KR101438327B1 - Thermal imaging camera for correcting ununiformity according to temperature of infrared detector and method of correcting ununiformity in the same - Google Patents

Abstract

Disclosed are a thermal imaging camera for correcting non-uniformity according to temperature changes in infrared detectors and a method for correcting non-uniformity. The thermal camera comprises: a lens to allow infrared rays of a subject to enter; a shutter; a shutter control unit to close or open the shutter; multiple infrared detectors to detect the infrared rays entered through the lens and the shutter by each pixel; a temperature detecting unit to detect temperatures of the infrared rays; a non-uniformity correction unit to calculate a temperature difference between the temperature detected by the temperature detecting unit at a state of closing the shutter and the temperature detected by the temperature detecting unit at a current time, control the shutter control unit to close the shutter if the calculated temperature difference is more than a certain threshold, and correct non-uniformity to generate non-uniformity correction data; an A/D converter to convert infrared rays detected by the infrared detectors to digital values and generate/output infrared images; and an image correcting unit to correct the converted infrared images by applying the non-uniformity correction data generated by the non-uniformity correction unit. With the above constitutions, a non-uniformity correction cycle can be aperiodically set according to the temperature changes in the infrared detectors, rather than periodically setting the non-uniformity correction cycle, thereby reducing unnecessary non-uniformity correction and increasing lifespan of the shutter.

Description

TECHNICAL FIELD [0001] The present invention relates to a thermal camera for correcting nonuniformity in accordance with a temperature change of an infrared ray detector, and a correction method thereof. [0002]

The present invention relates to a thermal imaging camera, and more particularly, to a thermal imaging camera and its non-uniformity correction method for correcting non-uniformity in accordance with a temperature change of an infrared ray detector.

A thermal imaging camera, also called an infrared camera, is configured to output an image formed by sensing infrared rays. It is very useful for detecting a specific temperature in a dark environment, a fogged place, or the like, since an image is generated by sensing infrared rays emitted by an object, which is not visible light, even in the absence of light.

Typical examples are medical / quarantine areas where the temperature of an immigrant from the airport is monitored remotely to detect high temperature patients, industrial fields where the temperature of a transformer installed on a telephone pole is measured while traveling on the ground or in a vehicle, There is a military / security field that detects and detects enemy or abnormal objects in darkness without light.

The thermal camera has an infrared sensor or an infrared sensor array arranged in the form of an infrared sensor array, and the thermal camera generates an image based on the temperature of the object obtained through the respective infrared detectors.

The infrared rays incident through the optical lens of the thermal camera are directly incident on the infrared ray detectors assigned to the respective pixels. Each infrared ray detector measures the changing resistance value in response to the incident infrared ray energy, And generates an image using this.

However, each of the infrared detectors has inherent physical characteristics. Even if they are fabricated through the same process, variations in the characteristics of actual devices may occur.

1 is a graph showing changes in characteristics of a pixel according to the temperature of an infrared ray detector.

Referring to FIG. 1, each infrared ray detector can know characteristics of the device that change with time. The temperature of each infrared ray detector changes with the passage of time, and an offset (deviation) occurs between the device characteristics according to the temperature change of the infrared ray detector.

Accordingly, in order to detect a precise infrared ray energy and generate a high-quality image, the characteristics of each infrared ray detector must be considered to correct the image. Even if the infrared energy of the same intensity is input due to the intrinsic characteristics of the infrared detector, unevenness or noise are mixed in the image when outputting the electric signals of different sizes without outputting the same electric signals for each of the infrared detectors.

Therefore, a deviation correction is required to allow each infrared ray detector to exhibit the same device characteristics before image capturing.

When the shutter of the thermal camera is closed, the infrared detector can not receive the external energy. At this time, the deviation (offset) of the detection value of each pixel of the infrared detector is obtained and stored in the memory. Then, the offset is used to correct the image.

2 is an illustration of an image in which a shutter is closed and non-uniformity correction is performed.

The image of FIG. 2 is an image obtained by detecting an output value of each pixel, that is, an electric signal, ie, an electric signal, in the closed state of the shutter, and performing signal correction so that the sensed signals become uniform in each pixel. The offset of the electrical signal, that is, the difference between the electrical signals between the pixels, is stored in a table and applied to the infrared image.

FIG. 3 is an exemplary view of an infrared image to which a shutter is opened and a non-uniformly corrected offset is applied.

Fig. 3 shows an infrared image in a state in which non-uniformity correction is applied, and the image is output smoothly and clearly.

Such variations or noises are caused by various reaction characteristics due to changes in the ambient temperature of the internal components of the thermal camera or the thermal camera, and become uneven. Such fixed pattern noise must be corrected by non-uniformity by closing the shutter at intervals of 1 minute, 5 minutes, 10 minutes or the like.

However, when a regular shutter operation is performed every one minute, the period is too frequent, and the life of the shutter can be shortened. Further, since the generation of the image is also stopped during the shutter operation, there is a problem that the motion picture is disconnected too frequently.

In addition, even if the thermal camera is stabilized and no fixed pattern noise is generated, nonuniformity correction may be performed periodically, which may cause unnecessary nonuniformity correction.

Further, during the stabilization of the thermal camera, there is a problem that the image quality deteriorates as the shutter operation becomes longer.

On the other hand, when the period of the shutter is set long, that is, when the non-uniformity correction period is too long, the fixed noise pattern can not be removed and the quality of the image deteriorates.

In general, the shutter operation and the non-uniformity correction are periodically performed by setting the periodic nonuniformity correction of about 1 minute and 2 minutes in the past. However, due to the shutter operation and the nonuniformity correction, There is a problem that shortens the life time. Further, in the stabilized state, unnecessary nonuniformity correction is performed too frequently.

Accordingly, it is necessary to more efficiently operate the cycle of performing the nonuniformity correction operation of the thermal imaging camera.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal imaging camera that corrects for non-uniformity in accordance with a temperature change of an infrared ray detector.

It is another object of the present invention to provide a non-uniformity correction method according to a temperature change of an infrared ray detector.

According to an aspect of the present invention, there is provided a thermal camera for correcting unevenness according to a temperature change of an infrared ray detector, including: a lens through which infrared rays of a subject are incident; A shutter; A shutter control unit for closing or opening the shutter; A plurality of infrared detectors for detecting infrared rays incident through the lens and the shutter for each pixel; An A / D converter for converting an infrared ray detected by the infrared ray detector into a digital value and generating / outputting an infrared ray image; A temperature sensing unit for sensing a temperature of the infrared ray detector; Wherein the controller calculates the temperature difference between the temperature sensed by the temperature sensing unit and the temperature sensed by the temperature sensing unit at the present time when the shutter is closed and if the calculated temperature difference is equal to or greater than the predetermined threshold, A non-uniform correction unit that performs non-uniform correction and controls non-uniformity correction so as to generate non-uniformity correction data; And an image correction unit for correcting the infrared image by applying the non-uniformity correction data generated by the non-uniformity correction unit to the generated / outputted infrared image.

At this time, the non-uniformity correction unit calculates a temperature change per pixel detected by the infrared detector, and controls the shutter control unit to close the shutter when the calculated temperature difference is equal to or larger than the predetermined threshold value, performs non-uniformity correction, . ≪ / RTI >

According to another aspect of the present invention, there is provided a non-uniformity correction method for an infrared ray detector according to a temperature change, the method comprising: detecting infrared rays of an object to be incident through a lens; Generating an infrared image by converting an infrared ray detected for each pixel into a digital value by an A / D converter; Sensing a temperature of the infrared detector; Calculating a temperature difference between a temperature sensed by the temperature sensing unit and a temperature sensed by the temperature sensing unit at a current time when the shutter is in a closed state; Determining whether the calculated temperature difference is greater than or equal to a predetermined threshold; Controlling the shutter control unit to close the shutter when the temperature difference is equal to or greater than a predetermined threshold; Performing non-uniformity correction on the non-uniformity correction portion in a state in which the shutter is closed to generate non-uniformity correction data; And the image correction unit may correct the infrared image by applying the non-uniformity correction data generated by the non-uniformity correction unit to the infrared image generated / outputted by the A / D converter.

At this time, the non-uniformity correction unit calculates the temperature change of each pixel detected by the infrared ray detector, determines whether the calculated temperature difference is equal to or greater than a predetermined threshold value, and controls the shutter control unit to close the shutter Performing nonuniformity correction to generate nonuniformity correction data, and correcting the infrared image by applying the nonuniformity correction data generated by the nonuniformity correction unit to the infrared image generated by the image correction unit and output from the A / D converter As shown in FIG.

According to the thermal camera and the non-uniformity correction method for correcting the non-uniformity in accordance with the temperature change of the infrared ray detector as described above, the period for nonuniformity correction is set periodically, and is set non-periodically according to the temperature change of the infrared ray detector, It has the effect of reducing the correction and increasing the life of the shutter.

The non-uniformity correction period can be set to an optimum variable period according to the temperature of the infrared ray detector.

Therefore, the life of the shutter can be maximized while maintaining the quality of the image.

1 is a graph showing changes in characteristics of a pixel according to the temperature of an infrared ray detector.
2 is an illustration of an image in which a shutter is closed and non-uniformity correction is performed.
FIG. 3 is an exemplary view of an infrared image to which a shutter is opened and a non-uniformly corrected offset is applied.
4 is a block diagram of a thermal imaging camera that corrects nonuniformity according to temperature change of an infrared ray detector according to an embodiment of the present invention.
5 is a flowchart of a method for correcting non-uniformity according to temperature change of an infrared ray detector according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail to the concrete inventive concept.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Like reference numerals are used for like elements in describing each drawing.

The terms first, second, A, B, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, .

On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise.

In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to FIGS. 4 and 5. FIG.

4 is a block diagram of a thermal imaging camera that corrects nonuniformity according to temperature change of an infrared ray detector according to an embodiment of the present invention.

Referring to FIG. 4, a thermal imaging camera 100 (hereinafter referred to as a thermal imaging camera) for correcting irregularities according to temperature changes of an infrared ray detector according to an embodiment of the present invention includes a lens 110, a shutter 120, A shutter control unit 130, an infrared ray detector 140, an A / D converter 150, a temperature sensing unit 160, a non-uniformity correction unit 170, and an image correction unit 180.

The thermal camera 100 may be configured to perform nonuniformity correction according to the temperature change of the infrared ray detector 140 without periodically setting the period for nonuniformity correction such as 1 minute or 10 minutes so as to reduce unnecessary or too frequent nonuniformity correction times, 120 can also be increased.

That is, the thermal camera 100 can normally maintain the quality of the infrared image at the optimal nonuniformity correction timing.

Hereinafter, the detailed configuration will be described.

A lens 110 is an optical system configuration in which an infrared ray of a subject is incident.

A shutter 120 blocks the infrared ray incident through the lens 110. In the present invention, the shutter 120 is used for non-uniformity correction through interception of infrared rays.

The shutter control unit 130 controls an operation of closing or opening the shutter 120. [

The infrared ray detector 140 is provided as a plurality of infrared ray sensors per pixel.

The infrared ray detector 140 is configured to detect infrared rays incident through the lens 110 and the shutter 120 on a pixel-by-pixel basis.

The A / D converter 150 converts the infrared ray detected by the infrared ray detector 140 into a digital value to generate and output an infrared ray image.

The temperature sensing unit 160 is configured to directly sense the temperature of the infrared ray detector 140. As the temperature of the infrared ray detector 140 is rapidly changed, the deviation of each infrared ray detector 140 is generated for each component.

The temperature sensing unit 160 is configured to directly sense the temperature of the infrared ray detector 140 or to calculate a temperature change per pixel detected by the infrared ray detector 140. [ The infrared detector 140 can detect the degree of change of the electrical signal according to the amount of infrared rays to estimate or detect the temperature change of the infrared ray detector 140 itself. Thus, it is possible to indirectly recognize that the timing for non-uniformity correction is reached.

The nonuniformity correction unit 170 is configured to calculate a temperature difference between the temperature sensed by the temperature sensing unit 160 and the temperature sensed by the temperature sensing unit 160 at the present time in a state in which the shutter 120 is closed. This is to judge whether the temperature change of the infrared ray detector 140 becomes large and the timing of non-uniformity correction is reached.

The nonuniformity correction unit 170 is configured to control the shutter control unit 130 to close the shutter 120 and perform nonuniformity correction to generate nonuniformity correction data when the calculated temperature difference is equal to or greater than a predetermined threshold value. The amount of infrared rays detected by the infrared ray detector 140 while the shutter 120 is closed must be constant for each pixel, and a deviation occurs for each infrared ray detector 140. [ At this time, the deviation or offset becomes non-uniformity correction data, which is stored in a memory and used for correction of an infrared image.

On the other hand, the non-uniformity correction unit 170 may be configured to estimate the non-uniformity correction timing by calculating the temperature change per pixel detected by the infrared ray detector 140 without directly measuring the temperature of the infrared ray detector 140. [

The non-uniformity correction unit 170 is configured to determine a temperature change of the infrared ray detector 140 through a temperature change of each pixel in which infrared rays are detected, and to determine whether a temperature difference between the calculated pixels themselves is a predetermined threshold value or more .

If the temperature difference is equal to or greater than the predetermined threshold value, the non-uniformity correction unit 170 controls the shutter control unit 130 to close the shutter 120 and performs nonuniformity correction to generate nonuniformity correction data.

The image correction unit 180 is configured to correct the infrared image by applying the non-uniformity correction data generated by the non-uniformity correction unit 170 to the infrared image generated / outputted from the A / D converter 150. [

5 is a flowchart of a method for correcting non-uniformity according to temperature change of an infrared ray detector according to an embodiment of the present invention.

Referring to FIG. 5, first, the infrared ray detector 140 detects infrared rays of an object incident through the lens 110 on a pixel-by-pixel basis (S101).

Next, the A / D converter 150 converts the infrared rays sensed for each pixel into digital values to generate / output an infrared image (S102).

Next, the temperature sensing unit 160 senses the temperature of the infrared ray detector 140 (S103).

Next, the nonuniformity correction unit 170 calculates the temperature difference between the temperature sensed by the temperature sensing unit 160 and the temperature sensed by the temperature sensing unit 160 at the present time in a state in which the shutter 120 is closed (S104 ).

At this time, the non-uniformity correction unit 170 determines whether the previously calculated temperature difference is equal to or greater than a predetermined threshold (S105).

If the temperature difference is equal to or greater than the predetermined threshold value, the non-uniformity correction unit 170 controls the shutter control unit 130 to close the shutter 120 (S106).

If the temperature difference is less than or equal to the predetermined threshold value, the non-uniformity correction unit 170 calculates the temperature change per pixel detected by the infrared ray detector 140 (S105a)

The non-uniformity correction unit 170 determines whether the calculated temperature difference is equal to or greater than the threshold value. If the difference is equal to or greater than the threshold value, the non-uniformity correction unit 170 controls the shutter control unit 130 to close the shutter 120 (S106).

Next, in a state in which the shutter 120 is closed, the nonuniformity correction unit 170 performs nonuniformity correction to generate nonuniformity correction data (S107).

Next, the image correction unit 180 corrects the infrared image by applying the non-uniformity correction data generated by the non-uniformity correction unit 170 to the infrared image generated / outputted from the A / D converter 150 (S108).

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the following claims. There will be.

110: lens
120: Shutter
130:
140: Infrared detector
150: A / D converter
160: Temperature sensing unit
170: Non-uniformity correction unit
180: Image correction unit

Claims (4)

In a thermal imaging camera,
A lens through which infrared rays of a subject are incident;
A shutter;
A shutter control unit for closing or opening the shutter;
A plurality of infrared detectors for detecting infrared rays incident through the lens and the shutter for each pixel;
An A / D converter for converting an infrared ray detected by the infrared ray detector into a digital value and generating / outputting an infrared ray image;
A temperature sensing unit for sensing a temperature of the infrared ray detector;
Wherein the controller calculates the temperature difference between the temperature sensed by the temperature sensing unit and the temperature sensed by the temperature sensing unit at the present time when the shutter is closed and if the calculated temperature difference is equal to or greater than the predetermined threshold, A non-uniform correction unit that performs non-uniform correction and controls non-uniformity correction so as to generate non-uniformity correction data;
And an image correction unit for correcting an infrared image by applying non-uniformity correction data generated by the non-uniformity correction unit to the generated / outputted infrared image. The apparatus according to claim 1, wherein the non-
Wherein when the calculated temperature difference is equal to or greater than a predetermined threshold value, the shutter control unit controls the shutter to close and performs non-uniformity correction to generate non-uniformity correction data. A thermal camera that corrects for irregularities according to the temperature change of the infrared detector. Detecting an infrared ray of an object incident on the infrared ray detector through the lens;
Generating an infrared image by converting an infrared ray detected for each pixel into a digital value by an A / D converter;
Sensing a temperature of the infrared detector;
Calculating a temperature difference between a temperature sensed by the temperature sensing unit and a temperature sensed by the temperature sensing unit at a current time when the shutter is in a closed state;
Determining whether the calculated temperature difference is greater than or equal to a predetermined threshold;
Controlling the shutter control unit to close the shutter when the temperature difference is equal to or greater than a predetermined threshold;
Performing non-uniformity correction on the non-uniformity correction portion in a state in which the shutter is closed to generate non-uniformity correction data;
And correcting the infrared image by applying the non-uniformity correction data generated by the non-uniformity correction unit to the infrared image generated / outputted from the A / D converter by the image correction unit. Non-uniformity correction method. 4. The method according to claim 3, wherein, in the step of determining whether the non-uniformity correction section calculates the calculated temperature difference to be equal to or greater than a predetermined threshold value,
Wherein the non-uniformity correction unit calculates the temperature change of each pixel detected by the infrared ray detector, and determines whether the calculated temperature difference is equal to or greater than a predetermined threshold value, and controls the shutter control unit to close the shutter when the calculated temperature difference is equal to or greater than a predetermined threshold, And correcting the infrared image by applying the non-uniformity correction data generated by the non-uniformity correction unit to the infrared image generated / outputted by the image correction unit by the A / D converter And correcting the non-uniformity according to the temperature change of the infrared ray detector.

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