JPS5849068B2 - Image processing method and device for pyroelectric imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image processing method and device for a pyroelectric imaging device, and more particularly, to an image processing method and device for a pyroelectric imaging device, and more specifically, it is capable of improving the signal-to-noise ratio and accurately capturing temperature changes of an object to be measured. This invention relates to an improved image processing method and apparatus.

A pyroelectric image pickup tube, which uses the pyroelectric phenomenon to produce infrared images, uses electron beam scanning to extract changes in the amount of charge due to time changes in the temperature of a pyroelectric target due to incident infrared rays, using a normal television scanning method to create television images. It is to be reproduced as a.

As mentioned above, this pyroelectric image pickup tube absorbs thermal radiation from outside the object to be measured and reads out the charge generated according to the rate of temperature change of the pyroelectric target by scanning the electron beam, so it does not stand still. , and when imaging an object whose temperature has not changed, move the object to be measured, the camera itself, or the optical system between the object and the camera so that the same radiation stays at the same position on the pyroelectric target for a long time. It is necessary to prevent the radiation from being hit or to interrupt the radiation over time using rotating blades, shutters, etc.

In this case, if the temperature distribution of a stationary object is visualized as is on a television receiver, in the former case, the measured object moves, and in the latter case, a positive polarity signal and a negative polarity signal appear alternately, making it extremely difficult to observe. It has the disadvantage of being difficult to do.

In order to avoid this drawback, it is possible to record the video signal from a pyroelectric image pickup tube with a video tape recorder, etc., and then observe it by playing back still images, but such still images have a low signal-to-noise ratio. It is small and difficult to distinguish as a temperature pattern even if it is reproduced as is on a television receiver.0 For this reason, in the past, the signal-to-noise ratio was improved by superimposing video signals at the signal repetition period.

That is, in general, if the signal is a repetitive signal and the noise is white noise, if this video signal is superimposed N times in the signal repetition period, the signal will be multiplied by N and the noise will be multiplied by F. That is, the signal-to-noise ratio is N/J
The signal-to-noise ratio was improved by utilizing the property that Fr = J''H times.

Hereinafter, a conventionally used pyroelectric imaging device will be described in detail with reference to the drawings.

FIG. 1 shows an overall configuration diagram of a pyroelectric imaging device.

Below, a conventional image processing method will be explained based on FIG. 1. In FIG. , is converted into an electrical signal by the pyroelectric image tube camera 104.

At this time, the radiation image is closed by the shutter 103 every other frame period.

Further, the shutter drive circuit 105 is connected to the pyroelectric image tube camera 1.
A vertical synchronizing signal is extracted from the deflection circuit 04, and the shutter 103 is opened and closed by this vertical synchronizing signal.

After the video signal from the camera 104 is amplified to the required voltage by the amplifier 106, the memory control circuit 107 stores it in an analog memo IJ-108 consisting of a capacitor, a charge-coupled device, etc. in units of frames for each pixel. be done.

When this operation is repeated by operating the memory control circuit using the vertical synchronization signal from the deflection circuit of the camera 104 during a plurality of frame periods when the shutter 103 is open, the analog memo IJ-108 has the following effects due to the superimposition effect:
An amplified video signal with an improved signal-to-noise ratio is obtained by superposition.

This video signal is sent to the television receiver 109 for monitoring.
The image is displayed on the television receiver 109 under the control of the memory control circuit 107, but normally the image is not displayed on the television receiver 109 during the period when writing to the analog memo IJ-108 is being performed, so a separate At the same time as the image is displayed, writing is performed on the analog memo IJ-110, and during the writing period to the analog memo 'J-108, the same signal is continuously read from the analog memory 110 provided separately, so that the image on the monitor stops. This prevents flickering or flickering.

Next, the recording method to the analog memo IJ-108 will be explained in more detail based on FIGS. 2, 3, and 4. As shown in FIG.
3, the video signal 301 during one horizontal scanning period is sampled by the clock pulse 302 from the memory control circuit 107 as shown in FIG.
As shown in 03, the video signal for each pixel is extracted as an analog quantity.

Sampling is performed every horizontal scanning period as shown in FIG. 4, and the sampled video signal for one frame is stored in the analog memory 108 according to the address signal of the memory control circuit 107.

Here, 401 is a vertical synchronization signal, and 402 is a horizontal synchronization signal.

Note that the video signal of the next frame is sampled in the same way, and is superimposed on the already stored signal of the previous frame.

That is, for example, when the signals of the n-th pixel on the m-th horizontal scanning line are superimposed as shown in FIG. 2, the counter built into the memory control circuit 107 is first After clearing with the vertical synchronization signal 401, the number of horizontal synchronization signals 402 is counted and the m-th horizontal scanning period is extracted.

Next, in the extracted mth horizontal scanning period, another counter is cleared by the horizontal synchronization signal 402, the number of clock pulses 302 is counted, and the nth sampled video signal is extracted, and the already stored frame is Signals are input to the memory at the location of the n-th pixel 202 on the m-th scanning line and are superimposed.

By performing the same processing as described above while changing the numbers of m and n, all pixels on the video 201 for one frame period can be superimposed.

The disadvantage of the conventional signal processing method explained above is that when the surface temperature of the object to be measured changes over time, if the number of superimposed frames is too large, the temperature changes will be averaged, so The image displayed on the John receiver 109 differs from the actual temperature distribution.

Furthermore, if the number of frames to be superimposed is reduced in order to avoid this, the signal-to-noise ratio cannot be improved.

The present invention solves the above-mentioned drawbacks and provides an image processing method and apparatus that have an excellent signal-to-noise ratio and can accurately follow temperature changes of an object to be measured.

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

In the following drawings, parts having the same functions as those in FIG. 1 are given the same numbers and explanations are omitted.

FIG. 5 is an overall configuration diagram of a pyroelectric imaging device using the image processing method according to the present invention.

In the figure, among the video signals amplified by the amplifier 106, the first frame signal is directly input to the analog memo IJ-108 through a line 504.

On the other hand, signals from the second frame onward of the video signal are processed by the multiplier 5.
After being multiplied by a/b by 01, it is applied to the adder 503.

Note that a < b here.

On the other hand, the output of the analog memory 108 is sent to the television receiver 109 and simultaneously sent to the multiplier 502, multiplied by c/d, and then added to the output of the multiplier 501 by the adder 503. Added analog memo I
J-108.

At this time, if you choose integers a, b, c, and d so that a / b + c / d - 1, the analog memo IJ-108
will always store a signal of the same magnitude as the input signal.

Here, for example, let a-c=1, b=d=2, the signal of the first frame is F1, and the signal of the next frame is F2.
When the nth frame signal is Fn, the output of the nth frame of the analog memory 108 is as follows.The signal-to-noise ratio is improved by superimposition, and at the same time, the signal of the newer frame is stronger in time, and the signal of the older frame is stronger. Since the signal becomes weaker, it is possible to accurately follow the temporally changing surface temperature of the object to be measured.

Note that the first frame signal is directly input to the analog memo IJ-108 because it is input to the analog memo IJ-108 through the multiplier 501 and the amplifier 10
This is to prevent the output from being applied to the television receiver 109 to be weaker than when the output No. 6 is directly applied to the television receiver 109.

In the above explanation, a = c = 1, b = d = 2, but if the values of a, b, c, and d are changed under the conditions described above, the relative weight of the new signal and the old signal can be changed. can be changed to any value.

Next, we will discuss an example in which a digital memory is used instead of an analog memory, the obtained video signals are divided into classes according to the signal strength, and the colors are matched to display infrared video in color. explain.

FIG. 6 shows a signal processing circuit for color display. In the figure, a video signal amplified to the required voltage by an amplifier 106 is converted into a digital signal by an A-D converter 601. After that, the same signal processing as in the case of analog memory is applied to the digital memory 602.
is memorized.

Note that here, the multipliers 501, 502 and the adder 503 have all been replaced with ones for digital signal processing.

The output signal of the digital memory 602 is converted by the color matrix circuit 603 into signals of three colors, for example, red, blue, and green, or a combination of these colors, according to the signal size, that is, the intensity of the temperature, and then the output signal is displayed on a color television. john receiver 60
It will be shown on 4.

In the embodiment described above, the shutter is closed during every other frame period, but depending on the pyroelectric material used for the target, the response speed may not be very fast. For example, when using lead titanate as the target material, When used in this case, the apex peak, that is, the point at which the amount of generated charge is maximum, appears 8 to 12 frames after the shutter is opened.

Therefore, when using pyroelectric materials with slow response speed,
By extracting about 10 frames around which the amount of charge generated is the maximum, reading the signal only during this frame period, and not reading the signals during other periods when the amount of charge is small and the period when the shutter is closed, the signal pair of the image reception signal will be reduced. It is possible to obtain a high noise ratio and a temperature pattern with high sensitivity.

As explained above, the present invention provides a pyroelectric imaging device that includes:
By using a new image processing method that is different from the conventional method of improving the signal-to-noise ratio, it is possible to achieve a good signal-to-noise ratio even when the surface temperature of the measured object changes over time. This makes it possible to provide a high-performance pyroelectric imaging device that can accurately track the image.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional pyroelectric imaging device, FIGS. 2, 3, and 4 are explanatory diagrams of an image processing method in the device of FIG. 1, and FIGS. 5 and 6 are diagrams of the present invention. 1 is a block diagram of a pyroelectric imaging device according to an embodiment of the present invention. 101...Object to be measured, 102...Optical system, 103...Shutter, 104...
...Pyroelectric image pickup tube, 105...Shutter drive circuit, 106...Amplifier, 107...Memory control circuit, 108, 110...Analog memory, 109...Television receiver, 2
01... 1 frame image, 202...
・Pixel, 301...Video signal during horizontal scanning period, 302...Clock pulse, 303...
...Sampled video signal, 401...
Vertical synchronization signal, 402...Horizontal synchronization signal, 50
1 ,502... Multiplier, 503...
Adder, 504... Line, 601...
A-D converter, 602...Digital memory,
603...Color matrix circuit, 604...
...Color television receiver.

Claims (1)

[Claims] 1. An infrared video signal from a subject is read out intermittently at a constant cycle, and the video signal read out from the second cycle onwards is multiplied by a first ratio to obtain a first signal. The signal read out in the first cycle is used as a second signal to be applied to the image display section,
A portion of the second signal is multiplied by a second ratio whose sum with the first ratio is 1, and then added to the first signal to obtain a third signal; An image processing method for a pyroelectric imaging device, characterized in that: is used as the second signal. 2. An image processing method for a pyroelectric imaging device according to claim 1, wherein the fixed period is one frame period. 3. A pyroelectric imaging camera that intermittently captures infrared images from a subject at a fixed cycle, and a first camera that multiplies the signal from the second period onward of the infrared image from this pyroelectric imaging camera by a/b (a<b). a multiplier, a memory to which the first cycle signal of the infrared image is supplied, and an output of this memory (1 a/
b) An image processing device for a pyroelectric imaging device, comprising: a second multiplier that multiplies the multiplier; and an adder that adds the outputs of the first and second multipliers and applies the result to the memory.