JPH09189611A - Two-dimensional infrared camera with built-in heat source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regularly and easily perform the offset and gain correction of a two-dimensional infrared sensor without carrying a heat source. SOLUTION: A housing case 24 is connected to a lens-barrel 23 having a two-dimensional infrared sensor 21 and a light receiving optical system 22 arranged therein so as to be easily attachable and detachable. A flat black body 25 as a heat source whose temperature is externally adjustable is arranged in the upper part within the housing case 24, and generally set in a position shown by the solid line so as to shield the black body 25. At correction, it is set in a position shown by the dashed line by a pulse motor so as to catch the infrared ray emitted by the black body 24 by the two-dimensional infrared sensor 21.

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to a heat source built two-dimensional infrared camera, in particular I _n S _b (InSb)
In an infrared thermal imaging device (also called thermography) that measures the temperature distribution of an object with multiple infrared detection elements such as, and generates a thermal image showing the temperature distribution, the characteristics of the infrared detection elements are not uniform. The present invention relates to a two-dimensional infrared camera with a built-in heat source, which enables offset correction and gain correction for compensating for temperature measurement errors caused by the above and ensuring uniformity of a thermal image, without requiring carrying a heat source at all times. .

[0002]

2. Description of the Related Art An object emits infrared rays according to its temperature, and the temperature and the infrared radiation amount correspond to each other in a fixed relationship. Utilizing this relationship, an infrared image emitted from an object is captured and an image showing the temperature distribution of the object is a thermal image. An apparatus for obtaining this thermal image is an infrared thermal imager or a thermographic device. I am calling.

FIG. 5 is a block diagram showing the configuration of a conventional two-dimensional infrared sensor and its output section. The two-dimensional infrared sensor 501 has n arranged in a two-dimensional matrix.
The infrared detection elements d1, d2, d3, ... dn, and the detection outputs 1001 S1, S2, S3, ... Sn obtained by scanning the infrared detection elements d1, d2, d3 ,. The serial signal 200 is converted into a time division signal by the multiplexer 201 driven by the synchronization signal 2001.
It is output as 2. The serial output 2002 of the multiplexer 202 is amplified by the amplifier 301 and amplified output 300
After being set to 1, it is converted into a digital signal 4001 by the A / D converter 401 and provided for thermal image generation.

The conventional two-dimensional infrared sensor 501 described above
Is a plurality of infrared detecting elements d1, d2, d3, ... dn
It is difficult to manufacture the two-dimensional infrared sensor 50 without completely correcting the outputs of these infrared detecting elements so as to eliminate the influence of characteristic variations.
1 causes an error in the measured temperature, and the A / D converter 40
The unevenness of the brightness (temperature) is caused in the thermal image obtained by processing the digital output 4001 of No. 1. Therefore, the offset value based on the nonuniformity of the output of each infrared detection element at a certain constant temperature (usually low temperature) and the difference between the outputs of the infrared detection elements at high and low temperatures, that is, the nonuniformity of the gain (gain ratio) is corrected. It is necessary to perform offset correction and gain correction to ensure the uniformity of the thermal image.

The offset value is a heat source having a constant temperature T1,
For example, receiving infrared rays from a two-dimensional infrared sensor from a blackbody furnace,
The average value of the outputs of all the infrared detecting elements is obtained, and the difference between the output of each infrared detecting element and the average value is obtained. Further, the output of the infrared detecting element at the temperature T2 higher than the above-mentioned temperature T1 for which the offset value is obtained is obtained, and the difference between the output at the temperature T2 and the output at the temperature T1 is obtained as the gain of each infrared detecting element for each infrared detecting element. The ratio of the average gain of all infrared detecting elements and the gain of each infrared detecting element is calculated as a gain ratio. The gain ratio is usually different for each infrared detection element.

By subtracting the offset value from the output of each infrared detection element, so-called zero correction as offset correction can be performed. However, when the offset value is obtained by subtracting the output of each infrared detection element from the above-mentioned average value, the offset correction can be performed by adding the output of each infrared detection element to the offset value.

Further, by multiplying the output of each infrared detecting element by the gain ratio, it is possible to correct the unevenness of the gain of each infrared detecting element. However, when the gain ratio is obtained by dividing the gain of each infrared detection element by the average of the gains of all infrared detection elements, the gain correction can be performed by dividing the output of each infrared detection element by the gain ratio.

FIG. 4 is a schematic diagram showing the output section of the two-dimensional infrared sensor shown in FIG.
A circuit including a / D converter 401) and a correction system including offset correction and gain correction is added. The configuration shown in FIG. 4 is used as a two-dimensional infrared sensor 1, a multiplexer 2, an amplifier 3, an A / D converter 4, an adder 5, a multiplier 6, a peak hold circuit 20 for peak holding an input, and a frame memory for image data. Image memory 8 and offset memory 1 for storing offset value data
1. A gain memory 12 for storing gain ratio data, a sync signal generator 13 for generating a sync signal necessary for operation, a bus 14, and a CPU 1 which incorporates a program and controls the overall operation.
5 and 5. The peak hold circuit 20 also includes a peak selection switch 7 for selecting a peak value, an image memory 9 as a frame memory for image data, and a comparator 10 for comparing the levels of two inputs.

The two-dimensional infrared sensor 1 is formed by arranging infrared detecting elements using I _n S _b in a two-dimensional matrix, for example, 320 elements in the horizontal direction and 2 elements in the vertical direction.
It has 40 elements and has sufficient sensitivity in the temperature range of −40 ° C. to 1,200 ° C. Infrared rays emitted from the object to be measured are incident on the two-dimensional infrared sensor 1 through an optical system,
An infrared image is formed. The multiplexer 2 receives the parallel signal output 101 of the two-dimensional infrared sensor 1 and converts it into a serial signal time-division signal. The amplifier 3 amplifies the voltage of the output 102 of the multiplexer 2. The A / D converter 4 converts the output 103 of the amplifier 3 into a digital signal. The adder 5 adds the output 104 of the A / D converter 4 and the data read from the offset memory 11,
The sum 105 is output. The multiplier 6 multiplies the sum 105 of the outputs of the adder 5 by the data read from the gain memory 12 and outputs the product 106.

The comparator 10 of the peak hold circuit 20 is
The product 106 input to the terminal A is compared with the data 109 input to the terminal B. When the product 106 is greater than or equal to the data 109, the output is set to high level, and otherwise the output is set to low level. Peak selection switch 7
Selects the signal at the terminal a and connects it to the terminal c when the output of the comparator 10 is high level, and selects the signal at the terminal b and connects it to the terminal c when the output of the comparator 10 is low level.

The image memories 8 and 9 are both frame memories and store the output 107 of the peak selection switch 7. The number of pixels stored in each of the image memories 8 and 9 is 32 in the number of infrared detecting elements in the two-dimensional infrared sensor 1.
It has a storage capacity of 0 × 240 or more.

The synchronizing signal generator 13 includes a multiplexer 2
To the offset memory 11,
The sync signal 113b is applied to the gain memory 12 and the image memory 9.
Supply. The multiplexer 2 time-division-processes the output of each infrared detection element included in the two-dimensional infrared sensor 1 at the timing of the synchronization signal 113a, and converts the parallel signal output 101 into the serial signal output 102. Time division signal output 1
Reference numeral 02 denotes an image signal, and 320 × 240 pixels form one frame. Each pixel in the output 102 represents the output of the 320 × 240 infrared detection elements that form the two-dimensional infrared sensor 1.

Offset memory 11 and gain memory 12
The image memory 9 writes and reads data at the timing of the synchronization signal 113b. Sync signal 113a,
By the action of 113b, the addition in the adder 5, the multiplication in the multiplier 6, and the comparison in the comparator 10 are performed for the output of the same infrared detection element, that is, for the same pixel signal.

By the way, the two-dimensional infrared camera shown in FIG.
Usually, it has two operation modes, an operation mode and a correction data acquisition mode. In the normal operation mode, the image signal output 108 with the offset correction and the gain correction is output from the image memory 8. In the correction data acquisition mode, the offset value is stored in the offset memory 11 and the gain ratio is stored in the gain memory 12.

When the two-dimensional infrared camera is operated in the correction data acquisition mode, infrared rays are input to the optical system of the infrared camera from a heat source such as a black body furnace. Such a black body furnace is mounted on an XY table and moved in a plane orthogonal to the optical axis of the optical system to move the black body furnace on all the infrared detecting elements constituting the two-dimensional infrared sensor. The infrared images of are sequentially formed. That is, by moving the black body furnace in a plane orthogonal to the optical axis of the optical system, all the infrared detecting elements can see the entire area of the black body furnace.

The adder 5, the multiplier 6, the offset memory 11, the gain memory 12 and the peak hold circuit 2 shown in FIG.
0 constitutes the correction system A. In the correction data acquisition mode, the correction system A generates an offset value stored in the offset memory 11 and a gain ratio stored in the gain memory 12. The CPU 15 uses the correction system A via the bus 14.
Control. In the correction data acquisition mode, the peak selection switch 7 is controlled by the start signal 114c so that the peak selection switch 7 can select the signal at the terminal a or the signal at the terminal b according to the output of the comparator 10.

Further, in the correction data acquisition mode, the CPU
Reference numeral 15 controls the offset memory 11 and the gain memory 12, causing the offset memory 11 to output the offset value “0” for all pixels, and the gain memory 12 to output the gain ratio “1” for all pixels. That is, in the correction data acquisition mode, the adder 5 and the multiplier 6
Simply passes the input signal and does not correct the image data in the correction data acquisition mode.

Prior to operating the infrared camera in the correction data acquisition mode, the average temperature of the blackbody furnace is set to a temperature T1 lower than the center value of the operating temperature range of the infrared camera. The temperature of the black body furnace is set by the control of the CPU 15. When the infrared camera is activated in the correction data acquisition mode under the control of the CPU 15, first, the contents of the image memories 8 and 9 are all cleared to "0". However, FIG.
In the figure, the signal lines to be set between the bus 14 and the image memories 8 and 9 for controlling the memory clear and the like are not shown.

Next, the image of the first frame input in the correction data acquisition mode is written in the image memory 9. Next, when the image of the second frame is serially input pixel by pixel as a product 106 and input to the peak hold circuit 20, the data of the same pixel already stored in the image memory 9 is compared in magnitude by the comparator 10. Then, the larger data is written in the address of the pixel in the image memory 9. Subsequently, until all regions of the blackbody furnace are seen by all infrared detectors, in other words, all infrared detectors detect infrared radiation emitted from all regions of the blackbody furnace. While performing a parallel movement around the optical axis, the correction system is caused to perform the above-mentioned operation, and the output when each infrared detecting element detects the point of the highest temperature in the blackbody furnace, for each infrared detecting element, that is, Each pixel is stored in the image memory 9.

By the operation of the correction data acquisition mode described above, the image memory 9 stores pixel data when all the infrared detecting elements constituting the two-dimensional infrared sensor 1 detect infrared rays at the highest temperature point in the blackbody furnace. Is stored for all pixels for one frame. Therefore, the image memory 9 stores the same data as when observing a black body furnace having a completely uniform temperature in all regions.

Next, the CPU 15 sets the average temperature of the black body furnace to a temperature T2 which is higher than the center value of the operating temperature range of the infrared camera, and sets the temperature of the black body furnace to T1. Thus, each pixel data at the second temperature T2 is acquired. However, the maximum value data obtained at this time is stored in the image memory 8. By the above operation, when the maximum values of the respective pixels at the average blackbody furnace temperatures T1 and T2 are stored in the image memories 9 and 8, respectively, the CPU 15
Calculate the offset value and gain ratio.

In this calculation, first, the maximum value data S _T1M of each pixel at the low temperature T1 is read from the image memory 9, and the average value S _TIMA of the maximum values S _T1M for all the pixels is calculated,
The maximum value S _T1M of each pixel is subtracted from the average value S _T1MA , and the obtained difference data S _T1MA −S _T1M is written to each pixel address of the offset memory 11 as the offset value d of each pixel.

Next, the maximum value data S at the high temperature T2
_T2M is read from the image memory 8, gain g = S _T2M −S _T1M is calculated for each pixel, the average value g _A of the gain g for all pixels is calculated, and the gain ratio r is calculated for each pixel.
_g = g _A / g is calculated, and the gain ratio r _g is written in each pixel address of the gain memory 12.

By the above operation in the correction data acquisition mode, the offset memory 11 and the gain memory 12 store the correct offset value d and gain ratio r _g for each pixel, respectively. After finishing the correction data acquisition mode,
In the normal mode, the start signal 114c causes the terminal c of the peak selection switch 7 to remain connected to the terminal a and stores the thermal image of the measured object in the image memory 8.

In the above description, in the correction data acquisition mode, the black body furnace was moved in parallel around the optical axis, but conversely, the infrared camera side was moved while keeping the optical axis parallel, and the black body furnace was Even if it is fixed, exactly the same correction data can be obtained.

Further, S _T1MA -S _T1M is set as the offset value d. Conversely, S _T1M -S _T1MA is set as the offset value (d), and a subtracter is used instead of the adder 5, and this subtracter is used. There is no problem even if (d) is subtracted from the output 104 of the A / D converter 4. Furthermore, r _g = g _A / g
Was used as the gain ratio, but conversely, (r _g ) = g / g _A was used as the gain ratio, a divider was used instead of the multiplier 6, and the signal 105 was output from the gain memory 12 (r _g ) by this divider. It does not matter if it is divided by. The offset correction circuit shown in FIG. 4 is provided in order to correct variations in offset value caused by aging of each infrared detection element and the analog circuit of its output.

When manufactured in a factory, infrared rays from a black body furnace are input to an infrared sensor, the offset value of each infrared detecting element and the unevenness of the gain of each infrared detecting element are measured, and the offset value and gain ratio are recorded in a calibration table. Was stored, the offset value was subtracted from the output of each infrared detection element, and the offset corrected signal was multiplied by the gain ratio to obtain the corrected infrared sensor output.

[0028]

However, the thermal image uniformity correction of the above-mentioned conventional two-dimensional infrared sensor has the following problems.
A heat source such as a black body furnace that provides a uniform temperature surface is required. As shown in FIG. 6, a heat source 503 that serves such a purpose is configured to include a black body 5031 that provides a uniform temperature surface for the two-dimensional infrared camera 502. It is extremely inconvenient to carry and the possibility of loss is unavoidable.

Use more than tens of thousands of infrared detecting elements 2
It is necessary to make corrections at least several times a year to smooth the effects of variations in the sensitivity and offset amount of the two-dimensional infrared sensor, and in consideration of the sensitive secular variability of the two-dimensional infrared sensor, always carry a heat source. Inevitably, this has been a major obstacle to the operation of the two-dimensional infrared sensor.

An object of the present invention is to provide a two-dimensional infrared camera with a built-in heat source, which solves the above-mentioned problems and has a built-in heat source necessary for correction for ensuring the uniformity of a thermal image, thereby significantly improving the operability. To do.

[0031]

The present invention has the following means in order to achieve the above object. That is, the first configuration of the present invention relating to a two-dimensional infrared camera with a built-in heat source is
A two-dimensional infrared camera with a built-in heat source, which is capable of always performing offset correction and gain correction for ensuring the uniformity of an acquired thermal image without carrying an independent heat source. Show (a) or (c)
Each configuration is provided. (A) A front open end that is detachably coupled with an inner space that does not spatially obstruct the light receiving optical path for the two-dimensional infrared sensor at the tip of the lens barrel in which the light receiving optical system and the two-dimensional infrared sensor are installed. (B) A flat plate-shaped black as a heat source having a uniform temperature distribution, which is arranged in a position parallel to the optical axis of the light receiving optical path and not spatially obstructing the light receiving optical path on the upper inside of the housing case. Body (c) It is fixed to a fulcrum member arranged in the upper part of the inside of the housing case and in the vicinity of the black body, and is always held parallel to the black body and in a state not spatially obstructing the light receiving optical path. The black body is enclosed and shielded from the housing case, and when the offset correction and the gain correction are performed, the black body is swung downward by about 45 degrees around the central axis of the fulcrum member and the tip is housed in the housing case. State of contact In, the movable mirror allowed to form an optical path between the black body and the two-dimensional infrared sensor

A second structure of the present invention is the same as the first structure, except that the black body can control the temperature from the outside.

A third structure of the present invention is the above-mentioned first or second
In the above configuration, the movable mirror is rotated by an electric method in which the motor of the fulcrum member is rotated.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION A two-dimensional infrared sensor, in which a large number of infrared detecting elements are two-dimensionally arrayed, is provided in a lens barrel together with a light receiving optical system and the like to constitute a two-dimensional infrared camera. Such a two-dimensional infrared camera has a two-dimensional infrared sensor, and the two-dimensional infrared sensor has a plurality of infrared detectors.
This causes uneven brightness in the thermal image. As a countermeasure against this, an offset value and a gain correction for correcting the offset value due to the output irregularity at a certain constant temperature and the gain ratio value indicating the output irregularity at the two high and low temperatures for the all-infrared detecting element are the uniformity of the thermal image. It is necessary to secure.

For this offset correction and gain correction,
A black body as a heat source that provides a uniform temperature distribution surface is required for the two-dimensional infrared sensor, but conventionally, this heat source was carried together with the two-dimensional infrared sensor for correction.

The two-dimensional infrared sensor has a large number of extremely sensitive sensitive elements arrayed therein, and its change over time is great, and it is desirable to always make a correction before use. However, this requires that the heat source is always carried and operated. There is a possibility that it may be lost as well as significantly hindering.

Therefore, in the present invention, a black body as a heat source necessary for offset correction and gain correction is built in a two-dimensional infrared camera, and correction can be easily performed at any time.
In addition, the structure of the heat source built-in two-dimensional infrared camera that does not hinder the normal operation of the two-dimensional infrared camera is used as an embodiment to solve the problem.

[0038]

Next, the present invention will be described with reference to the drawings. 1 is a longitudinal sectional view showing the structure of an embodiment of the present invention, FIG. 2 is a perspective view showing the structure of an embodiment of the present invention, and FIG.
3 is a vertical cross-sectional view showing the structure of the black body in FIG. The configuration of the embodiment shown in FIGS. 1 and 2 serves as a lens barrel 23 of a two-dimensional infrared camera having a two-dimensional infrared sensor 21 and a light receiving optical system 22 therein, and an adapter that is detachably connected to the lens barrel 23. The housing case 24 and a flat plate-shaped black body 25 arranged in parallel with the light receiving axis of the two-dimensional infrared sensor 21 so as not to spatially obstruct the light receiving optical path of the two-dimensional infrared sensor 21 inside the housing case 24. And a movable mirror 26 which is arranged around the central axis of a fulcrum member 261 attached to the upper part inside the housing case 24 and near the black body 25, and a pulse for electrically rotating the movable mirror 26. And a motor 27.

Next, the operation of this embodiment will be described.
The lens barrel 23 and the housing case 24 have a screw structure and are detachably attached to each other by screwing. The other end of the housing case 24 is configured as an open end, and receives infrared rays emitted from an external scene through the open end. In addition, a flat plate-shaped black body 25 is disposed above the inside of the housing case 24 in parallel with the light receiving axis so as not to spatially obstruct the light receiving optical path of the two-dimensional infrared sensor 21.

The movable mirror 26 is held above the inside of the housing case 24 by a fulcrum member 261, and is normally a black body 25.
It is positioned parallel to and shields the black body 25. The movable mirror 26 is set so as not to spatially obstruct the light receiving optical path of the two-dimensional infrared sensor 21 in this state.

At the time of correction, the movable mirror 26 is rotated by the pulse motor 27 by about 45 ° until the tip 262 contacts the lower part of the housing case 24. In this state, the infrared rays emitted from the black body 25 are reflected by the movable mirror 26. Reflected,
It is captured by each infrared detection element of the two-dimensional infrared sensor 21 via the light receiving optical system 22, and enables offset correction and gain correction using the black body 25 as a heat source.

As shown in FIG. 3, the black body 25 includes a flat plate heater 251 as an electric heating member enclosed in a metal case 252, and a black body paint or a black body sheet is applied or adhered on one surface of the metal case. Become. In this embodiment, the black body paint 253 is applied. Such a flat plate-shaped black body 25 is heated by applying power to the flat plate heater 251, and forms a correction heat source by using the coating surface of the black body paint 253 as a uniform temperature distribution surface. Further, in this embodiment, by varying the power source applied to the flat plate heater 251, the temperature as a heat source can be appropriately set to room temperature to 5 to 60 ° C. in this embodiment. In addition, the black body 25 is a couple checker (cou
ple checker) and the like are commercially available.

Thus, in the operating state in which the movable mirror 26 is set parallel to the light receiving axis, the black body 25 is shielded, and the transmission of the input received by the two-dimensional infrared sensor 21 via the light receiving optical system 22 is not hindered. The thermal image can be acquired, and when the pulse motor 27 is opened, only the infrared rays emitted from the black body 25 are received to enable offset correction and gain correction. Offset correction and gain correction per se are shown in FIG.
It is performed by the correction system described above.

As described above, the offset correction and the gain correction can be easily performed at all times prior to the operation, and the quality of the thermal image can be remarkably improved, and the heat source by the black body can be used in the vicinity of the receiving optical system of the two-dimensional infrared camera The constant temperature changes constantly, and the influence of the environmental temperature change can be significantly suppressed.

[0045]

As described above, according to the present invention, a heat source necessary for offset correction and gain correction of a two-dimensional infrared sensor is contained in a housing case that is easily attached to and detached from a two-dimensional infrared camera having a two-dimensional infrared sensor. By disposing a heat source that does not obstruct the received light path and that easily forms an optical path of the heat source for correction, it is possible to easily perform correction prior to thermal image acquisition. The thermal image quality can be remarkably improved, the temperature in the vicinity of the light receiving optical system can be kept constant, and the environmental temperature resistance can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view showing the configuration of an embodiment of the present invention.

FIG. 2 is a perspective view showing the configuration of an embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view showing the configuration of the black body shown in FIGS. 1 and 2.

FIG. 4 is a block diagram showing a configuration of a conventional two-dimensional infrared sensor including a thermal image uniformity correction function and its output section.

FIG. 5 is a block diagram showing a configuration of a conventional two-dimensional infrared sensor and its output section.

FIG. 6 is an explanatory diagram of conventional offset and gain correction by a heat source.

[Explanation of symbols]

 1 2 dimensional infrared sensor 2 multiplexer 3 amplifier 4 A / D converter 5 adder 6 multiplier 7 peak selection switch 8 image memory 9 image memory 10 comparator 11 offset memory 12 gain memory 13 sync signal generator 14 bus 15 CPU 20 peak Hold circuit 21 Two-dimensional infrared sensor 22 Light receiving optical system 23 Lens barrel 24 Housing case 25 Black body 26 Movable mirror 27 Pulse motor

Claims (3)

[Claims] 1. The present invention is characterized by comprising the following respective configurations and enabling constant execution of offset correction and gain correction for ensuring uniformity of an acquired thermal image without carrying an independent heat source. A two-dimensional infrared camera with a built-in heat source. (A) A front open end that is detachably coupled with an internal space that does not spatially obstruct the light receiving optical path for the two-dimensional infrared sensor at the tip of the lens barrel in which the light receiving optical system and the two-dimensional infrared sensor are installed. (B) A flat plate-shaped black as a heat source having a uniform temperature distribution, which is arranged in a position parallel to the optical axis of the light receiving optical path and not spatially obstructing the light receiving optical path on the upper inside of the housing case. Body (c) It is fixed to a fulcrum member arranged in the upper part of the housing case and in the vicinity of the black body, and is always held in parallel with the black body and in a state not spatially obstructing the light receiving optical path. The black body is enclosed and shielded from the housing case, and when the offset correction and the gain correction are performed, the black body is swung downward by about 45 degrees around the central axis of the fulcrum member and the tip is housed in the housing case. State of contact In, the movable mirror allowed to form an optical path between the black body and the two-dimensional infrared sensor 2. The two-dimensional infrared camera with a built-in heat source according to claim 1, wherein the black body has a structure that enables temperature control from the outside. 3. The two-dimensional infrared camera with a built-in heat source according to claim 1, further comprising a structure in which the movable mirror is rotated by an electric system in which a motor of the fulcrum member is rotated.