JPS63101839A - Heat infrared image pickup camera - Google Patents

Abstract

PURPOSE:To improve a sensitivity characteristic of a pyroelectric infrared detecting element by constituting the titled camera so that a reflecting mirror executes a panning scan in the direction vertical to a linear array, and also, scans stepwise a prescribed scanning angle. CONSTITUTION:The titled camera is provided with a linear array 1 in which plural pyroelectric infrared detecting elements are arranged in one line, an infrared optical system 2, and a reflecting mirror 3 for scanning an infrared image. Also, said camera is constituted so that the reflecting mirror 3 executes a panning scan in the direction vertical to the linear array 1, and scans stepwise a prescribed scanning angle. As a result, a driving state of the reflecting mirror 3 goes to stepwise, the time required for scanning from some instantaneous visual field to the next instantaneous visual field is shortened, and said mirror stops in its instantaneous visual field for a prescribed time. By setting a ratio of its stop time and the movement time to several times or more, a variation quantity of an infrared signal is increased and an output signal of the pyroelectric infrared detecting element can be maximized. Accordingly, the characteristic of the pyroelectric infrared detecting element can be drawn out enough.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is a thermal infrared light beam that can observe two-dimensional temperature distribution without contact and can be used for heat management, temperature control, disaster prevention, etc. in factories. This relates to an imaging camera.

Conventional technology As a conventional thermal infrared imaging camera, Japanese Patent Application Laid-Open No. 59-1537
As described in No. 9, a configuration in which a linear array of pyroelectric infrared detection elements, an infrared optical system, and an infrared image scanning reflector are combined is known.

The conventional thermal infrared imaging camera will be described below with reference to FIG. 4.

In FIG. 4, 21 is a linear array in which a plurality of pyroelectric infrared detection elements are arranged in a row, 22 is an optical lens for infrared light imaging made of germanium, etc., and 23 is a linear array arranged around a rotation axis 24. A reflector that rotates and performs one-dimensional panning scan.
The panning scanning direction is perpendicular to the arrangement direction of the IJ near 7 rays 21.

25 indicates the field of view to be imaged.

Next, the operation of the above conventional example will be explained.

Now, considering the state where the reflecting mirror 23 is stationary at the position shown in the figure, a two-dimensional image from the field of view 25 is incident on the reflecting mirror 23,
The light passes through the optical lens 22 and enters the pyroelectric infrared detection element linear array 21 . However, since the linear array 21 is arranged in one dimension, it cannot receive the entire two-dimensional image, but only a one-dimensional image, for example, a one-dimensional image 26 at the left end of the field of view 25. Next, when the reflecting mirror 23 rotates slightly around the rotation axis 24 in the direction of the arrow a in the figure, the image in the field of view 25 received by the linear array 21 becomes a one-dimensional image that has moved slightly to the right in the figure. If the reflector 23 is further rotated in the direction of the arrow a, the field of view 26
The entire two-dimensional image is scanned and received by the linear array 21.

FIG. 5 shows the relationship between the infrared radiation distribution in the field of view 25 in FIG. 4 and the output signal of the linear array 21. Now, A- in Figure 4
When the infrared radiation distribution amount on line A is as shown in FIG. A differential signal of such an infrared radiation distribution is extracted as an output signal. Similarly, the field of view 25 from other parts of the linear array 21 is
A differential signal of the infrared radiation distribution is extracted as the reflecting mirror 23 scans.

Since this output signal corresponds to the viewing direction from each element, by integrating these signals in the signal processing section, it is possible to measure the relative value of the two-dimensional infrared radiation temperature distribution. FIG. 5C shows the state of the output signal after the integral processing corresponding to the negative element.

Problems to be Solved by the Invention In the conventional thermal infrared imaging camera described above, since the pyroelectric infrared detection element IJ near array 21 is a differential detection element,
The output signal differs depending on the panning situation by the scanning reflector 23. In other words, the output signal is based on the temporal change of the input signal (
The larger the differential value), the larger the value.

However, in the configuration of the conventional thermal infrared imaging camera described above, the driving state of the reflecting mirror 23 is simply scanning at a constant speed, and is not designed to maximize the amount of change in the infrared input. However, it cannot be said that the characteristics of the pyroelectric infrared detection element are fully utilized. Therefore, there is a problem that the expected sensitivity characteristics have not been achieved yet.

Therefore, the present invention aims to solve the above-mentioned conventional problems, and provides a thermal infrared imaging camera that can improve the sensitivity characteristics of a pyroelectric infrared detection element. .

Means for solving the problems and technical means of the present invention for solving the above problems include a linear array in which a plurality of pyroelectric infrared detection elements are arranged in a row, an infrared optical system, , and a reflecting mirror for infrared image scanning, and the reflecting mirror is configured to perform panning scanning in a direction perpendicular to the linear array and to scan at a constant scanning angle in a stepwise manner.

Effect of the Invention With the above configuration, the present invention makes the driving situation of the reflecting mirror step-like, shortens the time required to scan from one instantaneous field of view to the next instantaneous field of view, stops in the instantaneous field of view for a certain period of time, and changes the stopping time. By setting the ratio of the first period travel time to several times or more, the amount of change in the infrared signal can be maximized, and the output signal of the pyroelectric infrared detection element can be maximized. Therefore, the characteristics of the pyroelectric infrared detection element can be fully brought out.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. 1 and 2 show a thermal infrared imaging camera according to an embodiment of the present invention, FIG. 1 is an overall schematic explanatory diagram, and FIG. 2 is an explanatory diagram of a driving section of a reflecting mirror.

In FIG. 1, numeral 1 denotes a linear array of pyroelectric infrared detection elements, which are arranged in parallel in a direction perpendicular to the plane of the drawing.

2 is an infrared optical system, 3 is a reflecting mirror for infrared image-dimensional scanning,
Both surfaces are mirror-finished, and the scanning direction is perpendicular to the parallel direction of the linear array 1. 4 is a signal processing unit for the output signal of the pyroelectric infrared detection element, 5 is a visible light source, which is arranged in a photodiode or linear array, and is combined with the mirror surface of the reflecting mirror 3, that is, the visible light reflecting surface. A thermal infrared image observed by receiving an infrared image signal from the thermal signal processing unit 4 can be converted into a visible image.

To explain the angle scanning mechanism of the reflecting mirror 3, the second
As shown in the figure, a driving rod 7 is fixed to the end of the rotational center shaft 6 of the reflecting mirror 3, and the reflecting mirror 3 operates in the same manner as the driving rod 7. The drive rod 7 is angularly driven by a pair of first and second drive cams 8 and 9 provided on both sides thereof. Each of the driving cams 8 and 9 has pinwheel-shaped teeth 10 formed on approximately half of its outer periphery, and the outer periphery without teeth 10 serves as a magnetized portion 11. And both cams 8.9
The positions of the drive rods 7 and 7 correspond to both sides of the drive rod 7, and the positions are shifted from each other by approximately 180 degrees in phase.

Both cams 8 and 9 rotate in opposite directions in synchronization.
In the state where the first cam 8 defines an angle by its melon 10 (the state shown by the solid line in FIG. 2), the second cam 9 contacts the drive rod 7 due to the repulsive force of its magnetized portion 11. Rather, the magnetic force acts to widen the distance between the two. This acting force serves to press the drive rod 7 against the first cam 8. In this state, both cams 8 and 9 rotate,
In the portion where the diameter of the first cam 8 becomes large, the second cam 9
The repulsive force of the magnetized portion 11 causes the drive rod 7 to
is pressed against the gourd 10 of the second cam 9, and is angularly driven in a stepwise manner following the shape of the gourd 10 of the second cam 9. With such a mechanism, the reflecting mirror 3 can always be driven in a stepwise manner in a reciprocating manner. If there is only one cam, the virtual shape of the cam 9 shown by the chain line in FIG. There is no step-like angular drive. The feature of using the pair of cams 8 and 9 is that they provide the reflecting mirror 3 with a drive as shown in FIG. 3(b). Although the number of steps is different from that of the cam 8.9 shown in FIG. 2, the number of steps is reduced in order to simplify the explanation.

Next, the operation of the above embodiment will be explained.

This embodiment differs from the conventional example described above particularly in that the reflecting mirror 3 is reciprocated in a stepped manner, so this point will be mainly explained.

As described above, since the reflecting mirror 3 is reciprocated in a stepwise manner by the rotation of the cams 8 and 9, the time required to scan from one instantaneous field of view to the next is shortened, and the mirror 3 is stopped for a certain period of time in that instantaneous field of view. By setting the ratio of the stop time to the first movement time to be several times or more, the amount of change in the infrared signal is maximized, and the output signal of the pyroelectric infrared detection element of the linear array 1 is maximized. To explain this in detail, one instantaneous field of view is scanned in a time sufficiently shorter than the thermal time constant tT of the pyroelectric infrared detection element of the linear array 1, and then it is stopped for a time equivalent to τT or longer. Therefore, the output signal of the pyroelectric infrared detection element with the number of daughters τ1 in the heat state is maximized.

That is, the differential value dI/dt of the infrared input (J: infrared intensity, t
: time) is given as a short enough time to sufficiently exceed the upper limit limited by τT, and is held for a time equivalent to the response time τ1 of the pyroelectric infrared detection element or longer,
The process waits until the detection element output becomes sufficiently high. Therefore, this scanning drive works to fully bring out the characteristics of the pyroelectric infrared detection element.

When the infrared radiation distribution shown in Figure 3 (a) is observed, the amount of change in the infrared radiation can be efficiently measured by scanning the stepped field of view as shown in Figure 3 (b), and the amount of change in the infrared radiation can be efficiently measured as shown in Figure 3 (e). The output signal of the infrared detection element as shown can be obtained.

If this is integrally processed by the signal processing section 4, a thermal infrared image signal as shown in FIG. 5(C) can be reproduced, and this signal processing section 4
A part of the output is applied to the photodiode array of the visible light source 5, causing the photodiode array to blink. This flashing light is reflected by the back surface of the reflecting mirror 3 and displayed as a visible image on a screen (not shown). That is, the infrared radiation distribution in the field of view can be observed as a visible light image. Therefore, it is possible to perform measurements with a higher S/N ratio than conventional thermal infrared imaging cameras.

Next, a prototype example of the present invention will be explained.

Pyroelectric infrared detection element IJ near array 1 has 12 linear
Eight elements were arranged in parallel with a pitch of 0.1n and a total length of 12.811. The dimensions of the pyroelectric infrared detection element in the scanning direction of the reflecting mirror 3 are 0.
One fin. The infrared optical system 2 had a focal length of 50 mm, had an anti-reflection coating of 10 μm in the center, and also served as a transmission window for the 8-12 μm band. The scanning angle of the reflecting mirror 3 was 011° in viewing angle (0.055° in mirror angle) and 128 steps.

Therefore, the viewing angle in the scanning direction is 14.7°, and the viewing angle in the linear array direction is also the same. The visible light source 5 has 128 photodiodes arranged in a linear array. The number of steps of the cams 8 and 9 was 128.

Then, the cams 8 and 9 were rotated half a revolution per second at a rotational speed of 3 Qrpm. In this half-circle, 128 steps are driven, so one step is approximately 13m5.IJ near array 1
The thermal time constant (τT) of the pyroelectric infrared detection element of 3 ms could be maintained for a sufficient period of time. The time required to move one step is approximately 0.1 mS, which is 1/30 of τT,
The time is sufficiently short, and compared to the case of using a conventional reflector with a constant angular velocity, the S/
It was possible to improve N by about 1.5 times.

Effects of the Invention As described above, according to the present invention, since the reflecting mirror scans stepwise angles, it is possible to maximize the output signal of the pyroelectric infrared detection element and improve its sensitivity characteristics. The S/N ratio of the output signal of the pyroelectric infrared detection element can be improved compared to the case where a reflector with a constant angular velocity is used.

[Brief explanation of the drawing]

1 and 2 show a thermal infrared imaging camera according to an embodiment of the present invention, FIG. 1 is an overall schematic explanatory diagram, FIG. ), (b), (C)
4 is a diagram showing the relationship between the field of view scanning situation, infrared radiation distribution, and infrared detection element output signal of the thermal infrared imaging camera of the present invention; FIG. 4 is a schematic explanatory diagram showing the conventional thermal infrared imaging camera; Figure 5 (
Figures a), (b), and (C) are diagrams each showing the relationship between the output signal of a conventional thermal infrared imaging camera and the infrared radiation distribution amount of the differential signal before signal processing. DESCRIPTION OF SYMBOLS 1... Pyroelectric infrared detection element linear array, 2... Infrared optical system, 3... Scanning reflector, 4... Signal processing section,
5... Visible light source, 6... Scanning reflector rotation axis, 7...
- Scanning reflector drive rod, 8, 9... cam, 11... magnetized part. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1 Figure 2 Figure 3 Right column of Figure 1 5 Column 21 A-A' w! r time

Claims (4)

[Claims] (1) A linear array in which a plurality of pyroelectric infrared detection elements are arranged in a row, an infrared optical system, and a reflecting mirror for scanning an infrared image, the reflecting mirror being arranged in a direction perpendicular to the linear array. 1. A thermal infrared imaging camera, characterized in that it is configured to perform panning scanning and to scan at a constant scanning angle in a stepwise manner. (2) The thermal infrared imaging camera according to claim 3, wherein the constant scanning angle at which the reflecting mirror is scanned stepwise is equal to the instantaneous viewing angle in the panning direction. (3) A claim in which both surfaces of the reflecting mirror are formed into mirror surfaces, one of which is a reflecting surface for scanning an infrared image, and the other is a visible light reflecting surface for scanning visible light and creating a visible image. The thermal infrared imaging camera according to item 1. (4) A patent claim in which the time required to move a fixed scanning angle in stepped scanning of the reflecting mirror is sufficiently shorter than the thermal time constant of the pyroelectric infrared detection element, and the stopping time is equivalent to or longer than the thermal time constant. A thermal infrared imaging camera according to scope 1.