Infrared camera

Abstract

To provide an infrared camera capable of miniaturizing hardware configuration and obtaining more accurate image data.SOLUTION: An infrared camera 1 includes: an imaging part 6 including an infrared detection element 6a; a shutter 4 for opening / closing an optical path of an infrared ray; an element temperature sensor 7 for detecting a temperature of the infrared detection element 6a; an image data generation part 21 for generating image data by using a gain coefficient and an offset coefficient on the basis of an output value from the infrared detection element 6a; a reference gain coefficient calculation part 19 for calculating a reference gain coefficient being the sensitivity of the infrared detection element 6a; a gain adjustment coefficient calculation part 15 for calculating a gain adjustment coefficient for adjusting an error caused by the element temperature sensor 7; and an offset coefficient calculation part 17 for calculating the offset coefficient. The image data generation part 21 calculates a gain coefficient A on the basis of the reference gain coefficient and the gain adjustment coefficient.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an infrared camera having an imaging section configured by arranging a plurality of infrared detection elements on a two-dimensional plane. [Background technology]

[0002] Conventionally, an infrared camera has been proposed in which the imaging section is composed of a thermal, uncooled infrared detection element known as a bolometer (Patent Document 1). This infrared detection element changes its resistance value when it absorbs infrared rays, and outputs a voltage value corresponding to the amount of incident light when a current is passed through it. When an image of an object is captured, that is, when infrared rays emitted from the object are absorbed by the infrared detection element, a voltage value corresponding to the incident energy is output, and the temperature of the object can be calculated by calibrating the output voltage value based on the sensitivity obtained in advance.

[0003] It is known that the sensitivity of this infrared detection element varies from one element to another. Conventionally, generally, an image of an object at two different known temperatures T1 and T2, for example, a blackbody furnace (a device that approximates a blackbody), is captured, and the output V of each infrared detection element n obtained at that time is measured. n and the temperature T of the object to be imaged, the sensitivity of each infrared detection element n is calculated.

[0004] More specifically, the output V n The relationship between temperature T and output V1 at temperatures T1 and T2 is n ,V2 n From the two data points, the sensitivity coefficient a n and offset coefficient b n It is approximated by the following equation, which is a linear function using V n =a n ×T+b n Therefore, the temperature T of the object to be imaged can be calculated by the following formula: T=(V n -b n ) / a n =V n / an -b n / a n =V n ×A n +B n

[0005] In conventional infrared cameras, the sensitivity coefficient A for calibration is used to increase the calculation speed. n (=1 / a n ), and offset coefficient B n (=-b n / a n ) is calculated in advance and stored in memory as a data table, and the output V of each infrared detection element n is calculated according to the above formula. n The temperature T of the object to be imaged is calculated from the calculated temperature T, and image data including a temperature component is generated from the calculated temperature T, for example, image data obtained by converting the temperature data into brightness data.

[0006] Furthermore, the infrared detection element has a characteristic that its sensitivity changes as its temperature rises due to absorption of infrared rays. For this reason, in the past, the calibration sensitivity coefficient A n and the calibration offset coefficient B n is acquired in advance and stored as a data table, and the calibration sensitivity coefficient A according to the temperature of the infrared detection element at the time of imaging is calculated. n and the calibration offset coefficient B n The image data is generated using the above. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-193194 Summary of the Invention [Problem to be solved by the invention]

[0008] However, as in the conventional method, the calibration sensitivity coefficient A according to the temperature of each infrared detection element is not calculated. nand the calibration offset coefficient B n If the above is stored in memory as a data table, the calculation speed increases, but a large capacity memory is required, and the hardware configuration becomes excessive. In other words, the number of circuit components increases, which increases costs, and the number of images acquired to be used in calculating the data table also increases, resulting in the problem of measurement taking a long time.

[0009] For example, if the ambient temperature of the infrared camera is -20°C to 50°C, and the temperature of each infrared detection element is in the range of -20°C to 50°C in 5°C increments, the calibration sensitivity coefficient A n and the calibration offset coefficient B n is acquired in advance and stored in the memory, the calibration sensitivity coefficient A n and the calibration offset coefficient B n In addition to the problem of the hardware configuration becoming excessively large, the preparatory work (calibration process) requires the temperature of the blackbody furnace to be set in 5°C increments, which is a time-consuming and cumbersome process, and this results in a huge load.

[0010] The calibration offset coefficient B n In the case of an infrared camera equipped with a shutter, the output V output from each infrared detection element when the shutter is closed is ns and the shutter temperature Ts, the calibration offset coefficient B is calculated using the following formula: n By performing this calibration before imaging with the infrared camera, the calibration offset coefficient B can be calculated. n Therefore, the calibration offset coefficient B according to the temperature of the infrared detector element can be calculated. n does not need to be stored in memory, but the calibration sensitivity coefficient A n Regarding the second aspect, it is still necessary to acquire and store data for each predetermined temperature for each infrared detection element in advance, and the above problem remains. B n =-V ns ×A n +T S However, A n is the calibration sensitivity coefficient according to the temperature of the infrared detection element at the time of imaging.

[0011] The present invention has been made in consideration of the above-mentioned circumstances, and has as its object to provide an infrared camera that can make the hardware configuration compact and reduce the burden of calibration. [Means for solving the problem]

[0012] To solve the above problems, the present invention provides: an imaging unit including a plurality of infrared detection elements arranged in x rows and y columns on a two-dimensional plane; a lens that condenses infrared light emitted from an object to be imaged onto the imaging unit; a shutter disposed between the lens and the imaging unit or in front of the lens, for opening and closing an optical path of infrared light that passes through the lens and is focused on the imaging unit; an element temperature sensor for detecting the temperature of the infrared detection element; a shutter temperature sensor that detects the temperature of the shutter; an image data generation unit that generates image data Y(x,y) of the image capture target based on an output value X(x,y) from the infrared detection element, using a gain coefficient A(x,y) and an offset coefficient B(x,y) that are coefficients for determining a correlation between the output value X(x,y) and image data Y(x,y) according to the following formula 1; A reference gain coefficient A(x, y) is a coefficient for calculating the gain coefficient A(x, y) set for the output value X(x, y), and corresponds to the sensitivity of each infrared detection element. r a reference gain coefficient calculation unit that calculates (x, y); The reference gain coefficient A r a gain adjustment coefficient calculation unit that calculates a gain adjustment coefficient FT, which is a coefficient set for (x, y) and is a coefficient for adjusting an error caused by the element temperature sensor; an offset coefficient calculation unit that calculates an offset coefficient B(x, y), The image data generating unit uses the reference gain coefficient A calculated by the reference gain coefficient calculating unit. r The infrared camera is configured to calculate the gain coefficient A(x, y) in accordance with the following equation 2 based on (x, y) and the gain adjustment coefficient FT calculated by the gain adjustment coefficient calculation unit. (Equation 1) Y(x,y)=A(x,y)×X(x,y)+B(x,y) (Equation 2) A(x,y)=A r (x,y)×FT Here, the x is an integer from 1 to n, and the y is an integer from 1 to i.

[0013] In this infrared camera, the image data generation unit generates image data Y(x,y) of the object to be imaged based on the output value X(x,y) from the infrared detection element, using a gain coefficient A(x,y) and an offset coefficient B(x,y), which are coefficients for determining the correlation between the output value X(x,y) and image data Y(x,y), in accordance with the above formula 1. Formula 1 is a calculation formula based on so-called point-to-point correction.

[0014] The gain coefficient A(x, y) is calculated by the image data generating unit according to the above formula 2 as the reference gain coefficient A r It is calculated using (x, y) and the gain adjustment coefficient FT. Note that the reference gain coefficient A r (x, y) corresponds to the sensitivity of each infrared detection element and is calculated by the reference gain coefficient calculation unit, and the gain adjustment coefficient FT is calculated by the reference gain coefficient A r The coefficients are set for (x, y) to adjust the error caused by the element temperature sensor, and are calculated by the gain adjustment coefficient calculation unit. Also, the offset coefficient B(x, y) is calculated by the offset coefficient calculation unit.

[0015] As described above, the infrared camera according to the present invention can generate image data through the processes of the reference gain coefficient calculation section, the gain adjustment coefficient calculation section, the offset coefficient calculation section, and the image data generation section.

[0016] Therefore, there is no need to store a huge amount of calibration data as in the past, and the hardware configuration can be made compact, and the load for acquiring the calibration data can be reduced.

[0017] Further, in the present invention, the reference gain coefficient calculation unit of the above aspect (first aspect) calculates energy T equivalent to k [°C] when the temperature of the image capturing object is k [°C]. k and the output value X from each infrared detection element at that time k (x, y), and the energy T equivalent to j [°C] when the temperature of the object to be imaged is j [°C] j and the output value X from each infrared detection element at that time j Using (x, y), the reference gain coefficient A is calculated according to the following formula 3. r It is possible to adopt a mode (second mode) configured to calculate (x, y). (Equation 3) A r (x,y)=(T k -T j ) / (X k (x,y)-X j (x,y) However, k>j.

[0018] Further, in the above aspect (first aspect), the gain adjustment coefficient calculation unit calculates an output value X from each infrared detection element when the temperature of the image capture object is k [°C]. k (x, y) and the output value X from each infrared detection element when the temperature of the imaged object is j [°C] j The sensitivity ratio expressed as the ratio of (x, y) and the output value FPA from the element temperature sensor are calibrated FPA. ad It is possible to adopt an aspect (third aspect) configured to calculate the gain adjustment coefficient FT according to the following equation 4, which is derived from the relationship: (Equation 4) FT=p×(FPA ad ) 2 +q×(FPA ad )+r where p, q, and r are predetermined coefficients

[0019] In the third aspect, the offset coefficient calculation unit calculates an output value X output from the infrared detection element when the shutter is closed. s (x, y), and the energy corresponding to the shutter temperature, which is the output value from the shutter temperature sensor, is T s and an aspect (fourth aspect) configured to calculate the offset coefficient B(x, y) according to the following equation 5 can be adopted. (Equation 5) B(x,y)=-A r (x,y)×FT×X s (x,y)+T s [Effects of the Invention]

[0020] As described above, the infrared camera according to the present invention can generate image data through the processes of the reference gain coefficient calculation unit, gain adjustment coefficient calculation unit, offset coefficient calculation unit, and image data generation unit. Therefore, there is no need to store a huge amount of calibration data as in the past, which allows for a compact hardware configuration and reduces the load required to obtain calibration data. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a block diagram showing a schematic configuration of an infrared camera according to an embodiment of the present invention; [Figure 2] 10 is a graph showing the relationship between the temperature detected by the element temperature sensors of a plurality of infrared cameras and the environmental temperature. [Figure 3] 10 is a graph showing the relationship between the ambient temperature and the detected temperature of an element temperature sensor after correcting errors between a plurality of infrared cameras. [Figure 4] 10 is a graph showing the relationship between the sensitivity ratio of the infrared detection elements and the calibration element temperature in a plurality of infrared cameras. [Figure 5]10 is a graph showing the relationship between the sensitivity ratio of an infrared detection element, in which errors between a plurality of infrared cameras have been corrected, and the temperature of the calibration element. [Figure 6] 10 is a graph showing the relationship between the reciprocal of the sensitivity ratio of an infrared detection element and the calibration element temperature. [Figure 7] 10 is a graph showing the relationship between the output value Xs(x, y) of the infrared detection element and the calibration element temperature (FPAad) when an image of a black body at 40° C. is captured. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0023] Figure 1 is a block diagram showing the schematic configuration of an infrared camera according to one embodiment of the present invention. As shown in Figure 1, the infrared camera 1 of this example comprises a housing 2, and within this housing 2 are arranged a lens 3, a shutter 4, a shutter temperature sensor 5, an imaging unit 6, an element temperature sensor 7, and a data processing unit 8.

[0024] The lens 3 is disposed in the opening of the housing 2 so as to close the opening, and focuses infrared rays emitted from an object to be imaged onto the imaging unit 6, which is disposed in parallel at the rear with an appropriate gap. The shutter 4 is disposed between the lens 3 and the imaging unit 6, and is driven by a drive unit (not shown) to open and close the optical path of the infrared rays that pass through the lens 3 and are focused onto the imaging unit 6.

[0025] The imaging unit 6 includes a plurality of infrared detection elements 6a arranged in x rows and y columns on a two-dimensional plane. The infrared detection elements 6a are thermal, uncooled elements known as bolometers, and each infrared detection element 6a outputs a voltage value corresponding to the amount of incident light, which is input to the data processing unit 8.

[0026] A shutter temperature sensor 5 is attached to the shutter 4, and the temperature of the shutter 4 is input from this shutter temperature sensor 5 to a data processing unit 8. In addition, an element temperature sensor 7 is attached to the imaging unit 6, and data related to the temperature of the infrared detection element 6a is input from this element temperature sensor 7 to the data processing unit 8.

[0027] The data processing unit 8 comprises A / D converters 9, 10, and 11, a changeover switch 12, a p, q, and r coefficient memory unit 13, a sensor temperature correction value memory unit 14, a gain adjustment coefficient calculation unit 15, a gain adjustment coefficient memory unit 16, an offset coefficient calculation unit 17, an offset coefficient memory unit 18, a reference gain coefficient calculation unit 19, a reference gain coefficient memory unit 20, an image data generation unit 21, a D / A converter 22, and an input / output interface 23.

[0028] The A / D converter 9 receives data relating to the temperature of the infrared detection element 6a output from the element temperature sensor 7, A / D converts the data, and inputs the converted element temperature data to the gain adjustment coefficient calculation unit 15. Similarly, the A / D converter 11 receives data relating to the temperature of the shutter 4 output from the shutter temperature sensor 5, A / D converts the data, and inputs the converted shutter temperature data to the offset coefficient calculation unit 17. The A / D converter 10 also A / D converts the output from each infrared detection element 6a, and inputs the converted data to the offset coefficient calculation unit 17, the reference gain coefficient calculation unit 19, or the image data generation unit 21, which are selectively connected via a changeover switch 12.

[0029] In this example, the data processing unit 8 is realized by an electronic device equipped with appropriate electronic circuits, but is not limited to this configuration. The data processing unit 8 may be configured as a computer including a CPU, RAM, ROM, etc., and its functions may be realized by a computer program.

[0030] (Basic Considerations) As described above, the sensitivity of the infrared detection elements 6a varies from one element to another, and the infrared detection elements 6a have the characteristic that their sensitivity changes as they absorb infrared rays and their temperature rises. Therefore, it is necessary to correct such errors between the infrared detection elements 6a, but the image data output from the infrared camera 1 is affected by various error factors.

[0031] 1. Individual differences in element temperature sensors For example, there is a problem of variations in detected temperature (temperature detection accuracy) due to individual differences in element temperature sensors 7. The element temperature sensors 7 detect the temperature of the infrared detection elements 6a, but there is variation in temperature detection accuracy between the element temperature sensors 7 of each infrared camera 1, posing a problem that the temperature of the infrared detection elements 6a cannot be detected accurately. Therefore, it is necessary to calibrate the detected temperature detected by the element temperature sensor 7 of each infrared camera 1.

[0032] 2 is a graph showing the relationship between the temperature of the environment in which the infrared camera 1 is placed and the detected temperature (FPA) output from the element temperature sensor 7 of each infrared camera 1, and as can be seen from this graph, there is little individual difference in the slope of the detected temperature of the element temperature sensor 7 relative to the environmental temperature among the element temperature sensors 7. Therefore, by moving the graph parallel (horizontally) along the axis of environmental temperature, it is possible to absorb (i.e., calibrate) the variation in the detected temperature of the element temperature sensor 7.

[0033] In this example, for example, the average value of the output temperatures of the six element temperature sensors 7 when the ambient temperature is 30°C is calculated, and the difference of the output temperature of each element temperature sensor 7 from the average value is obtained as a correction value (sensor temperature correction value). By correcting the output temperature of each element temperature sensor 7 using this difference, it is possible to absorb the variation in the output temperature of each element temperature sensor 7 relative to the ambient temperature, as shown in Figure 3.

[0034] The sensor temperature correction value (FPA cr ) can be calculated using the following Equation 6. (Equation 6) FPA cr =(FPA RT30 )av-FPA RT30 However, (FPA RT30 ) av is the average value of the output temperatures of the six element temperature sensors 7 when the ambient temperature is 30°C, and FPA RT30 is the output temperature of each element temperature sensor 7 when the ambient temperature is 30°C. cr is acquired in advance as a unique value for each infrared camera 1 and stored in the sensor temperature correction value storage unit 14 via the input / output interface 23.

[0035] The output temperature (FPA) from the element temperature sensor 7 is calculated by the sensor temperature correction value (FPA cr ) is used to calibrate the temperature of the infrared detection element 6a by the following formula 7, and the calibration element temperature (FPA ad ) is calculated as (Equation 7) FPA ad =FPA+FPA cr

[0036] 2. Effect of environmental temperature on element temperature sensor Furthermore, the infrared detection element 6a is affected by the temperature of its surroundings (environment), causing its own temperature to fluctuate, which results in a problem of fluctuation in its sensitivity. Therefore, the detection temperature (element temperature) detected by the element temperature sensor 7 is calibrated as described above, and the calibrated element temperature (FPA ad ) the sensitivity of the infrared detection element 6a needs to be adjusted according to the above.

[0037] Figure 4 shows the calibration element temperature (FPA) for six infrared cameras. ad ) and the sensitivity ratio of the infrared detection elements 6a of each infrared camera 1. The sensitivity ratio is calculated by taking an image of a blackbody furnace at 5°C using the infrared camera 1 when the ambient temperature is 30°C and the average value (X T5 ) avSimilarly, when the ambient temperature is 30°C, the average value (X T75 ) av That is, the sensitivity ratio = (X T75 ) av / (X T5 ) av In addition, (X T5 ) av and (X T75 ) av are values ​​when the sensitivity calculated from the average value (average brightness) of the output values ​​of the infrared detection elements 6a in the central quarter region of the group of infrared detection elements 6a at an ambient temperature of 30°C is set to 1.

[0038] From the graph shown in Figure 4, the calibration element temperature (FPA ad ) and the sensitivity ratio of the infrared detection element 6a of each infrared camera 1. ad ) and the sensitivity ratio of the infrared detection element 6a of the infrared camera 1, the average values ​​of six infrared cameras 1 are shown in Figure 5. Considering that the sensitivity of the infrared detection element 6a is high at high temperatures, the reciprocal of the sensitivity ratio (called the inverse sensitivity ratio) is taken so that the value at high temperatures is small and the value at low temperatures is large, and this inverse sensitivity ratio is used as the correlation between the calibration element temperature (FPA ad ) and correlation was calculated.

[0039] Figure 6 shows the relationship between the inverse sensitivity ratio and the calibration element temperature (FPA ad ) is shown. An approximate expression showing this correlation can be found, for example, by the least squares method, and can be expressed, for example, by the following general formula, Equation 8. Note that the inverse sensitivity ratio (=(X T5 ) av / (X T75 ) av ) is used as an adjustment coefficient (gain adjustment coefficient (FT)) for adjusting the sensitivity (gain) of each infrared detection element 6a during point-to-point correction, which will be described later. (Equation 8) FT=p×(FPA ad ) 2 +q×(FPAad )+r where p, q, and r are coefficients, and in the example shown in Figure 6, p=9.610×10 -5 q=1.819×10 -2 r=1.59 is.

[0040] 3. Image data generation based on two-point correction The relationship between the luminance data X(x, y), which is the output value from each infrared detection element 6a, and the temperature T of the imaged object can be expressed by a linear equation, which is expressed by the following equation 9, where a(x, y) is the sensitivity of each infrared detection element 6a and b(x, y) is a constant. Note that, although the temperature T is more specifically the energy equivalent to the temperature T, for the sake of simplicity, hereinafter it will be referred to simply as the temperature, and unless otherwise specified, when referring to the temperature it means the energy (radiance value) equivalent to the temperature. (Equation 9) X(x,y)=a(x,y)×T+b(x,y) Therefore, the temperature T of the object to be imaged can be calculated by the following formula 10. (Equation 10) T=(X(x,y)-b(x,y)) / a(x,y) =X(x,y) / a(x,y)-b(x,y) / a(x,y) =A r (x,y)×X(x,y)+B(x,y) however, A r (x,y)=1 / a(x,y) B(x,y)=-b(x,y) / a(x,y) Hereinafter, A r (x, y) is called the reference gain coefficient, and B(x, y) is called the offset coefficient.

[0041] The energy (radiance value) corresponding to the temperature can be calculated from the following formula 11, which is Planck's radiation law that defines the correlation between temperature and energy. (Equation 11) L(λ,T)=(2C1 / λ 5 )×(1 / (exp(C2 / (λ×T))-1)×Tr where L(λ,T) is the spectral radiance [W], λ is the wavelength of light [m], T is temperature [K], Tr is the transmittance of the sensor characteristics [-], C1 and C2 are constants, C1=c 2 ×h=5.9548×10 -17 [W m 2 ], C2=c×h / k=0.014388[m·K] is. However, c is the speed of light in a vacuum (≒ 3.0 × 10 8 [m / s]), h is Planck's constant (= 6.6256 × 10 -34 [J·s]), K is the Boltzmann constant (=1.38054×10 -23 [J / s]) is.

[0042] Then, by summing the spectral radiance L(λ, T) of each wavelength of interest for the temperature T, the energy (radiance value) equivalent to the temperature can be calculated. In the following processing in this example, when it is necessary to calculate the energy equivalent to the temperature, it is calculated according to the above formula 11. Note that, in order to speed up the processing, it is preferable to calculate the relationship between the temperature and the energy in advance and provide it in the form of a data table, and even in this example, it is possible to adopt a mode in which such a data table is provided.

[0043] and the reference gain coefficient A r Using (x, y) and the offset coefficient B(x, y), image data Y(x, y) as energy (radiance value) can be calculated by the following Equation 12. (Equation 12) Y(x,y)=A r (x,y)×FT×X(x,y)+B(x,y) As mentioned above, the gain adjustment coefficient FT is a reference gain coefficient A that varies depending on the ambient temperature. r (x,y) and the reference gain coefficient A r The gain is adjusted by multiplying (x, y) by the gain adjustment coefficient FT. By performing such adjustment, it is possible to generate highly accurate image data. Note that the reference gain coefficient A r The coefficient obtained by multiplying (x, y) by the gain adjustment coefficient FT is the gain coefficient A(x, y) (=A r (x,y)×FT).

[0044] 4. Reference gain coefficient A r Calculation of (x,y) and the reference gain coefficient A r (x, y) can be calculated, for example, by the following Equation 13. (Equation 13) A r (x,y)=(T 75 -T5) / (X 75 (x,y)-X5(x,y)) Here, X5(x, y) is the output value output from each infrared detection element 6a when an infrared camera 1 placed at an environmental temperature of 30°C captures an image of a blackbody furnace at 5°C, and T5 is the energy corresponding to 5°C. Similarly, X 75 (x, y) is the output value output from each infrared detection element 6a when the infrared camera 1 placed at an environmental temperature of 30°C captures an image of a blackbody furnace at 75°C, and T 75 is the energy equivalent to 75°C. Note that the temperatures of the blackbody furnace are merely examples, and are not limited to the above-mentioned 5°C and 75°C, but can be set to other temperatures. This can be generalized by replacing 5°C with j°C and 75°C with k°C.

[0045] Then, according to the above formula 9, X5(x,y) and X 75 (x, y) are expressed by the following formulas 14 and 15, respectively. (Equation 14) X5(x,y)=a(x,y)×T5+b(x,y) (Equation 15) X 75 (x,y)=a(x,y)×T 75 +b(x,y) These differences are expressed by Equation 16. (Equation 16) X 75 (x,y)-X5(x,y)=a(x,y)×(T 75 -T5) Therefore, the reference gain coefficient A r (x, y) (= 1 / a(x, y)) can be calculated using the above-mentioned formula 13.

[0046] 5. Calculation of offset coefficient B(x,y) The offset coefficient B(x, y) can be obtained, for example, as follows: First, the shutter 4 is closed and the infrared camera 1 captures an image of the shutter 4. Then, the output value X(x, y) output from each infrared detection element 6a is calculated as follows: s Based on (x, y), an offset coefficient B(x, y) is calculated.

[0047] According to the above-mentioned formula 12, the image data Y of the shutter 4 captured by the infrared camera 1 is s (x, y) can be calculated by the following Equation 17. (Equation 17) Y s (x,y)=A r (x,y)×FT×X s (x,y)+B(x,y) Here, if the temperature of the shutter 4 is uniform, Y s (x, y) can be regarded as a constant value, and this is the energy T s Then, the following formula 18 is established. (Equation 18) T s =A r (x,y)×FT×X s (x,y)+B(x,y) Therefore, the offset coefficient B(x, y) can be calculated by the following Equation 19. (Equation 19) B(x,y)=-A r (x,y)×FT×X s (x,y)+T s The temperature of the shutter 4 can be obtained by the shutter temperature sensor 5.

[0048] (Specific configuration of infrared camera 1) Based on the above basic considerations, the infrared camera 1 of this example is configured as follows.

[0049] The p, q, r coefficient storage unit 13 is a storage unit that stores coefficients p, q, r for calculating the gain adjustment coefficient (FT) according to the above-mentioned formula 8, and stores the coefficients p, q, r input from the outside via the input / output interface 23. The coefficients p, q, r are acquired in advance by the above-mentioned method.

[0050] The sensor temperature correction value storage unit 14 stores the sensor temperature correction value (FPA) for calculating the gain adjustment coefficient (FT) according to the formulas 7 and 8. cr ) input from the outside via the input / output interface 23. cr ) is stored. In addition, the sensor temperature correction value (FPA cr ) is obtained in advance according to the above-mentioned method and Equation 6.

[0051] The gain adjustment coefficient calculation unit 15 receives the output temperature (FPA) from the element temperature sensor 7 via the A / D converter 9, and calculates the value of the received element temperature (FPA) and the sensor temperature correction value (FPA) stored in the sensor temperature correction value storage unit 14. cr ) to calculate the calibration element temperature (FPA) according to Equation 7. ad ) and calculate the calculated calibration element temperature (FPA ad ) and the values ​​of the coefficients p, q, and r stored in the p, q, and r coefficient storage unit 13, and calculates a gain adjustment coefficient (FT) according to Equation 8, and stores the calculated gain adjustment coefficient (FT) in the gain adjustment coefficient storage unit 16.

[0052] The reference gain coefficient calculation unit 19 receives the output value X(x, y) from the infrared detection element 6 a via the A / D converter 10 while being connected to the A / D converter 10 by the switch 12, and calculates the reference gain coefficient A based on the received output value X(x, y) in accordance with Equation 13 using the above-described method. r Calculate (x, y) and calculate the reference gain coefficient A r The value of (x, y) is stored in the reference gain coefficient storage unit 20.

[0053] More specifically, the reference gain coefficient calculation unit 19 calculates the output value X5(x, y) output from the infrared detection element 6a when the infrared camera 1 is placed at an environmental temperature of 30°C and an image of a blackbody furnace at 5°C is captured, and the output value X5(x, y) output from the infrared detection element 6a when the image of a blackbody furnace at 75°C is captured under the same environmental temperature. 75 (x,y) and receives the output values ​​X5(x,y) and X 75 Based on (x,y), the reference gain coefficient A r This process is performed in advance before capturing an image of the object, and the calculated reference gain coefficient A r The value of (x, y) is stored in the reference gain coefficient storage unit 20 .

[0054] The offset coefficient calculation unit 17 receives the output temperature from the shutter temperature sensor 5 via the A / D converter 9, and while connected to the A / D converter 10 by the switch 12, receives the output value X(x, y) from the infrared detection element 6 a via the A / D converter 10. Based on the received shutter temperature and output value X(x, y) and the gain adjustment coefficient (FT) stored in the gain adjustment coefficient storage unit 16, the offset coefficient calculation unit 17 calculates an offset coefficient B(x, y) in accordance with Equation 19 using the above-mentioned method, and stores the calculated value of the offset coefficient B(x, y) in the offset coefficient storage unit 18.

[0055] The image data generating unit 21 receives the output value X(x, y) from the infrared detection element 6a via the A / D converter 10 while being connected to the A / D converter 10 by the switch 12, and stores the received output value X(x, y) and the reference gain coefficient A stored in the reference gain coefficient storage unit 20. r Based on (x, y), the gain adjustment coefficient (FT) stored in the gain adjustment coefficient memory unit 16, and the offset coefficient B(x, y) stored in the offset coefficient memory unit 18, the image data Y(x, y) is calculated according to Equation 12 using the above-mentioned method.

[0056] The D / A converter 22 converts the image data Y(x, y), which is luminance data generated by the image data generating unit 21, into analog data and outputs it to the outside via the input / output interface .

[0057] According to the infrared camera 1 of this example having the above configuration, the following pre-processing 1 and pre-processing 2 are performed, and then a process of capturing an image of an object to be captured (image capturing process) is performed.

[0058] 1. Pre-processing 1 First, the coefficients p, q, r and the sensor temperature correction value (FPA) are calculated by pre-processing using an external calculation device. cr ) is acquired, and the acquired coefficients p, q, r and the sensor temperature correction value (FPA cr ) are stored in the p, q, r coefficient storage unit 13 and the sensor temperature correction value storage unit 14 via the input / output interface 23. This pre-processing 1 relates to the eigenvalues ​​of the infrared camera 1, and basically only requires one processing, but may be updated periodically or irregularly in consideration of changes over time.

[0059] 2. Pre-processing 2 Next, as pre-processing 2, the reference gain coefficient A r According to the method for calculating (x, y), the reference gain coefficient calculation unit 19 calculates the reference gain coefficient A r Calculate (x, y) and calculate the reference gain coefficient A rThe process of storing the (x, y) values ​​in the reference gain coefficient storage unit 20 is executed. This pre-processing 2 also relates to the eigenvalues ​​of the infrared camera 1, and basically only requires one processing, but taking into account changes over time, it may be updated periodically or irregularly. 3. Image Processing After the above-described pre-processing 1 and pre-processing 2 have been executed, the following imaging processes 1, 2, and 3 are executed to capture an image of the imaging target. 1) Imaging processing 1 First, as imaging process 1, with the shutter 4 closed, the gain adjustment coefficient calculation unit 15 calculates the gain adjustment coefficient FT according to the method for calculating the gain adjustment coefficient described above, and executes a process of storing the value of the calculated gain adjustment coefficient FT in the gain adjustment coefficient storage unit 16. 2) Imaging processing 2 Next, as imaging process 2, the offset coefficient B(x, y) is calculated by the offset coefficient calculation unit 17 according to the method for calculating the offset coefficient B(x, y) described above, and the value of the calculated offset coefficient B(x, y) is stored in the offset coefficient storage unit 18. 3) Image capture processing 3 After the above imaging processes 1 and 2 have been executed, the switch 12 connects the image data generation unit 21 to the A / D converter 10 with the shutter 4 open, whereby the output value X(x, y) is received from the infrared detection element 6a via the A / D converter 10 to the image data generation unit 21, and image data Y(x, y) of the object to be imaged is generated by the image data generation unit 21. The generated image data Y(x, y) is then converted into analog data by the D / A converter 22 and output to the outside via the input / output interface 23.

[0060] Thus, according to the infrared camera 1 of this example, the coefficients p, q, and r are stored in the p, q, and r coefficient storage unit 13, and the sensor temperature correction value (FPA cr ) is stored in the sensor temperature correction value storage unit 14, the gain adjustment coefficient (FT) is stored in the gain adjustment coefficient storage unit 16, and the reference gain coefficient A rBy storing (x, y) in the reference gain coefficient storage unit 20, image data of the object to be imaged can be obtained.

[0061] Therefore, it is not necessary to store a huge amount of calibration data as in the past, and the hardware configuration can be made compact, and the load for acquiring the calibration data can be reduced. In particular, the reference gain coefficient A r Although (x, y) are the number of data according to the number of infrared detection elements 6a, the coefficients p, q, r, and the sensor temperature correction value (FPA cr ) and the gain adjustment coefficient (FT) are each a single value, and the amount of data to be stored is extremely small.

[0062] In addition, in the infrared camera 1 of this example, the individual differences of the element temperature sensor 7 are corrected, and the corrected calibration element temperature (FPA ad ), the sensitivity of each infrared detection element 6a (reference gain coefficient A r Since the (x, y) is adjusted, highly accurate image data of the object to be imaged can be obtained.

[0063] Although specific embodiments of the present invention have been described above, the aspects that the present invention can adopt are not limited to these.

[0064] For example, in the example described above, the offset coefficient calculation unit 17 calculates the output value X of the infrared detection element 6a obtained by capturing an image of the shutter 4 with the shutter 4 closed, as shown in Equation 19. s However, the calculation is not limited to this, and X s (x, y) may be calculated from an approximate formula.

[0065] For example, when a black body at 40° C. is regarded as the shutter 4 by the infrared camera 1 and the black body is imaged, the output value X of the infrared detection element 6a is s (x,y) and the calibration element temperature (FPA ad) is as shown in the graph in Figure 7.

[0066] Then, when this data is approximated by a method such as the least squares method, it is expressed by the following Equation 20. (Equation 20) X s (x,y)=u×(FPA ad ) 2 +v×(FPA ad )+w

[0067] Therefore, the data processing unit 8 is further provided with a u, v, w storage unit for storing the values ​​of the coefficients u, v, w, and the offset coefficient calculation unit 17 calculates the coefficients u, v, w stored in the u, v, w storage unit and the sensor temperature correction value (FPA) stored in the sensor temperature correction value storage unit 14. cr ) and the shutter image data X according to the above-mentioned Equations 7 and 20. s (x,y) is calculated and the resulting X s Using (x, y), the offset coefficient B(x, y) can be calculated by Equation 19. The offset coefficient calculation unit 17 can adopt such a mode.

[0068] Furthermore, X s The approximation formula of (x, y) is not limited to the quadratic formula shown in Equation 20, but may be a higher-order approximation formula, or the calibration element temperature (FPA ad ) may be divided into a plurality of sections, and an approximation formula may be set for each section. Furthermore, an approximation formula such as a logarithmic approximation or an exponential approximation may be used.

[0069] Furthermore, in the above example, the shutter 4 is configured to be arranged between the lens 3 and the imaging unit 6, but this is not limited to this, and the position of the shutter 4 may be any position that can open and close the optical path of the infrared rays that are focused on the imaging unit 6, and for example, the shutter 4 may be arranged in front of the lens 3. [Explanation of symbols]

[0070] 1. Infrared camera 2. Case 3 Lenses 4 Shutter 5 Shutter temperature sensor 6. Imaging unit 6a Infrared detector 7 Element temperature sensor 8 Data Processing Unit 9, 10, 11 A / D converter 12. Changeover switch 13 a, b, c coefficient storage section 14 Sensor temperature correction value memory section 15 Gain adjustment coefficient calculation section 16 Gain adjustment coefficient memory section 17 Offset coefficient calculation section 18 Offset coefficient memory section 19 Reference gain coefficient calculation section 20 Reference gain coefficient memory section 21 Image data generation unit 22 D / A converter 23 Input / Output Interface

Claims

1. an imaging unit including a plurality of infrared detection elements arranged in x rows and y columns on a two-dimensional plane; a lens that condenses infrared light emitted from an object to be imaged onto the imaging unit; a shutter disposed between the lens and the imaging unit or in front of the lens, for opening and closing an optical path of infrared light that passes through the lens and is focused on the imaging unit; an element temperature sensor for detecting the temperature of the infrared detection element; a shutter temperature sensor that detects the temperature of the shutter; an image data generation unit that generates image data Y(x, y) of the image capture target based on an output value X(x, y) from the infrared detection element, using a gain coefficient A(x, y) and an offset coefficient B(x, y) that are coefficients for determining a correlation between the output value X(x, y) and image data Y(x, y) according to the following formula 1; A reference gain coefficient A(x, y) is a coefficient for calculating the gain coefficient A(x, y) set for the output value X(x, y), and corresponds to the sensitivity of each infrared detection element. ｒ a reference gain coefficient calculation unit that calculates (x, y); The reference gain coefficient A ｒ a gain adjustment coefficient calculation unit that calculates a gain adjustment coefficient FT, which is a coefficient set for (x, y) and is a coefficient for adjusting an error caused by the element temperature sensor; an offset coefficient calculation unit that calculates an offset coefficient B(x, y), The image data generating unit uses the reference gain coefficient A calculated by the reference gain coefficient calculating unit. ｒ (x, y) and the gain adjustment coefficient FT calculated by the gain adjustment coefficient calculation unit, according to the following formula 2. (Equation 1) Y(x,y)=A(x,y)×X(x,y)+B(x,y) (Equation 2) A(x,y)=A ｒ (x,y)×FT Here, x is an integer from 1 to n, and y is an integer from 1 to i.

2. The reference gain coefficient calculation unit calculates energy T equivalent to k [°C] when the temperature of the image capturing object is k [°C]. ｋ and the output value X from each infrared detection element at that time. ｋ (x, y), and the energy T equivalent to j [°C] when the temperature of the object to be imaged is j [°C] ｊ and the output value X from each infrared detection element at that time. ｊ (x, y) and calculate the reference gain coefficient A according to the following formula 3. ｒ 2. The infrared camera of claim 1, wherein the infrared camera is configured to calculate (x, y). (Equation 3) A ｒ (x,y)=(T ｋ -T ｊ ) / (X ｋ (x,y)-X ｊ (x,y)) However, k>j.

3. The gain adjustment coefficient calculation unit calculates an output value X from each infrared detection element when the temperature of the image capture object is k [°C]. ｋ (x, y) and the output value X from each infrared detection element when the temperature of the object being imaged is j [°C] ｊ The sensitivity ratio expressed as the ratio of (x, y) and the output value FPA from the element temperature sensor are calibrated FPA. ａｄ 2. The infrared camera according to claim 1, wherein the gain adjustment coefficient FT is calculated in accordance with the following formula 4, which is derived from the relationship: (Equation 4) FT=p×(FPA ａｄ ) ２ +q×(FPA ａｄ )+r where p, q, and r are predetermined coefficients.

4. The offset coefficient calculation unit calculates an output value X output from the infrared detection element when the shutter is closed. ｓ (x, y), and the energy corresponding to the shutter temperature, which is the output value from the shutter temperature sensor, is T ｓ 4. The infrared camera according to claim 3, wherein the offset coefficient B(x, y) is calculated in accordance with the following equation (5): (Equation 5) B(x,y)=-A ｒ (x,y)×FT×X ｓ (x,y)+T ｓ

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