Method for generating correction information for non-uniformity correction in thermal imaging camera and non-uniformity correction method using same

Abstract

The present invention relates to a method for generating correction information for non-uniformity correction in a thermal imaging camera and a non-uniformity correction method using same in a thermal imaging camera, the method comprising the steps of: acquiring thermal images of uniform temperature surfaces corresponding to temperature pairs, each including a low temperature point and a high temperature point, captured by a thermal imaging camera; mapping, onto two-dimensional planes, the output value of each pixel of the thermal images corresponding to the temperatures of the uniform temperature surfaces; generating a linear equation, of each temperature pair, having a gain value and an offset value for each pixel on the basis of a temperature graph in which the low temperature point and the high temperature point of the temperature pair for each pixel are connected; and generating an nth-degree polynomial mapping function (n is equal to or greater than 2) for the entire captured temperature range on the basis of the linear equation of each temperature pair.

Description

Method for generating correction information for non-uniformity correction of a thermal imaging camera and non-uniformity correction method using the same

[0001] The present invention relates to a method for generating correction information to correct pixel-by-pixel output values ​​so that they have uniform output values ​​for the same input radiation amount, in relation to the fact that the infrared detector of a thermal imaging camera has different output characteristics for each pixel, and a method for correcting non-uniformity of a thermal imaging camera using the same.

[0002] Generally, a thermal image camera or infrared camera refers to a device that outputs an image formed by detecting infrared radiation emitted from a subject. Since such thermal image cameras generate images by detecting infrared radiation emitted from the object itself rather than visible light, even in the absence of light, they are utilized in dark environments, foggy places, or in fields requiring the detection of specific temperatures.

[0003] Meanwhile, the thermal imaging camera includes an infrared detector for generating thermal image data by detecting infrared radiation emitted from a subject, and a plurality of infrared sensors are installed in the infrared detector to form a focal plane array (FPA). The amount of radiation detected by one infrared sensor of the focal plane array (FPA) is output as one pixel output value.

[0004] In this case, the pixels corresponding to each infrared sensor constituting the infrared detector must output the same output value for the same amount of radiation; however, if each pixel has different detection characteristics, they output different output values ​​for the same amount of radiation.

[0005] To solve this problem, non-uniformity correction is performed on each pixel so that all pixels constituting the infrared detector exhibit the same detection characteristics.

[0006] Meanwhile, even if a thermal imaging camera is manufactured by performing non-uniformity correction in this manner, if a certain period (e.g., one year) has passed since the product was released, the detection characteristics of the infrared sensor may change or deteriorate, resulting in non-uniform output values ​​for each pixel for the same amount of radiation, and non-uniformity correction is required in such cases as well.

[0007] To perform this non-uniformity correction, a method is used in which different detection characteristics for each pixel constituting the infrared detector are represented as gain and offset values, and the output value is corrected using the gain and offset values ​​for each pixel.

[0008] In this regard, a method is used to calculate gain and offset values ​​by assuming that the subject's radiant energy and the output value at each pixel exhibit linear characteristics across the entire temperature range detected by the thermal imaging camera; however, this method presents a problem in that it is difficult to guarantee the accuracy of non-uniformity correction across the entire temperature range. For example, non-linear characteristics tend to increase in low-temperature ranges, such as sub-zero temperatures.

[0009] In addition, there is a problem in that it is difficult to reflect accurate output characteristics because the temperature of a subject (black body) having a uniform temperature surface is set at regular intervals (e.g., 10°C) over the entire temperature range (e.g., 0°C, 10°C, 20°C, 30°C, etc.) to obtain pixel output values ​​at those temperatures and then generate a linear equation based on them.

[0010] The present invention has been devised in consideration of the above points, and its technical objective is to provide a method for generating correction information for non-uniformity correction and a method for non-uniformity correction using the same, which enables the acquisition of a uniform thermal image by improving the accuracy of non-uniformity correction over the entire temperature range from low to high temperatures of the subject.

[0011] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art from the description below.

[0012] According to one embodiment of the present invention, a method for generating correction information for non-uniformity correction of a thermal imaging camera is disclosed, comprising: a step of acquiring a thermal image by capturing a uniform temperature surface corresponding to a temperature pair including a low temperature point and a high temperature point with a thermal imaging camera; a step of mapping the output value of each pixel of the thermal image corresponding to the temperature of the uniform temperature surface onto a two-dimensional plane; a step of generating a linear equation for each temperature pair having a gain value and an offset value for each pixel based on a temperature graph connecting the low temperature point and the high temperature point of each temperature pair for each pixel; and a step of generating a mapping function in the form of an n-th degree polynomial (where n is 2 or greater) for the entire range of the captured temperature range based on the linear equation of each temperature pair.

[0013] In addition, the above two-dimensional plane may include a plane with the actual temperature value and the pixel output temperature value of the uniform temperature plane as two axes.

[0014] In addition, the above temperature pairs have temperature ranges of the same size, but one of the temperature pairs may have a temperature range that overlaps with one or more adjacent temperature pairs.

[0015] In addition, each of the above temperature pairs can be set so that each low point and each high point of the temperature pair increases at regular intervals.

[0016] In addition, the above linear equation can be defined according to the following mathematical formula 1.

[0017] [Mathematical Formula 1]

[0018] y i = (Gain)x i + offset

[0019] (here, x i is the actual temperature value of the uniform temperature surface input to pixel i, y i is the output temperature value of pixel i, Gain is the gain value, and offset is the offset value)

[0020] In addition, the step of mapping the output value captured from the uniform temperature plane onto the two-dimensional plane can be repeated for each ambient temperature at which the thermal imaging camera is placed.

[0021] In addition, the mapping function can be generated by fitting a polynomial curve based on the actual temperature value and output temperature value of the uniform temperature surface derived based on the pixel-specific gain value and offset value.

[0022] In addition, the above mapping function may be a third-order polynomial following the following mathematical formula 2.

[0023] [Mathematical Formula 2]

[0024] y i = (Gain3)x i 3 + (Gain2)x i 2 + (Gain1)x i + offset

[0025] (Here, Gain1, Gain2, and Gain3 are the gain values ​​of the mapping function, and offset is the offset value of the mapping function)

[0026] Meanwhile, according to another embodiment of the present invention, a method for correcting non-uniformity of a thermal imaging camera is disclosed, comprising: a step of acquiring a thermal image by capturing a uniform temperature surface corresponding to a temperature pair including a low temperature point and a high temperature point with a thermal imaging camera; a step of mapping the output value of each pixel of the thermal image corresponding to the temperature of the uniform temperature surface onto a two-dimensional plane; a step of generating a linear equation for each temperature pair having a gain value and an offset value for each pixel based on a temperature graph connecting the low temperature point and the high temperature point of each temperature pair for each pixel; a step of generating a mapping function in the form of an n-th degree polynomial (where n is 2 or greater) for the entire range of the captured temperature range based on the linear equation of each temperature pair; and a step of correcting the output value for each pixel based on the value of a correction table calculated through the mapping function.

[0027] In addition, the non-uniformity correction method of the thermal imaging camera may further include a first defective pixel correction step of identifying and correcting defective pixels based on the result of mapping the output value of each pixel onto a two-dimensional plane.

[0028] In addition, the non-uniformity correction method of the thermal imaging camera may further include a second defective pixel correction step of identifying and removing defective pixels based on the result of correcting the output value for each pixel.

[0029] Meanwhile, according to another embodiment of the present invention, a non-uniformity correction system for a thermal imaging camera is disclosed, comprising: an original image acquisition unit for receiving an original image of a thermal image obtained by capturing a uniform temperature surface corresponding to a temperature pair including a low temperature point and a high temperature point through a thermal imaging camera; a correction information generation unit for generating correction information for non-uniformity correction using information of the original image of the thermal image obtained through the original image acquisition unit; and a pixel output value correction unit for correcting the pixel-by-pixel output value of the original image of the thermal image using the correction information of the correction information generation unit; wherein the correction information generation unit generates the correction information by: a step of mapping the output value of each pixel of the thermal image corresponding to the temperature of the uniform temperature surface onto a two-dimensional plane; a step of generating a linear equation for each temperature pair having a gain value and an offset value for each pixel based on a temperature graph connecting the low temperature point and the high temperature point of each temperature pair for each pixel; and a step of generating a mapping function in the form of an n-th degree polynomial for the entire range of the captured temperature range based on the linear equation of each temperature pair.

[0030] Furthermore, according to another embodiment of the present invention, a thermal imaging camera is disclosed, comprising: a lens for receiving infrared rays emitted from a subject; an infrared detector including a plurality of infrared sensors for sensing infrared rays received through the lens; a memory for storing correction information of a thermal imaging camera generated by the method disclosed above; and a controller for correcting pixel output values ​​of a thermal image sensed by the infrared sensors based on the correction information stored in the memory.

[0031] According to an embodiment of the present invention, a linear equation is formed in the first degree through a temperature pair including a low temperature point and a high temperature point, and correction information is generated by creating a mapping function in the form of an n-th degree polynomial for the entire temperature range based on this, thereby having the effect of improving the accuracy of non-uniformity correction across the temperature range.

[0032] In addition, according to an embodiment of the present invention, there is an advantage in that the efficiency of the non-uniformity correction process can be improved by ensuring that defective pixel correction is processed together during the non-uniformity correction process.

[0033] FIG. 1 is a block diagram showing a non-uniformity correction system for a thermal imaging camera according to one embodiment of the present invention.

[0034] FIG. 2 is a flowchart illustrating the generation of non-uniformity correction information and a non-uniformity correction method of a thermal imaging camera according to an embodiment of the present invention.

[0035] FIG. 3 is a diagram schematically illustrating the thermal image acquisition and two-dimensional planar mapping process illustrated in FIG. 2.

[0036] FIG. 4 is a diagram illustrating a temperature pair for generating non-uniformity correction information according to the embodiment shown in FIG. 2.

[0037] Figure 5 is a diagram schematically illustrating the process of generating a linear equation shown in Figure 2.

[0038] FIG. 6 is a flowchart illustrating a non-uniformity correction method for a thermal imaging camera according to another embodiment of the present invention.

[0039] FIG. 7 is a diagram schematically illustrating the defective pixel correction process illustrated in FIG. 6.

[0040] FIG. 8 is a schematic diagram showing the configuration of a thermal imaging camera to which a non-uniformity correction method according to one embodiment of the present invention can be applied.

[0041] ※ Explanation of symbols

[0042] 1: Uniform temperature surface 10: Non-uniformity correction system

[0043] 11: Original image acquisition unit 12: Correction information generation unit

[0044] 13: Pixel output value correction section 20: Total temperature pairs

[0045] 21, 22, 23, 24, 25: Individual temperature pairs 30: Original thermal image

[0046] 31: Low-temperature thermal image 33: High-temperature thermal image

[0047] 40: 2D plane 100: Thermal imaging camera

[0048] 110: Lens 120: Infrared detector

[0049] 130: Controller 140: Display

[0050] 150: Memory 160: Correction Table

[0051] The present invention is capable of various modifications and may have various embodiments; specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention. In describing the present invention, detailed descriptions of related prior art are omitted if it is determined that such detailed descriptions may obscure the essence of the present invention.

[0052] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another.

[0053] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to indicate the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0054] Hereinafter, embodiments of a method for generating correction information for non-uniformity correction of a thermal imaging camera according to the present invention and a method for correcting non-uniformity using the same will be described in detail with reference to the attached drawings. In describing with reference to the attached drawings, identical or corresponding components are given the same reference numerals, and redundant descriptions thereof will be omitted.

[0055] FIG. 1 is a block diagram showing a non-uniformity correction system for a thermal imaging camera according to one embodiment of the present invention.

[0056] Referring to FIG. 1, the non-uniformity correction system (10) of a thermal imaging camera according to the present embodiment includes an original image acquisition unit (11), a correction information generation unit (12), and a pixel output value correction unit (13).

[0057] The original image acquisition unit (11) is configured to acquire an original thermal image (30, see FIG. 3) by capturing a uniform temperature surface (1) through a thermal imaging camera (100). For non-uniformity correction, the thermal imaging camera (100) captures a uniform temperature surface (1) where the entire radiating surface outputs the same temperature, and usually a black body is used to capture the uniform temperature surface (1). The black body is configured to enable the uniform output of a temperature set by the user on the uniform temperature surface within the shooting range of the thermal imaging camera (100).

[0058] To correct non-uniformity, a black body is set to a preset temperature, and a uniform temperature surface (1) of the black body is captured by a thermal imaging camera (100). The original image acquisition unit (11) is configured to acquire a thermal image original image (30) from the thermal imaging camera (100). Multiple temperatures for non-uniformity correction may be set, and shooting may be performed for each set temperature. The original image acquisition unit (11) may acquire a thermal image original image (30) for each temperature and store them in a data storage means.

[0059] The correction information generation unit (12) generates correction information for non-uniformity correction using information of the original thermal image (30) obtained through the original image acquisition unit (11). According to the present invention, the correction information for non-uniformity correction (which may also be referred to as 'non-uniformity correction information') may include gain values ​​(Gain1, Gain2, Gain3) and offset values ​​(Offset) that constitute a mapping function in the form of an n-th degree polynomial, and a correction table (160, see FIG. 8) may be generated using these gain values ​​(Gain1, Gain2, Gain3) and offset values ​​(Offset). The correction table (160) may include correction information for each pixel, for example, gain values ​​(Gain1, Gain2, Gain3) and offset values ​​(Offset) for each pixel, or values ​​calculated from them. A specific method and process for generating non-uniformity correction information will be described in detail later.

[0060] The pixel output value correction unit (13) is configured to correct the output value for each pixel based on the correction information generated by the correction information generation unit (12), specifically the correction value of the correction table (160). The pixel output value correction unit (13) can be configured to correct the output setting so as to correct the output value for each pixel and output it based on the input value.

[0061] For example, the term "part" used in this embodiment refers to a software or hardware component such as an FPGA or ASIC, and the "part" performs certain roles. However, the meaning of "part" is not limited to software or hardware; the "part" may be configured to reside in an addressable storage medium or configured to execute one or more processors. Accordingly, as an example, the "part" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and "parts" may be combined into a smaller number of components and "parts" or further separated into additional components and "parts." Furthermore, the components and "parts" may be implemented to execute one or more CPUs within a device or secure multimedia card.

[0062] In this way, the non-uniformity correction system (10) according to one embodiment of the present invention generates correction information for each of a plurality of pixels constituting an infrared detector (detector, 120) of a thermal imaging camera (100), and corrects the original thermal image (30) through a correction value for each of a plurality of pixels using the same, thereby improving the pixel-by-pixel output uniformity of the thermal imaging camera (100), and thereby enabling the thermal imaging camera to stably perform thermal image processing.

[0063] FIG. 2 is a flowchart illustrating the generation of non-uniformity correction information and a non-uniformity correction method of a thermal imaging camera according to one embodiment of the present invention.

[0064] Referring to FIG. 2, a method for generating non-uniformity correction information for a thermal imaging camera according to the present embodiment is described as follows: First, a uniform temperature surface (1) corresponding to a temperature pair including a low temperature point and a high temperature point is captured to obtain a thermal image original image (S10). As previously described, this is performed by an original image acquisition unit (11) connected to the thermal imaging camera acquiring an image of the uniform temperature surface (1) captured by the thermal imaging camera.

[0065] The temperature plane of the uniform screen where the thermal imaging camera acquires the original image is set by a plurality of temperature pairs including low temperature points and high temperature points.

[0066] FIG. 3 is a diagram schematically illustrating the process of acquiring a thermal image and mapping a two-dimensional plane (40) as illustrated in FIG. 2, and FIG. 4 is a diagram illustrating a temperature pair for generating non-uniformity correction information according to the embodiment illustrated in FIG. 2.

[0067] As shown in FIG. 4, each temperature pair includes a low temperature point and a high temperature point, and can be expressed as, for example, (L1, H1), (L2, H2), (L3, H3), (L4, H4), (L5, H5), … etc., where L1, L2, L3, L4, L5 etc. represent low temperature points and H1, H2, H3, H4, H5 etc. represent high temperature points, and these are values ​​within the entire temperature range that can be captured by a thermal imaging camera.

[0068] The temperature range of each temperature pair (i.e., the difference between the high and low points) can be set to be identical to one another. Additionally, one of the temperature pairs may have a temperature range that overlaps with one or more adjacent temperature pairs. Furthermore, the low and high points of each temperature pair can be set to increase at regular temperature intervals.

[0069] The total temperature range (20) exemplified in FIGS. 3 and 4 includes a plurality of individual temperature pairs (21, 22, 23, 24, 25, etc.) having the same temperature range, and these individual temperature pairs (21, 22, 23, 24, 25) can be expressed as (-30℃, 40℃), (-20℃, 50℃), (-10℃, 60℃), (0℃, 70℃), (10℃, 80℃), etc. In this case, each individual temperature pair (21, 22, 23, 24, 25) has a temperature range of 70℃, and the low temperature point and high temperature point are set to increase at a certain interval (10℃). Also, one of the individual temperature pairs (21, 22, 23, 24, 25) may have a temperature range that overlaps with one or more adjacent other temperature pairs.

[0070] As exemplified in this embodiment, each individual temperature pair (21, 22, 23, 24, 25) is set such that the low temperature point and the high temperature point increase sequentially by 10°C, and the first individual temperature pair (21) has a temperature range that overlaps with the second individual temperature pair (22) by 60°C, with the third individual temperature pair (23) by 50°C, with the fourth individual temperature pair (24) by 40°C, and with the fifth individual temperature pair (25) by 30°C.

[0071] After setting each temperature pair in this way, a thermal image of the uniform temperature surface (1) corresponding to each temperature pair is obtained, and FIG. 3 schematically illustrates this. In FIG. 3, a thermal image of the uniform temperature surface (1) corresponding to the low temperature point is shown as a low temperature point thermal image (31), and a thermal image of the uniform temperature surface (1) corresponding to the high temperature point is shown as a high temperature point thermal image (33).

[0072] When the acquisition of the original thermal image (30) that captures the low temperature point and high temperature point temperature planes is completed in this manner, the output value of each pixel of the thermal image corresponding to the temperature of the uniform temperature plane (1) is mapped onto a two-dimensional plane (40) through the correction information generation unit (12) (S20). As illustrated in FIG. 3, the two-dimensional plane (40) may be a plane with the actual temperature value of the uniform temperature plane (1) and the pixel output temperature value as two axes, and this embodiment exemplifies a plane with the actual temperature value of the uniform temperature plane (1) as the x-axis (horizontal axis) and the pixel output temperature value as the y-axis (vertical axis).

[0073] Figure 3 illustrates a graph in which points corresponding to the output temperature values ​​of the uniform temperature plane (1) for each pixel are mapped onto a two-dimensional plane (40). According to this, a number of points equal to the number of pixels multiplied by the number of temperature points measured by the thermal imaging camera are mapped onto the two-dimensional plane (40).

[0074] Meanwhile, this process, that is, acquiring a thermal image of a uniform temperature surface (1) and mapping it onto a two-dimensional plane (40), can be repeated for each ambient temperature at which the thermal imaging camera (100) is placed, i.e., the operating environment temperature of the thermal imaging camera. The imaging of a black body through the thermal imaging camera (100) is generally performed with the thermal imaging camera (100) installed inside an insulated chamber, and the ambient temperature can be set by varying the temperature of the insulated chamber. By calculating the correlation between the temperature of the uniform temperature surface (1) and the output temperature value per pixel according to the ambient temperature, a correction value for the corresponding output temperature value can be calculated based on this, and it is possible to map this onto the same two-dimensional plane (40).

[0075] Next, through the correction information generation unit (12), a linear equation having gain and offset values ​​for each pixel is generated based on a temperature graph connecting the low temperature point and the high temperature point of each pixel temperature pair (S30). FIG. 5 is a diagram schematically illustrating the process of generating such a linear equation.

[0076] The graph in Fig. 5 is for temperature pairs (10°C, 80°C) with a low temperature point of 10°C and a high temperature point of 80°C, and for pixels 1 to N, it shows multiple straight line graphs connecting the low temperature point and the high temperature point for each pixel.

[0077] Based on such multiple graphs, a linear equation having gain and offset values ​​for each pixel is generated, and the linear equation can be expressed as Equation 1 below.

[0078] [Mathematical Formula 1]

[0079] y i = (Gain)x i + offset

[0080] (here, x i is the actual temperature value of the uniform temperature surface (1) input to pixel i, y i represents the output temperature value of pixel i, Gain represents the gain value, and offset represents the offset value)

[0081] In mathematical formula 1, the gain value corresponds to the average value of the slope of the straight line for each pixel, and the offset value for each pixel can be calculated from the difference between the straight line graph for each pixel with the slope value corrected and the straight line graph before correction through the average value.

[0082] This process is repeated for each pair of temperatures, and for each pair of temperatures, a linear equation such as Equation 1 above and the corresponding gain and offset values ​​are calculated.

[0083] Referring again to FIG. 2, the correction information generation unit (12) generates a mapping function in the form of an n-th degree polynomial (where n is 2 or greater) for the entire shooting temperature range based on the linear equation of each temperature pair calculated through the above process (S40).

[0084] Based on the pixel-wise gain and offset values ​​of the linear equations of each temperature pair derived above, the output temperature value for the actual temperature value of the uniform temperature surface (1) can be calculated, and this is x of the n-th degree polynomial i and y i By substituting values ​​and fitting the polynomial curve, the coefficient values ​​of the n-th degree polynomial can be calculated.

[0085] It is advisable to design the mapping function in the form of odd terms based on the shape of the curve, and since the amount of computation for fitting increases significantly starting from the 5th-degree polynomial, it is desirable to set it as a 3rd-degree polynomial.

[0086] When the mapping function takes the form of a third-order polynomial, the mapping function can be expressed as shown in Equation 2 below.

[0087] [Mathematical Formula 2]

[0088] y i = (Gain3)x i 3 + (Gain2)x i 2 + (Gain1)x i + offset

[0089] (here, x i is the actual temperature value of the uniform temperature surface (1) input to pixel i, y i is the output temperature value of pixel i, Gain1, Gain2, Gain3 are gain values, and offset is the offset value)

[0090] By generating a mapping function as described above, gain values ​​and offset values ​​for each pixel can be calculated, and based on this, a correction table (160) as shown in [Table 1] below can be generated.

[0091]

[0092] Pixel position information Gain value Offset value Gain1 Gain2 Gain3 OffsetP1(P 1x .P 1y )Gain 1,1 Gain 2,1 Gain 3,1 Offset1P2(P 2x .P 2y )Gain 1,2 Gain 2,2 Gain 3,2 Offset2… … … … … … P i (P ix ,P iy )Gain 1,i Gain 2,i Gain 3,i Offset i … … … … … … P N (P Nx ,P Ny )Gain 1,N Gain 2,N Gain 3,N Offset N

[0093] Meanwhile, it is also possible to construct the correction table (160) with values ​​calculated from them instead of the gain values ​​and offset values ​​in the correction table of Table 1 above.

[0094] For example, a correction table (160) can be constructed using the difference between the gain value for each pixel and the average gain value (i.e., the average value of the gain values ​​of all pixels). Additionally, it is possible to construct a correction table (160) using the difference between the offset value for each pixel and the average offset value (i.e., the average value of the offset values ​​of all pixels), thereby reducing the amount of data stored.

[0095] Correction information for non-uniformity correction can be generated through the above process, and the pixel output value correction unit (13) performs non-uniformity correction by correcting the output value for each pixel using this correction information, specifically, the correction value of the correction table (160).

[0096] In the flowchart illustrated in FIG. 2, the process from S10 to S40 represents the process of generating correction information for non-uniformity correction of a thermal imaging camera, and if the process of S50 is additionally performed, non-uniformity correction of the thermal imaging camera is achieved. In other words, the method for correcting non-uniformity of a thermal imaging camera according to the present embodiment can be performed by including a series of processes following S10 to S50 described above.

[0097] FIG. 6 is a flowchart illustrating a non-uniformity correction method for a thermal imaging camera according to another embodiment of the present invention.

[0098] The non-uniformity correction method of a thermal imaging camera according to the present embodiment may additionally perform steps (S25, S55) of identifying and correcting bad pixels. To this end, the non-uniformity correction system (10) of a thermal imaging camera according to the present embodiment may additionally provide a bad pixel correction unit in the configuration shown in FIG. 1.

[0099] Specifically, regarding the non-uniformity correction method of a thermal imaging camera according to the present embodiment, the step (S10) of acquiring a thermal image for a uniform temperature surface (1) corresponding to a plurality of temperature pairs including a low temperature point and a high temperature point, and the step (S20) of mapping the output value of each pixel of the thermal image corresponding to the temperature of the uniform temperature surface (1) onto a two-dimensional plane (40) can be performed in the same way as in the previous embodiment, and the explanation thereof is replaced with the previous explanation.

[0100] As the next step, the bad pixel correction unit performs a first bad pixel correction step (S25) to identify and correct bad pixels based on the result of mapping the output value of each pixel onto a two-dimensional plane (40). FIG. 7 is a diagram schematically illustrating the bad pixel correction process illustrated in FIG. 6.

[0101] As illustrated in FIG. 7, by mapping the output value of each pixel onto a two-dimensional plane (40), a certain range in which the output value of the pixel is output can be set through predetermined gain and offset values, and a maximum and minimum range indicated by the red straight line in FIG. 7 can be set. Here, pixels located in a range outside the maximum and minimum ranges can be set as bad pixels, and a correction process can be performed thereon.

[0102] Correction of bad pixels can be performed using known methods, for example, cubic interpolation using surrounding pixels, or spline interpolation (spline, b-spline, etc.).

[0103] Next, through the correction information generation unit (12), a step (S30) is performed to generate a linear equation for each temperature pair based on a temperature graph connecting the low temperature point and the high temperature point of each temperature pair, and a step (S40) is performed to generate a mapping function in the form of an n-th degree polynomial for the entire shooting temperature range based on the linear equation of each temperature pair. Then, through the pixel output value correction unit (13), the output value for each pixel is corrected based on the correction value of the correction table (160) calculated through the mapping function (S50). These processes can be performed in the same way as in the previous embodiment, and the explanation thereof is substituted with the previous explanation.

[0104] Next, a second bad pixel correction step is performed to identify and remove bad pixels based on the result of correcting the output value for each pixel through the bad pixel correction unit (S55). The second bad pixel correction step is performed in the same manner as the first bad pixel correction step described above. This step is a process of checking whether the corrected pixel output value, i.e., the pixel output value reflecting non-uniformity correction, using correction information, i.e., gain value and offset value, deviates from the maximum and minimum ranges following a predetermined gain value, thereby making it possible to minimize the output of bad pixels.

[0105] FIG. 8 is a schematic diagram showing the configuration of a thermal imaging camera to which a non-uniformity correction method according to one embodiment of the present invention can be applied.

[0106] Although it is possible to perform non-uniformity correction for a thermal imaging camera using the non-uniformity correction method and system described above, it is also possible to provide a non-uniformity correction function to the thermal imaging camera (100) itself, as exemplified in this embodiment. Accordingly, it is also possible to configure the thermal imaging camera (100) to automatically perform non-uniformity correction when a preset condition (correction period, rate of change of pixel output value, etc.) is met.

[0107] A thermal imaging camera (100) according to the present embodiment includes a lens (110) that receives infrared rays emitted from a subject, an infrared detector (120) that includes a plurality of infrared sensors that sense infrared rays received through the lens (110), and a controller (130) that generates an output signal of a thermal image based on the detection signal of the infrared detector (120).

[0108] A thermal imaging camera (100) may be equipped with a display (140) for outputting a thermal image, and a controller (130) applies an output signal to the display (140) so that the display (140) outputs a thermal image.

[0109] The thermal imaging camera (100) may be equipped with a memory (150) for storing various information, and information for correcting non-uniformity of the thermal imaging camera in relation to the present invention, for example, a correction table (160), may be stored.

[0110] When a preset condition is met, the controller (130) extracts pixel-specific correction values ​​from the correction table (160) of the memory (150), corrects the pixel output value using the corresponding correction values, and thereby obtains a uniform thermal image. According to this, if non-uniformity correction is required during the use of the thermal imaging camera (100), there is an advantage that the thermal imaging camera (100) can perform non-uniformity correction on its own without visiting a location for non-uniformity correction of the thermal imaging camera (100).

[0111] Meanwhile, the method for generating non-uniformity correction information of a thermal imaging camera and the non-uniformity correction method according to the embodiments of the present invention described above may be implemented in the form of program code that can be executed through various computer components and recorded on a non-transient computer-readable recording medium. The computer-readable recording medium may include program code, data files, data structures, etc., either alone or in combination. The program code recorded on the computer-readable recording medium may be specially designed and configured for the present invention or may be known and available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs and DVDs; magneto-optical media such as floptical disks; and hardware devices specially configured to store and execute program code, such as ROM, RAM, and flash memory. Examples of program code include machine code, such as that generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc. A hardware device may be changed into at least one software module to perform processing according to the present invention, and vice versa.

[0112] Although the present invention has been described above with reference to specific embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as described in the following claims.

Claims

1. A step of acquiring a thermal image by capturing a uniform temperature surface corresponding to a temperature pair including a low temperature point and a high temperature point using a thermal imaging camera; A step of mapping the output value of each pixel of the thermal image corresponding to the temperature of the uniform temperature surface onto a two-dimensional plane; A step of generating a linear equation for each temperature pair having gain values ​​and offset values ​​for each pixel based on a temperature graph connecting the low point and high point of the temperature pair for each pixel; and A method for generating correction information for non-uniformity correction of a thermal imaging camera, comprising the step of generating a mapping function in the form of an n-th degree polynomial (where n is 2 or greater) for the entire range of the shooting temperature based on a linear equation of each temperature pair.

2. In Paragraph 1, A method for generating correction information for non-uniformity correction of a thermal imaging camera, characterized in that the above two-dimensional plane is a plane having the actual temperature value of the uniform temperature plane and the pixel output temperature value as two axes.

3. In Paragraph 1, A method for generating correction information for non-uniformity correction of a thermal imaging camera, characterized in that the above temperature pairs have temperature ranges of the same size, and one of the temperature pairs has a temperature range that overlaps with one or more adjacent temperature pairs.

4. In Paragraph 3, A method for generating correction information for non-uniformity correction of a thermal imaging camera, characterized in that each of the above temperature pairs is set such that each low point and each high point of the above temperature pair increases at a constant interval.

5. In Paragraph 1, A method for generating correction information for non-uniformity correction of a thermal imaging camera, characterized in that the above linear equation follows the following mathematical formula 1. [Mathematical Formula 1] y i = (Gain)x i + offset (here, x i is the actual temperature value of the uniform temperature surface input to pixel i, y i is the output temperature value of pixel i, Gain is the gain value, and offset is the offset value) 6. In Paragraph 1, A method for generating correction information for non-uniformity correction of a thermal imaging camera, characterized in that the step of mapping the output value of the uniform temperature surface captured above onto the two-dimensional plane is repeated for each ambient temperature at which the thermal imaging camera is placed.

7. In paragraph 1, the mapping function is, A method for generating correction information for non-uniformity correction of a thermal imaging camera, characterized by being generated by fitting a polynomial curve based on the output temperature value for the actual temperature value of the uniform temperature surface derived based on the gain value and offset value per pixel.

8. In Paragraph 1, A method for generating correction information for non-uniformity correction of a thermal imaging camera, characterized in that the above mapping function is a third-order polynomial following the following mathematical formula 2. [Mathematical Formula 2] y i = (Gain3)x i 3 + (Gain2)x i 2 + (Gain1)x i + offset (Here, Gain1, Gain2, and Gain3 are the gain values ​​of the mapping function, and offset is the offset value of the mapping function) 9. A step of obtaining a thermal image by capturing a uniform temperature surface corresponding to a temperature pair including a low temperature point and a high temperature point using a thermal imaging camera; A step of mapping the output value of each pixel of the thermal image corresponding to the temperature of the uniform temperature surface onto a two-dimensional plane; A step of generating a linear equation for each temperature pair having gain and offset values ​​for each pixel based on a temperature graph connecting the low point and high point of the temperature pair for each pixel; A step of generating a mapping function in the form of an n-th degree polynomial (where n is 2 or greater) for the entire range of the shooting temperature range based on the linear equation of each temperature pair; and A method for correcting non-uniformity in a thermal imaging camera, comprising the step of correcting the output value for each pixel based on the value of the correction table calculated through the above mapping function.

10. In Paragraph 9, A method for correcting non-uniformity in a thermal imaging camera, further comprising: a first defective pixel correction step for identifying and correcting defective pixels based on the result of mapping the output value of each pixel above onto a two-dimensional plane.

11. In Paragraph 10, A method for correcting non-uniformity in a thermal imaging camera, characterized by further including a second defective pixel correction step of identifying and removing defective pixels based on the result of correcting the output value for each pixel.

12. An original image acquisition unit for receiving an original image of a thermal image obtained by capturing a uniform temperature surface corresponding to a temperature pair including a low temperature point and a high temperature point using a thermal imaging camera; A correction information generation unit that generates correction information for non-uniformity correction using information of the original image of the thermal image obtained through the original image acquisition unit; and A pixel output value correction unit that corrects the pixel-by-pixel output value of the original image of the thermal image using the correction information of the correction information generation unit; The above correction information generation unit is, A step of mapping the output value of each pixel of the thermal image corresponding to the temperature of the uniform temperature surface onto a two-dimensional plane; A step of generating a linear equation for each temperature pair having gain values ​​and offset values ​​for each pixel based on a temperature graph connecting the low point and high point of the temperature pair for each pixel; and A non-uniformity correction system for a thermal imaging camera, characterized by generating correction information through the step of generating a mapping function in the form of an n-th degree polynomial for the entire range of the shooting temperature based on a linear equation of each temperature pair.

13. A lens that receives infrared rays emitted from a subject; An infrared detector comprising a plurality of infrared sensors that sense infrared light received through the lens; A memory for storing correction information of a thermal imaging camera generated by a method according to any one of claims 1 to 8; and A thermal imaging camera comprising: a controller that corrects the pixel output value of a thermal image sensed by the infrared sensor based on correction information stored in the memory.

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