JPH09325078A - Room temperature clamping level correction method for inferred ray picture device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase stability in picture generation in a room temperature clamping level correction method for an inferred ray picture device in which both processes of analogue offset and digital offset are used. SOLUTION: The output from an input part 2 is, at an analogue offset circuit 3, applied with an analogue offset of rough adjustment by the first offset signal (c). A digital offset circuit 5, with the second offset signal (d), applies a digital offset of fine adjustment, for sending a digital inferred ray sensor output. A room temperature sensor 1 and a room temperature data detector 6, respectively, obtain a temperature data at in-device assignment places of the room temperature sensor 1, and supply them to a CPU 7. The CPU 7 performs, only when the relative deviation of two room temperature data exceeds a specified allowable range, a room temperature clamp level correction in step-by-step manner in a specified processing unit, for eliminating too-sensitive correction for securing stable picture generation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a room temperature clamp level correction system for an infrared imager, and more particularly, a clamp level as a reference DC level to be set in a signal acquired by the infrared imager is fixed in accordance with room temperature fluctuations. The present invention relates to a room temperature clamp level correction method for an infrared imaging device that is held in a room.

[0002]

2. Description of the Related Art When a thermal image of an object is generated by an infrared imaging device, a room temperature sensor is usually arranged at a predetermined position inside the device, and its acquisition temperature in a substantially saturated operating environment temperature is used as a reference temperature. To use. In this case, the difference between the maximum temperature level and the minimum temperature level detected by the infrared sensor is constant, but the reference temperature corresponding to room temperature varies depending on the operating environment. A so-called room temperature clamp level correction, which handles the detected temperature as an upper zero, is applied to the detected temperature so that the clamp level is always constant corresponding to room temperature.

FIG. 4 is a block diagram showing the structure of a room temperature clamp level correction system of a conventional infrared imager. The infrared sensor signal amplified by the amplifier 121 of the input unit 12 is subjected to DC regeneration in the DC regenerator 122 in which the level is fixed at a constant DC potential regardless of the magnitude of the input amplitude. The output signal of the input unit 12 is supplied to the analog offset circuit 13, and the potential when the infrared sensor in the same device scans the room temperature sensor 11 is held at a reference DC level as a value predetermined corresponding to room temperature. Is corrected by the analog voltage provided from the DA converter 18.

However, in the above correction, when the accuracy (the number of bits) of the actual DA converter 18 is rough, the residual error corresponding to the minimum digit may not be negligible.

Therefore, a digital offset circuit 15 is added next to the A / D converter 14, and a digital correction signal from the CPU 17 is fed back to this to enable fine correction up to the minimum bit of the infrared imager. .

In order to realize such correction, the room temperature data detector 16 detects a signal corresponding to the room temperature from the digital infrared sensor signal, and the CPU 17 sets the base value b as the base value b.
To supply. The CPU 17 switches the correction procedure according to the magnitude of the relative deviation between the actual room temperature a and the base value b indicating the room temperature data included in the digital infrared sensor signal and the change thereof based on the offset processing logic by the program stored in advance, Feedback correction is performed on the analog offset circuit 13 of the analog system and the digital offset circuit 15 of the digital system.

By such feedback correction,
A large error based on the relative deviation is an analog offset system, and a small error left by the correction of the analog offset system is corrected by the feedback to the digital offset system to realize the room temperature clamp level correction method of the infrared imager that can accurately measure the temperature. are doing.

As described above, conventionally, the relative deviation between the room temperature a and the base value b is controlled by the coarse adjustment by the analog offset system and the fine adjustment of the remaining amount under the control of the built-in program of the CPU 17. The room temperature clamp level was corrected in such a manner that it was corrected to zero. In this case, as the base value b in the processing of the CPU 17, average data for every predetermined several samples of the digital infrared sensor signal to be output is used in consideration of the smoothing of the data.

[0009]

In the conventional room temperature clamp level correction method for the infrared imager described above, the large deviation of the relative deviation between the room temperature a and the base value b is corrected by the coarse adjustment by the analog offset system. The correction of the residual deviation in the correction of the analog offset system is performed as a fine adjustment in the digital offset system.

As described above, when the fine adjustment is performed by the digital offset system, since the correction is performed so that the room temperature = the base value, the base value to be compared with the room temperature is used as the average value for each past several samples. Even if the change is smoothed, it is immediately responded that the change of the base value with respect to the room temperature occurs due to the change of the noise component included in the acquired image data and the increase of the relative deviation due to the change with time of the room temperature sensor itself. As a result, the correction is executed, which makes it difficult to stabilize the image.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and provide a room temperature clamp level correction system for an infrared imaging device which secures image stability.

[0012]

The present invention has the following means constitution in order to solve the above-mentioned object. That is, in the configuration of the present invention relating to the room temperature clamp level correction method of the infrared imager, the clamp level as the reference DC level set as an input in the infrared imager for imaging the infrared rays emitted by the object is constant corresponding to the room temperature. A room temperature clamp level correction method for an infrared imaging device, characterized in that the room temperature clamp level correction is carried out, which has the following respective configurations (a) to (h). (A) A room temperature sensor that is placed inside the infrared imaging device to measure the room temperature. (B) An amplifier that amplifies the infrared sensor signal input from the infrared sensor of the infrared imaging device, and the output of this amplifier is limited in amplitude. And an input section having a DC regenerator that is fixed to a fixed clamp DC level as the reference DC level. (C) The output of the DC regenerator is received, and the temperature is raised to room temperature based on an analog first offset signal received from the outside. Correspondingly, an analog offset circuit for roughly adjusting the clamp level at an analog level which should be held constant. (D) A / D converter for digitizing the output of the analog offset circuit with a predetermined number of bits. The output of the −D converter is received, and the clamp level de-selection is performed based on the digital second offset signal received from the outside. Digital offset circuit that outputs a digital infrared sensor signal that has been finely adjusted at the digital level (f) Room temperature data from the digital infrared sensor signal output by the digital offset circuit according to scan data near the room temperature sensor acquired by the infrared sensor Room temperature data detector that detects and outputs as a base value (g) Temperature data near the room temperature sensor output as the base value and temperature data acquired by the room temperature sensor are compared at predetermined measurement timings. When the relative deviation is within a predetermined allowable range set in consideration of the fluctuation of the base value, the digital infrared sensor signal output from the digital offset circuit is sent as it is, and the relative deviation is within the predetermined allowable range. A predetermined quantization of the room temperature and the base value only when A CPU for sending the first offset signal and the second offset signal in digital form so that they are made to coincide with each other stepwise, and for controlling the overall operation. DA converter for converting an offset signal into an analog signal and sending it to the analog offset circuit

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The room temperature clamp level correction of an infrared imaging device is carried out by using a room temperature sensor installed inside the infrared imaging device and room temperature data obtained by an infrared sensor of the same device in the vicinity of the room temperature sensor ( Based on the viewpoint that the (base value) should be the same, the coarse adjustment to correct the part with a large relative deviation in the analog offset system so that the offset fluctuation due to the relative deviation between the room temperature and the base value becomes zero. With respect to the relative deviation remaining in the rough adjustment, the CPU performs feedback processing for finely adjusting the correction by the digital offset system to make the relative deviation zero.
Go under the control of.

By such room temperature clamp level correction, room temperature clamp level correction capable of always maintaining the reference DC level for the input infrared sensor signal at a desired constant state against changes in room temperature is ensured, and infrared rays with high accuracy are obtained. It is said that video will be possible.

However, in the conventional room temperature clamp level correction, since the correction is performed so that room temperature = base value, even if the base value to be compared with room temperature is calculated by averaging several samples, noise and room temperature are increased. Since the correction is executed in response to the increase in the relative deviation caused by the change with time of the sensor, there is a problem that the image is difficult to stabilize.

In the present invention, the image formation based on the excessive sensitivity is performed by promptly executing the room temperature = base value processing in such conventional room temperature clamp level correction whenever the relative deviation between the room temperature and the base value occurs. Eliminate instability,
Once stable at room temperature = base value, only when a relative deviation between the room temperature and the base value occurs that exceeds a preset allowable range to give a grace process for starting execution of room temperature clamp level correction, and An embodiment of the present invention is to execute room temperature clamp level correction under the control of a CPU having a program including an offset processing logic that permits execution of room temperature clamp level correction stepwise, and to ensure stability of image generation. I am trying.

In this case, the problem is how to set the allowable range, but in the present invention, ± 5 digits is set as the guard line for the difference between the room temperature and the base value. That is, when the relative deviation is expressed by a predetermined quantization step, room temperature clamp level correction in which room temperature = base value is executed step by step by one digit only when it exceeds 6 steps, that is, when it is ± 6 digits or more, The same digital infrared sensor signal output is permitted for fluctuations within ± 5 digits.

[0018]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. The embodiment shown in FIG. 1 inputs an infrared sensor signal from the vicinity of the room temperature sensor 1 arranged at a proper place inside the infrared ray and the room temperature sensor 1 scanned by an infrared sensor (not shown),
An input section 2 for performing DC reproduction for amplifying and setting a reference DC level, an analog offset circuit 3 for performing coarse adjustment by analog offset processing, and an AD converter 4
A digital offset circuit 5 for fine adjustment by digital offset processing, a room temperature data detector 6 for detecting room temperature data from the digital infrared sensor signal that has been subjected to the offset processing and is output from the digital offset circuit 5, and a predetermined offset A CPU 7 that incorporates a program including processing logic and sends out signals necessary for offset processing of the analog offset circuit 3 and the digital offset circuit 5 based on the relative deviation between the outputs of the room temperature sensor 1 and the room temperature data detector 6; DA converter 8 which converts the output to analog and supplies it to the analog offset circuit 3
With.

Next, the operation of this embodiment will be described.
The infrared sensor signal in the vicinity of the room temperature sensor 1 obtained by the infrared sensor is amplified by the amplifier 21 of the input unit 2, and the DC regenerator 22 sets a reference DC level as a constant DC potential regardless of the magnitude of the signal amplitude. DC reproduction is performed, and the output is supplied to the analog offset circuit 3.

In the analog offset circuit 3, the potential when the infrared sensor scans the vicinity of the room temperature sensor 1 is preset by the first offset signal c provided from the DA converter 8 in correspondence with the room temperature. Reference value D
Coarse adjustment of room temperature clamp level correction for analog offset processing is performed so that the level becomes C level, whereby the relative deviation between the room temperature output by the room temperature sensor 1 and the base value b output by the room temperature data detector 6 is calculated. Most of the correction processing is performed to correct the loss.

The output of the analog offset circuit 3 is then digitized by the A / D converter 4 and supplied to the digital offset circuit 5, where it is digitally offset and then output as a digital infrared sensor signal.

The digital offset circuit 5 is provided from the CPU 7 with a fine adjustment for the residual digitized component of the relative deviation between the room temperature a and the base value b remaining after the coarse adjustment of the room temperature clamp level by the analog offset circuit 3.
Only when the residual digitized component exceeds the predetermined permissible range based on the offset signal d, the process is executed based on the offset processing logic included in the built-in program of the CPU 7.

That is, this fine adjustment is carried out at room temperature a and base value b.
It is performed in accordance with the room temperature clamp level correction executed again under the control of the CPU 7 only when the digital expression value of the relative deviation between and exceeds the predetermined allowable range of the digital expression. The excessive sensitivity of the correction to the occurrence of the relative deviation from b is eliminated to enable stable image generation.

In the present embodiment, the above-mentioned allowable range is set to 5 which is the digital value of the relative deviation between the room temperature a and the base value b.
The digit is set. The number of digits in this allowable range depends on operating conditions of the device, various conditions such as the number of quantization steps set based on desired processing accuracy with respect to the expected maximum relative deviation, and desired image generation stability. It is decided in advance in consideration.

Further, even if the relative deviation exceeds n digits (n = 6, 7, 8, ...) In excess of 5 digits, the CPU 7 does not correct the n digit as it is.
The image is gradually decremented step by step to eliminate the destabilization of the image caused by the sudden relative deviation.

FIG. 2 is a flow chart showing the first half of the offset correction processing logic included in the CPU 7 built-in program corresponding to the processing sequence, and FIG. 3 shows the latter half of the offset correction processing logic included in the CPU 7 built-in program as the processing sequence. It is a figure correspondingly and shown in a flowchart.

The correction processing logic shown in FIG. 3 is a portion directly connected to the main contents of the present invention, and the above-described stepwise correction processing is executed under the control of the CPU 7 which develops the correction processing logic shown in FIGS. To be done.

The correction processing logic shown in FIGS. 2 and 3 is branched into two depending on whether it is in the analog output processing state, [THEN], that is, YE.
In the case of S, the offset correction process of the process flow corresponding to whether the base value is larger or smaller than room temperature is adopted for the analog output.

The analog output state is [ELSE], that is, N.
When it is O, the digital output is in a more stable state,
That is, the CPU 7 determines whether or not it is within the allowable range.
The built-in program determines whether the stable state flag is set or not, and branches into [THEN] and [ELSE], and in the stable state ([THEN]), determines whether the relative deviation is ± 5 digits. Perform processing to

Further, in the non-stable state ([ELSE]), it is shown that processing for further bifurcating depending on the room temperature and the base value to direct the stable state is performed. In this way, it is possible to eliminate excessive sensitivity to the relative deviation between the room temperature and the base value and generate a stable image.

[0031]

As described above, according to the present invention, in the room temperature clamp level correction of the infrared imaging apparatus which uses both the analog offset processing and the digital offset processing, the temperature data by the room temperature sensor arranged inside the apparatus and the apparatus Only when the relative deviation from the base value of the temperature data near the room temperature sensor acquired by the infrared sensor exceeds the predetermined allowable range, the correction to make the relative deviation fall within the allowable range is performed stepwise by the predetermined digit step in the digital offset processing. By carrying out the method, it is possible to generate an image with significantly increased stability.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a room temperature clamp level correction system of an infrared imaging device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a first half of an offset correction processing logic included in a built-in program of a CPU 7 of FIG. 1 in a flowchart corresponding to a processing sequence.

FIG. 3 is a diagram showing a latter half of an offset correction processing logic included in a built-in program of a CPU 7 of FIG. 1 in a flowchart corresponding to a processing sequence.

FIG. 4 is a block diagram showing a configuration of a room temperature clamp level correction method of a conventional infrared imaging device.

[Explanation of symbols]

 1 Room Temperature Sensor 2 Input Section 3 Analog Offset Circuit 4 AD Converter 5 Digital Offset Circuit 6 Room Temperature Data Detector 7 CPU 8 DA Converter 21 Amplifier 22 DC Regenerator

Claims (1)

[Claims] 1. A room temperature clamp level for holding a clamp level as a reference DC level to be set at an input in an infrared imager for imaging infrared rays emitted from an object, which is provided with the following respective configurations and is kept constant corresponding to room temperature. Room temperature clamp level correction method for infrared imagers, which is characterized by performing correction. (A) A room temperature sensor that is placed inside the infrared imaging device to measure the room temperature. (B) An amplifier that amplifies the infrared sensor signal input from the infrared sensor of the infrared imaging device, and the output of this amplifier is limited in amplitude. And an input section having a DC regenerator that is fixed to a fixed clamp DC level as the reference DC level. (C) The output of the DC regenerator is received, and the temperature is raised to room temperature based on an analog first offset signal received from the outside. Correspondingly, an analog offset circuit for roughly adjusting the clamp level at an analog level which should be held constant. (D) A / D converter for digitizing the output of the analog offset circuit with a predetermined number of bits. The output of the −D converter is received, and the clamp level de-selection is performed based on the digital second offset signal received from the outside. Digital offset circuit that outputs a digital infrared sensor signal that has been finely adjusted at the digital level (f) Room temperature data from the digital infrared sensor signal output by the digital offset circuit according to scan data near the room temperature sensor acquired by the infrared sensor Room temperature data detector that detects and outputs as a base value (g) Temperature data near the room temperature sensor output as the base value and temperature data acquired by the room temperature sensor are compared at predetermined measurement timings. When the relative deviation is within a predetermined allowable range set in consideration of the fluctuation of the base value, the digital infrared sensor signal output from the digital offset circuit is sent as it is, and the relative deviation is within the predetermined allowable range. A predetermined quantization of the room temperature and the base value only when A CPU for sending the first offset signal and the second offset signal in digital form so that they are made to coincide with each other stepwise, and for controlling the overall operation. DA converter for converting an offset signal into an analog signal and sending it to the analog offset circuit