High-speed temperature data output method for measurement point in two-dimensional image using two-color temperature method

Abstract

To provide a temperature measuring device using a two-color temperature method capable of measuring the temperature of a heat-generating workpiece.SOLUTION: By using a two-dimensional image sensor with a high frame rate and displaying an image in real time, the whole view of a heating body can be grasped, and multiple measurement points or areas can be specified on the image arbitrarily. Temperature calculation is accelerated by performing temperature calculation only for the measurement points or areas, and further, processing is accelerated by stopping update of the image display while temperature data is being output. This enables outputting and recording the temperature data of the multiple measurement points of the two-dimensional image at high speed in real time. In addition, by using the two-color temperature method, the effect of emissivity is reduced, and highly accurate temperature measurement can be performed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] A temperature measuring device using a two-color temperature method that can measure the temperature of a heat-generating workpiece [Background technology]

[0002] Conventionally, when measuring the temperature of a heating element non-contact and at high speed, temperature data at the measurement point was obtained using a radiation thermometer or the like. Another method is to use a high frame rate thermography to record images at high speed and calculate the temperature offline, but it is not possible to output temperature data in real time. In addition, it is necessary to set the emissivity according to the heating element when calculating the temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2001-157214 [Patent Document 2] Patent Publication No. 2020-038107 [Patent Document 3] Patent Publication No. 2021-060325 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional measurement methods had the following issues:

[0005] It is difficult to confirm the measurement position when measuring a heat source using a radiation thermometer, and multiple measurements cannot be taken at the same time. It is necessary to set the emissivity each time.

[0006] When using a two-dimensional image sensor, it is not possible to output temperature data in real time at high speed, and it is necessary to set the emissivity each time.

[0007] Measurements using thermocouples require contact with the heating element, making it difficult to perform measurements during the manufacturing process, and measurements at multiple points require installation wiring, which requires setup work each time. Effect of the Invention

[0008] By using a two-dimensional image sensor with a high frame rate and displaying images in real time, it is possible to grasp the entire view of the heating body. As a result, it is possible to narrow down the measurement points arbitrarily, which means that temperature calculations are performed only at those measurement points, and calculations at points where calculations are not necessary are not required. As a result, the number of temperature calculations can be reduced, making it possible to increase the speed compared to current temperature measurement methods.

[0009] Other advantages over conventional technologies include the ability to record and output temperature data from multiple specified points at high speed, the use of a two-dimensional image sensor means that measurement points can be specified while checking the image, the use of a two-color temperature method means that highly accurate temperature measurements can be made, and in addition to recording temperature data, the data can be output in real time to a sequencer or logger so that it can be used to control heating equipment.

[0010] As a result, highly accurate temperature data can be obtained by processing with the two-color temperature method, and the temperature of the product being processed or heat-treated can be measured and output at high speed, enabling feedback control to the processing equipment or heating equipment, making it possible to manufacture products with stable quality. It also contributes to cost reduction and energy saving by reducing defective products and unnecessary heating. [Brief description of the drawings]

[0011] [Figure 1] Obtain temperature data at measurement points using a radiation thermometer, etc. [Diagram 2] 2D image sensor camera for two-color temperature measurement [Diagram 3] As an example of the structure of a sensor with a mosaic filter, here is an example of a sensor with a mosaic filter. [Figure 4]Image showing the camera image of the heating element displayed on a monitor, along with the measurement point or area and temperature. [Diagram 5] An image showing the temperature of a specified measurement point or area without displaying the image of the heating element on the monitor. [Figure 6] Temperature data output method concept diagram DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention can be implemented in many different forms, and should not be interpreted as being limited to the description of the present embodiment. Note that the same elements are designated by the same numbers throughout the embodiments.

[0013] In the following embodiments, the method will be mainly described, but it will be obvious to those skilled in the art that the present invention can be embodied in an image sensor structure with a mosaic filter using the two-color temperature method, provided that the position of the mosaic filter coincides with the position of the pixels of the image sensor.

[0014] The invention of this application uses a two-dimensional image sensor with a high frame rate, and by displaying the image in real time, it is possible to grasp the whole view of the heating body, and multiple measurement points or measurement areas can be specified on the image at will, and temperature calculation is accelerated by calculating the temperature only at those measurement points or measurement areas, and furthermore, processing is accelerated by stopping the updating of the image display while the temperature data is being output, thereby achieving the output and recording of temperature data from multiple measurement points on a two-dimensional image at high speed in real time.In addition, by using the two-color temperature method, the effects of emissivity are reduced, enabling highly accurate temperature measurement (Figure 2).

[0015] First, the concept of the two-color temperature method is that in order to measure the temperature of a high-temperature workpiece above 300°C without contact, the electromagnetic radiation emitted from the measurement object is measured and the temperature is calculated from its intensity. This method is commercialized as a radiation thermometer that obtains temperature from visible or infrared light, and as a thermograph that measures temperature distribution. The measurement object is generally a non-black body, and in order to know the true temperature from a radiation thermometer or from a thermograph, it is necessary to correct for the emissivity, which is the ratio of the amount of radiation to that of a black body. However, the emissivity of a non-black body generally varies depending on its material, shape, and temperature, making it difficult to obtain an accurate temperature. Therefore, the two-color temperature method is used. The two-color temperature method focuses on the fact that the emissivity of radiation at two adjacent wavelengths is the same, and since the ratio of the amount of radiation at the two wavelengths is functionally related to the true temperature, it measures the amount of radiation at the two wavelengths and calculates the true temperature.

[0016] The radiation utilization at wavelength λ is given by Planck's radiation formula:

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[0017] If the emissivity of the object is ε and the transmittance from the object to the measurement system is τ, then

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[0018] Applying Woorn's approximation formula, if the radiant energy at two wavelengths λ1 and λ2 is M1 and M2, the emissivity ε1 and ε2, the transmittance τ1 and τ2, and the conversion efficiency of the sensor etc. β1 and β2, then the two wavelength ratio R at wavelengths λ1 and λ2 is,

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[0019] By bringing the two wavelengths of radiation close together, the emissivities ε1 = ε2, τ1 = τ2, and β1 = β2 become true, and the emissivity ε, transmittance τ, and conversion efficiency β are eliminated. It is known that the ratio of the amounts of radiation is a function of temperature.

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[0020] Even if the emissivity at two wavelengths or the transmittance of an inclusion are different, if the ratio does not change with temperature, the true temperature of an object whose temperature changes can be determined by correcting the ratio with a black body.

[0021] Next, as for the image sensor for the two-color temperature method, conventionally, two sets of light receiving sensors that receive light of different specific wavelengths are prepared by attaching a bandpass filter to the photodiode, and two-color temperature measurement is performed by calculating the output of the two sets of sensors according to Equations 1 to 5. However, in order to obtain the temperature distribution of a product, etc., multiple sets of sensors are required, which makes the control complicated and increases the cost. It was devised to apply the fact that camera sensors such as CCD and CMOS have photodiodes arranged in a compound eye to two-color temperature measurement (Patent Publication No. 4378003). In general cameras, the electrical output in response to the incident light is intentionally made non-linear, but here it is necessary to use a camera that emphasizes linearity.

[0022] There are two ways to obtain a distribution image of radiation at two wavelengths: using two cameras with bandpass filters attached to the front of the sensor or the front of the objective lens, or using a camera with λ1 and λ2 filters attached to the front of the sensor in a mosaic pattern, alternating for each pixel. Single-chip color cameras with red, green, and blue filters attached to the sensor in a mosaic pattern are widely used for consumer and industrial purposes, and a two-color temperature measurement device using this has been published as Patent No. 4378003. A sensor with two near-infrared wavelength filters attached in a mosaic pattern for measuring relatively low temperatures has also been devised (Patent Application No. 2018-165055). Here, λ1 is the first wavelength filter, and λ2 is the second wavelength filter.

[0023] Figure 3 shows an example of a sensor with a mosaic filter as the structure of a sensor with a mosaic filter. Each pixel receives light passing through only the first or second wavelength. Signals of other wavelengths that a pixel cannot receive are output by calculating and processing the values ​​of the surrounding signals of other wavelengths. In the example of Figure 3, the second pixel from the left and the second pixel from the top cannot receive signals of the second wavelength, so the value of its own second signal is calculated by adding the values ​​of the four signals of the second wavelength to the left, right, and above and below itself and dividing the result by four. This means that the amount of radiation of two wavelengths is obtained. This means that only one piece of hardware related to radiation reception is required, and although the color (wavelength) resolution is halved, it is possible to significantly reduce costs. This advantage makes it widely used in consumer color cameras.

[0024] Image sensors such as CCD and C-MOS are constructed by arranging photodiodes in a matrix on a silicon or indium-gallium-arsenide substrate. These photodiodes are affected by the ambient temperature and drift significantly. When trying to receive radiation amounts of two wavelengths with two cameras in two-color thermometry, a complicated configuration is required to control the ratio of the two cameras so that it does not drift due to changes in the ambient temperature. In contrast, when configured with a mosaic filter type camera, the temperature drift of the radiation output at both wavelengths is the same value, and the drift value is eliminated when the ratio is calculated, which has the great advantage of eliminating the need for a complicated drift control configuration.

[0025] In the present invention, by using a two-dimensional image sensor, it is possible to grasp the entire view of the heating element without contact, and by calculating the temperature of only multiple measurement points or the measurement area, it is possible to output temperature data at high speed, solving the problems of the past, that with a radiation thermometer, the position of the measurement point cannot be confirmed on the image and there is only one measurement point, that with the two-dimensional image sensor method, temperature data cannot be output in real time at high speed, and that with a thermocouple, it is necessary to make contact with the heating element, and installation wiring requires time and effort.

[0026] Figure 4 shows an image of a camera using a sensor with a mosaic filter used for the two-color temperature method. The camera image is displayed on a monitor, and multiple measurement points or measurement areas can be set at any location while checking the image. Since the positions of the mosaic filter and the image element of the camera are aligned, it is possible to specify any measurement point or measurement area from the image and obtain the temperature at the specified location using the two-color temperature method. In addition, by not calculating the temperature of measurement points other than the specified position, it is possible to reduce the number of calculations for the two-color temperature method compared to measuring the entire displayed image, and as a result, the temperature measurement time can be shortened. As a result, the output data can be reduced compared to when all pixel data is output, and the time it takes for the computer to receive the camera image, calculate the temperature, and output the data can be made equal, making it possible to output data in real time.

[0027] Figure 5 shows the camera image when temperature data is output. To speed up temperature measurement, the camera image is not displayed, and only the measurement point or measurement area and its temperature are displayed. By limiting the temperature calculation to a specified point or measurement area and not displaying the camera image, it is possible to reduce the amount of output data, and it is possible to output temperature data 30-50 times faster than before.

[0028] By performing two-color temperature processing on the output data from the measurement area using the sum of the output data of the first wavelength of the pixels in this area and the sum of the output data of the second wavelength, it is possible to reduce the amount of calculations, making it possible to increase speed compared to performing two-color temperature processing on each measurement point one by one.

[0029] Figure 6 is a conceptual diagram of the temperature data output method. The image captured by the camera is sent to a computer, and the temperature is calculated using the two-color temperature method. The temperature data resulting from the calculation is recorded in the computer, or sent to a sequencer or logger as direct digital data or as analog current or voltage signals by a DA converter (digital-to-analog converter) connected to the computer.

Claims

1. A temperature measuring device for measuring the temperature of a heating element, comprising: a camera including a two-dimensional image sensor and a mosaic filter attached to the two-dimensional image sensor so that pixels corresponding to a first wavelength and pixels corresponding to a second wavelength different from the first wavelength are alternated; A temperature measuring means using a two-color temperature method for measuring temperature only at one or more measurement points or measurement areas arbitrarily designated in the image of the heating element captured by the camera; a means for displaying, recording, or simultaneously outputting to an external device the temperature data measured at the one or more designated measurement points or measurement areas together with the one or more designated measurement points or measurement areas; A temperature measuring device comprising:

2. A temperature measuring device as described in claim 1, characterized in that in order to speed up temperature measurement, temperature is measured from the sum of the outputs of the first wavelength and the sum of the outputs of the second wavelength of pixels at the specified one or more measurement points or measurement areas.

3. The temperature measuring device described in Claim 1, characterized in that the mosaic filter corresponds to different wavelengths of red, green, and blue, or to two near-infrared wavelengths, and is attached to the two-dimensional image sensor in a mosaic pattern.

4. A temperature measuring device as described in claim 1, characterized in that updating of the image display is stopped while the temperature data is being output.

5. A temperature measuring device as described in any one of claims 1 to 4, characterized in that when the means for performing any of the above displays an image of the heating element captured by the camera together with the specified one or more measurement points or measurement areas.

6. A temperature measuring device as described in any one of claims 1 to 4, characterized in that when the means for performing any of the above displays the image of the heating element captured by the camera together with the specified one or more measurement points or measurement areas, the image is not displayed.

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