JPH09189610A - Two-dimensional time delay integration type thermal imager - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To improve thermal image quality acquired by an infrared sensor. SOLUTION: A two-dimensional infrared sensor 1 in which infrared detection elements are two-dimensionally arranged receives a light reception input of a subject by a combination scan of a main scanning (horizontal direction) and a sub-scanning (vertical direction) separately in an optical scanning system, and performs a main scanning. Directional outputs are added and output by TDI (time delay integration) circuits 2a to 2d after time position alignment by time delay, and these added outputs are added by delay addition circuits 3a to 3d.
In 3c, a two-dimensional time-delay integration processing is performed in which the TDI processing is performed in the sub-scanning direction and then added and output by the addition circuit 4, and the thermal image quality (S / N ratio) is significantly improved by the time-delay integration effect over the two-dimensions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-dimensional time-delay integration type thermal imager, and more particularly to improving the image quality of a thermal image obtained by a raster scan including a horizontal direction and a vertical direction of a subject by a two-dimensional infrared sensor. The present invention relates to a two-dimensional time delay integration type thermal imaging device which is secured based on a three-dimensional time delay integration process.

[0002]

2. Description of the Related Art As a method for ensuring the improvement of the image quality of a thermal image obtained by arranging a plurality of infrared detecting elements, the conventional TDI is used.
The (Time Delay and Integration) method or the parallel scan method is well known. The TDI method is a method of improving the image quality by arranging a plurality of infrared detecting elements one-dimensionally in the main scanning direction (scanning direction with a faster scanning speed) and adding the outputs of the individual infrared detecting elements while delaying. Is. Generally, the sensitivity is set to N by delaying and adding the outputs of N infrared detection elements.
And the S / N ratio can be improved in proportion to N ^1/2 times.

As shown in FIG. 5, a thermal image device of the TDI system has a predetermined number of rotations (for example, in a rotation direction R1).
Main scanning device 8 having a rotary polygon mirror (polygon mirror) that rotates at 14,400 rpm) and performs horizontal scanning, and a predetermined number of repetitions (for example, 15 Hz) about rotation shaft 91 in rotation direction R2. Sub-scanning device 9 having a plane mirror for performing
And a lens 11 that focuses the input light that has been two-dimensionally scanned by a combination scan (raster scan) of the main scanning device 8 and the sub-scanning device 9, and the focused output of the lens 11 is received and converted into an electrical signal for output. The infrared sensor 10 as a one-dimensional detection element array is provided as a basic configuration.

FIG. 5 also shows a subject 103 that receives light through a light receiving window such as a silicon window or a light receiving optical system (not shown).
A main scanning (horizontal scanning) direction 101, a sub-scanning (vertical scanning) direction 102, and a detection area 106 corresponding to each infrared detection element included in the infrared sensor 10 are shown. The input light for each infrared light receiving element acquired by the infrared sensor 10 is then combined with a thermal image by the light receiving signal processing circuit shown in FIG.

The infrared sensor 12 shown in FIG. 6 comprises a plurality of infrared detecting elements 121-1 to 121-8 arranged one-dimensionally. These infrared detection element is generally I _n S _b and H _g C _d T _e quantum infrared detection element, such as are utilized, one side has a square or rectangular shape having 10 microns, is infrared element surface When incident, electric signal conversion is performed according to the incident amount.

In order to obtain a more sensitive signal by using this infrared detecting element, the TDI method shown in FIG. 6 is used, and N infrared detecting elements (in FIG. 6, in series in the optical scanning direction of infrared rays are used. Since N = 8) is arranged, infrared rays from any same part of the subject are incident on each infrared detection element with a fixed time delay corresponding to the scanning speed, and these detection outputs are delayed by the delayed time. Then, the light receiving sensitivity can be increased N times by adding the cumulative processing of sequentially adding to the outputs of the adjacent infrared detecting elements, and the noise is also added. Since it does not exist, the increase is only N ^1/2 times, and the S / N ratio is N ^1/2.
In addition to the double improvement, the spatial resolution is determined by the size of one infrared detection element, so that it is possible to avoid sacrificing the spatial resolution.

Mechanical scanning direction (main scanning direction) L of the optical system
The detection outputs of the infrared detection elements 121-1 to 121-8 scanned in the direction of are amplified by amplifiers 13-1 to 13-8, respectively,
The TDI processing is performed by delaying the delay adding circuits 14-1 to 14-7 one by one by a delay time corresponding to the scanning time and sequentially adding the outputs to adjacent amplifier outputs to perform addition synthesis.
An output 1301 having a light-receiving sensitivity N times is obtained. However, in this case,
Only the delay addition circuit 14-1 sets the addition amount to 0 in advance.

The parallel scan system uses an infrared sensor 15 in which a plurality of infrared detecting elements are one-dimensionally arranged in the sub-scanning direction 102, as shown in FIG.
The scanning speed of each infrared detection element at a constant frame rate of the thermal image is reduced to a low scanning speed by sub-scanning to narrow the occupied band of the detection signal, thereby suppressing noise. The occupied band is set to 1 / N by N infrared detection elements, and the improvement of the S / N ratio can be secured in proportion to N ^1/2 . The processing of the detection signal by the infrared sensor 15 is performed according to the configuration shown in FIG.

Further, as a further development of the TDI system, there is a SPRITE infrared sensor, which is shown in FIG. This SPRITE infrared sensor is configured as an infrared sensor 16 having a filament-shaped infrared detection element 17 arranged in a long and narrow direction in the mechanical scanning direction (main scanning direction) L of the optical system, and the delay addition circuit 14- shown in FIG. 1 to 14
A delay addition processing circuit by -7 or the like is integrally built in the infrared detection element 17, and the electrodes also have a very simple structure with two driving bias electrodes and one output. The output is amplified by the amplifier 18 and the TDI shown in FIGS.
An output 1801 equivalent to the output of the scheme is obtained.

[0010]

However, the image quality improving effect of the thermal image, that is, S /
Since the N-ratio improvement degree is proportional to the number N ^1/2 of the infrared detection elements included in the infrared sensor, it is necessary to significantly increase the number of infrared detection elements in order to obtain a large image quality improvement effect. For example, in order to improve the S / N ratio 10 times, theoretically, a one-dimensional array of 100 infrared detection elements is required.

In the TDI system, it is necessary to arrange 100 infrared detection elements and delay adder circuits in the main scanning direction, but an optical system that provides sufficient imaging performance for all these infrared detection elements is not available. It is extremely large and extremely impractical.

In the parallel scan system, a delay circuit is not necessary, but 100 infrared detecting elements are also arranged in the sub-scanning direction, and the optical system becomes extremely large as in the TDI system. , Due to variations in the characteristics of individual infrared detection elements, variations in sensitivity occur for each scanning line formed by each infrared detection element, and it is extremely difficult to eliminate such variations in sensitivity by the infrared detection element itself or signal processing. is there.

For the above reasons, the commercial infrared camera which has improved the image quality by operating a plurality of infrared detecting elements uses only about 10 infrared detecting elements at most, and therefore the image quality is improved. It is also the limit.
This also applies to the SPRITE infrared detector,
A one-dimensional array filament having a length of about 10 infrared detection elements has been put into practical use only in earnest.

The object of the present invention is to solve the above-mentioned problems and to delay all the outputs of the two-dimensionally arranged infrared detecting elements to synthesize and output them, thereby significantly improving the sensitivity and S / S.
(EN) A two-dimensional time delay integration type thermal imager capable of improving N ratio.

[0015]

The present invention has the following means in order to achieve the above object. That is, the first configuration of the present invention related to the two-dimensional time-delay integration thermal imaging device is to optically two-dimensionally scan a subject to detect infrared rays,
A two-dimensional time-delay integration type thermal imaging device which reproduces a surface temperature distribution image of the subject based on a time-delay integration process of a detection signal, wherein each of (a) to (c) below is provided. Have. (A) An optical scanning mechanism including a horizontal scanning device and a vertical scanning device for optically scanning the subject in the horizontal and vertical directions to obtain a two-dimensional image. (B) Arranged in a reflection optical path formed by the horizontal scanning device. Infrared sensor formed by arranging a plurality of infrared detecting elements for detecting infrared rays in a two-dimensional manner. (C) The detection signals of the individual infrared detecting elements included in the infrared sensor are detected in the horizontal and vertical directions by the optical scanning mechanism. Based on the time delay integration processing that delays by the delay time between adjacent infrared detecting elements in the optical scanning of the above, and sequentially adds to the detection signals of the adjacent infrared detecting elements and adds them together, the detection sensitivity and the signal-to-noise ratio are detected. Delay adder circuit that effectively increases the number of scans

A second structure of the present invention is the same as the first structure, wherein the infrared sensor has a plurality of infrared detecting elements arranged in a matrix.

According to a third structure of the present invention, in the first structure, the infrared sensor sequentially delays the adjacent infrared detecting elements by a delay time of a detection signal caused by a scanning timing difference between the adjacent infrared detecting elements. A plurality of one-dimensional arrays of time-delay integration type infrared detection elements that are superimposed on the detection signal and combined are two-dimensionally arrayed in parallel to the horizontal scanning direction.

According to a fourth aspect of the present invention, in the first configuration, the infrared sensor is integrated by incorporating the time-delay integration processing function into the time-delay integration type infrared detection element itself of the one-dimensional array. A plurality of SPRITE infrared sensors having the configuration are two-dimensionally arranged in parallel to the horizontal scanning direction.

In a fifth configuration of the present invention, in the first configuration, the delay adder circuit outputs the output of the time delay integration processing in the horizontal optical scanning of the infrared sensor to the infrared sensor vertically. The two-dimensional time delay integration process is ensured while repeating the delay addition in the time delay integration process in the optical scanning in the direction.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The detection outputs of N infrared detecting elements which are one-dimensionally arrayed in the main scanning (high-speed horizontal scanning) direction or the sub-scanning (low-speed vertical scanning) direction are set for each delay time required for scanning. Infrared rays by the TDI method or parallel method that delays and sequentially adds to the output of the adjacent infrared detection element to cumulatively combine them to effectively increase the light receiving sensitivity to N times and improve the S / N ratio to N ^1/2 times. In thermal image processing, the light receiving sensitivity and S
Since the image quality improvement represented by the / N ratio is proportional to N, that is, the number of array infrared detection elements, it is necessary to increase the number of array infrared detection elements in order to improve the improvement.

Therefore, if the degree of improvement in image quality is to be multiplied by N, the number of arrayed infrared detecting elements will be N ² times, and it is necessary to arrange the arrayed infrared detecting elements in the main scanning direction or the sub-scanning direction. It will be extremely unrealistic and difficult to realize, including the problem of variation.

In the present invention, the infrared detecting elements are arranged in a two-dimensional array in which the main scanning direction and the sub-scanning direction are arranged, and the outputs of a plurality of infrared detecting element arrays arranged in the main scanning direction are delayed and added by the TDI method. By performing a two-dimensional delay addition process of outputting the delayed addition outputs of the plurality of main scanning directions in the sub-scanning direction, it is possible to improve the image quality with a realizable configuration.

According to the present invention, for example, in order to increase the image quality improvement degree by N times, it is sufficient to arrange N arrays in the main scanning direction and N arrays in the sub scanning direction in parallel, which is realistic. The embodiment is characterized in that the structure can be easily secured.

[0024]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention. The configuration of the embodiment shown in FIG. 1 has a two-dimensional infrared sensor 1 in which a plurality of infrared detecting elements are two-dimensionally arranged in a matrix, and a time delay of the infrared detecting elements arranged in the main scanning direction of the two-dimensional infrared sensor 1. TD that performs integration processing
I circuits 2a, 2b, 2c and 2d, and TDI circuit 2a
The delay adding circuits 3a, 3b and 3c and the adding circuit 4 for performing the time delay integration processing of the outputs of 2d to 2d in the sub-scanning direction are provided. These have a configuration used in combination with a scanning optical system according to the scanning optical system shown in FIG.

Next, the operation of this embodiment will be described.
The two-dimensional infrared sensor 1 has 4
Infrared detecting elements S1a, S1b, S1c and S1
d, S2a, S2b, S2c and S2d, S3a, S
3b, S3c and S3d, S4a, S4b, S4c and S4d are arranged in parallel to form a two-dimensional array by a matrix arrangement of 4 × 4 infrared detection elements.

2A and 2B are explanatory views of the optical scanning in the embodiment of FIG. 1. FIG. 2A shows the fifth main scanning state, and FIG. 2B shows the sixth main scanning state. . Since the two-dimensional infrared sensor 1 has a matrix arrangement of 4 × 4 infrared detection elements in the main scanning direction × sub-scanning direction as a scanning unit, the projected image of the infrared detection elements, that is, the detection area 104 for the subject 103 is also included. , Is expressed as a detection unit of 4 × 4 divisions corresponding to the light receiving surface of the infrared detection element.

Scanning by the two-dimensional infrared sensor 1
A combination of horizontal main scanning and vertical sub-scanning is one scanning line corresponding to the width in the sub-scanning direction of the infrared detection element indicated by main scanning numbers # 1 to # 9 ... #n. Scanning is performed one after another while shifting downward by each minute. 2A shows the fifth main scanning state, and FIG. 2B shows the sixth main scanning state.

Returning to FIG. 1, the description of the embodiment will be continued. By scanning the subject 103 in the main scanning direction 101 with the two-dimensional infrared sensor 1 in a combination of main scanning and sub-scanning,
Infrared detector elements S1a to S1d, S2 arranged in a matrix
The four detection outputs obtained for each of the main-direction arrays a to S2d, S3a to S3d, and S4a to S4d are supplied to the TDI circuits 2a, 2b, 2c, and 2d, respectively, and described above with reference to FIG. The delay addition processing in the main scanning direction based on the time delay integration processing is performed. Scanning including main scanning and sub-scanning is repeated while shifting the main scanning number by one, and the entire field of view of the subject 103 is scanned.

While the TDI circuits 2a to 2d perform the time delay integration processing in the main scanning direction in the full-field scanning, the delay addition circuit 3 is applied to the outputs of these TDI circuits 2a to 2d.
a to 3c and the adder circuit 4 perform the time delay integration processing in the sub-scanning direction, and as a result, the two objects of the subject 103 are formed by all the infrared detecting elements arranged in a two-dimensional matrix.
Dimensional time delay integration processing is ensured.

The delay adder circuit 3a includes a delay adder circuit 3b,
3c has the same configuration as that of 3c, but the amount of addition is set to zero, and as a result, the delay time for one infrared detection element corresponding to the sub-scan time is added to the output of the TDI circuit 2a, and the delay addition is performed. The circuit 3b delay-adds the output of the delay-add circuit 3a to the output of the TDI circuit 2b, and also delay-add circuit 3c.
Delays and adds the output of the delay addition circuit 3b to the output of the TDI circuit 2c. The delay amount in each of the delay addition circuits 3b and 3c is the infrared detection element 1 at the sub-scanning speed.
The amount of time delay per piece.

The adder circuit 4 adds the output of the delay adder circuit 3c to the output of the TDI circuit 2d to obtain the output 401 by the two-dimensional time delay integration processing. By performing such two-dimensional time delay integration processing over the entire area of the subject 103, a remarkable improvement in image quality can be obtained.

FIG. 3 is a block diagram showing the configuration of the second embodiment of the present invention. The second embodiment shown in FIG. 3 is a two-dimensional infrared sensor 5 in which four SPRITE infrared sensors 51 to 54 are arranged in parallel, and delay addition circuits 6a to 6c.
And an adder circuit 7. The examples shown in FIGS. 3A and 3B also have a configuration in which they are used together with a scanning optical system according to the scanning optical system shown in FIG. The operation of the second embodiment is basically the same as the operation of the first embodiment shown in FIG. 1, but the SPRI in which four individual infrared detecting elements are integrally configured.
By replacing with the TE infrared sensor, the delay addition circuit in the main scanning direction can be significantly compressed. In this case, the SPRITE infrared sensors 5 adjacent to each other in the sub-scanning direction
Since 1 to 54 have a time difference of several main scanning times, the delay times given by the delay adder circuits 6a to 6c are also set in consideration of this condition. Note that only the addition amount of the delay addition circuit 6a is set to zero. From the adder circuit 7, 2
An output 701 is obtained by the dimensional time delay integration processing.

FIGS. 4A and 4B are explanatory views of the optical scanning in the embodiment of FIGS. 3A and 3B. FIG. 4A shows the fifth main scanning state, and FIG. 4B shows the sixth main scanning state. . The scanning unit in the main scanning in this case is the same as that in the case of FIG. 2, but the detection area 105 as a scanning unit consists of four detection fields of view by each SPRITE infrared sensor. In this way, the image quality can be significantly improved by the two-dimensional time delay integration processing for the subject 103.

[0034]

As described above, according to the present invention, the outputs from the optical main scanning and sub-scanning of a plurality of infrared detecting elements arranged two-dimensionally are all based on the time delay integration processing in the main scanning and sub-scanning directions. The thermal image quality can be remarkably improved by adding and synthesizing over the range, and the degree of the improvement is N ^{2 when the} number of one-dimensional array infrared detecting elements in the conventional TDI method or parallel scan method is N ^1/2 times.
There is an effect that it can be improved to about double. Further, by performing the time-delay integration processing on the received light signal also in the sub-scanning direction, it is possible to avoid the occurrence of quality variation for each scan due to the variation between the infrared detection elements which occurs in the parallel scan method.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is an explanatory diagram of optical scanning according to the first embodiment of this invention.

FIG. 3 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is an explanatory diagram of optical scanning according to the second embodiment of the present invention.

FIG. 5 is a diagram showing a basic configuration of a thermal image device according to the TDI method.

FIG. 6 is a block diagram showing a basic configuration for thermal image formation by the TDI method.

FIG. 7 is a diagram showing a basic configuration of a thermal image device of a parallel scan system.

FIG. 8 is a block diagram showing a basic configuration of a SPRITE infrared sensor.

[Explanation of symbols]

 1 Two-dimensional infrared sensor 2a-2d TDI circuit 3a-3c Delay addition circuit 4 Addition circuit 5 Two-dimensional infrared sensor 6a-6c Delay addition circuit 7 Addition circuit 8 Main scanning device 9 Sub-scanning device 10 Infrared sensor 11 Lens 12 Infrared sensor 13 -1 to 13-8 Amplifier 14-1 to 14-7 Delay addition circuit 51 to 54 SPRITE infrared sensor

Claims (5)

[Claims] 1. An optical system for shooting a subject, comprising:
A two-dimensional time-delay integration type thermal imaging device, characterized by performing infrared scanning to detect infrared rays and reproducing a surface temperature distribution image of the subject based on time-delay integration processing of a detection signal. (A) An optical scanning mechanism including a horizontal scanning device and a vertical scanning device for optically scanning the subject in the horizontal and vertical directions to obtain a two-dimensional image. (B) Arranged in a reflection optical path formed by the horizontal scanning device. Infrared sensor formed by arranging a plurality of infrared detecting elements for detecting infrared rays in a two-dimensional manner. (C) The detection signals of the individual infrared detecting elements included in the infrared sensor are detected in the horizontal and vertical directions by the optical scanning mechanism. Based on the time delay integration processing that delays by the delay time between adjacent infrared detecting elements in the optical scanning of the above, and sequentially adds to the detection signals of the adjacent infrared detecting elements and adds them together, the detection sensitivity and the signal-to-noise ratio are detected. Delay adder circuit that effectively increases the number of scans 2. The two-dimensional time-delay integration type thermal imaging device according to claim 1, wherein the infrared sensor has a plurality of infrared detection elements arranged in a matrix. 3. A one-dimensional array of time delays in which the infrared sensor sequentially delays a detection signal due to a scanning timing difference between adjacent infrared detection elements and superimposes and combines the detection signals of the adjacent infrared detection elements. 2. The two-dimensional time-delay integration thermal imager according to claim 1, wherein a plurality of integration-type infrared detection elements are two-dimensionally arranged parallel to the horizontal scanning direction. 4. The integrated SPRITE (Signa) in which the infrared sensor incorporates the time delay integration processing function in the time delay integration type infrared detection element itself of the one-dimensional array.
2. The two-dimensional time-delay integration type thermal imager according to claim 1, wherein a plurality of infrared processing sensors are two-dimensionally arrayed in parallel to the horizontal scanning direction. 5. The delay addition circuit delay-adds the output of the time delay integration processing in the optical scanning in the horizontal direction to the infrared sensor in the time delay integration processing in the optical scanning in the vertical direction to the infrared sensor. The two-dimensional time-delay integration process is ensured while repeating the above process.
-Dimensional time delay integration type thermal imager.