JPH09298688A - Infrared ray image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the distortion of signals accompanying the saturation of an amplifier generated in the case that a large difference is present between the luminance level of an optical system inner surface and the luminance level within a view field with respect to a scanning type infrared ray image pickup device provided with an optical scanning mechanism such as a rotary polygon mirror and a vibration mirror, etc. SOLUTION: The output of an infrared ray detector 4 is distributed into two systems and a first system 14 performs output to a signal switching device 16 as it is without working. A second system 15 outputs average output obtained from the infrared ray detector 4 in a valid scanning area to the signal switching device 16. The signal switching device 16 is controlled by switching signals 20, selects the signals of the first system 14 in the valid scanning area and the signals of the second system 15 in an invalid scanning area and outputs them to a post-amplifier 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared imaging device, and more particularly to a scanning infrared imaging device having an optical scanning mechanism such as a rotating polyhedral mirror or a vibrating mirror.

[0002]

2. Description of the Related Art FIG. 4 showing a conventional scanning infrared image pickup device.
Referring to the block diagram of FIG. 1, infrared rays incident from the imaging space are converted into a parallel light flux by the afocal optical system 1 and then scanned by the two-dimensional optical scanning mechanism 2, and then the infrared ray detector 4 by the imaging optical system 3. It forms an image on the top and detects it.
Since the output of the infrared detector 4 is weak, the preamplifier 5
However, in general, the output obtained from the infrared detector 4 is a large direct-current component with a weak alternating-current component superimposed on it, and this alternating-current component is a component that is particularly significant as a signal. In amplifying the signal of the preamplifier 5, an AC coupling type amplification circuit capable of amplifying only the AC component is used. Here, the amplified output signal is input to the clamp circuit 6, and the reference signal 1
After the necessary DC component is reproduced by 1 and the clamp signal 12 and the unnecessary level is cut, the brightness is adjusted to a brightness suitable for display by another reference signal 13 by the brightness adjusting circuit 7, and the post-amplifier 8 is used. The input signal 9 is amplified and output to the signal processor 10 in the subsequent stage such as a display and an A / D converter.

In such a conventional apparatus, as shown in FIG. 5, the optical scanning mechanism 2 scans the inside of the visual field, that is, the brightness level in the so-called effective scanning area, and the inner surface of the optical system 3, which is so-called invalid. In the case of the input signal 9 having a large difference from the brightness level in the scanning area, most of the dynamic range of the amplifier circuit 8 for amplifying the output signal of the infrared detector is indicated by this brightness difference. There is a problem that the amplifier circuit 8 is saturated and the AC component due to the luminance distribution in the visual field is distorted.

In order to avoid such a problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-239180, a field controllable field diaphragm is arranged so as to cover the entire invalid scanning area, By controlling the brightness level of the field stop to an average brightness level within the field of view, a structure has been proposed in which the brightness difference between the effective scanning region and the ineffective scanning region is reduced. Heating material,
Since a power source, a temperature control circuit, etc. are required, the device becomes large and expensive.

Further, in the conventional device, since the reference signal for reproducing the DC component is generated based on the average brightness in the visual field, an object having an extremely large brightness such as flare (super-high temperature object) in the visual field is generated. ) Is present, there is a problem that the reference signal fluctuates greatly and other parts are not displayed.

In addition to the above-mentioned conventional technique, there have been conventionally proposed some configurations for automatically adjusting the reference signal for reproducing the direct current component and the reference signal for adjusting the brightness according to the brightness level in the visual field. There is.

In the method for automatically adjusting the brightness level of an infrared imaging device disclosed in Japanese Patent Laid-Open No. 56-4020, an object is optically scanned and the object is detected based on a signal from an infrared detection system obtained by this scanning. Of the temperature signal corresponding to the temperature of the temperature signal, obtain a first arithmetic mean value of the minimum value and the maximum value of the temperature signal,
The second average value of the signal portion that is equal to or greater than or equal to the arithmetic average value of is calculated, the difference signal between the second average value and the temperature signal is amplified, and this signal is guided to the display device as a brightness modulation signal. There is.

Referring to FIG. 6 showing such a configuration, as a means for obtaining a differential input of a differential amplifier 35 for automatically adjusting a brightness level, a peak hold circuit 44 for holding a signal of the highest potential level value and a minimum potential are held. The peak hold circuit 45 that holds the signal of the level value, the first and second calculation circuits 47 and 48 that performs the arithmetic mean of the highest potential level and the lowest potential level, the clipper 46, etc. are indispensable components. Therefore, the analog or digital circuit for realizing this is not only extremely complicated, but also there is a drawback that a highly accurate differential input cannot be obtained. In addition, when an ultra-high temperature object is present at one point in the field of view, the mere arithmetic averaging is performed as described above. In some cases, nothing may be displayed. Depending on the intended use of the infrared imaging device, it may be meaningless to install. Further, in the case of observing a low temperature part and a high temperature part, there is a drawback that the function of the clipper must be changed in operation principle.

In the method for extracting the brightness adjusting signal in the infrared image pickup device disclosed in Japanese Patent Laid-Open No. 4-119777, an optical means is inserted in the incident infrared light path during an invalid scanning period in which the image signal of the scanning mirror is invalid. However, the focus of the incident infrared light is forcibly shifted to obtain the brightness adjustment signal.However, in such a configuration, a mechanical system such as a transmissive chopper and a drive mechanism is used, so the device is downsized. In addition to the difficulty in securing a long life, the brightness adjustment signal is obtained from the input signal in the invalid scanning period, not in the effective scanning period, so that the high temperature subject can detect the invalid scanning. When it appears repeatedly within the period, the image brightness during the effective scanning period may decrease.

Further, in the infrared image pickup device disclosed in Japanese Patent Laid-Open No. 6-303485, a digital image is extracted for the purpose of accurately extracting the target when the background is complicated or there is a moving target. Each time the image is updated, the brightness of each pixel is compared with the previous image, means for detecting the amount of brightness change, and a histogram of this amount of brightness change are calculated, and a threshold value is set according to this histogram, Means for binarizing and detecting the target are provided. However, in such a configuration, since the binarized data is obtained by the digital signal processing by the computer, there is no mention of measures for the case where the input signal deviates from the dynamic range of the amplifier which is an analog system.

[0011]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is that the detection signal from the infrared detector does not deviate from the dynamic range of the amplifier at the subsequent stage, and the potential levels of the invalid scanning area and the effective scanning area in the detection signal are detected. An object of the present invention is to provide an infrared imaging device that can accurately display an image even if the difference is large.

Another object of the present invention is to reduce the size of the apparatus by reducing the number of mechanical parts, and to greatly fluctuate the reference signal even if there is a high temperature object having extremely large brightness such as flare in the visual field. In other words, it is an object of the present invention to provide an infrared imaging device that does not display an image in the surrounding area.

Still another object of the present invention is to simplify the circuit structure and obtain a highly accurate differential input (reference signal), wherein the reference signal is not based on the signal of the invalid scanning period of the detection signal, and the analog system is used. An object of the present invention is to provide an infrared imaging device that can be easily designed even in the case of a circuit.

[0014]

In order to solve the above-mentioned problems, the infrared image pickup device of the present invention is a scanning type infrared image pickup device in which a signal of an effective scanning period in a detection signal obtained from an infrared detector is used. A hold signal obtained by performing sample hold based on the above is inserted into an invalid scanning period in the detection signal, and a predetermined level is clamped and then input to an amplifier at a subsequent stage.

Here, a signal switching means for inserting the hold signal only in the invalid scanning period is provided, and the hold signal is used as a reference signal for the clamp.
The smoothed signal of the detection signal is compared with the detection signal or the attenuated detection signal, and when the signal level of the latter becomes large, the start of the sampling is stopped and the level of the previous hold signal is compared. Can be maintained, and the potential level of the hold signal or a temperature value corresponding to the potential level can be inserted in the image.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Referring to the block of FIG. 1 showing a first embodiment of the present invention, in this scanning infrared image pickup device, infrared rays incident from an image pickup space are collimated by an afocal optical system 1. And is scanned by a two-dimensional optical scanning mechanism 2 such as a rotating polyhedral mirror or a vibrating mirror,
An image is formed on the infrared detector 4 by the image forming optical system 3. The output signal from the infrared detector 4 is amplified by the AC-coupling type preamplifier 5, and then the first system 14 and the second system 1
5 and the signals of the first system 14 are input to the signal switch 16 without being processed.

On the other hand, the second system 16 is input to a sample hold circuit 18 for holding and non-holding a signal via a smoothing circuit 17 for smoothing the signal. The signal of the second system 15 output from the sample hold circuit 18 passes through the smoothing circuit 19 again, is input to the signal switcher 16, and is also input to the clamp circuit 12 as a reference signal for DC component regeneration. Is also entered. The output signal of the signal switcher 16 is regenerated by the clamp circuit 6 for direct current, and further, an appropriate reference signal is superposed by the brightness adjusting circuit 7 and input to the post-amplifier 8. The output signal from the post-amplifier 8 is input to a desired signal processor 10 such as a display, an A / D or a converter.

In such a configuration, the sample-hold circuit 18 outputs the smoothed input signal as it is in the effective scanning region by the hold signal 21 and holds the immediately preceding input signal in the invalid scanning region and outputs it. Controlled. Further, the signal switch 16 is
The switching signal 20 is controlled to select and output the signal of the first system 14 in the effective scanning area and the signal of the second system 15 in the invalid scanning area.

Referring to the waveform diagram of FIG. 2 showing the input signal 9 of the post-amplifier 8, the effective scanning area T of the input signal 9 is shown.
The signal of e is supplied to the preamplifier 5 by the signal switcher 16.
Output signal is selected, the DC component is further cut by the clamp circuit 6, and the brightness is adjusted to obtain the signal.
In addition, the signal of the invalid scanning area Tn is the signal switch 16
The output of the smoothing circuit 19 is selected by, is further clamped, and is a signal obtained by adjusting the brightness. This flat level is obtained in the sample hold after smoothing the signal of the immediately preceding effective scanning area Te. The sample period of the sample hold circuit 18 may extend over the entire effective scanning area Te, but is limited to the central area of the area Te.
This is more preferable for accurately measuring the target subject.

As shown in FIG. 5, the signal in the conventional general scanning infrared image pickup device is dominated by the brightness difference, and most of the signal amplitude is due to the brightness difference. If the dynamic range is exceeded, not only the target AC signal due to the brightness distribution in the visual field is distorted but also brightness may not be displayed. However, according to this embodiment, the post-amplifier is used. Since the dynamic range of 8 can be effectively used, the above-mentioned problem is solved.

Further, since the level of the invalid scanning area Tn is not based on the output signal of the preamplifier 5 obtained during this period, but is based on the signal within the effective scanning area Te, it is temporarily invalid. Even if the input signal in the scanning region Tn has a high-luminance portion or a low-luminance portion, it is not affected at all. That is, the brightness during image display is not affected by the subject during the time when the image is not displayed.

Referring to the block diagram of FIG. 3 showing the second embodiment of the present invention, the present imaging apparatus additionally includes an attenuator 22, a comparator 23, and an AND circuit 25 in addition to the block of FIG. The description of the operation of the circuit that is the same as that of the first embodiment is omitted.

In the present embodiment, the output of the preamplifier 5 is input to the signal switch 16 and the smoothing circuit 17 and also to the attenuator 22, for example, 2 here.
It is output after being attenuated by a factor of 1. The output of the attenuator 22 is
The output of the smoothing circuit 19 is compared by the comparator 23,
When the output of the attenuator 22 is larger, it is estimated that there is a high-intensity object locally, so the sample hold circuit 18 controls so as to output the hold signal 27 that holds the immediately preceding input signal. . That is, it is possible to prevent an extreme output fluctuation of the smoothing circuit 19 which occurs when there is a high-luminance object due to interference such as flare in a part of the visual field. Here, the hold signal 24 prevents the sample and hold circuit 18 from sampling again, so that the input signal 9 is formed based on the previous input signal (the input signal one cycle before). Here, the signal before smoothing and the signal after smoothing are compared by the comparator 23.
Are compared.

When there is an ultra-high brightness object in a part of the external space due to flare interference, the output of the sample hold circuit 18 used for the clamp voltage may fluctuate. It can be easily avoided by the principle shown in. The signal of the amplifier 5 is attenuated by the attenuator 22, for example, halved, and the signal of the second system is compared by the comparator 23. When the output of the attenuator 22 is larger,
That is, when the optical scanning system scans a space having an extremely large brightness as compared with the average brightness in the external space, the sample hold circuit 18 controls so as to hold the immediately preceding signal.

According to the first and second embodiments described above, the output level of the sample hold circuit 18 or the smoothing circuit 19 is introduced into the signal processor 10, and the output level value is set at one corner of the image, for example. Alternatively, by displaying a temperature value corresponding to this output level value, it becomes possible to directly read how much temperature bias is added to the display image.
Although any smoothing circuit 19 is provided, it is possible to operate without it.

[0026]

As described above, according to the infrared imaging apparatus of the present invention, the average output obtained from the infrared detector is amplified and used as the reference signal in the effective scanning area in the invalid scanning area. Even if there is a large difference between the brightness level in the field of view and the brightness level on the inner surface of the optical system, the dynamic range of the amplifier can be used effectively, and the size and cost of the device increases with the addition of optical components. It is possible to prevent the saturation phenomenon of the amplifier, and to prevent the fluctuation of the reference signal for DC reproduction that occurs when there is an interference such as flare in the field of view by adding a simple circuit. ,
The above-mentioned objects of the present invention are achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of an infrared imaging device according to the present invention.

FIG. 2 is a waveform diagram showing an input signal of the post-amplifier shown in FIG.

FIG. 3 is a block diagram showing a second embodiment of an infrared imaging device according to the present invention.

FIG. 4 is a block diagram showing an example of a conventional scanning infrared imaging device.

FIG. 5 is a waveform diagram showing an input signal of a conventional post-amplifier.

FIG. 6 is a block diagram showing another example of a conventional imaging device.

[Explanation of symbols]

 1 Afocal optical system 2 Optical scanning mechanism 3 Imaging optical system 4 Infrared detector 5 Preamplifier 6 Clamp circuit 7 Brightness adjusting circuit 8 Post-amplifier 9 Input signal 10 Signal processor 14, 15 System 16 Signal switcher 17, 19 smoothing circuit 18 sample hold circuit 22 attenuator 23 comparator 25 AND circuit 35 differential amplifier 44, 45 peak hold circuit 46 clipper 47, 48 arithmetic mean calculation circuit 49 hold circuit

Claims (5)

[Claims] 1. A scanning type infrared image pickup device, wherein a hold signal obtained by performing sample hold based on a signal of a valid scanning period in a detection signal obtained from an infrared detector is used as an invalid scan in the detection signal. An infrared imaging device characterized by being inserted into a period and being clamped to a predetermined level before being input to an amplifier in a subsequent stage. 2. The infrared imaging device according to claim 1, further comprising a signal switching unit that inserts the hold signal only in the invalid scanning period. 3. The infrared imaging device according to claim 1, wherein the hold signal is used as a reference signal for the clamp. 4. The smoothed signal of the detection signal is compared with the detection signal or the attenuated detection signal, and when the latter signal level becomes high, the start of the sample is stopped and the sampling is stopped. The infrared image pickup device according to claim 1, wherein the level of the hold signal is maintained. 5. The infrared imaging device according to claim 1, wherein a potential level of the hold signal or a temperature value corresponding to the potential level is inserted into an image.