JPH03108883A - Pyroelectric infrared ray detector - Google Patents

Abstract

PURPOSE:To execute both high speed response and highly accurate temperature detection with one device by devising the device such that a high speed optical chopper is employed to quicken the scanning speed thereby recognizing the position and movement of an object roughly and the speed of the optical chopper is decreased to apply highly accurate temperature detection after the detection of the object. CONSTITUTION:An infrared ray 2 intermitted by an optical chopper 1 formed by providing lots of radial slits to a disk radiates a pyroelectric element array 3 in a line and an AC electromotive force is generated in each pyroelectric element 3. The generated signal is processed by a band pass filter and switched sequentially by an analog multiplexer 6 to apply signal scanning in the arrangement direction of the pyroelectric element array 3. A variable speed motor is employed for a motor driving the optical chopper 1 and a motor driving a moving mirror 8. Then in the case of high speed scanning, the chopper 1 and the mirror 8 are both driven at a high speed and in the case of highly accurate temperature detection, they are both driven at a low speed.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a device for detecting the position and temperature information of an object using a pyroelectric infrared sensor. Crime prevention/disaster prevention/H
For the purpose of A (home automation), devices that use infrared sensors to detect the presence and movement of infrared sources have come into use. Infrared sensors include quantum type sensors using compound semiconductors and pyroelectric sensors. There are calorific sensors that use elements, thermistors, etc., and quantum infrared sensors need to be cooled with liquid nitrogen, etc.Calorific infrared sensors are also used for purposes such as crime prevention, disaster prevention, and HA. Pyroelectric sensors have higher sensitivity than other calorific sensors, and are ideal for detecting the position of infrared sources.Currently, however, pyroelectric sensors, used for crime prevention, disaster prevention, HA, etc., determine the presence or absence of infrared sources. The mainstream is single-element or multi-element sensors (in addition, the development of sensors that detect heat sources as two-dimensional information so that they can also read the position information of infrared sources and make advanced judgments is progressing.) Especially for air conditioning. Considering the application to devices, it is necessary to obtain not only position information but also temperature information of the infrared source. The infrared rays 2 interrupted by the optical chopper 1 are irradiated onto a row of pyroelectric element arrays 3, and each pyroelectric element 3 has a period of 6 corresponding to the brightness and darkness of the infrared rays 2. Even if an AC electromotive force with an amplitude is generated, the generated signal is impedance converted 4 and then processed by a band pass filter 5 to improve hs/N.The output of each element after signal processing is sequentially switched by an analog multiplexer 6. scan in the array direction of the pyroelectric element array 3 (read the signal for one column when the optical chopper 1 is closed Read the signal for one column when the optical chopper 1 is open, and start from the open signal to the closed signal) Even if the infrared intensity of one row is obtained by subtracting the signal, one row is read in one cycle of opening and closing of the optical chopper.The optical axis is moved by the movable mirror 8 installed in front of the lens 7.
Problems that the invention aims to solve even though two-dimensional infrared information is obtained by repeating the process of reading the next column of information It is not possible to follow faster temperature changes or movement of infrared sources.

The cycle and temperature resolution of this optical chopper are almost inversely proportional; if fast response is required, temperature detection accuracy will deteriorate, and if temperature detection accuracy is required, response speed will be slow.

Tokorogeki In applications such as crime prevention, disaster prevention, and HA, a speed close to that of a video signal (30 frames per second) is required to deal with objects moving at ζ, and temperature resolution It is required to distinguish between people and objects.
Although it is extremely difficult to produce a sensor that satisfies both of these requirements, it is currently difficult to create a sensor that meets both of these requirements. However, the system becomes larger and more expensive.a The present invention is a focusing system that can perform high-speed position detection against changes and movements of the infrared source and highly accurate temperature detection of the infrared source with a single unit. It is an object of the present invention to provide a pyroelectric infrared detection device that obtains a two-dimensional distribution of infrared rays using at least one row or more of pyroelectric element arrays. The above problem is solved by making it possible to set the speed of the scanning mechanism in at least two stages or more, and to change the frequency characteristics of the filter used for signal processing in accordance with the frequency change of the output signal due to the speed change. As mentioned above, the response time is equivalent to the period of the optical chopper.Usually, by increasing the speed of the optical chopper and increasing the scanning speed, the position and movement of the object can be roughly known, and after detecting the object, the response time is equivalent to the period of the optical chopper. The optical chopper is set at a low speed to perform high-precision temperature detection.By providing at least two scanning speeds in this way, it is possible to achieve both high-speed response and high-precision temperature detection with one device. r,, A pyroelectric infrared detector that can change the scanning speed by using a filter whose frequency characteristics can follow changes in signal frequency when changing the scanning speed. The present invention will be described in more detail below.Example 1 A general view of an embodiment of the pyroelectric infrared detection device of the present invention is shown in Fig.1. Infrared rays 2 are interrupted by an optical chopper 1, which has a large number of radial slits in a disk, and irradiate one row of pyroelectric element arrays 3.Although no alternating current electromotive force is generated in each pyroelectric element 3, the generated signal is an impedance. After conversion 4, the signal is processed by a bandpass filter consisting of a switched capacitor filter 9, and is sequentially switched by an analog multiplexer 6 to scan the signal in the arrangement direction of the pyroelectric element array 3. Even when performing optical scanning in the vertical direction of the pyroelectric element array by 8, a variable speed motor is used for the motor that drives the optical chopper 1 and the motor that drives the movable mirror 8 (for high-speed scanning, the chopper 1
, both mirrors 8 are driven at high speed L. Both are driven at low speed for high precision temperature detection. Switched capacitor filter 9 used for signal processing.
For external devices, the center frequency can be changed simply by changing the supplied clock frequency without changing the constants of the parts.It is easy to synchronize with the drive motor and follow the signal frequency. Let's think about the case of detecting a human body and measuring its temperature using a high-speed scan.If you use high-speed scanning to detect where an object around 36 degrees Celsius is and whether it is moving, the movement of the object becomes very small. Sometimes, the temperature of the object is measured using low-speed scanning. If the object is determined to be a human body based on its temperature and shape, the measured temperature is used as body temperature data to provide more comfortable air conditioning. If the object is determined to be other than a human body, the object is ignored, but scanning at a low speed may take too much time to scan one screen.Slowly scanning only the front and back of the target object's position can shorten the measurement time. Embodiment 2 While performing high-speed scanning, time can also be shortened by performing low-speed scanning only when approaching the object. Embodiment 2 An embodiment with another configuration is shown in FIG.

Electrodes 22 are provided on both sides of the pyroelectric thin film 21. 23 is formed to constitute each pyroelectric element.The pyroelectric element plates are arranged two-dimensionally.The pyroelectric elements in the horizontal direction are wired alternately between adjacent pyroelectric elements according to the pattern of electrodes 2423, and arranged in rows. Even if the pyroelectric elements are arranged in series, the pyroelectric element array is arranged in a plurality of rows in the vertical direction to form a two-dimensional pyroelectric element array. By moving the array, the infrared rays 26 passed through the lens 25 and were focused on the pyroelectric element array, and the voltage generated between the electrodes 27 and 28 at both ends of each column was output and connected to the signal processing circuit. Here, the pyroelectric elements in the horizontal direction are wired so that adjacent ones create a counter electromotive force. A signal is obtained by subtracting the downward peak value from . This signal is omitted in Figure 2, but as in Example 1. After impedance conversion, the signal is processed by a bandpass filter consisting of a switched capacitor filter. Even if an analog multiplexer is used to scan signals in the array direction of the pyroelectric element array, the slits are driven at high speed for high-speed scanning and at low speed for high-precision temperature measurement. The slit 24 in this configuration (Friend Example 1)
This device has both the role of intermittent infrared rays of the optical chopper 1 and the role of optically scanning the movable mirror 8.The advantage is that the trouble of synchronizing the optical chopper 1 and the movable mirror 8 is eliminated. Of course, it is possible to simplify the device by combining two mechanical parts into one device (1. miniaturization and lower cost), but in Example 2, the force using a two-dimensional vertical and horizontal pyroelectric element array (focusing on concentric circles) is possible. Although the same effect can be obtained by arranging electric elements and using a disc-shaped slit, the present invention provides a pyroelectric infrared detection device that obtains a two-dimensional distribution, in which the speed setting of the two-dimensional scanning mechanism is set in at least two stages. This is a pyroelectric infrared detection device that can set the above settings and change the frequency characteristics of the filter used for signal processing according to the frequency change of the output signal due to the speed change. It is possible to create a pyroelectric infrared detection device that can perform both accurate position detection and highly accurate temperature detection of an infrared source with a single device.

[Brief explanation of drawings]

FIGS. 1 and 2 are conceptual side views showing the main parts of a pyroelectric infrared detection device according to an embodiment of the present invention, and FIG. 3 is a conceptual side view showing the main parts of a conventional pyroelectric infrared detection device. Amo 1... Choppe 3... Pyroelectric element array, 5...
・Band pass filter, 8... Movable mirror 9.
...Switched capacitor filter 21...Pyroelectric filter 24...Slit

Claims (3)

[Claims] (1) In a pyroelectric infrared detection device that obtains a two-dimensional distribution of infrared rays using at least one row or more of pyroelectric element arrays, the speed setting of the two-dimensional scanning mechanism can be set in at least two or more stages, and as the speed changes A pyroelectric infrared detection device characterized by changing the frequency characteristics of a filter used for signal processing according to changes in the frequency of an output signal. (2) A switched capacitor filter is used for output signal processing of the pyroelectric element array, and the frequency characteristics of the signal processing are changed according to the frequency of the output signal when the scanning speed is changed. pyroelectric infrared detection device. (3) The pyroelectric element array is arranged two-dimensionally, each pyroelectric element making up one row is electrically connected in series, and adjacent pyroelectric elements are wired so that they create a counter electromotive force, 2. The pyroelectric infrared detection device according to claim 1, wherein the slit sequentially scans the infrared images irradiated to each pyroelectric element by moving in the column direction on the pyroelectric element array.