CN109671050B

CN109671050B - Method for detecting scintillation bad elements of linear detector

Info

Publication number: CN109671050B
Application number: CN201811331618.0A
Authority: CN
Inventors: 徐华楠; 王凯; 孙小亮; 李玉岩; 刘琼; 汪江华
Original assignee: Luoyang Institute of Electro Optical Equipment AVIC
Current assignee: Luoyang Institute of Electro Optical Equipment AVIC
Priority date: 2018-11-09
Filing date: 2018-11-09
Publication date: 2022-11-22
Anticipated expiration: 2038-11-09
Also published as: CN109671050A

Abstract

The invention relates to a method for detecting a scintillation bad element of a linear detector, which comprises the steps of performing improved median filtering on standard deviation of frame image data, calculating a difference value of median filtering results of a standard deviation array, marking an ith pixel as a scintillation bad element if the absolute value of ith data in the array is greater than a threshold Th, and otherwise, determining that the ith pixel is not the scintillation bad element. The invention combines the improved median filtering method and the self-adaptive threshold method to realize the scintillation bad element detection of the linear infrared detector. The method is simple in principle, can effectively detect the scintillation bad elements in the linear infrared detector, and reduces the false detection rate.

Description

Method for detecting scintillation bad elements of linear detector

Technical Field

The invention belongs to the technical field of image processing, and relates to a method for detecting a scintillation bad element of a linear detector.

Background

In an infrared imaging system, due to the problems of the device production process, blind pixels and flickering bad pixels often exist in a linear infrared detector, so that bright (dark) stripes (caused by the blind pixels) or alternately bright and dark stripes (caused by the flickering bad pixels) appear in an image along the scanning direction when the system is scanned and imaged, and the overall imaging effect and the subsequent small target detection effect are seriously influenced. Especially, the flicker bad element causes the generated light and dark alternate stripes, and the detection of the small target is greatly influenced. For the detection of bad elements of the linear detector, a time domain method and a window detection method are representative methods. The time domain method has higher detection precision, but cannot be realized in real time; the existing window method mainly detects blind pixels and cannot effectively detect flicker bad pixels. Therefore, a method for detecting a flash bad element is provided to improve the imaging quality of the line array detector.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides a method for detecting scintillation bad elements of a linear detector.

Technical scheme

A method for detecting scintillation bad elements of a linear detector is characterized by comprising the following steps:

step 1: after the system runs, acquiring a frame of image data and putting the frame of image data into a frame memory;

and 2, step: calculating the standard deviation of each line of image data in the frame image data and storing the standard deviation in an array R _ ST [ M ]; wherein M is the number of detector pixels;

and step 3: performing improved Median filtering on the standard deviation array R _ ST [ M ] in the sliding window by using the window with the size of W x 1, and storing a filtering result in the array R _ Median [ M ];

and 4, step 4: calculating the difference value between the standard difference array R _ ST [ M ] and the Median filtering result R _ media [ M ] and storing the difference value in the array ERR [ M ];

and 5: calculating the standard deviation sigma of the array ERR [ M ], multiplying the standard deviation sigma by a set weight value K to obtain a detection threshold Th of the flicker bad element:

sigma＝sqrt[∑(ERR(M)-avg)*(ERR(M)-avg)]

avg＝∑ERR(M)/M

Th＝K*sigma

wherein: avg is the average of the array ERR [ M ];

step 6: and judging the array ERR [ M ] by using a threshold Th, if the absolute value of the ith data in the array ERR [ M ] is greater than the threshold Th, marking the ith pixel as a flicker bad element, and if not, considering that the ith pixel is not the flicker bad element.

The weight K is 2.5-5.

The improved median filtering method: recording W standard difference values in the sliding window as an array ST _ WD [ W ]; removing the maximum value and the minimum value in the array ST _ WD [ W ], and recording the rest W-2 values as an array ST _ TEMP [ W-2]; sorting the values in the array ST _ TEMP [ W-2] and outputting the median value.

Advantageous effects

The invention provides a method for detecting a flicker bad element of a linear detector, which comprises the steps of performing improved median filtering on a standard deviation of frame image data, calculating a difference value of median filtering results of a standard deviation array, marking an ith pixel as the flicker bad element if an absolute value of ith data in the array is greater than a threshold Th, and otherwise, judging that the ith pixel is not the flicker bad element.

The invention combines the improved median filtering method and the self-adaptive threshold method to realize the scintillation bad element detection of the linear infrared detector. The method is simple in principle, can effectively detect the scintillation bad elements in the linear infrared detector, and reduces the false detection rate.

Drawings

FIG. 1 is a flowchart of the procedure of the present invention

Detailed Description

The invention will now be further described with reference to the following examples and drawings:

the specific implementation method comprises the following steps:

(1) After the system operates, acquiring a frame of image data and putting the frame of image data into a frame memory;

(2) The standard deviation of the image data for each line is calculated and stored in the array R _ ST [ M ]. Wherein M is the number of detector pixels;

(3) An improved median filtering is performed on the standard deviation array R _ ST [ M ]. Taking the window size as W x 1, carrying out improved Median filtering on a standard deviation array R _ ST [ M ] in the sliding window, and storing a filtering result in an array R _ Median [ M ];

(4) Calculating the difference value between the standard difference array R _ ST [ M ] and the Median filtering result R _ media [ M ] and storing the difference value in the array ERR [ M ];

(5) An adaptive threshold is calculated. Calculating the standard deviation sigma of the array ERR [ M ], and multiplying the standard deviation sigma by a set weight K to obtain a detection threshold Th of the flicker bad element;

sigma＝sqrt[∑(ERR(M)-avg)*(ERR(M)-avg)]

avg＝∑ERR(M)/M

Th＝K*sigma

(6) And judging the array ERR [ M ] by using a threshold Th, if the absolute value of the ith data in the array ERR [ M ] is greater than the threshold Th, marking the ith pixel as a flicker bad element, otherwise, considering that the ith pixel is not the flicker bad element.

Example (b):

for a 480-pixel line-array infrared imaging system, after the infrared system is powered on and operated, an infrared image with 480 × 640 pixels, that is, an infrared image with 480 rows and 640 columns, is obtained. The standard deviation for each row of data for this image is calculated and stored in the array R _ ST [480] (step 2). The array R _ ST [480] is subjected to improved Median filtering by the size of the window 9 × 1, resulting in the array R _ media [480] (step 3). The difference between the arrays R _ ST [480] and R _ Median [480] is calculated to obtain the difference array ERR [480] (step 4). The standard deviation sigma of the array ERR [480] is calculated and then the adaptive threshold is found: th = K sigma, where K =4.35 (step 5). And judging the array ERR [480] by using a threshold Th, if the absolute value of the ith data in the array ERR [480] is greater than the threshold Th, marking the ith pixel as a flicker bad element, otherwise, considering that the ith pixel is not the flicker bad element.

Claims

1. A method for detecting scintillation bad elements of a linear detector is characterized by comprising the following steps:

step 1: after the system operates, acquiring a frame of image data and putting the frame of image data into a frame memory;

and 5: calculating the standard deviation sigma of the array ERR [ M ], and multiplying the standard deviation sigma by a set weight K to obtain a detection threshold Th of the flicker bad element:

sigma＝sqrt[∑(ERR(M)-avg)*(ERR(M)-avg)]

avg＝∑ERR(M)/M

Th＝K*sigma

wherein: avg is the average of the array ERR [ M ];

2. The method for detecting the scintillation bad element of the line array detector as recited in claim 1, wherein: the weight K is 2.5-5.

3. The method for detecting the scintillation bad element of the line array detector as recited in claim 1, wherein: the improved median filtering method: recording W standard difference values in the sliding window as an array ST _ WD [ W ]; removing the maximum value and the minimum value in the array ST _ WD [ W ], and recording the rest W-2 values as an array ST _ TEMP [ W-2]; sorting the numerical values in the array ST _ TEMP [ W-2] and outputting the median value.