WO2016185699A1

WO2016185699A1 - Infrared imaging device

Info

Publication number: WO2016185699A1
Application number: PCT/JP2016/002352
Authority: WO
Inventors: 小林　誠
Original assignee: 富士フイルム株式会社
Priority date: 2015-05-21
Filing date: 2016-05-13
Publication date: 2016-11-24

Abstract

[Problem] To correct, with a high degree of accuracy, for fluctuations in the values for pixel signals output by an infrared sensor (3) caused by temperature variations, without causing an increase in the number of components of an infrared imaging device (1). [Solution] This infrared imaging device (1) comprises: an imaging optical system (2); an infrared sensor (3) wherein, by matching the center (31o) of the detection region (31) and the optical axis (O) of the imaging optical system, and making the length of the detection region (31) longer than the length of the imaging region (D) of the imaging optical system in one direction passing through the center (31o), an effective region (A) in which the detection region (31) and the imaging region (D) overlap, and reference regions (B) in which the detection region (31) and the imaging region (D) do not overlap, are provided within the detection region (31); and a signal correction unit (61) that corrects fluctuations in the values of pixel signals caused by temperature variations, by correcting values of pixel signals for effective pixels, which are pixels within the effective region (A), using the values for pixel signals for reference signals, which are pixels within the reference region (B).

Description

Infrared imaging device

The present invention relates to an imaging device that captures an infrared image, and more particularly to an infrared imaging device that corrects fluctuations in the value of a pixel signal output from an infrared sensor.

An infrared imaging device that captures an infrared image by detecting infrared rays emitted from a subject such as an object or a person with an infrared sensor is known. It is generally known that a subject whose temperature is higher than absolute zero emits infrared light, and that the higher the temperature of the subject, the more infrared light with a shorter wavelength, and the lower the temperature of the subject, the less infrared light with a longer wavelength. When a subject is imaged by an infrared imaging device, the captured image is displayed white at a high temperature and black at a low temperature. However, when a temperature change occurs in the vicinity of the infrared imaging device or the like, the detection signal detected by the infrared sensor changes due to the temperature change, and noise is generated in the captured subject image.

Therefore, in Patent Document 1, among detection regions in which pixels that are thermal infrared imaging elements are two-dimensionally arranged, pixels in a region where infrared rays are incident are effective pixels, and pixels in a region where infrared rays are not incident are reference pixels. An infrared imaging device is disclosed in which, when a temperature rise occurs in a region where a reference pixel is located, the fluctuation of the detection signal of the infrared sensor due to the temperature rise is suppressed by reducing the bias current flowing to the effective pixel. ing. In Patent Document 1, a ridge that covers the periphery of the detection region, that is, an infrared shielding body is provided inside the infrared sensor, and the infrared shielding body shields infrared light incident on the infrared sensor, thereby generating a region where no infrared light is incident. I am letting.

Further, in Patent Document 2, an infrared shielding body is provided in a housing in which an infrared sensor is accommodated so that infrared rays from a subject do not enter a part of the pixels, that is, the reference pixels, and the reference pixels are used as a reference. An infrared sensor is disclosed in which an electrical signal from another pixel is read to cancel a variation in infrared rays radiated from a casing and detect infrared rays incident from a subject.

Japanese Patent Laid-Open No. 2004-245692 JP 2006-292594 A

Generally, infrared rays emitted from a subject and infrared rays emitted from an infrared imaging device main body are incident on the infrared sensor. When the temperature of the infrared imaging device main body rises, the amount of infrared rays emitted from the infrared imaging device main body increases, so that the entire captured image becomes whitish. For example, when a high-temperature object or the like is placed on the right side of the infrared imaging apparatus main body, the captured infrared image is generally whitish on the right side. Therefore, it is desired to perform correction for reducing fluctuations in infrared rays emitted from the infrared imaging device body from the pixel signals output from the infrared sensor.

In the infrared sensor described in Patent Document 1 and Patent Document 2, for example, as shown in FIG. 19, an infrared shield 99 is provided. In Patent Document 1 and Patent Document 2, since an infrared shielding plate is required, simplification of the structure and improvement in cost saving are desired. Moreover, when such an infrared shielding body 99 is used, it has been found that the following problems occur due to the incidence of infrared rays contributing to the infrared shielding body 99 on the reference pixels. FIG. 20 is a diagram illustrating an example of the amount of infrared rays in an infrared sensor provided with the infrared shielding body 99. In FIG. 19, of the detection areas of the infrared sensor, an effective area where infrared rays from the imaging optical system 2 are incident is indicated by A, and a reference area where infrared rays from the imaging optical system 2 are not incident is indicated by B. When the infrared shielding body 99 is provided, the temperature of the infrared shielding body 99 does not increase immediately even if the temperature of the imaging apparatus body 12 rises. In contrast to the incidence of infrared rays, infrared rays radiated from the infrared shielding body 99 having a temperature lower than that of the imaging apparatus main body 12 are incident on the reference region B. As shown in FIG. The incident amount of infrared rays unrelated to the infrared rays from the imaging optical system 2 is different from the region B. For this reason, when the reference pixels in the reference region B are used, it is difficult to accurately perform correction for reducing the incident amount of infrared rays unrelated to the infrared rays from the imaging optical system 2.

The present invention has been made in view of such problems, and provides an infrared imaging device capable of accurately correcting fluctuation due to a temperature change in the value of a pixel signal output from an infrared sensor without increasing the number of components. It is intended.

An infrared imaging device of the present invention includes an imaging optical system that forms an infrared image,
It has a detection region located on the imaging surface of the imaging optical system and in which a plurality of pixels that are thermoelectric conversion elements are arranged, and outputs a pixel signal based on infrared rays incident from the imaging optical system for each pixel. An infrared sensor that matches the optical axis of the imaging optical system with the center of the detection area, and makes the length of the detection area larger than the length of the imaging area of the imaging optical system in one direction passing through the center. An infrared sensor provided with an effective area in which the detection area and the imaging area overlap in the detection area, and a reference area in which the detection area and the imaging area do not overlap;
A signal that corrects a change in the value of the pixel signal due to a temperature change by correcting the value of the pixel signal of the effective pixel that is a pixel in the effective region using the value of the pixel signal of the reference pixel that is a pixel in the reference region A correction unit.

Here, in the present invention, “infrared rays” includes all of near infrared rays, middle infrared rays, and far infrared rays.

In the present invention, the “effective region where the detection region and the imaging region overlap” means a region where infrared rays incident from the imaging optical system reach in the detection region. In addition, the “reference region where the detection region and the imaging region do not overlap” means a region where infrared rays incident from the imaging optical system do not reach in the detection region. The “reference area” means an area that is not an effective area among the detection areas.

In the infrared imaging device of the present invention, the signal correction unit can perform the offset correction by subtracting the average value of the pixel signal value of the reference pixel from the value of the pixel signal of the effective pixel.

The infrared imaging device of the present invention is provided with two or more reference regions in the detection region,
The signal correction unit may perform offset correction by subtracting the average value of the pixel signal values of the reference pixels in at least one reference region of the two or more reference regions from the value of the pixel signal of the effective pixel. .

In the infrared imaging device of the present invention, the detection area is rectangular, and reference areas are provided at the four corners of the detection area, respectively.
The signal correction unit may perform offset correction by subtracting an average value of pixel signal values of reference pixels in at least one reference region of the reference regions at the four corners from the pixel signal value of the effective pixel. .

The infrared imaging device of the present invention is provided with two or more reference regions in the detection region,
The signal correction unit calculates the average value of the pixel signals of the reference pixels in at least two reference areas among the two or more reference areas, and uses the calculated at least two average values to obtain the pixel signal of the effective pixel The shading correction can be performed on the value of.

In the present invention, “shading correction” refers to non-uniformity of incident infrared rays generated on the imaging surface of the infrared sensor, such as a decrease in the amount of infrared rays at the periphery of the imaging region caused by the imaging optical system, or to the circuit board. It means correction that reduces non-uniformity of infrared rays caused by non-uniformity of infrared rays generated from a circuit board by energization and non-uniformity of infrared rays caused by non-uniformity of external heat from an optical system or an infrared imaging device main body.

In the infrared imaging device of the present invention, the detection area is rectangular, and reference areas are provided at the four corners of the detection area, respectively.
The signal correction unit calculates an average value of the pixel signal values of the reference pixels in the reference area for at least two reference areas of the reference areas at the four corners, and uses the calculated at least two average values to Shading correction may be performed on the value of the pixel signal of the pixel.

In the infrared imaging device of the present invention, a reference region is provided at an edge in a detection region, a frame-like reference region portion in which a plurality of reference pixels are arranged is provided in the reference region, and the frame-like reference region portion is provided as a plurality of regions. Divided into
The signal correction unit calculates an average value of the pixel signal values of the reference pixels located in the plurality of regions for the plurality of divided regions, and uses each of the calculated average values for the pixel signal of the effective pixel. Shading correction may be performed on the value.

The infrared imaging device of the present invention is provided with at least one temperature sensor in the main body of the infrared imaging device,
The signal correction unit can perform a further offset correction by calculating a value corresponding to the value of the output signal from the temperature sensor to the value of the pixel signal of the effective pixel.

Here, in the present invention, the “value according to the value of the output signal from the temperature sensor” is a value set in advance for each type of infrared imaging device. For example, for each type of infrared imaging device, A table corresponding to the value of the output signal is created in advance, and a value based on this table can be used.

In the infrared imaging device of the present invention, it is preferable to provide a temperature sensor inside the main body of the infrared imaging device.

In the infrared imaging device of the present invention, it is preferable to provide a temperature sensor at a position facing the imaging optical system.

According to the infrared imaging device of the present invention, the optical axis of the imaging optical system and the center of the detection area of the infrared sensor in which a plurality of pixels as thermoelectric conversion elements are arranged coincide with each other, and in one direction passing through the center, the detection area Is made larger than the length of the imaging region of the imaging optical system, an effective region where the detection region and the imaging region overlap within the detection region, and a reference region where the detection region and the imaging region do not overlap exist. By correcting the value of the pixel signal of the effective pixel that is the pixel in the effective region using the provided infrared sensor and the value of the pixel signal of the reference pixel that is the pixel in the reference region, Since it has a signal correction unit that corrects fluctuations in the value, an effective region where infrared rays are incident on the detection region and a reference region where no infrared rays are incident, without using additional components for avoiding the incidence of infrared rays, Forming Rukoto can. Thereby, since the additional component for avoiding incidence | injection of infrared rays is unnecessary, an infrared sensor can be manufactured simply and at low cost. In addition, the amount of infrared radiation incident on each of the effective area and the reference area is not affected by the temperature difference between the infrared imaging device main body and further components for avoiding the incidence of infrared radiation. Can be accurately corrected.

1 is a schematic cross-sectional view illustrating a configuration of an infrared imaging device according to an embodiment of the present invention. 1 is a schematic block diagram illustrating a configuration of an infrared imaging device according to an embodiment of the present invention. The figure which shows an example of the 1st detection area | region of an infrared sensor The figure which shows an example of the 2nd detection area | region of an infrared sensor The figure which shows an example of the 3rd detection area | region of an infrared sensor The figure which shows an example of the 4th detection area | region of an infrared sensor Flowchart of a series of processes of the infrared imaging device of the present embodiment Flowchart of the first correction process of the signal correction unit Flowchart of second correction process of signal correction unit The figure explaining the calculation method of the correction value of shading correction when a reference area exists in four corners The figure which shows an example of the correction value of a shading correction when a reference area exists in four corners. The figure explaining the correction method when a reference field is frame shape The figure explaining the calculation method of the correction value of the shading correction when a reference area is frame shape The figure which shows an example of the correction value of shading correction when a reference area is frame shape Schematic sectional drawing explaining the structure of the infrared imaging device which concerns on the 2nd Embodiment of this invention. Flowchart of third correction process of signal correction unit The figure which shows the relationship between the value of the output signal from the temperature sensor and the calculated value according to this value Flowchart of fourth correction process of signal correction unit Schematic cross-sectional view illustrating the configuration of a conventional infrared imaging device The figure which shows an example of the amount of infrared rays in an infrared imaging device provided with the shield of FIG.

Hereinafter, an embodiment of an infrared imaging device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view illustrating the configuration of an infrared imaging device according to an embodiment of the present invention, and FIG. 2 is a schematic block diagram illustrating the configuration of an infrared imaging device 1 according to an embodiment of the present invention. . As shown in FIG. 1, the infrared imaging device 1 according to the present embodiment is installed in an infrared imaging device main body 12 including a first main body portion 10 and a second main body portion 11, and the first main body portion 10. An imaging optical system 2 capable of imaging infrared rays emitted from a subject on the imaging plane 30 and a second main body 11, located on the imaging plane 30 of the imaging optical system 2, An infrared sensor 3 having a detection region 31 in which a plurality of pixels as conversion elements are arranged and outputting pixel signals based on infrared rays incident from the imaging optical system 2 is provided for each pixel.

The infrared imaging device main body 12 is made of a metal material such as aluminum or stainless steel or a resin material such as plastic, but the infrared imaging device main body 12 of this embodiment is made of stainless steel. The internal structure of the infrared imaging device body 12 will be described later in detail.

The imaging optical system 2 is a lens group composed of one or more lenses. The lenses are held by a holding frame, and the holding frame is fixed to the first main body 10. In the present embodiment, the imaging optical system 2 is described as a fixed focus optical system, but the present invention is not limited to this, and may be a variable focus optical system.

The infrared sensor 3 is driven by a drive control unit (not shown), takes a subject image formed in the detection area 31 as an infrared image, converts it into a pixel signal, and outputs it. The infrared sensor 3 outputs a pixel signal by sequentially transferring charges accumulated in each pixel and converting them into an electrical signal.

Here, what is characteristic in the present invention is that the region C of the detection region 31 is configured to be larger than the imaging region D of the imaging optical system 2 as shown in FIG. Here, FIG. 3 shows a diagram illustrating a first embodiment of the detection region 31 of the infrared sensor 3. It is assumed that the region C of the detection region 31 of the infrared sensor 3 of the present embodiment has a rectangular shape, and the imaging region D of the imaging optical system 2 has a circular shape. When the optical axis of the imaging optical system 2, that is, the center O of the imaging region D is matched with the center 31o of the region C of the detection region 31 of the infrared sensor 3, and a straight line passing through the centers O and 31o is a straight line d The length of the region C of the detection region 31 is configured to be greater than the length of the imaging region D on the straight line d. In the present embodiment, the straight line d is a straight line connecting diagonal lines of the region C of the detection region 31.

In the detection region 31, a region where the infrared light that has passed through the imaging optical system 2 is incident, that is, a region where the region C of the detection region 31 and the imaging region D of the imaging optical system 2 overlap is an effective region AR. A region where the transmitted infrared light does not enter, that is, a region where the region C of the detection region 31 and the imaging region D of the imaging optical system 2 do not overlap with each other becomes the reference region BR. In the present embodiment, the length of the region C of the detection region 31 is larger than the length of the imaging region D also on the straight line orthogonal to the straight line d in FIG. Reference regions BR are formed at the four corners of the region C, respectively. Note that pixels that are a plurality of thermoelectric conversion elements are arranged in the effective region AR and the reference region BR, and pixels located in the effective region AR become effective pixels and pixels located in the reference region BR become reference pixels. In the present embodiment, the area that forms the largest rectangle in the effective area AR and the area in which the effective pixels are arranged in a matrix is set as the effective area A, and is output in the effective pixels in the effective area A. Assume that the pixel data forms an infrared image.

Further, in the present embodiment, for the reference areas BR formed at the four corners, signal correction, which will be described later, is made the reference area B1, the upper left is the reference area B2, the lower left is the reference area B3, and the lower right is the reference area B4. The unit 61 performs infrared image signal correction processing using pixel data output from the reference pixels in the reference regions B1 to B4.

As described above, when the reference areas B1 to B4 are provided at positions other than the effective area AR, no additional parts are required for avoiding the incidence of infrared rays from the imaging optical system 2 to the reference areas B1 to B4. Therefore, the infrared sensor 3 can be manufactured easily and at low cost. Further, it is advantageous to provide the reference areas B1 to B4 in the area excluding the imaging area D while suitably securing the positions and areas of the reference areas B1 to B4 with respect to the effective area AR. For example, as shown in FIG. 19, the lens of the imaging optical system 2 is more than the case where the region C of the detection region 31 overlaps the imaging region D, that is, all the pixels in the region C of the detection region 31 become effective pixels. Therefore, the cost of the imaging optical system 2 can be reduced.

In the example of FIG. 3, the infrared sensor 3 is a rectangular sensor, and the four corners of the infrared sensor 3 are reference areas BR that are areas that do not overlap with the imaging area D. The reference pixel used for the infrared image signal correction process can be arbitrarily selected from the reference pixels in the reference region BR. That is, the region formed by the reference pixels to be used can be selectively provided in an arbitrary shape at an arbitrary position in the reference region BR. The position information of the effective pixel and the reference pixel is stored in the storage unit 7 and is referred to by the signal correction unit 61 as appropriate.

For example, the length of the region C of the imaging region of the imaging optical system 2 relative to the length of the detection region 31 of the infrared sensor 3 on at least one straight line included in the imaging surface 30 as described above and passing through the optical axis. The use effective area A and the reference area B having different shapes from the above-described embodiment may be provided by appropriately changing the sizes. 4 to 6 show examples of other embodiments of the detection region 31 of the infrared sensor 3, respectively. 4 to 6 are schematic diagrams for explaining the configuration of the detection region 31 of the infrared sensor 3, and the size of each region is different from the actual one.

As shown in FIG. 4, the second detection region 31 of the infrared sensor 3 includes the optical axis of the imaging optical system 2, that is, the center O of the imaging region D, and the center 31 o of the region C of the detection region 31 of the infrared sensor 3. The vertical line connecting the upper and lower sides of the detection region 31 of the infrared sensor 3 through the centers O and 31o is defined as a straight line d, and the length of the region C of the detection region 31 on the straight line d is the imaging region D. It is configured to be larger than the length of. As a result, in the detection region 31 of FIG. 4, the region where the infrared rays that have passed through the imaging optical system 2 are incident, that is, the region C of the detection region 31 and the imaging region D of the imaging optical system overlap. An effective area AR which is an area, and an outer peripheral portion surrounding the imaging area D is an area where infrared rays that have passed through the coupling optical system 2 do not enter, that is, an area where the imaging area D of the imaging optical system does not overlap with the area C of the detection area 31 Is a reference region BR.

Also in the second detection area 31, as in the detection area 31 of the above-described embodiment, an area that forms the largest rectangle in the effective area AR and in which effective pixels are arranged in a matrix is used effective area It is assumed that A is the pixel data output from the effective pixels in the use effective area A and forms an infrared image. Further, in the reference area BR, a signal correction unit 61, which will be described later, is referred to as reference areas B1 and B2, which are tangent to the imaging area D and have upper and lower ends from the horizontal line of the detection area 31, respectively. Performs signal correction processing of an infrared image using pixel data output in reference pixels in the reference regions B1 and B2.

Further, as shown in FIG. 5, the third detection region 31 of the infrared sensor 3 includes an optical axis of the imaging optical system 2, that is, a center O of the imaging region D, and a region C of the detection region 31 of the infrared sensor 3. A horizontal line connecting the left and right of the detection region 31 of the infrared sensor 3 through the centers O and 31o is defined as a straight line d, and the length of the region C of the detection region 31 is imaged on the straight line d. It is configured to be larger than the length of the region D. Accordingly, in the detection region 31 of FIG. 5, the region where the infrared rays that have passed through the imaging optical system 2 are incident, that is, the region C of the detection region 31 and the imaging region D of the imaging optical system overlap. The left and right regions adjacent to the imaging region D are regions where the infrared rays that have passed through the coupling optical system 2 are not incident, that is, the region C of the detection region 31 and the imaging region D of the imaging optical system overlap. The reference region BR is a region that should not be used.

In the third detection area 31 as well, as in the detection area 31 of the above-described embodiment, the area that forms the largest rectangle in the effective area AR and the area in which the effective pixels are arranged in a matrix is used effective area It is assumed that A is the pixel data output from the effective pixels in the use effective area A and forms an infrared image. In the reference region BR, a signal correction unit 61, which will be described later as reference regions B3 and B4, which are tangents to the imaging region D and have left and right ends from the vertical line of the detection region 31 as reference regions B3 and B4, respectively. Infrared image signal correction processing is performed using pixel data output from the reference pixels in the reference regions B3 and B4. The third detection region 31 is configured such that the length of the region C of the detection region 31 is larger than the length of the imaging region D on the straight line d, that is, in the horizontal direction of the detection region 31. In the vertical direction of the detection region 31, the length of the region C of the detection region 31 is not configured to be greater than the length of the imaging region D. That is, the length of the area C of the detection area 31 is shorter than the length of the imaging area D in the vertical direction. Therefore, when the second detection region 31 and the third detection region 31 are the same size, the third detection region 31 is a region of the detection region 31 than the second detection region 31. Since the area where C and the imaging area D of the imaging optical system overlap, that is, the effective area AR becomes wide, the usable effective area A can be widened.

Further, the fourth detection region 31 of the infrared sensor 3 includes an optical axis of the imaging optical system 2, that is, a center O of the imaging region D and a region C of the detection region 31 of the infrared sensor 3, as shown in FIG. A vertical line connecting the center 31o and passing through the centers O and 31o and connecting the upper and lower sides of the detection region 31 of the infrared sensor 3 is a straight line d1, and the right and left of the detection region 31 of the infrared sensor 3 is passed through the centers O and 31o. When the horizontal line to be connected is a straight line d2, the length of the region C of the detection region 31 is configured to be larger than the length of the imaging region D on the straight lines d1 and d2. Thereby, in the detection region 31 of FIG. 6, the region where the infrared rays that have passed through the imaging optical system 2 are incident, that is, the region C of the detection region 31 and the imaging region D of the imaging optical system overlap. An effective area AR which is an area, and an outer peripheral portion surrounding the imaging area D is an area where infrared rays that have passed through the coupling optical system 2 do not enter, that is, an area where the imaging area D of the imaging optical system does not overlap with the area C of the detection area 31 Is a reference region BR.

In the fourth detection area 31 as well, as in the detection area 31 of the above-described embodiment, an area that forms the largest rectangle in the effective area AR and in which effective pixels are arranged in a matrix is used effective area It is assumed that A is the pixel data output from the effective pixels in the use effective area A and forms an infrared image. Further, in the reference region BR, it is a tangent to the imaging region D and includes an upper end and a lower end from the horizontal line of the detection region 31, and the upper end and the lower end. The signal correction unit 61, which will be described later, uses a frame-shaped region around the region C of the detection region 31 formed with the same width as the reference region B, and uses pixel data output in the reference pixels in the reference regions B1 and B2. The infrared image signal correction process is then performed.

The effective pixels in the usable effective area A and the reference pixels in the reference area B are infrared detecting elements (infrared detectors) that can detect infrared rays (wavelengths of 0.7 μm to 1 mm). It is an infrared detecting element capable of detecting 8 μm to 15 μm). For example, a microbolometer-type or SOI (Silicon-on-Insulator) diode-type infrared detection element can be used as the infrared detection element used as the effective pixel and the reference pixel.

Next, the configuration of the infrared imaging device 1 will be described. As shown in FIG. 2, the infrared imaging device 1 includes the imaging optical system 2, the infrared sensor 3, an analog signal processing unit 4 that performs various analog signal processing such as amplifying an output signal from the infrared sensor 3, and the like. A / D conversion (Analog-to-Digital conversion) unit 5 for converting the analog image signal processed by the analog signal processing unit 4 into digital image data, and the digital image data converted by the A / D conversion unit 5 A digital signal processing unit 6 that performs various signal processing, a storage unit 7 that stores information associated with various digital signal processing, and an output that outputs an infrared image subjected to the digital signal to the storage unit 7 or a display unit (not shown). Part 8.

The storage unit 7 stores various types of information used in the digital signal processing unit 6, infrared images subjected to various digital signal processing, and the like as necessary, and a volatile memory such as a DRAM (Dynamic Random Access Memory). A non-volatile memory such as a flash memory is included. In the present embodiment, the storage unit 7 is provided separately from the digital signal processing unit 6, but the present invention is not limited to this, and the storage unit 7 is provided in the digital signal processing unit 6. Also good.

The output unit 8 outputs an infrared image subjected to various digital signal processing to the storage unit 7, a display unit (not shown), or a storage unit outside the apparatus by wireless or wired communication.

The digital signal processing unit 6 includes a signal correction unit 61 that performs correction processing on the value of the pixel signal output from the infrared sensor 3. Normally, when the temperature of the infrared imaging device main body 12 rises, the amount of infrared radiation emitted from the infrared imaging device main body 12 increases, and the entire captured infrared image becomes whitish. In view of this, the signal correction unit 61 of the present embodiment uses pixels in the reference region B in order to perform correction for offsetting a value that contributes to infrared rays emitted from the infrared imaging device main body 12 from the pixel signals output from the infrared sensor 3. The value of the pixel signal of the effective pixel that is the pixel in the use effective area A is corrected using the value of the pixel signal of a certain reference pixel.

Here, a correction method by the signal correction unit 61 will be described with reference to a flowchart. FIG. 7 shows a flowchart of a series of processes of the infrared imaging apparatus 1 of the present embodiment.

As shown in FIG. 7, the infrared imaging apparatus 1 of the present embodiment first images a subject (S1), and the infrared sensor 3 analogly outputs pixel signals based on infrared rays incident from the imaging optical system 2 for each pixel. Output to the signal processing unit 4, the analog signal processing unit 4 performs various analog signal processing such as amplifying the detection signal from the infrared sensor 3, and the A / D conversion unit 5 converts the processed analog image signal into digital image data. The digital signal processing unit 6 performs various signal processing on the digital image data converted by the A / D conversion unit 5, and stores the image data subjected to the various signal processing in the storage unit 7 (S2). ).

Next, the signal correction unit 61 reads the image data stored in the storage unit 7 and performs a correction process on the image data (S3). Here, the first correction processing by the signal correction unit 61 will be described in detail. FIG. 8 is a flowchart of the first correction process of the signal correction unit 61 of this embodiment.

The signal correction unit 61 calculates an average value of pixel signal values of reference pixels that are pixels in the reference region B (S11). When the reference region B is formed at the four corners of the detection region C as shown in FIG. 3, the values of all pixel signals of the reference pixels in the reference regions B1 to B4 at the four corners An average value M is calculated. The number of reference pixels in the upper left reference area B1, i, the number of reference pixels in the upper right reference area B2, j, the number of reference pixels in the lower left reference area B3, and the lower right reference area B4 If the number of reference pixels is m, the average value M can be calculated by the following equation (1).
M = (B1 ₁ + B1 ₂ +,..., + B1 _i + B2 ₁ + B2 ₂ +,... + B2 _j
+ B3 ₁ + B3 ₂ +, ..., + B3 _k + B4 ₁ + B4 ₂ +, ..., + B4 _m )
/ (I + j + k + m) (1)
Here, B1 ₁ , B1 _i are the pixel signal values of the reference pixels in the reference area B1, B2 ₁ , B2 _j are the pixel signal values of the reference pixels in the reference area B2, and B3 ₁ , B3 _k represents the value of the pixel signal of each reference pixel in the reference region B3, and B4 ₁ , B4 _m represent the value of the pixel signal of each reference pixel in the reference region B4.

As an average value calculation method, the pixel signal values of all the reference pixels in the reference regions B1 to B4 may be added together as in the above formula (1), and then divided by the number of pixels. An average value may be calculated for each of the reference regions B1 to B4, and a value obtained by adding the calculated four average values and dividing by four may be used as the average value. That is, the average value M may be calculated by the following formula (2).
_{_{_{_{M = ((B1 1 + B1}}}} 2 + ,,, + B1 i) / i + (B2 1 + B2 2 + ,,, + B2 j) / j + (B3 1 + B3 2 + ,,, + B3 k) / k + (B4 1 + B4 2 +, ..., + B4 _m ) / m) / 4 (2)

In addition, when the reference area B is provided at the upper and lower ends of the detection area C as shown in FIG. 4, the reference pixel in the reference area B1 at the upper end and the reference area B2 at the lower end are referred to. An average value M of values of both pixel signals of the pixel is calculated. If the number of reference pixels in the reference region B1 at the upper end is i and the number of reference pixels in the reference region B2 at the lower end is j, the average value M can be calculated by the following equation (3).
M = (B1 ₁ + B1 ₂ +,..., + B1 _i + B2 ₁ + B2 ₂ +,... + B2 _j ) / (i + j) (3)
Here, B1 _1, ..., B1 _i indicate the value of the pixel signal of each reference pixel in the reference area B1, and B2 _1, ... B2 _j indicate the value of the pixel signal of each reference pixel in the reference area B2.

As shown in FIG. 5, when the reference area B is provided at the left and right ends of the detection area C, as in the case where the reference area B is provided at the upper and lower ends of the detection area C, An average value M of pixel signal values of both the reference pixel in the reference region B3 at the left end and the reference pixel in the reference region B4 at the right end is calculated. When the number of reference pixels in the left end reference area B3 is i and the number of reference pixels in the right end reference area B4 is j, the average value M can be calculated by the following equation (4).
M = (B3 ₁ + B3 ₂ +,..., + B3 _i + B4 ₁ + B4 ₂ +,... + B4 _j ) / (i + j) (4)
Here, B3 _1, ..., B3 _i indicate the pixel signal value of each reference pixel in the reference area B3, and B4 _1, ... B4 _j indicate the value of the pixel signal of each reference pixel in the reference area B4.

In addition, when the reference region B is provided in a frame shape at the edge of the detection region C as shown in FIG. 6, the average value of the pixel signal values of the reference pixels in the frame-shaped reference region B is calculated. calculate. When the number of reference pixels in the reference region B is i, the average value M can be calculated by the following equation (5).
M = (B ₁ + B ₂ +,... + B _i ) / i (5)
Here, B _1, ... B _i indicate pixel signal values of the respective reference pixels in the reference region B.

Then, as shown in FIG. 8, the signal correction unit 61 subtracts the calculated average value M from each of the pixel signal values of the effective pixels in the use effective area A to obtain the value of the image signal. Offset correction is performed (S12).

Next, as shown in FIG. 7, the signal correction unit 61 stores the value of the pixel signal subjected to the correction process in the storage unit 7 (S4). The image data stored in the storage unit 7 is appropriately output by the output unit 8 to an external storage unit or a display unit (not shown). The corrected image data may be appropriately subjected to other necessary correction processing by the digital signal processing unit 6 of the infrared imaging device 1.

In the infrared imaging device 1 of the present embodiment, the reference region B can capture only the infrared radiation from the infrared imaging device body 12 at the same timing as the use effective region A captures the infrared radiation from the subject. Therefore, the average value M calculated above is a value resulting from the infrared rays incident from the infrared imaging device main body 12.

In the conventional infrared imaging device 100 shown in FIG. 19, a region where infrared rays are not incident is generated by blocking infrared rays incident on the infrared sensor with an infrared shield, and an infrared shielding plate is required, so that the structure is simple. Improvement of cost and cost saving is desired. Moreover, in the conventional infrared imaging device 100, even if the temperature of the imaging device main body 12 rises, the temperature of the infrared shielding body 99 does not rise immediately, so that the temperature in the reference region B is lower than that of the imaging device main body 12. Infrared rays radiated from the infrared shielding body 99 are added. Accordingly, the amount of incident infrared rays differs between the use effective area A and the reference area B, and the correction amount to be offset differs between the use effective area A and the reference area B. Therefore, the effective pixels in the use effective area A are different. In the offset correction in which the average value M is subtracted from each of the pixel signal values, it is difficult to perform correction with high accuracy.

However, as described above, in the infrared imaging device 1 of the present embodiment, the optical axis O of the imaging optical system 2 and the center 31o of the detection region 31 of the infrared sensor 3 are made to coincide with each other, and the unidirectional direction passing through the centers O and 31o. On the straight line d, by making the length of the region C of the detection region 31 larger than the length of the image formation region D of the imaging optical system 2, the region C of the detection region 31 and the region C of the detection region 31 are included in the detection region 31 of the infrared sensor 3. Since the effective area AR where the imaging area D overlaps, the area C of the detection area 31 and the reference area BR where the imaging area D does not overlap are provided, even without using additional components to avoid the incidence of infrared rays, An effective area AR in which infrared rays are incident and a reference area BR in which no infrared rays are incident can be formed in the detection area 31. Thereby, since the additional component for avoiding incidence | injection of infrared rays is unnecessary, the infrared sensor 3 can be manufactured simply and at low cost. In addition, the amount of infrared radiation incident on each of the effective area AR and the reference area BR is not affected by the temperature difference between the infrared imaging apparatus main body 12 and a further component for avoiding the incidence of infrared radiation. The fluctuation of the signal value can be accurately corrected.

When the offset correction is performed using the average value M of the pixel signal values of all the reference pixels in the reference areas B1 to B4 at the four corners as shown in FIG. Can reduce the influence of the temperature difference caused by. In addition, when the offset correction is performed using the average value M of the pixel signals of both the reference pixel in the reference region B1 at the upper end and the reference pixel in the reference region B2 at the lower end as shown in FIG. The influence of the temperature difference that occurs in the vertical direction of the infrared imaging device main body 12 can be reduced. In addition, when the offset correction is performed using the average value M of the pixel signals of both the reference pixel in the reference region B3 at the left end and the reference pixel in the reference region B4 at the right end as shown in FIG. The influence of the temperature difference that occurs in the left-right direction of the imaging device body 12 can be reduced. Further, when the offset correction is performed using the average value M of the pixel signal values of the reference pixels in the frame-like reference region B as shown in FIG. 6, the influence of the temperature difference generated around the infrared imaging device main body 12. Can be reduced.

In this embodiment, reference areas B1 to B4 at the four corners in FIG. 3, reference areas B1 and B2 at the upper and lower end parts in FIG. 4, and reference areas B3 and B4 at the left and right end parts in FIG. Although the average value of the pixel signal values of the pixels is used for offset correction, the present invention is not limited to this. For example, in FIG. 3, one reference area selected from the reference areas B1 to B4 at the four corners. An average value of pixel signal values of only reference pixels may be used. In FIG. 4, the average value of the pixel signals of the reference pixels only in the reference region B1 at the upper end may be used, or the average value of the pixel signals of the reference pixels in the reference region B2 at the lower end is used. You may do it. Further, in FIG. 5, the average value of the pixel signals of the reference pixels only in the reference region B3 at the left end may be used, or the average value of the pixel signals of the reference pixels only in the reference region B4 at the right end is used. It may be changed as appropriate.

Next, the second correction processing by the signal correction unit 61 of this embodiment will be described in detail. Here, FIG. 9 is a flowchart of the second correction processing of the signal correction unit 61, FIG. 10 is a diagram for explaining a correction method when the reference area is at four corners, and FIG. 11 is a reference area having four corners. FIG. 12 is a diagram illustrating a method for calculating a correction value for shading correction when the reference area is in FIG. 12, FIG. 12 is a diagram illustrating a correction method when the reference area is frame-shaped, and FIG. 13 is a shading correction when the reference area is frame-shaped. FIG. 14 is a diagram illustrating a method for calculating the correction value, and FIG. 14 is a diagram illustrating an example of a correction value for shading correction when the reference region has a frame shape.

As shown in FIG. 9, the signal correction unit 61 first calculates an average value of pixel signal values of reference pixels that are pixels in the reference region B (S21). When the reference area B is provided at the four corners of the detection area C as shown in FIG. 3, the average value M1 of the pixel signal values of the reference pixels in the upper left reference area B1, and the upper right The average value M2 of the pixel signal values of the reference pixels in the reference region B2, the average value M3 of the pixel signal values of the reference pixels in the lower left reference region B3, and the pixel signal values of the reference pixels in the lower right reference region B4 An average value M4 is calculated. When the number of reference pixels in the upper left, upper right, lower left, and lower right reference regions B1 to B4 is i, j, k, and m, the average values M1 to M4 are expressed by the following equations (6-1), It can be calculated by (6-2), (6-3), (6-4).
M1 = (B1 ₁ + B1 ₂ +,... + B1 _i ) / i (6-1)
M2 = (B2 ₁ + B2 ₂ +,... + B2 _j ) / j (6-2)
M3 = (B3 ₁ + B3 ₂ +,... + B3 _k ) / k (6-3)
M4 = (B4 ₁ + B4 ₂ +,... + B4 _m ) / m (6-4)
Here, B1 ₁ , B1 _i are the pixel signal values of the reference pixels in the reference area B1, B2 ₁ , B2 _j are the pixel signal values of the reference pixels in the reference area B2, and B3 ₁ , B3 _k represents the value of the pixel signal of each reference pixel in the reference region B3, and B4 ₁ , B4 _m represent the value of the pixel signal of each reference pixel in the reference region B4.

When the reference area B is provided at the upper and lower ends of the detection area C as shown in FIG. 4, the average value M1 of the pixel signal values of the reference pixels in the reference area B1 at the upper end is An average value M2 of pixel signal values of the reference pixels in the reference region B2 at the lower end is calculated. If the number of reference pixels in the reference region B1 at the upper end is i and the number of reference pixels in the reference region B2 at the lower end is j, the average values M1 and M2 are expressed by the following equations (7-1) and (7- 2).
M1 = (B1 ₁ + B1 ₂ +,... + B1 _i ) / i (7-1)
M2 = (B2 ₁ + B2 ₂ +,... + B2 _j ) / j (7-2)
Here, B1 _1, ..., B1 _i indicate the value of the pixel signal of each reference pixel in the reference area B1, and B2 _1, ... B2 _j indicate the value of the pixel signal of each reference pixel in the reference area B2.

As shown in FIG. 5, when the reference area B is provided at the left and right ends of the detection area C, as in the case where the reference area B is provided at the upper and lower ends of the detection area C, An average value M3 of pixel signal values of the reference pixels in the reference region B3 at the left end portion and an average value M4 of pixel signal values of the reference pixels in the reference region B4 at the right end portion are calculated. If the number of reference pixels in the left end reference region B3 is i and the number of reference pixels in the right end reference region B4 is j, the average values M3 and M4 are expressed by the following equations (8-1) and (8-2). ).
M3 = (B3 ₁ + B3 ₂ +,... + B3 _i ) / i (8-1)
M4 = (B4 ₁ + B4 ₂ +,... + B4 _j ) / j (8-2)
Here, B3 _1, ..., B3 _i indicate the pixel signal value of each reference pixel in the reference area B3, and B4 _1, ... B4 _j indicate the value of the pixel signal of each reference pixel in the reference area B4.

Further, when the reference area B is provided in a frame shape at the edge of the detection area C as shown in FIG. 6, the frame-shaped reference area B is divided into a plurality of reference areas. In the present embodiment, as shown in FIG. 12, the upper row and the lower row are each divided into five divided reference regions B11 to B15, B51 to B55, and the remaining reference regions, that is, divided reference regions B11 to B15, B51 to The left column and the right column, which are reference regions excluding B55, are divided into three divided reference regions B21 to B41 and B25 to B45, respectively, to create a total of 16 divided reference regions B11 to B55.

Next, average values M11 to M55 of the pixel signal values of the reference pixels in the divided reference areas B11 to B55 are calculated for each of the 16 divided reference areas B11 to B55 created. If the number of reference pixels in the reference area B11 is i, the average value M11 can be calculated by the following equation (9).
M11 = (B ₁ + B ₂ +,... + B _i ) / i (9)
Here, B _1, ... B _i indicate pixel signal values of the respective reference pixels in the reference region B.
The average values M12 to M55 of the remaining reference areas B12 to B55 can be calculated in the same manner as the reference area M11.

Next, as shown in FIG. 9, the signal correction unit 61 performs shading correction on the value of the pixel signal of the effective pixel in the use effective area A (S22). When the reference area B is provided at the four corners of the detection area C as shown in FIG. 3, the reference pixels in the calculated reference areas B1 to B4 for each of the four reference areas B1 to B4. The shading amount S is calculated using the average values M1 to M4 of the pixel signal values. Here, a method for calculating the shading amount S will be described in detail.

In the following description, the row direction that is the direction in which the pixel columns of the use effective area A extend is the x direction, the column direction that is the direction in which the pixel rows extend is the y direction, and the position of each effective pixel in the use effective area A is Expressed in the xy coordinate system. As shown in FIG. 10, the x coordinate of the endmost column on one end side in the row direction is x1, the x coordinate of the endmost column on the other end side is x2, and the y coordinate of the endmost row on the one end side in the column direction is y1. The y coordinate of the outermost row on the other end side in the column direction is y2. Note that x1 <x2 and y1 <y2. Further, the average value of the pixel signal values of the reference pixels in the reference areas B1 to B4 is set as Z11, Z12, Z21, and Z22, respectively, and the shading amount S at the coordinates (x, y) is calculated.

As shown in FIG. 10, when y = y1, the shading amount S (x, y) is expressed by the following equation (10-1).
S (x, y1) = a1x + b1 (10-1)
Here, a1 is the inclination in the vertical direction and is represented by the following formula (10-2).
a1 = (Z12-Z11) / (x2-x1) (10-2)
Further, b1 is an intercept in the vertical direction, and is expressed by the following equation (10-3) when x = x1 and y = y1 = Z11.
b1 = S (x1, y1) −a1x1 = Z11− (Z12−Z11) / (x2−x1) × x1 (10-3)

Similarly, when y = y2, the shading amount S (x, y) is expressed by the following equation (11-1).
S (x, y2) = a2x + b2 (11-1)
Here, a2 is an inclination and is represented by the following formula (11-2).
a2 = (Z22-Z21) / (x2-x1) (11-2)
Further, b2 is an intercept, and is expressed by the following formula (11-3) when x = x1 and y = y2 = Z21.
b2 = S (x1, y2) −a2x1 = Z21− (Z22−Z21) / (x2−x1) × x1 (11-3)

Using the above equations (10-1) to (11-3), the shading amount S (x, y) at the coordinates (x, y) is expressed by the following equation (12).
S (x, y) = ((a2x + b2) − (a1x + b1)) / (y2−y1)
× (y−y1) + (a1x + b1)
(12)

Next, an example of the correction value of the shading correction calculated by the above-described shading amount calculation method will be described. The average values Z11, Z12, Z21, and Z22 of the pixel signals of the reference pixels in the reference regions B1 to B4 calculated in step S21 of FIG. 9 are expressed as Z11 = 10, Z12 = 20, as shown in FIG. It is assumed that Z21 = 60 and Z22 = 300. First, when the slope is calculated in each of the columns x1 to x2 in FIG. 11, the values shown at the bottom of the table in FIG. 11 are calculated. For example, when x = x1, (60-10) / (10-2) = 6.25.

Similarly, when the slope is calculated in each row y1-y2 in FIG. 11, the value shown on the right side of the table in FIG. 11 is calculated. For example, when y = y1, (20-10) / (5-1) = 2.5.

In this embodiment, when y = y1 = 2, the slope a1 = 2.5 from the above equation (10-2), and the intercept b1 = 7.5 from the above equation (10-3). When y = y2 = 10, the slope a2 = 60 from the above equation (11-2), and the intercept b2 = 0 from the above equation (11-3).

When the above values are substituted into the above equation (12), for example, the shading amount S at coordinates (x2, y1) = (2, 2) is S = 12.5. Similarly, when the coordinate value is substituted into the above equation (12), the value of the shading amount S shown in FIG. 11 can be calculated. Then, the shading correction is performed by calculating the calculated shading amount S to the value of the pixel signal of the effective pixel in the use effective area A.

When shading correction is performed using average values M1 to M4 of pixel signal values of reference pixels in the four reference regions B1 to B4 provided at the four corners of the detection region C as shown in FIG. Since the shading amount S in the vertical direction and the horizontal direction of the infrared image due to the temperature difference around the infrared imaging device main body 12 can be acquired in detail, the unevenness of the entire infrared image can be accurately corrected.

Further, when the reference area B is provided at the upper and lower ends of the detection area C as shown in FIG. 4, the average of the pixel signal values of the reference pixels in the reference area B1 at the upper end calculated. Using the value M1 and the average value M2 of the pixel signals of the reference pixels in the reference region B2 at the lower end, linear interpolation is performed to calculate the shading amount S of each effective pixel in the use effective region A, and the calculated shading The shading correction is performed by calculating the amount S to the value of the pixel signal of each effective pixel in the use effective area A.

For example, when a high-temperature object or the like is placed on the upper side of the infrared imaging device main body 12, the captured infrared image becomes generally whitish on the upper side. That is, the density of the infrared image captured by the temperature difference around the infrared imaging device body 12 is uneven. When performing shading correction using the average values M1 and M2 of the pixel signals of the reference pixels in the reference region B1 at the upper end and the reference pixels in the reference region B2 at the lower end as shown in FIG. Since the shading amount S in the vertical direction of the image can be acquired in detail, the unevenness in the vertical direction of the infrared image can be accurately corrected.

Further, as shown in FIG. 5, when the reference area B is provided at the left and right ends of the detection area C, the same as when the reference area B is provided at the upper and lower ends of the detection area C. Further, linear interpolation is performed using the calculated step difference between the average value M3 of the pixel signal values of the reference pixels in the reference region B3 at the left end portion and the average value M4 of the pixel signal values of the reference pixels in the reference region B4 at the right end portion. The shading correction S is performed by calculating the shading amount S of the effective pixels in the use effective region A and calculating the calculated shading amount S to the value of the pixel signal of the effective pixels in the use effective region A.

When performing shading correction using the average values M3 and M4 of the pixel signals of the reference pixels in the reference region B3 at the left end and the reference pixels in the reference region B4 at the right end as shown in FIG. Since the shading amount S in the left-right direction of the image can be acquired in detail, unevenness in the left-right direction of the infrared image can be accurately corrected.

Further, when the reference area B is provided in a frame shape at the edge of the detection area C as shown in FIG. 6, the calculation is performed for each of the 16 divided reference areas B11 to B55 created above. The shading amount S is calculated using the average values M11 to M55 of the pixel signal values of the reference pixels in the divided reference regions B11 to B55. The shading amount S can be calculated using, for example, pixel signal values of surrounding pixels. Here, a method for calculating the shading amount S will be described in detail.

As shown in FIG. 13, when the average values of the pixel signals of the reference pixels in the divided reference areas B11 to B55 are Z11 to Z55, respectively, the shading amount in the upper left effective pixel Z22 in the use effective area A is expressed by the following equation. It can be calculated by (13).
Z22 = (Z12−Z11) + (Z21−Z11) + Z11
= Z12 + Z21-Z11 (13)

Further, the shading amount at the upper right effective pixel Z24 in the use effective area A can be calculated by the following equation (14).
Z24 = (Z14−Z15) + (Z25−Z15) + Z15
= Z14 + Z25-Z15 (14)

That is, the usable effective area A is divided into four areas divided in the center in the horizontal direction and the vertical direction, and the effective pixel T1 located in the upper left area with respect to the center of the usable effective area A is the effective pixel T1. The average value M or effective pixel value of the divided reference region B adjacent to the upper and left sides is added, and the average value M or effective pixel value of the divided reference region B adjacent to the upper left of the effective pixel T1 is added from the added value. The shading amount S at the effective pixel T is calculated by subtracting the value. For the effective pixel T2 located in the lower left area with respect to the center of the effective area A, the average value M or the effective pixel value of the divided reference area B adjacent to the lower and left sides of the effective pixel T2 is added. Then, the shading amount S at the effective pixel T2 is calculated by subtracting the average value M or the value of the effective pixel of the divided reference region B adjacent to the lower left of the effective pixel T2 from the added value.

Similarly, for the effective pixel T3 located in the upper right area with respect to the center of the effective area A, the average value M or the effective pixel value of the divided reference area B adjacent to the upper and right sides of the effective pixel T3 is set. The shading amount S in the effective pixel T3 is calculated by adding and subtracting the average value M or the value of the effective pixel of the divided reference region B adjacent to the diagonally upper right of the effective pixel T3 from the added value. For the effective pixel T4 located in the lower right area with respect to the center of the effective area A, the average value M or the effective pixel value of the divided reference area B adjacent to the lower and right sides of the effective pixel T4 is added. Then, the shading amount S at the effective pixel T4 is calculated by subtracting the average value M or the value of the effective pixel of the divided reference region B adjacent to the lower left of the effective pixel T4 from the added value.

As described above, the shading amount is calculated for each effective pixel in the use effective region A by calculating the shading amount from the effective pixel farthest from the center of the use effective region A. For example, the effective pixel Z23 in FIG. 13 is a pixel located in the center in the horizontal direction of the use effective area A. In the present embodiment, the effective value Z13 above the effective pixel Z23 and the left effective pixel Z22 are slanted. Although the shading amount is calculated using the upper left average value Z12, the shading amount may be calculated using the average value Z13 above the effective pixel Z23, the right effective pixel Z24, and the diagonally upper right average value Z14. In addition, the shading amount value calculated previously in the surrounding pixels can be used. The pixel located in the center in the vertical direction of the use effective area A can be calculated in the same manner. Further, when the effective pixel is located in the center of the use effective area A, the value of the shading amount calculated in any of the surrounding pixels may be used or may be appropriately selected.

Next, an example of the correction value of the shading correction calculated by the above-described shading amount calculation method will be described. If the average values Z11 to Z55 of the pixel signals of the reference pixels in the divided reference areas B11 to B55 calculated in step S21 of FIG. 9 are substituted into the expression shown in the effective area A of FIG. The shading amount shown in FIG. 14 is calculated for each effective pixel in the region A.

Then, the signal correction unit 61 calculates the value of the shading amount calculated for each effective pixel from each of the pixel signal values of the effective pixels in the use effective area A, and shades the pixel signal value. to correct. As shown in FIG. 14, the value of the shading amount calculated for each pixel may include a positive value and a negative value. When the shading amount is a negative value, the absolute value of the shading amount is added to the value of the pixel signal of the effective pixel in the use effective area A. When the shading amount is positive In this case, the value of the shading amount is subtracted from the value of the pixel signal of the effective pixel in the use effective area A.

As shown in FIG. 12, shading correction is performed using average values M11 to M55 of pixel signal values of reference pixels in 16 divided reference regions B11 to B55 provided in a frame shape at the edge of the detection region C. When performing, since the shading amount S in the vertical direction and the horizontal direction of the infrared image due to the temperature difference around the infrared imaging device main body 12 can be acquired in detail, the unevenness of the entire infrared image can be accurately corrected.

Also in the second correction method, as in the first correction method described above, the optical axis O of the imaging optical system 2 and the center 31o of the detection region 31 of the infrared sensor 3 are made to coincide with each other, and the centers O and 31o are set. By making the length of the region C of the detection region 31 larger than the length of the imaging region D of the imaging optical system 2 on the straight line d in one direction passing therethrough, the detection region 31 in the detection region 31 of the infrared sensor 3 is obtained. An effective area AR in which the imaging area D overlaps with the imaging area D and a reference area BR in which the imaging area D does not overlap with the effective area AR of the detection area 31 are provided. Even if not, the effective area AR in which infrared rays enter and the reference area BR in which infrared rays do not enter can be formed in the detection area 31. Thereby, since the additional component for avoiding incidence | injection of infrared rays is unnecessary, the infrared sensor 3 can be manufactured simply and at low cost. In addition, the amount of infrared radiation incident on each of the effective area AR and the reference area BR is not affected by the temperature difference between the infrared imaging apparatus main body 12 and a further component for avoiding the incidence of infrared radiation. The fluctuation of the signal value can be accurately corrected.

In the present embodiment, the above-described interpolation method is used to calculate the shading amount S. However, the present invention is not limited to this, and a known method such as linear interpolation or nonlinear interpolation can be used. .

Next, an infrared imaging device according to a second embodiment of the present invention will be described. FIG. 15 is a schematic cross-sectional view illustrating the configuration of the infrared imaging device according to the second embodiment of the present invention. Note that the infrared imaging apparatus of the second embodiment has a configuration in which a temperature sensor described later is provided in the infrared imaging apparatus 1 of the above-described embodiment, and therefore, the description of the configuration of FIG. Hereinafter, only the temperature sensor 13 and the correction method using the output signal from the temperature sensor 13 by the signal correction unit 61 will be described in detail.

In the infrared imaging device main body 12 of the present embodiment, a temperature sensor 13 is provided at a position facing the imaging optical system 2 in the first main body portion 10. As the temperature sensor 13, a known one such as a thermistor, a thermocouple, or a resistance temperature detector can be used. The output signal from the temperature sensor 13 is sent to the signal correction unit 61 by wired or wireless communication (not shown).

Next, a correction method by the signal correction unit 61 of the infrared imaging device of the present embodiment will be described with reference to a flowchart. FIG. 16 is a flowchart of the third correction process of the signal correction unit 61. Note that a series of processing of the infrared imaging apparatus of the present embodiment is the same as the processing of the flowchart of FIG. 7 of the above-described embodiment, and thus description thereof is omitted here, and only correction processing by the signal correction unit 61 is described. To do. In FIG. 16, the same processing as in FIG. 8 is denoted by the same step number, and detailed description thereof is omitted.

As shown in FIG. 16, the signal correction unit 61 calculates the average value M of the pixel signal values of the reference pixels that are the pixels in the reference region B in step S11, and in the use effective region A in step S12. Offset correction is performed by subtracting the average value M from the value of the pixel signal of the effective pixel.

Next, the signal correction unit 61 detects an output signal from the temperature sensor 13 and calculates a value corresponding to the detected value of the output signal (step S13). FIG. 17 shows a relationship between the value of the output signal from the temperature sensor 13 and the calculated value corresponding to this value.

The calculation value corresponding to the value of the output signal from the temperature sensor 13 is set in advance for each type of the infrared imaging device 1, and corresponds to the value of the output signal from the temperature sensor 13, for example, as shown in FIG. A table of calculation values is stored in the storage unit 7. In this table, the amount of infrared rays radiated for each temperature of the infrared imaging device body 12 is detected, and a value based on the amount of infrared rays is set as a calculation value. Specifically, for example, in a state where the infrared imaging device 1 is placed in a constant temperature bath and the temperature of the infrared imaging device 1 is set to be constant, a reference heat source whose absolute temperature is known is photographed by the infrared imaging device 1, and the infrared imaging device The calculated value of FIG. 17 is calculated from the difference between the temperature data of 1 and the temperature of the reference heat source. This table is set in advance at the design stage or manufacturing stage of the infrared imaging device 1. The signal correction unit 61 refers to the table stored in the storage unit 7 to calculate a calculation value corresponding to the value of the output signal from the temperature sensor 13.

Next, the signal correction unit 61 calculates a calculation value corresponding to the value of the output signal of the temperature sensor 13 calculated in step S13 to the value after the offset correction in step S12, and further performs offset correction (step) S14). In FIG. 17, for example, when the calculated value M4 when the value of the output signal from the temperature sensor 13 is N4 is 0, the infrared image indicated by the value after offset correction is stored in the storage unit 7 in step S12. Is done.

On the other hand, if the values of the calculated values M1 to M3 when the value of the output signal from the temperature sensor 13 is any of N1 to N3 are positive values, the calculated values M1 to M3 are offset in step S12. The value of the pixel signal is further offset-corrected by subtracting from the corrected value. If the value after the calculated value M5 when the value of the output signal from the temperature sensor 13 is any value after N5 is a negative value, the absolute value of the value after the calculated value M5 is obtained in step S12. The value of the pixel signal is further offset corrected by adding to the value after the offset correction.

Generally, infrared rays emitted from the subject and infrared rays emitted from the infrared imaging device main body 12 are incident on the infrared sensor 3. As described above, the value of the output signal from the temperature sensor 13 is a calculated value that is a value based on the amount of infrared rays radiated from the infrared imaging device body 12, and thus is based on the value of the output signal from the temperature sensor 13. By calculating the calculation value, which is a value, to the pixel signal value after offset correction, it is possible to offset the value due to the infrared ray radiated from the infrared imaging device main body 12 out of the infrared rays incident on the infrared sensor 3. Therefore, it is possible to acquire a highly accurate image signal value based on the infrared rays emitted from the camera, and to acquire a highly accurate infrared image based on the absolute temperature of the subject.

Next, a fourth correction method by the signal correction unit 61 of the infrared imaging device of the present embodiment will be described with reference to a flowchart. FIG. 18 is a flowchart of the fourth correction process of the signal correction unit 61. Note that a series of processing of the infrared imaging apparatus of the present embodiment is the same as the processing of the flowchart of FIG. 7 of the above-described embodiment, and thus description thereof is omitted here, and only correction processing by the signal correction unit 61 is described. To do. Also, in FIG. 18, the same processing as in FIG. 9 is indicated by the same step number, and detailed description thereof is omitted.

As shown in FIG. 18, the signal correction unit 61 calculates an average value M of pixel signal values of reference pixels, which are pixels in each reference region B, in step S21, and in the use effective region A in step S22. The shading correction is performed on the value of the pixel signal of the effective pixel.

Next, the signal correction unit 61 detects an output signal from the temperature sensor 13 and calculates a value corresponding to the detected value of the output signal (step S23). Here, since the process of step S23 is the same as the process of step 13 of FIG. 16, description here is abbreviate | omitted.

Next, the signal correction unit 61 performs an offset correction by calculating a calculation value corresponding to the value of the output signal of the temperature sensor 13 calculated in step S23 to the value after the shading correction in step S22 (step S24). ). In FIG. 17, for example, when the calculated value M4 when the value of the output signal from the temperature sensor 13 is N4 is 0, the infrared image indicated by the value after shading correction is stored in the storage unit 7 in step S22. The

On the other hand, if the values of the calculated values M1 to M3 when the value of the output signal from the temperature sensor 13 is any of N1 to N3 are positive values, the calculated values M1 to M3 are shaded in step S22. The value of the pixel signal is offset-corrected by subtracting from the corrected value. If the value after the calculated value M5 when the value of the output signal from the temperature sensor 13 is any value after N5 is a negative value, the absolute value of the value after the calculated value M5 is determined in step S22. The value of the pixel signal is offset corrected by adding to the value after the shading correction.

Generally, infrared rays emitted from the subject and infrared rays emitted from the infrared imaging device main body 12 are incident on the infrared sensor 3. As described above, since the value of the output signal from the temperature sensor 13 is a calculated value that is a value based on the amount of infrared rays radiated from the infrared imaging device body 12, it is based on the value of the output signal from the temperature sensor 13. By calculating the calculated value, which is a value, to the value of the pixel signal after shading correction, it is possible to offset the value due to the infrared rays radiated from the infrared imaging device main body 12 out of the infrared rays incident on the infrared sensor 3. A highly accurate image signal value based on infrared rays emitted from the subject can be acquired, and a highly accurate infrared image based on the absolute temperature of the subject can be acquired.

In the embodiment described above, the temperature sensor 13 is provided at a position facing the imaging optical system 2 in the infrared imaging apparatus main body 12, but the present invention is not limited to this. In the present invention, the temperature sensor 13 may be provided anywhere on the infrared imaging device 12, for example, may be provided on a wall surface constituting the second main body portion 11 inside the infrared imaging device main body 12 of FIG. You may provide in the wall surface which comprises the 1st main-body part 10 and the 2nd main-body part 11 outside the infrared imaging device main body 12, and can change suitably. When the temperature sensor 13 is provided inside the infrared imaging device main body 12, the temperature of the wall located in the space where the infrared sensor 3 is installed is measured, and the temperature of the wall that radiates infrared rays to the infrared sensor 3. Therefore, the correction accuracy can be improved. Further, when the infrared sensor 3 is provided at a position corresponding to the imaging optical system 2 in the infrared imaging apparatus main body 12, the temperature of the wall that emits infrared rays to the infrared sensor 3 can be measured. Further improvement can be achieved. In the present embodiment, one temperature sensor 13 is provided, but a plurality of temperature sensors 13 may be provided at different positions. When a plurality of temperature sensors 13 are provided, the average value of the output signals from each temperature sensor 13 can be used.

According to each embodiment of the present invention, since each effect described above can be suitably obtained with respect to offset fluctuation occurring in a thermal sensor (microbolometer type, SIO diode type, etc.), an infrared sensor that detects far infrared rays However, the present invention is not limited to this, and an infrared sensor that detects mid-infrared rays and near-infrared rays may be used.

Moreover, the infrared imaging device 1 according to each embodiment of the present invention can be suitably applied to a security imaging device, an in-vehicle imaging device, and the like, and may be configured as a single imaging device that captures an infrared image. It may be configured to be incorporated in an imaging system having an infrared image capturing function.

The infrared imaging device of the present invention is not limited to the above embodiment, and can be appropriately changed without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 1 Infrared imaging device 12 Infrared imaging device main body 13 Temperature sensor 2 Imaging optical system 3 Infrared sensor 4 Analog signal processing part 5 A / D conversion part 6 Digital signal processing part 61 Signal correction part 7 Storage part 8 Output part 30 Imaging surface 31 Detection area 31o Center of detection area AR Effective area A Effective use area B Reference area C Detection area O Optical axis

Claims

An imaging optical system for imaging infrared rays;
A pixel signal based on infrared rays incident from the imaging optical system is provided for each pixel, having a detection region located on the imaging surface of the imaging optical system and having a plurality of pixels as thermoelectric conversion elements arranged. Infrared sensors for outputting, respectively, the optical axis of the imaging optical system and the center of the detection area coincide with each other, and the length of the detection area in one direction passing through the center is imaged by the imaging optical system An infrared sensor provided with an effective region in which the detection region and the imaging region overlap within the detection region, and a reference region in which the detection region and the imaging region do not overlap by providing the detection region with a length larger than the length of the region; ,
Variation in the value of the pixel signal due to a temperature change by correcting the value of the pixel signal of the effective pixel that is the pixel in the effective area using the value of the pixel signal of the reference pixel that is the pixel in the reference area An infrared imaging device comprising: a signal correction unit that corrects
The infrared imaging device according to claim 1, wherein the signal correction unit performs offset correction by subtracting an average value of pixel signals of the reference pixels from a value of a pixel signal of the effective pixel.
Two or more reference areas are provided in the detection area,
The signal correction unit subtracts an average value of pixel signals of the reference pixels in at least one of the reference regions of the two or more reference regions from a value of the pixel signal of the effective pixel, and the offset. The infrared imaging device according to claim 2, wherein correction is performed.
The detection area is rectangular, and the reference areas are provided at the four corners of the detection area,
The signal correction unit subtracts, from the pixel signal value of the effective pixel, an average value of pixel signal values of reference pixels in at least one of the reference regions of the four corners, respectively, and the offset The infrared imaging device according to claim 2, wherein correction is performed.
Two or more reference areas are provided in the detection area,
The signal correction unit calculates an average value of pixel signals of the reference pixels in at least two of the reference regions out of the two or more reference regions, and uses the calculated at least two average values, The infrared imaging device according to claim 1, wherein shading correction is performed on a value of a pixel signal of the effective pixel.
The detection area is rectangular, and the reference areas are provided at the four corners of the detection area,
The signal correction unit calculates an average value of pixel signal values of reference pixels in the reference area for at least two of the reference areas in the four corners, and calculates the calculated at least two averages. The infrared imaging device according to claim 5, wherein the shading correction is performed on a value of a pixel signal of the effective pixel using a value.
The reference region is provided at an edge in the detection region, a frame-like reference region portion in which a plurality of the reference pixels are arranged is provided in the reference region, and the frame-like reference region portion is divided into a plurality of regions. And
The signal correction unit calculates, for each of the plurality of regions, an average value of pixel signals of reference pixels located in the plurality of regions, and uses each of the calculated average values to calculate the effective pixel. The infrared imaging apparatus according to claim 1, wherein shading correction is performed on the value of the pixel signal.
Providing at least one temperature sensor in the body of the infrared imaging device;
The infrared signal according to any one of claims 1 to 7, wherein the signal correction unit performs a further offset correction by calculating a value corresponding to a value of an output signal from the temperature sensor to a value of a pixel signal of the effective pixel. Imaging device.
The infrared imaging device according to claim 8, wherein the temperature sensor is provided inside a body of the infrared imaging device.
The infrared imaging device according to claim 9, wherein the temperature sensor is provided at a position facing the imaging optical system.