Electronic camera

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an electronic camera which photographs an object and records image data. In particular, the present invention relates to a technology for recording image data in a good shooting condition without hand shaking or the like.

[0003] 2. Description of the Related Art

[0004] Generally, when performing hand-held camera shooting, hand shaking often occurs. When this kind of hand shaking occurs, since an object field is exposed in a blurry condition, an entirely blurry image is shot.

[0005] In a blurry image like this, the details of the entire image and the edge portions, which should be shot clearly, are lost. Therefore, the image does not give a good impression.

[0006] A conventional camera with a hand shaking correction mechanism for solving these disadvantages due to hand shaking is well known.

[0007]FIG. 13 shows a camera with this kind of hand shaking correction mechanism.

[0008] In FIG. 13, a shooting lens <b>92</b> is disposed on the front face of the camera <b>91</b>. A blur correction optical system <b>93</b> is rotatably arranged in the lens barrel of the shooting lens <b>92</b>.

[0009] The rotation of two-axis coreless motors <b>94</b> and <b>95</b> is transmitted to this blur correction optical system <b>93</b>, causing it to vibrate vertically and horizontally.

[0010] Meanwhile, a blur amount detecting sensor <b>96</b> which detects the blur amount in the horizontal direction and a blur amount detecting sensor <b>97</b> which detects the blur amount in the vertical direction are arranged in the camera <b>91</b>.

[0011] In the camera <b>91</b> which has this kind of structure, vibration of the camera body is detected by using the blur amount detecting sensors <b>96</b> and <b>97</b>. The camera <b>91</b> drives the coreless motors <b>94</b> and <b>95</b> in the reverse direction of the detected vibration, and vibrates the optical axis of the blur correction optical system <b>93</b>. As a result, the vibration of the shooting optical axis is diminished, and a good photograph in which the hand shaking is corrected can be shot.

[0012] However, in this kind of conventional example, the blur correction optical system <b>93</b> is disposed in the shooting lens <b>92</b>. Therefore, there is a problem in that the shooting lens <b>92</b> becomes large and heavy.

[0013] Moreover, the space to arrange the blur correction optical system <b>93</b> has to be kept in the shooting lens <b>92</b>, and there is a problem in that the flexibility of design of the shooting lens <b>92</b> decreases.

[0014] Furthermore, the inner reflection in the shooting lens <b>92</b> increases for the portion where the blur correction optical system <b>93</b> is provided. Therefore, flaring easily occurs when performing back-lit shooting or the like.

[0015] Moreover, since electric power is consumed when driving the blur correction optical system <b>93</b>, there is a problem in that the battery life becomes shorter.

[0016] Furthermore, there is a problem in that a small amount of noise occurs when driving the blur correction optical system <b>93</b>.

[0017] On the other hand, a blurred image can occur due not only to the aforementioned hand shaking, but also due to object shifting and misfocusing. However, since the conventional hand shaking correction mechanism only diminishes the vibration of the camera, there is a problem in that the mechanism cannot prevent object shifting and misfocusing at all.

[0018] In particular, along with the trend toward higher resolution and miniaturization of imaging elements in recent years, the light receiving area per one pixel is more and more reduced, and the effective sensitivity of the imaging element has become low. Because of this, there is a tendency that the exposure time of the shooting element generally increases, and the chances of occurrence of hand shaking and object shifting become even higher. Because of this, especially in an electronic camera, immediate countermeasures are desired with respect to hand shaking and object shifting.

[0019] Moreover, it was very difficult to accurately prevent misfocus accurately with conventional AF (automatic focus) shooting for an object which shows unpredictable movements, such as a flower which is swaying in the wind. Because of this, an electronic camera which can accurately resolve the misfocus accurately under this adverse conditions is strongly desired.

SUMMARY OF THE INVENTION

[0020] The present invention, in order to solve the aforementioned problems, has a purpose of providing an electronic camera which can reliably obtain image data in a good shooting condition, an electronic camera which can achieve minimum electric power consumption, an electronic camera which can decrease the worst value of release time lag by approximately one half, an electronic camera with a simplified structure, and an electronic camera which can decrease the memory capacity of the temporary storing means (later mentioned) or can increase the number of the samplings of image data.

[0021] Moreover, another purpose of the invention is to provide an electronic camera which can omit the temporary storing means (later mentioned), an electronic camera which can obtain good image data with little hand shaking, an electronic camera which can obtain good image data which has little object shifting or misfocus, an electronic camera which can effectively perform analysis of a spatial frequency component, and an electronic camera which can obtain good image data with little release time lag.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a principal block diagram which explains the invention.

[0023]FIG. 2 is a principal block diagram which explains another aspect of the invention.

[0024]FIG. 3 is a block diagram which shows the first embodiment.

[0025]FIG. 4 is a flowchart which explains the operation of the first embodiment.

[0026]FIG. 5 is a figure which shows the time change of the blur amount.

[0027]FIG. 6 is a block diagram which shows the second embodiment.

[0028]FIG. 7 is a flowchart which explains the operation of the second embodiment.

[0029]FIG. 8 is a block diagram which shows the third embodiment.

[0030]FIG. 9 is a flowchart which explains operation of the third embodiment.

[0031]FIG. 10 is a block diagram which shows the fourth embodiment.

[0032]FIG. 11 is a flowchart which explains the operation of the fourth embodiment.

[0033]FIG. 12 is a flowchart which explains the operation of the fifth embodiment.

[0034]FIG. 13 is a diagram which shows a conventional example of a camera with a hand shaking correction mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035]FIG. 1 is a schematic block diagram that explains the invention.

[0036] The invention comprises an image pick-up means <b>1</b> which continuously images an object, a temporary memory means <b>2</b> which temporarily stores a plurality of image data that are continuously imaged by the image pick-up means <b>1</b>, a shooting evaluation means <b>3</b> which evaluates whether the shooting condition of the image data which is imaged by the image pick-up means <b>1</b> is good or bad, a still image selection means <b>4</b> which selects image data with the highest evaluation by the shooting evaluation means <b>3</b>, and an image saving means <b>5</b> which saves the image data which is selected by the still image selection means <b>4</b>.

[0037] In the electronic camera, the temporarily memory means <b>2</b> starts the temporary storing of the image data after the release operation of the electronic camera is performed.

[0038] Moreover, while waiting for the release operation, the temporary memory means <b>2</b> successively takes in new image data from the image pick-up means <b>1</b> and successively updates the image data that is being temporarily stored, and after the release operation of the electronic camera, suspends the data updating when the image data spanning from before to after the release operation has been temporarily stored.

[0039] The temporary memory means <b>2</b> and the image saving means <b>5</b> share the same memory mechanism.

[0040] The temporary memory means <b>2</b> performs differential compression and stores a plurality of image data that is continuously imaged by the image pick-up means <b>1</b>.

[0041]FIG. 2 is a schematic block diagram to explain another aspect of the invention.

[0042] Another aspect of the invention comprises the image pick-up means, that continuously images an object, a memory medium <b>10</b> which can store the image data, a shooting evaluation means <b>3</b> that evaluates whether the shooting condition of the individual image data imaged by the image pick-up means <b>1</b> is good or bad, a comparison means <b>11</b> which compares the evaluation of the shooting evaluation means <b>3</b> concerning the image data in the memory medium <b>10</b> and the evaluation of the shooting evaluation means <b>3</b> concerning new image data from the image pick-up means <b>1</b>, and an image overwriting means <b>12</b> which overwrites and records the new image data to the memory medium <b>10</b> when the evaluation of the new image data by the comparison of the comparison means <b>11</b> is high.

[0043] This shooting evaluation means <b>3</b> is a means for detecting the blur amount of the image pick-up means <b>1</b> as at least one of a good shooting condition or a bad shooting condition.

[0044] In particular, the shooting evaluation means <b>3</b> evaluates the spatial frequency component of the image data as at least one of a good shooting condition and a bad shooting condition.

[0045] Furthermore, the shooting evaluation means <b>3</b> evaluates the high area component amount of the spatial frequency based on the compression encoding amount of the image data.

[0046] The shooting evaluation means <b>3</b> evaluates the release time lag which is the time shift between the release operation of the electronic camera and the point of imaging the image data.

[0047] [Explanation of the Operation of FIG. 1]

[0048] In the electronic camera of FIG. 1, the image pick-up means <b>1</b> continuously images an object. A plurality of image data that are shot in the same manner are temporarily stored in the temporary memory means <b>2</b>.

[0049] Meanwhile, the shooting evaluation means <b>3</b> evaluates whether the shooting condition of the individual image data is good or bad. The still image selection means <b>4</b> selects the image data which is imaged during the period when the evaluation of the shooting condition is highest among the image data that are stored in the temporary memory means <b>2</b>. The image saving means <b>5</b> saves the selected image data.

[0050] According to the aforementioned operation, the electronic camera can selectively obtain image data of a good shooting condition.

[0051] Moreover, in particular, in this electronic camera, the temporary memory means <b>2</b> temporarily stores the image data during the shooting period. Accordingly, since it is sufficient to perform the selecting processing of the image data after the shooting is completed, the processing operation during the shooting period can be decreased without any trouble.

[0052] In the electronic camera, the temporary memory means <b>2</b> starts the temporary storing of the image data after the release operation of the electronic camera.

[0053] Accordingly, image data of a good shooting condition can be selected from among the image data that is imaged after the release operation.

[0054] With this kind of operation, the operation may start after the release operation, and it is not necessary to always perform the imaging operation. Accordingly, it is possible to minimize electric power consumption of the electronic camera.

[0055] In the electronic camera, the temporary memory means <b>2</b> takes the new image data from the image pick-up means <b>1</b> successively while waiting for the release operation.

[0056] The temporary memory means <b>2</b> updates the image data by using this new image data, and maintains a plurality of image data that are temporarily stored in the nearest condition.

[0057] When the electronic camera is release-operated in this condition, the temporary memory means <b>2</b> suspends the data updating when the image data spanning from before to after the release operation has been temporarily stored.

[0058] Through this operation, the sampling zone (interval) of the image data which remains in the temporary memory means <b>2</b> is the zone which spans from before to after the release operation.

[0059] In particular, hand shaking that accompanies the release operation hardly ever occurs right before the release operation. Because of this, the possibility of selecting image data which has fewer hand shakings becomes very high by adding the period of right before the release operation to the sample zone.

[0060] In addition, since the sample zone of the image data spans from before to after the release operation, the worst value of the release time lag (corresponding to the time interval between the edge point of the sample zone and the release operation point) decreases by approximately half compared to when a sample zone of the same time length is arranged only after the release operation.

[0061] In the electronic camera, the temporary memory means <b>2</b> and the image saving means <b>5</b> share the same memory mechanism. Accordingly, the structure of the electronic camera is simplified.

[0062] In the electronic camera, the temporary memory means <b>2</b> performs differential compression to the image data which is continuously imaged by the image pick-up means <b>1</b> and stores the image data. The differential compression is compression by obtaining differential data between images and, for example, includes the techniques of simple differential compression between frames, movement guarantee prediction or the like. Normally, image data which is continuously imaged by the image pick-up means <b>1</b> has a very high correlation, even though it is not as high as the frame correlation of an animated image. Accordingly, it is possible to make the encoding amount of the image data smaller by performing the above mentioned differential compression.

[0063] Accordingly, it is possible to increase the sample number of the image data which can be stored in the temporary memory means <b>2</b>. The possibility of selecting image data which has a better shooting condition becomes high by thus increasing the sample number of the image data.

[0064] Moreover, if the sample number of image data is not increased, it is possible to decrease the memory capacity of the temporary memory means <b>2</b>.

[0065] [Explanation of the Operation of FIG. 2]

[0066] In the electronic camera of FIG. 2, the image pick-up means <b>1</b> continuously images an object. At this time, the shooting evaluation means <b>3</b> evaluates whether the shooting condition is good or bad. The comparing means <b>11</b> compares the evaluation concerning image data in the memory medium <b>10</b> and the new evaluation concerning new image data from the image pick-up means <b>1</b>.

[0067] Here, when the new evaluation is higher, the image overwriting means <b>12</b> overwrites and records the new image data to the memory medium <b>10</b>. As a result, the image data of the better shooting condition remains in the memory medium <b>10</b>.

[0068] In particular, in this electronic camera, it is not necessary to temporarily store the entire series of image data, and a large capacity of temporary memory means becomes unnecessary.

[0069] The electronic camera detects the blur amount (vibration amount or angular speed) of the image pick-up means <b>1</b> for the good or bad evaluation of the shooting condition. It can be evaluated that the hand shaking is small and the shooting condition is good when the blur amount of the image pick-up means <b>1</b> is small.

[0070] Accordingly, it is possible to image the image data with less hand shaking by performing the good or bad evaluation of the shooting condition by using the blur amount of the image pick-up means <b>1</b> as the measurement.

[0071] The electronic camera uses the spatial frequency component of the image data as the measurement of the good or bad evaluation of the shooting condition. Normally, for image data that are continuously imaged the image itself does not change much and it is assumed that the distribution of the spatial frequency has virtually no change. However, when hand shaking, object shifting or misfocus occurs to these image data, the image data is flattened and spatial frequency components of the high area is lost.

[0072] Accordingly, it can be evaluated that image data which has many spatial frequency components of high area among these image data has less hand shaking, object shifting or misfocus as a whole, and that the shooting condition is better.

[0073] Accordingly, it is possible to accurately select the image data which has small hand shaking, object shifting and misfocus as a whole by performing the good or bad evaluation of the shooting condition by using the spatial frequency component of the image data as the measurement.

[0074] The electronic camera evaluates the spatial frequency component of the image data from the compressed encoding amount. Normally, it can be evaluated that when the compressed encoding amount is larger, the spatial frequency component of the high area is larger. Accordingly, image data among the image data that are continuously imaged which has a large compressed encoding amount has less hand shaking, object shifting, and misfocus as a whole, and it can be evaluated that the shooting condition is better. Moreover, the value of this kind of compressed encoding amount can be obtained from the result of prior image compression processing, and it is not necessary to add special processing.

[0075] The electronic camera detects the release time lag as at least one of a good evaluation and a bad evaluation of the shooting condition. When this release time lag is smaller, it is closer to the shutter timing which the user desires, and it can be evaluated that the shooting condition is better. Accordingly, it is possible to select image data which has a smaller release time lag by making the release time lag as one item of the good or bad evaluation.

[0076] Moreover, in particular, the case is explained in which image data which has smaller release time lag is selected in a condition of performing the temporary storing of the imaged image from before the release operation. In this case, it is possible that the camera is in the middle of an exposure operation at the moment of the release operation. Accordingly, it is possible to obtain an image which has completely zero release time lag, which could not be obtained with conventional single shooting of an electronic camera, by automatic image selection.

[0077] Moreover, in the above description, the good or bad evaluation is performed by only one evaluation item for convenience. However, the present invention is not limited to this.

[0078] The good or bad evaluation can be performed by providing a priority order in the plurality of evaluation items, or by performing a total evaluation by weighting the evaluation items. At this time, needless to say, it is acceptable when evaluation items other than those in claims 7-10 are included.

[0079] Moreover, the electronic camera of the above-mentioned FIGS. 1 and 2 is not narrowly limited to a single structure electronic camera. There is a trend in recent electronic cameras to structure them as a plurality of mechanical systems, such as by having separate structures for the shooting unit and the information mechanism. (Computer, electronic notebook or the like). In this kind of system structure, it is possible to divide the operations of the present invention appropriately between a plurality of machines.

[0080] For example, it is possible to divide the operations, such as (1) in the imaging unit side, the continuously shot image data is temporarily stored and (2) in the information mechanism side, the images are selected and saved from among the series of image data according to the good or bad evaluation of the shooting condition.

[0081] Moreover, the operation of the information mechanism in this case can be realized by using a program (recorded on a machine readable recording medium) which makes the information mechanism execute “a step of obtaining a result of a good or bad evaluation from the image pick-up unit or performing a good or bad evaluation of the shooting condition from the spatial frequency component of the image data or the like” and “a step of selecting and saving image data according to the result of the good or bad evaluation”.

[0082] [Embodiments]

[0083] Hereafter, the embodiments of the present invention are explained based on the drawings.

[0084] (First Embodiment)

[0085]FIG. 3 is a block diagram which shows the first embodiment. Moreover, the first embodiment corresponds to the invention of claims 1, 2, 4, 5 and 7.

[0086] In FIG. 3, a shooting lens <b>22</b> is provided at the front face of the electronic camera <b>21</b>. The light receiving face of an image pick-up element <b>23</b> is arranged on the image space side of the shooting lens <b>22</b>.

[0087] The image output of this image pick-up element <b>23</b> is directly stored in the image memory <b>25</b> via an image processor <b>24</b> which performs color signal processing, A/D conversion, γ correction, image compression and the like. Other than this, in the image memory <b>25</b>, reading and writing of the data are performed via the data bus of the microprocessor <b>26</b>.

[0088] Moreover, blur amount detecting sensors <b>29</b><i>a </i>and <b>29</b><i>b </i>that are made of an angular speed sensor such as a piezoelectric gyro are arranged within the case of the electronic camera <b>21</b>. The blur amount detecting sensor <b>29</b><i>a </i>detects the blur amount in the vertical direction (pitching). The other blur amount detecting sensor <b>29</b><i>b </i>detects the blur amount in the horizontal direction (yawing). Output terminals of these blur amount detecting sensors <b>29</b><i>a </i>and <b>29</b><i>b </i>are respectively connected to the A/D input terminal of the microprocessor <b>26</b>.

[0089] Moreover, on the top face of the case of the electronic camera <b>21</b>, a release button <b>30</b> is arranged. The switch output of the release button <b>30</b> is connected to the microprocessor <b>26</b>.

[0090] Moreover, an electronic shutter control signal from the microprocessor <b>26</b> is given to the CCD driving circuit <b>31</b>. The CCD driving circuit <b>31</b> forms a driving pulse corresponding to this control signal, and gives it to the image pick-up element <b>23</b>. In addition, a timer <b>32</b> and an infrared ray transmission interface <b>33</b> are connected to the microprocessor <b>26</b>.

[0091] Moreover, the corresponding relationships of the present invention and the first embodiment are as follows. Image pick-up means <b>1</b> corresponds to the image pick-up element <b>23</b> and the CCD driving circuit <b>31</b>. The temporary memory means <b>2</b> corresponds to the image memory <b>25</b> and “a function which differentially compresses and temporarily stores image data” of the image processor <b>24</b>. The shooting evaluation means <b>3</b> corresponds to the blur amount detecting sensors <b>29</b><i>a </i>and <b>29</b><i>b. </i>The still image selection means <b>4</b> corresponds to “a function which selects image data based on the blur amount” of the microprocessor <b>26</b>. The image saving means <b>5</b> corresponds to the image memory <b>25</b> and “a function which saves the selected image data” of the microprocessor <b>26</b>.

[0092] Next, the operation of the first embodiment is explained.

[0093]FIG. 4 is a flowchart to explain the operation of the first embodiment.

[0094] First of all, when the main power of the electronic camera <b>21</b> is turned on, the microprocessor <b>26</b> waits until the release button <b>30</b> is pressed (NO side of S<b>1</b> of FIG. 4).

[0095] Here, when the release button <b>30</b> is pressed (YES side of S<b>1</b> of FIG. 4), the microprocessor <b>26</b> activates the CCD driving circuit <b>31</b>, and temporarily discharges the unnecessary charge on the image pick-up element <b>23</b>. After discharging the unnecessary charge, a signal charge is newly accumulated on the image pick-up element <b>23</b> corresponding to the brightness of an object which is projected to the light receiving face (S<b>2</b> of FIG. 4).

[0096] During the accumulating period of this kind of signal charge, the microprocessor <b>26</b> takes in a blur amount W1 in the vertical direction from the blur amount detecting sensor <b>29</b><i>a. </i>A blur amount W2 in the horizontal direction is obtained from the other blur amount detecting sensor <b>29</b><i>b. </i>The microprocessor <b>26</b> calculates the sum of the squares or the sum of the absolute values of the blur amounts W1 and W2, and takes this value as the blur amount W of the entire electronic camera <b>21</b> (S<b>3</b> of FIG. 4).

[0097] When a predetermined accumulation time passes, the microprocessor <b>26</b> reads out the image data from the image pick-up element <b>23</b> via the CCD driving circuit <b>31</b> (S<b>4</b> of FIG. 4).

[0098] The image processor <b>24</b> records this image data in a temporary memory area of the image memory <b>25</b> after performing A/D conversion, γ correction, image compression and the like. Moreover, for the image compression here, differential compression is adopted which is the same as in MPEG or the like. Moreover, at this time, the microprocessor <b>26</b> records the blur amount W relating to the image data (S<b>5</b> of FIG. 4).

[0099] The above mentioned series of operations S<b>2</b>-S<b>5</b> are repeatedly executed until a limited time of 0.3 seconds elapses from the release operation (YES side of S<b>6</b> of FIG. 4).

[0100] Through the operation until this point, image data of a plurality frames that are imaged during the 0.3 seconds from the release operation are recorded in the image memory <b>25</b> along with the blur amount W during the shooting period.

[0101] The microprocessor <b>26</b> searches for the smallest value among the blur amounts W, and finds image data A which was imaged during the period for which the smallest blur amount W is detected (S<b>7</b> of FIG. 4).

[0102]FIG. 5 is a diagram which shows the condition of the time change and overall blur amount W. According to FIG. 5, it can be expected that the blur amount W becomes smallest approximately once for every 0.3 seconds. Accordingly, the image data A which is selected as described above has sufficiently small hand shaking and it is predicted that it is good image data.

[0103] The microprocessor <b>26</b> records this image data A in the saving area of the image memory <b>25</b> (S<b>8</b> of FIG. 4). Moreover, it is acceptable to finish the processing of the image data A by performing a change of the management area, the image memory <b>25</b> and the file attributes without actually shifting the image data A in the image memory <b>25</b>. Moreover, when the image data A is differentially compressed, it may be newly JPEG compressed after being image decompressed.

[0104] By the operation explained above, in the first embodiment, the image data which has the smallest blur amount W among the image data that are continuously imaged is selected. Accordingly, it is possible to obtain image data which has small hand shaking without using a conventional hand shaking correction mechanism at all.

[0105] Moreover, since it is not necessary to arrange an optical system for the hand shaking correction in the shooting lens <b>22</b>, a compact lightweight shooting lens <b>22</b> can be easily obtained.

[0106] In addition, because there is no need to maintain space in order to arrange the optical system for hand shaking correction in the shooting lens <b>22</b>, the degree of design freedom of the shooting lens <b>22</b> becomes higher. Because of this, it has become possible to improve the operationability of the shooting lens <b>22</b> without having any problems.

[0107] Moreover, since the inner reflection by the optical system for the hand shaking correction is resolved, flaring at the time of performing backlight shooting is decreased.

[0108] In addition, since there is no need to have a driving mechanism for the hand shaking correction, it is possible to extend the battery life to conserve the electric power consumption. Moreover, the disadvantages of occurrence of noise or vibration from the driving mechanism for the hand shaking correction are resolved.

[0109] Moreover, since the image memory <b>25</b> is jointly used for both the temporary storing and saving of the image data, there is no need to provide the image memory separately, and the structure of the electronic camera <b>21</b> can be simplified.

[0110] Moreover, in the above mentioned embodiment, the memory area of the image memory <b>25</b> is fixedly divided into the temporary memory area and the saving area, but the present invention is not limited to this. For example, it is acceptable to movably divide the temporary memory area of the image memory <b>25</b>. With this kind of structure, it becomes possible to save the image data by using the entire memory area of the image memory <b>25</b> by dividing the temporary memory area into the saving area gradually.

[0111] Next, another embodiment is explained.

[0112] (Second Embodiment)

[0113]FIG. 6 is a block diagram which shows the second embodiment. Moreover, the second embodiment corresponds to the invention that is described in claims 1, 3, 7 and 10.

[0114] In FIG. 6, a shooting lens <b>42</b> is provided on a front face of the electronic camera <b>41</b>. The light receiving face of an image pick-up element <b>43</b> is arranged on the image space side of the shooting lens <b>42</b>.

[0115] The image output from the image pick-up element <b>43</b> is connected to the data input of the image memory <b>45</b> via the image processor <b>44</b> which performs color signal processing, A/D conversion, γ correction and the like. Meanwhile, the data output of the image memory <b>45</b> is connected to the data input of the microprocessor <b>46</b>.

[0116] A memory card <b>48</b> is detachably connected to the data output terminal of the microprocessor <b>46</b> via the image recording part <b>47</b>.

[0117] Meanwhile, blur amount detecting sensors <b>49</b><i>a </i>and <b>49</b><i>b </i>that are composed of an angular speed sensor such as a piezoelectric gyro are arranged within the case of the electronic camera <b>41</b>. The outputs of these blur amount detecting sensors <b>49</b><i>a </i>and <b>49</b><i>b </i>are respectively connected to A/D input terminals of the microprocessor <b>46</b>.

[0118] Furthermore, a release button <b>50</b> is arranged on the top face of the case of the electronic camera <b>41</b>, and the switch output of the release button <b>50</b> is connected to the microprocessor <b>46</b>.

[0119] An electronic shutter control signal from the microprocessor <b>46</b> is given to the CCD driving circuit <b>51</b>. The CCD driving circuit <b>51</b> generates a driving pulse in response to this control signal, and forwards it to the image pick-up element <b>43</b>. Other than this, a timer <b>52</b> is connected to the microprocessor <b>46</b>.

[0120] The corresponding relationships of the present invention and second embodiment are as follows. The imaging means <b>1</b> corresponds to the image pick-up element <b>43</b> and the CCD driving circuit <b>51</b>, the temporary memory means <b>2</b> corresponds to the image memory <b>45</b> and “a function that temporarily stores the image data spanning from before to after the release operation” of the image processor <b>44</b>, the shooting evaluation means <b>3</b> corresponds to the blur amount detecting sensors <b>49</b><i>a </i>and <b>49</b><i>b </i>and “a function which measures the release time lag” of the timer <b>52</b> and the microprocessor <b>46</b>, the still image selection means <b>4</b> corresponds to “a function which selects the image data based on an evaluation value” of the microprocessor <b>46</b>, and the image saving means <b>5</b> corresponds to the image recording part <b>47</b> and the memory card <b>48</b>.

[0121] Next, the operation of the second embodiment is explained.

[0122]FIG. 7 is a flowchart which explains the operation of the second embodiment.

[0123] First of all, when the main power of the electronic camera <b>41</b> is turned on, the microprocessor <b>46</b> discharges unnecessary charges in the image pick-up element <b>43</b> via the CCD driving circuit <b>51</b>. After thus discharging unnecessary charges, signal charges are accumulated in the image pick-up element <b>43</b> according to the brightness of the object which is projected on the light receiving face (S<b>11</b> of FIG. 7).

[0124] During the accumulation period of the signal charge, the microprocessor <b>46</b> obtains the blur amount W1 in the vertical direction from the blur amount detecting sensor <b>49</b><i>a</i>. The blur amount W2 in the horizontal direction is obtained from the other blur amount detecting sensor <b>49</b><i>b. </i>The microprocessor <b>46</b> calculates the sum of the square values, the sum of the absolute values or the like for these blur amounts W1 and W2, and takes this as the overall blur amount of the electronic camera <b>41</b> (S<b>12</b> of FIG. 7).

[0125] Next, the microprocessor <b>46</b> obtains the current time as the shooting time Te from the timer <b>52</b> (S<b>13</b> of FIG. 7).

[0126] In this condition, when a predetermined accumulation time has passed, the microprocessor <b>46</b> reads out the image data from the image pick-up element <b>43</b> via the CCD driving circuit <b>51</b> (S<b>14</b> of FIG. 7).

[0127] The image processor <b>44</b> temporarily stores this image data in the image memory <b>45</b> after performing A/D conversion, γ correction, and the like (S<b>15</b> of FIG. 7). At this time, the microprocessor <b>46</b> stores the blur amount W and the shooting time Te in correlation with the image data (S<b>17</b> of FIG. 7).

[0128] When the image data and the image memory <b>45</b> have already reached up to seven frames (S<b>16</b> of FIG. 7), the newest data is written and recorded in place of the oldest data in the image memory <b>45</b> (S<b>18</b> of FIG. 7).

[0129] Here, the microprocessor <b>46</b> evaluates whether the release button <b>50</b> is pressed (S<b>19</b> of FIG. 7).

[0130] When the release button <b>50</b> is pressed (YES side of S<b>19</b> of FIG. 7), the microprocessor <b>46</b> obtains the current time from the timer <b>52</b>, and stores it as the time Tr of the release operation (S<b>20</b> of FIG. 7).

[0131] The above-mentioned operations S<b>1</b>-<b>20</b> are repeatedly executed until four frames of the image data after the release operation have been recorded (NO side of S<b>21</b> of FIG. 7).

[0132] On the other hand, when four frames of the image data have been recorded after the release operation (YES side of S<b>21</b> of FIG. 7), the microprocessor <b>46</b> executes the selection of the image data by the following procedure after suspending the imaging operation.

[0133] First of all, the microprocessor <b>46</b> calculates the evaluation value E by using the equation (1) for each image data in the image memory <b>45</b> (S<b>22</b> of FIG. 7).

Evaluation value <i>E=α·|Te−Tr|+β·|W|</i>  (1)

[0134] Here, the first item of the right side is an item relating to the release time lag, and the second item is an item relating to the blur amount W. Additionally, the coefficients α and β are to perform the weighting of these two items (for example, they are set as α=1, β=1 or the like).

[0135] The microprocessor <b>46</b> searches for the smallest value among individual evaluation values E, and finds the image data A which is related to the smallest evaluation value E (S<b>23</b> of FIG. 7).

[0136] The microprocessor <b>46</b> reads out this image data A from the image memory <b>45</b> and image compresses the data. The microprocessor <b>46</b> saves the image-compressed image data A onto the memory card <b>48</b> via the image recording part <b>47</b> (S<b>24</b> of FIG. 7). For the processing of the image compression, it is acceptable to complete it at steps S<b>17</b> and S<b>18</b> in FIG. 7 instead of performing it at this point.

[0137] Next, the microprocessor <b>46</b> returns the operation to step S<b>11</b> after initializing the image memory <b>45</b> and the control data (S<b>25</b> of FIG. 7).

[0138] According to the series of operations that are explained above, in the second embodiment, the image data in which the evaluation value E is the smallest is selected among the continuously imaged image data. Accordingly, it is possible to obtain the image data in which the hand shaking is smallest and in which the release time lag is smallest by taking the evaluation value E as the standard.

[0139] Additionally, since the selection of the image data is performed from among image data spanning from before to after the release operation, more adequate image data can be selected without being limited to the data obtained after performing the release operation.

[0140] In the above-mentioned second embodiment, the temporary storing of the image data is started by turning on the main power, but the present invention is not limited to this. For example, it is acceptable for the microprocessor <b>46</b> to detect the half-pressed state of the release button <b>50</b> and to start the temporary storing of the image data from the half-pressed point. In this kind of structure, because it is not necessary to always perform the temporary storing of the image data, it is possible to conserve electric power of the electric camera.

[0141] Next, another embodiment is explained.

[0142] (The Third Embodiment)

[0143]FIG. 8 is a block diagram showing the third embodiment.

[0144] In FIG. 8, a shooting lens <b>62</b> is fixed at a front surface of the electronic camera <b>61</b>. The light-receiving face of an image pick-up element <b>63</b> is disposed on the image space side of the shooting lens <b>62</b>.

[0145] The image output of the image pick-up element <b>63</b> is given to a microprocessor <b>65</b> through an image processor <b>64</b>, which performs color signal processing, A/D conversion, γ correction, and the like. Furthermore, an image memory <b>66</b> is connected to the data bus of the microprocessor <b>65</b>.

[0146] Additionally, a memory card <b>68</b> is detachably connected to the data output terminal of the microprocessor <b>65</b> through an image recorder <b>67</b>.

[0147] Furthermore, the blur amount detection sensors <b>69</b><i>a </i>and <b>69</b><i>b </i>comprising an angular speed sensor such as a piezoelectric gyro are disposed inside of the case of the electronic camera <b>61</b>. The outputs of the blur amount detection sensors <b>69</b><i>a </i>and <b>69</b><i>b </i>are respectively connected to A/D input terminals of the microprocessor <b>65</b>.

[0148] In addition, a release button <b>70</b> is disposed on the top of the case of the electronic camera <b>61</b>, and the switch output of the release button <b>70</b> is connected to the microprocessor <b>65</b>.

[0149] Additionally, an electronic shutter control signal from the microprocessor <b>65</b> is given to a CCD driving circuit <b>71</b>. The CCD driving circuit <b>71</b> forms a driving pulse in response to the control signal and gives it to the image pick-up element <b>63</b>.

[0150] Furthermore, with respect to the corresponding relationships between the invention as set forth in claims 6 and 7 and the third embodiment, the image pick-up means <b>1</b> corresponds to the image pick-up element <b>63</b> and the CCD driving circuit <b>71</b>, the shooting evaluation means <b>3</b> corresponds to the blur amount detection sensors <b>69</b><i>a </i>and <b>69</b><i>b, </i>the recording medium <b>10</b> corresponds to the image memory <b>66</b>, the comparison means <b>11</b> corresponds to a “function to perform comparison between old and new blur amount” of the microprocessor <b>65</b>, and the image overwriting means <b>12</b> corresponds to a “function to overwrite the image data to the image memory <b>66</b>” of the microprocessor <b>65</b>.

[0151] The following explains the operation of the third embodiment.

[0152]FIG. 9 is a flow chart explaining the operation of the third embodiment.

[0153] First, when the main power is turned on to the electronic camera <b>61</b>, the microprocessor <b>65</b> determines the maximum allowable value of the blur amount, based upon the current shutter speed and focal distance (FIG. 9 S<b>31</b>).

[0154] Next, the microprocessor <b>65</b> initially sets the maximum allowable value which was thus determined at the minimum blur amount W_min(FIG. 9 S<b>32</b>).

[0155] The microprocessor <b>65</b> returns to step S<b>31</b> until the release button <b>70</b> is pressed, and the above operation is regularly repeated (NO side of FIG. 9 S<b>33</b>).

[0156] Meanwhile, when the release button <b>70</b> is pressed (YES side of FIG. 9 S<b>33</b>), the microprocessor <b>65</b> repeatedly performs steps S<b>35</b>-<b>40</b> as follows from the time of the release operation until 0.5 second has elapsed (FIG. 9 S<b>34</b>).

[0157] First, the microprocessor <b>65</b> temporarily discharges unnecessary charges from the image pick-up element <b>63</b> via the CCD driving circuit <b>71</b>. After thus discharging unnecessary charges, the signal charge is accumulated in response to the brightness of the object image which is projected onto the light-receiving face in the image pick-up element <b>63</b> (FIG. 9 S<b>35</b>).

[0158] During the accumulation period of the signal charge, the microprocessor <b>65</b> obtains the blur amount W1 in the up-and-down direction from the blur amount detection sensor <b>69</b><i>a. </i>The blur amount W2 in the right-and-left direction is obtained from the other blur amount detection sensor <b>69</b><i>b. </i>The microprocessor <b>65</b> calculates the sum of the square values or the sum of the absolute values of the blur amounts W1 and W2, and this is defined as the overall blur amount W of the electronic camera <b>61</b> (FIG. 9 S<b>36</b>).

[0159] Here, the microprocessor <b>65</b> compares the size of the minimum blur amount W_minand the blur amount W.

[0160] As a result of this type of comparison, when the blur amount W is larger (NO side of FIG. 9 S<b>37</b>), the microprocessor <b>65</b> does not read the image data from the image pick-up element <b>63</b> and returns the operation to step S<b>34</b>.

[0161] Furthermore, at the time of this determination, since the microprocessor <b>65</b> discharges unnecessary charge from the image pick-up element <b>63</b>, it is acceptable to begin the following frame of the charge accumulation as soon as possible. By this type of operation, it is possible to increase the number of shooting frames per unit time by minimizing the waste of accumulation time.

[0162] Meanwhile, when the blur amount W is smaller (YES side of FIG. 9 S<b>37</b>) the microprocessor <b>65</b> reads the image data from the image pick-up element <b>63</b> after a predetermined accumulation time elapses (FIG. 9 S<b>38</b>).

[0163] The microprocessor <b>65</b> takes in the image data through the image processor <b>64</b> and is overwritten and recorded in the image memory <b>66</b> (step S<b>39</b>).

[0164] Along with this type of overwriting recording, after the microprocessor <b>65</b> sets the current blur amount W at the minimum blur amount W_min(step S<b>40</b>), the operation returns to step S<b>34</b>.

[0165] After the above-mentioned series of operations S<b>34</b>-<b>40</b> are repeatedly performed until the limit time 0.5 seconds has elapsed since the release operation, the microprocessor <b>65</b> moves the operation to step S<b>41</b>.

[0166] By the operation up to the present, the image data with the smallest blur amount W among the image data which is imaged in 0.5 seconds from the release operation is recorded in the image memory <b>66</b>.

[0167] In this type of case (YES side of FIG. 9 S<b>41</b>), after the microprocessor <b>65</b> image-compresses the residual image data within the image memory <b>66</b>, the data is saved on the memory card <b>68</b> through the image recorder <b>67</b> (FIG. 9 S<b>43</b>). In addition, with respect to the image compression processing, instead of performing the processing here, it is acceptable to have the processing performed in step S<b>39</b> shown in FIG. 9.

[0168] After saving of the image data is completed, the microprocessor <b>65</b> returns the operation to step S<b>31</b> after the image data within the image memory <b>66</b> is erased in preparation for the following shooting operation (FIG. 9 S<b>44</b>).

[0169] Furthermore, when the blur amount W does not fall under the largest allowable value of the blur amount even one time, the image data cannot be recorded in the image memory <b>66</b> at all. Thus, when no image data exists in the image memory <b>66</b> (NO side of FIG. 9 S<b>41</b>), the microprocessor <b>65</b> determines that blurring due to hand shaking was too much, so the operation returns to step S<b>31</b> after processing of the “warning of blurring due to hand shaking” is performed (FIG. 9 S<b>42</b>).

[0170] By the operation which was explained above, in the third embodiment, image data with much less blur amount is saved in the image memory <b>66</b>. Therefore, it is possible to obtain image data with less blurring due to hand shaking without using the conventional correction mechanism for blurring due to hand shaking.

[0171] Furthermore, the image data is successively overwritten and recorded in the image memory <b>66</b>, so the capacity to store at least one frame of image data is sufficient.

[0172] Additionally, in the third embodiment, image data with less blur amount is saved in the image memory <b>66</b> based upon the comparison of the blur amount, but the invention is not limited to this. It is also acceptable to select the image data which will be left in the image memory <b>66</b> based upon an evaluation value including the evaluation items or the like as set forth in claims 7-10.

[0173] Furthermore, in the third embodiment, when the blur amount W does not fall below the “largest allowable value of the blur amount”, the image data is not recorded at all, but the invention is not limited to this. For example, the first image data or the like can be temporarily recorded, and after that, the image data can be updated every time the blur amount W falls below the largest allowable value. In this type of structure, the image data with the smallest blur amount W is eventually recorded.

[0174] Additionally, in the first through third embodiments, based upon the blur amount or the evaluation value, only one frame of image data is saved, but the invention is not limited to this. For example, it is also acceptable to save a predetermined number of image data beginning from the highest ranking evaluated position based upon the blur amount or the evaluation value. In this type of structure, the operator can later select the image data with the best “shutter chance” among a specified number of image data.

[0175] The following explains another embodiment.

[0176] (Fourth Embodiment)

[0177]FIG. 10 is a block diagram showing the fourth embodiment.

[0178] In FIG. 10, a zoom lens <b>102</b> is fixed at the front of an electronic camera <b>101</b>. The light-receiving face of an image pick-up element <b>103</b> is disposed on the image space side of the zoom lens <b>102</b>.

[0179] The image output from the image pick-up element <b>103</b> is connected to an image compressor <b>106</b><i>a </i>via the image processor <b>104</b> which performs color signal processing, A/D conversion, γ correction and the like and the image memory <b>105</b>. The output of the image compressor <b>106</b><i>a </i>is connected to a microprocessor <b>106</b>.

[0180] Furthermore, a memory card <b>108</b> is detachably connected to the microprocessor <b>106</b> via an image recorder <b>107</b>.

[0181] Furthermore, a release button <b>110</b> and a shooting mode selection button <b>111</b> are disposed on the housing of the electronic camera <b>101</b>, and the switch outputs of these operation parts are connected to the microprocessor <b>106</b>.

[0182] Additionally, an electronic shutter control signal from the microprocessor <b>106</b> is given to the CCD driving circuit <b>112</b>. The CCD driving circuit <b>112</b> forms a driving pulse in response to the control signal and gives the driving pulse to the image pick-up element <b>103</b>.

[0183] Furthermore, a photometry part <b>113</b> to measure the object brightness, a range finding part <b>114</b> to measure the object distance, an encoder <b>115</b> to detect the focal distance from the lens position, and a flash part (so-called strobe) <b>116</b> are disposed on the electronic camera <b>101</b> and are respectively connected to the microprocessor <b>106</b>.

[0184] Furthermore, with respect to the corresponding relationships between the invention as set forth in claims 1, 2 and 8 and the fourth embodiment, the image pick-up means <b>1</b> corresponds to the image pick-up element <b>103</b>, the CCD driving circuit <b>112</b>, and the zoom lens <b>102</b>, the temporary memory means <b>2</b> corresponds to the image memory <b>105</b>, the shooting evaluation means <b>3</b> corresponds to a “function to convert the image data to a spatial frequency component” of the image compressor <b>106</b>a, the still image selection means <b>4</b> corresponds to a “function to select image data based upon the spatial frequency component” of the microprocessor <b>106</b>, and the image saving means <b>5</b> corresponds to the image recorder <b>107</b> and the memory card <b>108</b>.

[0185] The following explains the operation of the fourth embodiment.

[0186]FIG. 11 is a flow chart explaining the operation of the fourth embodiment.

[0187] First of all, when the main power is turned on to the electronic camera <b>101</b>, the microprocessor <b>106</b> waits until the release button <b>110</b> is pressed (NO side of FIG. 11 S<b>1</b>).

[0188] Here, when the release button <b>110</b> is pressed (YES side of FIG. 11 S<b>1</b>), the microprocessor <b>106</b> determines a current shooting mode (FIG. 11 S<b>2</b>).

[0189] If the current shooting mode is not any of the following cases (1)-(3), the microprocessor <b>106</b> returns the operation to step S<b>1</b> after an ordinary shooting (shooting that images and records one frame) is performed (FIG. 11 S<b>3</b>).

[0190] (1) Night view shooting mode—a mode which can cut the flash emitted light, adjust the focus at infinite, and expose for a long period of time.

[0191] (2) Macro mode—a mode which sets the focus of the lens at the macro area and performs close-up shooting.

[0192] (3) Sports mode—a mode which sets the exposure time as short as possible and shoots an object which moves at high speed.

[0193] Meanwhile, when the current shooting mode is any of these shooting modes, there is a particularly high possibility of blurring due to hand shaking, movement of the object, and/or misfocus, so the microprocessor <b>106</b> performs the countermeasure operations of step S<b>4</b> and after.

[0194] First of all, the microprocessor <b>106</b> instructs a plurality of sequential shootings (3 frames as an example here) to the CCD driving circuit <b>112</b>. The CCD driving circuit <b>112</b> consecutively reads three frames of image data from the image pick-up element <b>103</b>. The three frames of the image data are temporarily stored in the image memory <b>105</b> after color signal processing, γ correction, and the like is performed by the image processor <b>104</b> (FIG. 11 S<b>4</b>).

[0195] Next, the microprocessor <b>106</b> instructs DCT conversion (discrete cosine transformation) to the image compressor <b>106</b><i>a. </i>The image compressor <b>106</b><i>a </i>takes in a specified area of the screen (for example, the center of the screen) and performs DCT conversion with respect to three frames of image data within the image memory <b>105</b> (FIG. 11 S<b>5</b>).

[0196] The microprocessor <b>106</b> takes in the spatial frequency component after the DCT conversion and selects the image data including the highest spatial frequency component among the three frames (FIG. 11 S<b>6</b>).

[0197] Here, when there is only one piece of selected image data (NO side of FIG. 11 S<b>7</b>), the microprocessor <b>106</b> moves the operation to step S<b>11</b>.

[0198] Meanwhile, when a plurality of selected image data are available (YES side of FIG. 11 S<b>7</b>), the microprocessor <b>106</b> selects the spatial frequency component with the largest amplitude in the high area among the selected data (FIG. 11 S<b>8</b>).

[0199] Here, when there is one piece of selected image data (NO side of FIG. 11 S<b>9</b>), the microprocessor <b>106</b> moves the operation to step S<b>11</b>.

[0200] Meanwhile, when there are still a plurality of selected image data (YES side of FIG. 11, S<b>9</b>), the microprocessor <b>106</b> selects the first shot data among the selected image data (FIG. 11 S<b>10</b>).

[0201] After the image data is thus narrowed down to one, the microprocessor <b>106</b> image-compresses the image data via the image compressor <b>106</b><i>a, </i>and the image data is recorded to the memory card <b>108</b> (FIG. 11 S<b>1</b>).

[0202] By the operation which was explained above, in the fourth embodiment, the image data with the most ample spatial frequency component in the high area is selected among the image data which has been continuously imaged and is recorded. Therefore, it is possible to select image data in which blurring due to hand shaking, movement of the object, misfocus, or the like is appropriately small.

[0203] Furthermore, in the fourth embodiment, by using conversion such as DCT conversion, the spatial frequency component of the image data is accurately determined, but the present invention is not limited to this. For example, it is acceptable to easily determine the spatial frequency component by using a well-known spatial frequency filter (e.g., a high pass filter which takes the difference between the adjacent pixels), contrast detection, or the like.

[0204] The following explains another embodiment.

[0205] (Fifth Embodiment)

[0206] The fifth embodiment is an embodiment which corresponds to the present invention as set forth in claims 1, 2, 8, and 9. Additionally, the structure of the fifth embodiment is virtually the same as the fourth embodiment (FIG. 10), so the structural explanation is omitted here.

[0207]FIG. 12 is a flow chart explaining the operation of the fifth embodiment.

[0208] The following explains the operation of the fifth embodiment in accordance with FIG. 12.

[0209] First, when the main power is turned on to the electronic camera <b>101</b>, the microprocessor <b>106</b> waits until the release button <b>110</b> is pressed (NO side of FIG. 12, S<b>1</b>).

[0210] Here, when the release button <b>110</b> is pressed (YES side of FIG. 12 S<b>1</b>), the microprocessor <b>106</b> measures the object brightness through the photometry part <b>113</b> and determines the exposure time to obtain the appropriate exposure (FIG. 12 S<b>2</b>).

[0211] Next, the microprocessor <b>106</b> detects the focal distance of the zoom lens <b>102</b> through the encoder <b>115</b>. Furthermore, the microprocessor <b>106</b> detects the object distance through the range finding part <b>114</b> (FIG. 12 S<b>3</b>).

[0212] Here, the microprocessor <b>106</b> determines whether the current mode setting is the flash shooting mode (FIG. 12 S<b>4</b>). In the case of the flash shooting mode, the possibility of blurring due to hand shaking or movement of the object is lower, so the microprocessor <b>106</b> returns the operation to step S<b>1</b> after ordinary shooting (shooting to image and record one frame) is performed (FIG. 12 S<b>5</b>).

[0213] Meanwhile, when the current mode setting is other than the flash shooting mode, the microprocessor <b>106</b> performs the following condition determinations (1) and (2).

[0214] (1) Whether the exposure time is longer than a specified time τ.

[0215] (2) Whether the image magnification (approximately equal to focal distance/object distance) is larger than a specified magnification γ.

[0216] When neither of these conditions are established (NO side of FIG. 12 S<b>6</b>), the microprocessor <b>106</b> determines that there is little possibility of blurring due to hand shaking or movement of the object, and the operation is returned to step S<b>1</b> after the ordinary shooting is performed (FIG. 12 S<b>5</b>).

[0217] Meanwhile, when either of these conditions is established (YES side of FIG. 12 S<b>6</b>), the microprocessor <b>106</b> performs the countermeasure operation of step S<b>7</b> and after.

[0218] First, the microprocessor <b>106</b> instructs continuous shooting of a plurality of frames (3 frames as an example here) to the CCD driving circuit <b>112</b>. The CCD driving circuit <b>112</b> sequentially reads three frames of image data from the image pick-up element <b>103</b>. The three frames of image data are temporarily stored in the image memory <b>105</b> through the image processor <b>104</b> after color signal processing, γ correction, and the like is performed (FIG. 12 S<b>7</b>).

[0219] Next, the microprocessor <b>106</b> instructs image compression to the image compressor <b>106</b><i>a. </i>The image compressor <b>106</b><i>a </i>compresses one frame of image data for testing and determines an appropriate scale factor (a well-known parameter value to govern the condition of quantization in the image compression) in order to approach a desired compression encoding amount. The image compressor <b>106</b><i>a </i>uniformly uses the scale factor value and sequentially image-compresses three frames of image data (FIG. 12 S<b>8</b>). This method is generally known as fixed-length compression of JPEG.

[0220] Here, the microprocessor <b>106</b> compares the sizes of the encoding amounts after compression (compressed encoding amounts) of the three frames of image data and selects the image data with the largest compressed encoding amount (FIG. 12 S<b>9</b>).

[0221] Here, when there is one piece of selected image data (NO side of FIG. 12 S<b>10</b>), the microprocessor <b>106</b> moves the operation to step S<b>12</b>.

[0222] Meanwhile, when there are a plurality of selected image data (YES side of FIG. 12 S<b>10</b>), the microprocessor <b>106</b> selects the data which was first shot among the selected image data (FIG. 12 S<b>11</b>).

[0223] After the image data is thus narrowed down to one, the microprocessor <b>106</b> records the selected image data (already compressed) to the memory card <b>108</b> (FIG. 12 S<b>12</b>).

[0224] By the operation which was explained above, in the fifth embodiment, the image data with the largest compressed encoding amount is selected among the image data which has been continuously imaged and is recorded to the memory card <b>108</b>. Therefore, the image with generally little blurring due to hand shaking, movement of the object, and misfocus and with the most ample spatial frequency component in the high area can be recorded onto the memory card <b>108</b>.

[0225] Furthermore, in the fifth embodiment which was described above, when the image magnification is larger than the specified magnification γ, it is in a mode that selects a good image (an image in a good shooting state), but the invention is not limited to this. For example, it is acceptable to enter a mode which selects a good image when the focal distance is longer than the specified value.

[0226] Furthermore, in the fifth embodiment which was described above, three frames of image data are image-compressed over the entire screen, but the present invention is not limited to this. For example, it is also acceptable to extract only a specified area (for example, the center of the screen) on the screen from the three frames of image data, perform the image compression, and obtain the compressed encoding amount for evaluation. In this type of operation, the comparison of the spatial frequency component is performed limited to the specified area. Therefore, even if it is in a shooting condition where the background might be blurry such as zoom shooting or wide-angle shooting, it is possible to accurately select clear image data within the specified area. Furthermore, when the compressed encoding amount for evaluation is obtained, image compression for only the specified area is sufficient, so it is possible to significantly shorten the processing time to obtain the compressed encoding amount for evaluation.

[0227] In addition, in the fifth embodiment which was described above, after three frames of continuous shooting are all completed, three frames of image compression begins, but the present invention is not limited to this. For example, it is acceptable to increase the number of shooting per unit time by simultaneously performing the previous frame of image compression and the following frame of image pick-up operation. Particularly, in this type of operation, it is possible to simultaneously perform the image pick-up operation along with the old and new comparison of the compressed encoding amount, so it is possible to structure an electronic camera to overwrite and record better image data such as the present invention.

[0228] Furthermore, in the first through fifth embodiments which were described above, the case is explained in which one good image is saved, but it is possible to apply the present invention to a case in which a plurality of good images are saved. For example, in the case of exposure bracketing (a mode that shoots several times while changing the exposure condition), the operation to save one good image under the same exposure condition can be repeated while changing the exposure condition.

[0229] Furthermore, in the first through fifth embodiments which were described above, the display function of the electronic camera is not particularly explained, but it is possible to perform various displays related to the present invention. For example, a mode display such as “a mode to select an image in response to a good/bad evaluation of the shooting state” may be performed within the view finder, and/or on the monitor screen of the electronic camera, and/or the number of the current sample of image data and/or the number of remaining samples can be displayed by using pictures, characters, or the like. With this type of structure, it is possible to inform the photographer of the operation state of the electronic camera in detail.

[0230] In addition, the result of a good/bad evaluation of the shooting state (size of the blur amount or the like) can be displayed by using pictures, characters, or the like. At this time, along with the display of a good/bad evaluation, it is acceptable to display (for example, thumbnail display) the image data which is temporarily stored. With this type of structure, the photographer considers the image display and the display of a good/bad evaluation and can appropriately select desired image data.

[0231] Furthermore, when the good/bad evaluation in a shooting state is less than a threshold, a warning display (including a warning or the like) can be performed, and/or a display to inform that the good/bad evaluation is the maximum (including a warning or the like) can be performed. In this type of structure, the photographer is informed of the goodness or badness of the shooting state, so it is possible to lead the shooting to a better shooting state.

[0232] Furthermore, in the above-mentioned embodiment, the electronic camera of a unitary structure is explained, but the present invention is not limited to this. For example, it is possible to apply the present invention to an electronic camera which is separately structured by an image pick-up unit and information equipment (computer or the like).

[0233] As a specific example of the above case, the operations can be divided into: (1) The image data which is continuously imaged in the image pick-up unit side is temporarily stored. (2) An image is selected and saved among a series of image data in response to the good/bad evaluation of the shooting state by the program execution of the computer side.

[0234] Furthermore, when the present invention is applied to a computer, it is acceptable to independently perform “the image selection program to select and save an image among a series of image data in response to the good/bad evaluation of the shooting state” on the computer side. Needless to say, in this type of structure, there is a disadvantage such that the collection of information of the shooting state from the camera side is insufficient, but it is possible to perform the operation as a single computer if the good/bad evaluation of the spatial frequency component is available, so it is possible to obtain almost the same operation effect as the structure in the present invention.

[0235] In the invention, the image data which has been imaged during the period of time when the shooting state is the best is selected from among the image data which has been continuously imaged. Therefore, it is possible to obtain image data in a good shooting state without using the conventional correction mechanism for blurring due to hand shaking.

[0236] Therefore, it is possible to omit the optical system for the conventional correction of blurring due to hand shaking, and size reduction and weight reduction of the shooting lens can be improved.

[0237] Furthermore, it is possible to omit the space to dispose the optical system for the correction of blurring due to hand shaking from the shooting lens. As a result, the degree of freedom becomes high in terms of the optical design, and the aberration performance and the like of the shooting lens can be optimized without any difficulty.

[0238] Furthermore, the slight internal reflection which occurs in the optical system for the conventional correction of blurring due to hand shaking can be solved. Therefore, the flare during backlight shooting can be decreased and the camera image quality can be significantly improved.

[0239] Furthermore, it is possible to omit the driving mechanism for the conventional correction for blurring due to hand shaking or the like, and electricity conservation in the electronic camera can be improved. Additionally, problems such as noise and vibration from the driving mechanism for the correction for blurring due to hand shaking can be solved.

[0240] Furthermore, the selection processing of the image data is performed after the shooting is completed, so there are advantages such that the processing load during the shooting period does not significantly increase and the number of shooting frames per time unit does not decrease much.

[0241] In the invention, the temporary memory means begins the temporary storage of the image data after the release operation of the electronic camera. Because of this, it is possible to stop the image pick-up operation prior to the release operation. Accordingly, electricity conservation for the electronic camera can be improved.

[0242] In the invention, the temporary memory means maintains the image data from before to after the release operation. Accordingly, not limited to the image data after the release operation, it is possible to accurately select the image data in a much better shooting state from the period spanning from before to after the release operation.

[0243] Furthermore, blurring due to hand shaking has not yet occurred immediately before the release operation in accordance with the release operation. Therefore, when blurring due to hand shaking is evaluated as a shooting state, by adding the period immediately before the release operation to the sampling range of the image data, it is possible to select the image data with extremely little blurring due to hand shaking at high probability.

[0244] Furthermore, the sampling range of the image data spans from before to after the release operation, so the worst value of the release time lag (equivalent to the edge point of the sampling range of the image data) can be decreased by almost half compared to the case when the sampling range of the same time length begins with the release operation.

[0245] In the invention, the temporary memory means and the image saving means use the same memory mechanism. Therefore, there is no need for a memory mechanism for only the temporary memory means, and it is possible to simplify the construction of the electronic camera.

[0246] In the invention, the image data which is continuously imaged is differentially compressed and then is temporarily stored. Therefore, it is possible to keep the encoding amount of the image data small and to minimize the memory capacity of the temporary memory means.

[0247] Furthermore, if the memory capacity of the temporary memory means does not change, it is possible to increase the number of samplings of the image data which can be temporarily stored. In this case, because the selection is performed among more image data, the possibility of obtaining image data in a much better shooting state can be significantly higher.

[0248] In the invention, image data in a much better shooting state is selectively retained among the image data which is continuously imaged. Therefore, it is possible to obtain image data in a good shooting state without using the conventional correction mechanism for hand shaking or the like.

[0249] Additionally, image data is overwritten and recorded in the memory medium, so it is sufficient to have merely enough capacity to store at least one frame of image data. Therefore, it is not necessary to have a large capacity memory medium for temporary storage, and it is possible to simplify the construction of the electronic camera.

[0250] In the invention, as a good/bad evaluation of the shooting state, the blur amount of the image pick-up means is detected. As a result, it is possible to select and save the image data with appropriately little hand shaking.

[0251] In the invention, as a standard of a good/bad evaluation of the shooting state, the spatial frequency component of the image data is used. As a result, it is possible to select and save image data with appropriately little overall blurring due to hand shaking, movement of the object, and misfocus.

[0252] Particularly, this type of good/bad evaluation of the spatial frequency component can be performed by a calculation, so a piezoelectric gyro or the like for the detection of blurring due to hand shaking is not needed. Therefore, even if the invention as set forth in claim 8 is used, it is not particularly necessary to add a sensor part or the like to the conventional electronic camera, and it is possible to obtain the effects of the present invention with a simple structure at low cost.

[0253] Furthermore, particularly, with respect to an object showing unpredictable movement such as a flower swayed by the wind, it is extremely difficult to completely prevent misfocus by ordinary AF (autofocus) shooting only. However, in the invention as set forth in claim 8, even under a bad condition like this, based upon the spatial frequency component, it is possible to reliably select and save the image data with little misfocus.

[0254] In the invention, the high-area component amount of the spatial frequency is determined by the compressed encoding amount. This type of value of the compressed encoding amount can be obtained by the result of conventional image compression processing or the like, so it is not necessary to add a particular calculation processing, and it is possible to decrease the processing time and the calculation processing amount.

[0255] In the invention, for the good/bad evaluation of the shooting state, the release time lag is used. As a result, it is possible to select and save good image data with comparatively little release time lag.

[0256] Especially, in a state where temporary storage of the camera image has been performed since before the execution of the release operation, when image data with little release time lag is selected, it is possible to obtain image data where the release time lag is extremely close to 0.