JP2019060830A - Infrared camera for temperature detection - Google Patents

Abstract

To provide an infrared camera for temperature detection capable of obtaining thermal images of high resolution while reducing the load imposed to a terminal which performs a series of processing to acquire a thermal image of high resolution and the load during transmission.SOLUTION: The infrared camera for temperature detection composes: an infrared sensor 11 for picking up thermal images of a first number of pixels; a representative value calculation part 13 configured to calculate representative values in block units of a predetermined number of pixels on a thermal image picked up by the infrared sensor 11; and an output part 14 configured to output thermal images of a second number of pixels in which the number of pixels have been subtracted by the representative value calculation part 13. At least one block processed by the representative value calculation part 13 has a representative value which is the maximum value, minimum value, or a difference between the maximum value and the minimum value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a temperature detection infrared camera for obtaining a thermal image for temperature detection.

  An infrared camera that obtains a thermal image by detecting infrared radiation emitted from an object has conventionally been used for various types of thermal analysis. Since the infrared camera has an excellent feature that the temperature distribution can be measured instantaneously without contact, its application range has been expanded.

  A thermal image captured by a conventional infrared camera is, for example, composed of 320 horizontal pixels × 240 vertical pixels, one frame of which is referred to as the QVGA (Quarter Video Graphics Array) standard.

  Patent Document 1 describes an example in which thermal management of a facility (temperature management of a waste disposal site) is performed using a thermal image captured by an infrared camera.

JP 2000-113344 A

  2. Description of the Related Art In recent years, cameras that capture visible light are increasing in number of pixels of captured images, and an increase in the number of pixels is also required for a thermal image obtained by an infrared camera for temperature detection. As the number of pixels of the thermal image increases, the heat distribution of the monitoring target can be detected with such high accuracy. For example, with an increase in the number of pixels, it is possible to detect even a slight temperature change as conventionally missed.

  However, on the receiving terminal side that receives and analyzes the thermal image output from the temperature detection infrared camera, if the number of pixels of the thermal image increases, the amount of arithmetic processing for analyzing the thermal image increases accordingly. For example, when the thermal image is changed from the QVGA standard (horizontal 320 pixels × vertical 240 pixels) to the VGA standard (horizontal 640 pixels × vertical 480 pixels), the number of thermal image pixels in one frame becomes four times, and the amount of operation processing Will increase fourfold. Thus, when the amount of arithmetic processing increases, a high-performance terminal having a large amount of information processing is required as a receiving terminal (computer) for performing arithmetic processing, and it is assumed that the conventional terminal does not have sufficient capability.

  In addition, also for a transmission path for transmitting a thermal image signal from an infrared camera to a receiving terminal, it is necessary to cope with transmission of four-fold amount of information by changing from the QVGA standard to the VGA standard. Therefore, to improve the image quality of the infrared camera, it is necessary to take measures to increase the transfer rate also for the transmission path.

  If the transfer rate of the transmission path is not sufficient, for example, it is conceivable that the infrared camera compresses the thermal image data and transmits it to the receiving terminal. However, in the case of a lossless compression method in which data can be restored as it is on the receiving side, the compression rate is not very high and it is not very effective. In addition, when applying a non-reversible compression method with low recoverability on the receiving side, a high compression ratio can be obtained, but since the data restored on the receiving side contains an error, an incorrect temperature is detected at the receiving terminal. Therefore, there is a possibility of false alarm output or alarm leak. Furthermore, it is necessary to mount a thermal image data compression function on an infrared camera and a thermal image data restoration function on a receiving terminal, which is disadvantageous from the viewpoint of increased equipment cost, increased computational load, and increased processing delay.

  In addition, as another measure in the case where the transfer rate of the transmission path is not sufficient, measures such as transmitting only a partial range of the thermal image with the temperature detection infrared camera or reducing the frame rate of the thermal image may be considered. However, in either case, the ability of the temperature detection infrared camera is not utilized, which is not preferable.

  The present invention provides an infrared camera for temperature detection capable of obtaining a high-resolution thermal image and reducing the load on the terminal for acquiring and processing the high-resolution thermal image and the load at the time of transmission. With the goal.

The infrared camera for temperature detection according to the present invention calculates a representative value in a block unit of a predetermined number of pixels for the infrared sensor for capturing a thermal image of the first number of pixels and the thermal image captured by the infrared sensor. The representative value calculation unit includes an output unit that outputs a thermal image of the second number of pixels obtained by reducing the number of pixels.
Here, at least one block processed by the representative value calculation unit takes the maximum value or the minimum value in the block, or the difference between the maximum value and the minimum value as a representative value.

  According to the present invention, a thermal image in which the number of pixels is reduced can be output while making use of the high resolution of the thermal image captured by the infrared sensor. Therefore, it is possible to construct a system capable of monitoring with a high resolution thermal image while reducing the load on the terminal and the transmission path that analyze and process the thermal image.

It is a block diagram showing an example of composition of an infrared camera by one example of embodiment of the present invention. It is a figure which shows the pixel structural example (A: structural example of an imaging pixel, B: structural example of the pixel after representative value calculation) of the infrared camera by one embodiment example of this invention. It is a flowchart which shows the process example (example which outputs the maximum value or the minimum value) by one embodiment of this invention. It is a flowchart which shows the process example (example which outputs the difference of the maximum value and the minimum value) by one embodiment of this invention. It is explanatory drawing which shows the example of the thermal image by one embodiment of this invention.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as "this example") will be described with reference to the attached drawings.

[1. Configuration of Infrared Camera for Temperature Detection]
FIG. 1 shows a configuration example of the temperature detection infrared camera 10 of this embodiment.
The temperature detection infrared camera 10 of the present embodiment includes an infrared sensor 11, an infrared correction processing unit 12, a representative value calculation unit 13, an output unit 14, and a control unit 15.

The infrared sensor 11 is an infrared image sensor that acquires a thermal image in a pixel array (horizontal 640 pixels × vertical 480 pixels) of the VGA standard. The thermal image data acquired by the infrared sensor 11 is supplied to the infrared correction processing unit 12. Here, each pixel of the thermal image data acquired by the infrared sensor 11 is, for example, 16-bit data, and the infrared sensor 11 acquires thermal image data of 30 frames per second.
The infrared correction processing unit 12 performs correction processing for converting the thermal image data supplied from the infrared sensor 11 into thermal image data from which appropriate temperature information can be obtained. The thermal image data corrected by the infrared correction processing unit 12 is supplied to the representative value calculation unit 13.

  The representative value calculation unit 13 reduces the number of pixels of the thermal image data of the pixel array of the VGA standard, and converts it into thermal image data of the pixel array (horizontal 320 pixels × vertical 240 pixels) of the QVGA standard. Details of the representative value calculation process in the representative value calculation unit 13 will be described later. The thermal image data of the QVGA standard obtained by reducing the number of pixels by the representative value calculation unit 13 is supplied to the output unit 13.

  The output unit 13 outputs thermal image data of the QVGA standard to the outside of the temperature detection infrared camera 10. In the example of FIG. 1, the output unit 13 and the receiving terminal 20 are connected by a cable, and the thermal image data of QVGA standard is transmitted from the output unit 13 to the receiving terminal 20. When the infrared sensor 11 obtains thermal image data of 30 frames per second, the output unit 13 also outputs (transmits) thermal image data of 30 frames per second.

  When the output unit 13 and the receiving terminal 20 are connected by a network such as a LAN (Local Area Network), the output unit 13 is a communication interface compatible with the network. When thermal image data of the QVGA standard in which one pixel is composed of 16 bits is transmitted to the receiving terminal 20 at 30 frames per second, the transfer rate is 320 × 240 × 16 bits × 30 = about 37 Mbps. For example, in the case of a LAN, this can be transmitted using a device called "100 BASE" which can transfer up to 100 Mbps. In the case of transferring the thermal image of the VGA standard as it is, the transfer rate of 147 Mbps, which is four times as high, is required, and the transfer can not be performed by the LAN of the 100 BASE standard.

  The correction processing by the infrared correction processing unit 12, the representative value calculation processing by the representative value calculation unit 13, and the output processing by the output unit 14 are executed under the control of the control unit 15. For example, as representative value calculation processing in the representative value calculation unit 13, there are a plurality of processing modes, and it is determined by which mode the representative value calculation unit 13 performs representative value calculation processing by an instruction from the control unit 15. Do.

  The receiving terminal 20 receives the thermal image data transmitted from the temperature detection infrared camera 10, and analyzes and monitors the thermal image.

[2. Example of representative value calculation process]
Next, details of the representative value calculation process performed by the representative value calculation unit 13 will be described.
FIG. 2A shows a pixel array before the representative value calculation process, and FIG. 2B shows a pixel array after the representative value calculation process. 2A and 2B show X-coordinates in which the horizontal axis is horizontal coordinates, and Y-coordinates in which the vertical axis is vertical coordinates. Numbers in each square indicate pixel numbers. The pixel number is [. The numbers to the left of] indicate the x-coordinate, [. The numbers to the right of] indicate the Y coordinate.

  As a pixel array before the representative value calculation process which is a pixel array to be acquired by the infrared sensor 11, as shown in FIG. 2A, the first horizontal line (uppermost horizontal line) is a pixel of [1.1] , [2.1] pixels, [3.1] pixels,..., And the next horizontal line (second horizontal line) is the [1.2] pixel, [2.2] , [3.2],..., And so forth, the data of the pixels of each horizontal line are similarly arranged.

Here, in the present example, four adjacent pixels are treated as one block, and processing for calculating one pixel data serving as a representative value is performed for each block. That is, as shown by surrounding each pixel with a thick line in FIG. 2A, one block is formed by four pixels of (2 pixels in the X direction) × (2 pixels in the Y direction), and the representative value calculation unit 13 A representative value calculation process is performed so that only one pixel data is output for each block.
For example, as shown in FIG. 2B, the pixel [1.1] of the thermal image data subjected to the representative value calculation processing by the representative value calculator 13 is four pixels [1.1] and [2.1] shown in FIG. 2A. , And [1.2] and [2.2] to output one pixel data as a representative value.
Such representative value calculation processing in block units is performed to convert thermal image data of the VGA standard into thermal image data of the QVGA standard.

Next, a process of generating pixel data to be output after calculating the representative value when the representative value calculation process is performed in each block will be described.
The flowchart of FIG. 3 shows a processing example when the first processing mode is selected.
First, the representative value calculation unit 13 acquires data of four pixels of one block (step S11). Then, the representative value calculation unit 13 determines a pixel having the maximum pixel value (temperature) among the acquired four pixels of data (step S12).
When the maximum value is determined in step S12, the representative value calculation unit 13 sets the output value of the pixel of the block after calculation of the representative value as the determined maximum value (step S13). When the output pixel value of one block is determined in step S13, the representative value calculation unit 13 returns to the process of step S11 and proceeds to the process of the next block.

As described above, when the first processing mode is set, the representative value calculation unit 13 selects data of a pixel having a maximum value (maximum temperature) for each block, and outputs the selected pixel data.
In the example of FIG. 3, although the maximum value is determined and output for each block, the minimum value is determined for each block, and the data of the pixel having the minimum value (minimum temperature) is output. You may do it.

  In the first processing mode, the temperature detection infrared camera 10 effectively reduces the number of pixels of the thermal image to be output while making use of the high resolution of the thermal image acquired by the infrared sensor 11 be able to. That is, since the resolution of the thermal image is determined by the number of pixels of the infrared sensor 11, a thermal image with high resolution can be obtained by obtaining the thermal image of the VGA standard. For example, when only a very small range of temperatures becomes very high, that high temperature can be accurately detected in the thermal image.

  Then, when the representative value calculation unit 13 performs the representative value calculation processing, since the pixel of the maximum value is selected for each block, the high temperature detected by the infrared sensor 11 is output as it is. One pixel of the low resolution thermal image can be considered as an average of a plurality of pixels of the high resolution thermal image. Therefore, when the maximum value for each block is adopted as a representative value, as in the case of using a high resolution thermal image, a minute high temperature portion is output without being averaged. Therefore, the receiving terminal 20 performs monitoring using a QVGA standard thermal image, but monitoring of the temperature at the monitoring location is performed using the VGA standard thermal image as in the case of monitoring the high temperature maximum resolution. it can.

As described above, by setting the first processing mode, it is possible to monitor the temperature with high resolution by using the transmission path for transmitting the thermal image data and the conventional one as the receiving terminal 20 as it is. For example, in the case of transmitting QVGA standard thermal image data in which one pixel is composed of 16 bits as described above to the receiving terminal 20 at 30 frames per second, the transfer rate is approximately 37 Mbps, which is generally It is possible to transfer on a 100BASE standard LAN network, which is a used transmission system. In addition, the receiving terminal 20 also has the ability to monitor the thermal image of the VGA standard by the ability to monitor the thermal image of the QVGA standard, so that the ability to monitor the thermal image can be improved. .
When the temperature detection infrared camera 10 monitors that the place where the temperature is monitored is a low temperature, the representative value calculation unit 13 performs the representative value calculation process as the second processing mode. It is sufficient to select the pixel of the minimum value for each block.

Next, a processing example when the third processing mode shown in the flowchart of FIG. 4 is set will be described.
First, the representative value calculation unit 13 acquires data of four pixels of one block (step S21). Then, the representative value calculation unit 13 determines a pixel with the largest pixel value (temperature) and a pixel with the smallest pixel value (temperature) among the acquired four pixels of data (step S22).
Next, the representative value calculation unit 13 calculates the difference between the maximum value and the minimum value determined in step S22 (step S23). Then, the representative value calculation unit 13 sets the output value of the pixel of the block after the representative value calculation process as the value of the difference calculated in step S23 (step S24). When the output pixel value of one block is determined in step S24, the representative value calculation unit 13 returns to the process of step S21 and proceeds to the process of the next block.

  As described above, in the third processing mode, the representative value calculation unit 13 selects data of the difference between the maximum value and the minimum value for each block, and outputs pixel data of the selected difference value.

In this third processing mode, the thermal image data output from the temperature detection infrared camera 10 shows the maximum temperature difference of each block. Therefore, in the receiving terminal 20, each block (each output pixel) The monitoring of the temperature difference of the can be done well with high resolution.
FIG. 5 shows an example of the monitoring state when the third processing mode is applied. Here, the high temperature location H exists in the thermal image P1, and the receiving terminal 20 accurately detects the edge portion (outline) of the high temperature location H, and to which coordinate position is the high temperature location H It is to monitor.

When monitoring in such an application, by setting the third processing mode, as shown in FIG. 5, for example, the representative value pixel of the block b1, the representative value pixel of the block b2,. Is obtained, the block b3 which has detected the heat of the edge portion of the high temperature portion H becomes the maximum temperature difference.
Therefore, in the receiving terminal 20 that receives the thermal image data with the reduced number of pixels, the edge portion of the high temperature portion H can be detected by the resolution of the original thermal image obtained by the temperature detection infrared camera 10.

[3. Modified example]
In the embodiment described above, it is an example that the thermal image obtained by the temperature detection infrared camera 10 is the pixel number of the VGA standard, and the thermal image output after the representative value calculation process is the pixel number of the QVGA standard. The temperature detection infrared camera 10 may obtain a thermal image of another number of pixels. The point of reducing the number of pixels to 1⁄4 is also an example, and may be reduced to other numbers of pixels.

The number of pixels in one block may also change. In the embodiment described above, four pixels (two horizontal pixels × two vertical pixels) are used as the number of pixels in one block when performing the representative value calculation process. Making these two pixels into one block is an example, and one block may be configured by the other number of pixels, and representative value calculation processing may be performed on a larger block.
Specifically, it can be generalized as a block composed of N pixels × M pixels (N and M are arbitrary integers) as a block of a unit of representative value calculation processing. Note that when one block is configured by N pixels × M pixels, pixels that can not be divided by the block are not cut off, and may be set as independent minute regions.

Further, the frame rate of 30 frames per second shown in the above-described embodiment is also an example, and the present invention can be applied to the case of obtaining a thermal image at other rates.
Furthermore, in the above-described embodiment, the same representative value calculation process is performed for all blocks, but different representative value calculation processes may be performed for each block. That is, for example, it is possible to select the maximum value in one block of a certain thermal image, select the minimum value in another block, and select the difference between the maximum value and the minimum value in another block.
In addition, if a representative value calculation process is performed using the maximum value or the minimum value or the difference between the maximum value and the minimum value for a partial area (an area including at least one block) in the image, the area Other representative value calculation processes may be applied to the other parts. Other representative value calculation processing may include pixel values at fixed positions in the block, average values, median values, and the like. That is, for example, one block selects a maximum value in a certain thermal image, another selects a minimum value in another block, and a representative value different from the maximum value, the minimum value, and the difference between the maximum value and the minimum value in another block. It may be possible to select
The selection of the representative value calculation process in each block may be configured to be changed by setting in the control unit 15.

  10: infrared camera for temperature detection, 11: infrared sensor, 12: infrared correction processing unit, 13: representative value calculation unit, 14: output unit, 15: control unit, 20: receiving terminal, P1: thermal image, H ... hot spot

Claims (2)

An infrared sensor for capturing a thermal image of a first number of pixels;
A representative value calculation unit that calculates a representative value in block units of a predetermined number of pixels for a thermal image captured by the infrared sensor;
An output unit for outputting a thermal image of the second number of pixels, wherein the representative value calculation unit reduces the number of pixels;
The temperature detection infrared camera, wherein at least one block processed by the representative value calculation unit has a maximum value or a minimum value in the block, or a difference between the maximum value and the minimum value as a representative value. The representative value calculation unit is configured to set the block of the specific area with respect to the block other than the specific area subjected to the processing using the maximum value, the minimum value, or the difference between the maximum value and the minimum value in the block as a representative value. The temperature detection infrared camera according to claim 1, wherein the representative value is calculated by a representative value calculation process different from the representative value calculation process performed for.

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