JPH02285223A - Signal processing for pyroelectric type infrared detector - Google Patents

Abstract

PURPOSE:To reduce variations in sensitivity of elements generated depending on a relationship between a layout of elements and a light chopper while simplifying a signal processing method by performing analog computation of a difference between positive and negative signals o be obtained when the light chopper is opened or closed. CONSTITUTION:A signal processing system is made up of a light chopper 11, an infrared lens 12, a multi-element infrared detector 13, a preamplifier 14, a sampling/holding (S/H) section 16, a P-n computing section 18, a S/H timing section 20 and the like. Incident infrared rays modulated with the light chopper 11 form an image on the infrared detector 13 with the infrared lens 12 to be converted into an electrical signal, which provides an original signal (b) corresponding to a light chopper opening/closing signal (a) with the preamplifier 14 and sampled and held by an S/H timing pulse (c) with an S/H section 16 to obtain a signal (d). Furthermore, with a P-n computing section 18, when the original signal (b) not sampled/held is subtracted from the signal (d) after the sampling and holding thereof, a signal (e) is obtained. Thus, a p-n computation is accomplished in an analog manner.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a signal processing method for a pyroelectric infrared detector that converts infrared rays emitted from an object into electrical signals.

2. Prior Art A conventional signal processing method for a multi-element pyroelectric infrared detector is to convert the signal generated by opening and closing of an optical chopper that modulates incident infrared rays into an A/D converter, and then digitally convert the signal generated by the opening and closing of an optical chopper.
A pn calculation is performed at a certain timing after inputting the signal and the n signal generated at the time of closing into the digital memory. For example, a configuration described in Japanese Unexamined Patent Publication No. 56-91589 is known.

Below, the configuration will be briefly explained.
3 is a multi-element infrared detector, 12 is an infrared lens, 11 is an optical chopper, 14 is a preamplifier, 36 is an A/D conversion section,
37 is a part of p memory, 38 is a part of //in memory, 39 is a pn calculation section, 40 is a D/A conversion section, and 2o is a timing generation section.

The incident infrared rays modulated by the optical chopper 11, which opens and closes according to the timing signal from the timing generator 20, is imaged by the infrared lens 12 on the multi-element infrared detector 13, converted into an electrical signal, and amplified by the preamplifier 14. /
It is added to the D converter 36. The A/D converter 36 converts the positive signal (hereinafter referred to as p signal) into a digital signal according to the opening/closing reference signal from the timing generating section 20 and the positive signal (hereinafter referred to as p signal) obtained according to the chopper opening/closing reference signal to the p memory part 37 as a true signal ( The n signal (hereinafter referred to as n signal) is stored in the n memory part 38, subjected to subtraction processing in the p-n calculation section 39, and then converted into an analog signal by the D/A conversion section 40 again.

Problems to be Solved by the Invention However, conventional signal processing methods for multi-element infrared detectors are difficult to process when processing large-capacity signals such as planar sensors with a pixel count of 128 x 12B or 256 x 256. Although this is an effective means, there is a problem that the peripheral processing section becomes large and complicated when the number of pixels is about N=2 to 16.

The present invention provides a signal processing method suitable for a multi-element pyroelectric infrared detector with N=2 to 16 or so, and a first object thereof is to simplify the signal processing method. The second purpose is to reduce variations in sensitivity of each element caused by the relationship between the arrangement of the elements and the optical chopper. The third purpose is to reduce variations in sensitivity of each element caused by the relationship between the supporting method of each element and the optical chopper.

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 is such that the difference between the positive signal and the negative signal obtained when the optical chopper is opened and closed is calculated in an analog manner.

According to the second and third aspects of the present invention, the difference between the signal obtained when the optical chopper is opened and closed is sampled and held, and the signal that is not sampled and held is calculated.

According to the fourth aspect of the invention, the difference between a positive peak hold signal and a negative bottom hold signal obtained when the optical chopper is opened and closed is calculated.

In the invention according to claims 1 to 3, the difference between the positive signal and the negative signal obtained when the optical choke bar is opened and closed is calculated in an analog manner, so that the calculation process is very simple.

In the invention according to claim 4, when the n signal is generated by opening and closing the optical chopper, the maximum value is detected by the peak hold method, and when the n signal is detected, the minimum value is detected by the bottom hold method, and the difference between the two is calculated. It is possible to reduce variations in sensitivity of each element caused by the relationship between the arrangement of the elements and the optical chopper or the relationship between the supporting method of each element and the optical chopper.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a signal processing method of a multi-element infrared detector according to a first embodiment of the present invention. In FIG. 1, 11 is an optical chopper, 12 is an infrared lens, 13 is a multi-element infrared detector, 14 is a preamplifier, 16 is a sampling hold (hereinafter referred to as S/H) section, and 18 is a pn calculation section. , 20 is an S/H';' timing section. FIGS. 2 and 3 show signal waveforms at each part.

The incident infrared rays modulated by the optical chopper 11 are imaged by the infrared lens 12 on the multi-element infrared detector 13 and converted into electrical signals. Therefore, S/H section 16
S/H is performed using the S/H timing pulse C, and the signal d
By subtracting the original signal S which is not used from the signal d after S/H in the p-n calculation unit 18, a signal e is obtained, and p
-n operation can be performed.

As is clear from the above explanation, the signal obtained by opening and closing the optical chopper is the p signal when open and the n signal when closed (however, if the subject temperature is lower than the optical chopper temperature, the signal is n when open and the p signal when closed). Therefore, the DC offset is a PP signal of almost zero, but according to this embodiment, the 378 section 16 and the p-n calculation section 18 are analogously used.
By using p-n, signal processing similar to that performed with digital signals can be performed.

Note that the signal waveforms at each part in FIG. 3 are those in which the negative signal is subjected to S/H at the timing of closing the optical chopper, which is the S/H timing, and the same effect as in FIG. 2 can be obtained.

Next, a second embodiment of the present invention will be described.

In Figure 4, the difference from the configuration in Figure 1 is 378 part 1.
6, a peak hold section 23 and a bottom hold section 24 are provided to perform pn calculation processing.

Further, FIG. 5 shows signal waveforms at each part.

The operation of the above configuration will be explained below.

The incident infrared rays modulated by the optical chopper 11 are imaged by the infrared lens 12 on the multi-element infrared detector 13 and converted into electrical signals. , an original signal consisting of n signals, a peak hold section 23 and a bottom hold section 24.
It will be supplied in parts. When the peak hold section 23 and the bottom hold section 24 process the n signal and the n signal, respectively, at the timing of the P/H pulse "and B/H pulse h" shown in FIG. 5, the peak hold signal g and the bottom hold signal l are processed. Further, when the bottom hold signal i is subtracted from the peak hold signal g in the p-n calculation unit 27, p-
A signal l after n is obtained and pn calculation can be performed in an analog manner.

Compared to the embodiment of FIG. 1, the embodiment of FIG. 4 can correct variations in sensitivity of each element as shown below. When chopping the planar sensor 32 in the chopper scanning direction like the 4×4 element shown in FIG.
When the waveform of the preamplified signal of each element of the l-S 14 is based on the optical chopper opening/closing reference signal a, there is a difference in the rising edge of the signal as shown in FIG. In the method using the optical chopper opening/closing reference signal C, there is a difference in the S/H level at the S/H timing based on the optical chopper opening/closing reference signal C, and there is a difference in the signal even when viewing the same subject, but this problem is solved in the embodiment shown in FIG. Does not occur.

Furthermore, the embodiment shown in FIG. 4 can compensate for variations in sensitivity caused by the method of supporting the element. This situation will be explained using FIGS. 8 and 9.

FIG. 8 shows a configuration in which 2×2 elements are supported in a suspended state, and the figure (al shows a plan view, and (b+ shows a cross-sectional side view).

In the figure, pyroelectric infrared detecting elements 81 to S4 are mounted and supported within the hollow portion 35 of the support base 34 on the substrate 36. When chopping in the chopper scanning direction shown by the arrow in Figure 8 (al), the waveform of the signal after amplification in the preamplifier of elements 81 to S4 is based on the optical chopper opening/closing reference signal fat as shown in Figure 9. The state of the left and right heat sinks differs depending on the support method, and the rise of the signal changes when the optical chopper opens and closes. Therefore, in the method using the S/H circuit 16 shown in the embodiment of FIG. 1, the optical chopper opening/closing reference signal a is At the reference S/H timing (C1), there is a difference in the S/H level, and a difference in signals occurs even when viewing the same subject, but this problem does not occur in the embodiment shown in FIG.

In this way, even in the case of elements with configurations as shown in FIGS. 6 and 8, the problem that occurs in FIG. Incidentally, variations in the sensitivity of each element can also be reduced.

In each of the above embodiments, the case where p-n operation is performed is explained, but n-p operation may also be performed (, n signal and n
What is necessary is to essentially calculate the difference between the signals.

Effects of the Invention As described above, the present invention easily performs signal processing on the output of a multi-element pyroelectric infrared detector by calculating the difference between the n signal and the n signal in an analog manner using an S/H circuit. be able to. Furthermore, when the optical chopper is open, the maximum value is detected using the peak hold method when the n signal is generated, and when the n signal is generated when the optical chopper is closed, the minimum value is detected using the bottom hold method and arithmetic processing is performed to determine the arrangement of each element and the optical chopper. It is possible to reduce variations in sensitivity of each element caused by the relationship between the two elements or the relationship between the supporting method of each element and the optical chopper.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the signal processing method of a multi-element infrared detector in the first embodiment of the present invention, FIG. 2 is a signal waveform diagram of each part in the block diagram of FIG. 1, and FIG.
4 is a block diagram showing a signal processing method of a multi-element infrared detector in the second example of the present invention, and FIG.
Figure 6 is a plan view of the 4x4 elements of the infrared detector in the configuration shown in Figure 4. Figure 7 is the output waveform for each element arrangement shown in Figure 6. Figure 8 (at, (bl) is a plan view and a cross-sectional side view of the configuration of the infrared detector in the configuration shown in Figure 4 in the case of a 2 x 2 element array, and Figure 9 is each element arrangement shown in Figure 8. Figure 10 is a block diagram showing a signal processing method of a conventional multi-element infrared detector. 11... Optical chopper, 12... Infrared lens, 13
...Infrared detector, 14...Preamplifier, 16...
・Sampling hold section, 18...pn calculation section,
20... Sampling hold timing section, 23.
...Peak hold part, 24...Bottom hold part,
27...P-N calculation section, timing generation section. 29...

Claims (4)

[Claims] (1) A focusing system characterized in that incident infrared rays are modulated by an optical chopper and made to enter a pyroelectric infrared detector, and the difference between a positive signal and a negative signal generated in response to opening and closing of the optical chopper is calculated in an analog manner. Signal processing method for electric type infrared detector. (2) A signal processing method for a pyroelectric infrared detector according to claim 1, characterized in that the difference between a signal in which the p signal is sampled and held and a signal in which the p signal is not sampled and held is calculated at the opening timing of the optical chopper. (3) A signal processing method for a pyroelectric infrared detector according to claim 1, characterized in that the difference between a signal obtained by sampling and holding the n signal and a signal not obtained by sampling and holding the n signal at the closing timing of the optical chopper is calculated. (4) Pyroelectric infrared detection characterized by calculating the difference between a positive peak hold signal and a negative bottom hold signal generated with respect to the optical chopper opening/closing reference signal in the signal processing method according to claim 1. signal processing method of the device.