JP2021189171A - Infrared imaging device - Google Patents

Abstract

To provide an infrared imaging device for properly correcting an image blur due to a deteriorated image forming characteristic of a lens, even when using an optical lens with a non-ideal optical characteristic.SOLUTION: An infrared imaging device comprises: an infrared transmitting lens 1 that collects infrared light emitted from a subject; an infrared imaging element 2 that has a screen on which pixels for converting, into an electric signal, the infrared light collected by the infrared transmitting lens 1 are arranged in a two-dimensional array; a signal processor 3 that converts the electric signal from the infrared imaging element 2 into a digital signal; an optical characteristic correction unit 4 that corrects an optical characteristic on the basis of an output of the signal processor 3, and an output obtained by multiplying the output of the signal processor 3 by the dispersion degree of the infrared transmitting lens 1; a reference temperature detection unit 7 that detects the reference temperature; and a temperature measurement unit 6 that performs absolute temperature conversion on the subject on the basis of an output of the optical characteristic correction unit 4 and an output of the reference temperature detection unit 7.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an infrared image pickup apparatus.

In a general thermal infrared solid-state image sensor, pixels having a heat insulating structure are arranged in a two-dimensional array, and an infrared image is imaged by utilizing the fact that the temperature of the pixels changes due to the incident infrared rays. In the case of a non-cooled thermal infrared solid-state image sensor, the temperature sensor that constitutes the pixel uses a borometer such as polysilicon, amorphous silicon, silicon carbide, or vanadium oxide, as well as a semiconductor element such as a diode or transistor. It has been known. In particular, a semiconductor element such as a diode is made of a solid or the like, and the variation in electrical characteristics and temperature dependence is very small, which is advantageous in making the characteristics of each pixel uniform.

In the thermal infrared image pickup device, an electric signal is generated by injecting a current or applying a voltage to the temperature sensor. The temperature of the temperature sensor fluctuates minutely due to the incident of infrared rays, and the electric signal fluctuates minutely. The fluctuation of this electric signal is amplified, converted into a digital signal, and then output to the outside.

Generally, an infrared image pickup device holds the infrared image pickup element, a mounting substrate portion that holds the infrared image pickup element, an optical system member such as a lens for collecting and forming an image of infrared light, and an optical system member. It is composed of a lens barrel for this purpose. Further, in many cases, parts composed of an ASIC (Application Specific Integrated Circuit) substrate, an IC (Integrated Circuit), and the like for performing image processing, correction processing, and the like are simultaneously mounted on the mounting substrate portion.

The optical member for forming a condensed image of infrared rays is generally made of germanium (Ge), chalcogenide glass, silicon (Si), or the like. Although chalcogenide glass can form a lens by sintering, the material is very expensive. Further, since Ge and Si cannot be sintered and formed, they need to be formed by shaving or etching. Both materials are inferior in cost or processing accuracy to glass lenses or resin lenses generally used for visible light.

For this reason, it is common to use a spherical lens made of Si material, especially in an inexpensive infrared image pickup device, but in this case, it is often not in an ideal state in terms of the image quality of infrared light. .. In particular, when trying to achieve a wide viewing angle and high sensitivity at the same time, the deterioration of image quality tends to be remarkable. Further, the difference in the amount of light between the optical center portion and the outer peripheral portion, that is, the sensitivity variation due to the shading component becomes remarkable at the same time.

Further, in the temperature sensor, the temperature change of the temperature sensor due to the infrared light incident from the subject through the optical system, that is, the actual sensitivity component and the self-heating temperature of the temperature sensor itself by injecting a current or applying a voltage to the temperature sensor. The change and the temperature change due to the self-heating of the entire infrared image pickup device generated by the above-mentioned parts are added and detected. Therefore, the temperature information output from the temperature sensor by infrared light is not limited to the above-mentioned actual sensitivity component.

In order to solve the above-mentioned problem, for example, as disclosed in Patent Document 1, a mechanism for performing correction after preparing a sensitivity correction table for each pixel in advance has been reported.

Further, as disclosed in Patent Document 2, a mechanism for performing correction processing using a correction table preset by digital processing has also been reported, in which case, for example, in order to acquire temperature information of an infrared image pickup apparatus. It is also common to perform sequential difference processing based on the second temperature sensor of the above and the preliminary data of the output level acquired in advance and stored for each infrared imaging device.

Japanese Unexamined Patent Publication No. 2012-213130 Japanese Patent No. 5755780

However, in the conventional infrared image pickup apparatus, when an optical lens having non-ideal optical characteristics is used, there is a problem that image blurring due to deterioration of lens imaging property cannot be corrected.

The infrared image pickup apparatus according to the present disclosure has been made to solve such a problem, and is an infrared image pickup apparatus that appropriately corrects image blurring due to deterioration of lens image quality even when an optical lens having non-ideal optical characteristics is used. The purpose is to provide.

In the infrared image pickup apparatus according to the present disclosure, an infrared transmission lens that collects infrared light emitted from a subject and pixels that convert infrared light collected by the infrared transmission lens into an electric signal are arranged in a two-dimensional array. An infrared image pickup element having a screen, a signal processing unit that converts the electric signal from the infrared image pickup element into a digital signal, an output of the signal processing unit, and an infrared transmissive lens at the output of the signal processing unit. Based on the optical characteristic correction unit that corrects the optical characteristics based on the output multiplied by the degree of dispersion, the reference temperature detection unit that detects the reference temperature, the output of the optical characteristic correction unit, and the output of the reference temperature detection unit. A temperature measuring unit for converting the absolute temperature of the subject is provided.

According to the infrared image pickup apparatus according to the present disclosure, even when an infrared transmissive lens whose optical characteristics are not ideal is used, signal processing can be performed based on the information on the degree of dispersion of the infrared transmissive lens, thereby improving the absolute temperature measurement accuracy and improving the absolute temperature measurement accuracy. It is possible to acquire an image with improved image quality.

It is a functional block diagram of the infrared image pickup apparatus according to Embodiment 1. FIG. It is a figure which shows the structure of an infrared image pickup element. It is a figure which shows the composition of a pixel. It is a figure which shows the calculation result of the Si lens imaging property of the biconvex spherical shape when the incident ray angle is 10 degrees. It is a figure which shows the calculation result of the Si lens imaging property of the biconvex spherical shape when the incident ray angle is 55 degrees. It is a figure which shows the calculation result of the Si lens imaging property of the biconvex spherical shape which has a diaphragm. It is a figure which shows the calculation result of the Si lens imaging property of a biconvex aspherical shape. It is a figure which shows the tendency of the change of the captured image due to the deterioration of the lens imaging property. It is a figure which shows the tendency of the luminance value of the captured image due to the deterioration of the lens imaging property. FIG. 5 is an image diagram of image correction by correction of optical characteristics in the infrared image pickup apparatus according to the first embodiment. It is a figure which shows the tendency of the luminance value correction by the correction of the optical characteristic in the infrared image pickup apparatus according to Embodiment 1. FIG. FIG. 5 is an image diagram of image correction by correction of optical characteristics in the infrared image pickup apparatus according to the first embodiment. It is a figure which shows the tendency of the luminance value correction by the correction of the optical characteristic in the infrared image pickup apparatus according to Embodiment 1. FIG. It is a figure which shows the actual measurement result of the image correction by the correction of the optical characteristic in the infrared image pickup apparatus according to Embodiment 1. FIG. It is a figure which shows the subject size dependence of the optical characteristic sensitivity in the infrared image pickup apparatus according to Embodiment 1. FIG. It is a functional block diagram of the infrared image pickup apparatus according to Embodiment 1. FIG. It is a functional block diagram of the infrared image pickup apparatus according to Embodiment 2. FIG. It is a functional block diagram of the infrared image pickup apparatus according to Embodiment 3. FIG. It is a functional block diagram of the infrared image pickup apparatus according to Embodiment 4. FIG. It is a functional block diagram of the infrared image pickup apparatus according to Embodiment 5. It is a figure which shows an example of the hardware of the infrared image pickup apparatus according to Embodiments 1-5.

Embodiment 1.
FIG. 1 is a functional block diagram of the infrared image pickup apparatus according to the first embodiment.
An infrared image pickup element 2 having a pixel region 12 in which pixels for converting received infrared light into an electric signal are arranged in a two-dimensional array, and an infrared light emitted from the subject arranged between the infrared image pickup element 2 and the subject. An infrared transmissive lens 1 arranged so as to collect light and form an image, a signal processing unit 3 that inputs an electric signal from an infrared image pickup element 2 and performs signal amplification and conversion to a digital signal, and a signal processing unit. It has an optical characteristic correction unit 4 that performs correction processing based on the output of 3 and the non-imaging information of the infrared transmissive lens 1 accumulated in the optical member non-imaging information storage unit 5, and has an optical characteristic correction unit 4. The temperature measuring unit 6 receives the signal component corrected by the above, that is, the output of the optical characteristic correction unit 4, and the signal component of the reference temperature detecting unit 7 that acquires the reference temperature information, that is, the output of the reference temperature detecting unit 7. The configuration is such that the subject temperature information is calculated in.

FIG. 2 shows the configuration of the infrared image pickup element 2. The pixel units 100 that receive the incident infrared light and convert it into an electric signal are preferably arranged in a two-dimensional array, and the signals output from the drive line selection circuit 102 and the pixel unit 100 that control the energization timing of the pixel unit 100. A read-out circuit 101 that amplifies and reads out the components is arranged. The electric signals of the pixel units 100 arranged in a two-dimensional array are sequentially output from the readout circuit 101 via the signal output terminal 103.

The configuration of the pixel unit 100 is shown in FIG. The upper view of FIG. 3 is a top view of the pixel portion 100, and the lower view of FIG. 3 is a cross-sectional view taken along the line AA in the top view.
The temperature detection unit 202 is arranged in the hollow heat insulating structure 205 while being held by the hollow support leg wiring 201 electrically and thermally connected to the drive line wiring 200 connected to the drive line selection circuit 102. ing. Here, the hollow heat insulating structure 205 may be formed by etching a part of the substrate 204, or the hollow heat insulating structure 205 may be formed by etching the sacrificial layer composed of the organic layer and other components. You may.

The temperature detection unit 202 is provided with a thermoelectric conversion mechanism 206 composed of a diode, a bolometer, or the like in order to detect a component of infrared light emitted from the subject. The electric signal generated by the temperature detection unit 202 is transmitted to the read circuit 101 via the signal line wiring 203 via the other hollow support leg wiring 201. Reference numeral 102a in the upper part of FIG. 3 indicates the direction of the current flowing in from the drive line selection circuit 102, and reference numeral 101b indicates the direction of the current flowing in the readout circuit 101.

Here, the electric signal output from the temperature detection unit 202 has as its components the substrate temperature, a self-heating component due to energization, an optical system member such as a lens, and infrared rays emitted from a lens barrel that holds the optical system member. Contains light components. That is, the electric signal level of the temperature detection unit 202 fluctuates due to fluctuations in the environmental temperature and the like. In order to improve the fluctuation of the electric signal level, it is generally practiced to stabilize the module temperature and the housing temperature.

Hereinafter, in the infrared image pickup apparatus 20 according to the first embodiment, it is necessary to provide an optical characteristic correction unit 4 for the infrared transmissive lens 1 based on preset non-imaging information to correct the optical characteristics. do.

In a commonly used biconvex Si lens, when the imaging property is calculated with the incident ray angle set to 10 degrees, the incident parallel rays are not concentrated at one point but dispersed, as shown in FIG. I understand. This is the reason why the lens imaging property is deteriorated. Even if a point light source is imaged, it will be dispersed and incident as if it were a normal distribution centered on the image point.

FIG. 5 shows the calculation result of a ray having an incident ray angle larger than that of FIG. 4 and an incident ray angle of 55 degrees. It can be understood from the comparison between FIGS. 4 and 5 that the amount of incident light rays differs depending on the angle of the light rays incident on the optical lens. This leads to the difference in the amount of light between the optical center and the outer periphery, that is, the sensitivity variation due to the shading component. At the same time, it can be seen that the focal lengths to the image formation points are different in FIGS. 4 and 5.

The effective optical focal length is shorter when the angle of incidence of the light beam is deeper than when the angle of incidence of the light beam is shallow. This is a phenomenon of so-called curvature of field, which leads to a difference in the degree of blurring of the image between the central portion and the outer peripheral portion of the obtained image.

In order to improve the above-mentioned defects of the biconvex Si lens, improvements to the optical system have generally been made so far. For example, by arranging a diaphragm as shown in FIG. 6 in front of the optical lens to remove unnecessary light, it is possible to improve the appearance of the image. However, as can be seen by comparing FIGS. 4 and 6, the amount of incident absolute light is reduced by the aperture, so that the sensitivity is reduced.

It is also common to make the optical lens aspherical as shown in FIG. FIG. 7 is a calculation result simulating the asphericalization of only the objective surface, but it can be seen that it is improved as compared with that of FIG. Furthermore, it can be seen that the amount of incident light is also improved.

As described above, it can be seen that the asphericalization of the optical lens brings a great merit to the characteristics of the image sensor. In the visible light image sensor region, since a resin material or a glass material is used as the optical lens material, there is no significant cost impact in dealing with asphericalization.

On the other hand, Ge, chalcogenide glass, Si, or the like is generally used as a material that transmits a wavelength in the infrared region typified by 8 to 14 μm, but it can be made aspherical by sintering. Calcogenide glass has the disadvantage in terms of cost that the material itself is expensive.

Sintering is not possible for Ge or Si, and aspherical lens processing by machining leads to a very large cost increase.

In order to solve this problem, a technique for performing aspherical processing by using grayscale etching on a Si wafer has been reported, but a very advanced surface processing technology is required to make an aspherical lens. There remains a problem from the viewpoint of processing accuracy.

Here, FIG. 8 schematically shows the tendency of the captured image change due to the deterioration of the lens imaging property described above. Further, the output luminance between AB in FIG. 8 is schematically shown in FIG.

When the subject is imaged with an optical lens having ideal optical characteristics, the output brightness based on the temperature information of the subject and the surface emissivity can be obtained as shown in the figure on the left side of FIG. Further, as shown by the solid line in FIG. 9, blurring between the subject and the background does not occur, and good output can be obtained. That is, it is easy to obtain the temperature information of each part by calculation based on the output luminance.

On the other hand, when the subject is imaged with an optical lens that does not have ideal optical characteristics, such as a spherical Si lens, the temperature information of the subject is the background temperature, as shown in the figure on the right side of FIG. It is affected by the size of the subject image. Specifically, as shown by the broken line in FIG. 9, the lower the background temperature, the lower the subject output brightness, and the smaller the subject size, the lower the subject output brightness. That is, it is difficult to accurately calculate the temperature information of each part based on the output luminance, and the visibility is deteriorated due to the blurring between the subject and the background.

Based on the above studies, in the infrared image pickup apparatus according to the present disclosure, in order to appropriately correct image blurring due to deterioration of lens image quality even when an infrared transmission lens 1 having non-ideal optical characteristics is used, FIG. The basic configuration is the device configuration shown in. The operating principle of the infrared image pickup apparatus according to the first embodiment will be described in detail below.

The optical characteristic correction unit 4 that performs correction processing based on preset non-imaging information for the infrared transmissive lens 1 will be described below.
Assuming that an ideal optical system is used, the output value of each pixel array arranged in a two-dimensional array is defined as the ideal output value P (i, j). Next, the degree of dispersion to peripheral pixels when a point light source is incident on a certain point (x, y) in the pixel array is defined as the degree of dispersion r _{(x, y)} (i, j). The actually measured output value Q (x, y) actually output at the point (x, y) is expressed by the ideal output value P (i, j) and the degree of dispersion r _{(x, y)} (i, j). It can be expressed by the following equation (1).

The degree of dispersion r _{(x, y)} (i, j) is the degree of dispersion determined by an optical lens or the like, that is, the non-imaging information of the infrared transmissive lens 1 accumulated in the optical member non-imaging information storage unit 5. Therefore, it may be derived from the actually measured value obtained by measuring the infrared transmissive lens 1 in the shipping inspection or the like, or if the error is within an allowable range, it may be an ideal value calculated by the lens design. Strictly speaking, the degree of dispersion changes with respect to the incident angle, but if an error is allowed, a representative value may be provided for the incident angle.

Further, the degree of dispersion r _{(x, y)} (i, j) may be set by limiting the range of influence. That is, if the main factor is the dispersion of only a limited range of several pixels or about ten pixels around the point (x, y), the other pixel areas may be ignored. ..

Since the actually measured output value Q (x, y) of each pixel array is an actually measured value, and the dispersity r _{(x, y)} (i, j) determined by an optical lens or the like is calculated or measured in advance, ( The ideal output value P (i, j) can be calculated by the analysis calculation using the equation 1). In this case, it is possible to reduce the load of analysis calculation by devising the setting of the _{degree of dispersion r (x, y) (i, j) as described above.}

Further, in order to reduce the analysis calculation load, the following linear calculation means may be adopted.
Assuming that the measured output value Q (x, y) actually output at the point (x, y _{) is further multiplied by the dispersion r (x, y)} (i, j) by the infrared transmissive lens 1. If the output of is defined as the assumed output value S (x, y), the assumed output value S (x, y) can be expressed by the following equation (2).

In this case, 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). The ratio can be transformed into the following equation (3).

Here, the denominator term of Eq. (3) is approximated as in Eq. (4) below.

On the other hand, the numerator term of the formula (3) is expressed as the following formula (5).

That is, by approximating the term on the left side of Eq. (5) as a constant, the ideal output value P (x, y) and the actually measured output value Q (x, y) are as shown in Eq. (6) below. It is possible to linearly approximate the ratio of the difference value to the measured output value Q (x, y) and the assumed output value S (x, y) as the proportionality constant α.

As described above, in order to calculate the ideal output value P (i, j) directly from the measured output value Q (x, y) and the dispersion degree r _{(x, y) (i, j), matrix calculation was included.} Although complicated calculations are required, from the measured output values Q (x, y) and the dispersion r _{(x, y)} (i, j), the dispersion r _{(x, y)} (i, by the infrared transmissive lens 1) The assumed output value S (x, y), which is the output when it is assumed that j) is further multiplied, can be calculated by simple calculation. By deriving the ideal output value P (i, j) by linear calculation from the measured output value Q (x, y) and the assumed output value S (x, y), the calculation load can be greatly reduced.

Further explanation will be given regarding the calculation of the correction value of the optical characteristics by linear approximation.
FIG. 10 shows the result of simulating the effect of correcting the optical characteristics from the relationship between the ideal output value P (x, y), the measured output value Q (x, y), and the hypothetical output value S (x, y). And shown in FIG.

In FIG. 10, the ideal output value P (x, y) is a simulated image when a square-shaped subject is imaged, and the dispersion degree r _{(x, y)} (i, j) is arbitrarily set as a constant in-plane value of the screen. When set, the ideal output value P (x, y), the measured output value Q (x, y), the assumed output value S (x, y), the measured output value Q (x, y), and the assumed output value S ( The restored images P'(x, y) derived from x, y) are represented, respectively, and correspond to the first, second, third, and fourth figures from the left in FIG.

11 shows the ideal output value P (x, y), the measured output value Q (x, y), the hypothetical output value S (x, y), and the restored image P'(x, y) in FIG. 10, respectively. It is a graph showing the output between A and B, and corresponds to the first, second, third, and fourth figures from the left in FIG. 10, respectively.

In the restored image P'(x, y), although an error occurs in the correction at the point where the output value switches, the error in the output value in the central part of the subject becomes small, and the effect of improving the temperature determination accuracy can be obtained. .. In addition, a slight edge enhancement effect is obtained even at the point where the output value is switched, that is, the contour portion that has been blurred at the actually measured output value Q (x, y).

The correction calculation of the optical characteristics by the linear approximation of the present disclosure can similarly improve the temperature determination accuracy and obtain the effect of edge enhancement even when a high temperature or low temperature subject is adjacent to each other.

12 and 13, as in the case of FIGS. 10 and 11, are graphs showing the simulated image, the restored image, and the output between AB, respectively.

The graph of FIG. 13 shows the output when the correction calculation is performed assuming the case where high temperature or low temperature subjects are adjacent to each other as the subject model as shown in FIG. As in the case of FIGS. 10 and 11, it can be confirmed that the temperature determination accuracy is improved and the edge enhancement effect is obtained.

_{Actually, the dispersity r (x, y)} (i, j) determined by the optical lens is
(A) Derived from the optical design value (b) Limited to 21 × 21 pixels (c) It shall not change with respect to the incident angle (d) Correction of the output value by linear calculation Above, (a) to (d) As a condition, FIG. 14 shows the result of evaluating the effect of the correction of the optical characteristics from the actual imaging data.

In the image before correction of the optical characteristics shown in the two figures on the left side of FIG. 14, the luminance value of the subject, that is, the person in the figure is changed to be lower when the subject is small, and at the same time, the person and the background are changed. Blurring occurs at the boundary. On the other hand, in the image after correction of the optical characteristics shown in FIG. 2 on the right side of FIG. 14, the change in the output luminance value is small and the blurring of the boundary portion is also improved.

The graph of FIG. 15 shows the result of measuring the output temperature sensitivity with respect to the subject size when the same correction method is used, that is, the amount of change in the output luminance when the subject temperature changes by 1 ° C. In FIG. 15, the circle points filled with black represent the output sensitivity value from the image before the correction of the optical characteristics, and the triangular points filled with black represent the output sensitivity value from the image after the correction of the optical characteristics. When the subject size is extremely reduced, the output sensitivity value decreases, but in other cases, it can be seen that the output sensitivity value can be corrected to be constant.

Next, a supplementary explanation will be added regarding the calculation of the subject temperature information in the temperature measuring unit 6.
As described above, the signal component of the temperature detection unit 202 includes a temperature change component due to infrared light emitted from the subject, a substrate temperature, a self-heating component due to energization, an optical system member such as a lens, and a lens barrel that holds the optical system member. It contains components of infrared light emitted from such sources. That is, in order to detect the temperature of the subject, it is necessary to calculate the subject temperature information.

As an example, as shown in the functional block diagram of the infrared image pickup device shown in FIG. 16, a mechanical shutter 8 is arranged in front of the infrared transmissive lens 1, and the temperature of the mechanical shutter 8 is measured by the reference temperature detection unit 7 at the same time as the mechanical shutter 8. The output value when the shutter 8 is imaged is stored in advance. In this configuration, the temperature of the mechanical shutter 8 becomes the reference temperature. Needless to say, a shutter mechanism other than the mechanical shutter 8 has the same effect.

First, it is assumed that the temperature of the mechanical shutter 8 is T ₁ and the obtained output value is P _1. Next, except for the mechanical shutter 8, the output when the subject is imaged is measured. It is assumed that the obtained output value is P _2. Assuming that the output temperature sensitivity after the above-mentioned correction of the optical characteristics, that is, the amount of change in the output luminance when the subject temperature changes by 1 ° C. is dP / dT, the subject temperature T ₂ is expressed by the following equation (7). be able to.

Here, the output temperature sensitivity dP / dT is optically based on the non-imaging information of the infrared transmissive lens 1 accumulated in the optical member non-imaging information storage unit 5, as shown in the above-mentioned explanation regarding the correction of the optical characteristics. By correcting the characteristics, if the subject size is extremely reduced, the output sensitivity value will decrease, but in other cases, the output sensitivity value can be corrected to be constant. That is, the measurement accuracy of the subject temperature T _{2 is improved.}

On the other hand, unlike the infrared image pickup device shown in FIG. 1, it is also equivalent to taking an image of a subject having the same room temperature as a wall, a floor, etc. without configuring the mechanical shutter 8 and observing the room temperature with the reference temperature detection unit 7. The effect of is obtained.

Here, a description will be added regarding the output temperature sensitivity dP / dT. Infrared light emitted from a subject is composed of various wavelength bands, and the total amount of emitted light obtained by integrating all wavelength bands has the characteristic of the fourth power of temperature according to Planck's radiation law.

In addition, the transmittance of the optical system including the infrared transmissive lens 1 has a wavelength characteristic. For example, in the case of a Si lens, the transmittance is low for wavelengths in the 8 μm band, while the transmittance is high for wavelengths in the 10 μm to 12 μm band. Further, the wavelength characteristic also exists from the viewpoint of the absorption rate of the temperature detection unit 202 in the infrared image pickup apparatus 20. That is, the result of integrating the incident light amount wavelength characteristic, the optical system wavelength characteristic, and the sensor absorption rate wavelength characteristic and performing all-wavelength integration is the detectable incident light amount.

The output temperature sensitivity dP / dT is a value proportional to the amount of incident light that can be detected, and has a complicated functional system with respect to the subject temperature. When using the output temperature sensitivity dP / dT for calculation, a conversion table may be provided for the subject temperature, or it may be a function system of a quadratic or cubic function. If the measurement error is acceptable, it may be a linear function system.

With these correction circuit configurations and arithmetic circuit configurations, even when the subject is imaged with an optical lens that does not have ideal optical characteristics, such as a spherical Si lens, the optical member non-imaging information storage unit. By correcting the optical characteristics based on the non-imaging information of the infrared transmissive lens 1 accumulated in 5, the temperature information of the subject is not affected by the background temperature, the subject imaging size, etc., and the conversion accuracy of the subject temperature can be obtained. Can be improved. At the same time, it is possible to eliminate the deterioration of visibility due to blurring between the subject and the background, and obtain an image with an emphasized outline.

Embodiment 2.
FIG. 17 is a functional block diagram of the infrared image pickup apparatus according to the second embodiment.
In addition to the components of the infrared image pickup apparatus according to the first embodiment, the temperature detection target derivation unit 23 is arranged between the signal processing unit 3 and the optical characteristic correction unit 4. The temperature detection target derivation unit 23 limits the temperature measurement points in the screen of the infrared image pickup element 2, and corrects the optical characteristics only in the limited points. As a result, the amount of calculation required for correcting the optical characteristics can be significantly reduced. At the same time, it is possible to obtain the effect of improving the conversion accuracy of the subject temperature for the designated temperature measurement points.

For example, the temperature measurement points derived by the temperature detection target derivation unit 23 may be set only at the maximum point of the output brightness in the screen, or a plurality of points may be set by image analysis. Alternatively, the same point may be specified at all times.

Even when the subject is imaged with an optical lens having no ideal optical characteristics represented by a spherical Si lens by the infrared image pickup apparatus according to the second embodiment, the optical member non-imaging information storage unit 5 By correcting the optical characteristics based on the non-imaging information of the infrared transmissive lens 1 accumulated in, the temperature information of the subject is not affected by the background temperature, the subject imaging size, etc., and the conversion accuracy of the subject temperature is improved. At the same time as achieving the effect of the first embodiment, that is, it is possible to obtain a new effect that the calculation load can be greatly reduced.

Embodiment 3.
FIG. 18 is a functional block diagram of the infrared image pickup apparatus according to the third embodiment.
In addition to the components of the infrared image pickup apparatus according to the first embodiment, the level stabilization representative point extraction unit 21 and the brightness value adjustment unit 22 that receive the output of the level stabilization representative point extraction unit 21 are behind the temperature measurement unit 6. And place. Of the outputs measured by the temperature measuring unit 6, the portion where the subject has moved, that is, the portion where the output value does not fluctuate significantly is at room temperature level, and it is presumed that the actual temperature does not change significantly.

On the other hand, the signal component of the temperature detection unit 202 includes a substrate temperature, a self-heating component due to energization, an optical system member such as a lens, and a component of infrared light emitted from a lens barrel or the like that holds the optical system member. That is, the signal level may fluctuate due to wind, direct sunlight, other disturbance influences, fluctuations in the environmental temperature, etc., and thus the output value may not be stable.

The level stabilization representative point extraction unit 21 determines a portion where the output value does not fluctuate significantly, and outputs the coordinate data of the portion where it is determined that the output value level does not fluctuate significantly to the temperature measuring unit 6. By performing screen brightness correction or determination temperature correction so that the designated coordinate data output is constant, the temperature measurement unit 6 enables temperature determination and image generation without being affected by disturbance effects.

In the level stabilization representative point extraction unit 21, for example, a plurality of fixed points are always temperature-determined, and pixels having a small time deviation of their output values may be designated pixels, that is, representative points, or image analysis is performed on the entire screen. By doing so, the accuracy may be improved. As an example, pixels whose output value fluctuation is less than a predetermined threshold value may be extracted as designated pixels, that is, representative points. The luminance value adjusting unit 22 receives the output of the level stabilizing representative point extracting unit 21 and adjusts the luminance of the designated pixel, that is, the representative point.

Even when the subject is imaged with an optical lens having no ideal optical characteristics represented by a spherical Si lens by the infrared image pickup apparatus according to the third embodiment, the optical member non-imaging information storage unit 5 By correcting the optical characteristics based on the non-imaging information of the infrared transmissive lens 1 accumulated in, the temperature information of the subject is not affected by the background temperature, the subject imaging size, etc., so that the conversion accuracy of the subject temperature can be improved. improves.

Further, it is possible to eliminate the deterioration of visibility due to the blurring between the subject and the background, obtain the effect of the first embodiment that the image with the emphasized outline can be obtained, and at the same time, it is possible to make a determination that the influence of the disturbance is reduced. Effect can be obtained.

Embodiment 4.
FIG. 19 is a functional block diagram of the infrared image pickup apparatus according to the fourth embodiment.
In addition to the components of the infrared image pickup apparatus according to the first embodiment, a temperature influence calculation unit 9 is arranged between the signal processing unit 3 and the optical characteristic correction unit 4, and the temperature influence calculation unit 9 has a reference temperature detection unit 7. The reference temperature information from the above and the output influence calculation coefficient storage unit 10 are connected. The output influence calculation coefficient storage unit 10 stores the output displacement tendency with respect to the reference temperature held in advance.

The temperature influence calculation unit 9 corrects the output value by combining the reference temperature information from the reference temperature detection unit 7 and the output displacement tendency with respect to the reference temperature. As a result, the fluctuation of the signal level due to fluctuations in wind, direct sunlight, other disturbance effects, environmental temperature, etc. described in the infrared image pickup apparatus 20 according to the third embodiment can be corrected and the output value can be stabilized. can.

Even when the subject is imaged with an optical lens having no ideal optical characteristics represented by a spherical Si lens from the infrared image pickup apparatus according to the fourth embodiment, the optical member non-imaging information storage unit 5 By correcting the optical characteristics based on the non-imaging information of the infrared transmissive lens 1 accumulated in, the temperature information of the subject is not affected by the background temperature, the subject imaging size, etc., and the subject temperature conversion accuracy is improved. ..

Further, the effect of the first embodiment is achieved by eliminating the deterioration of visibility due to the blurring between the subject and the background and obtaining an image with the emphasized outline, and at the same time, the influence of the disturbance as in the third embodiment. It is possible to obtain a new effect of being able to make a judgment with a reduced amount of. Further, the frequency of shutter correction can be reduced, and the shutter mechanism itself can be eliminated.

Embodiment 5.
FIG. 20 is a functional block diagram of the infrared image pickup apparatus according to the fifth embodiment.
Among the components shown by the infrared image pickup device according to the first embodiment, the reference temperature detected by the reference temperature detection unit 7 may be the temperature sensor output arranged in the infrared image pickup element 2. As described above, the signal component of the temperature detection unit 202 includes the substrate temperature, the self-heating component due to energization, and the component of infrared light emitted from the optical system member such as a lens, the lens barrel holding the optical system member, and the like. .. By accurately measuring the temperature of the infrared image pickup element 2, it is possible to improve the temperature determination accuracy.

Even when the subject is imaged with an optical lens having no ideal optical characteristics represented by a spherical Si lens by the infrared image pickup apparatus according to the fifth embodiment, the optical member non-imaging information storage unit 5 By correcting the optical characteristics based on the non-imaging information of the infrared transmissive lens 1 accumulated in, the temperature information of the subject is not affected by the background temperature, the subject imaging size, etc., and the conversion accuracy of the subject temperature is improved. do. Further, it is possible to obtain the effect of the first embodiment that the deterioration of visibility due to the blurring between the subject and the background can be eliminated and the image with the emphasized outline can be obtained, and at the same time, the temperature determination accuracy can be further improved. It becomes.

The configurations of the infrared imaging devices according to the first to fifth embodiments have been described with reference to functional block diagrams. FIG. 21 shows an example of the configuration as hardware for storing each of the above-mentioned functional blocks. The hardware 300 includes a processor 301 and a storage device 302. Although the storage device is not shown, it includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. Further, the auxiliary storage device of the hard disk may be provided instead of the flash memory. The processor 301 executes the program input from the storage device 302. In this case, the program is input from the auxiliary storage device to the processor 301 via the volatile storage device. Further, the processor 301 may output data such as a calculation result to the volatile storage device of the storage device 302, or may store the data in the auxiliary storage device via the volatile storage device.

The present disclosure describes various exemplary embodiments and examples, although the various features, embodiments, and functions described in one or more embodiments are those of a particular embodiment. It is not limited to application, but can be applied to embodiments alone or in various combinations.

Therefore, innumerable variations not exemplified are envisioned within the scope of the techniques disclosed herein. For example, it is assumed that at least one component is modified, added or omitted, and further, at least one component is extracted and combined with the components of other embodiments.

1 Infrared transmission lens, 2 Infrared image pickup element, 3 Signal processing unit, 4 Optical characteristic correction unit, 5 Optical member non-imaging information storage unit, 6 Temperature measurement unit, 7 Reference temperature detection unit, 8 Mechanical shutter, 9 Temperature effect 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 target derivation unit, 100 pixel unit, 101 readout circuit, 102 drive line selection circuit , 103 signal output end, 200 drive line wiring, 201 hollow support leg wiring, 202 temperature detector, 203 signal line wiring, 204 board, 205 hollow insulation structure, 206 thermoelectric conversion mechanism, 300 hardware, 301 processor, 302 storage device

Claims (9)

An infrared transmissive lens that collects infrared light emitted from the subject,
An infrared image pickup element having a screen in which pixels for converting infrared light focused by the infrared transmissive lens into an electric signal are arranged in a two-dimensional array are used.
A signal processing unit that converts the electric signal from the infrared image pickup element into a digital signal, and
An optical characteristic correction unit that corrects optical characteristics based on the output of the signal processing unit and the output obtained by multiplying the output of the signal processing unit by the dispersion degree of the infrared transmissive lens.
A reference temperature detector that detects the reference temperature and
A temperature measuring unit that converts the absolute temperature of the subject based on the output of the optical characteristic correction unit and the output of the reference temperature detecting unit, and the temperature measuring unit.
Infrared image pickup device. The optical characteristic correction unit is characterized in that it corrects optical characteristics based on a difference value between the output of the signal processing unit and the output obtained by multiplying the output of the signal processing unit by the dispersion degree of the infrared transmissive lens. The infrared image pickup apparatus according to claim 1. The optical characteristic correction unit has optical characteristics based on a numerical value obtained by multiplying the difference value between the output of the signal processing unit and the output obtained by multiplying the output of the signal processing unit by the degree of dispersion of the infrared transmissive lens by a proportionality constant. The infrared image pickup apparatus according to claim 1, wherein the correction is performed. The screen arranged in the two-dimensional array is composed of i × j pixels, and the output value when an ideal optical system is used is the ideal output value P (x, y) in the infrared transmissive lens. The degree of dispersion to the peripheral pixels when the point light source is incident on the point (x, y) in the pixel array _{is actually output at the degree of dispersion r (x, y)} (i, j) and the point (x, y). The measured output value is Q (x, y), the proportionality constant is α, and the assumed output value S (x, y) is

If so, the following formula,

The infrared image pickup apparatus according to claim 3, wherein the ideal output value P (x, y) is calculated from the above. Any of claims 1 to 4, wherein a shutter mechanism is arranged on the front surface of the infrared transmissive lens, the temperature of the shutter mechanism is measured by the reference temperature detecting unit, and the temperature is applied to the calculation in the temperature measuring unit. The infrared image pickup device according to item 1. Further, a temperature detection target derivation unit that limits the temperature measurement location from the screen of the infrared image pickup element is further provided.
The infrared image pickup apparatus according to any one of claims 1 to 5, wherein the optical characteristic correction unit targets a representative point limited by the temperature detection target derivation unit. A level stabilization representative point extractor that extracts pixels whose output value fluctuation is less than the threshold value,
Further provided with a brightness value adjusting unit that adjusts the brightness value of the screen based on the output of the level stabilization representative point extraction unit.
Claim 1 is characterized in that the optical characteristic correction unit corrects an output value with respect to the output of the signal processing unit, including the output of the level stabilization representative point extraction unit and the luminance value adjustment unit. The infrared image pickup apparatus according to any one of 5 to 5. An output influence calculation coefficient storage unit that stores the output displacement tendency with respect to the reference temperature,
A temperature effect calculation unit that calculates the correction of the output of the reference temperature detection unit based on the output displacement tendency,
The infrared image pickup apparatus according to any one of claims 1 to 7, further comprising. The infrared image pickup apparatus according to any one of claims 1 to 8, wherein the reference temperature is the temperature of the infrared image pickup element measured by the reference temperature detection unit.

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