JPH09233389A - Infrared ray image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared ray image pickup device which is capable of displaying a target object to be an object on a screen with stable brightness, even when the background object having a high temperature and the background object having a low temperature exist at the parts of the screen. SOLUTION: The digital video signal outputted from a correction processing circuit 6 is transmitted to a histogram calculation circuit 10 and the histogram of the digital video signal is calculated. Next, the median of the obtained historam is calculated in a histogram median calculation circuit 11. Further, a DC level is controlled so that the median of the obtained histogram may be always a stipulated value in a DC level control part 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to video level control of an infrared imaging device using an infrared solid-state imaging device.

[0002]

2. Description of the Related Art FIG. 9 is a diagram showing an embodiment using a conventional level control method. Reference numeral 1 denotes an infrared optical system for focusing infrared rays to form an image, 2 is an infrared solid-state image sensor for photoelectrically converting the infrared rays focused by the infrared optical system 1 into an electric signal, and 3 is an output of a DC level subtractor 4. A low-pass filter that transmits only low-frequency components and extracts a DC level, 4 is a DC level subtractor that subtracts the output of the low-pass filter 3 from the output of the infrared solid-state image sensor 2, and 5 is an analog output of the DC level subtractor 4. A / D converter for converting a signal to a digital signal, 6 a correction processing circuit for performing correction processing on the output of the A / D converter and converting it to a digital video signal, 7 a digital video output from the correction processing circuit A D / A converter for converting the signal into a display analog video signal, 8 is a control signal generating circuit for generating various control signals, 9
Is a display monitor for displaying the obtained infrared image.

In general, imaging in the infrared band has a much smaller contrast than imaging in the visible band, and due to dark current generated by the thermal energy of the device itself, the output obtained by the infrared solid-state imaging device 2 has many DC components. Is output including. Therefore, if the input dynamic range of the A / D converter is sufficiently wide, such as when the gain of the circuit system is small, the infrared imaging device can be configured with a simple configuration by performing A / D conversion and correction processing as it is. it can. However, in the conventional infrared imaging device, in order to image a target with better contrast, the gain of the circuit system, that is, the sensitivity is increased even if the input dynamic range of the A / D converter is sacrificed. . Conventionally, as shown in FIG. 9, D of the output of the infrared solid-state image sensor 2 is used.
The C component is detected by the low-pass filter 3 and then fed back, and the DC level subtractor 4 is used to detect the infrared solid-state image sensor 2
It is possible to automatically subtract the DC component of (4) and store it within the input dynamic range of the A / D converter 5 in a stable manner. Further, the output of the A / D converter 5 is converted into a digital video signal by the correction processing circuit 6, and converted into an analog video signal by the D / A converter 7 for displaying on the display monitor 9.

[0004]

Since the conventional infrared ray image pickup device is constructed as described above, it is possible to see an image with stable brightness on the entire screen, but it is possible to see the image especially on the screen. If there is a target object to be displayed and there is a high-temperature background or a low-temperature background near the edge of the screen or the target object, the brightness of the entire screen is excessively or under-induced by the high-temperature background and the low-temperature background. The brightness of the target object cannot be adjusted, and in some cases, the level of the target object exceeds the input dynamic range of the A / D converter and is saturated with a white level or a black level, which does not appear on the screen. was there.

The present invention provides an infrared image pickup device capable of displaying on a screen with stable brightness to a target object of interest even if there is a high temperature background object or a low temperature background object near the edge of the screen or the target object. The purpose is to

[0006]

According to the first invention, a histogram of a digital video signal output from a correction processing circuit is calculated, and a median value of the obtained histogram is calculated. A means for controlling the DC level output to the DC level subtractor is used so that the calculated median value of the histogram always becomes a certain prescribed value.

In the second invention, the histogram of the digital video signal output from the correction processing circuit is calculated, and the median value of the histogram is calculated within the designated area. The means for controlling the DC level output to the DC level subtractor is used so that the median value of the histogram is always a certain prescribed value within the designated area.

According to the third aspect of the invention, after the histogram of the digital video signal output from the correction processing circuit is calculated, the histogram is corrected by the set upper and lower limits of brightness. Further, the average value of the corrected histogram is calculated, and D is adjusted so that the average value is always a certain prescribed value.
The means for controlling the DC level output to the C level subtractor is used.

According to the fourth aspect of the invention, after calculating the histogram of the digital video signal output from the correction processing circuit, the histogram is corrected by the set upper and lower limits of brightness. Further, a means for calculating the average value of the corrected histogram in the designated area and controlling the DC level output to the DC level subtractor so that the average value always becomes a certain prescribed value is used. .

Further, in the fifth invention, in order to correct the level control contribution near the black level or the white level,
An A / D converter for directly A / D converting the output of the infrared solid-state image sensor through an amplifier, a histogram of a digital signal output from the A / D converter, and a black level correction table,
The histogram is converted using the white level correction table. Further, a means for calculating the average value of the converted histogram, outputting the calculated average value of the histogram to the DC level subtractor as it is, and controlling the DC level is used.

In the sixth aspect of the invention, in order to correct the level control contribution near the black level or the white level,
An A / D converter for directly A / D converting the output of the infrared solid-state image sensor through an amplifier, a histogram of a digital signal output from the A / D converter, and a black level correction table,
The histogram is converted using the white level correction table. Further, a means for controlling the DC level by calculating the average value of the converted histogram in the designated area, outputting the calculated average value of the histogram in the area to the DC level subtractor as it is, is used.

[0012]

First Embodiment FIG. 1 is a diagram showing a first embodiment of the present invention.
Is a histogram calculation circuit for calculating a histogram for one frame, 11 is a histogram median value calculation circuit for calculating the median value of the histogram with respect to the output of the histogram calculation circuit 10, and 12a is output from the histogram median value calculation circuit 11. It is a DC level control unit that controls the DC level so that the median value of the histogram always becomes a prescribed value. In FIG. 1, the digital video signal output from the correction processing circuit 6 is a histogram calculation circuit 10
The output distribution for one frame is calculated. Further, the median value of the histogram is calculated by the histogram median value calculation circuit 11, and then the first DC level control unit 12a subtracts the DC level so that the output of the histogram median value calculation circuit 11 always becomes a prescribed value. The DC level set in the container 4 is controlled. The output from the DC level subtractor 4 is A / D converted by the A / D converter 5 as in the conventional processing.
It is converted and supplied for further processing.

Second Embodiment FIG. 2 is a diagram showing a second embodiment of the present invention.
Is an area designation generation circuit that designates a processing area used for level control, and 14 is an output of the histogram calculation circuit 10.
It is an in-area histogram median value calculation circuit for calculating the median value of the histogram in the area specified by the area specification generation circuit 13. In FIG. 2, the digital video signal output from the correction processing circuit 6 is passed through the histogram calculation circuit 10 and the output distribution for one frame is calculated.
Further, the median value of the histogram in the area designated by the area designation generating circuit 13 is calculated by the intra-area histogram median value calculating circuit 14, and then, in the first DC level control unit 12a, the median histogram value within the area is always calculated. The DC level subtractor 4 so that the output of the calculation circuit 14 becomes a specified value.
Control the DC level set to. DC level subtractor 4
The output from is A / D converted by the A / D converter 5 in the same manner as the conventional processing, and is supplied to the subsequent processing.

Third Embodiment FIG. 3 is a diagram showing a third embodiment of the present invention, FIG. 4 is a diagram for explaining details of histogram shape conversion in the embodiment of the present invention, and 12b is a histogram average value calculation. A second DC level control unit for controlling the DC level set in the DC level subtractor 4 so that the output of the circuit 18 is always a specified value, and 15 is a brightness upper limit setting circuit for setting the upper limit of brightness to be calculated. , 16 is a brightness lower limit value setting circuit for setting a lower limit value of brightness to be calculated, 17 is a histogram shape conversion circuit for receiving the outputs of the brightness upper limit value setting circuit 15 and the brightness lower limit value setting circuit 16, and converting a histogram, 18 Is a histogram average value calculation circuit for calculating the average value of the corrected histogram output from the histogram shape conversion circuit 17. In FIG. 3, the digital video signal output from the correction processing circuit 6 is passed through the histogram calculation circuit 10 and the output distribution for one frame is calculated. Brightness upper limit value setting circuit 15 and brightness lower limit value setting circuit 16
The upper and lower limits are set in advance. The histogram shape conversion circuit 17 converts the histogram according to the outputs of the brightness upper limit value setting circuit 15 and the brightness lower limit value setting circuit 16. For example, as shown in FIG.
The histograms exceeding the upper limit value set in 5 and below the lower limit value set in the luminance lower limit value setting circuit 16 are set to zero, and the histograms are corrected. Then, the histogram average value calculation circuit 18 receives the output of the histogram shape conversion circuit 17 and calculates the average value of the converted histogram. Further, the second DC level control unit 12b controls the DC level set in the DC level subtractor 4 so that the output of the histogram average value calculation circuit 18 always becomes a prescribed value. The output from the DC level subtractor 4 is A / D converted by the A / D converter 5 as in the conventional processing.
It is converted and supplied for further processing.

Fourth Embodiment FIG. 5 is a diagram showing a fourth embodiment of the present invention.
Is an in-area histogram average value calculation circuit for calculating an average value in the specified area of the converted histogram output from the histogram shape conversion circuit 17. In FIG. 5, the digital video signal output from the correction processing circuit 6 is passed through the histogram calculation circuit 10 and the output distribution for one frame is calculated. Brightness upper limit value setting circuit 15,
An upper limit value and a lower limit value are set in advance in the brightness lower limit value setting circuit 16. The histogram shape conversion circuit 17 converts the histogram according to the outputs of the brightness upper limit value setting circuit 15 and the brightness lower limit value setting circuit 16. After that, the in-region histogram average value calculation circuit 19 receives the outputs of the histogram shape conversion circuit 17 and the region designation generation circuit 13, and calculates the average value of the in-region histogram. Further, the second
The DC level control unit 12b controls the DC level set in the DC level subtractor 4 so that the output of the in-region histogram average value calculation circuit 19 is always a specified value.
The output from the DC level subtractor 4 is A as in the conventional processing.
It is A / D converted by the / D converter 5 and supplied to the subsequent processing.

Fifth Embodiment FIG. 6 is a diagram showing a fifth embodiment of the present invention, and FIG.
FIG. 5 is a diagram for explaining the details of histogram shape conversion in the embodiment of the present invention, and 5b is a second A / D for converting the output of the infrared solid-state image sensor 2 from an analog signal to a digital signal via the amplifier 20. The converter 12c receives the output of the histogram average value calculation circuit 18, sets the value as it is in the DC level subtractor 4, and controls the DC level by a third DC level controller 17a and the black level correction table 21. Is multiplied by the output of the histogram calculation circuit 10 to correct the histogram in the black direction, and 17b is the output of the white level correction table 22 and the first histogram shape conversion circuit 17a. A second histogram shape conversion circuit that multiplies the outputs and corrects the histogram in the white direction, 20 is an infrared solid-state image sensor Amplifier for amplifying an output of 21 black level correction table for determining a correction amount of the black level direction,
A white level correction table 22 determines a correction amount in the white level direction. In FIG. 6, the output of the infrared solid-state imaging device 2 is directly output via the amplifier 20 to the second A / D converter 5
It is converted into a digital signal by b. The digital signal output from the second A / D converter 5b is passed through the histogram calculation circuit 10 and the output distribution for one frame is calculated. The black level correction table 21 and the white level correction table 22 store in advance correction data indicating contributions related to histogram conversion in each direction. Histogram shape conversion circuit 17a and histogram shape conversion circuit 17b
Then, the histogram output from the histogram calculation circuit 10 and the outputs of the black level correction table 21 and the white level correction table 22 are received, calculation is performed, and the histogram is converted. For example, first, in the black level correction table 21, the correction value α _Y as shown in FIG.
Is stored. Next, the calculation of "Equation 1" is performed for all the brightness values Y to convert the brightness values. After that, a histogram is calculated for the converted luminance value Y ′. As a result, the corrected histogram is slightly shifted to the white side as shown in the range of black levels Y ′ b1 to Y ′ b2 in FIG. 7C. Next, the white level correction table 22 stores a correction value β _Y ′ as shown in FIG. 7D in advance. Next, the calculation of "Equation 2" is performed on all the luminances Y'to convert the luminance values. Then, a histogram is calculated for the converted luminance value Y ″. As a result, the corrected histogram is shown in FIG.
As shown in the range of Y ″ w2, it is shifted slightly to the black side. Therefore, according to "Equation 3", the range of the black levels Yb1 to Yb2 shown in FIG. 7A corresponds to the range of the black levels Y ″ b1 to Y ″ b2 shown in FIG. The range of black levels Yw1 to Yw2 shown in FIG. 7 is shifted to the range of white levels Y ″ w1 to Y ″ w2 shown in FIG. Thereafter, the histogram average value calculation circuit 18 receives the output of the second histogram shape conversion circuit 17b and calculates the average value of the converted histogram. Thereafter, the histogram average value calculation circuit 18 receives the output of the second histogram shape conversion circuit 17b and calculates the average value of the converted histogram. In the third DC level control unit 12c, the output of the histogram average value calculation circuit 18 is directly set in the DC level subtractor 4 to control the DC level.

[0017]

[Equation 1]

[0018]

[Equation 2]

[0019]

(Equation 3)

Sixth Embodiment FIG. 8 is a diagram showing a sixth embodiment of the present invention. In FIG. 8, the output of the infrared solid-state image sensor 2 is directly converted into a digital signal by the second A / D converter 5b via the amplifier 20. The digital signal output from the second A / D converter 5b is passed through the histogram calculation circuit 10 and the output distribution for one frame is calculated. In the black level correction table 21 and the white level correction table 22, correction data indicating level control contributions in each direction are stored in advance. In the histogram shape conversion circuit 17a and the histogram shape conversion circuit 17b, the histogram output from the histogram calculation circuit 10 and the black level correction table 2
1. The output of the white level correction table 22 is received, the calculation is performed, and the histogram is converted. Then, the in-region histogram average value calculation circuit 19 receives the output of the second histogram shape conversion circuit 17b and calculates the average value of the converted histograms in the designated region. In the third DC level control unit 12c, the output of the in-region histogram average value calculation circuit 19 is directly applied to the DC level subtractor 4
To control the DC level.

[0021]

According to the first aspect of the present invention, by calculating the median value of the histogram and controlling the DC level so that the median value is always a prescribed value, a high-intensity object of a part of the screen or a low brightness object is displayed. Suppresses the level induction by the brightness object
Stable level control can be performed on the screen.

According to the second aspect of the invention, the median value of the histogram in the designated area is calculated, and the DC level is controlled so that the value is always a prescribed value in the designated area. It is possible to suppress level induction by an external high-luminance object or low-luminance object and perform stable level control within the area.

According to the third aspect of the invention, the brightness upper limit value,
Using the lower limit value, after correcting the histogram, calculate the average value, and by performing level control, suppress the induction of the level by a high-luminance object in the screen with a relatively high frequency distribution, or a low-luminance object, Stable level control can be performed on the screen.

According to the fourth aspect of the invention, the brightness upper limit value,
By correcting the histogram using the lower limit value, calculating the average value, performing level control, and further limiting the area, a high-luminance object or a low-luminance object with a relatively high frequency distribution outside the specified area can be used. Suppresses level induction,
Stable level control can be performed within the area.

According to the fifth invention, the amplifier and the second
Since the calculated average value of the histogram can be directly set in the DC level subtractor by using the A / D converter, the feedback control need not be used, and stable level control can be performed by a simple method. In addition, it is possible to suppress level induction by a high-luminance object or a low-luminance object in the screen.

According to the sixth invention, the amplifier and the second
Since the calculated histogram average value can be directly set in the DC level subtractor by using the above A / D converter, it is not necessary to use feedback control and stable level control can be performed by a simple method. Further, by limiting the area, it is possible to suppress the level guidance by the high brightness object or the low brightness object outside the specified area.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram illustrating details of histogram shape conversion according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a fifth embodiment of the present invention.

FIG. 7 is a diagram illustrating details of histogram shape conversion according to the fifth embodiment of the present invention.

FIG. 8 is a diagram showing a sixth embodiment of the present invention.

FIG. 9 is a diagram showing a conventional example.

[Explanation of symbols]

 1 infrared optical system 2 infrared solid-state image sensor 3 low-pass filter 4 DC level subtractor 5 A / D converter 6 correction processing circuit 7 D / A converter 8 control signal generator 9 display monitor 10 histogram calculation circuit 11 histogram median value calculation Circuit 12 DC level control unit 13 Area designation generation circuit 14 Area histogram median value calculation circuit 15 Brightness upper limit value setting circuit 16 Brightness lower limit value setting circuit 17 Histogram shape conversion circuit 18 Histogram average value calculation circuit 19 Area histogram average value calculation circuit 20 Amplifier 21 Black level correction table 22 White level correction table

Claims (6)

[Claims] 1. An infrared optical system that collects infrared rays emitted from an object, an infrared solid-state image sensor that detects infrared rays and performs photoelectric conversion, and a DC output from the infrared solid-state image sensor.
A DC level subtractor for removing a component, and A for converting an analog signal output of the DC level subtractor into a digital signal
A / D converter and the output of the A / D converter are corrected,
A correction processing circuit for converting into a digital video signal, a D / A converter for converting the digital video signal output of the correction processing circuit into an analog video signal, a control signal generation circuit for generating various control signals, and a video display. A display monitor; a histogram calculation circuit for calculating a histogram for one frame for the output of the correction processing circuit; a histogram median value calculation circuit for calculating the median value of the histogram for the output of the histogram calculation circuit; A first value that controls the value output to the DC level subtractor so that the output of the median value calculation circuit is always a specified value
Infrared image pickup device, comprising: 2. An infrared optical system that collects infrared rays emitted from an object, an infrared solid-state image sensor that detects infrared rays and performs photoelectric conversion, and a DC output from the infrared solid-state image sensor.
A DC level subtractor for removing a component, and A for converting an analog signal output of the DC level subtractor into a digital signal
A / D converter and the output of the A / D converter are corrected,
A correction processing circuit for converting into a digital video signal, a D / A converter for converting the digital video signal output of the correction processing circuit into an analog video signal, a control signal generation circuit for generating various control signals, and a video display. A display monitor, a histogram calculation circuit that calculates a histogram for one frame for the output of the correction processing circuit, an area designation generation circuit that limits the processing area, and a designation for the output of the histogram calculation circuit by the area designation generation circuit A histogram area median value calculating circuit for calculating the median value of the histogram in the selected area, and a value for controlling the value output to the DC level subtractor so that the area histogram median value calculating circuit always has a prescribed value. 1. An infrared imaging device comprising a DC level control unit No. 1. 3. An infrared optical system for condensing infrared rays emitted from an object, an infrared solid-state image sensor for detecting infrared rays and performing photoelectric conversion, and a DC output from the infrared solid-state image sensor.
A DC level subtractor for removing a component, and A for converting an analog signal output of the DC level subtractor into a digital signal
A / D converter and the output of the A / D converter are corrected,
A correction processing circuit for converting into a digital video signal, a D / A converter for converting the digital video signal output of the correction processing circuit into an analog video signal, a control signal generation circuit for generating various control signals, and a video display. A display monitor, a histogram calculation circuit that calculates a histogram for one frame for the output of the correction processing circuit,
A brightness upper limit value setting circuit for setting a brightness upper limit value to be calculated, a brightness lower limit value setting circuit for setting a brightness lower limit value, an output of the histogram calculation circuit, the brightness upper limit value setting circuit, and the brightness lower limit value. A histogram shape conversion circuit that receives the output of the setting circuit and performs a correction operation, a histogram average value calculation circuit that calculates the average value of the histogram with respect to the output of the histogram shape conversion circuit, and an output of the histogram average value calculation circuit. An infrared imaging device, comprising: a second DC level control unit that controls a value output to the DC level subtractor so that the value always becomes a prescribed value. 4. An infrared optical system for condensing infrared rays emitted from an object, an infrared solid-state image sensor for detecting infrared rays and performing photoelectric conversion, and a DC output from the infrared solid-state image sensor.
A DC level subtractor for removing a component, and A for converting an analog signal output of the DC level subtractor into a digital signal
A / D converter and the output of the A / D converter are corrected,
A correction processing circuit for converting into a digital video signal, a D / A converter for converting the digital video signal output of the correction processing circuit into an analog video signal, a control signal generation circuit for generating various control signals, and a video display. A display monitor, a histogram calculation circuit that calculates a histogram for one frame for the output of the correction processing circuit,
A brightness upper limit value setting circuit for setting a brightness upper limit value to be calculated, a brightness lower limit value setting circuit for setting a brightness lower limit value, an output of the histogram calculation circuit, the brightness upper limit value setting circuit, and the brightness lower limit value. A histogram shape conversion circuit that receives an output of the setting circuit and performs a correction operation, an area designation generation circuit that limits a processing area, an output of the histogram shape conversion circuit and an output of the area designation generation circuit,
An in-region histogram average value calculating circuit for calculating an in-region histogram average value, and a second value for controlling the value output to the DC level subtractor so that the output of the in-region histogram average value calculating circuit is always a prescribed value Infrared image pickup device, comprising: 5. An infrared optical system for condensing infrared rays emitted from an object, an infrared solid-state imaging device for detecting infrared rays and performing photoelectric conversion, and a DC output from the infrared solid-state imaging device.
A DC level subtractor for removing components, a first A / D converter for converting an analog signal output of the DC level subtractor into a digital signal, and an output of the A / D converter are corrected to obtain a digital video. A correction processing circuit for converting into a signal, a D / A converter for converting the digital video signal output of the correction processing circuit into an analog video signal, a control signal generating circuit for generating various control signals, and a display monitor for displaying an image. An amplifier for amplifying the output of the infrared solid-state imaging device, a second A / D converter for converting an analog signal output of the amplifier into a digital signal, and the second
The A / D converter output, a histogram calculation circuit that calculates a histogram for one frame, a black level correction table that suppresses the correction amount in the black level direction, the output of the histogram calculation circuit, and the black level A first histogram shape conversion circuit that receives the output of the correction table and performs a correction operation, a white level correction table that suppresses the correction amount in the direction of the white level, an output of the first histogram shape conversion circuit, and the white level. Receive the output of the correction table,
A second histogram shape conversion circuit for performing correction calculation;
A histogram average value calculation circuit for calculating an average value of the histogram with respect to the output of the second histogram shape conversion circuit; and an output of the histogram average value calculation circuit for determining a value to be set in the DC level subtractor. D of 3
An infrared imaging device comprising a C level control unit. 6. An infrared optical system for condensing infrared rays emitted from an object, an infrared solid-state image sensor for detecting infrared rays and performing photoelectric conversion, and a DC output from the infrared solid-state image sensor.
A DC level subtractor for removing components, a first A / D converter for converting an analog signal output of the DC level subtractor into a digital signal, and an output of the A / D converter are corrected to obtain a digital video. A correction processing circuit for converting into a signal, a D / A converter for converting the digital video signal output of the correction processing circuit into an analog video signal, a control signal generating circuit for generating various control signals, and a display monitor for displaying an image. An amplifier for amplifying the output of the infrared solid-state imaging device, a second A / D converter for converting an analog signal output of the amplifier into a digital signal, and the second
The A / D converter output, a histogram calculation circuit that calculates a histogram for one frame, a black level correction table that suppresses the correction amount in the black level direction, the output of the histogram calculation circuit, and the black level A first histogram shape conversion circuit that receives the output of the correction table and performs a correction operation, a white level correction table that suppresses the correction amount in the direction of the white level, an output of the first histogram shape conversion circuit, and the white level. Receive the output of the correction table,
A second histogram shape conversion circuit for performing correction calculation;
An area designation generation circuit that limits a processing area; an in-area histogram average value calculation circuit that receives an output of the second histogram shape conversion circuit and an output of the area designation generation circuit and calculates a histogram average value in the area; An infrared imaging device comprising: a third DC level control unit that receives an output of the in-region histogram average value calculation circuit and determines a value to be set in a DC level subtractor.