JPS61191170A - Dc restoration circuit of infrared image projecting device - Google Patents

Abstract

PURPOSE:To reduce the variance of luminance due to the noise or the like superposed to an input signal by subtracting a clamp code signal, which prescribes a restoration level, from an input digital signal and subtracting the average value of this subtraction value from the input signal to project an image. CONSTITUTION:An input digital signal D from an A/D converter 5 is inputted to the first and the second subtracting circuits 6 and 11. The circuit 11 subtracts the clamp code signal, which is outputted from a clamp code generating circuit 7 and has a preliminarily prescribed clamp level, from the signal D and outputs the difference to a storage part 12. The storage part 12 outputs one-picture components of difference signal to an averaging circuit 13 after storing one-picture components of input difference signal. The circuit 13 detects the average level of one-picture components of difference signal and inputs this average level to the circuit 6. The circuit 6 subtracts the average level from the circuit 13 from the signal D and clamps the signal D at the average level to restore the DC, and it is stored in a memory part 8 and is displayed as an image on a display part 10 through a picture processing part 9. Thus, the variance of the clamp point is reduced to reduce the variance of luminance on the display part 10.

Description

[Detailed Description of the Invention] [Field of Industrial Application] (1) The present invention relates to a DC regeneration circuit for an infrared imaging device that performs digital image processing, and in particular, to a DC regeneration circuit that suppresses fluctuations in display brightness due to noise at a clamp point during DC regeneration. This invention relates to a DC regeneration circuit of an infrared imaging device that has been improved to eliminate the problem.

[Conventional technology]

FIG. 3 is a block diagram of a conventional infrared imaging device, and FIG. 4 is a signal waveform diagram for explaining the operation of a conventional DC regeneration circuit.

In FIG. 3, the infrared imaging device uses a multi-element detector 4 to horizontally scan the infrared light from the target object 1 reflected via the scanning mirror 2 in the direction from A to B with a width of viewing angle a1, and When horizontal scanning is completed, scanning mirror 2 is moved vertically from A to C.
, and scan the range a2.

In this way, the target object is sequentially scanned starting from 81 and the infrared rays emitted from the target object are captured. The infrared rays sequentially captured in this manner are collected by the optical system 3 and input to the infrared detector 4. The multi-element infrared detector 4 converts the infrared rays input sequentially for each horizontal scanning line into an electrical signal, and outputs the electrical signal to the A/D converter 5 as a series signal. A
The /D converter 5 converts the input electrical signal into a digital signal and outputs it to the first subtracter 6.

On the other hand, the clamp code generation circuit 7 generates a clamp code signal representing a predefined clamp level and generates a first clamp code signal.
is output to the subtracter 6.

The first subtracter 6 subtracts the clamp code signal output from the clamp code generation circuit 7 from the digital signal output from the A/D converter 5, digitally clamps the signal, performs DC reproduction, and stores the digital signal in the memory section. Output to 8. The memory section 8 stores the output signal of the first subtracter 6 for one screen, and then outputs it to the image processing section 9. The image processing unit 9 converts the digital signal for one screen into an analog signal again, amplifies it to a predetermined level, and then outputs it to the display unit 10. The temperature pattern of the target object for one screen is displayed on the display unit 10. Ru.

In the above clamp circuit, as shown in Fig. 4,
When the scanning mirror 2 captures noise whose level fluctuates during scanning, the output signal level of the first attenuator 6 varies depending on the peak level and the lowest level of the captured noise, and as a result, the luminance fluctuation of the display section is suppressed. Occur.

[Problem that the invention seeks to solve]

In the above-mentioned DC regeneration circuit that digitally regenerates DC, the DC regeneration is performed by subtracting the specified clamp code signal from the input digital signal in the first subtracter, so the clamp point may be affected by noise, etc. , the output signal level of the first subtractor changes depending on the level difference between the peak level and the lowest level of the noise. When this fluctuating output signal is visualized, there is a problem that the brightness of the displayed image fluctuates and the displayed temperature pattern becomes unclear.

[Means for solving problems]

The present invention provides a DC reproduction circuit for an infrared imaging device that solves the above-mentioned problems, and its means converts infrared rays emitted from a target object into a digital signal, and defines a reproduction level from the digital signal. In a DC reproduction circuit of an infrared imaging device that performs DC reproduction of the digital signal by subtracting a clamp code signal with a subtracter and displays a temperature pattern of the target object on a display unit, a memory for storing the output signal of the subtracter. A direct current reproducing circuit for an infrared imaging device, which comprises: an average circuit for extracting the average level value of the output signal of the storage section; and another subtracter for subtracting the output signal of the averaging circuit from the digital signal. It will be done.

[Effect]

The DC regeneration circuit of the above-mentioned infrared imaging device adds a second subtracter, a storage section, and an averaging circuit to the conventional DC regeneration circuit, and generates a clamp code generator from a digital signal sequentially inputted by the second subtractor. The output clamp code signal having a predefined clamp level is subtracted to extract the difference for each human-powered digital signal, and after storing one screen worth of the extracted difference signal in the storage section, the average circuit calculates one screen. Detect the average level of the minute difference signal.

This detected average level is input to the first subtractor, and the first
By subtracting the average level from the input digital signal in the subtracter, the human-powered digital signal is digitally clamped at the average level and DC reproduction is performed.

This DC regeneration reduces fluctuations in the output signal level of the first subtracter caused by signal level differences between horizontal scans and noise superimposed on the input signal, thereby reducing brightness changes in the display section.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

Fig. 1 is a block diagram of a DC regeneration circuit of an infrared imaging device according to an embodiment of the present invention, and Fig. 2 is a signal waveform diagram for explaining the operation of the DC regeneration circuit according to an embodiment. Parts are indicated using the same symbols.

As shown in FIG. 1, the DC regeneration circuit of one embodiment has a clamp code outputted from a clamp code generation circuit 7 based on a digital signal sequentially outputted from an A/D converter 5 to a conventional DC regeneration circuit. A second subtraction circuit 11 that subtracts signals to obtain a difference signal, a storage unit 12 that stores one screen worth of difference signals output from the second subtraction circuit 11, and one screen output from the storage unit 12. An averaging circuit 13 is added to detect the average level of the difference signal.

In this operation, a digital signal output from the A/D converter 5 is input to the first subtraction circuit 6 and the second subtraction circuit 11. The second subtraction circuit 11 subtracts the clamp code signal having a predetermined clamp level output from the clamp code generation circuit 7 from the sequentially inputted digital signals, and extracts the difference between each human-powered digital signal. , is output to the storage unit 12. The storage unit 12 stores the sequentially input difference signals for one screen, and then outputs the difference signals for one screen to the averaging circuit 13. The averaging circuit 13 detects the average level of the input difference signal for one screen and outputs it to the first subtracter 6.

The first subtracter 6 subtracts the average level of the difference signal for one screen output from the averaging circuit 13 from the input digital signal, digitally clamps the input digital signal at the average level, and performs DC reproduction. Let's do it. This DC-regenerated input digital signal is displayed as an image on the display section 10 via the image processing section 9.

In other words, by detecting the average level of the difference between the clamp point output code and the clamp code for one screen, the second
As shown in the figure, the signal level difference between horizontal scans and the noise value superimposed on the input signal are averaged, and by clamping the input digital signal at this average level, the signal level difference between horizontal scans and the noise value superimposed on the input signal are averaged. Fluctuations in the clamp point caused by noise superimposed on the input signal are reduced, and changes in brightness of the display section are reduced.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to reduce luminance changes in video display caused by signal level differences between horizontal scans or peak values of noise superimposed on input signals.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a DC regeneration circuit of an infrared imaging device according to an embodiment of the present invention, Fig. 2 is a signal waveform diagram for explaining the operation of the DC regeneration circuit of an embodiment, and Fig. 3 is a conventional FIG. 4, which is a block diagram of an infrared imaging device, is a signal waveform diagram for explaining the operation of a conventional DC regeneration circuit. In the figure, 1 is the target object, 2 is the scanning mirror, 3 is the optical system,
4 is an infrared detector, 5 is an A/D converter, 6 is a first subtracter, 7 is a clamp code generation circuit, 8 is a memory section, 9 is an image processing section, 10 is a display section, and 11 is a second subtractor, 12
13 indicates a storage section, and 13 indicates an average circuit.

Claims (1)

[Claims] Converting infrared rays emitted from the target object into a digital signal, subtracting a clamp code signal that defines a reproduction level from the digital signal using a subtracter to perform DC reproduction of the digital signal, and displaying the temperature pattern of the target object. In the DC reproduction circuit of the infrared imaging device shown in the section, there is provided a storage section for storing the output signal of the subtracter, an averaging circuit for extracting the average level value of the output signal of the storage section, and an averaging circuit for extracting the average level value of the output signal from the storage section. A direct current reproducing circuit for an infrared imaging device, characterized in that it further includes a separate subtracter for subtracting an output signal.