JP2551366B2 - Image drift control circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image drift control circuit. In particular, the present invention relates to an image drift control circuit that is applied to an infrared imaging device that captures infrared rays emitted from the surface of an object to obtain a two-dimensional thermal image, and that compensates for characteristic fluctuations due to temperature and the like.

[0002]

2. Description of the Related Art Conventionally, in an infrared image pickup device, in general, a drift of characteristics may occur in an infrared detector and an electronic circuit inside the image pickup device, especially due to a change in self-heating temperature / environmental temperature. This change in characteristics causes distortion in the fixed pattern of the infrared image pickup device output. Therefore, in order to improve the accuracy of the image obtained by the infrared imaging device, a uniform temperature pattern is imaged, a distortion component is extracted, and the imaged image data is corrected. In order to cope with changes in characteristics over time, a fixed pattern used to correct acquired imaged data is updated by re-imaging a flat reference image.

[0003]

However, in the conventional infrared imaging device, when the fixed pattern is deviated due to the drift of the infrared imaging device output or the drift of the electronic circuit in the imaging device, a uniform temperature pattern is imaged each time. The fixed pattern must be redone by doing. According to this procedure, it takes a lot of time to retake the fixed pattern, and the acquisition of the thermal image is interrupted each time the fixed pattern is retaken, which causes a problem that the continuity of the thermal image is lost.

It is an object of the present invention to provide an image drift control circuit capable of successively and automatically correcting the drift of a fixed pattern for obtaining a thermal image from an infrared imaging device.

[0005]

In order to achieve the above object, the image drift control circuit of the present invention subtracts a fixed pattern image data stored in advance from the image data acquired by a two-dimensional infrared image pickup device. An image drift control circuit which is applied to an infrared image pickup device for removing and obtains a thermal image and corrects an image drift of the infrared image pickup device, and a first storage means for storing image data of a fixed pattern,
Second storage means for storing the image data of the object to be measured, and Fourier transform means connected to the first and second storage means for Fourier transforming the image data stored in the respective storage means, and A second storage unit for inputting the respective frequency decomposition components of the image data converted by the Fourier transforming unit, comparing the respective input frequency components, and extracting and outputting the frequency components of the mutual difference; The image data of the object to be measured is stored in the means at a predetermined time interval, and the image data of the fixed pattern stored in the first storage means is updated based on the frequency component extracted by the comparison means. It is characterized by correcting image drift.

[0006]

According to the image drift control circuit of the present invention, the fixed pattern image data and the image data of the object to be measured are respectively stored, each stored image data is Fourier-transformed, and each frequency of the Fourier-transformed image data is stored. By comparing the components, extracting the frequency component of the mutual difference, and updating the stored image data of the fixed pattern on the basis of the extracted frequency component, the temporal change of the image drift component of the infrared imaging device is sequentially corrected. It becomes possible.

[0007]

Embodiments of the image drift control circuit according to the present invention will now be described in detail with reference to the accompanying drawings. Referring to FIG. 1, there is shown a partial configuration block diagram of an embodiment of an infrared imaging device to which an image drift control circuit of the present invention is applied. Hereinafter, the configuration of the present invention will be described in detail based on an embodiment shown in the drawings.

FIG. 1 is a partial block diagram of the infrared image pickup device as described above.
It is composed of a D converter 2, a subtractor 5, an image processing unit 6 and an image drift control circuit 10.

The two-dimensional infrared image pickup device 1 is an image pickup device which detects infrared rays, and the A / D converter 2 is a circuit which converts an analog signal output from the image pickup device 1 into a digital signal. The subtractor 5 is a circuit that calculates and outputs a difference between two digital input signals. The image processing unit 6 is a circuit unit that processes the digital original image signal such as D / A conversion to obtain a video signal.

The image drift control circuit 10 comprises a fixed pattern memory 3, an image memory 4, two Fourier transformers 7 and 7, and a comparator 8.

The fixed pattern memory 3 is a storage circuit for temporarily storing pixel data. This memory 3
Corrected image data for correcting the drift characteristic of the infrared imaging device is stored. The fixed pattern of the original image data is removed by subtracting the stored corrected image data from the original image data by the subtracter 5, and a thermal image is obtained. The image data of the fixed pattern corresponds to the temperature drift of the image pickup circuit and the amplifier circuit, and needs to be updated at predetermined time intervals. The stored image is updated by the memory content rewriting signal output from the comparator 8.

The image memory 4 is a storage circuit for temporarily storing pixel data, and may have substantially the same circuit configuration as the fixed pattern memory except that the object to be stored is different. The image data is captured in the image memory 4 at predetermined time intervals, and the captured image data has a change component for correcting a change with time of the fixed pattern image data stored in the fixed pattern memory 3. Used to extract.

The two Fourier transformers 7, 7 are two-dimensional Fourier transformers, and are circuit portions for frequency-decomposing image data of m × n pixels (m and n are positive integers). The two Fourier transformers 7, 7 are circuit units for performing Fourier transform on image data in the same two-dimensional image area of the fixed pattern memory 3 and the image memory 4. The respective image data stored in the two memories 3 and 4 are subjected to Fourier transform, and the contents of the fixed pattern memory 3 are rewritten so that the respective converted frequency components match. This is performed over the entire pixels of the two-dimensional infrared imaging device 1.

The comparator 8 is a circuit section for comparing the two-dimensional Fourier-transformed frequency components of the pixels based on the image data stored in the fixed pattern memory 3 and the image memory 4. The comparison result is output as a memory rewriting signal and written in the fixed pattern memory 3.

The image drift control circuit 10 composed of the above-mentioned respective circuit sections can obtain a highly accurate thermal image of a subject with the drift characteristic corrected by the following procedure shown in FIG. .

In step S12, a uniform temperature pattern is first imaged, and the reference image data G is written in the fixed pattern memory 3 and the image memory 4. Next, a uniform temperature pattern is removed from the imaging target. Step S14
Then, the image data g of the object to be measured is acquired, and step S1
The reference image data G written in 6 is subtracted (g−G) from the original image data g by the subtractor 5. The image processing unit 6 performs predetermined image processing on the subtracted image data to obtain a thermal image from the original image.

In step S18, it is checked whether or not a predetermined time T has elapsed, and the stored image data gm in the image memory 4 is updated every time the predetermined time has elapsed (step S).
20). In step S22, arbitrary m × n pixels of the data in the fixed pattern memory 3 and the image data in the image memory 4 in the same image area are frequency-decomposed by the Fourier transformers 7 and 7, respectively, and in step S24, respectively. The frequency components of are compared by the comparator 8.

The mutually different frequency components of the comparison result are extracted, and the extracted image data is output as a memory rewriting signal. The output data is fixed pattern memory 3 in step S26 so that the frequency components of arbitrary m × n pixels of the data of fixed pattern memory 3 match.
Is written to. This is performed over the entire pixels of the two-dimensional infrared imaging device 1 (step S28).

Steps S14 to S28 described above
Is repeatedly executed until the measurement of the thermal image of the measured object is completed (step S30). By repeating this series of operations, the fixed pattern data can follow the drift.

As described above, the present invention can reduce the deviation of the fixed pattern of the two-dimensional infrared image pickup device due to the drift of the two-dimensional infrared image pickup device or the drift of the circuit of the image pickup apparatus. Further, since a uniform temperature pattern can be captured only when the infrared imaging device is started up, it is possible to eliminate a temporary interruption of the thermal image due to the fixed pattern acquisition.

Although the above-described embodiment is a preferred example of the present invention, the present invention is not limited to this and various modifications can be made without departing from the gist of the present invention.

[0022]

According to the image drift circuit of the present invention, the image data of the fixed pattern and the image data of the object to be measured are respectively stored, and each stored image data is Fourier-transformed,
The frequency decomposition components of the two Fourier-transformed image data are compared, the frequency components of the mutual difference are extracted, and the stored image data of the fixed pattern is tracked and updated based on the extracted frequency components, and the image drift of the infrared imaging device is detected. It is possible to sequentially correct the amount of change over time. Therefore, the work of updating the image data of the fixed pattern is unnecessary, and the number of steps can be reduced and the acquired images can be made continuous.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment in which an image drift control circuit of the present invention is applied to an infrared imaging device.

FIG. 2 is a flow chart showing an example of an image drift correction procedure of the apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Two-dimensional infrared imaging device 2 A / D converter 3 Fixed pattern memory 4 Image memory 5 Subtractor 6 Image processing unit 7 Fourier transformer 8 Comparator 10 Image drift control circuit

Claims (3)

(57) [Claims] 1. An image of an infrared imaging device, which is applied to an infrared imaging device for obtaining a thermal image by subtracting and removing image data of a fixed pattern stored in advance from image data acquired by a two-dimensional infrared imaging device. In an image drift control circuit that corrects drift, the control circuit includes a first storage unit that stores the image data of the fixed pattern, a second storage unit that stores the image data of the measured object, and the first storage unit. And Fourier transform means for performing Fourier transform on the image data stored in each storage means, respectively connected to the second storage means, and inputting respective frequency components of the image data transformed by the Fourier transform means, And comparing means for comparing the respective input frequency components and extracting and outputting the frequency components of the mutual difference. The infrared imaging is performed by storing image data of the measurement object at predetermined time intervals and updating the fixed pattern image data stored in the first storage means based on the frequency component extracted by the comparison means. An image drift control circuit for correcting image drift of a device. 2. The image drift control circuit according to claim 1, wherein the image data of the fixed pattern stored in the first storage means is updated by the image data stored in the second storage means. An image drift control circuit, characterized in that the stored contents are rewritten so as to match the frequency components converted by the Fourier transform means. 3. The image drift control circuit according to claim 2, wherein the stored contents are rewritten for each predetermined pixel region.