JPH03246428A - Infrared video device - Google Patents

Abstract

PURPOSE:To eliminate the influence of a change in environmental temp. and the sensitivity of an IR detector, etc. to exactly detect a temp. by providing a heater or cooler which continuously or stepwise changes an IR power and a computing section. CONSTITUTION:A scanning mirror 1 scans a black body 20 for calibration and simultaneously, the black body 20 is successively heated from near the lower limit of the objective temp. range of, for example, the device up to about the upper limit by the heater or cooler 22. The IR power radiated from the black body 20 is changed successively in this way or the radiated IR rays are reflected by the scanning mirror 1 and are condensed by a condenser optical system 4. The condensed light is inputted to the IR detector 5 and is converted to a slight electric signal by photoelectric conversion. The electric signal is then inputted to a computing section 25 through an amplifier 6 and, at the time of this calibration mode, through a switching circuit 24 connected to a terminal 24. The temp. signal of the black body 20 extracted by the temp. sensor 21 is further inputted through the amplifier 23 to the computing section 25. This temp. signal is corresponded to the respective detecting voltages inputted through the circuit 24 and is stored into the RAM in the computing section 25.

Description

[Detailed Description of the Invention] [Summary] Regarding an infrared imaging device that uses a calibration source to perform temperature correction on the detection signal of an infrared detector, the present invention relates to an infrared imaging device that uses a calibration source to perform temperature correction on the detection signal of an infrared detector, and to achieve accuracy by eliminating as much as possible the effects of changes in environmental temperature and sensitivity of the infrared detector. The purpose is to perform accurate temperature detection, and based on the detection signal of infrared rays incident on the infrared detector from the calibration source via the mirror and the condensing optical system, In an infrared imaging device that calibrates an infrared detection signal incident on the infrared detector from a subject, the infrared power variable means continuously or stepwise changes the infrared power emitted from the calibration source; Storing data regarding the detection signal obtained by detecting infrared rays from the calibration source whose power changes sequentially by the power variable means with the infrared detector at predetermined temperature intervals and the temperature of the calibration source at the time of A. a storage means for reading out data from the storage means based on a detection signal of infrared rays from the subject taken out from the infrared detector when the image of the subject is conveyed, and detecting a temperature corresponding to the infrared rays from the subject; and a detection means for performing the detection.

[Industrial application field]

The present invention relates to an infrared imaging device, and more particularly to an infrared imaging device that performs temperature correction on a detection signal of an infrared detector using a calibration source.

[Conventional technology]

FIG. 5 shows a block diagram of an example of a conventional infrared imaging device. In the figure, reference numeral 1 denotes an object plane scanning type scanning mirror, which scans the object to be imaged and also scans the black body 2 for calibration. The scanning angle, scanning period, etc. of the scanning 1t1 are controlled by the scanning control section 3.

The infrared light reflected by the scanning line 1 passes through the condensing optical system 4, is condensed, and enters the infrared detector 5. This infrared detector 5 has one infrared detection element constituting a pixel,
It may be a one-dimensional arrangement of a plurality of infrared detection elements, a near array type, or a two-dimensional arrangement of infrared detection elements in a matrix.

A weak electrical signal obtained by photoelectrically converting the incident infrared light by the infrared detector 5 is amplified to a required level by the amplifier 6 and converted into a detection voltage, and then supplied to the arithmetic unit 7. The calculation section 7 has a memory such as a read-only memory (ROM), and also has a circuit section for digital calculation processing,
Correcting the detection voltage of the N image object based on the detection voltage obtained when scanning the calibration black body 2 with a known temperature, calculates the corresponding temperature value, and further generates a signal indicating the temperature value. is converted into a video signal and supplied to the display unit 8.

The display section 8 is supplied with a sweep signal synchronized with the scanning of the scanning mirror 1 from the synchronization control section 9, and displays a video signal indicating the above-mentioned temperature value on the screen at a position corresponding to the scanning position.

Note that the mechanical structure around the infrared detector 5 is generally constructed as shown in FIG.

In the figure, reference numeral 5a denotes an infrared detector, which corresponds to the infrared detector 5 described above, in which a plurality of infrared detecting elements are arranged one-dimensionally or in a near array type.

This infrared detector 5a is mounted on a cold aperture 11, and its field of view is limited by a cold aperture 12, which is a cooled opening, and these are housed in a vacuum inside a container 13. There is.

Further, in the container 13 in front of the light receiving surface side of the infrared detector 5a, there is a window 1 made of, for example, germanium that transmits infrared rays.
4 is provided, and in front of it, a condenser lens 15, which is the last one of the plurality of lenses constituting the aforementioned condensing optical system 4, is attached to a lens barrel 16 and arranged. There is.

Here, the cold aperture 12 has a rectangular opening 12a according to the shape of the infrared detector 5a, as shown in the plan view of FIG. 7, so that the infrared detector 5a can see the lens surface of the condensing lens 15. .

However, in reality, in order to ensure the field of view of the infrared detecting elements at both ends of the infrared detector 5a, the lens barrel 16 other than the lens surface of the condensing lens 15 must be viewed as shown by the broken line 17 in FIG. It has become. This point applies to infrared ray detectors of other configurations, even if they are not linear array type.

By the way, conventionally, the correction calculation by the calculation unit 7 includes ■-
There are point calibration and ■two-point calibration. - In point calibration, a single calibration black body with a known constant temperature is used as the calibration black body 2, and various reference temperatures and their The characteristics (shown by the curved line in FIG. 8) with respect to the detected voltage at the time are stored in the ROM in the calculation unit 7 as a table. During actual imaging, even if the characteristics of the infrared detection element at the time of object imaging change as shown by the dashed line ■ in Fig. 8, the black body 2 for temperature calibration shown by TO in the same figure is used. By performing a correction calculation based on the detected voltage Vo obtained when taking an appropriate image, it is possible to perform an accurate temperature display obtained with the characteristic indicated by 1 in the figure.

In addition, in the case of two-point calibration, two reference black bodies with different temperatures are prepared as the calibration black body 2, and the temperature T
The detection voltage v1 of the infrared detector 5 when imaging the first calibration black body at +-+ and the detection voltage v2 of the infrared detector 5 when imaging the second calibration black body at temperature T difference (V
The calculation unit 7 calculates a correction coefficient, which is the ratio of the detection voltage VH, VL (7) (VH - VL ) of the first and second calibration black bodies Ill standby stipulations. A correction value is obtained by multiplying the difference value Vo obtained by subtracting the detection voltage v2 from the detection voltage obtained when imaging the subject by the correction coefficient, and then adding the detection voltage V1 to this multiplied value.

As a result, as shown by a in FIG. 9 (Δ) under the environmental temperature, the first. The detection voltage at the time of second calibration blackbody imaging is Va
H, VaL, and the same figure (A) under different environmental temperature.
As shown by b in the figure, even when Vl))I and VbL, the solid line IV in the same figure (B) is obtained by the above-mentioned correction calculation operation.
As shown in , it is possible to obtain the correction values of VH when capturing the first black body image for calibration, and VL when capturing the black body image for second calibration, providing a stable temperature measurement function that is not affected by changes in the environmental temperature. can have

Another method of two-point calibration is to use only one black body 2 for calibration, and to set the infrared detector 5 so that the infrared detector 5 is seen when the scanning mirror 1 is scanned at a specific angle. The operating state of the device is monitored from two signals: the zero level signal corresponding to the extremely low temperature obtained at this time, and the detection voltage when imaging the calibration blackbody 2. Methods for doing so have also been known.

[Problem to be solved by the invention]

However, when the environmental temperature of the device changes, the temperature of the lens barrel 16 shown in FIG.
The infrared power (DC component) incident on (5a) as background light changes.

Since the relationship between infrared power and detection voltage has a nonlinear characteristic as shown in FIG. 10, the incident infrared power is P when the environmental temperature of the device is a predetermined value. Even if a detection voltage of VSO is obtained when ,
The obtained detection voltage has an amplitude different from VsO, such as VS1 or VS2, and the temperature versus detection voltage characteristic changes.

In addition, the temperature vs. detection voltage characteristics may also change due to a decrease in the infrared power incident on the infrared detector 5 due to slight changes in the condensing optical system 4, deterioration or sensitivity changes in the infrared detector 5 itself, gain fluctuations in the amplifier 6, etc. It will change.

If the temperature vs. detection voltage characteristic changes, a characteristic with a slope different from the desired standard characteristic will be obtained in the case of the single-point calibration shown in Figure 8, so even if the −-point calibration is performed, the slope shown in the figure is Therefore, accurate temperature detection becomes impossible.

In addition, in the case of the two-point calibration shown in Figure 9, due to the non-linearity of the temperature vs. detected voltage characteristic, even if the two-point calibration is performed, the desired characteristic (<8) as shown by the - dotted chain line V in the figure is not achieved. Only different characteristics can be obtained, and complete correction cannot be made.

Therefore, in order to correct the temperature change of the lens barrel 16 due to the environmental temperature change of the device, for example, the present applicant has previously proposed
Like the infrared R image device proposed in No. 76, M cylinder 16
A temperature sensor is provided inside, and the temperature data of this temperature sensor and the infrared detection voltage corresponding to the temperature fluctuation of the lens barrel 16 are stored in advance as a table in the memory, and the infrared detection voltage and correction value are stored in the memory during actual imaging. It is conceivable that this is performed by an arithmetic and logic operation unit based on the detected voltage (detected voltage read from the memory corresponding to the temperature data at that time) to improve temperature stability.

However, although this proposed device can compensate for the effects of temperature changes in the lens barrel 16, it is possible to compensate for infrared radiation caused by temperature changes in other optical elements of the focusing optical system on the incident side of the focusing lens 15 in FIG. Changes and the effects of the various variable factors mentioned above cannot be corrected.

The present invention has been made in view of the above points, and an object of the present invention is to provide an infrared imaging device that can accurately detect temperature while minimizing the influence of changes in environmental temperature and sensitivity of an infrared detector.

(Means for Solving the Problems) FIG. 1 shows a principle block diagram of the present invention. , an infrared power variable means 105 for continuously or stepwise changing the infrared power emitted from the calibration source 101, a storage means 106, and a detection means 107 are provided.

Here, the storage means 106 stores data regarding a detection signal obtained by detecting infrared rays from the calibration source 101 with the infrared detector 104 at predetermined temperature intervals and the temperature of the calibration source 101 at that time.

Furthermore, the detection means 107 stores data based on the detection signal taken from the infrared detector 104 when imaging the subject.
06 and performs temperature detection processing corresponding to infrared rays from the subject.

[Function] The present invention does not keep the temperature of the calibration source 101 constant under the same conditions as the subject, but varies it continuously or stepwise from near the upper limit to near the lower limit of the temperature range targeted by the device.
The storage means 10 stores data regarding the detection signals obtained at each predetermined temperature interval and the temperature at that time among the detection signals obtained at that time.
6, then start the actual @ image operation.

Therefore, in the present invention, before starting the actual imaging operation, the environmental temperature of the apparatus at that time, changes in infrared radiation due to temperature changes of the optical elements of the condensing optical system 103, and decreases in arriving power due to aging, etc. The detection signal and correct temperature information can be stored in the storage means 106 in a form that includes all deterioration of the infrared detector 104 and the like.

Note that the mirror 102 may be an object plane scanning type scanning mirror or a non-scanning type pointing mirror. Furthermore, if the infrared detector 104 is a multi-element detector, the storage means 106
The data regarding each of the infrared detection elements is stored in .

〔Example〕

FIG. 2 shows a block diagram of one embodiment of the invention.

In the figure, the same components as those in FIGS. 1 and 5 are denoted by the same reference numerals, and their explanations will be omitted. In FIG. 2, reference numeral 20 denotes a calibration blackbody, which corresponds to the calibration source 101 and is a thin plate made of a material with a small heat capacity (such as aluminum) and whose infrared emittance is about 1. The reason why a material with a small heat capacity is used is to enable the temperature of the calibration black body 20 to be easily changed.

One or more temperature sensors 21 are attached to a part of the calibration black body 20, and a heating or cooling device 22 is attached.
It is configured to be heated or cooled by. The heating or cooling device 22 is the infrared power variable means 105 described above.
In order to change the temperature of the calibration black body 20 to near the upper and lower limits of the temperature range targeted by the device,
■ Initially, the calibration black body 20 is kept at a low temperature and heated by a heater etc. at the start of calibration, or ■ Initially, the calibration black body 20 is kept at a high temperature and cooled by an electronic cooler etc. at the start of calibration. It is configured as one of the following.

The temperature change of the calibration black body 20 by the heating or cooling device 22 is performed continuously or stepwise. In the case of continuous temperature changes, it is sufficient to simply set the heating temperature to the maximum (cooling temperature to the minimum), but since the temperature changes moment by moment, the processing speed of the calculation unit 25 needs to be fast. In the case of a stepwise temperature change, the processing speed of the arithmetic unit 25 may be slow because the power of the heater or electronic cooler can be changed at appropriate steps and the processing can be carried out after the temperature has stabilized.

If the temperature on the low temperature side is below O'C, it is necessary to take precautions to prevent frost from forming (for example, placing the calibration black body 20 in a nitrogen gas atmosphere) in order to maintain calibration accuracy. There is.

Further, 23 is an amplifier, 24 is a switch circuit, 25 and 2
6 are arithmetic units, respectively. The switch circuit 24 scans 111
11] The signal from the unit 3 causes the scanning mirror 1 to move to the calibration black body 2.
During the period when 0 is being scanned, the terminal is switched to the terminal 24a side, and during the period when the scanning H1 is scanning the subject, it is switched to the terminal 24b side, and the detected voltage from the amplifier 6 is selectively input to one of the calculation units 25 and 26. do.

The arithmetic unit 25 has a random memory corresponding to the storage means 106.
It has an access memory (RAM), and an A/D converter and RAM that convert the detection voltage from the switch circuit 24 and the temperature signal from the amplifier 23 into digital signals.
It has a data write/read control circuit, etc. Further, the calculation section 26 is a circuit section that performs calculation processing and conversion into a video signal, which corresponds to the detection means 107, and generates a video signal indicating the temperature corresponding to the detected voltage from the switch circuit 24.

In FIG. 2, the parts other than the display section 8 are housed in the same casing 30 shown in FIG. 3. FIG. 3 is a schematic external view of the main part of FIG.
and a window 31 are provided.

The scanning range scanned by the scanning mirror 1 through the window 31 is the field of view 32 where the subject is located.

Next, the operation of this embodiment will be explained. First, scanning mirror 1
scans the calibration black body 20 (calibration mode). At the same time, the calibration black body 20 is heated by the heating or cooling device 22, for example, from near the lower limit to near the upper limit of the temperature range targeted by the apparatus.

As a result, the infrared power emitted from the calibration black body 20 changes sequentially, and the emitted infrared rays are reflected by the scanning mirror 1, condensed by the condensing optical system 4, and incident on the infrared detector 5. After being photoelectrically converted into a weak electric signal, the signal is input to the arithmetic unit 25 through the amplifier 6 and the switch circuit 24 connected to the terminal 24a side in this calibration mode.

The temperature signal of the calibration black body 20 extracted by the temperature sensor 21 is further input to the calculation unit 25 through the amplifier 23, and the temperature signal and the detection voltage input through the switch circuit 24 are made to correspond to each other. , stored in the RAM in the calculation unit 25.

That is, based on the temperature signal obtained by accurately measuring the temperature of the calibration black body 20 with the temperature sensor 21, the calculation unit 25 calculates
A predetermined number of detected voltages are sampled at an appropriate temperature interval Δt, and a functional equation (quadratic to quartic equation) connecting the information (cutting point) consisting of the sampled detected voltage and the temperature at that time is calculated. The value of each coefficient and each cut point of the functional formula are stored in RAM.

For example, the above cut points are d+, d2°d3 in Figure 4.
As shown by and d4, the set of temperature and detection voltage is (T+,
V+ >, (T2.V2), (T3.V3) and U
(T4, V4), the calculation unit 25 connects these cut points d1 to d4 with a fourth cut point.
A functional formula for the curve shown by ■ in the figure is calculated, and the values of each coefficient of the functional formula and information on the cut points d1 to d4 are stored in the RAM.

Next, the scanning mirror 1 scans the subject (imaging mode). As a result, the infrared rays from the subject 1 are incident on the infrared detector 5 through the scanning mirror 1 and condensing optical system 4 shown in FIG. Accordingly, the electric signal extracted from the infrared detector 5 is inputted as a detection voltage to the arithmetic unit 26 through the amplifier 6. During this imaging mode, the switch circuit 24 is connected to the terminal 24b.

The calculation unit 26 reads out the values of each coefficient of the above-mentioned function formula from the RAM in the calculation unit 25, thereby reproducing the function formula,
After substituting the detected voltage of the object at this time into the functional equation and calculating the corresponding temperature, it is converted into a video signal that can be displayed on the display unit 8.

Therefore, according to this embodiment, even if the infrared detector 5 is influenced by the environmental temperature of the device because it looks into the lens barrel as shown in FIG. 6, the calibration is performed in a manner that includes the environmental temperature. Since the infrared rays from the black body 20 are detected and the accurate temperature at that time is detected by the temperature sensor 2, it is possible to have an accurate temperature measuring function. Moreover, the detection voltage input to the calculation unit 25 during the calibration mode is due to a decrease in the arriving power due to aging of the condensing optical system 4, a deterioration in the sensitivity of the infrared detector 5, and a temperature change of the optical elements of the condensing optical system 4. Since this information currently includes all the various temperature-versus-detection voltage fluctuation factors such as changes in infrared radiation and gain fluctuations of the amplifier 6, the detection output of the arithmetic unit 26 in the imaging mode is not affected by these factors. .

In addition, when the infrared detector 5 is a linear array 41 or a two-dimensional array type multi-element detector in which a large number of infrared detection elements are arranged in a matrix, the above-mentioned procedure is performed separately for each infrared detection element. RAM of cut points and values of each coefficient of the function equation
memory is carried out.

This is because there are variations in sensitivity among each infrared sensing element.

Note that the present invention is not limited to the above-mentioned embodiments; for example, the calculation unit 25 (1) reduces the temperature interval Δt to such an extent that linear approximation holds, and stores only each cut point obtained thereby in the RAM. It may be stored, or it may be determined by calculating in advance a correspondence table between a large number of detected voltages and temperatures from each cut point information,
The correspondence table may be stored in the RAM as a table.

In the case of ■, the calculation unit 26 reads out a detection voltage close to the input detection voltage in the imaging mode from the RAM in the calculation unit 25 and calculates temperature information by calculation using a linear approximation formula. Furthermore, in the case of (2), the temperature corresponding to the input detection voltage in the imaging mode can be immediately obtained from the table without calculation.

Furthermore, although the scanning mirror 1 has been described as an object plane scanning type scanning mirror, the present invention is a non-scanning type scanning mirror using a CCD system, which is equipped with a pointing mirror for changing the direction of the field of view instead of the scanning mirror 1. It can also be applied to infrared imaging devices.

This non-scanning infrared imaging device is mounted on an artificial satellite or an aircraft, and since scanning can be performed by moving the entire device in a predetermined direction, there is no need to use a mirror for scanning. However, in the calibration mode and @image mode, it is necessary to switch the field of view using a pointing mirror.

〔Effect of the invention〕

As described above, according to the present invention, various changes in temperature vs. detection voltage characteristics, such as changes in infrared radiation due to changes in the environmental temperature of the device, changes in the temperature of the optical elements of the condensing optical system, and deterioration of each element due to aging, can be avoided. Since data regarding the detected voltage including the factors and the accurate temperature at that time is stored in the calibration mode, it is possible to obtain accurate temperature information that is almost unaffected by the above fluctuation factors in the imaging mode. , it has features such as being able to significantly improve the reliability of infrared imaging devices.

[Brief explanation of drawings]

Fig. 1 is a diagram of the principle configuration of the present invention, Fig. 2 is a block diagram of an embodiment of the invention, Fig. 3 is a schematic external view of an embodiment of the main part of the invention, and Fig. 4 is a diagram of the embodiment of the invention. A characteristic diagram for explaining the main parts of one embodiment. Fig. 5 is a block diagram of a conventional example. Fig. 6 is a configuration diagram of an example of the main parts of an infrared imaging device. Fig. 7 is a linear array type infrared detector and a cold aperture. Figure 8 is a characteristic diagram based on one-point calibration. Figure 9 is a characteristic diagram based on two-point calibration. Figure 10 is a diagram showing the relationship between infrared power and detection voltage when environmental temperature changes. It is a diagram. In the figure, 4. 103 is a condensing optical system, 5 and 104 are infrared detectors, 20 is a black body for calibration, 21 is a temperature sensor, 22 is a heating or cooling device, 24 is a switch circuit, 25.26 is a calculation unit, 101 is a calibration source , 102 is a mirror 105 is an infrared power variable means, 106 is a storage means, and 107 is a detection means. Detection voltageCharacteristics diagram for explaining the main parts of an embodiment of the present invention Fig.7 A configuration diagram of an example of the main parts of an infrared imaging device Fig.7 A diagram showing the positional relationship between the X-direction nonia array type infrared detector and the cold aperture Characteristic explanatory diagram based on detection voltage point calibration 1 Section 8 Diagram showing the relationship between detection voltage υ and detection voltage Figure 10 Detection voltage V Detection voltage V Characteristic explanatory diagram based on two-point calibration 1

Claims (4)

[Claims] (1) Based on the detection signal of infrared rays incident on the infrared detector (104) from the calibration source (101) via the mirror (102) and the condensing optical system (103), then the mirror (102) and an infrared imaging device that calibrates an infrared detection signal that is incident on the infrared detector (104) from a subject via the condensing optical system (103), the infrared power emitted from the calibration source (101). Infrared power variable means (1
05), and a detection signal obtained by detecting infrared rays from the calibration source (101) whose power changes sequentially by the infrared power variable means (105) with the infrared detector (104) at predetermined temperature intervals. a storage means (106) for storing data regarding the temperature of the calibration source (101) at that time; and a storage means (106) for storing data regarding the temperature of the calibration source (101) at that time; An infrared imaging device comprising: a detection means (107) that reads data from a storage means (106) and performs temperature detection processing corresponding to infrared rays from the subject. (2) The infrared detector (104) is a multi-element detector in which a plurality of infrared detection elements are arranged, and the storage means (104) is a multi-element detector in which a plurality of infrared detection elements are arranged.
2. The infrared imaging device according to claim 1, wherein the infrared imaging device (06) stores the data for each of the plurality of infrared detection elements. (3) The infrared imaging device according to claim 1, wherein the mirror (102) is an object plane scanning type scanning mirror. (4) The infrared rays according to claim 1, wherein the mirror (102) is a pointing mirror whose field of view is set to only one of the calibration source (101) and the subject and does not scan the subject. Video equipment.