KR102041234B1 - Bolometer thermogram apparatus and method for correcting process variation per pixel - Google Patents

Abstract

Disclosed in the present invention are a bolometer thermal imaging apparatus and method for correcting pixel-by-pixel process deviations. According to the present invention, the bolometer thermal imaging apparatus comprises: a pixel array consisting of a two-dimensional array of unit pixels in which a bolometer which senses thermal information of a subject and a reference resistance, which is a reference for correction, are connected in series with a pixel bias voltage; and a control unit for controlling a first mode for correcting a process deviation of a corresponding unit pixel by using a division voltage of a pixel bias voltage of a selected unit pixel in a unit pixel array, and a second mode for sensing thermal image information of the subject by using the unit pixel having the process deviation corrected in the unit pixel array.

Description

Bolometer thermogram apparatus and method for correcting process variation per pixel

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal imager, and more particularly, to a bolometer thermal imager and method for correcting a process deviation for each pixel for correcting a process deviation for each pixel of a thermal imager using a bolometer.

In general, when correcting a resistance variation of a bolometer element for each pixel generated in a manufacturing process of a bolometer thermal imaging camera, the basic pixel configuration is the same resistance value as an active bolometer for detecting heat of a real subject. Although the reference bolometer is connected in series with the heat of the subject blocked, and the array of correction resistors and the selectable MOS switches of these resistors are connected.

In addition, the operation principle for this is that when the resistance value of the effective bolometer and the reference bolometer is completely the same while the subject heat source is completely dark, the integrator output of the readout circuit is fixed to a specific value. However, if there is a deviation in the two bolometer resistances, the integrator output will charge or discharge at a specific value in proportion. Therefore, in the past, information on the process deviation of the bolometer was obtained by reading a specific value of the integrator output. Here, the information on the process deviation of each pixel is stored in the frame memory through an analog-to-digital converter (ADC).

That is, the conventional technology controls the MOS switches of each pixel and adjusts the correction resistance value by using the deviation information for each pixel stored in the frame memory so that the integrator output is fixed to a specific value for all pixels. After correcting the deviation of the resistance of the bolometer for each pixel, if the effective bolometer of each pixel to sense the column of the subject it is possible to obtain a desired thermal image.

However, in the conventional technology, all of the MOS switches for selecting correction resistor arrays have ON resistance (RSD_ON) deviation, and these are connected to the correction resistors in parallel again, so that it is difficult to obtain the desired correction value accurately. In addition, there is a limit to the resolution of combining discontinuous resistance values to create a resistance value for a desired correction.

Therefore, there is a need for a method of correcting the process deviation of the bolometer for each pixel that can solve the above problems.

Korea Patent Publication No. 10-1806860 (2017.12.04.)

SUMMARY OF THE INVENTION An object of the present invention is to provide a bolometer thermal imager and a method for correcting a pixel-specific process deviation for correcting a deviation of a bolometer resistance value for each pixel generated in a manufacturing process using a pixel or a readout circuit. .

In order to achieve the above object, a bolometer thermal imager for correcting the process deviation of each pixel according to the present invention is a unit in which a bolometer for detecting thermal information of a subject and a reference resistance, which is a reference for correction, are connected in series with a pixel bias voltage. The process deviation of the unit pixel is corrected by using a unit pixel array having a two-dimensional array of pixels and a division voltage of a pixel bias voltage which is an output voltage of a selected unit pixel among the unit pixel arrays. And a controller configured to control a second mode of detecting thermal image information of the subject using a unit pixel in which a process deviation is corrected among the first mode and the unit pixel array.

The controller may control the second mode to be performed after the first mode is performed on all the unit pixels of the unit pixel array.

When the first mode is performed, the controller amplifies a difference value between the output voltage and the reference voltage, which is process deviation correction information of the selected unit pixel, through an amplifier stage using an OP-AMP, and outputs the amplifier stage. The bias voltage of the unit pixel is controlled by connecting the voltage to the pixel bias voltage of the unit pixel using a feedback loop so that the output voltage of the unit pixel and the reference voltage are the same.

The control unit may convert the output voltage of the amplifying stage, which is the process deviation correction information, into a digital value, and control the stored process deviation correction information to be stored for each unit pixel.

When the second mode is performed, the controller breaks the feedback loop of the first mode, converts the process deviation correction information stored for each unit pixel into an analog value using another feedback loop, and converts the converted process deviation. The correction information may be connected to the pixel bias voltage of the corresponding unit pixel to control sensing of the thermal image information in a state in which the process deviation of the unit pixel is corrected.

The controller may be further configured to perform image signal processing on a change in the output voltage of the unit pixel generated when the resistance value of the bolometer is changed by the thermal image information when the correction of the process deviation of the unit pixel is completed.

The controller may control the change of the output voltage to have noise immunity.

The controller may perform mode switching of the first mode and the second mode through switching control.

The controller may perform the first mode in a state where the heat of the subject is blocked, and perform the second mode in a state where the heat of the subject is detected.

A method of correcting a process deviation for each pixel according to the present invention includes a unit pixel array having a two-dimensional array of unit pixels in which a bolometer for detecting thermal information of a subject and a reference resistance, which is a reference for correction, are connected in series with a pixel bias voltage. Controlling the process deviation of the corresponding unit pixel by using a division voltage of a pixel bias voltage which is an output voltage of a selected unit pixel of the unit pixel array, and the bolometer thermal imager of the unit pixel array And detecting thermal image information of the subject by using a unit pixel of which process deviation is corrected.

In the bolometer thermal imager and method for correcting the process deviation of each pixel of the present invention, the output voltage and the reference voltage of the unit pixel distributed by the bolometer and the reference resistance are respectively input to the amplifier stage, and the output of the amplifier stage is the pixel bias of the corresponding unit pixel. The feedback circuit can be configured to be equal to the voltage to correct the process deviation of the unit pixel.

Through this, the present invention can effectively improve the quality of the thermal image by correcting the process deviation.

1 is a block diagram illustrating a bolometer thermal imager according to an embodiment of the present invention.
2 is a schematic diagram illustrating a bolometer thermal imager according to an embodiment of the present invention.
3 is a diagram for describing a unit pixel and a readout circuit of the bolometer thermal imager according to the first embodiment of the present invention.
4 is a view for explaining a first mode operation of the bolometer thermal imaging apparatus according to the first embodiment of the present invention.
5 is a view for explaining a second mode operation of the bolometer thermal imaging apparatus according to the first embodiment of the present invention.
FIG. 6 is a diagram for describing a unit pixel and a readout circuit of the bolometer thermal imager according to the second embodiment of the present invention.
7 is a diagram for describing a method of correcting a process deviation for each pixel according to an exemplary embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the components of each drawing, it is noted that the same reference numerals are assigned to the same components as much as possible, even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function is apparent to those skilled in the art or may obscure the gist of the present invention, the detailed description thereof will be omitted.

1 is a block diagram illustrating a bolometer thermal imager according to an embodiment of the present invention.

Referring to FIG. 1, the bolometer thermal imager 100 corrects a variance in bolometer resistance for each pixel generated in a manufacturing process by using a pixel or a readout circuit.

The bolometer thermal imager 100 includes a unit pixel array 10 and a controller 30, and further includes an output unit 50 and a storage unit 70.

In the unit pixel array 10, a bolometer for sensing thermal information of a subject and a unit pixel in which a reference resistance, which is a reference for correction, are connected in series with a pixel bias voltage are formed in a two-dimensional array. Here, the reference resistance may be a general resistance element or a reference bolometer that is dark (heat).

The controller 30 processes the first mode and the unit pixel array 10 to correct the process deviation of the corresponding unit pixel by using the divided voltage of the pixel bias voltage which is the output voltage of the selected unit pixel of the unit pixel array 10. The second mode of detecting the thermal image information of the subject is controlled by using the unit pixel in which the deviation is corrected. In this case, the controller 30 may perform mode switching between the first mode and the second mode as the switching control. In addition, the controller 30 may control the second mode to be performed after the first mode is performed on all the unit pixels of the unit pixel array 10, but the present invention is not limited thereto, and the first mode is performed before the process deviation. If is corrected, the second mode may be directly performed without performing the first mode. Meanwhile, the controller 30 may perform the first mode in a dark state in which the heat of the subject is blocked, and perform the second mode in a state in which the heat of the subject is detected.

The output unit 50 outputs thermal image information of the subject detected in the second mode. The output unit 50 outputs the thermal image information of the subject in black and white shades or colors. The output unit 50 may be a display such as a liquid crystal display, a thin film transistor liquid crystal display, an organic light emitting diode, a flexible display, a three-dimensional display, or the like. In addition, the output unit 50 may be a beam projector, a printer, or the like.

The storage unit 70 stores the thermal image information detected by the bolometer. The storage unit 70 stores the process deviation correction information and the pixel bias voltage for each pixel, which are a result of comparing the difference between the output voltage and the reference voltage of the unit pixel calculated by the controller 30. The storage unit 70 may be a flash memory type, a hard disk type, a media card micro type, a card type memory (for example, SD or XD memory, etc.), RAM, SRAM, ROM, EEPROM, PROM, magnetic memory, magnetic disk. And at least one storage medium of the optical disc.

2 is a schematic diagram illustrating a bolometer thermal imager according to an embodiment of the present invention.

1 and 2, the bolometer thermal imager 100 corrects the process deviation by controlling the pixel bias voltage of the unit pixel 11 without correcting the resistance value of the bolometer. To this end, the bolometer thermal imager 100 may include the following configuration.

The bolometer thermal imager 100 includes a unit pixel 11, a row address decoder 31, an amplifier 32, an analog-to-digital converter 33, a digital-to-analog converter 34, a thermal multiplexer. (column MUX) 35 and frame memory 71. Here, the unit pixel 11 is included in the unit pixel array 10, and the row address decoder 31, the amplifier 32, the analog-to-digital converter 33, the digital-to-analog converter 34, and the column multiplexer ( 35 is included in the controller 30, and the frame memory 71 is included in the storage 70. In this case, the controller 30 may be a readout circuit.

The unit pixel 11 includes a bolometer and a reference resistor. The unit pixels 11 are arranged in two dimensions to form the unit pixel array 10. For example, the unit pixel 11 is arranged to have m (m is a natural number) rows and n (n is a natural number) columns. The row address decoder 31 selects a desired row in the unit pixel array 10. The amplifier stage 32 amplifies the voltage to read the output voltage of the selected unit pixels 11. Here, the amplifying stage 32 may be an OP-AMP. The analog-to-digital converter 33 converts the analog value into a digital value. Digital-to-analog converter 34 converts digital values to analog values. The thermal multiplexer 35 outputs thermal image information of each column. The frame memory 71 stores process deviation correction information for each pixel.

On the other hand, the bolometer thermal imager 100 is parallel to the columns of the unit pixel array 10 in order to process the amplifier stage 32, the analog-to-digital converter 33, the frame memory 71, and the digital-to-analog converter 34 in parallel. By arranging the column-parallel, the frame rate of the bolometer thermal imager 100 can be increased.

FIG. 3 is a view illustrating a unit pixel and a readout circuit of a bolometer thermal imager according to a first embodiment of the present invention, and FIG. 4 is a first mode of the bolometer thermal imager according to the first embodiment of the present invention. 5 is a view for explaining an operation, and FIG. 5 is a view for explaining a second mode operation of the bolometer thermal imaging apparatus according to the first embodiment of the present invention.

1 to 5, in the bolometer thermal imager 100, a readout circuit is connected to each unit pixel 11 to detect process deviation correction and thermal image information for each pixel.

The unit pixel 11 divides the pixel bias voltage V _A by using the reference resistor R _REF 13 and the bolometer 12 connected in series, and distributes the divided output voltage V _B to the unit pixel switch SW. _ROW ) (14). In this case, the unit pixel switch 14 may be controlled to be opened and closed (on / off) by the row address decoder 31. The amplifier 32 using the op amp receives the output voltage V _B and the reference voltage V _REF of the unit pixel 11, and is connected to the negative input terminal and the positive input terminal of the op amp, respectively. The output voltage V _out of the amplifier stage 32 is output as a digital value through the analog-to-digital converter 33.

Here, the output voltage V _out of the amplifier stage 32 is a bolometer process deviation correction information or thermal image information, and is computed by the calculator 36, respectively. Specifically, the output voltage V _out of the amplifier 32 is process deviation correction information when the first mode is performed, and the output voltage V _out of the amplifier 32 is thermal image when the second mode is performed. Information. Here, the operator 36 may be a microprocessor or a field programmable gate array (FPGA).

In this case, the process deviation correction information calculated through the first mode is stored in the frame memory 71. When the second mode is performed, the stored process deviation correction information is stored in the pixel of the unit pixel 11 through the digital-analog converter 34. The bias voltage V _A is output.

Hereinafter, a process in which the bolometer thermal imager 100 performs the first mode and the second mode will be described.

The first mode is a mode that controls the process deviation of the bolometer to be corrected, and is performed when the first mode switch SW _CAL 37 is closed (on) and the second mode switch SW _SEN 38 is open (off). do. In this case, the unit pixel 11 in which the first mode is performed is selected because the unit pixel switch 14 is closed (on).

In the first mode, the pixel bias voltage V _A of the unit pixel 11 is distributed using the bolometer 12 and the reference resistor 13 connected in series, and then output. In this case, the output voltage V _B of the output unit pixel 11 may be expressed as shown in [Equation 1].

Here, R _B means the resistance of the bolometer.

When the virtual ground of the amplifier stage 32 using the op amp is used, the output voltage V _B of the unit pixel 11 is equal to the reference voltage V _REF , and the output voltage ( Since V _out ) is directly connected to the bias voltage V _A of the unit pixel 11 through a feedback loop, Equation 1 may be expressed as Equation 2 below.

That is, when the resistance R _B of the bolometer 12 changes due to the process deviation with a constant reference voltage V _REF , the control unit 30 determines that the output voltage V _B of the unit pixel 11 is the reference voltage. The output voltage V _out of the amplifier stage 32 is controlled to be equal to (V _REF ) as shown in [Equation 2].

The controller 30 may obtain the process deviation correction information for the selected unit pixel 11 by converting the output voltage V _out of the amplifier 32 from an analog value to a digital value and storing it in the frame memory 71. .

The controller 30 may perform this process on all the unit pixels in the two-dimensional array, and separately store the process deviation correction information corresponding to the entire unit pixel array 10 in the frame memory 71.

The second mode is a mode for sensing thermal image information, and is performed when the second mode switch 38 is closed (on) and the first mode switch 37 is open (off). In this case, the unit pixel 11 in which the second mode is performed is selected because the unit pixel switch 14 is closed (on). Preferably, in the second mode, all the unit pixels whose process deviations are corrected may be sequentially selected using the unit pixel switch 14 to obtain thermal image information.

When the second mode is performed, the controller 30 converts process deviation correction information of the corresponding pixel stored in the frame memory 71 from a digital value to an analog value and applies the pixel bias voltage V _A of the corresponding unit pixel. In this way, the controller 30 may complete the correction of the process deviation with respect to the corresponding unit pixel.

When the correction of the process deviation is completed, the controller 30 detects thermal image information. In detail, the controller 30 amplifies and outputs a change in the output voltage V _B of each unit pixel 11 generated when the bolometer resistance value R _B is changed by the thermal image information. The controller 30 converts the output voltage V _OUT of the output amplifier stage 32 from an analog value to a digital value and performs image signal processing on the converted output voltage V _OUT so that thermal image information can be output. To control.

FIG. 6 is a diagram for describing a unit pixel and a readout circuit of the bolometer thermal imager according to the second embodiment of the present invention.

3 and 6, the bolometer thermal imager 100 according to the first embodiment (hereinafter referred to as the first bolometer thermal imager) 100 and the bolometer thermal imager according to the second embodiment (hereinafter referred to as the second bolometer row) The imaging apparatus 200 has the same structure as a whole, but differs in that the second bolometer thermal imaging apparatus 200 implements the amplifying stage 32 in an integrator form.

The second bolometer thermal imager 200 operates in the same manner as the first bolometer thermal imager 100 in the first mode. However, in the second mode, the second bolometer thermal imager 200 is implemented in the form of an integrator in which a negative input terminal and an output terminal of the amplifier stage 32 using the op amp are connected to the capacitor 39. As a result, the second bolometer thermal imager 200 may increase and increase noise immunity.

7 is a diagram for describing a method of correcting a process deviation for each pixel according to an exemplary embodiment of the present invention.

2 and 7, the method for correcting the process deviation for each pixel includes inputting the output voltage and the reference voltage of the unit pixel 11 distributed by the bolometer and the reference resistor to the amplifier 32, respectively. ), The feedback circuit may be configured such that the output of the same unit is equal to the pixel bias voltage of the unit pixel 11, thereby correcting the process deviation of the unit pixel. Through this, in the method of correcting the process deviation of each pixel, the quality of the thermal image may be improved by correcting the process deviation effectively.

In operation S11, the bolometer thermal imaging apparatus 100 or 200 controls the process deviation of the corresponding unit pixel to be corrected by using a divided voltage of the pixel bias voltage which is an output voltage to the selected unit pixel of the unit pixel array 10. The bolometer thermal imagers 100 and 200 amplify the difference between the output voltage and the reference voltage, which are process deviation correction information of the selected unit pixel, through the amplifier stage 32, and output the output voltage of the amplifier stage 32 using a feedback loop. The pixel bias voltage of the unit pixel is controlled by connecting the pixel bias voltage of the unit pixel so that the output voltage and the reference voltage of the unit pixel are the same. The bolometer thermal imagers 100 and 200 convert the process deviation correction information into digital values and store the converted process deviation correction information for each unit pixel.

In operation S13, the bolometer thermal image apparatus 100 or 200 detects thermal image information of the subject using the unit pixel in which the process deviation is corrected among the unit pixel array 10. The bolometer thermal imagers 100 and 200 break the feedback loop in the first mode and convert the process deviation correction information stored for each unit pixel to an analog value by using another feedback loop. The bolometer thermal imagers 100 and 200 detect the thermal image information in a state in which the process deviation of the unit pixel is corrected by connecting the converted process deviation correction information to the pixel bias voltage of the corresponding unit pixel. That is, when the correction of the process deviation of the unit pixel is completed, the bolometer thermal image apparatus 100 or 200 performs image signal processing on the change of the output voltage of the unit pixel generated when the resistance value of the bolometer is changed by the thermal image information. do. Through this, the bolometer thermal imaging apparatus 100 or 200 may output thermal image information.

Preferably, the bolometer thermal imaging apparatus 100 or 200 may perform step S11 on all unit pixels of the unit pixel array 10 and then perform step S13.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

10: unit pixel array
11: module pixel
12: bolometer
13: reference resistance
14: module pixel switch
30: control unit
31: line address decoder
32: amplification stage
33: analog to digital converter
34: digital-to-analog converter
35: thermal multiplexer
36: operator
37: first mode switch
38: second mode switch
39: capacitor
50: output unit
70: storage
71: frame memory
100, 200: Volometer thermal imager

Claims (10)

A unit pixel array in which unit pixels are arranged in a two-dimensional array; And
A first mode for correcting a process deviation of a corresponding unit pixel by using a distribution voltage between a bolometer and a reference resistance of a selected unit pixel of the unit pixel array, and a unit pixel of which a process deviation is corrected among the unit pixel arrays. And a controller configured to control a second mode of detecting thermal image information of the subject using the same.
The unit pixel,
A bolometer thermal imager for correcting a process deviation for each pixel, characterized in that a bolometer for detecting thermal information of a subject and a reference resistor as a reference for the bolometer correction are connected in series with respect to a pixel bias voltage. The method of claim 1,
The control unit,
And a process of performing the first mode and then the second mode for all the unit pixels of the unit pixel array. The method of claim 1,
The control unit,
When the first mode is performed, the difference between the output voltage and the reference voltage, which is process deviation correction information of the selected unit pixel, is amplified by an amplifier stage using an OP-AMP, and the output voltage of the amplifier stage is fed back through a feedback loop ( a bolometer for correcting the process deviation for each pixel, which is connected to the pixel bias voltage of the corresponding unit pixel by controlling a pixel bias voltage of the unit pixel so that the output voltage and the reference voltage of the unit pixel are the same. Thermal imager. The method of claim 3, wherein
The control unit,
And converting the output voltage of the amplifying stage, which is the process deviation correction information, into a digital value, and controlling the stored process deviation correction information to be stored for each unit pixel. The method of claim 4, wherein
The control unit,
When the second mode is performed, the feedback loop of the first mode is interrupted, the process deviation correction information stored for each unit pixel is converted into an analog value by using another feedback loop, and the converted process deviation correction information is applied. And a pixel bias voltage of the unit pixel to control the thermal image information to be detected in a state in which the process deviation of the unit pixel is corrected. The method of claim 5,
The control unit,
When the correction for the process deviation of the unit pixel is completed, the bolometer for correcting the process deviation for each pixel, characterized in that the image signal processing changes in the output voltage of the unit pixel generated by changing the resistance value of the bolometer by the thermal image information Thermal imager. The method of claim 6,
The control unit,
And a process for correcting the process deviation for each pixel, wherein the change in the output voltage is controlled to have noise immunity. The method of claim 1,
The control unit,
And the mode switching of the first mode and the second mode is performed by switching control. The method of claim 1,
The control unit,
And performing the first mode while the heat of the subject is blocked, and performing the second mode when the heat of the subject is sensed. A bolometer thermal imager including a unit pixel array in which a unit pixel is formed in a two-dimensional array is configured to control a process deviation of a corresponding unit pixel by using a distribution voltage between a bolometer and a reference resistor of a selected unit pixel among the unit pixel arrays. step; And
And detecting, by the bolometer thermal imager, thermal image information of the subject using unit pixels whose process deviations are corrected among the unit pixel arrays.
The unit pixel,
A method for correcting a process deviation for each pixel, characterized in that a bolometer for detecting thermal information of a subject and a reference resistor as a reference for correction are connected in series with a pixel bias voltage.

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