KR20180122234A - Adaptive signal calibration method to environmental changes for cooling type infrared imaging system - Google Patents

Abstract

The present invention relates to a method for correcting an output signal of an infrared image system which constantly maintains an output signal even when an internal temperature is changed by applying output signal correction for a change of an external temperature and the internal temperature and a change of a cooling temperature of an infrared image system and can maintain a certain level of image quality since noise is not increased when the cooling temperature is changed, and a device thereof. According to an embodiment of the present invention, the output signal correction method of an infrared image system comprises the following steps of: defining an output signal model of an infrared detector of a cooling type infrared image system based on the change of the external temperature of the cooling type infrared image system and the internal temperature of the cooling type infrared image system; obtaining a predetermined number of internal temperature data within an internal temperature range to be corrected while constantly maintaining the external temperature based on the output signal model; and adaptively correcting an image output signal according to the change of the external temperature and the internal temperature based on the output signal model and the obtained internal temperature data.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of calibrating an output signal of a cooling type infrared image system,

The present invention relates to a method of calibrating an output signal adaptive to ambient environment changes for a cooling infrared image system.

Infrared image system is a system that generates infrared image by detecting radiant energy (external temperature) from the outside (sight) by using infrared detector and requires fast operation time and excellent responsiveness. Cooling type infrared detectors are generally applied. In order to generate a high-quality infrared image, such a cooling infrared image system should be able to detect a minute difference in radiant energy from the outside. However, the level of energy that is focused on the focal plane array (FPA) of the infrared detector is non-uniform according to the position of the focal plane array, and the readout integrated circuit (ROIC) amplifier of the infrared detector A linear pattern noise (FPN) is generated in the output signal due to the difference of the output of the phase shifter.

In order to correct the non-uniform characteristic (noise) of the output signal of the infrared ray detector and to obtain a high-quality infrared ray image, a method of compensating the output signal to be adaptive to various operating environments of the infrared ray image system and robust against changes in the surrounding environment It is a required skill.

The output signal correction method of the infrared image system according to the related art can be divided into a reference-based correction method and a scene-based correction method.

The reference-based correction method is basically a process of acquiring data for a reference temperature to be referred to in advance and generating correction data for output signal correction using the obtained reference data This is important. For this purpose, it is possible to correct the output signal over a wide temperature range by generating data by dividing the temperature interval into several sections, but there is a disadvantage that a large amount of memory is required. If an additional device such as a mechanical shutter is used, it may cause problems such as parts cost, layout space, etc. Also, it takes time for shutter operation and correction data update, .

The image-based correction method is advantageous in that it does not require a pre-correction data acquisition process and a test equipment therefor. However, since the next frame is corrected using the current frame and previous frame information, convergence time ) And it can not adapt quickly in case of sudden change of image. Above all, such prior arts only consider correction for changes in external temperature, and there is a limit to correcting the change in the output signal according to the internal temperature of the image system.

In the cooling type infrared image system according to the related art, all output signal correction methods have been proposed on the assumption that the cooling temperature (FPA temperature) of the infrared ray detector is kept constant. However, according to the environment in which the infrared ray image system is applied, (E.g., ambient pressure change, detector temperature change, etc.). It is possible to implement additional circuits or devices for keeping the cooling temperature constant, but the application of such additional devices requires consideration of the operational reliability of the additional device itself, and the heat generation, vibration, etc., Infrared imaging system performance may be affected. As a result, the prior art has a limitation in adaptively coping with a noise increase due to a change in cooling temperature and a deterioration in the quality of an infrared image due to an offset change of an output signal.

It is an object of the present invention to provide a method and apparatus for adjusting the output signal of an infrared image system by applying an output signal correction to an external temperature and an internal temperature change and a change of a cooling temperature, The present invention provides a method and apparatus for correcting an output signal of an infrared image system that can maintain a constant level of image quality as a result.

The problems of the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a method of calibrating an output signal of an infrared image system, the method comprising the steps of: sensing a temperature of a cooling type infrared image system based on a change in an external temperature of the cooling type infrared image system and an internal temperature of the cooling type infrared image system; Defining an output signal model of the infrared detector of the imaging system; Obtaining a predetermined number of internal temperature data within an internal temperature range to be corrected while maintaining the external temperature constant, based on the output signal model; And adaptively correcting an image output signal according to an external temperature and an internal temperature change based on the output signal model and the acquired internal temperature data.

식을 통해 외부온도 및 내부온도를 모두 고려하는 출력 신호 모델(

)을 정의하며, 여기서, G_S는 외부온도에 따른 신호이득(Gain), V_S는 외부온도에 해당하는 균일한 입력신호, O_S는 외부온도에 따른 신호옵셋(Offset), G_I는 내부온도에 따른 신호이득, O_I는 내부온도에 따른 신호옵셋, V_I는 내부온도에 해당하는 입력신호일 수 있다.The present invention

An output signal model that takes both external and internal temperature into account

) To define, where, G _S is the signal gain (Gain), V _S is a uniform input signal that corresponds to the external temperature, O _S is the signal offset (Offset) according to the outside temperature of the outside temperature, G _I is the internal O _I is the signal offset according to the internal temperature, and V _I is the input signal corresponding to the internal temperature.

식을 통해 외부온도 및 내부온도 변화에 따른 영상출력신호를 적응적으로 보정할 수 있다.According to the present invention,

The image output signal according to the change of the external temperature and the internal temperature can be adaptively corrected.

The present invention relates to a cooling type infrared image system in which only an external temperature change corresponding to infrared radiation energy from the outside is detected to generate an output signal and an internal temperature for maintaining a constant output signal even when the internal temperature changes An internal temperature compensation method and an output signal correction model can be defined.

식을 통해 정의되며, 여기서 V_TCOMP는 내부온도(V_I)를 변화시키면서 출력신호(V_S)가 일정하게 유지되는 보상신호일 수 있다.The present invention provides an output signal correction model for maintaining a constant output signal even when the internal temperature changes

Where V _TCOMP may be a compensation signal whose output signal V _S is kept constant while varying the internal temperature V _I.

식을 통해 정의하며, 여기서, O_FPACOMP는 냉각형 적외선영상시스템에서 적외선검출기의 냉각온도 변화에 따른 영상출력신호변화를 보정하기 위하여 일정하게 유지되는 냉각온도에서의 기준옵셋과 냉각온도가 변함에 따라 달라지는 옵셋의 차이일 수 있다.The present invention may further comprise the step of defining a calibration model that adaptively corrects the output signal to a change in cooling temperature corresponding to a focal plane array (FPA) temperature of the infrared detector, A calibration model that compensates the output signal adaptively to the change

O _FPACOMP is defined as a function of the reference offset and the cooling temperature at a constant cooling temperature to compensate for the change of the image output signal according to the cooling temperature of the infrared detector in the cooling infrared image system It may be the difference of the different offsets.

The details of other embodiments are included in the detailed description and drawings.

A method and apparatus for correcting an output signal of an infrared image system according to an embodiment of the present invention includes applying an output signal correction to an external temperature and an internal temperature change of an infrared image system to maintain the output signal constant, In addition, since the noise is not increased, a certain level of image quality can be maintained as a result. For example, if only the correction to the external temperature is applied, the noise increases as the internal temperature changes. However, if the output signal correction for the external temperature and the internal temperature change is applied, the output signal remains constant even if the internal temperature changes, The image quality can be maintained at a constant level as a result. When the output signal correction for the cooling temperature change is performed, a certain level of noise can be maintained even if the cooling temperature changes. However, if the cooling temperature is not corrected, if the cooling temperature changes at the reference temperature, the noise increases and the image quality deteriorates.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the claims.

1 is a flowchart illustrating an output signal correction method of an infrared image system according to an embodiment of the present invention.
FIG. 2 illustrates a method of approximating a compensation signal to an internal temperature of an infrared image system according to an embodiment of the present invention. Referring to FIG.
FIG. 3 is a graph illustrating an offset of an output signal according to a cooling temperature of an arbitrary number of infrared detectors.
FIGS. 4A and 4B are diagrams illustrating changes in noise after correction of an output signal with respect to an internal temperature change. FIG.
FIG. 5 is a graph showing performance according to whether or not an output signal correction method for cooling temperature changes is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like or similar components are denoted by the same reference numerals, and redundant explanations thereof will be omitted. The suffix "module" and " part "for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role. In the following description of the embodiments of the present invention, a detailed description of related arts will be omitted when it is determined that the gist of the embodiments disclosed herein may be blurred. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. , ≪ / RTI > equivalents, and alternatives.

Terms including ordinals, such as first, second, etc., may be used to describe various elements, but the elements are not limited to these terms. The terms are used only for the purpose of distinguishing one component from another.

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 singular expressions include plural expressions unless the context clearly dictates otherwise.

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

The following method of correcting the output signal according to the change in the external temperature and the internal temperature of the cooling infrared image system can be implemented by the control unit or the correction unit in the cooling infrared image system. Hereinafter, a method of correcting the output signal according to the change in the external temperature and the internal temperature of the cooling type infrared image system will be described in the control unit in the cooling type infrared image system.

1 is a flowchart illustrating an output signal correction method of an infrared image system according to an embodiment of the present invention.

First, the control unit defines the output signal model of the infrared detector in the cooling type infrared image system as shown in the following Equation 1 (S11).

Here, V _O is the output signal (output signal non-uniformity) of the infrared detector in the cooled-type infrared imaging system, V _S is the input signal corresponding to a uniform radiation (external temperature) from the outside, and _{S is} G Signal gain (Gain) according to external temperature, and O _S is signal offset (Offset) according to external temperature.

In order to obtain a uniform output signal, an output signal for a plurality of external temperatures is measured, and a signal gain and a signal offset are obtained based on the measured data to obtain a correction formula as shown in Equation 2 below.

The infrared detector in the cooling type infrared image system has both the unevenness of the output signal due to the change in the external temperature and the influence due to the change in the internal temperature of the cooling type infrared image system. To this end, the present invention proposes a method for real-time output signal correction that can be applied adaptively to changes in the surrounding environment for generating a high-quality infrared image of a cooling infrared image system. (2) a method of adaptively adjusting the output signal adaptively to changes in the cooling temperature (focal plane array (FPA) temperature);

Hereinafter, an output signal correction method adaptive to the internal temperature change of the cooling infrared image system will be described.

It can be seen that when the internal temperature is changed while the external temperature is constant, the output signal varies unevenly. Therefore, the signal offset Os, which is the second term of Equation 1, is defined as a signal model such as Equation 3 in which the internal temperature change is taken into consideration.

V _I is the input signal corresponding to the internal temperature of the cooling infrared image system, G _I is the signal gain according to the internal temperature of the cooling infrared image system, O _I is the signal offset according to the internal temperature of the cooling infrared image system, to be.

Equation (3) is substituted into Equation (1) and defined as an output signal model that can take both external temperature and internal temperature into account as shown in Equation (4).

In order to obtain the signal gain and offset according to the internal temperature, the first term (G _S × V _S ) and the third term (O _I ) of Equation (4) can be summarized as Equation (5)

The control unit maintains the external temperature constant (G _S x V _S fixed), changes the internal temperature Obtain the output signal. At this time, the control unit obtains a predetermined number of data within an internal temperature range to be corrected based on the output signal model (S12), and calculates a linear regression equation G _I and K are obtained. Wherein _{K = G S × V S +} O it can be obtained because the _I O, the control unit (S13) and in the external temperature and the internal temperature correct the output signal adaptively by using the equation (6).

Hereinafter, the internal temperature compensation for the internal temperature will be described.

The infrared imaging system should only detect infrared radiation from the outside and be able to maintain a stable output signal even when the internal temperature changes. In other words, the output signal V _S should remain constant even if V _I changes in Equation 6.

To this end, the controller performs internal temperature compensation on the internal temperature. As shown in FIG. 1, a compensation signal (V _TCOMP ) which can keep the output signal (V _S ) constant while changing the internal temperature (V _I ) is obtained by multiplying the internal temperature (N > = 1).

FIG. 2 illustrates a method of approximating a compensation signal to an internal temperature of an infrared image system according to an embodiment of the present invention. Referring to FIG. That is, FIG. 2 is a method for approximating a compensation signal for an internal temperature at which an output signal can be kept constant even if the internal temperature changes for signal compensation with respect to the internal temperature. In order to approximate the accuracy, .

Therefore, if the internal temperature changes, a compensation signal (V _TCOMP ) for the temperature can be obtained. Substituting V _I in Equation (6) with the compensation signal (V _TCOMP ) adaptively corrects the output signal for changes in the external temperature and the internal temperature and adjusts the output signal correction model to maintain the output signal constant even if the internal temperature changes (7) " (7) "

Hereinafter, the correction of the output signal with respect to the change in the temperature of the infrared detector cooling will be described.

The cooling infrared detector must maintain a constant cooling temperature (focal plane array (FPA) temperature) of the detector. If the cooling temperature changes, the dark current inherent to the detector changes, and the offset of the output signal changes. As described above, if the cooling temperature is changed, the quality of the infrared image corrected by Equation (7) is deteriorated.

Accordingly, the controller additionally performs detector cooling temperature compensation (FPA temperature compensation) in order to adaptively adapt the output signal to the cooling temperature change of the infrared detector.

The detector cooling temperature compensation is a method for compensating for the offset difference (O _FPACOMP ) that varies as the cooling temperature is changed and the reference offset at the cooling temperature which is kept constant. As shown in FIG. 3, (N > = 1). ≪ / RTI >

FIG. 3 is a view showing an offset of an output signal according to a cooling temperature of an arbitrary number of infrared detectors, and an offset of an output signal according to an arbitrary number of detector cooling temperatures is obtained and represented by an n-th degree polynomial (n ≥ 1) .

O < _{RTI ID} = 0.0 & gt _{; I} < / _{RTI &} - O _FPACOMP , a calibration model that can adaptively adapt the output signal to the temperature change of the infrared detector cooling temperature can be obtained as shown in Equation (8).

FIGS. 4A and 4B are diagrams illustrating changes in noise after correction of an output signal with respect to an internal temperature change. FIG. That is, FIGS. 4A and 4B are diagrams for obtaining an output image for a black body, which is a standard light source for infrared rays, in order to confirm that the performance is maintained in a state where an internal temperature is changed by applying an output signal correction for an internal temperature change, Respectively. At the reference internal temperature of 20 ° C, even when only the output signal correction to the external temperature was applied, the noise was small, but the noise increased greatly due to the change of the internal temperature. However, if both the external temperature and the internal temperature change are corrected, the noise is kept at a constant level even if the internal temperature changes.

FIG. 5 is a graph showing performance according to whether or not an output signal correction method for cooling temperature changes is applied. That is, FIG. 5 shows the noise level of the output infrared image while keeping the cooling temperature at about 81K and lowering the cooling temperature to about 73K in order to confirm the performance according to the application of the output signal correction technique to the cooling temperature change . In the case of applying the output signal correction according to the cooling temperature, it was confirmed that even if the cooling temperature was changed, the noise was kept at a low level. However, it was confirmed that the noise was greatly increased when the cooling temperature was not applied. .

As described above, the output signal correction method and apparatus of the infrared image system according to the embodiment of the present invention apply the output signal correction to the external temperature and the internal temperature change of the infrared image system, And the noise is not increased. As a result, a certain level of image quality can be maintained. For example, if only the correction to the external temperature is applied, the noise increases as the internal temperature changes. However, if the output signal correction for the external temperature and the internal temperature change is applied, the output signal remains constant even if the internal temperature changes, The image quality can be maintained at a constant level as a result. When the output signal correction for the cooling temperature change is performed, a certain level of noise can be maintained even if the cooling temperature changes. However, if the cooling temperature is not corrected, if the cooling temperature changes at the reference temperature, the noise increases and the image quality deteriorates.

Claims (6)

A method for correcting an image output signal in a cooling infrared image system,
Defining an output signal model of an infrared detector of a cooling infrared image system based on a change of an external temperature of the cooling infrared image system and an internal temperature of the cooling infrared image system;
Obtaining a predetermined number of internal temperature data within an internal temperature range to be corrected while maintaining the external temperature constant, based on the output signal model;
And adaptively correcting an image output signal according to an external temperature and an internal temperature change based on the output signal model and the acquired internal temperature data. The method according to claim 1,

An output signal model that takes both external and internal temperature into account

) To define, where, G _S is the signal gain (Gain), V _S is a uniform input signal that corresponds to the external temperature, O _S is the signal offset (Offset) according to the outside temperature of the outside temperature, G _I is the internal Wherein O _i is a signal offset according to an internal temperature, and V _I is an input signal corresponding to an internal temperature. 3. The method of claim 2,

Wherein an image output signal according to an external temperature and an internal temperature change is adaptively corrected through an equation. The method of claim 3,
The cooling type infrared image system generates an output signal by detecting only an external temperature change corresponding to the infrared radiation energy from the outside, and compensates the internal temperature for maintaining a constant output signal even when the internal temperature changes An internal temperature compensation method and an output signal correction model are defined. 5. The method of claim 4,
An output signal correction model for maintaining a constant output signal even when the internal temperature changes

Wherein V _TCOMP is a compensation signal whose output signal V _S is kept constant while changing the internal temperature V _I. 6. The method of claim 5,
Further comprising the step of defining a calibration model to adaptively adapt the output signal to a change in cooling temperature corresponding to a focal plane array (FPA) temperature of the infrared detector, The correction model, which corrects the output signal,

≪ / RTI > where < RTI ID =
O _FPACOMP is a difference between a reference offset at a constant cooling temperature and an offset that varies as the cooling temperature changes to compensate for a change in the image output signal due to the cooling temperature change of the infrared detector in a cooling infrared image system A method of calibrating an output signal of an infrared imaging system.

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