Synchronous signal detection unit and temperature measurement device using the same

Abstract

Provided are a synchronization signal detection unit capable of detecting a synchronization signal without providing a mark for forming a synchronization signal on a rotating plate having a filter region, and a temperature measurement device using the same. **Solution means**: As a synchronization signal detection unit, one or more sets of a first filter and a second filter having different spectral transmission characteristics are provided in the circumferential direction. For a rotating plate without a mark for forming a synchronization signal, a light source on one side, a light receiving sensor on the other side, sandwiching the rotating plate, and a third filter provided in the optical path from the light source to the light receiving sensor, or provided on the light receiving sensor itself or the light source itself, having the same spectral transmission characteristics as the first filter or the second filter. Based on the comparison between the first output of the light receiving sensor through the first filter and the third filter and the second output of the light receiving sensor through the second filter and the third filter, a synchronization signal on the rotating plate is detected.

Description

Technical Field

[0001] The present invention relates to a synchronous signal detection unit capable of detecting a synchronous signal and a temperature measurement device using the same, which include, as a filter region, one or more sets of a first filter and a second filter having different spectral transmission characteristics in the circumferential direction, for a rotating plate without a mark for forming a synchronous signal.

Background Art

[0002] As a temperature measurement device, there is known one using a two-color temperature method for converting temperature from the ratio of radiance using two different wavelengths close to each other. Among various specific methods using the two-color temperature method, there is known one that includes a first filter and a second filter having different spectral transmission characteristics in the filter region of a rotating plate in the optical path from the measurement object to the sensor and measures temperature at low cost (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in Patent Document 1, the rotating plate includes a mark for forming a synchronous signal together with a plurality of filter regions. Specifically, it is considered that the edge of the transmission window in the circumferential direction of the rotating plate corresponds to the mark for forming the synchronous signal. When the rotating plate is provided with the mark for forming the synchronous signal in this way, there is an inconvenience that the filter region other than the mark for forming the synchronous signal inevitably becomes narrow.

[0005] An object of the present invention is to provide a synchronous signal detection unit capable of detecting a synchronous signal without providing a mark for forming a synchronous signal on a rotating plate having a filter region, and a temperature measurement device using the same.​

Means for Solving the Problem

[0006] The synchronization signal detection unit according to the present invention includes, as a filter region, one or more sets in the circumferential direction of a first filter and a second filter having different spectral transmission characteristics, and is a synchronization signal detection unit for a rotating plate not provided with a mark for forming a synchronization signal, a light source provided on one side sandwiching the filter region on the rotating plate, a light receiving sensor provided on the other side, and provided in the optical path from the light source to the light receiving sensor, or provided on the light receiving sensor itself or the light source itself, and having a third filter having the same spectral transmission characteristics as the first filter or the second filter, and detecting a synchronization signal on the rotating plate based on a comparison between a first output of the light receiving sensor via the first filter and the third filter and a second output of the light receiving sensor via the second filter and the third filter.

[0007] Further, the temperature measuring device according to the present invention includes the above synchronization signal detection unit, the rotating plate, a second light receiving sensor that receives light radiated from the measurement target and measures the temperature of the measurement target, and the first light via the first filter from the measurement target to the second light receiving sensor and the second light via the second filter are time-sequentially guided to the second light receiving sensor via the rotating plate, and is characterized by having a light guiding means.

Advantages of the Invention

[0008] According to the present invention, since the rotating plate having a filter region is not provided with a mark for forming a synchronization signal, a wider filter region can be adopted.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] (First Embodiment) Prior to the specific description of this embodiment, first, the two-color temperature measurement method will be described.

[0012] (Two-Color Temperature Measurement Method) Hereinafter, the concept of the two-color temperature measurement method will be described. In order to measure the temperature of a high-temperature workpiece of 300 °C or higher non-contact, the electromagnetic radiation emitted from the measurement target is measured, and the temperature is calculated from its intensity. As a commercialized product, there is a radiation thermometer that obtains the temperature from visible light or infrared light, and there is thermography for measuring the temperature distribution. Since a general measurement target is a non-blackbody, in order to know the true temperature from a radiation thermometer and the true temperature from thermography, correction must be made with the emissivity, which is the ratio of the radiation amount to that of a blackbody. However, since the emissivity of a non-blackbody generally varies depending on its material, shape, and temperature, it is difficult to obtain an accurate temperature.

[0013] Therefore, the two-color thermometer method is used. The two-color thermometer method focuses on the fact that the emissivities of radiation at two adjacent wavelengths are the same, and since the ratio of the radiation amounts at the two wavelengths has a functional relationship with the true temperature, the radiation amounts at the two wavelengths are measured to calculate the true temperature. Explained using mathematical formulas, it is as follows.

[0014] Wien's radiation formula for the radiation amount Mλ at wavelength λ is as follows.

[0015]

Equation

[0016] Here, c1: First radiation constant = 2πc2h = 3.741844X10-16 [Wm2] λ: Wavelength μm c2: Second radiation constant = 1.438769X10-2 [m K] T: Absolute temperature (Kelvin) For the two wavelengths λ1 and λ2 to be measured, with emissivities ε1 and ε2 respectively, and the radiation amounts of both being M1 and M2, and the ratio of the radiation amounts at both wavelengths (output ratio in the image sensor) being R, then R is expressed by equation (2).

[0017]

Equation

[0018] When the condition ε1 = ε2 is satisfied, equation (2) becomes equation (3).

[0019]

Equation

[0020] When both sides are arranged, the temperature T is obtained by equation (4).

[0021]

Equation

[0022] Here, C3 and C4 are constants calculated from both wavelengths and are expressed by the following equations.

[0023]

Equation

[0024] Even when the emissivities and the transmissivities of the inclusions at two wavelengths are different, if their ratio does not change with temperature, the true temperature of an object with a changing temperature can be known by correcting the ratio to a black body.

[0025] (Temperature measurement by the rotating filter method) FIG. 1 shows an overall configuration diagram of a temperature measurement apparatus according to an embodiment of the present invention, which is composed of a measurement head and a computer. The measurement head is provided with an objective lens 1, a rotating filter 2, an image sensor unit 3, a wavelength-specific image distribution circuit 4, an image addition / non-addition processing circuit 5, a memory bank 6, a trigger light source 8, a trigger sensor 9, and a motor 10 for rotating the rotating filter 2 at a constant speed. At least the computer 7 that performs exposure time indication and two-color temperature processing is provided with computer hardware / software. The image sensor unit 3 is provided with an image sensor 3a (a second light receiving sensor different from the trigger sensor 9), an analog amplifier 3b, and an A / D conversion element 3c.

[0026] Regarding these members, those with the same reference numerals are shown in the block diagram of FIG. 2.

[0027] In this embodiment, in order to reduce costs, the rotating filter 2 is provided as a rotating plate between the objective lens 1 and the image sensor 3a. The rotating filter 2 is provided with a first filter region and a second filter region through which first light and second light having different wavelengths pass as band-pass filters, respectively, and these regions are adjacent to each other in the rotation direction, and a plurality of sets of such combinations are provided in the rotation direction.

[0028] In Fig. 3(a), the filter is divided into four parts, and two sets of a first filter 12 and a second filter 13 are provided. In Fig. 3(b), the filter is divided into twenty parts, and ten sets of a first filter 22 and a second filter 23 are provided.

[0029] In the conventional two-color thermometer, the measurement target is one-dimensional point measurement of one point or one area, whereas in this embodiment, an image sensor is used and the measurement targets a large number such as 300,000 points (640 x 480).

[0030] Furthermore, while the conventional two-color thermometer depends on analog signal processing with floating elements for temperature measurement from the radiation ratios of two wavelengths, in this embodiment, temperature calculation processing for each of about 300,000 pixels can perform accurate numerical processing based on Wien's radiation law.

[0031] In such an embodiment, the image sensor 3a is a single image sensor with a global shutter that has pixels two-dimensionally and each pixel is simultaneously exposed to output a digital signal. The global shutter method is adopted because when performing dynamic imaging with the rotating filter 2 intervening, it is preferable that each pixel is simultaneously exposed to output a digital signal.

[0032] An image of the measurement target is captured by the image sensor 3a through a band-pass filter configured on the rotating plate of the rotating filter 2 by the objective lens 1. In this way, the objective lens 1 functions as a light guiding means for guiding the first light and the second light from the measurement target to the image sensor 3a in a time series through the rotating filter 2. As the light guiding means, a glass fiber image transmission tube (image guide fiber) may be provided on the focal plane of the objective lens, and a lens may be arranged at the tip of the image transmission tube again to construct a system for transmitting to the image sensor through the filter rotating plate, thereby avoiding stray light around the measurement target and performing temperature measurement.

[0033] Here, prior to temperature measurement, the computer 7 instructs the image sensor unit 3 to set the exposure time, and the image sensor 3a can set the exposure time for the global shutter function.

[0034] Then, in the image sensor unit 3, after the output of each pixel of the image sensor 3a is amplified by the analog amplifier 3b, it is sent to the wavelength - specific image distribution circuit 4 as digital data such as 12 - 16 bits by the A / D converter 3c. And it is stored in each wavelength region of the memory bank 6 as an image of the wavelength identified by the trigger signal which is the output of the trigger light - receiving sensor 9 (Fig. 2).

[0035] Regarding data reading, the image addition / non - addition processing circuit 5 reads the data of two pairs of necessary wavelengths from the memory bank 6, and according to the command from the computer 7, after adding or not adding the data of each pixel, it outputs to the computer 7. Then, the computer 7 performs two - color temperature processing on the non - added or added image data, and then outputs a signal for display or control.

[0036] Regarding the image addition in the image addition / non - addition processing circuit 5 as the output addition unit, when the rotation speed of the rotating plate of the rotation filter 2 is P rotations per second (RPS) and the filter division number is Q, when the required exposure time is longer than 1 / (P×Q) seconds, the two pairs of memory numerical values read from the memory bank 6 are added (Fig. 7). For example, when the rotation speed of the rotating plate of the rotation filter 2 is 2400 RPM (40 rotations per second) and the filter division number is 4 (the rotating plate is divided into 4 parts), the exposure time per wavelength is 1 / 40×1 / 4×1000 = 6.25 milliseconds (msec), but by adding two images per wavelength, the exposure time per wavelength can be extended to 12.5 milliseconds (msec).

[0037] In this embodiment, when the measurement target is on the low-temperature side (for example, less than 500 °C), since the amount of radiant light from the measurement target is small, a rotating plate with a small number of filter divisions is rotated at a low speed so as to increase the exposure amount to the imaging sensor. Furthermore, by performing the image addition process shown in FIG. 6, the output of the output addition unit can be used to increase the sensor output.

[0038] On the other hand, when the measurement target is on the high-temperature side (for example, 500 °C or higher), a rotating plate with a large number of filter divisions is rotated at a high speed. Then, by performing the addition average process of the image addition shown in FIG. 6, the addition average of the output of the output addition unit can be used to improve the temperature measurement accuracy.

[0039] (Synchronization signal detection) In the rotating filter 2 as the rotating plate, a synchronization signal with the position of the filter is required so that the image sensor can perform imaging when the filter region that transmits a predetermined wavelength is in front of the image sensor.

[0040] In this embodiment, as shown in FIGS. 1 and 4, a trigger light source 8 is provided as a light source provided on one side across the filter region in the rotating plate, and a trigger light receiving sensor (photodiode) 9 is provided as a light receiving sensor provided on the other side. Then, synchronization signal detection is performed by comparing the outputs when the light from the trigger light source 8 is received by the trigger light receiving sensor (photodiode) 9 through the trigger filter 50 (FIG. 4).

[0041] That is, the trigger filter 50 having the same spectral transmission characteristics as the first filter or the second filter is, as the third filter, the same filter (same spectral transmission characteristics) as one of the different filters of the rotating plate. Therefore, when the filter on the optical path of the rotating plate is the same as the trigger filter 50, the output of the trigger light receiving sensor 9 becomes on. On the other hand, when the filter on the optical path of the rotating filter 2 is different from the trigger filter 50, the output of the trigger light receiving sensor 9 becomes off.

[0042] That is, a synchronization signal on the rotating plate is detected based on a comparison between a first output from a light-receiving sensor via a first filter and a third filter, and a second output from the light-receiving sensor via a second filter and the third filter.

[0043] Such a trigger filter 50 is provided as a third filter separately from the first filter and the second filter in the optical path from the trigger light source 8 to the trigger light-receiving sensor 9. Alternatively, it may be provided on the trigger light-receiving sensor itself or the trigger light source itself, or the trigger filter 50 may be attached to and integrated with the trigger light-receiving sensor 9 or the trigger light source 8.

[0044] In this embodiment, the synchronization signal can be detected in this way, and the image signal can be selected by wavelength by the wavelength-separated image distribution circuit 4 and stored in a predetermined memory area (FIG. 2) of the memory bank 6.

[0045] In this embodiment, regardless of the number of divisions (even when the number of filter divisions is increased), it is not necessary to allocate a trigger detection area to the rotating filter 2, and a wider filter area can be adopted (FIGS. 3(a) and (b)).

[0046] That is, since there are no marks for forming a synchronization signal in the circumferential direction or the radial direction of the rotating plate, a wider filter area can be adopted. Incidentally, in the comparative example shown in FIG. 7, since marks 16 to 19 for forming a synchronization signal are provided in the radial direction of the rotating plate, a wide filter area cannot be adopted in the radial direction of the rotating plate.

[0047] In FIG. 7, 14b is an image sensor, 32 is a first filter, and 33 is a second filter, and two sets of the combination of the first filter 32 and the second filter 33 are provided. A light source and a sensor for reading the synchronization signal forming marks 16 to 19 are provided with the rotating plate of the rotating filter interposed therebetween, and the trigger light source 8 and the trigger detection sensor 9 in a state excluding the trigger filter 50 in FIG. 4 are used.

[0048] In this way, in the present embodiment, by adopting a wide filter region, the output of the image sensor can be increased, enabling highly accurate temperature measurement.

[0049] The output of the trigger detection sensor in the present embodiment is shown in FIG. 5. In the image sensor 14a, from the time point of the output state where the light of the first wavelength λ1 is received (on) and the light of the second wavelength λ2 is not received (off), it shifts to the time point of the output state where the light of the first wavelength λ1 is not received (off) and the light of the second wavelength λ2 is received (on).

[0050] In the present embodiment, the above-described synchronization signal (trigger signal) is obtained, and the image signal is selected by wavelength according to the signal and stored in the predetermined memory area (memory bank 6) shown in FIG. 2. λ1 Regarding the light of wavelength λ1 that passes through the filter, it is sequentially stored in the memory areas 1-1, 1-2, ··· 1-n according to the rotation of the rotary filter 2. Also, regarding the light of wavelength λ2 that passes through the λ2 filter, it is sequentially stored in the memory areas 2-1, 2-2, ··· 2-n according to the rotation of the rotary filter 2.

[0051] (Modification example) As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof.

[0052] For example, in the above-described embodiment, the case where the rotating plate includes two or more sets of the first filter and the second filter in the circumferential direction is shown. However, it may be configured to include one set of the first filter and the second filter in the circumferential direction.

[0053] Also, in the above-described embodiment, an imaging sensor having two-dimensional pixels is used as the temperature measuring device. However, the temperature of the measurement target may be measured using a line sensor having one-dimensional pixels, a photodiode provided in a dot shape, or the like.

Explanation of reference numerals

[0054] 1... Objective lens, 2... Rotating filter, 3... Image sensor unit, 3a... Image sensor, 3b... Analog amplifier, 3c... A / D conversion element, 4... Wavelength-specific image distribution circuit, 5... Image addition / non-addition processing circuit, 6... Memory bank, 7... Computer, 8... Light source for trigger, 9... Light-receiving sensor for trigger, 10... Motor, 41... Measurement head

Claims

1. A synchronization signal detection unit for a rotating plate having one or more pairs of a first filter and a second filter having different spectral transmission characteristics in a circumferential direction as a filter region, and not having a synchronization signal forming mark, a light source provided on one side of the rotary plate across the filter area; A light receiving sensor provided on the other side; a third filter provided in an optical path from the light source to the light receiving sensor, or provided in the light receiving sensor itself or the light source itself, the third filter having the same spectral transmission characteristics as the first filter or the second filter; having A synchronization signal detection unit characterized by detecting a synchronization signal at the rotating plate based on a comparison between a first output at the light receiving sensor via the first filter and the third filter and a second output at the light receiving sensor via the second filter and the third filter.

2. 2. The synchronization signal detection unit according to claim 1, wherein the third filter is attached to the light receiving sensor itself or the light source itself.

3. A synchronization signal detection unit according to claim 1; The rotating plate; a second light receiving sensor for receiving light emitted from the measurement object and measuring the temperature of the measurement object; a light guiding means for guiding a first light from the measurement object through the first filter and a second light through the second filter to the second light receiving sensor via the rotating plate in a time-series manner; A temperature measuring device comprising:

4. 4. The temperature measuring device according to claim 3, wherein the second light receiving sensor is an image sensor.

5. The output adder includes two or more sets of the first filter and the second filter in a circumferential direction, and adds the outputs of the first light passing through the first filters in units of each pixel, and adds the outputs of the second light passing through the second filters in units of each pixel, 5. The temperature measuring device according to claim 4, wherein the temperature of the measurement object is measured based on the output of the output adder or an average of the outputs of the output adder.

6. 6. The temperature measuring device according to claim 3, wherein the light guiding means is an objective lens.

Images