Infrared camera

Abstract

The infrared imaging device includes: an infrared transmission lens (1) that focuses infrared light emitted from the subject; an infrared imaging element (2) having pixels arranged in a two-dimensional array that convert the infrared light focused by the infrared transmission lens (1) into electrical signals; a signal processing unit (3) that converts the electrical signals from the infrared imaging element (2) into digital signals; an optical characteristic correction unit (4) that corrects the optical characteristics of the output of the signal processing unit (3) based on non-imaging information preset for the infrared transmission lens (1); a reference temperature detection unit (7) that detects a reference temperature; and a temperature measurement unit (6) that calculates the absolute temperature of the subject based on the output of the optical characteristic correction unit (4) and the output of the reference temperature detection unit (7).

Description

Technical Field

[0001] This disclosure relates to infrared imaging devices. Background Technology

[0002] In typical thermal infrared solid-state imaging elements, pixels with heat-insulating structures are arranged in a two-dimensional array, and infrared images are captured by utilizing the temperature changes of the pixels according to the incident infrared radiation. In the case of uncooled thermal infrared solid-state imaging elements, in addition to calorimeters such as polycrystalline silicon, amorphous silicon, silicon carbide, and vanadium oxide, semiconductor elements such as diodes or transistors are known to be used as temperature sensors constituting the pixels. In particular, semiconductor elements such as diodes are made of solid materials, and their electrical characteristics and temperature dependence deviations are very small, which is beneficial for making the characteristics of each pixel uniform.

[0003] In a thermal infrared imaging element, an electrical signal is generated by injecting current or applying voltage to the aforementioned temperature sensor. Due to the incident infrared radiation, the temperature of the temperature sensor changes minutely, resulting in a minute change in the electrical signal. This change in the electrical signal is amplified and output to the outside via a digital signal conversion.

[0004] Generally, an infrared imaging device consists of an infrared imaging element, a mounting substrate for holding the infrared imaging element, optical system components such as a lens for focusing and imaging infrared light, and a lens barrel for holding the optical system components. Furthermore, most devices also mount components such as ASIC (Application Specific Integrated Circuit) boards and ICs (Integrated Circuits) for image processing and correction to the mounting substrate.

[0005] Optical components used for infrared focusing and imaging are generally made of materials such as germanium (Ge), chalcogenide glass, or silicon (Si). While chalcogenide glass can be sintered to form lenses, the material is very expensive. Furthermore, since Ge and Si cannot be sintered, they require machining methods such as cutting or etching. Regardless of the material, they are inferior to glass or resin lenses commonly used in visible light imaging in terms of cost and manufacturing precision.

[0006] Therefore, especially in inexpensive infrared imaging devices, spherical lenses made of Si material are generally used. However, in such cases, the imaging performance of infrared light is often not ideal. In particular, when trying to achieve both a wide viewing angle and high sensitivity simultaneously, there is a tendency for significant degradation in imaging performance. Furthermore, the difference in light intensity between the optical center and the peripheral area, i.e., the sensitivity deviation caused by shading components, also becomes significant.

[0007] Furthermore, in the temperature sensor, the actual sensitivity component is detected by adding together the temperature change caused by infrared light incident from the subject through the optical system (i.e., the temperature change due to the sensor's own self-heating caused by injecting current or applying voltage to the sensor), and the temperature change caused by the self-heating of the infrared imaging device as a whole due to the aforementioned components. Therefore, the temperature information output from the infrared light-based temperature sensor is not limited to the actual sensitivity component mentioned above.

[0008] To address the aforementioned problems, for example, as disclosed in Patent Document 1, a mechanism for performing corrections based on a pre-prepared sensitivity correction table for each pixel has been reported.

[0009] In addition, as disclosed in Patent Document 2, a mechanism for performing correction processing using a correction table pre-set by digital processing is also reported. In this case, differential processing is generally performed sequentially based on, for example, a second temperature sensor for obtaining temperature information of the infrared imaging device, and pre-acquired data of the output level stored in each infrared imaging device.

[0010] Patent Document 1: Japanese Patent Application Publication No. 2012-213130

[0011] Patent Document 2: Japanese Patent No. 5755780

[0012] However, in conventional infrared imaging devices, when using optical lenses with imperfect optical properties, there is a problem that the image blur caused by the deterioration of the lens imaging performance cannot be corrected. Summary of the Invention

[0013] The infrared imaging device disclosed herein was made to solve the above-mentioned problems, and its purpose is to provide an infrared imaging device that can properly correct image blur caused by lens imaging degradation even when using an optical lens with imperfect optical properties.

[0014] The infrared imaging apparatus disclosed herein includes: an infrared transmission lens that focuses infrared light emitted from a subject; an infrared imaging element having pixels arranged in a two-dimensional array that convert the infrared light focused by the infrared transmission lens into electrical signals; a signal processing unit that converts the electrical signals from the infrared imaging element into digital signals; an optical characteristic correction unit that corrects the optical characteristics of the output of the signal processing unit based on non-imaging information preset for the infrared transmission lens; a reference temperature detection unit that detects a reference temperature; and a temperature measurement unit that performs an absolute temperature conversion of the subject based on the output of the optical characteristic correction unit and the output of the reference temperature detection unit.

[0015] According to the infrared imaging device disclosed herein, even when using an infrared transmission lens with imperfect optical properties, by performing signal processing based on non-imaging information pre-set on the infrared transmission lens, it is possible to improve the accuracy of absolute temperature measurement and obtain an image with improved imaging properties. Attached Figure Description

[0016] Figure 1 This is a functional block diagram of the infrared imaging device involved in Embodiment 1.

[0017] Figure 2 This is a diagram showing the structure of an infrared imaging element.

[0018] Figure 3 It is a diagram representing the structure of pixels.

[0019] Figure 4 This is a graph showing the calculated imaging performance of a biconvex spherical Si lens with an incident ray angle of 10 degrees.

[0020] Figure 5 This is a graph showing the calculated imaging performance of a biconvex spherical Si lens with an incident ray angle of 55 degrees.

[0021] Figure 6 This is a graph showing the calculated imaging performance of a Si lens with a biconvex spherical shape and an aperture.

[0022] Figure 7 This is a graph showing the calculated imaging performance of a Si lens with a biconvex aspherical shape.

[0023] Figure 8 This is a diagram showing the tendency of the captured image to change due to the deterioration of the lens's imaging properties.

[0024] Figure 9 It is a graph that shows the tendency of the brightness value of the captured image to deteriorate due to the lens's imaging properties.

[0025] Figure 10 This is an image diagram of the infrared imaging device according to Embodiment 1, based on optical characteristics, for image correction.

[0026] Figure 11 This is a diagram illustrating the tendency of brightness value correction based on optical characteristics of the infrared imaging device according to Embodiment 1.

[0027] Figure 12 This is an image diagram of the infrared imaging device according to Embodiment 1, based on optical characteristics, for image correction.

[0028] Figure 13 This is a diagram illustrating the tendency of brightness value correction based on optical characteristics of the infrared imaging device according to Embodiment 1.

[0029] Figure 14 This is a graph showing the measured results of image correction based on optical characteristics of the infrared imaging device according to Embodiment 1.

[0030] Figure 15 This is a graph showing the dependence of the output temperature sensitivity of the infrared imaging device according to Embodiment 1 on the size of the subject being photographed.

[0031] Figure 16 This is a functional block diagram of the infrared imaging device involved in Embodiment 1.

[0032] Figure 17 This is a functional block diagram of the infrared imaging device involved in Embodiment 2.

[0033] Figure 18 This is a functional block diagram of the infrared imaging device involved in Embodiment 3.

[0034] Figure 19 This is a functional block diagram of the infrared imaging device involved in Embodiment 4.

[0035] Figure 20 This is a functional block diagram of the infrared imaging device involved in Embodiment 5.

[0036] Figure 21 This is a diagram illustrating an example of the hardware of the infrared imaging device described in embodiments 1 to 5. Detailed Implementation

[0037] Implementation Method 1

[0038] Figure 1 This is a functional block diagram of the infrared imaging device involved in Embodiment 1.

[0039] It includes: an infrared imaging element 2, a pixel region 12 having pixels arranged in a two-dimensional array to convert received infrared light into electrical signals; an infrared transmission lens 1, disposed between the infrared imaging element 2 and the subject, configured to focus and image the infrared light emitted from the subject; a signal processing unit 3, which receives electrical signals from the infrared imaging element 2 and performs signal amplification and conversion to digital signals; and an optical characteristic correction unit 4, which performs correction processing based on the output of the signal processing unit 3 and the non-imaging information of the infrared transmission lens 1 stored in the optical component non-imaging information storage unit 5. It is configured to receive the signal components corrected by the optical characteristic correction unit 4 (i.e., the output of the optical characteristic correction unit 4) and the signal components of the reference temperature detection unit 7 (i.e., the output of the reference temperature detection unit 7), and perform calculations on the temperature information of the subject in the temperature measurement unit 6.

[0040] exist Figure 2 The structure of the infrared imaging element 2 is shown. The pixel units 100, which receive incident infrared light and convert it into electrical signals, are preferably arranged in a two-dimensional array. A drive line selection circuit 102 for controlling the power-on timing of the pixel units 100, and a readout circuit 101 for amplifying and reading out the signal components output from the pixel units 100, are also provided. The electrical signals from the pixel units 100 arranged in the two-dimensional array are sequentially output from the readout circuit 101 via a signal output terminal 103.

[0041] exist Figure 3 The structure of the pixel section 100 is shown in the figure. Figure 3 The top image is a top view of pixel unit 100. Figure 3 The lower part of the diagram is a cross-sectional view along line AA in the top view.

[0042] The temperature detection unit 202 is disposed in the hollow heat insulation structure 205 in the form of a hollow support foot wiring 201, wherein the hollow support foot wiring 201 is electrically and thermally connected to the drive line wiring 200 connected to the drive line selection circuit 102. Here, the hollow heat insulation structure 205 can be formed by etching a part of the substrate 204, or by etching a sacrificial layer composed of an organic layer and other constituent elements.

[0043] The temperature detection unit 202 is equipped with a thermoelectric conversion mechanism 206, such as a diode or a calorimeter, to detect the composition of infrared light emitted from the subject. The electrical signal generated by the temperature detection unit 202 is transmitted to the readout circuit 101 via another hollow support foot wiring 201 and then via signal line wiring 203. Furthermore, Figure 3In the upper part of the figure, reference numeral 102a indicates the direction of current flowing from the drive line selection circuit 102, and reference numeral 101b indicates the direction of current flowing to the readout circuit 101.

[0044] Here, the electrical signal output from the temperature detection unit 202 includes components such as: substrate temperature, self-heating caused by power-on, and infrared light emitted from optical system components such as lenses and lens barrels that hold the optical system components. In other words, the electrical signal level of the temperature detection unit 202 fluctuates due to changes in ambient temperature, etc. To mitigate these fluctuations, it is generally implemented to stabilize the module temperature and the frame temperature.

[0045] Hereinafter, the necessity of setting up an optical characteristic correction unit 4 to correct the optical characteristics in the infrared imaging device 20 according to Embodiment 1 based on non-imaging information preset on the infrared transmission lens 1 will be explained.

[0046] In a commonly used biconvex Si lens, if the incident ray angle is set to 10 degrees to calculate the imaging performance, then as follows: Figure 4 As shown, the incident parallel rays are not concentrated at a single point but are dispersed. This is the reason for the deterioration of the lens's imaging performance. Even when photographing a point light source, the rays are dispersed in a normal distribution around the imaging point.

[0047] exist Figure 5 The angle of incidence is shown in the ratio of the ray angle. Figure 4 The calculation results for a larger incident ray angle of 55 degrees. Figure 4 and Figure 5 The comparison shows that the amount of incident light varies depending on the angle of incidence of the light rays incident on the optical lens. This leads to a difference in light intensity between the optical center and the periphery, i.e., a sensitivity deviation caused by the shading component. Simultaneously, it can be known that the focal length up to the imaging point is... Figure 4 and Figure 5 Different from China.

[0048] Compared to cases where the angle of incidence of light is shallow, the effective optical focal length becomes shorter when the angle of incidence is deep. This is a phenomenon known as image plane curvature, which causes differences in the degree of blurring between the center and the periphery of the resulting image.

[0049] To improve upon the aforementioned shortcomings of biconvex Si lenses, improvements have generally been made to the optical system. For example, by... Figure 6 An aperture as shown is positioned in front of the optical lens to remove unwanted light, thereby improving image quality. However, compared... Figure 4 and Figure 6 It can be seen that the sensitivity decreases because the absolute amount of incident light is reduced due to the aperture.

[0050] In addition, such as Figure 7 In that case, asphericalization of the optical lens is usually also implemented. Figure 7 Although the calculation results only simulated the aspherization of the object surface, it is clear that compared to... Figure 4 There has been some improvement. Furthermore, it can be seen that the amount of incident light has also increased.

[0051] As mentioned above, the asphericity of optical lenses brings significant advantages to the characteristics of image sensors. In the visible light image sensor region, resin or glass materials are used as optical lens materials, so the adoption of asphericity does not have a major cost impact.

[0052] On the other hand, materials that typically transmit infrared wavelengths in the 8–14 μm range are generally made of materials such as Ge, chalcogenide glass, or Si. However, chalcogenide glass, which can be made aspherical through sintering, has the disadvantage of high material cost.

[0053] As for Ge or Si, they cannot be sintered, and the machining of aspherical lenses by cutting leads to a very large increase in cost.

[0054] To address the aforementioned issues, a technique for aspherical processing using grayscale etching on Si wafers was also reported. However, aspherical lensing requires very high surface processing technology, posing challenges from the perspective of processing accuracy.

[0055] Here, in Figure 8 The diagram schematically illustrates the tendency of image changes caused by the aforementioned deterioration in lens imaging properties. Additionally, in Figure 9 schematically shown Figure 8 The output brightness between A and B.

[0056] When photographing a subject using an optical lens with ideal optical properties, such as Figure 8 As shown in the left-hand image, output brightness can be obtained based on the temperature information and surface emissivity of the subject. Furthermore, as... Figure 9 As shown by the solid line, no blurring occurs between the subject and the background, resulting in good output. That is, based on the output brightness, the temperature information of each part can be easily calculated.

[0057] On the other hand, when photographing a subject using an optical lens, such as a spherical Si lens, which does not possess ideal optical properties, such as... Figure 8 As shown in the diagram on the right, the temperature information of the subject is affected by factors such as background temperature and the size of the subject being photographed. Specifically, as... Figure 9As shown by the dotted lines, the lower the background temperature, the lower the output brightness of the subject, and the smaller the subject size, the lower the output brightness. That is, it is difficult to accurately calculate the temperature information of each part based on the output brightness, and it will cause a deterioration in visibility due to the blurring between the subject and the background.

[0058] Based on the above research, in the infrared imaging device disclosed herein, in order to appropriately correct image blur caused by lens imaging degradation even when using an infrared transmission lens 1 with suboptimal optical properties, the following measures are taken: Figure 1 The device structure shown is a basic structure. The operating principle of the infrared imaging device according to Embodiment 1 will be described in detail below.

[0059] The optical characteristic correction unit 4, which performs correction processing based on non-imaging information preset for the infrared transmission lens 1, will be described below.

[0060] Assuming an ideal optical system is used, the output values ​​of the pixels arranged in a two-dimensional array are defined as ideal output values ​​P(i,j). Next, the dispersion of a point light source incident on a point (x,y) in the pixel array to its surrounding pixels is defined as the dispersion r. (x，y) (i, j). If the measured output value Q(x, y) at point (x, y) is expressed as the ideal output value P(i, j) and the dispersion r, then... (x，y) If (i, j) is represented, then it can be expressed by the following equation (1).

[0061] [Formula 1]

[0062] Q(x, y) = ∑{P(i, j) × r (x，y) (i, j)} (1)

[0063] Dispersion r (x，y) (i, j) is the dispersion determined by the optical lens, etc. That is, the non-imaging information of the infrared transmission lens 1 stored in the non-imaging information storage unit 5 of the optical components can be derived from the measured value of the infrared transmission lens 1 measured during factory inspection, etc. If the error is within the allowable range, it can also be set to the ideal value calculated in the lens design. In addition, strictly speaking, the dispersion changes with the incident angle, but if the error is allowed, a representative value can also be set for the incident angle.

[0064] Alternatively, the dispersion r can be set by limiting the range of influence. (x，y) (i, j). That is, with point (x, y) as the center, and the dispersion within a limited range of only a few or ten pixels as the main factor, it is also possible to ignore other pixel areas.

[0065] Since the measured output value Q(x, y) of each pixel arrangement is a measured value, the dispersion r is determined by optical lenses, etc. (x，y) (i, j) are pre-calculated or determined, so the ideal output value P(i, j) can be calculated analytically using equation (1). In this case, the dispersion r is designed as described above. (x，y) Setting (i, j) can also reduce the load of analytical calculations.

[0066] Furthermore, in order to reduce the computational load of analytical calculations, the following linear operation method can also be used.

[0067] If the measured output value Q(x,y), which is assumed to be the actual output at point (x,y), is further multiplied by the dispersion r based on the infrared transmission lens 1... (x，y) The output in the case of (i, j) is defined as the assumed output value S(x, y), which can be expressed by the following equation (2).

[0068] [Equation 2]

[0069] S(x, y) = ∑{Q(i, j) × r (x，y) (i, j)} (2)

[0070] In this case, the difference between the ideal output value P(x,y) and the measured output value Q(x,y), and the ratio of the difference between the measured output value Q(x,y) and the assumed output value S(x,y), can be transformed into the following equation (3).

[0071] [Formula 3]

[0072]

[0073] Here, the denominator of equation (3) is approximately the following equation (4).

[0074] [Formula 4]

[0075]

[0076] On the other hand, the numerator of equation (3) is expressed as equation (5) below.

[0077] [Formula 5]

[0078] P(x, y) - ∑{P(i, j) × r (x，y )(i,j)} = constant (5)

[0079] That is, by approximating the left-hand side of equation (5) as a constant, as shown in equation (6) below, the ratio of the difference between the ideal output value P(x,y) and the measured output value Q(x,y), and the difference between the measured output value Q(x,y) and the assumed output value S(x,y) can be linearly approximated as the proportionality constant α.

[0080] [Formula 6]

[0081] P(x, y)-Q(x, y)={Q(x, y)--S(x, y)}×α (6)

[0082] As mentioned above, in order to obtain the measured output value Q(x,y) and the dispersion r (x，y) Directly calculating the ideal output value P(i,j) requires complex calculations, including matrix operations. However, based on the measured output value Q(x,y) and the dispersion r, (x，y) (i, j), for the assumption that it is further multiplied by the dispersion r based on the infrared transmission lens 1 (x，y) The output in case (i, j), i.e., the calculation of the assumed output value S(x, y), can be obtained through simple computation. By deriving the ideal output value P(i, j) from the measured output value Q(x, y) and the assumed output value S(x, y) using linear computation, the computational load can be significantly reduced.

[0083] The calculation of correction values ​​for optical properties based on linear approximation will be further explained.

[0084] The results obtained by simulating the correction effect of optical properties based on the relationship between the ideal output value P(x,y), the measured output value Q(x,y), and the assumed output value S(x,y) are shown below. Figure 10 as well as Figure 11 .

[0085] Figure 10 These represent simulated images with the ideal output value P(x, y) set to the value of a square subject, and the dispersion r represents the simulated image. (x，y) (i, j) are arbitrarily set to a certain in-plane value of the image, representing the ideal output value P(x, y), the measured output value Q(x, y), the assumed output value S(x, y), and the restored image P'(x, y) derived from the measured output value Q(x, y) and the assumed output value S(x, y), corresponding to... Figure 10 The first, second, third, and fourth images from the left.

[0086] Figure 11 It means Figure 10The curves representing the outputs between A and B for the ideal output value P(x,y), the measured output value Q(x,y), the assumed output value S(x,y), and the restored image P'(x,y) are respectively shown. Figure 10 The first, second, third, and fourth images from the left.

[0087] In the restored image P'(x, y), although the correction at the point where the output value switches introduces an error, the error in the output value at the center of the subject is reduced, resulting in improved temperature determination accuracy. Furthermore, for the point where the output value switches—that is, the blurred outline in the measured output value Q(x, y)—some edge enhancement effect is also achieved.

[0088] The correction calculation based on the linear approximation of optical properties disclosed herein can achieve improved temperature determination accuracy and edge enhancement even when subjects at high or low temperatures are adjacent.

[0089] Figure 12 as well as Figure 13 respectively with Figure 10 as well as Figure 11 Similarly, the graph represents the output between the simulated image and the restored image, and between A and B.

[0090] Figure 13 The curve represents the model of the subject being photographed, such as Figure 12 The output when performing correction calculations assuming adjacent high-temperature or low-temperature subjects. Figure 10 as well as Figure 11 Similarly, the improved accuracy of temperature determination and the effect of edge enhancement can be confirmed.

[0091] In fact, the dispersion r determined by the optical lens (x，y) (i, j)

[0092] (a) Derived from optical design values

[0093] (b) Limited to 21×21 pixels,

[0094] (c) Assume that it does not change relative to the angle of incidence.

[0095] (d) Correcting the output value based on linear operations.

[0096] Based on conditions (a) to (d) above, the results obtained by evaluating the effect of optical characteristic correction according to actual shooting data are shown below. Figure 14 .

[0097] exist Figure 14In the two images on the left, showing the optical properties before correction, the brightness value of the subject (the person in the image) decreases when the subject is small, and blurring occurs at the boundary between the person and the background. In contrast, in... Figure 14 In the two figures on the right, the corrected images of optical properties show small changes in output brightness values ​​and improved blurring at the boundaries.

[0098] exist Figure 15 The graph shows the output temperature sensitivity relative to the size of the subject when using the same correction method, i.e., the change in output brightness with a 1°C change in the temperature of the subject. Figure 15 In the diagram, the blackened dots represent the output sensitivity values ​​of the image before optical correction, and the blackened triangles represent the output sensitivity values ​​of the image after optical correction. It can be seen that although the output sensitivity decreases when the subject size is drastically reduced, corrections can be made to keep the output sensitivity constant in other cases.

[0099] Next, we will provide supplementary explanations regarding the calculation of the subject temperature information in the temperature measurement unit 6.

[0100] As described above, the signal components of the temperature detection unit 202 include: temperature change components caused by infrared light emitted from the subject, self-heating components caused by substrate temperature and power supply, and infrared light components emitted from optical system components such as lenses and lens barrels that hold the optical system components. In other words, in order to detect the temperature of the subject, it is necessary to calculate the temperature information of the subject.

[0101] As an example, such as Figure 16 As shown in the functional block diagram of the infrared imaging device, a mechanical shutter 8 is positioned in front of the infrared transmission lens 1. The temperature of the mechanical shutter 8 is measured by the reference temperature detection unit 7, and the output value of the mechanical shutter 8 when it is captured is pre-stored. In this structure, the temperature of the mechanical shutter 8 serves as the reference temperature. Of course, shutter mechanisms other than the mechanical shutter 8 can also achieve the same effect.

[0102] First, assume the temperature of the mechanical shutter 8 is T1, and assume the calculated output value is P1. Next, remove the mechanical shutter 8 and measure the output when the subject is photographed. Assume the calculated output value is P2. If the output temperature sensitivity after the above optical characteristic correction, i.e. the change in output brightness when the subject temperature changes by 1℃, is set as dP / dT, then the subject temperature T2 can be expressed by the following equation (7).

[0103] [Formula 7]

[0104] T2=(P2-P1)÷dP / dT+T1 (7)

[0105] Here, regarding the output temperature sensitivity dP / dT, as explained in the above description of optical characteristic correction, optical characteristic correction is performed based on the non-imaging information of the infrared transmission lens 1 stored in the non-imaging information storage unit 5 of the optical components. This results in a decrease in output sensitivity when the size of the subject is extremely reduced, but in other cases, correction can be performed in a way that keeps the output sensitivity constant. In other words, the accuracy of measuring the subject temperature T2 is improved.

[0106] On the other hand, such as Figure 1 Like the infrared imaging device shown, instead of a mechanical shutter 8, it photographs objects such as walls and floors at room temperature, and uses a reference temperature detection unit 7 to observe the room temperature, thereby achieving the same effect.

[0107] Here, the output temperature sensitivity dP / dT is explained. Although the infrared light emitted from the subject consists of various wavelengths, according to Planck's radiation law, the sum of the emitted light after integrating the entire wavelength range has the characteristic of the fourth power of temperature.

[0108] In addition, the transmittance of the optical system, exemplified by the infrared transmission lens 1, exhibits wavelength characteristics. For example, if it is a Si lens, the transmittance is low for wavelengths in the 8μm band, but high for wavelengths in the 10μm to 12μm band. Furthermore, even from the perspective of the absorptivity of the temperature detection unit 202 in the infrared imaging device 20, wavelength characteristics also exist. That is, the detectable amount of incident light is obtained by multiplying the wavelength characteristics of the incident light quantity, the wavelength characteristics of the optical system, and the wavelength characteristics of the sensor absorptivity, and then integrating the result over the entire wavelength.

[0109] The output temperature sensitivity dP / dT is a value proportional to the detectable amount of incident light and has a complex functional system relative to the temperature of the subject. When using the output temperature sensitivity dP / dT in calculations, a conversion table relative to the subject temperature can be used, or it can be a quadratic or cubic function. Furthermore, if measurement error is permissible, it can also be a linear function.

[0110] By utilizing these correction and computation circuit structures, even when photographing a subject using an optical lens with imperfect optical properties, such as a spherical Si lens, optical properties can be corrected based on the non-imaging information of the infrared transmission lens 1 stored in the non-imaging information storage unit 5 of the optical components. This ensures that the temperature information of the subject is unaffected by background temperature, subject size, etc., thereby improving the accuracy of subject temperature calculation. Simultaneously, it eliminates the deterioration in visibility caused by subject-background blurring, resulting in an image with emphasized contours.

[0111] Implementation Method 2

[0112] Figure 17 This is a functional block diagram of the infrared imaging device involved in Embodiment 2.

[0113] In addition to the components of the infrared imaging device described in Embodiment 1, a temperature detection target derivation unit 23 is also provided between the signal processing unit 3 and the optical characteristic correction unit 4. The temperature detection target derivation unit 23 defines the temperature measurement area within the frame of the infrared imaging element 2, and optical characteristic correction is performed only on the defined area. This significantly reduces the computational load required for optical characteristic correction. Furthermore, the accuracy of temperature calculation for the designated temperature measurement area is improved.

[0114] For example, the temperature measurement point exported by the temperature detection object export unit 23 can be set to only the point with the maximum output brightness within the screen, or multiple points can be set through image analysis. Alternatively, the same point can always be specified.

[0115] By using the infrared imaging device according to Embodiment 2, even when the subject is photographed using an optical lens that does not have ideal optical characteristics, such as a spherical Si lens, the optical characteristics are corrected based on the non-imaging information of the infrared transmission lens 1 stored in the non-imaging information storage unit 5 of the optical components. As a result, the temperature information of the subject is not affected by the background temperature, the size of the subject being photographed, etc., and the conversion accuracy of the subject temperature can be improved, which is the effect of Embodiment 1. At the same time, a new effect of greatly reducing the computational load is obtained.

[0116] Implementation Method 3

[0117] Figure 18 This is a functional block diagram of the infrared imaging device involved in Embodiment 3.

[0118] In addition to the components of the infrared imaging device described in Embodiment 1, a level stabilization representative point extraction unit 21 and a brightness value adjustment unit 22 that receives the output of the level stabilization representative point extraction unit 21 are also provided at the rear of the temperature measuring unit 6. The portion of the output measured by the temperature measuring unit 6 in which the photographed object moves, i.e., the portion in which the output value does not change significantly, is at the room temperature level and is presumed to mean that the actual temperature has not changed significantly.

[0119] On the other hand, the signal components of the temperature detection unit 202 include: components generated by the substrate temperature and self-heating caused by power-on; and components of infrared light emitted from optical system components such as lenses and lens barrels that hold the optical system components. That is, due to changes in wind, direct sunlight, other external interference, and ambient temperature, the signal level fluctuates, resulting in unstable output values.

[0120] The level stabilization representative point extraction unit 21 determines the portion of the output value that has not changed significantly, and outputs the coordinate data of the portion of the output value that has not changed significantly to the temperature measurement unit 6. In the temperature measurement unit 6, by implementing screen brightness correction or temperature determination correction to set the output of the specified coordinate data to a constant, temperature determination and image generation can be performed without being affected by external interference.

[0121] In the level-stabilized representative point extraction unit 21, for example, temperature determination can be performed on multiple fixed points continuously, and pixels with small time deviations in their output values ​​can be designated as representative pixels. Alternatively, image analysis can be performed on the entire screen to improve accuracy. As an example, pixels whose output value changes less than a predetermined threshold can be extracted as designated pixels, i.e., representative points. The brightness value adjustment unit 22 receives the output of the level-stabilized representative point extraction unit 21 and adjusts the brightness of the designated pixels, i.e., representative points.

[0122] By using the infrared imaging device according to Embodiment 3, even when the subject is photographed using an optical lens that does not have ideal optical characteristics, such as a spherical Si lens, the temperature information of the subject is not affected by the background temperature, the size of the subject being photographed, etc., by correcting the optical characteristics based on the non-imaging information of the infrared transmission lens 1 stored in the non-imaging information storage unit 5 of the optical components, thus improving the accuracy of the temperature conversion of the subject.

[0123] Furthermore, it achieves the effect of Implementation Method 1, which eliminates the deterioration of visibility caused by blurring between the subject and the background and obtains an image that emphasizes the outline, while also achieving a new effect of being able to make a judgment that reduces the influence of external interference.

[0124] Implementation Method 4

[0125] Figure 19 This is a functional block diagram of the infrared imaging device involved in Embodiment 4.

[0126] In addition to the components of the infrared imaging device described in Embodiment 1, a temperature influence calculation unit 9 is disposed between the signal processing unit 3 and the optical characteristic correction unit 4. The temperature influence calculation unit 9 is connected to a reference temperature information from the reference temperature detection unit 7 and an output influence calculation coefficient storage unit 10. The output influence calculation coefficient storage unit 10 stores the output displacement tendency relative to a pre-stored reference temperature.

[0127] In the temperature influence calculation unit 9, the output value is corrected by combining the reference temperature information from the reference temperature detection unit 7 and the output displacement tendency relative to the reference temperature. As a result, the signal level fluctuations caused by wind, direct sunlight, other external interference, and changes in ambient temperature, as described in the infrared imaging device 20 of Embodiment 3, can be corrected, and the output value can be stabilized.

[0128] By using the infrared imaging device according to Embodiment 4, even when the subject is photographed using an optical lens that does not have ideal optical characteristics, such as a spherical Si lens, the temperature information of the subject is not affected by the background temperature, the size of the subject being photographed, etc., by correcting the optical characteristics based on the non-imaging information of the infrared transmission lens 1 stored in the non-imaging information storage unit 5 of the optical components, and thus the temperature conversion accuracy of the subject is improved.

[0129] Furthermore, it achieves the effect of Embodiment 1, which eliminates the deterioration in visibility caused by blurring between the subject and the background, resulting in an image with emphasized contours. Simultaneously, similar to Embodiment 3, it provides a new effect: enabling the determination of reduced external interference. Additionally, it reduces the frequency of shutter correction, thereby eliminating the need for the shutter mechanism itself.

[0130] Implementation Method 5

[0131] Figure 20 This is a functional block diagram of the infrared imaging device involved in Embodiment 5.

[0132] In the components of the infrared imaging device described in Embodiment 1, the reference temperature detected in the reference temperature detection unit 7 can also be output as a temperature sensor disposed within the infrared imaging element 2. As described above, the signal components of the temperature detection unit 202 include: the substrate temperature, self-heating components caused by power-on, and components of infrared light emitted from optical system components such as lenses and the lens barrel holding the optical system components. By accurately measuring the temperature of the infrared imaging element 2, the accuracy of temperature determination can be improved.

[0133] By utilizing the infrared imaging device according to Embodiment 5, even when photographing a subject using an optical lens with non-ideal optical characteristics, such as a spherical Si lens, optical characteristics are corrected based on the non-imaging information of the infrared transmission lens 1 stored in the non-imaging information storage unit 5 of the optical components. This ensures that the temperature information of the subject is unaffected by background temperature, subject size, etc., thus improving the accuracy of subject temperature calculation. Furthermore, it achieves the effect of Embodiment 1, which eliminates the deterioration in visibility caused by subject-background blur and obtains an image with emphasized contours, while further improving the accuracy of temperature determination.

[0134] Furthermore, the structure of the infrared imaging device described in Embodiments 1 to 5 is explained using functional block diagrams. Figure 21 The diagram shows an example of the hardware structure for storing the aforementioned functional modules. Hardware 300 comprises a processor 301 and a storage device 302. Although the storage device is not shown, it includes volatile storage devices such as random access memory and non-volatile auxiliary storage devices such as flash memory. Alternatively, a hard disk drive may be used as an auxiliary storage device instead of flash memory. The processor 301 executes a program input from the storage device 302. In this case, the program is input to the processor 301 from the auxiliary storage device via the volatile storage device. Furthermore, the processor 301 can output data such as calculation results to the volatile storage device of the storage device 302, or it can save data to the auxiliary storage device via the volatile storage device.

[0135] This disclosure describes various exemplary embodiments and examples, but the various features, forms and functions described in one or more embodiments are not limited to the application of a specific embodiment, and can also be applied to the embodiment alone or in various combinations.

[0136] Therefore, numerous variations not illustrated can be conceived within the scope of the technology disclosed in this application. These include variations, additions, or omissions of at least one constituent element, as well as extraction of at least one constituent element and combination with constituent elements of other embodiments.

[0137] Explanation of reference numerals in the attached figures

[0138] 1...Infrared transmission lens; 2...Infrared imaging element; 3...Signal processing unit; 4...Optical characteristic correction unit; 5...Non-imaging information storage unit for optical components; 6...Temperature measuring unit; 7...Reference temperature detection unit; 8...Mechanical shutter; 9...Temperature influence calculation unit; 10...Output influence calculation coefficient storage unit; 12...Pixel area; 21...Level stabilization representative point extraction unit; 22...Brightness value adjustment unit; 23...Temperature detection object export unit; 100...Pixel unit; 101...Readout circuit; 102...Drive line selection circuit; 103...Signal output terminal; 200...Drive line wiring; 201...Hollow support foot wiring; 202...Temperature detection unit; 203...Signal line wiring; 204...Substrate; 205...Hollow heat insulation structure; 206...Thermoelectric conversion mechanism; 300...Hardware; 301...Processor; 302...Storage device.

Claims

1. An infrared camera characterized by comprising: an infrared transmitting lens that condenses infrared light radiated from an object; an infrared camera element having pixels that convert infrared light condensed by the infrared transmitting lens into electric signals arranged in a two-dimensional array; a signal processing section that converts the electric signals from the infrared camera element into digital signals; an optical characteristic correction section that corrects the output of the signal processing section in terms of optical characteristics based on non-imaging information set in advance for the infrared transmitting lens; a reference temperature detection section that detects a reference temperature; and a temperature measurement section that performs absolute temperature conversion of the object based on the output of the optical characteristic correction section and the output of the reference temperature detection section, wherein the optical characteristic correction section corrects the output in terms of optical characteristics based on a value obtained by multiplying a proportional constant by a difference between the output of the signal processing section and an output obtained by multiplying the non-imaging information, i.e., dispersion, of the infrared transmitting lens by the output of the signal processing section.

2. The infrared camera according to claim 1, characterized in that a shutter mechanism is arranged in front of the infrared transmitting lens, the temperature of the shutter mechanism is measured by the reference temperature detection section, and the temperature is used in the operation of the temperature measurement section.

3. The infrared camera according to claim 1 or 2, characterized by further comprising a temperature detection target derivation section that defines a temperature measurement site within the picture of the infrared camera element, wherein the optical characteristic correction section uses a representative point defined by the temperature detection target derivation section as an object of operation.

4. The infrared camera according to claim 1 or 2, characterized in that the infrared camera further comprises: a level-stabilized representative point extraction section that extracts pixels whose output values vary by less than a threshold value; and a luminance value adjustment section that adjusts the luminance values of the pixels based on the output of the level-stabilized representative point extraction section, wherein the optical characteristic correction section corrects the output of the signal processing section in terms of output values including the output of the level-stabilized representative point extraction section and the output of the luminance value adjustment section.

5. The infrared camera according to claim 1 or 2, characterized in that the infrared camera further comprises: an output displacement tendency storage section that stores an output displacement tendency with respect to the reference temperature; and a temperature influence operation section that operates correction of the output of the reference temperature detection section based on the output displacement tendency.

6. The infrared camera according to claim 1 or 2, characterized in that the reference temperature is the temperature of the infrared camera element measured by the reference temperature detection section. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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