JPS6040229B2 - infrared imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a parallel scanning infrared imaging device using an array of infrared detectors arranged in a direction perpendicular to a scanning direction.

FIG. 1 is a diagram showing the configuration of a parallel scanning type infrared imaging device using a conventional one-dimensional scanner.

In the figure, incident infrared light 1 is focused by a light-receiving optical system 2, then scanned by a horizontal scanner 3 that scans in a direction perpendicular to the direction of the infrared detector array 2, and enters the infrared detector array 5. The electrical signal obtained as the output of the infrared detector array 5 is processed by a signal processing circuit 6 and supplied to an image display 8 as a video signal 7. In order to display the imaged scene on the image display 8, the incident infrared light 1 is placed at a position corresponding to the angle of incidence on the light receiving optical system 2, that is, the angle at which the scanner is facing, in accordance with the magnitude of the video signal 7. A method of generating spots of brightness is used. The orientation of the scanner is transmitted as a synchronization signal 9 from the scanner to the signal processing circuit 6 in the form of an electrical signal, and the video signal 7 also includes this information.
FIG. 2 is a diagram showing a parallel scanning method.

Each detector in the infrared detector array 5 is arranged in a direction perpendicular to the scanning direction 10, and the field of view 11 is scanned by a horizontal scanner with a number of scanning lines equal to the number of detectors. The output of each detector is amplified by an amplifier 12 provided for each detector, and then converted into a serial video signal 7 by a multiplexer 13 and supplied to an image display 8.

Note that the amplifier 12 and multiplexer 13 are included in the signal processing circuit 6 in the device shown in FIG. By the way, focusing on two detectors in the infrared detector array, let the sensitivity and power of the first detector be R1 and P1, respectively, and the sensitivity and power of the second detector be R2 and P2, respectively. The outputs SI and S2 of the first detector and the second detector can be respectively expressed by the following equations. SI=RIPI
...mS2FR2P2
...{21 The brightness difference ΔB between the images displayed on the image display is expressed as follows using the gain G of the amplifier provided for each detector and the constant K determined by the image display.

ΔB=KGSI−KGS2=KG{P1(RI−R2)×(PI−P2)R2}.
... [3' It is preferable that the brightness difference ΔB of the image displayed on the image display device is determined only by the difference in the received light power, and the second term in the equation t3} represents this effect.

On the other hand, the first term represents the brightness difference caused by the difference in sensitivity between the detectors. The first term can be ignored compared to the second term: IR payment 2zem;F2! ...When the critical condition is met, for an object at room temperature, IPI - P2l <<PI, so the difference in sensitivity between each detector must be limited to an extremely small value.

However, with the current manufacturing technology of infrared detectors, it is difficult to satisfy the condition of formula 4' for many detectors. Therefore, in the displayed image of the conventional device, horizontal stripe-like brightness unevenness occurs due to uneven sensitivity of the detector. In order to eliminate such drawbacks, the present invention makes infrared light enter the infrared detector array from a reference infrared light source, and uses the infrared detector output at that time to generate an amplifier provided for each detector. The circuit is provided with a circuit for correcting the gain of the circuit, and will be described in detail with reference to the drawings below.

FIG. 3 is a diagram showing an embodiment of the invention.

In the figure, the infrared light incident on the infrared detector array 5 is the incident infrared light 1 incident from the outside or the infrared light generated from the reticle 14 provided on the imaging plane in the light receiving optical system 2. Which of these is incident is determined by the infrared detector array 5.
It is determined by the orientation of the horizontal scanner 3 which scans in a direction perpendicular to the direction of . Immediately before the incident infrared light 1 starts to enter the infrared detector array 5 due to the rotation of the horizontal scanner 3, a horizontal '<
2, whose edge is perpendicular to the scanning direction of the scanner 3;
The book is provided with parallel thread-like patterns with different amounts of infrared radiation. These two slit-like patterns should be set at different temperatures, or
This can be achieved by applying processing with different infrared emissivities. The gain correction signal processing circuit 15 detects the difference in sensitivity between each detector in the infrared detector array 5 based on the output of the gain control amplifier 16 corresponding to the two slit-shaped patterns on the surface of the reticle 14. do. The timing at which the infrared detector array 5 views the slit-like pattern is transmitted to the gain correction signal processing circuit 15 by a synchronization signal 9. The gain control amplifier 16 is an amplifier whose gain is variable according to an external signal, and the gain correction signal processing circuit 15 applies a gain control signal to each gain control amplifier 16 based on the previously detected sensitivity difference between each detector. 17 so that the product of the sensitivity of each detector and the gain of the gain control amplifier 16 connected to that detector is constant for all detectors in the infrared detector array 5.
Furthermore, the gain correction signal processing circuit 15 includes a multiplexer therein, and converts the signals sent in parallel from each detector through the gain control amplifier 16 into a serial format, and sends the signals to the image display 8 as a multiplexed video signal 26. supply FIG. 4 is a diagram showing the relationship between the image of the pattern on the reticle and the field of view required by the imaging device in the infrared imaging device according to the present invention.

Each detector in the infrared detector array 5 is scanned in one direction in the scanning direction by the scanner, but just before scanning the field of view 11, two slit-like patterns, namely the first slit 19 and the second slit 20, on the reticle are scanned. scan. Figure 5 shows
FIG. 3 is a diagram illustrating a configuration example of a gain correction signal processing circuit.

The digital memory 21 is for digitizing and storing the contents of the gain control signal 17 supplied to the gain control amplifier. The multiplex circuit 22 selects one of the many detectors based on a detector designation signal 24 given from a detector designation circuit 23 that designates detectors one after another, and sets the gain corresponding to that detector. The control amplifier output 25 is output as a multiplexed video signal 26. The voltage correction circuit 27 has the product of the sensitivity of the detector designated by the detector designation circuit 23 and the gain of the gain control amplifier corresponding to that detector set in advance based on the multiplexed video signal 26 and the synchronization signal 9. If the value differs from the current value, the difference is detected, the memo IJ contents 28 in the digital memory 21 are modified, and the memo IJ contents 28 are sent back to the digital memory 21 together with a write signal 29 as the write contents 30. Note that the write signal is a signal for putting the digital memory 21 into a write state, and the storage contents of the digital memory 21 do not change during a period when this signal is not applied. The sample-and-hold signal 31 causes a sample-and-hold circuit 32 corresponding to the detector designated by the detector designating circuit 23 to sample and hold the contents of the digital memory 21 that have been converted into an analog quantity by the digital-to-analog converter 33. It is generated by the detector designation circuit 23 for this purpose. Furthermore, after passing through a low-pass filter 34 provided to stabilize the output of the sample-and-hold circuit 32,
The output of the sample and hold circuit 32 is the gain control signal 17
becomes. FIG. 6 is a diagram showing an example of the configuration of the voltage correction circuit.

The multiplexed video signal 26 is supplied to two sample-and-hold circuits 36a and 36b after passing through a low-pass filter 35 provided to reduce noise. Based on the synchronization signal 9, the synchronization signal separation circuit 37 detects the first slit when the infrared detector array is looking at the first slit depending on the orientation of the scanner.
The slit synchronization signal 38, . A second slit synchronization signal 39 is generated while viewing the second slit. The two sample and hold circuits 36a and 36b sample and hold the multiplexed video signal 26 based on the first slit synchronization signal 38 and the second slit synchronization signal 39, respectively, and the output thereof is at the first slit level 40 and the second slit level 40. The 2-slit level becomes 41.

The difference between the first slit level 40 and the second slit level 41 is determined by the product of the sensitivity of the detector in the infrared detector array and the gain of each gain control amplifier corresponding to that detector. If the products of are the same, this difference will also be constant. The subtracter 42a determines the difference between the first slit level 40 and the second slit level 41, and the difference between this difference and a predetermined reference value 43 is determined again by the subtractor 42b, and becomes an error signal 44. After this error signal 44 passes through a coefficient multiplier 45 having a predetermined attenuation coefficient, it is applied to an analog-to-digital converter 46 and becomes a digitized error signal 47. Digital adder 48 adds memory contents 28 and digitized error signal 47 to generate write contents 30. Further, the discriminator 49 generates a write signal 29 for correcting the contents of the digital memory when the absolute value of the digitized error signal 47 exceeds a certain value. FIG. 7 is a diagram showing the phase relationship of the main signals in the voltage correction circuit, including the multiplexed video signal 26, the first slit synchronization signal 38, the second slit synchronization signal 39, the first slit level 40, the second slit level 41. shows the relationship between Note that the above explanation has been about the case where a one-dimensional scanner is used as the scanner, but the same effect can be obtained by using the same method as above when using a two-dimensional scanner that combines scanners that scan in mutually orthogonal directions instead. is obtained.

Furthermore, in the above explanation, a preset value was used as a reference value for comparison with the difference between the first slit level and the second slit level, but instead of this, the first slit level and the second slit level in all detectors are By determining the difference between the two and using this average value as a reference value, it is possible to reduce the dynamic range of the error signal. As described above, in the infrared imaging device according to the present invention, by having a circuit that automatically corrects sensitivity differences between a plurality of infrared detectors,
A highly uniform infrared image can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a parallel scanning type infrared imaging device using a conventional one-dimensional scanner, FIG. 2 is a diagram showing a parallel scanning type, and FIG. 3 is a diagram showing an embodiment of the present invention. 4 is a diagram showing the relationship between the image of the pattern on the reticle and the field of view required by the bran imaging device in the infrared imaging device according to the present invention, FIG. 5 is a diagram showing an example of the configuration of the gain correction signal processing circuit, and FIG. The figure shows an example of the configuration of a voltage correction circuit.
FIG. 7 is a diagram showing the phase relationship of the main signals in the voltage correction circuit. 20 is a second slit, 23 is a detector designation circuit, and 27 is a voltage correction circuit. It should be noted that the same or corresponding parts in the figures are indicated by the same reference numerals. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. An infrared imaging device having an infrared detector array arranged linearly in a direction perpendicular to the scanning direction and a light receiving optical system, and a scanner that two-dimensionally or one-dimensionally scans the field of view seen by the infrared detector array. , on the imaging plane in the light receiving optical system, within the range scanned by the scanner, and in a position that does not obstruct the field of view of the scene required by the infrared imaging device, in the same direction as the infrared detector row. A reticle with two parallel long sides having slit-like patterns with different amounts of infrared radiation is provided, and a reticle is provided for each detector in the infrared detector array corresponding to the image of each slit in the reticle. An infrared imaging device characterized in that the gain of each amplifier is automatically controlled so that the difference in signals generated by the provided amplifiers has the same value for all detectors.