Distance calculation device

Abstract

The present invention provides a distance calculation device that can calculate distance information relating to the distance a workpiece travels. [Solution] The system comprises a light source 10 that emits light, a first optical system 20 that converts the light from the light source into elliptical polarization and emits it toward a workpiece W1 that is transparent and moving in a specific direction, a second optical system 30 that converts the light from the workpiece into linear polarization and emits it, and an optical sensor 40 that acquires optical information of the workpiece based on the light from the second optical system. The first optical system includes a first polarizing filter 22 that converts to linear polarization and a first waveplate 23 that converts the linear polarization from the first polarizing filter into elliptical polarization. The second optical system 30 includes a second waveplate 31 that converts the light from the workpiece and a second polarizing filter 32 that is placed between the second waveplate and the optical sensor 40 and converts the light from the second waveplate into linear polarization.

Description

Technical Field

[0002] , , ,

[0001] The present disclosure relates to a moving distance calculation device.

Background Art

[0002] Conventionally, for a moving sheet-like translucent object, light from an illumination light source transmitted through a first polarizing plate is irradiated, and a speed measuring device that measures the speed of the translucent object based on the output signal of a photodetector that receives the light transmitted through the translucent object, a second polarizing plate, and a spatial filter has been disclosed (for example, see Patent Document 1). This speed measuring device measures the speed of the translucent object by detecting the birefringence of light when the light passes through the translucent object.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0006] The travel distance calculation device according to this disclosure comprises a light source that emits light, a first optical system that converts the light from the light source into elliptical polarization and emits it toward a workpiece that is transparent and moving in a specific direction, a second optical system that converts the light from the workpiece into linear polarization and emits it, an optical sensor that acquires optical information of the workpiece based on the light from the second optical system, and an information processing device that calculates travel distance information relating to the travel distance of the workpiece during the period from the first time to the second time, based on a correlation value showing the correlation between the first optical information acquired by the optical sensor at the first time and the second optical information acquired by the optical sensor at the second time, wherein the first optical system comprises a first polarizing filter that converts the light from the light source into linear polarization and a first waveplate disposed between the first polarizing filter and the workpiece and converts the linear polarization from the first polarizing filter into elliptical polarization, and the second optical system comprises a second waveplate that converts the light from the workpiece and a second polarizing filter disposed between the second waveplate and the optical sensor and converts the light from the second waveplate into linear polarization. [Effects of the Invention]

[0007] According to this disclosure, it is possible to calculate distance information regarding the distance traveled by the workpiece. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing the general configuration of the travel distance calculation device according to Embodiment 1. [Figure 2] This is a block diagram showing the schematic configuration of the travel distance calculation device according to Embodiment 1. [Figure 3] This is a block diagram showing an example of the hardware configuration of an information processing device according to Embodiment 1. [Figure 4] This is a block diagram showing an example of the hardware configuration of an information processing device according to Embodiment 1. [Figure 5] This flowchart shows an example of processing performed by the information processing device according to Embodiment 1. [Figure 6]This graph shows the reference optical information and measurement optical information acquired by the information processing device according to Embodiment 1. [Figure 7] Figure 7A is a side view of Figure 1, viewed from the left, showing light converted to linear polarization by the first polarizing filter of the optical information acquisition device according to Embodiment 1; Figure 7B is a side view of Figure 1, viewed from the left, showing light converted to circular polarization by the first waveplate of the optical information acquisition device according to Embodiment 1; and Figure 7C is a side view of Figure 1, viewed from the left, showing light birefred by the workpiece. [Figure 8] Figure 8A is a side view of Figure 1, viewed from the left, showing the light converted by the second waveplate of the optical information acquisition device according to Embodiment 1, and Figure 8B is a side view of Figure 1, viewed from the left, showing the light converted to linear polarization by the second polarizing filter of the optical information acquisition device according to Embodiment 1. [Modes for carrying out the invention]

[0009] The embodiments relating to this disclosure will be described in detail below with reference to the drawings. Embodiment 1. First, with reference to Figure 1, the travel distance calculation device according to Embodiment 1 will be described. Figure 1 is a schematic diagram showing the general configuration of the travel distance calculation device according to Embodiment 1. The travel distance calculation device according to Embodiment 1 is a device for measuring the travel distance of a workpiece W1 based on changes in the optical information of a workpiece W1 that is translucent and moves in a specific direction. As shown in Figure 1, the travel distance calculation device according to Embodiment 1 includes an optical information acquisition device 1 and an information processing device 100. In Figure 1, the downward direction is the X direction, the rightward direction is the Z direction, and the direction from back to front is the Y direction.

[0010] For example, the workpiece W1 is formed in the form of a sheet extending in the X and Y directions from a translucent material, and moves by being pulled out from a rolled-up state or being transported while being rolled up, so as to move in the X direction (A direction) as a specific direction. In Embodiment 1, the left side of the workpiece W1 shown in Figure 1 is also called the workpiece surface W1a, and the right side is also called the workpiece back surface W1b. In Embodiment 1, the workpiece is not limited to being formed in the form of a sheet, but may be formed in the form of a plate, rod, block, or other shape.

[0011] Next, with reference to Figure 1, an optical information acquisition device 1 according to Embodiment 1 will be described. As shown in Figure 1, the optical information acquisition device 1 includes a light source 10, a first optical system 20, a second optical system 30, and an optical sensor 40.

[0012] The light source 10 emits light. For example, the light source 10 has one or more light-emitting elements 11 that emit light when power is supplied, and emits light toward the first optical system 20. Specifically, the light source 10 has one or more LEDs (Light Emitting Diodes) as light-emitting elements 11.

[0013] The first optical system 20 receives light from the light source 10, converts the incident light from the light source 10 into elliptical polarization, and emits it toward the workpiece W1. For example, the first optical system 20 is positioned on one side of the workpiece W1 in the Z direction, which is perpendicular to the surface W1a of the workpiece W1. Alternatively, for example, the first optical system 20 includes one or more lenses 21 that focus light from the light source 10, a first polarizing filter 22 that converts the light from the lenses 21 into linear polarization, and a first waveplate 23 positioned between the first polarizing filter 22 and the workpiece W1, which converts the linear polarization from the first polarizing filter into elliptical polarization. In Embodiment 1, "ellipse" includes a "circle" in which the length of the major axis and the length of the minor axis are equal.

[0014] The first polarizing filter 22 converts the light from the light source 10 into linearly polarized light. For example, the first polarizing filter 22 is constituted by a transmissive polarizing filter that converts the light from the light source 10 transmitted through the first polarizing filter 22 into linearly polarized light.

[0015] The first wave plate 23 is disposed between the first polarizing filter 22 and the workpiece W1, and converts the linearly polarized light from the first polarizing filter 22 into elliptically polarized light. For example, the first wave plate 23 is constituted by a quarter-wave plate arranged such that, when viewed in the Z direction, the polarization direction of the first polarizing filter 22 and the slow axis of the first wave plate 23 are at 45°. By giving a phase difference of π / 2 to the X-axis component and the Y-axis component of the light incident from the first polarizing filter 22, the linearly polarized light from the first polarizing filter 22 transmitted through the first wave plate 23 is converted into circularly polarized light.

[0016] The second optical system 30 has the light from the workpiece W1 incident thereon, and converts the incident light from the workpiece W1 into linearly polarized light and emits it. For example, the second optical system 30 is disposed on the other side of the workpiece W1 with respect to the first optical system 20 in the Z direction. Also, for example, the second optical system 30 includes a second wave plate 31 that converts the light from the workpiece W1, a second polarizing filter 32 that is disposed between the second wave plate 31 and the optical sensor 40 and converts the light from the second wave plate 31 into linearly polarized light, and one or more lenses 33 that form an image of the light from the second polarizing filter 32 on the optical sensor 40.

[0017] The second wave plate 31 converts the light from the workpiece W1. For example, the second wave plate 31 is constituted by a quarter-wave plate, and by giving a phase difference of π / 2 to the X-axis component and the Y-axis component of the light incident from the workpiece W1, the light from the workpiece W1 transmitted through the second wave plate 31 is converted. Specifically, when circularly polarized light is incident from the workpiece W1, the second wave plate 31 gives a phase difference of π / 2 to the X-axis component and the Y-axis component of the light incident from the workpiece W1, thereby converting the light from the workpiece W1 transmitted through the second wave plate 31 into linearly polarized light.

[0018] The second polarizing filter 32 is disposed between the second wavelength plate 31 and the optical sensor 40, and converts the light from the second wavelength plate 31 into linearly polarized light. For example, when viewed in the Z direction, the second polarizing filter 32 is arranged such that the slow axis of the second wavelength plate 31 and the polarization direction of the second polarizing filter 32 are 45°, and converts the light from the second wavelength plate 31 into linearly polarized light. Specifically, when circularly polarized light is incident from the workpiece W1 on the second wavelength plate 31, the second polarizing filter 32 is arranged such that, when viewed in the Z direction, the polarization direction of the linearly polarized light from the workpiece W1 that passes through the second wavelength plate 31 and the polarization direction of the second polarizing filter 32 are 90°.

[0019] The optical sensor 40 acquires the optical information of the workpiece W1 based on the light from the second optical system 30. For example, the optical sensor 40 has one or more light receiving elements that receive the light from the second optical system 30, and acquires the optical information of the workpiece W1 by converting the light received by the light receiving elements into signals. Specifically, the optical sensor 40 is linearly arranged along the X direction, and has N light receiving elements (image pickup elements) numbered from 1 to N (for example, N is a natural number of 2 or more) that receive the light from the second optical system 30, and is configured as a one-dimensional image sensor (line sensor) that acquires one-dimensional image information. The optical sensor 40 outputs the acquired optical information toward the information processing device 100. For example, the optical sensor 40 outputs the first optical information acquired at the first time and the second optical information acquired at a second time different from the first time toward the information processing device 100. For example, the light receiving elements included in the optical sensor 40 are constituted by a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor.

[0020] Next, referring to FIG. 2, the information processing device 100 according to Embodiment 1 will be described. FIG. 2 is a block diagram showing a schematic configuration of the moving distance calculation device according to Embodiment 1. As shown in FIG. 2, the information processing device 100 includes an optical information acquisition unit 101, a correlation value calculation unit 102, a moving distance calculation unit 103, and a storage unit 104.

[0021] The optical information acquisition unit 101 acquires optical information of the workpiece W1 moving in the X direction based on information from the optical sensor 40. For example, the optical information acquisition unit 101 acquires one-dimensional image data along the X direction of the workpiece W1 moving in the X direction based on information from the optical sensor 40.

[0022] The correlation value calculation unit 102 calculates a correlation value indicating the correlation between two pieces of optical information by comparing optical information acquired at two different time points by the optical information acquisition unit 101. For example, the correlation value calculation unit 102 calculates a correlation value indicating the correlation between reference optical information, which is a reference first optical information acquired in advance at a first time point by the optical information acquisition unit 101, and measurement optical information, which is a second optical information acquired at a second time point different from the first time point, using the phase-limited correlation method.

[0023] The distance calculation unit 103 calculates distance information relating to the distance the workpiece W1 travels in the X direction based on the correlation value calculated by the correlation value calculation unit 102. For example, the distance calculation unit 103 calculates the distance the workpiece W1 travels in the X direction between two different time points by calculating the distance between two optical information sets that have the highest correlation value, based on the correlation value calculated by the correlation value calculation unit 102. Note that the distance calculation unit 103 is not limited to calculating only the distance the workpiece W1 travels in the X direction as distance information; it is sufficient if it is configured to calculate distance information relating to the workpiece's travel distance based on the correlation value calculated by the correlation value calculation unit 102. For example, information indicating the workpiece's travel speed can be obtained by differentiating the workpiece's travel distance with respect to travel time, and can therefore be considered information relating to travel distance. Therefore, the movement distance calculation unit 103 may calculate the movement distance of the workpiece W1 in the X direction as movement distance information, or it may calculate the movement speed of the workpiece W1 in the X direction based on the calculated movement distance, or it may calculate the movement speed of the workpiece W1 in the X direction without going through the calculation result of the movement distance of the workpiece W1 in the X direction.

[0024] The memory unit 104 stores information used by the information processing device 100 when it performs each process, and information indicating the results of each process. For example, the memory unit 104 stores optical information acquired by the optical information acquisition unit 101, functions showing the waveforms of each optical information calculated by the correlation value calculation unit 102, the results of processing by the travel distance calculation unit 103, and various setting values ​​used when each component of the information processing device 100 performs its processing. When each component of the information processing device 100 performs each process, it refers to and reads the information stored in the memory unit 104 as needed, and stores the results of each process in the memory unit 104.

[0025] Next, the hardware configuration of the information processing device 100 will be described with reference to Figures 3 and 4. Figure 3 is a block diagram showing an example of the hardware configuration of the information processing device 100 according to Embodiment 1, and Figure 4 is a block diagram showing an example of a hardware configuration of the information processing device 100 according to Embodiment 1 that is different from Figure 3. For example, as shown in Figure 3, the information processing device 100 has a processor 100a, a memory 100b, and an I / O port 100c, and is configured so that the processor 100a reads and executes a program stored in the memory 100b. The memory 100b is composed of, for example, a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, EEPROM, etc., or a combination thereof. The memory 100b may also be a magnetic disk, flexible disk, optical disk, compact disk, minidisc, DVD, etc. Furthermore, the memory 100b may be an HDD or SSD.

[0026] Furthermore, as shown in Figure 4, for example, the information processing device 100 has dedicated hardware, namely a processing circuit 100d and an I / O port 100c. The processing circuit 100d is composed of, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, a system LSI (Large-Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. Each function of the information processing device 100 is realized by these processors 100a or the dedicated hardware, namely the processing circuit 100d, executing a program which is software, firmware, or a combination of software and firmware. The information processing device 100 may also have other hardware, such as a hardware timer.

[0027] Next, the processing performed by the information processing device 100 will be described with reference to Figures 2, 5, and 6. Figure 5 is a flowchart showing an example of the processing performed by the information processing device according to Embodiment 5. The processing performed by the information processing device 100 shown in Figure 5 is a process for calculating travel distance information related to the travel distance of the workpiece W1 based on image data as optical information acquired by the optical information acquisition device 1.

[0028] As shown in Figure 5, when the information processing device 100 starts the regression function calculation process, it first acquires reference optical information (step ST01). In this process, the information processing device 100 acquires image data as reference optical information, which is the optical information used as a basis for calculating the correlation value by the correlation value calculation unit 102, using the optical information acquisition unit 101.

[0029] When the information processing device 100 performs the processing in step ST01, it acquires measurement optical information (step ST02). In this process, when the correlation value calculation unit 102 calculates the correlation value, the optical information acquisition unit 101 acquires image data as measurement optical information, which is optical information to be compared with the reference optical information acquired in step ST01. In this process, the information processing device 100 acquires new image data as measurement optical information acquired by the optical sensor 40 after a predetermined specific time interval has been set since the image data as reference optical information acquired in step ST01 was acquired by the optical sensor 40.

[0030] Figure 6 is a graph showing the waveforms of the reference optical information A1 and the measured optical information A2 acquired by the information processing device 100.

[0031] When the information processing device 100 performs the processing in step ST02, it calculates a correlation value between the reference optical information and the immediately preceding measured optical information (step ST03). In this process, the information processing device 100 calculates the correlation value between the reference optical information obtained in the processing of step ST01 and the measured optical information obtained in the immediately preceding step ST02 using the correlation value calculation unit 102.

[0032] When the information processing device 100 performs the processing in step ST03, it calculates the distance the workpiece W1 moves in the X direction (step ST04). In this process, the information processing device 100 calculates the distance the workpiece W1 moves in the X direction based, for example, on the amount of difference between the image data as reference optical information and the image data as measurement optical information obtained from the correlation value calculated in step ST03, the distance between the image sensors, and the magnification of the imaging lens.

[0033] When the information processing device 100 performs the process in step ST04, it determines whether the number of completions has been reached (step ST05). In this process, the information processing device 100 determines whether a sufficient number of samples have been obtained to calculate the movement distance of the workpiece W1.

[0034] In the process of step ST05, if the number of completions has not been reached (NO in step ST05), the information processing device 100 returns to step ST02 and acquires measurement optical information for calculating a new travel distance. In this way, the information processing device 100 is configured to improve the accuracy of calculating the travel distance of the workpiece W1 in the X direction by performing linear regression by repeating the process from step ST02 to step ST05 multiple times. The information processing device 100 may also be configured to calculate the travel speed of the workpiece W1 based on the calculated travel distance of the workpiece W1.

[0035] In the process of step ST05, if the number of completions has been reached (YES in step ST05), the information processing device 100 terminates the process.

[0036] Next, the details of the optical information acquisition device 1 will be described with reference to Figures 1, 7, and 8. Figure 7A is a side view of Figure 1, seen from the left, showing light converted to linear polarization by the first polarizing filter 22 of the optical information acquisition device 1 according to Embodiment 1. As shown in Figure 7A, for example, the first polarizing filter 22 is arranged such that the polarization direction 22a is aligned with the X direction, and converts light from the light source 10 into linearly polarized light L1a.

[0037] Figure 7B is a side view of Figure 1, seen from the left, showing light converted to circular polarization by the first waveplate 23 of the optical information acquisition device 1 according to Embodiment 1. As shown in Figure 7B, for example, the first waveplate 23 is arranged such that the slow axis 23a and the fast axis 23b are at a 45° angle to the polarization direction 22a of the first polarizing filter 22, and converts the linearly polarized light L1a from the first polarizing filter 22 into clockwise circularly polarized light L1b.

[0038] Figure 7C is a side view of Figure 1, seen from the left, showing the light birefred by the workpiece W1. For example, the workpiece W1 is distorted as it is transported while being pulled in the X direction, causing the light from the first optical system 20 to birefractive. As a result, as shown in Figure 7C, for example, circularly polarized light incident on the workpiece W1 is converted to elliptically polarized light L1c by birefringence as it passes through the workpiece W1.

[0039] Figure 8A is a side view of Figure 1, seen from the left, showing the light converted by the second waveplate 31 of the optical information acquisition device 1 according to Embodiment 1. As shown in Figure 8A, for example, the second waveplate 31 is arranged such that the slow axis 31a and the fast axis 31b are at a 45° angle to the X direction, and converts the light from the workpiece W1 into counterclockwise circularly polarized light L1d.

[0040] Figure 8B is a side view of Figure 1, seen from the left, showing light converted to linear polarization by the second polarizing filter 32 of the optical information acquisition device 1 according to Embodiment 1. As shown in Figure 8B, for example, the second polarizing filter 32 is arranged such that its polarization direction 32a is aligned with the Y direction, and converts light from the second waveplate 31 into linearly polarized light L1e. Also, for example, the optical sensor 40 has a plurality of light-receiving elements arranged linearly along the Y direction, and acquires optical information by receiving the linearly polarized light L1e from the second polarizing filter 32.

[0041] As described above, the travel distance calculation device according to Embodiment 1 comprises a light source that emits light, a first optical system that converts the light from the light source into elliptical polarization and emits it toward a workpiece that is transparent and moving in a specific direction, a second optical system that converts the light from the workpiece into linear polarization and emits it, an optical sensor that acquires optical information of the workpiece based on the light from the second optical system, and an information processing device that calculates travel distance information relating to the travel distance of the workpiece during the period from the first time to the second time, based on a correlation value showing the correlation between the first optical information acquired by the optical sensor at the first time and the second optical information acquired by the optical sensor at the second time. The first optical system comprises a first polarizing filter that converts the light from the light source into linear polarization, and a first waveplate disposed between the first polarizing filter and the workpiece and converting the linear polarization from the first polarizing filter into elliptical polarization. The second optical system comprises a second waveplate that converts the light from the workpiece, and a second polarizing filter disposed between the second waveplate and the optical sensor and converting the light from the second waveplate into linear polarization.

[0042] With this configuration, the travel distance calculation device according to Embodiment 1 can acquire optical information of a translucent workpiece W1 non-contactually by obtaining optical information showing the change in the effect of birefringence of light passing through the workpiece W1 using an optical sensor 40, and can calculate the travel distance and travel speed of the workpiece. Furthermore, even if there is directionality in the birefringence of light irradiated onto the moving workpiece W1 as it passes through the workpiece W1, it is not necessary to set up the device and the workpiece W1 so that, for example, the polarization direction of the polarizing filter and the direction of birefringence of the workpiece W1 do not coincide, and the optical information of the workpiece W1 can be acquired more easily than in the conventional method.

[0043] Furthermore, the travel distance calculation device according to Embodiment 1 includes an optical sensor 40 having a plurality of light-receiving elements arranged in a straight line to receive light from the second optical system 30. For example, the travel distance calculation device according to Embodiment 1 is configured to calculate travel distance information relating to the travel distance of the workpiece W1 during the period from the first time to the second time, based on a correlation value showing the correlation between first optical information acquired by the optical sensor 40 at a first time and second optical information acquired by the optical sensor 40 at a second time. With this configuration, the travel distance calculation device can calculate the travel distance and travel speed of the workpiece W1 based, for example, on the change in one-dimensional optical information along the direction of movement of the workpiece W1, acquired by the optical sensor 40.

[0044] In Embodiment 1, the optical sensor 40 is configured as a one-dimensional line sensor, but is not limited to this. The optical sensor only needs to be configured to acquire optical information of a workpiece based on light from the second optical system. For example, the optical sensor may be configured as a two-dimensional area sensor in which a plurality of light-receiving elements are arranged along a first direction and a second direction intersecting the first direction.

[0045] Furthermore, in Embodiment 1, the first wave plate 23 and the second wave plate 31 are both made of quarter-wave plates, but the invention is not limited to this. The first wave plate and the second wave plate only need to be configured to give a phase difference to the incident light, and for example, the first wave plate and the second wave plate may be eighth-wave plates or other types of wave plates.

[0046] Furthermore, in Embodiment 1, the optical information acquisition device 1 includes a first optical system 20 arranged on one side of the workpiece W1 in the Z direction perpendicular to the surface of the workpiece W1 which is formed in the shape of a flat plate or sheet, and a second optical system 30 arranged on the other side of the workpiece W1 in the Z direction, but is not limited thereto. The optical information acquisition device may include a first optical system that converts light from a light source into elliptically polarized light and emits it toward a workpiece that is transparent and moving in a specific direction, and a second optical system that converts light from the workpiece into linearly polarized light and emits it, and is configured to acquire optical information of the workpiece by an optical sensor based on the light from the second optical system. For example, the optical information acquisition device may include a first optical system and a second optical system arranged on one side of the workpiece in a direction perpendicular to the surface of the workpiece, and may be configured such that light from the first optical system incident on one side of the workpiece is transmitted through the workpiece and reflected by the other side of the workpiece, and the reflected light is incident on the second optical system.

[0047] Furthermore, this disclosure allows for modifications of any component of the embodiment, or the omission of any component. [Explanation of Symbols]

[0048] 1:Optical information acquisition device 10:Light source 11: Light-emitting element 20: 1st optical system 21: Lens 22: First polarizing filter 22a: Polarization direction 23: 1st wave plate 23a: slow axis 23b: Fast axis 30:Second optical system 31:Second wavelength plate 31a: Slow axis 31b: Fast axis 32: Second polarizing filter 32a: Polarization direction 33: Lens 40: Optical sensor 100: Information Processing Device 100a: Processor 100b: Memory 100c: I / O port 100d: Processing circuit 101:Optical information acquisition section 102: Correlation Value Calculation Unit 103: Distance calculation unit 104: Storage section A1: Reference optical information A2: Measurement optical information L1a: Linear polarization L1b: Circular polarization L1c: Elliptic polarization L1d: Circular polarization L1e: Linear polarization W1: Work W1a: Surface W1b: Reverse side

Claims

1. A light source that emits light, A first optical system that converts light from the light source into elliptically polarized light and emits it toward a workpiece that is transparent and moving in a specific direction, A second optical system that converts the light from the workpiece into linearly polarized light and emits it, An optical sensor that acquires optical information of the workpiece based on light from the second optical system, The system includes an information processing device that calculates travel distance information relating to the travel distance of the workpiece during the period from the first time to the second time, based on a correlation value showing the correlation between first optical information acquired by the optical sensor at a first time and second optical information acquired by the optical sensor at a second time. The first optical system includes a first polarizing filter that converts light from the light source into linearly polarized light, and a first waveplate disposed between the first polarizing filter and the workpiece, which converts the linearly polarized light from the first polarizing filter into elliptically polarized light. The second optical system includes a second waveplate that converts light from the workpiece, and a second polarizing filter positioned between the second waveplate and the optical sensor, which converts the light from the second waveplate into linearly polarized light. A device for calculating travel distance, characterized by the following features.

2. The optical sensor has a plurality of light-receiving elements arranged in a straight line that receive light from the second optical system. The travel distance calculation device according to claim 1, characterized by the feature.

3. The first optical system is arranged on one side of the workpiece in a direction perpendicular to the surface of the workpiece, which is formed in the shape of a flat plate or sheet. The second optical system is positioned on the other side of the workpiece in a direction perpendicular to the surface of the workpiece. A device for calculating travel distance according to claim 1 or 2, characterized in that it is a device for calculating travel distance according to claim 1 or 2.

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