JPH02186779A - Infrared-ray image pickup device - Google Patents

Abstract

PURPOSE:To exactly correct the characteristic dispersion of each detection element by non-linear-correcting the output of the detection element arranged in a row of an infrared-ray detection array by signal processing circuits each of which is provided with a ROM respectively, and outputting it through a scanning conversion circuit. CONSTITUTION:The outputs of the infrared-ray detection elements 191 to 198 arranged in a row of the infrared-rate detection array 7 are inputted to the corresponding signal processing circuits 101 to 108, and after they are A/D- converted 21, the corresponding ROM 22 in which a correction value is stored is referred to, and they are corrected in linear. These corrected signals are outputted as a parallel-series-converted video signals by the scanning conversion circuit 11, and become the signals in which the variance of each infrared-ray detection element is exactly corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an infrared imaging device used to display an image of a temperature distribution state of an object, and particularly to a signal processing method thereof.

``Prior Technology J'' Conventional infrared 1 imaging devices used a single infrared detection element to obtain video signals through rusk scanning using a mechanical scanning method. In pursuit of real-time performance, systems in which 50 to 150 elements are arranged in a row or a near array are beginning to be put into practical use.

FIG. 5 shows the basic configuration of this type of imaging device. A light beam 1 from an object enters a horizontal scan 113 via an infrared lens 2. The external shape of the horizontal scanning mirror 3 is, for example, a prism with a regular octagonal cross section, the side surfaces of which serve as mirrors that reflect infrared rays, and are rotated around the central axis YY. The light beam 1 reflected by the horizontal scanning mirror 3 is reflected by the vertical scanning mirror 4 and enters the reflecting mirror 5, where it is reflected again and enters the infrared detection array 6 via the imaging lens 6.

In this example, the array 6 is made up of eight elements, and as shown in FIG. 6, when an image is decomposed, eight rasters are used as IW to be horizontally and vertically scanned. That is, horizontal scanning is performed by rotating the horizontal scanning mirror 3 at high speed, and vertical scanning is performed by rotating the vertical scanning mirror 4 by the vertical scanning mechanism 8.
This is done by rotating or vibrating up and down. The infrared detection array 7 is housed in a dewar 9 and is cooled to about -190° C. with liquid nitrogen. The signals detected by each element of the detection array 7, that is, the photoelectrically converted signals V, 1 (i=1 to 8) are sent to a signal processing circuit 10+,
10z, . . . are amplified by log and input into the scan conversion circuit 11 in parallel. In the scan conversion circuit 11, the output Vs! of the signal processing circuit 107 input in parallel is inputted in parallel. is parallel-serial converted and converted into a standard television system, for example, an NTSC system television signal, which is output to an output terminal 12.

By the way, since there are variations in the photoelectric conversion characteristics of each detection element, a certain pattern of sensitivity nonuniformity occurs in the displayed image, which causes image quality deterioration, so it is necessary to correct the variations in the photoelectric conversion characteristics of each element. be. In the conventional correction method, each element is individually irradiated with light from two reference red sources (not shown) at temperatures Ta and Tb, and the input light 1 (Pa and p) of each element is
The gain and offset of the signal processing circuit 10+ are adjusted so that the outputs Vsi' of the signal processing circuit 10+ at b (corresponding to reference temperatures Ta and Tb, respectively) coincide with each other (see FIG. 7).

``Problems to be Solved by the Invention'' Conventional methods for correcting variations in each element of an infrared detection array are capable of complete correction if the characteristics of each element are linear. Further, even if the characteristics are non-linear, there is no problem as long as the characteristics in the usage area are almost the same by matching the characteristics at two points. However, this is not the case with infrared detection arrays, especially in the case of MCT detectors (detectors using mercury, cadmium, and tellurium), which have recently become widely used. Even if correction is possible within a range, the correction error will become large for images with large level differences in the amount of input light or images with large level fluctuations, and changes in image quality due to sensitivity variations cannot be avoided.

An object of the present invention is to provide a new signal processing method that can more accurately correct variations in characteristics of each element of an infrared detection array over a wider range than before.

[Means for Solving the Problems] The present invention relates to an infrared imaging device comprising a horizontal scanning mirror, a vertical scanning mirror, an infrared detection array, a plurality of signal processing circuits, and a scan conversion circuit. The infrared detection array has a plurality of infrared detection elements arranged in a row, and the signal processing circuit is provided for each infrared detection element, has a ROM, and processes the detection signals of the infrared detection elements. R.O.
The scan conversion circuit is input to the address input terminal of M and outputs a detection signal corrected for non-linearity of the corresponding infrared detection element stored in the corresponding storage area. It converts detection signals input in parallel from a plurality of signal processing circuits into parallel to serial, and converts them into standard television signals and outputs them.

Embodiment The imaging device of the present invention uses a mechano-optical scanning mechanism comprising a horizontal scanning mirror, a vertical scanning mirror, etc., as in the prior art. The present invention is characterized by the electronic circuits after the infrared detection array, especially the signal processing circuits.

As shown in FIG. 1, each element 19 of the infrared detection array 1
□ (i=1 to 8) detection outputs are each amplified by an amplifier 20 and then converted to a digital signal via an AD converter 21. The digital signal is input to an address input terminal of a ROM (read only memory) 22.

Each ROM 22 has a corresponding infrared detection element 19 in advance.
, the detection signal Vs' corrected for the nonlinearity is the detection signal Vs
It is stored in the storage area whose address is . That is, if the photoelectric conversion characteristic of the detection element 19 for infrared rays is deviated by 1 δν from the ideal straight line 00° at the point of the detection signal Vsν, as shown in FIG. As shown in FIG. 3, Vsv'=Vsv+δν is stored in the area. In this way, in a predetermined dynamic range of the detection signal Vs, the corresponding correction value Vs' is stored, forming a so-called reference table. Therefore, unique data corresponding to the characteristics of each element is stored in the reference table corresponding to each element. The output of the ROM 22, that is, the characteristic of the corrected detection signal Vs' with respect to the input light amount P is an ideal straight line as shown in FIG. In this way, the output of each ROM 22 with respect to the input light amount P has the same linear characteristic, so that each detection element 19. The variation in is corrected. Each ROM2
The outputs of 2 are inputted in parallel to the scan conversion circuit 11, where they are converted from parallel to serial, and also converted into a standard television system television signal (but a digital signal) and output to the DA converter 23, where they are converted into an analog television signal. Converted to output terminal 1
2 is output. Note that the above corresponding set of amplifiers 2
0, the signal processing circuit 10.0 by the AD converter 21 and the ROM 22. is configured.

"Effects of the Invention" According to the present invention, variations in the photoelectric conversion characteristics of each detection element of the infrared detection array 7 can be corrected more accurately over a wider range than conventional techniques. Therefore, even for images with large level differences in the amount of input light or images with large level fluctuations, there is no risk of image quality deterioration due to element variations, and higher quality images than conventional ones can be obtained.

Further, according to the present invention, in order to correct variations in detection elements, two reference red sources (reference temperature rA) as in the conventional method are used.
This also has the effect of making the equipment more economical.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a main part of an embodiment of the present invention, FIG. 2 is a diagram showing the photoelectric conversion characteristics of one detection element of the infrared detection array 7 of FIG. 1, and FIG. 3 is a diagram showing the characteristics of FIG. 2. 4 is a diagram for explaining a reference table stored in the ROM 22 of FIG. 1 which corresponds to the detection element 1 of FIG. 1.
ROM2 for input light amount P of 9+ (i=1 to 8)
FIG. 5 is a block diagram showing the basic configuration of a conventional infrared imaging device. FIG. 6 is a diagram showing the output characteristics of a conventional infrared imaging device. FIG. 7 is a diagram for explaining the state in which main parts are collectively analyzed and scanned, and FIG. 7 shows the output Vs' of the signal processing circuit 10 in FIG.
It is a figure which shows the example of a characteristic. 10 6 Decoy

Claims (1)

[Claims] (1) An infrared imaging device comprising a horizontal scanning mirror, a vertical scanning mirror, an infrared detection array, a plurality of signal processing circuits, and a scan conversion circuit, the infrared detection array comprising a plurality of infrared detection elements. are arranged in a row, and the signal processing circuit is provided for each infrared detection element, has a ROM, and transfers the detection signal of the infrared detection element to its RO.
The scan conversion circuit is input to the address input terminal of M and outputs a detection signal corrected for non-linearity of the corresponding infrared detection element stored in the corresponding storage area. An infrared imaging device that converts detection signals input in parallel from multiple signal processing circuits into parallel to serial, converts them into standard television signals, and outputs the signals.