JPH09318456A - Scan type infrared ray optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve picture quality of an infrared ray image with two dimensional scanning obtained based on TDI(time delay integration) process. SOLUTION: A photo detection input which is photo-detected through a main scan mechanism 1 which utilizes a rotating polygon mirror, a sub-scan mechanism 2 which utilizes a rotary flat mirror and an optical system 3, is converted into electric signal with an infrared ray detector 4, and sent to a time delay integration processing part 5. The time delay integration processing part 5, related to the photo detection output for each scan line from scan lines Rn-Rn+3 , etc., matches, in time base, the outputs for each continuous scan with time delay for addition-output, so that occurrence of stripe pattern on a thermal image caused by dispersion in reflection coefficient of each rotary flat mirror caused by TDI process output is essentially suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning infrared optical device, and more particularly, it performs raster scanning in which horizontal main scanning and vertical sub-scanning are combined and time delay integration (TDI) method. The present invention relates to a scanning infrared optical device that is effective in improving the image quality of an infrared camera that obtains a thermal image in the above.

[0002]

2. Description of the Related Art Conventionally, as an infrared optical device for acquiring an infrared thermal image by using a rotating polygon mirror for main scanning, a method using a single infrared detector is used, and a plurality of infrared detectors are arranged in the main scanning direction. Then, the output signals of these detectors are sequentially delayed by the time required for scanning and added and synthesized as in-phase in time, and a plurality of infrared detectors are arranged in parallel in the sub-scanning direction and these infrared rays are detected by one main scan. In addition to the parallel scan method that performs raster scanning of the number of detectors, a two-dimensional TDI method that performs TDI processing using a two-dimensional array of infrared detection elements that combines the TDI method and the parallel scan method (for example, Japanese Patent Application No. 8- 20552,
There is a two-dimensional time delay integration type thermal imager.

According to the TDI method described above, the sensitivity can be increased N times and the S / N ratio can be improved to N ^1/2 by delay-adding the outputs of the N infrared detecting elements.

[0004]

However, in each of the above-mentioned various methods, the reflectance of each reflecting surface of the rotating polygon mirror (polygon mirror) used for main scanning varies, or a certain reflecting surface is used in the manufacturing process. When there are scratches or stains on the surface, the output value of the detector changes only for the scanning line corresponding to the reflection surface, and horizontal stripes appear on the thermal image screen that should be uniform.

Therefore, when manufacturing the polygon mirror, special processing and inspection are required to make the reflectances of the respective reflecting surfaces the same, and the yield of the products is poor. Further, if the reflecting surface is erroneously scratched or stains cannot be removed during adjustment of the infrared optical system, the polygon mirror itself must be discarded.

The object of the present invention is to solve the above-mentioned problems and to make the imaging field of view two-dimensional by making the number of arrayed infrared detectors arranged in the sub-scanning direction coincide with the number of reflection surfaces of the polygon mirror used for main scanning. The output of each polygon detector is accumulated by adding the output signal of each infrared detector while delaying the time corresponding to the scanning time to the infrared detectors arranged in the sub-scanning direction. Another object of the present invention is to provide a scanning infrared optical device that eliminates the influence of dirt that cannot be removed.

[0007]

The present invention has the following means in order to achieve the above object. That is, the first configuration of the present invention relating to the scanning infrared optical device is a case where a thermal image acquired by raster scanning by performing horizontal scanning and vertical scanning of an object is two-dimensionally processed by a time delay integration method. In addition, a scanning infrared optical device characterized in that it is possible to eliminate the influence of variations in reflectance due to scratches or dirt on the reflecting surface of a rotating polygon mirror that performs horizontal scanning, and is shown below (a) To (c). (A) A horizontal scanning mechanism and a vertical scanning mechanism that independently perform high-speed horizontal scanning as high-speed main scanning and vertical scanning as low-speed sub-scanning on a subject to perform the raster scan, respectively. Further, an optical scanning section in which an optical system for optically focusing the scanning output of the raster scan to form a light receiving field is arranged. (B) A light receiving infrared ray which is linearly arranged in the sub scanning direction of the light receiving field by the optical scanning section. An infrared detector having a plurality of infrared detectors, which are equal in number to the number of reflecting surfaces of the rotating polyhedral mirror, for transmitting the electric power to the electric output. The detection output obtained from the scanning line is
A time-delay integration processing section that delays each successive sub-scan by the delay time required for the sub-scan and adds the outputs by time matching them.

According to a second structure of the present invention, in the first structure, the plurality of infrared detectors included in the infrared detector have amplifiers capable of setting outputs to the same level.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In order to perform a two-dimensional raster scan of an object, a high-speed main scan in the horizontal direction and a low-speed sub-scan in the vertical direction combined with this main scan are independently executed in parallel. A rotating polygon mirror, a so-called polygon mirror, is usually used for scanning. This polygon mirror has a reflecting surface formed by a plurality of plane mirrors forming a polyhedral mirror, and the main scanning in the horizontal direction of the object is performed by high-speed rotation of the reflecting surface.

Therefore, it is necessary that all of the plurality of reflecting surfaces have the same reflectance.
If scratches or irremovable stains are attached during the manufacturing process, adjustment, or for some other reason, the infrared detector output of the horizontal scanning line corresponding to the reflecting surface will change, and it should be uniform on the screen. Horizontal stripes, so-called image stripes, appear on the screen, resulting in screen deterioration.

According to the present invention, in order to improve screen deterioration caused by scratches and stains on the individual reflecting surfaces of the polygon mirror, the number of reflecting surfaces of the polygon mirror in infrared image formation and the one-dimensional array in the sub-scanning direction are arranged. When the number of infrared detectors included in the infrared detector matches, the addition output of the same scanning line for each sub-scan of the time series data in the TDI method becomes the same, which effectively affects the above-mentioned screen deterioration. Paying attention to the effect that can be eliminated, the number of reflecting surfaces of the polygon mirror and the number of infrared detectors which are one-dimensionally arrayed in the sub-scanning direction are matched, and the output for each sub-scanning obtained from the same scanning line is obtained. A scanning infrared optical device that suppresses the occurrence of image stripes by time-matching with delay and sequentially accumulating to make the output level from the same scanning line constant It is as embodiments that formed.

[0012]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a perspective view of the configuration of an embodiment of the present invention. In the embodiment shown in FIG. 1, the case where the number of reflecting surfaces of the polygon mirror is 4 is taken as an example, and a main scanning mechanism 1 having a polygon mirror having four reflecting surfaces as a tetrahedron and performing high-speed horizontal scanning is provided. , A sub-scanning mechanism 2 using a rotating plane mirror for performing low-speed vertical scanning and raster scanning in combination with the main scanning mechanism 1, and an optical system for converging and outputting the received light output of the raster scan to form a desired light receiving field of view. 3 and an infrared detector 4 in which four infrared detectors having the same number of reflecting surfaces as the main scanning mechanism 1 are arranged in the sub-scanning direction.
1 and a time delay integration processing unit 5 that performs the TDI processing unique to the present invention on the output of the infrared detector 4.
Note that the imaging field of view 101, the main scanning direction 102, and the sub-scanning direction 103 are also shown together. In the configuration described above, the main scanning mechanism 1, the sub-scanning mechanism 2 and the optical system 3 form an optical scanning unit.

Next, the operation of this embodiment will be described.
The polygon mirror of the main scanning mechanism 1 has four identical planar reflecting surfaces M1, M2, M3 and M4, and rotates in the direction of the arrow around the rotating shaft 11 at a predetermined high speed. The sub-scanning mechanism 2 rotates about the rotation shaft 21 at a predetermined low speed.
The rotation indicated by the double arrow is performed. Main scanning mechanism 1 and sub scanning mechanism 2
As a result, the raster scan is ensured by the scanning of the combination of the main scanning direction 102 and the sub scanning direction 103 with respect to the imaging visual field 101.

FIG. 1 shows one of such raster scans.
For example, on the scanning lines R _n , R _{n + 1} , R _{n + 2} and R _{n + 3} on the imaging field of view 101, in the direction of the main scanning direction 102, four infrared detection element light receiving fields D1 and D2 to be described later are provided. , D3 and D4.

The received light output for each scan of the raster scan is converged by the optical system 3, and the infrared detector 4
Receiving fields D1, D2, D3 and D of two infrared detectors
4 is received.

FIG. 2 is a block diagram showing the configurations of the infrared detector 4 and the time delay integration processing section 5. The infrared detector 4 includes four infrared detecting elements 41a, 41b, 41c and 4 having the same number of reflecting surfaces as the polygon mirror.
1d and four variable gain amplifiers 42a, 42b, 42c for amplifying the outputs of these four infrared detecting elements to a constant level and correcting sensitivity variations among the infrared detecting elements.
And 42d as an infrared detector.

The infrared detecting elements 41a to 41d convert the light receiving input for each sub-scanning into an electric output and sequentially shift the scanning lines one by one while sequentially delaying each for a fixed time required for the sub-scanning to receive four light-receivings. Send output.

The time-delay integration processing unit 5 detects the light reception output for each sub-scan provided from the infrared detector 4.
Sensitivity and S / N ratio are obtained by performing time-delay integration processing of temporally matching and adding detection outputs by four adjacent reflecting surfaces of the polygon mirror for each sub-scan obtained from the same scanning line by delay processing. To improve.

The time delay integration processing unit 5 shown in FIG. 2 is an example of a configuration for realizing the above-mentioned TDI processing, and the three adders 51a to 51c and the delay time are all set to the same sub-scanning time per one time. Three delay circuits 52a to 52c for setting are provided to obtain a desired TDI output 501.

Next, the operation of eliminating the influence of the variation in the reflectance due to the scratches and stains on the reflecting surface of the polygon mirror with such a configuration will be described. FIG. 3 is an explanatory diagram of the operation of the embodiment of FIG. 3A shows the first scanning, FIG. 3B shows the second scanning, and the scanning is continued until the nth scanning. In the first scan,
The scanning of the imaging visual field 101 is performed by raster scanning the scanning lines R1 to R4 in the main scanning direction 102 and the sub scanning direction 103. In the second scanning performed next, as shown in FIG. 3B, a raster scan targeting the scanning lines R2 to R5 is performed.

Reference numerals D1, D2, D3 and D shown in FIG.
4 is originally an infrared detection element 4 of the infrared detector 4.
1A, 41b, 41c, and 41d show the light-receiving fields of view, but for convenience of description, FIG. 3 shows imaging small areas of the respective infrared detection elements on the imaging field of view 101, and further, a polygon mirror. The light reception output obtained by the four reflecting surfaces of 4 and the imaging small area described above will be described as (M _n × D _n ) (n = 1 to 4).

Focusing now on the fourth scanning line R4, the output (M1 × D4) obtained by the infrared rays reflected by the reflecting surface M1 of the polygon mirror in the first scanning and detected by the infrared detecting element light receiving field D4 is obtained. To be This output is delayed by one sub-scan, and the output of the next second scan (M2 × D
Add 3).

Further, the result is added to the third result (M3 × D2) delayed by one sub-scan,
If the same thing is repeated once more, the addition output θ4 obtained as the output from the scanning line R4 is represented by the following formula 1.

[0024]

## EQU1 ## θ4 = (M1 × D4) + (M2 × D3) + (M
3 x D2) + (M4 x D1)

Considering the same thing for the fifth scanning line R5, it is shown by θ5 in the following equation 2.

[0026]

## EQU00002 ## .theta.5 = (M2.times.D4) + (M3.times.D3) + (M
4 x D2) + (M1 x D1)

Similarly, the sixth and seventh scan lines R6
The addition output by R7 and R7 is represented by θ6 and θ7 by the following formulas 3 and 4.

[0028]

## EQU3 ## θ6 = (M3 × D4) + (M4 × D3) + (M
1 x D2) + (M2 x D1)

[0029]

## EQU4 ## θ7 = (M4 × D4) + (M1 × D3) + (M
2 x D2) + (M3 x D1)

In this way, a similar output representation is obtained for each scan line. Infrared detector element light receiving field D1, D
The detection outputs of D2, D3, and D4 are set to be equal to each other, and D1 = D2 = D3 = D4 = D, so that the scanning line n is expressed by the following formula 5.

[0031]

[Mathematical formula-see original document] θn = (M1 + M2 + M3 + M4) × D (n = 4,5,6, ... m)

That is, no matter how the reflectance of the reflecting surfaces M1 to M4 changes, the total outputs are always equal to each other.

In the conventional method, the influence of the variation in the reflectance of each reflecting surface of the polygon mirror is unavoidable, and stripes appear on the screen as follows. For example, assume that there is one infrared detector and that the polygon mirror is a tetrahedron as in the embodiment. The output in this case is θ1 = (M1 × D), θ2 =
(M2 × D), θ3 = (M3 × D), θ4 = (M4 ×
D), θ5 = (M1 × D) ..., For example, when the reflectance of M1 is different from M2 to M4, θ1 and θ5 are different from other θ2, θ3, θ4, etc.
Every book appears as stripes on the screen.

In this embodiment, as described above, since the influence of the reflectance variation of the reflecting surface is basically eliminated, the occurrence of such stripes on the screen is eliminated,
Not only can the image quality be significantly improved, but the polygon mirror itself can also be manufactured and maintained very easily.

[0035]

As described above, according to the scanning infrared optical apparatus of the present invention, the TDI processing is performed on the light receiving input obtained by the raster scan by the parallel execution of the high speed main scanning using the polygon mirror and the low speed sub scanning. When a thermal image is generated by performing a TDI process that sequentially delays the light-receiving input for each scan from the same scanning line in the imaging field of view for each scanning time to achieve time alignment and adds and outputs them, the polygon There is an effect that the influence of the reflectance due to scratches and dirt between the reflecting surfaces of the mirror can be fundamentally eliminated to significantly improve the image quality, and the manufacturing and maintenance conditions of the polygon mirror itself can be significantly eased.

[Brief description of drawings]

FIG. 1 is a block diagram showing a perspective view of a configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing the configurations of an infrared detector 4 and a time delay integration processing unit 5 of FIG. 1 together.

FIG. 3 is an explanatory diagram of the operation of the present invention.

[Explanation of symbols]

 1 Main scanning mechanism 2 Sub-scanning mechanism 3 Optical system 4 Infrared detector 5 Time delay integration processing section

Claims (2)

[Claims] 1. When a thermal image acquired by raster scanning by simultaneously performing horizontal scanning and vertical scanning of an object is two-dimensionally processed by a time delay integration method, the horizontal scanning is provided with each of the following configurations. A scanning infrared optical device capable of eliminating the influence of variations in reflectance due to scratches or dirt on the reflecting surface of the rotating polygon mirror. (A) A horizontal scanning mechanism and a vertical scanning mechanism that independently perform high-speed horizontal scanning as high-speed main scanning and vertical scanning as low-speed sub-scanning on the subject to perform the raster scan, respectively. Further, an optical scanning section in which an optical system for optically focusing the scanning output by the raster scan to form a light receiving field is arranged. (B) A light receiving infrared ray which is linearly arranged in the sub-scanning direction of the light receiving field by the optical scanning section. An infrared detector equipped with a plurality of infrared detectors, which are equal in number to the number of reflecting surfaces of the rotating polyhedral mirror, for transmitting the electric power to the electric output. The detection output obtained from the scanning line is
A time-delay integration processing section that delays each successive sub-scan by the delay time required for the sub-scan and adds the outputs by time matching them. 2. The plurality of infrared detectors included in the infrared detector are each equipped with an amplifier whose output can be set to the same level.
The scanning infrared optical device described.