KR101656173B1 - Method and apparatus for detecting faulty pixel in thermal camera - Google Patents

Abstract

According to an embodiment of the present invention, there is provided a method for detecting defective pixels in a thermal camera, comprising: closing and photographing a shutter of a thermal camera in accordance with an ambient temperature and a predetermined time period to generate a first frame of a thermal image; Closing and photographing the shutter of the thermal camera in accordance with the ambient temperature and a predetermined time period to generate a second frame of the thermal image; Calculating a first temperature of the shutter at the time of generating the first frame and a second temperature of the shutter at the time of generating the second frame from the respective data of the first and second frames, respectively; Calculating a slope of each pixel using the first and second frames; And comparing the average slope of the pixels between the first frame and the second frame with the slope of the pixels to determine a defective pixel first.

Description

[0001] The present invention relates to a method and an apparatus for detecting defective pixels in a thermal camera,

The present invention relates to a thermal imaging camera, and more particularly, to a defective pixel detection method and apparatus of a thermal imaging camera.

A thermal imaging camera, also called an infrared camera, is configured to output an image formed by sensing infrared rays. It is very useful for detecting a specific temperature in a dark environment, a fogged place, or the like, since an image is generated by sensing infrared rays emitted by an object, which is not visible light, even in the absence of light.

The thermal camera has an infrared sensor or an infrared sensor array arranged in the form of an infrared sensor array, and the thermal camera generates an image based on the temperature of the object obtained through the respective infrared detectors.

The infrared rays incident through the optical lens of the thermal camera are directly incident on the infrared ray detector assigned to each pixel, and each infrared ray detector measures the changing resistance value in response to the incident infrared ray energy, Conversion. At this time, each pixel of the infrared detector should output the same electrical signal for the same infrared energy, but all pixels exhibit different characteristics.

Non-uniformity correction is a method of adjusting the gain and offset for each pixel so that all the pixels of the infrared detector exhibit the same characteristics.

However, even though the non-uniform compensation is applied, there are pixels which show the same characteristics of the electric signal output and the response is high or low. These pixels are fixed defect pixels existing in the infrared detector from the beginning.

And, as the infrared detector changes over time, the electrical characteristics of the pixels are changed so that the defective pixels are progressive defective pixels. If a progressive bad pixel occurs, the quality of the image may deteriorate, and the bad pixel may be erroneously judged as another object.

In the past, when a progressive failure pixel occurred, the camera was sent to the thermal camera correction center, and the defective pixel correction operation was performed there, so time and manpower for correction were consumed. For example, Korean Unexamined Patent Application Publication No. 2003-0065141 discloses a method of detecting and correcting a progressive defect pixel. In this method, a gain (gain) and a deviation Offset), and detects progressive failure pixels therefrom. However, in this conventional technique, since the temperature of the object must be known in advance, such a work can be performed only at a correction center having a black body that can be controlled at an accurate temperature.

Korean Patent Publication No. 2003-0065141 (published on August 6, 2003)

It is an object of the present invention to provide an apparatus and method for automatically correcting defective pixels in a thermal camera capable of automatically detecting and correcting progressive defective pixels while a user uses a thermal camera.

According to an embodiment of the present invention, there is provided a method for detecting defective pixels in a thermal camera, comprising: closing and photographing a shutter of a thermal camera in accordance with an ambient temperature and a predetermined time period to generate a first frame of a thermal image; Closing and photographing the shutter of the thermal camera in accordance with the ambient temperature and a predetermined time period to generate a second frame of the thermal image; Calculating a first temperature of the shutter at the time of generating the first frame and a second temperature of the shutter at the time of generating the second frame from the respective data of the first and second frames, respectively; Calculating a slope of each pixel using the first and second frames; And comparing the average slope of the pixel between the first frame and the second frame with the slope of each pixel to determine a defective pixel first, do.

According to an embodiment of the present invention, there is provided a method for detecting defective pixels in a thermal camera, comprising: closing and photographing a shutter of a thermal camera in accordance with an ambient temperature and a predetermined time period to generate a first frame of a thermal image; Closing and photographing the shutter of the thermal camera in accordance with the ambient temperature and a predetermined time period to generate a second frame of the thermal image; Calculating a first temperature of the shutter at the time of generating the first frame and a second temperature of the shutter at the time of generating the second frame from the respective data of the first and second frames, respectively; Calculating a slope of each pixel using the first and second frames; And comparing the calculated slope of each pixel with a non-uniformity correction (NUC) gain table to first determine a defective pixel.

According to an embodiment of the present invention, there is provided a thermal imaging camera comprising: a detection element array for detecting infrared rays emitted from a subject and outputting the infrared signal as an electrical signal; An analog-to-digital converter for converting an output value of the electrical signal into a digital signal; A defective pixel processing unit for detecting and correcting defective pixels among the pixels of the detection element array using the output value of the digital signal; And a nonuniformity correction unit that performs nonuniformity correction (NUC) on the output value of the digital signal, wherein the defective pixel processing unit can execute the defective pixel detection method described above.

According to an apparatus and method for automatically correcting defective pixels in a thermal camera according to an embodiment of the present invention, a thermal camera can automatically determine and correct progressive defective pixels while a user uses a thermal camera, And it is advantageous in that it is possible to prevent time and cost from being incurred.

1 is a block diagram of an exemplary thermal imaging camera equipped with a defective pixel correction apparatus according to an embodiment of the present invention;
2 is a block diagram of an engine core of a thermal imaging camera in accordance with one embodiment;
3 is a flowchart for explaining a defective pixel detection method according to the first embodiment,
4 is a flowchart for explaining a first frame generation step,
5 is a diagram for explaining a second frame generation step;
6 is a diagram for explaining an output value distribution of frame pixels,
7 is a diagram for explaining a method of calculating a slope of a pixel,
8 is a flowchart for explaining a defective pixel detection method according to the second embodiment,
9 is a flowchart for explaining a defective pixel detection method according to the third embodiment,
10 is a flowchart for explaining a defective pixel detecting method according to the fourth embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features, and advantages of the present invention will become more readily apparent from the following description of preferred embodiments with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

In this specification, when an element is referred to as being "above" (or "below", "right", or "left") another element, ) Or it may mean that a third component may be interposed therebetween. Further, in the drawings, the thickness of the components is exaggerated for an effective description of the technical content.

Also, in this specification, expressions such as 'upper', 'lower (lower)', 'left', 'right', 'front', 'rear' And it is a relative expression used for convenience of explanation based on the drawings when describing the present invention with reference to the respective drawings.

Where the terms first, second, etc. are used herein to describe components, these components should not be limited by such terms. These terms have only been used to distinguish one component from another. The embodiments described and exemplified herein also include their complementary embodiments.

In the present specification, the singular form includes plural forms unless otherwise specified in the specification. The terms "comprise" and / or "comprising" used in the specification do not exclude the presence or addition of one or more other elements.

Hereinafter, the present invention will be described in detail with reference to the drawings. In describing the specific embodiments below, various specific contents have been set forth in order to explain the invention in more detail and to aid understanding. However, it will be appreciated by those skilled in the art that the present invention may be understood by those skilled in the art without departing from such specific details. In some cases, it should be mentioned in advance that it is common knowledge in describing an invention that parts not significantly related to the invention are not described in order to avoid confusion in explaining the present invention.

1 is a block diagram of an exemplary thermal imaging camera equipped with a defective pixel correction apparatus according to an embodiment of the present invention.

The thermal camera 100 is an apparatus for photographing an infrared image of a subject such as a user. The infrared camera 100 detects infrared energy radiated from a subject, converts the detected infrared energy into an electric signal, and converts the electric signal into temperature data.

Referring to the drawings, a thermal imaging camera 100 according to an embodiment includes a lens 10, a shutter 20, a detection element array (FPA) 30, an analog-to-digital (A / D) converter 40, A core 50, an image processing unit 60, a display 70, a shutter control unit 80, and a temperature sensor 90.

The lens 10 is an infrared ray lens that transmits infrared rays radiated from a subject. The detection element array 30 is an element that detects infrared rays incident on the infrared lens 10 and converts the detected infrared rays into an electric signal. In one embodiment, the detection element array 30 may have, for example, a focal plane array (FPA) structure in which a plurality of pixels (pixels) are arranged in a two-dimensional array, but the structure is not limited thereto.

The shutter 20 has a structure similar to a shutter of a camera in general, and serves to cut off infrared rays that pass through the lens 10 and enter the detecting element array 30. In particular, in the embodiment of the present invention, in order to update the offset table used for the nonuniformity correction (NUC) of the temperature data or to block infrared rays incident on the detection element array 13 for the purpose of detecting and correcting progressive failure pixels, 20) is used. In the illustrated embodiment, the shutter 30 is disposed between the lens 10 and the detector element array 30, but in an alternative embodiment the shutter 20 may be disposed, for example, at the front of the lens 10.

The A / D converter 40 converts the output value of the electrical signal output from the detection element array 30 into a digital signal, and the output value thus converted into the digital signal is transmitted to the engine core 50.

The engine core 50 can correct the received digital signal and convert it into thermal data. Specifically, the engine core 50 performs correction processing such as non-uniformity correction (NUC) and / or defective pixel processing on the output data output from the detection element array 30 and digitized by the A / D converter 40 And converts the corrected data into a thermal image (hereinafter referred to as "thermal image") and outputs the data.

The engine core 50 can send a control signal to the shutter control unit 80 for controlling the operation of the shutter 20 as needed and the shutter control unit 80 can control the shutter 20 The opening and closing operation of the shutter 20 can be controlled.

The image signal processing unit 60 analyzes and processes the thermal image data output from the engine core 50. For example, the image signal processor 60 can perform image enhancement (e.g., enhancement of image quality, contrast enhancement, etc.) of a thermal image, temperature detection of a specific pixel, and application processing thereof.

The display device 70 displays the data output from the video signal processor 60 to the user. In one embodiment, the display device 70 may be implemented, for example, as an LCD display, but is not limited thereto.

The temperature sensor 90 is installed inside or outside the thermal imaging camera 100 to sense the temperature inside the thermal imaging camera or the ambient temperature outside. In one embodiment, the temperature information sensed by the temperature sensor 90 is transmitted to the engine core 50, and the engine core 50 can determine whether the defective pixel is operated based on the temperature information.

2 is a block diagram of an engine core 50 of a thermal imaging camera in accordance with one embodiment.

In one embodiment, the engine core 50 may include a frame generator 510, a bad pixel processor 520, a non-uniformity corrector 530, a columnar data converter 540, and a data store 550 have.

The frame generation unit 510 generates a digital signal received from the A / D converter 40 in units of image frames. Here, 'frame' means an infrared image of a subject at one point in time. In one embodiment, each pixel generates and outputs an electrical signal in accordance with the infrared rays received for each pixel of the detection element array 30, and the frame generation unit 510 generates an electrical signal (digitally converted) On a frame-by-frame basis. The generated frame may be temporarily stored in the data storage unit 550 and then processed in the bad pixel processing unit 520 or the nonuniformity correction unit 530 or the like.

In an alternative embodiment, the frame generator 510 may average a number of frames to generate one virtual frame. When the thermal camera 100 photographs a subject at a certain temperature, for example, the subject is photographed several times without photographing the subject once at this specific temperature to generate a plurality of frames, and these frames are averaged to form one virtual frame . In general, even when the image is taken at the same temperature, the temperature value may slightly change for each frame, and thus the virtual frame averaged in this way can represent a more accurate temperature value for the corresponding temperature.

The defective pixel processing unit 520 detects defective pixels in the pixels of the detection element array 30 and corrects them. The defective pixel detection method according to the embodiment of the present invention will be described later with reference to FIG. 3 to FIG.

The non-uniformity correction unit 530 refers to a predetermined non-uniformity correction (NUC) table for each frame, and corrects the temperature data value output from each pixel. In one embodiment, the NUC table is pre-created and stored in the data storage unit 550, for example, when the thermal imaging camera 100 is manufactured. The NUC table includes a gain correction value and an offset correction value for each pixel (pixel). The NUC table may be updated on the way to being used by the user after shipment of the thermal camera. In one embodiment, the thermal camera 100 stores the initial NUC table in the data storage unit 550 without overwriting the NUC table at the initial shipment, even if the NUC table is updated.

The thermal data converting unit 540 converts the data of the frames processed by the defective pixel processing unit 520 and the nonuniform correction unit 530 into matched colors in accordance with each temperature band to generate thermal data. For example, the columnar data converting unit 540 applies a RGB value matched to each temperature value of the temperature data to generate a column image. Accordingly, for example, a color thermal image in which a high temperature is displayed in a red system and a low temperature in a blue system is generated, or a black and white thermal image in which a high temperature is displayed close to white and a low temperature is displayed close to black .

3 is a flowchart for explaining a defective pixel detection method according to the first embodiment.

Referring to the drawings, the thermal imaging camera 100 determines whether to shoot a thermal image for defective pixel detection based on a predetermined time period. If it is determined to shoot a thermal image, the shutter 20 of the thermal imaging camera is closed A first frame of the column image is generated (S110).

Thereafter, the thermal imaging camera 100 determines again whether to shoot a thermal image for defective pixel detection based on the ambient temperature measured by the temperature sensor 90. When it is determined to shoot a thermal image, the shutter 20 is closed, Thereby generating a second frame of the column image (S120).

In this case, step S110 of determining whether to generate the first frame of the column image may include the concrete step shown in Fig. 4, and step S120 of determining whether to generate the second frame, As shown in FIG.

Referring to FIG. 4 for step S110 in FIG. 3, in step S111, the defective pixel processing unit 520 determines whether a preset predetermined time period has elapsed. The predetermined time period is taken into consideration to prevent the defective pixel detecting operation from being performed too often, where the 'predetermined time period' can be set as required, for example, several days, tens of days, or several months. This time period can be changed by the user.

If it is determined in step S111 that the predetermined period of time has elapsed, the process proceeds to step S112 where the defective pixel processing section 520 controls the shutter control section 80 to close the shutter 20 and capture the first frame , And sets the ambient temperature measured by the temperature sensor 90 at the time of the first frame generation as the reference temperature (S113). The execution order of the steps S112 and S113 may be changed or may be executed at the same time.

5, the defective pixel processing unit 520 of the engine core 50 continuously detects the ambient temperature sensed by the temperature sensor 90 (every predetermined time interval) It is determined whether the difference between the ambient temperature and the reference temperature is equal to or greater than a predetermined value (S121).

In this case, 'ambient temperature' refers to the temperature measured by the temperature sensor 90. For example, when the temperature sensor 90 is installed outside the thermal camera 100, the temperature outside the camera may be the ambient temperature, For example, when the temperature sensor 90 is mounted inside the thermal imaging camera, the temperature inside the camera can be the ambient temperature.

Also, the 'reference temperature' may be the reference temperature set at the time of generating the first frame, that is, the ambient temperature set in step S113 of FIG. Therefore, comparing the ambient temperature with the reference temperature in step S121 means comparing the ambient temperature at the generation of the first frame with the current ambient temperature at which the second frame is to be generated.

The 'predetermined value' when determining whether the temperature difference between the ambient temperature and the reference temperature is equal to or higher than the predetermined value may be set to, for example, 5 degrees or 10 degrees, and may be varied according to specific embodiments. Also, the user may arbitrarily set or change the 'predetermined value'.

If the difference between the ambient temperature and the reference temperature is equal to or higher than the predetermined value (i.e., the current ambient temperature is higher than or lower than the reference temperature by a predetermined value or lower) in step S121, the process proceeds to step S122, 520 control the shutter control unit 80 to close and photograph the shutter 20 to generate a second frame. Thereafter, in the step S123, counting can be started again from 0 in the predetermined time period. Alternatively, this step S123 may be performed after all the defective pixel detection and correction are completed (e.g., after step S160).

Referring again to FIG. 3, after generating the first frame and the second frame in steps S110 and S120, respectively, in step S130, the temperature of each shutter when generating the first frame and the second frame . In one embodiment, the temperature of such a shutter can be obtained from the temperature output value of the frame.

Since each of the first frame and the second frame is an image when the shutter 20 is closed and photographed, each frame will represent the temperature value of the shutter 20 when actually photographing the frame. For example, each of the first frame and the second frame has an output value distribution as shown in Fig. 6, for example.

6 is a graph illustrating a distribution according to an output value of a frame pixel, wherein X axis denotes an output value of each pixel of the frame and Y axis denotes the number of pixels having respective output values. The output value of the pixel is proportional to the temperature of the subject. That is, the output value of the pixel is higher as the temperature is higher, and the output value of the pixel is lower as the temperature is lower. Since the first frame generated in step S110 has photographed the shutter 20 having a uniform temperature as a whole, ideally, it is preferable that all pixels exhibit the same output value. However, since there is an error in each pixel and there is a defective pixel 6, respectively. Likewise, the second frame will have a distribution similar to that of FIG. At this time, however, each frame is not completely symmetric about the average as shown in FIG. 6, and each frame will have various types of distribution.

According to one embodiment, in step S130, the temperature of the shutter 20 is calculated from the pixel output value of each frame in consideration of the distribution form of such pixels.

In one embodiment, considering the error between the defective pixel and the pixels, the remaining pixels except the k pixels having the upper k output values and the k lower output values among the output values of all the pixels are used. That is, if the total number of pixels of the frame is N, the average of these output values is obtained for (N-2k) pixels, and this average value is set as the temperature of the shutter 20 at the time of generation of this frame. In this case, the k value can be set to, for example, the number of pixels which is approximately 5 to 10% of the total number of pixels (N), but it goes without saying that it can be varied according to the specific embodiment.

In step S130, the temperature of the shutter 20 at the time of generation of each frame can be calculated according to the above-described exemplary method, and the calculated shutter temperature at the time of the first frame generation is T1, Assume that the shutter temperature is T2.

Then, in step S140, the slope between the first temperature T1 and the second temperature T2 of each pixel is calculated. (I.e., the output value at time T2 - the output value at time T1) / the output value at time T2 at the time of generation of the second frame, for each pixel, (T2-T1)).

Next, in step S150, an average slope of pixels between the first frame and the second frame is calculated. In this regard, FIG. 7 shows a graph of a method of calculating the slope of a pixel. 7, the X-axis is the temperature and the Y-axis is the output value. Each pixel of the first frame at the temperature T1 at the time of generation of the first frame will be distributed according to the output value on T1 as shown. And each pixel of the second frame at the temperature T2 at the time of generating the second frame will be distributed according to the output value on T2.

In this graph, a straight line passing through the average output value at the first temperature T1 and the average output value at the second temperature T2 becomes the average slope to be obtained at step S150.

Thereafter, in step S160, a slope of each pixel is compared with an average slope to determine a defective pixel. In one embodiment, a pixel having a slope greater than or less than a predetermined value alpha at an average slope value may be determined as a defective pixel, and the predetermined value alpha may be varied according to the specific embodiment.

If defective pixels are detected according to the above-described method, the defective pixels are corrected according to a predetermined correction procedure. For example, an output value of a defective pixel may be replaced with an output value of a pixel adjacent to the defective pixel, or an average value of a plurality of adjacent pixels may be substituted.

8 is a flowchart for explaining a defective pixel detecting method according to the second embodiment.

Referring to the drawings, steps S210 to S240 of the defective pixel detection method according to the second embodiment are the same as or similar to steps S110 to S140 in the first embodiment of FIG. The first frame and the second frame are generated in steps S210 and S220 respectively and then the temperatures T1 and T2 during the generation of each frame are calculated in step S230, The slope is calculated for each pixel.

Then, in step S250, the calculated slope of each pixel is compared with the gain table of the nonuniformity correction (NUC). The slope of each pixel is the same as the gain used in NUC correction. In step S250, the slope value of each pixel calculated in step S240 is calculated for each pixel stored in the latest NUC gain table Can be compared with the gain value of the < RTI ID = 0.0 >

Thereafter, in step S260, the slope of each pixel is compared with the average slope to determine a defective pixel. In one embodiment, if the difference between the slope value for each pixel and the gain value of the NUC table is within a predetermined value, the pixel is determined to be normal. If the difference is larger than the predetermined value, it can be determined that the pixel is a defective pixel. At this time, the predetermined value may be set or changed according to a specific embodiment.

9 is a flowchart for explaining a defective pixel detection method according to the third embodiment.

Referring to the drawings, steps S310 to S360 of the defective pixel detection method according to the third embodiment are the same as or similar to the entire steps S110 to S160 of the first embodiment of FIG. That is, steps S310 to S360 are performed to compare the slope of each pixel with the average slope to determine the defective pixel first. Thereafter, in the embodiment of Fig. 9, steps S370 to S390 are additionally performed to judge the defective pixel secondarily.

That is, in step S370, the offset table of the nonuniformity correction (NUC) is updated using the second frame generated at the second temperature T2. Here, the offset refers to the Y value at the point where the slope straight line in FIG. 7 meets the Y axis. That is, since the slope is calculated for each pixel in step S340, a Y value (offset) when the straight line of the slope meets the Y axis can be calculated for each pixel, and the calculated offset value is stored in the offset table for NUC So that the offset table for NUC can be updated.

Thereafter, in step S380, each offset value of the updated NUC offset table is compared with the offset value of the first stored NUC offset table. Here, the first NUC offset table may be, for example, a NUC offset table that was first generated at the time of shipment of the thermal imaging camera 100 and stored in the data storage unit 550.

In step S380, the first offset value is compared with the offset value updated in step S370. If the difference between the two values is within a predetermined range, the pixel is determined to be normal. If the difference is outside the predetermined range, (S390). The predetermined range may be set or changed according to a specific embodiment.

10 is a flowchart for explaining a defective pixel detecting method according to the fourth embodiment.

Referring to the drawings, steps S410 to S460 of the defective pixel detection method according to the fourth embodiment are the same as or similar to the entire steps S210 to S260 of the second embodiment of FIG. That is, steps S410 to S460 are performed to compare the slope (gain) of each pixel with the gain of the NUC gain table to determine the defective pixel first. Then, in the embodiment of Fig. 10, steps S470 to S490 are additionally performed to make secondary determination of the defective pixel. The secondary determination of the defective pixel at this time can be the same as or similar to the steps (S370 to S390) of the embodiment of Fig.

That is, in step S470, the offset table of the nonuniformity correction (NUC) is updated using the second frame generated at the second temperature T2, and in step S480, the offset values of the updated NUC offset tables With the offset value of the first stored NUC offset table. If it is determined that the difference between the two values is within the predetermined range in step S380, the pixel is determined to be normal. If the difference is out of the predetermined range, the pixel is determined to be a defective pixel (S490). The predetermined range may be set or changed according to a specific embodiment.

As described above, in the embodiments of Figs. 9 and 10, whether or not a defective pixel is primarily determined according to the slope (gain) of each pixel and whether or not a defective pixel is additionally determined based on the offset of each pixel further detects a defective pixel more accurately can do. In this case, in one embodiment, only the pixel determined to be a defective pixel in both of the primary defective pixel determination according to the slope and the secondary determination according to the offset may be determined as a defective pixel, and alternatively, the primary and secondary If it is determined as a defective pixel in any one of the judgments, it may be finally determined that the defective pixel is a defective pixel.

The embodiments of the present invention have been described with reference to the drawings. However, those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the spirit and scope of the present invention as defined by the appended claims. Therefore, the scope of the present invention should not be limited by the described embodiments, but should be determined by the scope of the appended claims, as well as the appended claims.

10: Lens
20: Shutter
30: Detector element array (FPA)
40: Analog-to-Digital (A / D) Converter
50: engine core
60:
70: Display
80:
90: Temperature sensor

Claims (13)

A method for detecting defective pixels in a thermal camera,
Closing and photographing the shutter of the thermal camera based on the predetermined time period to generate a first frame of the thermal image;
Closing and capturing a shutter of the thermal camera based on ambient temperature to produce a second frame of thermal images;
Calculating a first temperature of the shutter at the time of generating the first frame and a second temperature of the shutter at the time of generating the second frame from the respective data of the first and second frames, respectively;
Calculating a slope of each pixel using the first and second frames; And
And comparing the average slope of the pixels between the first frame and the second frame with the slope of each pixel to determine a defective pixel first,
Wherein the step of generating the first frame includes setting an ambient temperature measured by the temperature sensor of the thermal camera at the time of generating the first frame to a reference temperature,
Wherein the generating of the second frame comprises:
Determining whether a difference between the ambient temperature measured by the temperature sensor and the reference temperature is equal to or greater than a predetermined value; And
And if the temperature difference is equal to or greater than a predetermined value, generating a second frame by photographing the shutter with the shutter closed. 2. The method of claim 1, wherein calculating the first temperature and the second temperature, respectively,
Calculating a first temperature of the shutter by using an average output value of pixels other than the predetermined number of pixels having a lower output value and a predetermined number of pixels having an upper output value among the output values of pixels of the first frame; And
Calculating a second temperature of the shutter by using an average output value of pixels other than the predetermined number of pixels having a lower output value and a predetermined number of pixels having an upper output value among the output values of pixels of the second frame Wherein the defective pixel detecting means detects the defective pixel of the thermal camera. 2. The method of claim 1, wherein generating the first frame comprises:
Determining whether a predetermined time period has elapsed (S111); And
And (S112) when the predetermined time period has elapsed, generating the first frame by closing and photographing the shutter (S112). delete The method according to claim 1,
Updating a non-uniformity correction (NUC) offset table using the second frame; And
And comparing the updated NUC offset table with a pre-stored NUC offset table to determine a defective pixel secondarily. 6. The method of claim 5, wherein the secondary determining comprises:
Determining whether a difference between an offset value of the updated NUC offset table of the pixel and an offset value of the previously stored NUC offset table is equal to or greater than a predetermined value for each pixel; And
And determining that the pixel is a defective pixel if the difference between the offset values is equal to or greater than a predetermined value. A method for detecting defective pixels in a thermal camera,
Closing and photographing the shutter of the thermal camera based on the predetermined time period to generate a first frame of the thermal image;
Closing and capturing a shutter of the thermal camera based on ambient temperature to produce a second frame of thermal images;
Calculating a first temperature of the shutter at the time of generating the first frame and a second temperature of the shutter at the time of generating the second frame from the respective data of the first and second frames, respectively;
Calculating a slope of each pixel using the first and second frames;
Comparing the calculated slope of each pixel with a non-uniformity correction (NUC) gain table to determine a defective pixel first;
Updating a non-uniformity correction (NUC) offset table using the second frame; And
Comparing the updated NUC offset table with a pre-stored NUC offset table to determine a defective pixel secondarily,
Wherein the secondary determining comprises:
Determining whether a difference between an offset value of the updated NUC offset table of the pixel and an offset value of the previously stored NUC offset table is equal to or greater than a predetermined value for each pixel; And
And determining that the pixel is a defective pixel if the difference between the offset values is equal to or greater than a predetermined value. 8. The method of claim 7, wherein calculating the first and second temperatures of the shutter, respectively,
Calculating a first temperature of the shutter by using an average output value of pixels other than the predetermined number of pixels having a lower output value and a predetermined number of pixels having an upper output value among the output values of pixels of the first frame; And
Calculating a second temperature of the shutter by using an average output value of pixels other than the predetermined number of pixels having a lower output value and a predetermined number of pixels having an upper output value among the output values of pixels of the second frame Wherein the defective pixel detecting means detects the defective pixel of the thermal camera. 8. The method of claim 7,
Wherein the generating the first frame comprises:
Determining whether a predetermined time period has elapsed (S111);
(S112) when the predetermined time period has elapsed, generating the first frame by closing the shutter; And
(S113) setting the ambient temperature measured by the temperature sensor of the thermal imaging camera to a reference temperature at the time of generating the first frame (S113). 10. The method of claim 9, wherein generating the second frame comprises:
Determining whether a difference between the ambient temperature measured by the temperature sensor and the reference temperature is equal to or greater than a predetermined value (S121); And
And a step (S122) of generating the second frame by closing the shutter when the temperature difference is equal to or greater than a predetermined value. delete delete In a thermal imaging camera,
A detection element array for detecting infrared rays emitted from a subject and outputting the detected infrared rays as an electrical signal;
An analog-to-digital converter for converting an output value of the electrical signal into a digital signal;
A defective pixel processing unit for detecting and correcting defective pixels among the pixels of the detection element array using the output value of the digital signal; And
And a nonuniformity correcting unit (NUC) for non-uniformly correcting the output value of the digital signal,
Wherein the defective pixel processing unit is capable of executing the defective pixel detection method according to any one of claims 1 to 3 and 5 to 10.

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