KR20200081191A - Apparatus for detecting soft defective pixels in infrared camera for detection of acquired bad pixels - Google Patents

Abstract

Disclosed is a soft defective pixel detecting device of a thermal camera comprising: a median value filter module for outputting a representative pixel by performing median value filtering on a pixel of a predetermined area of an image of a thermal camera; and a defective pixel detecting module for detecting a defective pixel of the image by using the representative pixel outputted from the median value filter module. According to the present invention, the contrast of a pixel is improved to a level of visual identification to calculate a median value with the median value filter module, and a defective pixel is detected by comparing pixels through a comparator module, thereby detecting an acquired defective pixel due to aging of the thermal camera, and corresponding even to a statistically determined error, wherein an original defective pixel is determined as a normal pixel. Also, a separate reference image is not required to be inputted for each thermal camera like an existing method but detects and compensates for a defective pixel by itself, thereby being convenient and greatly increasing the accuracy of detecting the defective pixel of the aged thermal camera compared to that of the conventional invention.

Description

A thermal imaging camera's soft defective pixel detection device for detection of acquired bad pixels {APPARATUS FOR DETECTING SOFT DEFECTIVE PIXELS IN INFRARED CAMERA FOR DETECTION OF ACQUIRED BAD PIXELS}

The present invention relates to a thermal imaging camera, specifically, to a soft defective pixel detection device of a thermal camera, and more specifically to a soft defective pixel detection and compensation device of a thermal imaging camera.

In the thermal imaging camera, each pixel basically has a characteristic difference during the factory shipment process.

Thermal imaging cameras contain defective pixels from the factory, and pixel defects are compensated through non-formality correction in the subsequent use process.

On the other hand, in a thermal camera, a normal pixel may be changed to a defective pixel by long-term use when shipped from the factory. The original defective pixel can be easily compensated and used in the conventional manner, but there is no proper means for error compensation for the acquired defective pixel caused by long-term use.

Also, when it is judged to be good or bad at the time of factory shipment, if it is judged to be more statistically normal, it is specified and shipped as a normal pixel. In this case, a statistical judgment error in which a bad pixel is determined to be a normal pixel may occur.

As such, there is a need for a method for detecting and compensating for a statistical error of the original bad pixel and an acquired bad pixel.

10-0415051 10-1656173

An object of the present invention is to provide an apparatus for detecting soft defective pixels of a thermal imaging camera.

An apparatus for detecting soft defective pixels of a thermal imaging camera according to the object of the present invention described above includes: a median filter module for outputting a representative pixel by performing median filtering on pixels in a predetermined area of an image of the thermal imaging camera; It may be configured to include a bad pixel detection module for detecting a bad pixel of the image by using a representative pixel output from the median filter module.

Here, it may be configured to further include a bad pixel interpolation module that performs interpolation on the bad pixels detected by the bad pixel detection module.

In addition, the median filter module may be configured to perform median filtering on pixels in a 3X3 region of the image.

An apparatus for detecting soft defective pixels of a thermal imaging camera according to the object of the present invention described above includes: a median filter module that sequentially outputs a representative pixel by sequentially performing median filtering on pixels in a 3X3 region of an image of the thermal imaging camera; It may be configured to include a bad pixel detection module for detecting a bad pixel of the image by using a representative pixel output from the median filter module.

Here, it may be configured to further include a bad pixel interpolation module that performs linear interpolation on the bad pixels detected by the bad pixel detection module.

In addition, the intermediate filter module may be configured as a low-pass filter.

The above-described apparatus for detecting a soft defective pixel of a thermal imaging camera according to the object of the present invention performs an intermediate value filtering on pixels of an nXn region sequentially on an image of the thermal imaging camera to output a representative pixel. ; A bad pixel detection module for detecting bad pixels of the image by using the representative pixels output from the median filter module; And a bad pixel interpolation module that performs linear interpolation on the bad pixels detected by the bad pixel detection module.

Here, the bad pixel interpolation module may be configured to perform bidirectional linear interpolation on the bad pixels detected by the bad pixel detection module.

In addition, the intermediate filter module may be configured as a low-pass filter.

The apparatus for detecting a soft defective pixel of a thermal imaging camera according to the object of the present invention described above outputs a representative pixel by performing an intermediate value filtering on 8 peripheral pixels excluding the central pixel of the 3X3 region on the image of the thermal imaging camera A median filter module; A defective pixel detection module that detects whether the central pixel is defective by using a representative pixel output from the median filter module; And configured to include a bad pixel interpolation module that bypasses the detected normal pixel when it is detected as the normal pixel in the bad pixel detection module and interpolates the detected bad pixel when it is detected as the bad pixel in the bad pixel detection module. Can be.

Here, the bad pixel detection module may be configured to perform bidirectional linear interpolation on the bad pixels detected by the bad pixel detection module.

In addition, the intermediate filter module may be configured to have robust characteristics against impulse noise as a low-pass filter.

The apparatus for detecting soft bad pixels of a thermal imaging camera according to the object of the present invention described above performs median filtering on eight peripheral pixels except for the center pixel of the nXn region for an image immediately after aging of the thermal imaging camera. An intermediate value filter module to perform and output a representative pixel; A defective pixel detection module that detects whether the central pixel is defective by using a representative pixel output from the median filter module; And a bad pixel interpolation module that linearly interpolates bad pixels detected by the bad pixel detection module.

Here, the bad pixel interpolation module bypasses the detected normal pixel when it is detected as the normal pixel in the bad pixel detection module and bidirectionally detects the detected bad pixel when it is detected as the bad pixel in the bad pixel detection module. It can be configured to perform linear interpolation.

And in the above nXn, n is odd.

According to the above-described apparatus for detecting a soft defective pixel of the thermal camera, the intermediate value of the intermediate filter module and surrounding pixels is calculated and configured to detect the defective pixel for each pixel through the comparator module, and thus acquired defects due to the aging of the thermal camera. There is an effect capable of detecting a pixel and responding to a statistical judgment error that determines the original bad pixel as a normal pixel. That is, there is an effect of finding a defective pixel that is not detected even after aging of the thermal imaging camera.

As in the conventional method, it is not necessary to input a separate reference image for each thermal camera, and it detects and compensates for defective pixels by itself, which is convenient and has an effect that the accuracy of detection of defective pixels of an aging thermal camera is very high compared to the previous one.

In addition, it is configured to detect defective pixels by improving the contrast of the pixels to the level of visual identification, and thus has an effect of easily distinguishing the contrast difference for each area, and has the effect of finding the defective pixels at the level of visual identification.

1 is a block diagram of a soft defective pixel detection device of a thermal imaging camera according to an embodiment of the present invention.
2 is a schematic diagram of a configuration of detecting a soft defective pixel of a thermal imaging camera according to an embodiment of the present invention.

The present invention can be applied to various changes and can have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in detail for carrying out the invention. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing each drawing, similar reference numerals are used for similar components.

Terms such as first, second, A, and B can be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from other components. For example, the first component may be referred to as a second component without departing from the scope of the present invention, and similarly, the second component may be referred to as a first component. The term and/or includes a combination of a plurality of related described items or any one of a plurality of related described items.

When an element is said to be "connected" or "connected" to another component, it is understood that other components may be directly connected to or connected to the other component, but there may be other components in between. It should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that no other component exists in the middle.

The terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as “include” or “have” are intended to indicate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, and that one or more other features are present. It should be understood that the existence or addition possibilities of fields or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. Terms, such as those defined in a commonly used dictionary, should be interpreted as having meanings consistent with meanings in the context of related technologies, and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. Does not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a soft defective pixel detection apparatus of a thermal imaging camera according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a soft defective pixel detection configuration of a thermal imaging camera according to an embodiment of the present invention.

Referring first to FIG. 1, the apparatus 100 for detecting soft defective pixels of a thermal imaging camera according to an embodiment of the present invention includes a contrast improvement module 110, a median filter module 120, a comparator module 130, and a bidirectional linear It may be configured to include an interpolation module 140.

In contrast to the detection and compensation of the existing original defective pixel in preparation for the reference image, the soft defective pixel detection apparatus 100 of the thermal imaging camera is configured to detect the defective pixel through its own median filtering and comparison between the center pixel and surrounding pixels. do.

The soft defective pixel detection apparatus 100 of the thermal imaging camera is capable of detecting acquired defective pixels according to the aging of the thermal imaging camera, and can also respond to statistical judgment errors that determine the original defective pixels as normal pixels during the factory shipment process. That is, it is possible to find defective pixels remaining after aging of the thermal imaging camera.

Since the reference image generated at the time of shipment from the factory is not used, the detection accuracy of the defective pixel of an aging thermal imaging camera is increased.

On the other hand, it is configured to detect a defective pixel by improving the contrast of the pixel to the level of visual identification, which has the advantage of finding a defective pixel at the level of visual identification.

Hereinafter, a detailed configuration will be described.

The contrast improvement module 110 may be configured to receive a pixel stream of a thermal imaging camera and improve contrast.

The contrast enhancement module 110 may be configured to move the pixel stream to a contrast of a band recognizable by the human eye to smooth it.

The contrast improvement module 110 has an advantage of easily distinguishing contrast differences for each region of the image.

The median filter module 120 may be configured to perform median filtering on neighboring pixels except for the center pixel of the nXn region for the image of the thermal imaging camera. The representative pixel value of the surrounding pixels can be found by median filtering.

Here, n is an odd number, and nXn may be 3X3, 5X5, 7X7, or the like.

The median filter module 120 is a low-pass filter, and may be configured to have robust characteristics against impulse noise.

In the example of FIG. 2, the center pixel has a value of 12, and the median value of eight peripheral pixels, that is, the representative pixel value is 11.

The median filter module 120 may sequentially perform median filtering using each pixel of the pixel stream as a center pixel.

The bad pixel detection module 130 may be configured to detect whether the center pixel is defective using a representative pixel output from the median filter module 120.

The bad pixel detection module 130 may be configured as a comparator module 130. The bad pixel detection module 130 may be input with a predetermined constant value added or subtracted as needed for a median value of median filtering performed by the median filter module 120, that is, a representative pixel of neighboring pixels.

Further, the value of the center pixel in which the contrast is improved may be input to the comparator module 130 by the contrast enhancement module 110.

Meanwhile, as shown in FIG. 2, the comparator module 130 may be configured to calculate a difference between a representative pixel and a central pixel, and compare the calculated difference with a predetermined threshold to determine size.

The comparator module 130 is configured to determine that the center pixel is a normal pixel when the difference between the representative pixel and the center pixel is less than the threshold, and determine that the center pixel is a bad pixel when the difference between the representative pixel and the center pixel is greater than the threshold. Can be. If the center pixel has a level difference greater than or equal to a predetermined threshold value compared to a representative value of surrounding pixels, it is determined as a bad pixel.

The comparator module 130 may be configured to sequentially determine whether a pixel is good or bad for each pixel in the pixel stream.

Here, the threshold may be variably set.

The threshold may be set as in Equations 1, 2, and 3 below.

가 산정되기 위한 시간은 열상 카메라 운용 초기화 이후 1분 이상 이어야 한다. 여기서,

는 충분히 작은 값을 취하기 위한 조건으로서, 최대 픽셀값의 10 %로 설정될 수 있다.Threshold

The time to be calculated should be at least 1 minute after initializing the operation of the thermal imaging camera. here,

Is a condition for taking a sufficiently small value, and can be set to 10% of the maximum pixel value.

의 최소값 및 최대값 제한을 걸어줄 수 있다.And as in Equation 2, the threshold value is used to prevent miscalculation.

You can limit the minimum and maximum values of.

The bad pixel interpolation module 140 bypasses the detected normal pixel when the bad pixel detection module 130 detects it as a normal pixel, and detects the bad pixel interpolation module 130 when it detects as a bad pixel. It can be configured to interpolate bad pixels.

The bad pixel interpolation module 140 may be a bidirectional linear interpolation module 140.

The bidirectional linear interpolation module 140 may change a defective pixel into a normal pixel through bidirectional linear interpolation.

Although it has been described with reference to the above embodiment, those skilled in the art can understand that the present invention can be variously modified and changed within the scope not departing from the spirit and scope of the present invention described in the following claims. There will be.

110: contrast enhancement module
120: median filter module
130: bad pixel detection module (comparator module)
140: bad pixel interpolation module (bidirectional linear interpolation module)

Claims (1)

A contrast improvement module that receives a pixel stream of a thermal imaging camera and improves contrast;
A median filter module that outputs a representative pixel by performing median filtering on pixels in a predetermined area of the image of the thermal imaging camera;
A bad pixel detection module for detecting bad pixels of the image by using a representative pixel output from the median filter module;
And a bad pixel interpolation module that performs linear interpolation on the bad pixels detected by the bad pixel detection module.
The median filter module,
Configured to perform median filtering on pixels in the 3X3 region of the image,
The contrast improvement module,
It is configured to move the pixel stream to the contrast of the band that can be visually identified, and to smooth it.
The bad pixel detection module,
It is configured to include a comparator, and a predetermined constant value is added to or subtracted from a representative pixel that is an intermediate value that has been subjected to median filtering in the median filter module.
The bad pixel detection module,
The difference between the representative pixel and the center pixel is calculated using the comparator, and the difference between the representative pixel and the center pixel is smaller than the threshold value by comparing the calculated difference with a predetermined threshold value. Is determined as a normal pixel, and if the difference between the representative pixel and the central pixel is greater than a threshold value, the corresponding central pixel is determined as a bad pixel.
The bad pixel interpolation module,
When the bad pixel detection module is detected as a normal pixel, the detected normal pixel is bypassed, and when the bad pixel detection module is detected as a bad pixel, the bad pixel is configured to perform bidirectional linear interpolation. A device for detecting soft defective pixels in a thermal imaging camera for detecting defective pixels.

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