Lens device, and electronic camera using same

Description: TECHNICAL FIELD [Detailed description of the invention]

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INDUSTRIAL APPLICABILITY The present invention relates to a lens device, an electronic camera using the lens device, specifically, a lens device for driving a retractable zoom lens by a stepping motor, and an electronic camera including the lens device. It is particularly related to drive control of a lens lens frame in an electronic camera.

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PROBLEM TO BE SOLVED: In recent years, an electric image signal is generated by using a camera for taking a picture or the like using a film for taking a picture, an image sensor or the like, and the image signal is recorded on a recording medium or the like. In the electronic cameras and the like (hereinafter, both are collectively referred to as cameras and the like), it is desired to reduce the size of the camera body so that it is convenient to carry and use.

On the other hand, there is a demand for even higher functionality such as higher accuracy of the automatic focus adjusting device (autofocus device = AF device) and higher magnification of the zoom lens used as a photographing lens. ..

Therefore, in conventional cameras and the like, various measures have been taken to achieve both miniaturization and high functionality of the camera body. For example, when the camera is not in use, a photographic lens barrel (also referred to as a zoom lens barrel when the photographic lens is a zoom lens) containing a plurality of lens lens frames for holding the photographic lens is placed inside the camera body. While trying to reduce the size when carrying the lens by storing it, when using the camera, the lens barrel is extended toward the front of the camera body, and multiple lens lens frames inside the lens barrel are positioned at predetermined positions. Those equipped with a so-called retractable zoom lens device that realizes a variable magnification operation (zoom operation) and an automatic focus adjustment operation (AF operation) by moving each of them are generally put into practical use.

In this retractable zoom lens device or the like, a storage position in which the lens mirror frame is housed inside the camera body and a lens mirror frame extended so as to protrude from the front surface of the camera body for shooting. The storage section that moves between the shooting preparation position in the state where the shooting is possible and the moving section of the lens mirror frame during the shooting operation starting from the shooting preparation position, that is, the predetermined lens mirror frame moves for the zoom operation. The lens mirror frame is configured to be moved in two movement sections, which is a possible zoom section.

When the moving section of the lens barrel is roughly divided into two different operations, that is, the zoom section (also referred to as the zoom area) that mainly performs the zoom operation, and the lens barrel. When the lens is configured to have a storage section for storing the lens inside the camera body, the requirements for driving the lens mirror frame are different in both sections.

In a normal case, the movement of the lens mirror frame in the zoom section is a movement mainly performed for a shooting operation, so that a higher accuracy of movement is required. On the contrary, in the storage section, high accuracy is not required, but quicker operation is required, and it is necessary to quickly move the lens barrel to the storage position by high-speed and reliable movement. For this reason, it is desirable to control the drive of the lens mirror frame under the optimum drive conditions according to each movement section.

In consideration of such a point, for example, in the lens driving device disclosed by Japanese Patent No. 2702474, the driving speed of the zoom lens is changed between the zoom section and the other sections. That is, in the zoom section, the driving speed of the zoom lens is controlled to be driven at a low speed, while in the non-zoom section, the driving speed of the zoom lens is controlled to be driven at a high speed.

According to this, by speeding up the movement of the zoom lens in the non-zoom section, it is possible to shorten the switching time from the movable state of the device to the retracted state.

As described above, in the means disclosed in Japanese Patent No. 2702474, paying attention to the driving speed of the zoom lens required for each of the zoom section and the other moving section, the zoom section and the other parts are used. It is controlled to change the driving conditions of the zoom lens in the moving section.

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However, in a normal retractable zoom lens device, the following driving conditions may be required in addition to the driving speed. Usually, in the storage section of the lens mirror frame, a means for operating at a relatively high speed is often used by devising a mechanism including a cam or the like for moving the lens mirror frame. Further, it is conceivable that an unexpected external force is applied to the lens barrel or the like that holds the lens lens frame. Therefore, a sufficient drive torque is required to execute the drive control in the storage section in which the lens barrel is housed.

Further, in the zoom section, in order to adjust the zoom magnification with high accuracy, it is indispensable to move in finer steps, and also to reliably position a predetermined lens mirror frame at a predetermined position. , More accurate drive control will be required.

Further, for example, in an electronic camera or the like, since it is necessary to operate an electric circuit or the like related to a shooting system having a relatively large power consumption during a shooting operation, it is consumed by an electric circuit system other than the shooting system during the shooting operation. It is necessary to keep the amount of power generated low.

Therefore, for this purpose, if the power consumption is relatively large and the drive current related to the zoom operation, which is frequently used during the shooting operation, can be reduced, a high power saving effect can be expected. Therefore, it can be said that reducing the drive current related to the zoom operation during the shooting operation is a particularly desired function in recent years.

By the way, as described above, an unintended unexpected external force is applied to the lens barrel or the like that holds the lens lens frame, for example, as shown in the schematic diagram of FIG. 9, an external force is applied to the front lens barrel 102 at the time of photographing. When F acts, the mirror frame 102 may move toward the inside of the camera body 101, and may deviate from the original position where the front lens mirror frame 102 should be arranged.

Conventionally, an encoder for position detection is provided on the lens lens frame and the drive cam, and a so-called closed-loop lens barrel drive system in which the encoder and the drive DC motor are combined is adopted. The problem of misalignment due to the external force F as described above has been solved. According to this, even if the position of the lens mirror frame changes due to an external force or the like, the change in the position can be detected by the encoder, and this can be corrected.

Examples of the lens barrel corresponding to the abnormal operation of the lens lens frame are disclosed in, for example, JP-A-6-347683, JP-A-7-218807, JP-A-9-230215 and the like. Some of these technical means use the encoder output for detecting the position of the lens barrel to detect abnormal operation.

As a drive method for the lens mirror frame, a drive method using a stepping motor controlled by a drive pulse as a drive source is more cost effective than a combination of a DC motor and an encoder as described above. It is well known that it is advantageous both in terms of occupied space. For example, in the means disclosed in Japanese Patent Application Laid-Open No. 5-188267, a stepping motor is used as a drive source of the lens mirror frame, and a photo sensor is used as a detection means for detecting a reference position (home position). I try to do it.

On the other hand, driving conditions such as a driving speed for driving a lens mirror frame and the like are closely related to a driving source such as a motor. Therefore, in order to control the drive source by reliably adapting to various drive conditions, it is indispensable to limit the drive source. Normally, as a drive source for a lens barrel in a camera or the like, a stepping motor or the like that does not require a member such as an encoder has been widely used.

Here, a general driving method of a stepping motor will be briefly described. Generally, the driving method of a normal stepping motor includes a one-phase excitation drive shown in FIG. 10, a two-phase excitation drive shown in FIG. 11, a 1-2 phase excitation drive shown in FIG. 12, and the like, and further, microstepping. There are various driving methods such as driving (not shown).

The one-phase excitation drive is a drive type in which the A-phase and B-phase coils are alternately energized as shown in FIG. Therefore, while it is possible to drive with low power consumption, the drive torque is characterized by a relatively low drive system.

Further, in the case of two-phase excitation, the magnetic poles of the rotor move so as to face the middle of two adjacent magnetic poles of the stator, but the amount of rotation rotated by one change of the magnetic poles is 1. It is the same as the case of phase excitation. As shown in FIG. 11, this two-phase excitation is a drive type in which the A-phase and B-phase coils are energized at the same time. Therefore, in the case of two-phase excitation, it is necessary to constantly excite the stator in order to keep the motor stopped. From this, it is said that two-phase excitation requires more power consumption than one-phase excitation, but can be driven with a higher drive torque than one-phase excitation, and faster movement can be realized. There is a feature.

In the case of 1-2 phase excitation, 1-phase excitation and 2-phase excitation are repeated. Therefore, for example, when rotation starts from a position facing the magnetic pole of the stator, the next magnetic pole becomes The change causes the rotor to move between the two adjacent magnetic poles of the stator, and the next change in the magnetic pole moves the rotor to a position facing the adjacent magnetic poles. As a result, the amount of rotation obtained by changing the magnetic pole of the stator once becomes the amount of rotation equivalent to one half of that in the case of one-phase excitation or two-phase excitation. Therefore, in the case of 1-2 phase excitation, the amount of rotation per magnetic pole change can be reduced as compared with the case of 1 phase excitation or 2 phase excitation, so that finer drive can be performed and the drive is higher. It has the feature that accurate positioning accuracy can be ensured, and has the advantage of being able to reduce vibration and noise.

Further, the micro step drive is a drive method capable of realizing a finer step angle electrically, and can secure a higher accuracy of positioning than in the case of 1-2 phase excitation. At the same time, it has the feature that it can contribute to low vibration and low noise.

When the stepping motor is used in this way, the lens mirror frame can be moved more efficiently by controlling the stepping motor drive method to be switched according to the required drive conditions. Very convenient.

By the way, in the inner focus type zoom lens barrel, the most problematic issue with respect to the displacement of the front lens frame due to an external force is the positional relationship between the zoom lens and the focus lens. According to the focusing method often used in conventional silver halide cameras, the position of the focus lens is determined by the position of the zoom lens and the distance information measured, so that the front lens frame is used as described above. It is not allowed to deviate from the original position. Therefore, in the conventional means, it is an indispensable problem to detect the position of the lens mirror frame by the encoder and manage it so that it is always in a predetermined position.

Further, in a conventional electronic camera, a video movie, or the like, a so-called contrast focusing method is used in which a high frequency component of a signal acquired by an image sensor is detected and the focusing state is performed without relying on distance information. Generally, the one used is used, but it is also known that the one using this focusing means does not require strictness in the positional relationship between the zoom lens and the focus lens.

However, as described above, in the conventional electronic camera or the like that employs the contrast focusing method, there is no particular problem in the shooting operation as long as the front lens mirror frame is slightly displaced due to an external force or the like. Therefore, there is no need to install an encoder. However, in the case where a stepping motor is used as a drive source for moving the lens mirror frame, when the deviation amount of the front lens mirror frame becomes larger than a certain level, the lens mirror frame is in the reference position to correct this. It can only be done when returning to (home position). For this reason, for example, if the front lens mirror frame of the lens mirror frames in the camera used by the photographer during the execution of the shooting operation is largely misaligned, this misalignment state is established. It is possible that you may continue shooting without knowing. Then, the following problems will occur.

That is, it is conceivable that the distance between the zoom lens and the focus lens is not the original distance, and the moving focus lens collides with the adjacent zoom lens or the like during the focusing operation.

Further, after the focusing operation is completed, the subject distance is calculated based on the relationship between the position of the zoom lens and the position of the focus lens, and the information on the subject distance is used as camera control information for controlling the strobe device or the like. When using it, if the misalignment is large, the error of the camera control information becomes large, which may deteriorate the image quality.

Due to the above-mentioned problems, the zoom lens barrel in which the front lens frame, which is applied in conventional electronic cameras and the like, is provided so as to be able to move forward and backward, has a lens barrel drive structure using a stepping motor as a drive source. It is considered difficult to make a configuration that does not use an encoder.

The present invention has been made in view of the above points, and an object of the present invention is to move the lens mirror frame to the inside of the camera body more quickly during the storage operation. Efficient drive control can be performed according to the required drive conditions by performing drive control that allows the lens mirror frame to move with higher accuracy during zoom operation during shooting operation. It is an object of the present invention to provide a lens device that can be realized and thereby contribute to a reduction in power consumption of the entire device.

Further, in the present invention, the drive control of the stepping motor used as a drive source for moving the lens mirror frame, particularly in an electronic camera or the like, is optimally performed according to a plurality of drive methods (drive modes). It is an object of the present invention to provide an electronic camera provided with a lens device that can contribute to reduction of power consumption, thereby obtaining both good usability and operability.

Further, according to the present invention, even when the position shift of the lens mirror frame on the subject side occurs due to an external force applied to the lens mirror frame or the like, this position shift is automatically solved by the shift correction process. It is an object of the present invention to provide a camera having a small-sized, low-cost zoom lens barrel that enables the continuation of a shooting operation.

Further, the present invention performs a zoom operation during execution of a moving image shooting operation and a zoom operation during execution of a still image shooting operation in an electronic camera capable of generating and recording moving image data and still image data. By controlling the drive in different drive modes, it is possible to prevent noise components such as the driving sound of the motor, etc. associated with the zoom drive from being recorded at the same time during the execution of the movie shooting operation, and to suppress vibration to obtain a good moving image. It is an object of the present invention to provide an electronic camera capable of recording data and comfortably recording still image data.

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[Means for solving problems] In the lens device of the present invention, the variable magnification operation is executed including the storage section between the storage position in the stored state and the shooting preparation position in the shooting ready state and the shooting preparation position in the lens barrel. A plurality of lens mirror frames that move the zoom section to hold the photographing optical system, a stepping motor that moves the plurality of lens mirror frames, and the plurality of lens mirror frames from the storage position to the shooting preparation position. The stepping motor is driven and controlled by the first drive mode during the feeding operation of moving the lens mirror frame and the storage operation of moving the lens mirror frame from an arbitrary position in the zoom section to the storage position, and the lens mirror frame is driven and controlled by the first drive mode. The drive control means is provided with a drive control means for driving and controlling the stepping motor in a second drive mode in which the stepping motor is operated with a current lower than that of the first drive mode during a zoom operation in which the lens is moved within the zoom section. In the first drive mode, the stepping motor is driven and controlled by two-phase excitation, and in the second drive mode, the stepping motor is driven and controlled by 1-2 phase excitation or microstep drive. When the drive control means issues a signal instructing to stop the power supply based on the operation of the power switch and the lens mirror frame is moved from an arbitrary position in the zoom section to the storage position, the drive control means is used. The stepping motor is driven and controlled by two-phase excitation.

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[0038] The electronic camera of the present invention has an electronic imaging means for generating an image signal by photoelectric conversion of a subject image formed by an imaging optical system, and a predetermined process for the image signal generated by the electronic imaging means. In an electronic camera provided with an image processing means for converting the image into a predetermined form and a recording means for recording the output from the image processing means as image data, the lens mirror frame is housed in the lens barrel. Moves to the storage section between the storage position where the lens is ready to be taken and the shooting preparation position where shooting is possible, and the zoom section where the variable magnification operation is executed including the shooting preparation position, and holds the shooting optical system. A plurality of lens mirror frames, a stepping motor for moving the plurality of lens mirror frames, a transmission means for transmitting the driving force of the stepping motor to the lens mirror frame, and the plurality of lens mirror frames from the storage position to the above. The stepping motor is driven and controlled by the first drive mode during the feeding operation of moving to the shooting preparation position and the storing operation of moving the lens mirror frame from an arbitrary position in the zoom section to the storage position. A drive control means for driving and controlling the stepping motor by a second drive mode in which the stepping motor is operated with a current lower than that of the first drive mode is provided during a zoom operation in which the lens mirror frame moves within the zoom section. In the first drive mode, the drive control means drives and controls the stepping motor by two-phase excitation, and in the second drive mode, drives and controls the stepping motor by 1-2 phase excitation or microstep drive. Further, the drive control means issues a signal instructing to stop the power supply based on the operation of the power switch, and the lens lens frame is moved from an arbitrary position in the zoom section to the storage position. In this case, the stepping motor is driven and controlled by two-phase excitation.

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BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the illustrated embodiments. The following embodiments of the present invention exemplify an electronic camera (hereinafter, abbreviated as a camera) configured to acquire an electrical image signal using an image sensor or the like.

In the camera according to the embodiment of the present invention, the operation of the entire camera is controlled by the system controller 8 as a control means as shown in the block configuration diagram of FIG. The system controller 8 includes a release switch (SW) 11 that generates a signal instructing the start of shooting among a group of operation switches that are operating means, and a zoom-up switch (SW) that generates a signal instructing a zoom-up operation among the zoom operations. SW) 9, similarly, a zoom down switch (SW) 10 that generates a signal instructing a zoom down operation, and a power switch (SW) that generates a signal (power on signal and power off signal) instructing the start and stop of power supply. ) 12 and the like are electrically connected, and each operation output signal is input to the system controller 8.

In this camera, when the release switch 11 first instructs the start of shooting, the subject image captured via the shooting optical system of the zoom lens barrel 1 is converted into an electric signal by the imager 2 which is an image sensor. In the image pickup circuit 3, image processing such as sample hold is performed on the electric signal, and the output image signal is converted into a digital signal by the A / D conversion circuit 4. Next, in the focusing circuit 7, contrast information for focusing driving of the photographing lens is extracted from the high frequency component of the digital image signal output from the A / D conversion circuit 4, and is output to the system controller 8.

On the other hand, the image signal output from the A / D conversion circuit 4 is output to the image processing circuit 13 which is an image processing means, and after various image processing is performed here, a memory 14 such as a buffer memory 14 is used. It is temporarily stored in. The image signal stored in the memory 14 is output to a display means (hereinafter, simply referred to as LCD) 16 such as a liquid crystal display via a display circuit 15 as needed, and is displayed as an image on the display means (hereinafter, simply referred to as LCD) 16. Further, after being output to the compression / decompression circuit 19 and subjected to a compression process suitable for recording, it is output to a recording medium 18 such as a memory card or a flash memory via an interface (I / F) 17 which is a recording means. Recorded in this. The image signal recorded in the compressed form on the recording medium 18 receives a predetermined instruction signal from the operation switch group, is read into the compression / expansion circuit 19 via the I / F 17, and is displayed here. After being subjected to a decompression process suitable for the above, it is read into the memory 14 and then displayed and output to the LCD 16 via the display circuit 15.

In the present embodiment, the block including the imager 2 and the image pickup circuit 3 and the like generates an image signal by photoelectric conversion of a subject image formed by a photographing lens held in a plurality of lens mirror frames. It is an electronic imaging means. Further, a block including at least this electronic imaging means and further formed by constituent members such as the A / D conversion circuit 4 and the focusing circuit 7 is referred to as a photographing block.

The system controller 8 drives the focus motor 29 built in the zoom lens barrel 1 via the focus motor drive circuit 6 to perform the focusing operation (AF operation) of the zoom lens barrel 1. It has become.

When the zoom-up SW9 or the zoom-down SW10 is operated prior to the operation of the release SW11 during the shooting operation, the system controller 8 causes the zoom motor drive circuit based on the input zoom operation instruction. It also serves as a drive control circuit that drives the zoom motor 26 built in the zoom lens barrel 1 via the zoom lens 5 to perform a variable magnification operation (zoom operation) of the photographing optical system.

A battery 42, which is a drive power source, is electrically connected to the system controller 8 via a power supply circuit 41. The power supply circuit 41 supplies power to each internal circuit of the camera under the control of the system controller 8.

As shown in FIG. 1, the zoom lens barrel 1 holds a photographing optical system such as a 1st group lens 22, a 2nd group lens 23, a 3rd group lens 24, and a 4th group lens 25, and a 1st group lens 22. A group 1 lens frame 21, a zoom cam frame 27 that performs a variable magnification operation (zoom operation), a zoom motor 26 that drives the zoom cam frame 27, and a photographing lens system for performing a focusing operation (AF operation). A focus motor 29 that moves a predetermined lens group in a direction along the optical axis O, an auxiliary frame 28 that holds the focus motor 29, and a photoreflector that is a position detecting means; PR (A) 31 and a photoreflector; PR. (B) It is composed of each member such as 32.

The zoom lens barrel 1 will be described in more detail. FIG. 2 is a perspective view showing a zoom lens barrel of the camera of the present embodiment.

[0066] The zoom lens barrel 1 includes a fixed frame 30 that fixedly supports the zoom lens barrel 1 on the front surface of the camera body (not shown), a plurality of lens groups (22, 23, 24, 25), etc. (in FIG. 2). A zoom motor 26 (not shown in FIG. 2, see FIG. 1) composed of the above-mentioned photographing optical system including a part thereof (see FIG. 1), a stepping motor as a zoom drive source, and the zoom motor 26. It is a driven transmission means that is rotatably supported by the fixed frame 30 and supports the 1st group lens frame 21, the 2nd group lens 23, the 3rd group lens 24, the auxiliary frame 28, etc. so as to be able to advance and retreat in the direction along the optical axis O. A zoom cam frame 27, which is a cam member, and a focus motor 29 (not shown in FIG. 2, see FIG. 1) that moves a group 4 lens 25 (see FIG. 1) in a direction along the optical axis O to perform a focusing operation. , The focus motor 29 and the like are attached, and the auxiliary frame 28 for focus drive (not shown in FIG. 2, see FIG. 1) that supports the 4th group lens 25 in the direction along the optical axis O so as to be able to move forward and backward, and the zoom cam. It is composed of two PR (A) 31, PR (B) 32 and the like, which are position detecting means for detecting the position of the cam pin engaged with the cam groove 27a of the zoom cam frame 27 by detecting the rotational state of the frame 27. ing.

The 1st group lens 22 is arranged closest to the subject, is arranged so as to project toward the front from the camera body during the shooting operation, and is held by the 1st group lens frame 21. Further, the 2nd group lens 23, the 3rd group lens 24, the 4th group lens 25 which is a focus lens, and the like are housed inside the zoom cam frame 27.

The PR (A) 31 and the PR (B) 32 are arranged side by side along the same circumferential direction on the outer peripheral surface of the fixed frame 30. Reflective members are located at predetermined positions on the outer peripheral surface of the zoom cam frame 27 at positions facing the passage paths of the PR (A) 31 and PR (B) 32, respectively, along a direction orthogonal to the optical axis O. The detection pattern (A) 33 and the detection pattern (B) 34 are attached side by side. The detection pattern (A) 33 is formed so that the detection period is longer than that of the detection pattern (B) 34, and the length of the detection pattern (A) 33 is PR (A) 31 · PR (B). ) It is set to be longer than the interval of 32.

Therefore, when the PR (A) 31 and the PR (B) 32 receive the reflected light of the detection pattern (A) 33 and the detection pattern (B) 34, the PR (A) 31 and the PR (B) 32 The output signal will be detected from each. As a result, it is possible to detect the position of the zoom cam frame 27, that is, the position of the zoom lens barrel 1 when it moves in the retracted section and the zoom section (see FIG. 4).

The zoom cam frame 27 has a substantially cylindrical shape, and a group 1 lens frame 21 is slidably fitted to the outer peripheral portion thereof. Further, the zoom cam frame 27 is provided with a cam groove 27a having a predetermined shape at a predetermined position on the peripheral surface, and the cam groove 27a is directed toward the inner peripheral side of the group 1 lens frame 21. The protruding drive pin is fitted. Further, the group 1 lens frame 21 is adapted to be guided straight in the direction along the optical axis O by a straight guide groove provided on the inner surface side of the protruding arm portion 30a of the fixed frame 30. Therefore, when the zoom cam frame 27 is rotated by the zoom motor 26, the group 1 lens frame 21 is driven forward and backward in the direction along the optical axis O in response to the rotation, and the zoom lens barrel is moved to the rearmost position of the retracted area ( It moves from the retracted position (retracted position or retracted position) to the most advanced position (maximum telephoto position) of the zoom section.

Inside the zoom cam frame 27, the second group lens 23, the third group lens 24, and the auxiliary frame 28 are held so as to be able to move forward and backward in the optical axis direction, and the zoom cam frame 27 is rotated by the zoom motor 26. As a result, each member of the photographing system such as the second group lens 23, the third group lens 24, and the auxiliary frame 28 moves in the direction along the optical axis O.

Further, during the zoom operation, the focus motor 29 also moves integrally with the advancing / retreating movement of the auxiliary frame 28, and at the same time, the focus motor 29 is rotationally driven according to a predetermined tracking curve, so that the four-group lens 25 is moved. Move to the in-focus position at each zoom position.

[0073] Fig. 3 conceptually shows the extension position relationship of each lens group when the zoom lens barrel in the present camera reaches the tele end position from the retracted position through the wide end position (which is also the shooting preparation position). It is a figure which shows.

In FIG. 3, the retractable position is a position when the zoom lens barrel 1 is completely housed inside the camera body, and indicates the position at the end of the retractable section. Further, the wide end (position) and the tele end (position) indicate the moving range of the zoom lens lens barrel 1 when the camera is in a shooting capable state, that is, the positions of both ends in the zoom section, and the variable magnification of the shooting lens is closer to the wide angle. The farthest position is called the wide end, and the farthest position from the telephoto end is called the telephoto end. The wide end is a shooting preparation position and is also the most end position on the front end side in the retracted section.

As shown in FIG. 3, when the zoom lens barrel 1 moves from the retracted position to the wide end (shooting preparation position), the 1st to 4th group lenses 22 to 25 are extended to a predetermined position at the wide end. This camera is ready for shooting.

Further, in the section from the wide end to the tele end, the 1st group and 3rd group lenses 22 and 24 are extended and moved in the direction along the optical axis O to perform a scaling operation (zoom operation). In response to this, the 4-group lens 25 is also extended and moved in the same direction within a predetermined range. The four-group lens 25 performs a focus adjustment operation (AF operation) by moving within the range shown by the diagonal line in FIG. 3, that is, within the focus movement range.

The extension position of the 4th group lens 25 is determined by the subject distance and the variable magnification. That is, as shown by the closest curve and the infinity curve in FIG. 3, the extension position of the 4-group lens 25 with respect to the same subject distance changes according to the variable magnification.

Further, as described above, when the PR (A) 31 and the PR (B) 32 are arranged at positions facing the detection pattern (A) 33 and the detection pattern (B) 34, each of them is a detection pattern ( The reflected light from A) 33 and the detection pattern (B) 34 will be received. In response to this, the PR (A) 31 and the PR (B) 32 are adapted to generate an on signal. Therefore, it is detected whether the zoom cam frame 27 is in the retracted section or the zoom section based on the output signals of PR (A) 31 and PR (B) 32 and the rotation angle of the zoom cam frame 27. It has become like.

FIG. 4 is a diagram showing the output signals of PR (A) 31 and PR (B) 32 and the regions (zones) in the zoom section that can be detected by the output signals. That is, in the present embodiment, the arrangement of the PR (A) 31 / PR (B) 32 and the detection pattern (A) 33 / detection pattern (B) 34 is devised as described above, so that the PR (A) 31 And PR (B) 32 can detect four regions (reference numerals Z1 to Z4 in FIG. 4) in the zoom section.

The camera of the present embodiment has the above-described configuration, and for example, an external force acts on the group 1 lens frame 21 which is one of the lens mirror frames protruding from the camera body. The zoom motor 26 has largely stepped out when the group lens frame 21 has moved significantly toward the camera body, or when an external force acts on the group 1 lens frame 21 during zoom drive. In such a case, the original zoom position data stored in advance in the system controller 8 and the zoom position of the zoom cam frame 27 actually detected will be different. For example, when a drive instruction is given by the system controller 8 and the zoom position should be at the tele end, and the actual zoom cam frame 27 is at a position near the wide end, the instruction signal of the system controller 8 is used. There may be a difference between the position data of the zoom cam frame 27 defined based on the above and the zoom position of the zoom cam frame 27 detected by PR (A) 31 and PR (B) 32.

Therefore, in the camera of the present embodiment, in such a case, the zoom motor 26 is driven to rotate the zoom cam frame 27 so as to be retracted to a predetermined position at the wide end. When the position of the zoom cam frame 27 detected by the PR (A) 31 and the PR (B) 32 is the retractable section, the zoom cam frame 27 is extended to a predetermined position at the wide end. At the same time, the zoom position data of the system controller 8 is also rewritten to the data indicating the wide end. As a result, when an abnormality occurs in the position of the zoom cam frame 27 due to an external force or the like, the position of the zoom cam frame 27 is corrected.

The operation of the camera according to the above embodiment during the shooting operation will be described below.

FIG. 5 is a flowchart showing a sequence of shooting operations in the camera of the present embodiment.

First, in step S11, the system controller 8 of the electronic camera confirms the state of the power SW12 among the operation switch group, and when it is confirmed that the power SW12 is turned on, the process of the next step S12 is performed. Move to.

In step S12, a subroutine of the shooting preparation process, that is, a process in which the zoom lens barrel 1 is extended from the retracted position to the shooting preparation position (wide end position of the zoom section) to prepare the electronic camera for shooting. (Lens extension process) is executed.

Next, in step S13, the system controller 8 monitors the state of the output signal of PR (B) 32, and when an on signal from PR (B) 32 is detected, the process of the next step S15. Proceed to. If the on signal from PR (B) 32 is not detected in step S13, the operation of the abnormality processing subroutine (see FIG. 8) in step S14 is executed, and then the process proceeds to step S15.

In step S15, the system controller 8 rotationally drives the zoom motor 26 in a predetermined direction (here, the forward rotation direction) via the zoom motor drive circuit 5 to rotate the zoom cam frame 27. Then, in response to this, a plurality of lens lens frames such as the group 1 lens frame 21 are extended in the direction along the optical axis O, and the zoom lens barrel 1 is extended accordingly. At this time, the zoom motor 26 is driven and controlled by the system controller 8 in the two-phase excitation drive, which is the first drive mode. Then, when the zoom lens barrel 1 moves to the shooting preparation position, the output signal of the PR (A) 31 is turned on.

That is, the system controller 8 monitors the state of the output signal of the PR (A) 31, and the processing after the above step S15 until the on signal from the PR (A) 31 is detected in the step S16. Is repeated. Then, when the on signal from the PR (A) 31 is detected in the above-mentioned step S16, the process proceeds to the next step S17. In step S17, the system controller 8 controls the power supply circuit 41 to start supplying power to the photographing block (turning on the power of the photographing block).

By starting the power supply to the shooting block in this way, a state in which actual shooting can be performed, that is, a shooting preparation state is set. In this state, the photographer arbitrarily operates a group of operation switches to perform a desired operation.

For example, the zoom processing subroutine in step S18 is executed by operating the zoom-up SW9 or the zoom-down SW10, whereby a desired zoom operation is performed (see FIG. 7).

During this zoom operation, the following processing is performed. That is, the system controller 8 which is the drive control means drives and controls the zoom motor 26 via the zoom motor drive circuit 5. At this time, the zoom motor 26 operates at a lower current than the first drive mode. The drive is controlled by the 1-2 phase excitation drive or the microstep drive, which is the drive mode of 2. Then, by operating an operation switch different from the zoom down SW9 and the zoom down SW10, the subroutine of this zoom process is terminated, and the camera returns to the shooting standby state (main routine) (return).

Here, the sequence of zoom processing will be described in more detail with reference to the flowchart of FIG.

As described above, when the zoom processing sequence is entered by the instruction signal from the zoom-up SW9 or the zoom-down SW10, the output signal of the zoom switch, that is, the zoom-up SW9 or the zoom-down SW10 is turned on in step S21. If any switch is in the on state, the process proceeds to step S22, and if any switch is in the off state, the process proceeds to step S30. ..

In step S22, the zoom mode is entered, and in the next step S23, the pulse drive of the zoom motor 26 is started. Subsequently, in step S24, the output drive pulse value P is added or subtracted to perform count-up or count-down, and this is stored.

Next, in step S25, the system controller 8 calculates the zoom position data corresponding to the drive pulse value P stored in step S24 described above. This zoom position data is data indicating which position of the zoom lens barrel 1 is in the moving range (range from the retracted position to the wide end position and from the wide end position to the tele end position). It corresponds to the rotation angle of the zoom cam frame 27. In this way, the system controller 8 serves as a calculation means for calculating zoom position information (data) from the drive pulse value P (drive pulse signal) that drives the zoom motor 26 (stepping motor).

In step S26, the normal zoom position determination mode is entered, and in the next step S27, the drive pulse value P described above and the pulse value corresponding to the original zoom position data stored in advance in the system controller 8 are used. Make a comparison.

The drive pulse of the zoom motor 26 basically corresponds to the actual zoom position unless the stepping motor is stepped out.

Therefore, in this step S27, PR (A) 31 and PR (B) 32 determine whether or not the drive pulse value P of the zoom motor 26 and the pulse value of the zoom position that should be originally matched. Determined by the output of.

This determination corresponds to the points indicated by the reference numerals C1, C2, C3, and C4 in FIG. 4 when the ON / OFF state of the output signal of PR (A) 31 or PR (B) 32 is switched. It is performed only at the zoom position).

That is, the outputs of PR (A) 31 and PR (B) 32 are constantly monitored by the system controller 8, and the zoom positions are the positions indicated by the reference numerals C1, C2, C3, and C4 in FIG. 4, respectively. At that time, the drive pulse value P of the zoom motor 26 at that time is compared with the drive pulse value corresponding to the zoom position in the symbols C1, C2, C3, and C4.

Here, when the drive pulse value P and the pulse value corresponding to the original zoom position match, it is determined that the state is normal, and the process proceeds to step S29. On the other hand, when the drive pulse value P and the pulse value corresponding to the original zoom position do not match, it is considered that the zoom cam frame 27 is moved by the action of, for example, an external force during the zoom drive, which is normal. It is determined that the state is not in the above state, and the process proceeds to step S28.

[0102] In step S28, the system controller 8 corrects the zoom position data stored inside the system controller 8 so as to be the zoom position data detected by the PR (A) 31 and the PR (B) 32. Here, the system controller 8 serves as a correction means for correcting the zoom position information calculated during the zooming operation according to the outputs of the PR (A) 31 and the PR (B) 32 (position detecting means). After that, the process proceeds to step S29.

Next, in step S29, it is determined whether or not there is a predetermined output of PR (A) 31 and PR (B) 32 when the zoom motor 26 is driven with a predetermined number of pulses or more. Here, when it is determined that the predetermined outputs of PR (A) 31 and PR (B) 32 are output, the process returns to the process of step S21 described above.

On the other hand, when the outputs of PR (A) 31 and PR (B) 32 do not reach the predetermined outputs, it is determined that some external force or the like continues to act on the group 1 lens frame 21, and step S31. In step S31, the subroutine for abnormal processing is called.

On the other hand, if it is determined in step S21 described above that all the zoom switches are in the off state, the process proceeds to step S30 as described above. In this case, in step S30, if the zoom position does not change from the previous determination, the series of zoom processing sequences is terminated (return).

On the other hand, in step S30, when it is determined that the zoom position has changed from the time of the previous determination, it is assumed that some external force or the like has acted to move the group 1 lens frame 21. Conceivable. Therefore, the process proceeds to step S31, and the exception handling subroutine is called.

[0107] Here, the details of the exception handling subroutine will be described with reference to the flowchart shown in FIG.

[0108] In step S41, the focus motor 29 is driven, and then in step S42, the group 4 lens (focus lens) 25 is moved to a predetermined infinity position. This operation is a process performed to prevent the 3rd group lens 24 and the 4th group lens 25 from interfering with each other because it is considered that the zoom lens is not in the normal extension position.

Next, in step S43, the zoom motor 26 is rotated forward or reverse to move the zoom cam frame 27 to a predetermined zoom position, that is, a predetermined position near the wide end. That is, when the zoom cam frame 27 is in the retracted section before the drive of the zoom motor 26 in step S43, the zoom motor 26 is rotated in the normal direction to rotate the zoom cam frame 27 in a predetermined direction to obtain the wide end position. Let it go out so that it becomes. Similarly, when the zoom motor 26 is in the zoom section before being driven, the zoom motor 26 is reversed and the zoom cam frame 27 is rotated in a predetermined direction so as to be retracted to the wide end position.

Next, in step S44, by checking the output signals of PR (A) 31 and PR (B) 32, it is determined whether or not the zoom cam frame 27 has reached the wide end position. Here, if it is determined that the zoom cam frame 27 has reached the same position, the process proceeds to the next step S45, and if it is determined that the zoom cam frame 27 has not reached the same position, the process proceeds to the process of step S46.

[0111] In step S46, it is confirmed whether or not the zoom motor 26 has driven a predetermined number of pulses or more. In this case, if it is confirmed that the drive has already been performed for a predetermined number of pulses or more, it is determined that the zoom operation cannot be performed normally for some reason, and the predetermined NG process is executed. Will be done. This NG process is a series of processes such as displaying a warning and stopping the shooting operation.

On the other hand, if it is determined in step S46 that the drive of a predetermined number of pulses has not been performed yet, the process returns to step S43 and the subsequent processes are repeated.

[0113] In step S45, an initialization process is performed in which the zoom position data is stored as data corresponding to the wide end position. In this way, a series of abnormal processing is completed, and the process returns to the zoom processing sequence, that is, the processing in step S21 of FIG.

Further, the shooting process in step S19 of FIG. 5 is a process executed by operating the release SW11, for example, an AE operation and an AF operation performed by the first release operation, and a release performed by the second release operation. It is a subroutine at the time of shooting operation including operation. Then, when the series of shooting operations is completed, this shooting process is finished, and the camera returns to the shooting standby state (main routine) (return).

On the other hand, in step S20 of FIG. 5, a shooting end process (power-off process), which is a process of operating the power SW12 to end the shooting state and storing the lens barrel 1 inside the camera body, is performed. It is done. The sequence of the shooting end processing will be described in detail below with reference to the flowchart of FIG.

In the camera of the present embodiment, the system controller 8 constantly monitors the output signal of the power SW12 when the shooting operation is possible, and from the power SW12 as shown in step S51 of FIG. It is determined whether or not the output signal of is a power-off signal. Here, when the off signal of the power SW12 is detected, the shooting end processing is executed.

First, in step S52, the system controller 8 controls the power supply circuit 41 to stop the power supply to the photographing block (power off). Next, in step S53, the system controller 8 rotationally drives the zoom motor 26 in a predetermined direction (here, the reverse direction) via the zoom motor drive circuit 5 to rotate the zoom cam frame 27. Then, in response to this, a plurality of lens mirror frames such as the group 1 lens frame 21 are retracted in the direction along the optical axis O, and the zoom lens barrel 1 moves in the retracted direction accordingly. At this time, the zoom motor 26 is driven and controlled by the system controller 8 by the two-phase excitation drive, which is the first drive mode. Then, when the zoom lens barrel 1 moves to the retracted position, the output signal of the PR (B) 32 is turned on.

That is, the system controller 8 monitors the output signal of the PR (B) 32, and in step S54, determines whether or not the output signal from the PR (B) 32 is an on signal. .. As described above, when the zoom lens barrel 1 reaches the retracted position and an ON signal is generated from the PR (B) 32, the system controller 8 controls the power supply circuit 41 in step S55 to drive the zoom motor. The power supply to the circuit 5 and the like is stopped (power-off processing). Then, a series of sequences of this shooting end processing is ended (end).

[0119] As described above, in the photographing end processing executed in response to the power-off signal generated by the operation of the power SW12, the zoom lens barrel 1 is partially located in the zoom section and the retracted section from an arbitrary position in the zoom section. It will move to the retracted position via. At this time, the zoom motor 26 is driven and controlled by the first drive mode (two-phase excitation drive).

That is, the shooting end process is started by the photographer arbitrarily turning off the power SW12 when the camera is in a state where the shooting operation can be executed. Therefore, the state of the zoom lens barrel 1 immediately before the power SW12 is operated is at an arbitrary position within the zoom section.

However, since it is necessary to store the zoom lens barrel 1 more quickly when the photographing end process is performed, in the present embodiment, the zoom lens barrel 1 is positioned at an arbitrary position within the zoom section. The zoom motor 26 is also driven and controlled in the first drive mode (two-phase excitation drive) even when the zoom section is moved from the position to the wide end position (shooting preparation position).

As described above, according to the above embodiment, the zoom lens barrel 1 is driven in the second drive mode (1-2 phase excitation drive or microstep drive) during the execution of the zoom process during the photographing operation. ), It is possible to secure more accurate positioning accuracy while suppressing power consumption.

Further, in the shooting end process started by receiving the power-off signal of the power SW12, even when the zoom lens barrel 1 moves in the zoom section, the first drive mode (two-phase excitation drive) is used. By controlling the drive, the lens can be driven with a higher torque than in the first drive mode, and even if an unexpected external force is applied to the moving zoom lens barrel 1, the lens mirror is surely used. The cylinder 1 can be stored. Then, at the time of the shooting end processing, the power supply to the shooting block is stopped by receiving the power-off signal, so that the power consumption can be suppressed and the zoom is surely performed even when the battery voltage is exhausted. The motor 26 can be driven.

As described above, in the electronic camera of the present embodiment, the zoom motor 26 is driven more efficiently by switching to the optimum drive control according to each moving section of the zoom lens barrel 1. It can contribute to the reduction of the power consumption of the entire camera.

Further, in the present embodiment, although the stepping motor is applied as the motor for driving the zoom, the zoom cam frame 27 has two PRs for detecting the zoom position without using the zoom encoder. Even if the position of the lens frame becomes abnormal, the position can be easily corrected by simply arranging it on the peripheral surface of the camera, and the size and cost of the camera itself can be reduced. Can contribute. For example, even if the group 1 lens frame 21 is largely displaced due to the action of an external force or the like, or if the zoom motor 26 is significantly out of step, the position is once set to the reference wide end position. By moving the zoom cam frame 27, the above-mentioned abnormal state can be corrected.

Since the focusing method is the contrast focusing method in this electronic camera, the focusing operation for detecting the information of the high frequency component of the subject image is performed again immediately before the exposure operation. When the amount of movement is such that the position of the lens frame is small, no particular problem occurs. Further, it is natural that there is no particular problem in strobe light emission control when the deviation of the lens frame is small.

The zoom motor 26 is driven and controlled by the supply voltage to the zoom motor drive circuit 5 during the execution of the photographing end process, that is, the drive voltage higher than that of the second drive mode in the first drive mode. You may try to do it. In this way, it becomes easy to secure a faster and more reliable storage operation.

Further, in the above-described embodiment, an electronic camera is described as an example, but the present invention is not limited to this, and for example, a camera using a silver salt film or an electronic video signal can be used. It can be easily applied to a video camera or the like for recording on a recording medium such as a magnetic tape.

By the way, in the above-described embodiment, the zoom lens barrel 1 to which the zoom lens barrel 1 is applied has a zoom optical system in which the group 1 lens 22 is driven forward and backward between the wide end position and the tele end position. Illustrates what is However, the present invention is not limited to this, and it can be applied to, for example, a zoom lens barrel having a configuration in which the group 1 lens does not advance or retreat between the wide end and the tele end.

That is, in a zoom lens barrel having a configuration in which the 1st group lens does not advance or retreat between the wide end and the tele end, the cam groove for driving the 1st group lens frame arranged in the zoom cam frame is the wide end. Between the telephoto ends, a cam groove having a shape orthogonal to the optical axis of the lens is formed. Therefore, even if an external force acts on the group 1 lens frame from the subject side, the group 1 lens frame itself does not move in the optical axis direction due to the pressure angle of the cam groove.

However, when the stepping motor is being driven by the zoom when an external force is applied, the applied external force resists the friction generated between the cam groove of the zoom cam frame and the cam pin engaged with the cam groove. Due to an increase in force or the like, the zoom cam frame may not rotate smoothly, and the stepping motor may step out. Then, due to the stepping motor step-out, the zoom cam frame deviates greatly from the zoom position instructed by the system controller, and the zoom position of the 2nd group lens, the 3rd group lens, the auxiliary frame, etc. becomes deviated. ..

[0132] When such a deviation occurs, a means for detecting the deviation of the zoom position is provided as in the above-described embodiment so as to recognize that an abnormality due to an external force has occurred, and the zoom cam. After correcting the position by moving the frame so that it becomes the wide end position, the subsequent shooting process may be executed. In this way, even if the zoom lens barrel has a configuration in which the group 1 lens does not advance or retreat between the wide end and the tele end, it is possible to easily eliminate the obstacle due to the displacement of the group 1 lens frame.

By the way, in recent years, various electronic cameras that can handle moving images have been proposed, and various electronic cameras have been put into practical use.

That is, even in the electronic camera shown in the above-described embodiment, it is easy to configure the electronic camera so that moving image data can be generated and recorded. Normally, when recording moving image data, it is usual to record audio data together at the same time. Therefore, during the recording operation of the moving image data, that is, during the shooting operation of the moving image, noise components that cause deterioration of the image quality of the acquired moving image, noise mixed in the audio data recorded at the same time as the moving image data, etc. It is necessary to suppress noise components as much as possible. In the case of an electronic camera, these noise components are caused by, for example, vibration generated by a drive motor, drive noise, or the like.

Therefore, when the electronic camera of the above-described embodiment is configured to be capable of generating and recording moving image data, the drive control of the zoom motor 26 may be as follows.

[0136] As described above, if the driving sound of the zoom motor or the like is loud due to the zoom driving or the like during the execution of the moving image shooting operation, this will be recorded as noise. On the other hand, even if some driving noise of the zoom motor due to the zoom drive is generated during the still image shooting operation, there is no problem in the shooting itself.

Therefore, when the still image shooting operation is performed, the zoom motor is driven and controlled by, for example, two-phase excitation (first drive mode), and when the moving image shooting operation is performed, the zoom motor is operated more than the first drive mode. Drive control is performed by driving control that operates at a low current, for example, 1-2 phase excitation or microstep drive (second drive mode).

By performing such drive control, it is possible to reduce noise and vibration during the moving image shooting operation, so that the image quality of the acquired moving image data is deteriorated and the moving image data is recorded at the same time. It is possible to prevent noise components such as noise from being included in the voice data. Further, during the still image shooting operation, the zoom drive can be performed more reliably and quickly, so that good operability can be ensured.

[0139] Separately from this, the zoom motor may be driven and controlled by, for example, 1-2 phase excitation (first drive mode) when performing a still image photographing operation. In this case, when performing the moving image shooting operation, the drive control for operating the zoom motor with a current lower than that of the first drive mode, that is, the microstep drive (second drive mode) may be used.

[0140] In this way, it is possible to reduce noise and vibration more than in the above case.

【０１４１】

According to the present invention, as described above, the drive control for moving the lens mirror frame more quickly during the storage operation (shooting end processing) for moving the lens mirror frame into the camera body. In addition to performing the drive control that can move the lens mirror frame with higher accuracy during the zoom operation (zoom processing) during the shooting operation, efficient drive control according to each drive condition is performed. Therefore, it is possible to provide a lens device that can contribute to the reduction of the power consumption of the entire device.

Further, according to the present invention, it is consumed by optimally performing drive control of a stepping motor as a drive source for moving a lens mirror frame in an electronic camera or the like according to a plurality of drive methods (drive modes). It is possible to provide an electronic camera that can realize a reduction in power consumption and contribute to a better usability and an improvement in operability.

Further, according to the present invention, in an electronic camera capable of generating and recording moving image data and still image data, a zoom operation during execution of a moving image shooting operation and a zoom operation during execution of a still image shooting operation are performed. Since the drive control is performed in different drive modes, it is possible to suppress the simultaneous recording of noise components such as the drive sound of the motor and the like accompanying the zoom drive during the execution of the moving image shooting operation, and also to vibrate. It is possible to provide an electronic camera capable of recording good moving image data while suppressing the problem, and further comfortably performing a shooting recording operation of still image data.

[Simple explanation of drawings]

FIG. 1 is a block configuration diagram showing a configuration of a camera according to an embodiment of the present invention.

2 is a perspective view showing a zoom lens barrel of the camera shown in FIG. 1. FIG.

FIG. 3 is a conceptual diagram showing the relationship between the extension positions of each lens group when the zoom lens barrel in the camera shown in FIG. 1 reaches the tele end position from the retracted position through the wide end position (shooting preparation position).

FIG. 4 is a diagram showing output signals of PR (A) 31 and PR (B) 32 in the camera shown in FIG. 1, a region (zone) in a zoom section that can be detected by the output signals, and a rotation angle of a zoom cam frame 27.

5 is a flowchart showing a sequence of shooting operations of the camera shown in FIG. 1. FIG.

6 is a flowchart showing a sequence of shooting end processing of the camera shown in FIG. 1. FIG.

FIG. 7 is a flowchart showing a zoom processing subroutine called in the shooting sequence of FIG.

8 is a flowchart showing an exception handling subroutine called in the shooting sequence of FIG. 5 or the zoom process of FIG. 7. FIG.

FIG. 9 is a schematic view showing a state in which an external force acts on the front lens mirror frame during shooting with a conventional camera.

FIG. 10 is a diagram illustrating one-phase excitation drive in a conventional general stepping motor.

FIG. 11 is a diagram illustrating a two-phase excitation drive in a conventional general stepping motor.

FIG. 12 is a diagram illustrating 1-2 phase excitation drive in a conventional general stepping motor.

[Explanation of symbols]

1 ...... Zoom lens lens barrel 2 ...... Imager (electronic imaging means) 3 ...... Imaging circuit (electronic imaging means) 4 ...... A / D conversion circuit 5 ...... Zoom motor drive circuit 6 ...... Focus motor drive circuit 7 ...... Focusing circuit 8 ...... System controller (drive control means, control means, calculation means, correction means) 9 ...... Zoom up switch (SW) 10 ...... Zoom down switch (SW) 11 ...... Release switch (SW) ) 12 ...... Power switch (SW) 13 ...... Image processing circuit (image processing means) 14 ...... Memory 15 ...... Display circuit 16 ...... LCD (display means) 17 ...... I / F (interface; recording means) 18 ...... Recording medium 19 ...... Compression / expansion circuit 21 ...... 1-group lens frame 22 ...... 1-group lens (shooting optical system) 23 ...... 2-group lens (shooting optical system) 24 ...... 3-group lens (shooting optical system) 25 ...... 4 group lens (photographing optical system, focus lens) 26 ...... Zoom motor (stepping motor) 27 ...... Zoom cam frame (transmission means) 27a ...... Cam groove (transmission means) 28 ...... Auxiliary frame 29 ...... Focus Motor 30 ...... Fixed frame 30a ...... Protruding arm 31 ...... PR (A) (photo reflector; position detecting means) 32 ...... PR (B) (photo reflector; position detecting means) 41 ...... power supply circuit 42 ...... battery

Continuation of front page (56) References Japanese Patent Application Laid-Open No. 63-167337 (JP, A) Japanese Patent Application Laid-Open No. 4-19606 (JP, A) Japanese Patent Application Laid-Open No. 5-45568 (JP, A) Japanese Patent Application Laid-Open No. 4-180008 (JP, A) , A) Japanese Patent Application Laid-Open No. 7-5548 (JP, A)