Pyroelectric infrared rays detector

Description: TECHNICAL FIELD [Detailed description of the invention]

Industrial application field The present invention relates to a pyroelectric infrared detector used for detecting the position of an object and the intensity distribution of infrared rays. Conventional technology In recent years, pyroelectric infrared detectors have been used by intruders to detect infrared rays from the human body and flames for crime prevention and disaster prevention purposes such as detection and fire detection. As the infrared sensor, there are a quantum type sensor using a compound semiconductor and a thermal type sensor using a pyroelectric element or a thermistor. Since the quantum infrared sensor needs to be cooled with liquid nitrogen or the like, the thermal infrared sensor is used for the purpose of crime prevention / disaster prevention. In particular, the pyroelectric type infrared sensor has higher sensitivity than other thermal type infrared sensors, and is most suitable for the position detection device of the infrared source. The conventional pyroelectric infrared detector will be described below. As shown in FIG. 6, in the method using a pyroelectric type point sensor, the incident infrared rays 1 are collected on the point sensor 13 through the lens 2, and the optical axis is driven by a movable mirror 14 that can drive the two axes vertically and horizontally. Scanning in two dimensions. As shown in Fig. 7, in the method using a pyroelectric type array sensor arranged in one dimension, the incident infrared rays 1 are collected on the one-dimensional array sensor 15 through the lens 2, and the optical axis thereof is one axis. The driveable movable mirror 14 scans the array of the one-dimensional array sensors 15 in the direction perpendicular to the array. The output of the one-dimensional array sensor 15 is sequentially electrically scanned. As shown in FIG. 8, in the method using a pyroelectric type array sensor arranged vertically and horizontally two-dimensionally, the incident infrared rays 1 are collected on the two-dimensional array sensor 16 through the lens 2 and electrically in both the vertical and horizontal directions. I'm scanning. In either case, in order to obtain the dielectric strength of the infrared distribution, a chopper 17 is provided in the optical path, and an output is obtained as the amplitude of the AC signal generated when the infrared ray 1 is intermittent. Problems to be solved by the invention However, in the above-mentioned conventional configuration, in the method using the point sensor, the mechanism for driving the movable mirror in two axes is complicated, so that there is a problem that it becomes a large and expensive device and the sensitivity of the pyroelectric sensor is infrared. Since it is proportional to the illumination time, the sensitivity per area becomes small in the method of scanning the entire area with one element, so if you try to obtain a certain degree of sensitivity, it takes a long time to scan the entire area. Had. In the method using a one-dimensional array sensor, since a movable mirror is provided on the front surface of the lens, there is a problem that it becomes a large device and a configuration in which a movable mirror is provided between the lens and the one-dimensional array sensor is conceivable. There is a problem that the space for providing the lens is limited and the viewing angle is limited with one lens. In the method using a two-dimensional array sensor, there is a problem that the viewing angle is limited by one lens, and as the number of pyroelectric elements increases, the wiring for extracting signals from each pyroelectric element becomes complicated, and the signal There is a problem that the number of processing circuits increases proportionally and becomes complicated. Further, in order to accurately determine the intensity of infrared rays with a pyroelectric type infrared sensor, it is necessary to interrupt the infrared rays by a chopper and obtain the difference between when the chopper is open and when the chopper is closed. Since it requires a chopper and a mechanism for rotating it, it has a problem that it becomes a larger device. The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a small pyroelectric infrared detection device having a wide viewing angle with a simple mechanism. Means to solve problems In order to achieve this object, the charcoal-type infrared detector of the present invention comprises an array sensor composed of a plurality of charcoal elements, at least one lens, a cylinder having a fixed lens, and a signal processing means. In the electric infrared detection device, the array sensor is composed of a plurality of pixels arranged in at least one row in the central axis direction in the vicinity of the central axis in the cylinder, and the lens is a window provided on the circumference of the cylinder. An infrared image from the outside of the cylinder is imaged on the array sensor, and the cylinder rotates at a constant speed together with the lens about the central axis, so that the field of view received by the array sensor is sequentially formed. A pulsed signal that is scanned in the circumferential direction and the voltage generated in the array sensor is subjected to impedance conversion and bandpass filtering by the signal processing means, and is generated when the field of view of the array sensor passes through a heat source. And, the configuration in which the position of the heat source is detected in two dimensions from the rotation angle of the cylinder at the time of receiving the pulsed signal, or the infrared shielding plate maintained at substantially the same temperature as the cylinder is in the immediate vicinity of the cylinder. Further, the array sensor is arranged at a position that shields the field of view for a certain period of time, and the voltage generated in the array sensor is subjected to impedance conversion and differentiation processing by the signal processing means, and the infrared shielding plate is used as the field of view. A configuration in which an infrared intensity distribution in the circumferential direction is obtained as a time-series signal based on a voltage of time, or a first slit group and a second slit group are provided in place of the shielding plate, and the first slit group is described above. The second slit group is arranged on the curved surface along the cylinder at equal intervals on the outer or inner side adjacent to the cylinder over the entire field to be scanned, and the second slit group is provided in the window portion provided with the sensor of the cylinder. It is arranged at equal intervals with the slit group, rotates together with the cylinder, interrupts the incident infrared rays by overlapping with the first slit group, and the voltage generated in the array sensor is impedance-converted by the signal processing means. It has a configuration in which the infrared intensity distribution in the circumferential direction is obtained as a time-series signal with reference to the voltage when the infrared rays are shielded by the first and second slit groups. Action By rotating the lens together with the cylinder and sequentially scanning in the circumferential direction of the focal array sensor at a constant speed, infrared rays are continuously emitted in an extremely wide field of view that cannot be covered by the viewing angle of one fixed lens. It is possible to perform detection. Further, the above-mentioned scanning of the field of view can be realized only by a simple mechanism for rotating the cylinder, and the device can be made extremely small in size, which is the size of the cylinder whose radius is the focal point of the lens. Further, by sequentially scanning the field of view at a constant speed and performing signal processing such as bandpass filter processing, it is possible to remove disturbance from the surroundings and detect the position of the infrared source with high accuracy. Further, by providing a plurality of lenses and dividing the field of view in the vertical direction by time, the number of pyroelectric elements required for the array sensor can be reduced. Furthermore, infrared rays are interrupted by a cylindrical slit that rotates with the lens and a slit with the same pitch adjacent to it, and the function of a chopper, which was conventionally large with multiple mechanisms, is the size of a cylinder whose radius is the focal point of the lens. It can be stored in the lens, and it is possible to measure the intensity distribution of infrared rays while achieving extremely small size. Furthermore, by arranging the infrared shield plate, which is a standard temperature substance, on the curved surface closest to the cylinder, in an extremely small device of the size of a cylinder whose radius is approximately the focal point of the lens, the infrared rays from the infrared shield plate are at temperature. By making the structure in which the infrared rays are periodically incident in a time shorter than the constant, it is possible to measure the standard temperature substance and then obtain the infrared intensity distribution with the standard temperature substance as a reference. Example (Example 1) Hereinafter, the first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the incident infrared rays 1 are collected through the lenses 2a and 2b on the array sensor 3 in which one or more rows of pyroelectric infrared sensors are arranged in the vertical direction. The lenses 2a and 2b are arranged on the outer peripheral surface of the cylinder 4 that rotates about the vertical center line of the array sensor 3, and the rotation of the cylinder 4 causes the lenses 2a and 2b to rotate and the array sensor. The field of view in the circumferential direction of 3 is sequentially scanned. At this time, the position information of the heat source and the temperature information can be obtained from the time change of the electromotive force generated in the array sensor 3. A simple mechanism that rotates the lenses 2a and 2b by one axis, that is, a cylinder 4 whose optical system and the volume occupied by the mechanical system have the focal length of the lenses 2a and 2b as the radius and a mechanism that rotates it, is a conventional point sensor. In addition, it is possible to make the device simpler and smaller than the method using a movable mirror. Further, even if a lens having a narrow viewing angle is used for the lenses 2a and 2b, the viewing angles in both directions can be sufficiently obtained because the lenses 2a and 2b themselves are rotated. In the embodiment of FIG. 1, a lens 2a and a lens 2b are provided on the front and back of the cylinder 4, respectively, and the vertical angle of the lens is set so that the lens 2a has an upward field of view and the lens 2b has a downward field of view. Half of the circumference of the cylinder 4 is divided into upper and lower fields of view. By doing so, the vertical viewing angle required for one lens can be halved, and the number of pyroelectric elements of the array sensor 3 can be halved. In the case of Fig. 1, since the array sensor 3 has 3 elements and the lenses 2a and 2b are 2, the vertical direction is divided into 6 areas, and a 60-degree field of view can be obtained even if the field of view is 10 degrees per area. Will be. Further, if the number of lenses to be arranged is increased to be divided into three or more in the vertical direction, a more effective effect can be obtained. The electromotive force of the angular pyroelectric element constituting the array sensor 3 is impedance-converted by the FET, and then signal processing is performed. When detecting the position of a heat source such as the human body, after signal processing is performed by a bandpass filter to remove disturbance from the surroundings, the pulsed signal generated when the optical axes of lenses 2a and 2b pass through the heat source is transmitted. To detect. The position of the heat source in the circumferential direction is obtained from the time when the pulse is generated. (Example 2) When detecting the position of a heat source having an area smaller than one pixel of the array sensor, the ratio of the image of the heat source to the area of one pixel becomes small, so that the detection sensitivity of the heat source decreases. On the other hand, since this problem does not occur for a heat source having a large area, it becomes difficult to detect only a small heat source. A second embodiment of the present invention corresponding to this problem will be described below with reference to the drawings. As shown in FIG. 2, the configuration different from that of FIG. 1 is that each pyroelectric element of the array sensor 3 is composed of a front electrode 6 and a back electrode 7 provided on both sides of the pyroelectric plate 5. The point is that a plurality of pyroelectric elements in which pixels are formed horizontally in two examples are wired in series by electrodes 6 and 7 on both sides. The wiring of the pyroelectric element is performed alternately on the left and right, and the pyroelectric electron in the left column and the pyroelectric element in the right column have counter electromotive forces. Here, consider a case where the size of the heat source to be detected after imaging is substantially equal to the size of the pyroelectric element. When the image of the heat source moves from left to right due to lens scanning, infrared rays 1 first irradiate the pyroelectric element with positive polarity, and positive charges are accumulated. Next, infrared rays 1 are incident on the pyroelectric element of negative polarity, the signal is attenuated, and the signal level returns to the original level. Also, in the case of a heat source with a large width, there is a time when infrared rays 1 from the heat source are incident on both the left column and the right column, and the signal during this time is canceled, so it occurs in the case of the small heat source described above. A pulse signal with a wide width can be obtained with an electromotive force that is almost the same as that of a pulse. As described above, the height of the pulse does not depend much on the size of the heat source, which is advantageous when detecting a small heat source. Further, information on the size of the heat source can be obtained from the information on the pulse width. When N × N elements are used as a conventional two-dimensional array sensor, N × N signal processing circuits and N × N mounting wiring are required. However, by using a single row of array sensors, Only N circuits and N wires are required, the signal processing circuit can be miniaturized, and mounting with a sensor can be easily realized. (Example 3) As a method of obtaining infrared distribution information, in the conventional example, infrared rays are intermittently used by a chopper, and the intensity of infrared rays is obtained from the amplitude of the output AC signal, so that the apparatus becomes large. A third embodiment of the present invention corresponding to this problem will be described below with reference to the drawings. As shown in FIG. 3, the difference from the configuration of FIG. 1 is that the shielding plates 8 that limit the field of view of the array sensor 3 are provided on the left and right sides of the array sensor 3, and the cylinder 4 and the shielding plate 8 have the same temperature. This is the standard temperature. When the lens 2 is completely turned sideways, only infrared rays from the standard temperature material are incident on the array sensor 3. The signal of the array sensor 3 after the impedance conversion 11 is amplified, and the CR circuit 12 performs pseudo differential processing. On the lower frequency side than the cutoff frequency of the CR circuit 12, the signal is attenuated in the first order with respect to the frequency, so that it becomes a pseudo differential. Since the output of the pyroelectric infrared sensor is obtained integral with respect to the incident infrared energy within a time shorter than the temperature time constant, the relative infrared intensity distribution can be obtained by using a differential signal processing circuit. can get. However, since the obtained output is attenuated after a time of about the temperature time constant of the sensor, it is difficult to accurately obtain the infrared intensity distribution over a long period of time. Therefore, the infrared intensity distribution from the standard temperature substance is obtained after measuring the standard temperature substance by periodically apologizing for the infrared rays from the standard temperature substance in a time shorter than the temperature time constant. be able to. FIG. 4 shows the signal waveforms of each part generated when the lens 2 of this device is rotated. A indicates the intensity of infrared rays 1 incident on the array sensor 3, and the state in which the lens 2 is completely turned sideways and only infrared rays from a standard temperature substance are incident is a, in the field of view of the array sensor 3. The pattern is repeated, in which the state where infrared rays 1 from a certain heat source are incident is b, and the state where infrared rays only infrared rays from a standard temperature substance are incident again is c. B indicates the temperature of the array sensor 3, and the waveform is an integral of the incident infrared rays 1, but it not only rises but also enters an equilibrium state with a thermal time constant determined by heat diffusion from the array sensor 3 to the surroundings. The temperature of the array sensor 3 in the equilibrium state changes periodically according to the distribution of infrared rays around the average temperature. The electromotive force of the array sensor 3 changes in proportion to the temperature change of the array sensor. The output signal when pseudo-differentiation is performed by the CR circuit 12 with respect to this signal is shown in C. The waveform of the output signal C has the same waveform as the incident infrared distribution, but the baseline changes according to the thermal time constant of the array sensor 3 and settles in the equilibrium state. The infrared distribution from each direction can be obtained by using the output voltage in the state a in which only infrared rays from the standard temperature substance are incident as a reference for each cycle. In this method, temperature distribution information can be obtained with almost no change in the configuration of the device, and a small device is possible. (Example 4) A fourth embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 5, the configuration differs from that of FIG. 3 in that a plurality of vertically long slits 9 are provided at equal intervals in the circumferential direction on the outer circumference of the cylinder 4, rotated together with the cylinder 4, and concentric with the cylinder 4. A point is that a slit plate 10 having a plurality of slits at the same intervals as the slits 9 is arranged slightly on the outside. By rotating the cylinder 4, the slit 9 and the slit plate 10 are used to interrupt the incident infrared ray 1, and the intensity of the infrared ray 1 is obtained from the amplitude of the output AC signal. In this method, scanning of the optical axis and interruption of infrared rays are realized by one rotation mechanism, and the mechanism is extremely simple. Since the slit 9 and the slit plate 10 can be provided in the cylinder having the focal length of the lens as the radius or on the outer periphery in the vicinity thereof, the infrared rays can be interrupted without impairing the feature of the small size of the device. In the embodiment, one row of array sensors is used, but the same effect can be obtained with two or more rows of array sensors. Rather, by using two rows of array sensors, the direction that could not be seen in one row while the slit 9 is closed, the so-called blind spot, can be compensated by another row. Further, although the slit plate 10 is provided on the outer circumference of the cylinder 4, it can also be provided on the inner circumference. Effect of the invention As is clear from the description of the above examples, the present invention comprises an array sensor in which one or more rows of pyroelectric infrared sensors are arranged in the vertical direction, and a lens for forming an image of incident infrared rays on the array sensor. The lens is rotated around the vertical center line of the array sensor, and a plurality of pyroelectric elements in which one pixel of the array sensor is formed in two horizontal rows are wired in series by double-sided electrodes. Shielding plates are provided on both sides so that the temperature of the cylinder and the shielding plate are the same, and a plurality of vertically long slits are provided on the outer circumference of the cylinder at equal intervals in the circumferential direction. By arranging the slit plate on which the slits are formed on the curved surface along the cylinder on the outside or inside adjacent to the cylinder, the infrared intensity distribution can be measured accurately with a wide viewing angle, and the mechanism is simple and compact. It is possible to realize an excellent pyroelectric infrared detection device that can be converted into an excellent one.

[Simple explanation of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a pyroelectric infrared detector according to a first embodiment of the present invention, and FIG. 2 is an array sensor of a pyroelectric infrared detector according to a second embodiment of the present invention. A schematic configuration diagram showing an electrode configuration, FIG. 3 is a top view showing a schematic configuration of a pyroelectric infrared detection device according to an embodiment of the present invention, and FIG. 4 is an infrared intensity during operation of the embodiment and a temperature of an array sensor. And a waveform diagram showing an output signal, FIG. 5 is a top view showing a schematic configuration of a pyroelectric infrared detector according to a fourth embodiment of the present invention, and FIGS. 6, 7, and 8 are conventional pyroelectric detectors. It is a perspective view which shows the schematic structure of the electric infrared ray detection device. 1 ...... infrared, 2,2a, 2b ...... lens, 3 ...... array sensor, 4 ...... cylinder, 5 ...... pyroelectric Body plate, 6 ... front electrode, 7 ... back electrode, 8 ... shielding plate, 9 ... slit, 10 ... slit Board.