JPH0614268A - Infrared ray image pickup device - Google Patents

Abstract

PURPOSE:To solve the difficulty of the combination of two means (picture correction and interpolation) which remove the nonuniformity of the sensitivity at every pixel of an infrared ray image pickup element. CONSTITUTION:The output of a solid image pickup element 1 which converts an infrared ray to a two dimensional image pickup signal is inputted to a gain adjusting circuit 3, and one from among the plural gains beforehand set is selected by the gain adjusting circuit 3, so that a picture correction can be attained. And concerning to a pixel which is beyond the conversion enabling range (maximum input range) of an A/D converter 4, by the selection of the gain by the gain adjusting circuit 3, picture-interpolation is performed by preparing memories 10a and 10b which beforehand store the position corresponding to the gain of the gain adjusting circuit 3, and by reading the content of the memory corresponding to the selected gain.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared image pickup device having a sensitivity unevenness correction circuit for correcting a sensitivity difference between pixels of an infrared solid-state image pickup device.

[0002]

2. Description of the Related Art A solid-state image pickup device provided in an infrared image pickup device causes non-uniformity in sensitivity for each pixel constituting the device due to process problems, and when the same temperature source is observed,
The pixel outputs do not have the same value. The following is a general means for removing the sensitivity nonuniformity. That is,
In advance, a correction coefficient is calculated from the output levels of all pixels for two temperatures and stored, and the stored data is used to perform so-called image correction for reducing sensitivity nonuniformity for each pixel (for example, Japanese Patent Laid-Open No. H11-242242). 3-204285). Also, for pixels with significant non-uniformity, the pixel position is identified as a defective pixel in advance and stored, and when that pixel is output,
So-called image interpolation is performed, in which the values of adjacent pixels are replaced (see, for example, JP-A-56-64570).

[0003]

However, the actual sensitivity non-uniformity varies depending on the nature of the solid-state image sensor,
In the case of an element having a wide sensitivity distribution, the image quality is remarkably different depending on the selection of the pixels corresponding to the image interpolation. That is, as the image correction is performed up to the pixel of the sensitivity that is farther from the sensitivity center (for example, the sensitivity center is set to the median value of all pixels), the resolution of the arithmetic processing system is constant and the S / N of the image decreases. To do. If the image correction is performed only on the pixels having the sensitivity close to the sensitivity center, the S / N of the image is improved, but many pixels are used for the image interpolation, the substantial spatial resolution is lowered, and the detection of the object The recognition probability decreases.

The present invention eliminates the difficulty of the combination of the two means (image correction and image interpolation) for removing the sensitivity nonuniformity for each pixel, and makes it possible to use the infrared image pickup according to the purpose of the user. The purpose is to obtain a device.

[0005]

In order to solve the above-mentioned problems, an infrared imaging device according to the present invention (1) receives an infrared image formed by an infrared optical system and converts the received infrared image into the received infrared image. The image pickup means for outputting a corresponding video signal, the A / D conversion means for converting the video signal output by the image pickup means into a digital image signal, and the digital image signal output by the A / D conversion means are input, In a infrared image pickup device having a predetermined pixel of the image pickup means as a pixel to be interpolated and a signal processing means for interpolating the output with the output of an adjacent pixel to create an infrared image signal, a maximum output fluctuation range of a desired pixel is set. Gain adjusting means for adjusting the maximum input range of the A / D converting means is provided between the image pickup means and the A / D converting means, and the maximum output is obtained as a result of the adjustment by the gain adjusting means. An infrared imaging device characterized in that the signal processing means is provided with a switching means for setting a pixel whose moving range exceeds the maximum input range of the A / D conversion means as an interpolation target pixel. (2) Imaging means for receiving an infrared image formed by the infrared optical system and outputting a video signal corresponding to the received infrared image, and a video signal output by the imaging means to a digital image signal An A / D conversion unit and a digital image signal output from the A / D conversion unit are input, and a predetermined pixel of the image pickup unit is set as an interpolation target pixel, and the output is interpolated by an output of an adjacent pixel to form an infrared image signal And a signal processing means for generating the
Corresponding to the gain selection means provided between the conversion means and capable of selecting a plurality of predetermined gains, and the gain selected by the gain selection means, the maximum output fluctuation range of the A / D conversion means. Memory means for pre-storing the position of a pixel that has exceeded the maximum input range as an interpolation target pixel, and the signal processing means responds from the memory means according to the gain selection by the gain selection means. The infrared imaging device is characterized in that the position of the pixel is read out and interpolation is performed.

[0006]

According to the present invention, the gain adjusting means allows S
Since it is possible to select the gain by emphasizing either / N or spatial resolution, the observer can obtain the image of the optimum image quality depending on the usage situation.

[0007]

FIG. 1 is a block diagram of an embodiment of the present invention. Solid-state image sensor 1 through an infrared imaging optical system (not shown)
The infrared rays incident on are photoelectrically converted by photoelectric conversion units (pixels) arranged corresponding to the two-dimensional coordinate positions of the solid-state image sensor 1, and sequentially output as a video signal. This output is
After the offset is adjusted by the offset adjusting circuit 2, the gain is adjusted by the gain adjusting circuit 3 and input to the A / D converter 4. The offset adjustment circuit 2 is configured so that the observer can freely set the offset by operating a dial or the like, and the gain adjustment circuit 3 allows the observer to arbitrarily select a plurality of gains prepared in advance. .

The image signal converted into a digital signal by the A / D converter 4 is digitally subjected to a gain adjustment (switching) reverse to the gain adjustment (switching) performed by the gain adjusting circuit 3 by the gain adjusting circuit 5. Then, the offset adjustment circuit 6 digitally performs the opposite adjustment to the offset adjustment performed by the offset adjustment circuit 2, and inputs the result to the image correction circuit 7.

The image correction circuit 7 digitally performs image correction of an image signal (video signal output from the solid-state image pickup device 1) by using an image correction coefficient memory 8 in which correction coefficients are stored in advance. That is, the image correction coefficient memory 8 stores the correction coefficient in advance in association with the two-dimensional coordinate position of each photoelectric conversion unit of the solid-state image sensor 1. Then, the image correction circuit 7 reads the correction coefficient corresponding to the image signal input from the offset adjustment circuit 6 from the image correction circuit 7 at the timing adjusted by the control signal from the control circuit 20.

The image correction circuit 7 performs image correction from the signal input from the offset adjustment circuit 6 and the correction coefficient from the image correction coefficient memory 8 to eliminate sensitivity nonuniformity of each photoelectric conversion unit of the solid-state image pickup device 1. Reduce. The output of the image correction circuit 7 is input to the image interpolation circuit 9. The image interpolation circuit 9
The gain adjustment circuit 3 is provided with a number of image interpolation position memories 10a, 10b, etc. equal to the number of gains prepared in advance, and the contents of the memory corresponding to the gain selected by the gain adjustment circuit 3 are controlled as described below. It is configured to read by a signal from the circuit 20. In this gain adjustment, the gain selection switches of the gain adjustment circuits 3 and 5 and the selection switches of the image interpolation position memories 10a and 10b may be configured as interlocking switches.

The image interpolating circuit 9 is timed by the control signal from the control circuit 20, and when it is necessary to interpolate the value of the image signal corresponding to the output of the image correcting circuit 7, the selected memory is selected. Image interpolation is performed based on the contents of. In this way, the signal whose image quality has been improved by performing the image correction and the image interpolation is the D / A converter 11
After being converted into an analog signal by, the synchronizing signal is added by the synchronizing signal adding circuit 12 to the TV signal format and output, and displayed on the display 13 such as a CRT.

Here, the control circuit 20 will be described. The control circuit 20 is a circuit for adjusting the timing of each circuit and for adjusting the circuit related to gain adjustment, and is a pulse generator for generating a pulse of a reference frequency. Including,
Depending on the function of softly dividing the pulse of the reference frequency and the command from the input device 21, the gain adjusting circuits 3 and 5 are provided.
Of the image interpolation circuit 9 so that the memories 10a, 10b, etc. corresponding to the gain adjustment are selected.
It mainly has a function of issuing a selection command to. That is, the control circuit 20 creates a video signal by sequentially outputting signals photoelectrically converted by each photoelectric conversion unit by sequentially scanning each photoelectric conversion unit of the solid-state imaging device 1 in synchronization with a pulse. In order to convert the video signal into an A / D converter 3 for converting the video signal into a digital signal (image signal) corresponding to the output of each photoelectric conversion unit and a D / A converter 12 for performing the reverse operation at a timing. Of the image signal input to the image correction circuit 7 and the image signal input to the image correction circuit 7 is subjected to appropriate image correction, and a predetermined pulse of the image signal input to the image interpolation circuit 9 is interpolated. It is supplied to the correction circuit 7 and the image interpolation circuit 9, respectively. Further, when the observer specifies the gain on the input device 21, the specified gain is set in the gain adjusting circuits 3 and 5, and the memories 10 a and 1 selected by the image interpolation circuit 9 are set.
A selection command designating 0b or the like is input to the image interpolation circuit 9.

Next, the operation of the apparatus described above will be described below. First, the sensitivity of the photoelectric conversion portion of the solid-state imaging device 1 is either A ₄ is assumed from the A _0, is substantially equal number of elements of sensitivity A ₄ from the sensitivity A _0, sensitivity A ₄ from the sensitivity A ₀
In between, A ₁ = 1/50 · A ₀ , A ₂ = 1/10 · A
_{It is} assumed that there is a relationship of ₀ , A ₃ = 10 · A ₀ , and A ₄ = 50 · A ₀ .

FIG. 2 shows these relationships, in which the horizontal axis represents temperature and the vertical axis represents the output of the photoelectric conversion unit. Temperature T
₀ is the lowest measurable temperature at which the output of each photoelectric conversion unit matches Q ₀ , and temperature T ₁ is the highest measurable temperature,
The output of the photoelectric conversion unit with sensitivity A ₀ at temperature T ₁ is Q ₂ ,
The output of the photoelectric conversion unit having sensitivity A ₄ at temperature T ₁ is shown by Q ₁ .

Here, as an example, consider a case where each photoelectric conversion unit with sensitivity A ₄ is used as a defective pixel and its two-dimensional coordinate value is stored in the image interpolation position memory 10. In this case, 20% of the total photoelectric conversion portion of the solid-state image sensor 1 (sensitivity A ₄
Each photoelectric conversion unit) is subjected to image interpolation, and the remaining 80% (sensitivity A ₀ , A ₁ , A ₂ , A ₃ ) image signal is output.

Then, the gain adjusting circuit 3 adjusts the output X ₃ of the photoelectric conversion unit having the sensitivity A ₃ at the maximum observation temperature T ₁ (shown in FIG. 2) to the maximum input level of the A / D converter 4. The sensitivity is selectable. In other words, the gain is adjusted so that the range H of FIG. 2 falls within the dynamic range of the A / D converter 4. Therefore, the sensitivity A
Outputs from the photoelectric conversion units having sensitivities A ₀ , A ₁ , and A ₂ lower than ₃ are used as image signals.

Now, the resolution of the A / D converter 4 is 1
If it is 0 bit, the image signal of sensitivity A ₃ is 102
An image signal having a gradation of 4 (2 ¹⁰ ) and a sensitivity of A ₂ is 102
An image signal having a gradation of 4/100 and sensitivity A ₁ is 102
An image signal having a gradation of 4/500 and sensitivity A ₀ is 102
It will have a gradation of 4/10. In such a case, the image signal of sensitivity A ₁ is only gradations of 1024/500, also, since the image signal sensitivity A ₂ has only gradations of 1024/100, in particular image signal sensitivity A ₁ Although it exists as a signal, if the S / N is poor and the image signal of sensitivity A ₁ greatly contributes to the image quality, the overall image quality is significantly deteriorated.

[0018] Accordingly, provided with a photoelectric conversion unit of sensitivity A ₁ when it is desired to contribute significantly to the image quality, the output of the photoelectric conversion portion having a sensitivity A ₂ at the maximum observed temperature T ₁ is the maximum A / D converter 4 The gain adjusting circuit 3 is configured to select a gain such that the input level is reached. By doing so, this time, the image signal with sensitivity A ₂ has a gradation of 1024/10, the image signal with sensitivity A ₁ has a gradation of 1024/50, and the image signal with sensitivity A ₀ has a gradation of 1024. You will have a key.

In this case, in addition to the photoelectric conversion unit with sensitivity A ₄ , the photoelectric conversion unit with sensitivity A ₃ is also a target of image interpolation as a defective pixel, so that only 60% of pixel image output can be obtained. Therefore, although the resolution of the entire screen decreases, S
/ N becomes good. Based on such a principle, the gain adjusting circuit 3 is preset with a plurality of gains according to the sensitivity of the photoelectric conversion unit.

Therefore, the observer turns the dial of the offset adjusting circuit 2 to change the offset amount while looking at the image on the display 13 to bring the image into the most visible state, and then the input device 21 is used to adjust the gain adjusting circuit 3. The gain can be changed to select a more visible state. At this time, the control circuit 20 causes the gain of the gain adjusting circuit 5 and the image interpolation position memories 10a and 10b read by the image interpolating circuit 9 to interlock in accordance with the signal corresponding to the gain selected by the gain adjusting circuit 3. The selection is as described above.

The signal output from the gain adjusting circuit 3 is A
The signal is converted into a digital signal by the / D converter 4. In this conversion, the control device 20 sequentially outputs the output of the gain control adjustment circuit 3 to A / S in synchronization with the driving of each photoelectric conversion unit of the solid-state imaging device 1.
The converted signal is output to the A / D converter 4 so as to be D-converted. The image signal converted into a digital signal by the A / D converter 4 is digitally adjusted by the gain adjustment circuit 5 in the opposite manner to that performed by the gain adjustment circuit 3, and is offset by the offset adjustment circuit 6. The offset adjustment, which is the reverse of that performed by the adjustment circuit 2, is digitally performed. afterwards,
The image correction circuit 7 and the image interpolation circuit 9 perform correction based on the above-described principle. The image signal corrected in this way is converted into a video signal which is an analog signal by the D / A converter 11, and then the synchronizing signal is added by the synchronizing signal adding circuit 12.

As a result, an infrared image is displayed on the display 13. As described above, when an observer aims to find a subject with a narrow brightness distribution, he / she selects a gain that does not perform image interpolation as much as possible and aims to find a subject with a wide brightness distribution. In such a case, the gain is selected so as to increase the amount of image interpolation, and the image with an improved S / N is selected (actually, without being aware of such a thing, While watching the display 13, the gain is switched so that an image suitable for one's purpose can be obtained.
Pixels that perform image interpolation are linked to gain adjustment).

In the above description, the sensitivity of the photoelectric conversion unit of the solid-state image pickup device 1 exists in five stages and with the same probability, so it is assumed that there is 20% of each sensitivity. However, in reality, the variation in sensitivity is not so large, and the ratio of the photoelectric conversion unit requiring image interpolation to the front photoelectric conversion unit is not so large. Therefore, in reality, the gain adjustment circuit 3
It suffices that the gain can be adjusted in 2 to 5 steps.

[0024]

As described above, according to the present invention, the position of the photoelectric conversion unit that executes image interpolation is changed in association with the adjustment of the gain depending on the state of the object, so that the S / N and the spatial resolution are reduced. It is possible to obtain an infrared imaging device capable of selecting an image that emphasizes any of the above.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a graph for explaining a sensitivity distribution of a photoelectric conversion unit.

[Explanation of symbols]

 1 Solid-state image sensor 2 Offset adjustment circuit 3 Gain adjustment circuit 4 A / D converter 5 Gain adjustment circuit 6 Offset adjustment circuit 7 Image correction circuit 8 Image correction coefficient memory 9 Image interpolation circuit 10a Image interpolation position memory 10b Image interpolation position memory 11 D / A converter 12 Sync signal addition circuit 13 Display device 20 Control circuit

Claims (2)

[Claims] 1. An image pickup means for receiving an infrared image formed by an infrared optical system and outputting a video signal corresponding to the received infrared image, and a video signal output by the image pickup means as a digital image signal. A / D conversion means for conversion and a digital image signal output from the A / D conversion means are input,
An infrared image pickup device comprising: a predetermined pixel of the image pickup unit as an interpolation target pixel; and a signal processing unit for interpolating an output of the pixel with an output of an adjacent pixel to create an infrared image signal. Is provided between the image pickup means and the A / D conversion means, and the maximum output fluctuation range is as a result of the adjustment by the gain adjustment means. An infrared image pickup device, wherein the signal processing means is provided with a switching means for setting a pixel that has exceeded a maximum input range of the A / D conversion means as an interpolation target pixel. 2. An image pickup means for receiving an infrared image formed by an infrared optical system and outputting a video signal corresponding to the received infrared image, and a video signal output by the image pickup means as a digital image signal. A / D conversion means for conversion and a digital image signal output from the A / D conversion means are input,
An infrared image pickup device comprising: a predetermined pixel of the image pickup means as an interpolation target pixel; and an output of the adjacent pixel to interpolate an output of the pixel processing means to generate an infrared image signal. Provided between the conversion means,
The maximum output fluctuation range exceeds the maximum input range of the A / D conversion means, corresponding to the gain selection means capable of selecting a plurality of predetermined gains and the gain selected by the gain selection means. Memory means for pre-storing the position of the pixel as an interpolation target pixel is provided, and the signal processing means reads out the position of the corresponding pixel from the memory means according to the gain selection by the gain selecting means and performs interpolation. An infrared imaging device characterized by performing.