High-speed temperature data output method for measurement points in two-dimensional images using the 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] Temperature measurement device using two-color temperature method that can measure the temperature of heat-generating workpieces [Background technology]

[0002] Conventionally, when measuring the temperature of a heating element non-contact and at high speed, temperature data at the measurement point is 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 this method does not allow for real-time temperature data output. 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] When measuring a heat source using a radiation thermometer, it is difficult to confirm the measurement position and multiple measurements cannot be taken simultaneously. It is necessary to set the emissivity each time.

[0006] When using a 2D 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 them difficult to perform during the manufacturing process. Measurements at multiple points require installation wiring, which requires setup work each time. [Effects of the Invention]

[0008] Using a high frame rate 2D image sensor and displaying images in real time makes it possible to grasp the entire view of the heat-generating body. As a result, it is possible to narrow down the measurement points arbitrarily, which means that temperature calculations can be performed only at those measurement points, eliminating the need to calculate at points where calculations were previously unnecessary. As a result, the number of temperature calculations can be reduced, making it possible to achieve higher speeds than current temperature measurement methods.

[0009] Compared to conventional technology, other advantages 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 the ability to not only record temperature data but also output it to a sequencer or logger in real time so that it can be used to control heating equipment.

[0010] As a result, high-precision temperature data can be obtained by processing using the two-color temperature method, and by measuring and outputting the temperature of products during processing or heat treatment at high speed, feedback control to processing equipment or heating equipment becomes possible, enabling the production of products with stable quality. It also contributes to cost reduction and energy saving by reducing defective products and unnecessary heating. [Brief explanation of the drawings]

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

[0012] Hereinafter, 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 will be assigned the same numbers throughout the embodiments.

[0013] Although the following embodiments mainly focus on the method, it will be apparent to those skilled in the art that the present invention can also 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 matches the position of the pixels of the image sensor.

[0014] The invention of this application uses a high-frame-rate two-dimensional image sensor and displays images in real time, allowing for a complete view of the heating element, multiple measurement points or measurement areas to be specified on the image, and temperature calculations are performed only at those measurement points or measurement areas, speeding up temperature calculations. Furthermore, by halting image display updates while temperature data is being output, processing is sped up, allowing for the output and recording of temperature data from multiple measurement points on a two-dimensional image at high speed in real time. Furthermore, the use of the two-color temperature method reduces the effects of emissivity, enabling highly accurate temperature measurements (Figure 2).

[0015] First, the concept of the two-color temperature method is to measure the temperature of high-temperature workpieces above 300°C without contact by measuring the electromagnetic radiation emitted by the object and calculating the temperature from its intensity. This method is commercially available as a radiation thermometer, which obtains temperature from visible or infrared light, or as a thermograph, which measures temperature distribution. Measurement targets are generally non-black bodies, and to obtain true temperature from a radiation thermometer or a thermograph, correction must be made for 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 closely spaced wavelengths is the same. Since the ratio of the amounts of radiation at the two wavelengths is functionally related to the true temperature, the amount of radiation at the two wavelengths is measured and the true temperature is calculated.

[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 Woon's approximation formula, if the radiant energy at two wavelengths λ1 and λ2 is M1 and M2, the emissivity is ε1 and ε2, the transmittance is τ1 and τ2, and the conversion efficiency of the sensor etc. is 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 become ε1 = ε2, τ1 = τ2, and β1 = β2, and the emissivity ε, transmittance τ, and conversion efficiency β are eliminated, and it is known that the ratio of the radiation amounts is a function of the temperature.

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[0020] Even if the emissivity at two wavelengths or the transmittance of an inclusion differs, 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, regarding image sensors for two-color temperature measurement, traditionally, two sets of light-receiving sensors that receive light of different specific wavelengths are prepared by attaching bandpass filters to the photodiodes, and two-color temperature measurement is performed by calculating their outputs using equations 1 to 5. However, obtaining the temperature distribution of a product, etc., requires multiple sets of sensors, which complicates control and increases costs. Noting that camera sensors such as CCD and CMOS have photodiodes arranged in a compound configuration, it was devised to apply this to two-color temperature measurement (Patent Publication No. 4378003). While conventional cameras intentionally make the electrical output in response to incident light nonlinear, here it is necessary to use a camera that emphasizes linearity.

[0022] Two methods for obtaining images of the distribution of radiation at two wavelengths include using two cameras with bandpass filters attached to the front of the sensor or the objective lens, or using a camera with λ1 and λ2 filters attached to each pixel in a mosaic pattern in front of the sensor. Single-chip color cameras with red, green, and blue filters attached to the sensor in a mosaic pattern are widely used in both consumer and industrial applications, and a two-color temperature measurement device using this has been disclosed as Patent No. 4378003. A sensor with two near-infrared wavelength filters attached in a mosaic pattern has also been devised for measuring relatively low temperatures (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, illustrating its structure. 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 the values ​​of the surrounding signals of other wavelengths. In the example in Figure 3, the second pixel from the left and 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 it, and dividing the result by four. This obtains the amount of radiation at two wavelengths. This means that only one piece of radiation reception-related hardware is required, and although the color (wavelength) resolution is halved, it enables significant cost reductions. This advantage makes it widely used in consumer color cameras.

[0024] Image sensors such as CCDs and C-MOSs are constructed by arranging photodiodes in a matrix on a silicon or indium-gallium-arsenide substrate. These photodiodes are subject to significant drift due to ambient temperature. When two cameras are used to receive radiation at two wavelengths in two-color thermometry, complex control is required to prevent the ratio between the two cameras from drifting due to changes in ambient temperature, resulting in a complex configuration. In contrast, when using a mosaic filter camera, the temperature drift of the radiation output at both wavelengths is the same, and the drift value is eliminated when calculating the ratio, offering the significant advantage of eliminating the need for complex drift control configurations.

[0025] In this invention, by using a 2D image sensor, it is possible to grasp the entire view of the heating element without contact, and by calculating the temperature of multiple measurement points or only the measurement area, it is possible to output temperature data at high speed. This solves the problems of conventional radiation thermometers, which cannot confirm the position of the measurement point on the image and can only measure one point, and the 2D image sensor method, which cannot output temperature data at high speed in real time, and the fact that thermocouples must be in contact with the heating element, which requires time and effort for installation and wiring.

[0026] Figure 4 shows an image captured by a camera equipped with a mosaic filter sensor for the two-color temperature method. The camera image is displayed on a monitor, allowing users to set multiple measurement points or measurement areas at any desired location while viewing the image. Because the mosaic filter and the camera's image sensor are aligned, users can specify any measurement point or measurement area on the image and obtain the temperature at the specified location using the two-color temperature method. By not calculating the temperature of measurement points other than the specified location, the number of two-color temperature calculations can be reduced compared to measuring the entire displayed image, thereby shortening the temperature measurement time. This also reduces the amount of output data compared to outputting all pixel data. This allows the time required for the computer to receive the camera image to be the same as the time required for temperature calculation and data output, enabling real-time data output.

[0027] Figure 5 shows the camera image when temperature data is being output. To speed up temperature measurement, the camera image is not displayed; 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, making it possible to output temperature data 30-50 times faster than before.

[0028] By performing two-color temperature processing from the output data from the measurement area, which is 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 calculation, and it is possible to achieve faster processing than when two-color temperature processing is performed 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 that results from the calculation is recorded on the computer, or sent directly as digital data or as analog current or voltage signals via a DA converter (digital-to-analog converter) connected to the computer to a sequencer or logger.

Claims

1. A temperature measurement device for measuring the temperature of a heating element using a camera equipped with a two-dimensional image sensor with a high frame rate for enabling real-time observation of images, and a mosaic filter attached to the two-dimensional image sensor and configured to correspond to red, green, and blue, or to correspond to two wavelengths of near-infrared, so that pixels corresponding to red, green, and blue alternate, or pixels corresponding to two wavelengths of near-infrared alternate, a temperature measurement means using a two-color temperature method for measuring temperature by displaying an image of the heating element taken by the camera in real time, allowing the user to grasp the entire view of the heating element, and then narrowing down the measurement points or measurement areas to only one or more measurement points or measurement areas arbitrarily designated by the user, and not measuring temperatures at positions other than the designated positions so as to reduce the output data of the camera for faster temperature measurement processing, and by controlling to stop updating the display of the image of the heating element while temperature data is being output; a means for displaying, recording, or simultaneously outputting to an external device in real time the temperature data measured at only the one or more specified measurement points or measurement areas and the one or more specified measurement points or measurement areas so that a user can recognize the correspondence between them within the image of the heating element; A temperature measuring device comprising:

2. The temperature measuring device described in claim 1, characterized in that when the means for performing either of the above displays the measured temperature data of only the one or more specified measurement points or measurement areas together with only the one or more specified measurement points or measurement areas, it also displays an image of the heating element captured by the camera.

3. The temperature measuring device described in claim 1, characterized in that when the means for performing either of the above displays the measured temperature data of only the one or more specified measurement points or measurement areas together with only the one or more specified measurement points or measurement areas, the image of the heating element captured by the camera is not displayed.

4. A temperature measurement device as described in claim 2 or 3, characterized in that a plurality of measurement points or measurement areas to be targeted for the temperature data are specified, a plurality of temperature data are measured simultaneously, and the measured temperature data is displayed together with only the specified plurality of measurement points or measurement areas.

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