# US 10,866,084 B2 · Relative position detection means and displacement detection device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,866,084 B2 - Document ID: US10866084B2 - Status: Granted - Kind: B2 - Application number: 16/575,008 - Filed: 2019-09-18 - Published: 2020-03-19 - Granted: 2020-12-15 - Earliest claimed: 2018-09-18 - Assignees: Dmg Mori Co., Ltd. - Applicants: Dmg Mori Co., Ltd. - Inventors: Shun Okuyama; Akinori Suzuki - Web page: https://patentgrep.com/patent/US10866084B2 ## CPC - G01B 11/026: {by measuring distance between sensor and object (G01B11/0608 takes precedence)} - G02B 27/283: {used for beam splitting or combining} - G02F 1/13363: Birefringent elements, e.g. for optical compensation - G02B 27/10: Beam splitting or combining systems (polarising systems G02B27/28; mixing and splitting light signals using optical waveguides G02B6/28; {beam shaping, e.g. changing the cross-sectional area, by dividing or superposing multiple light beams G02B27/0905}) - G02B 27/14: operating by reflection only - G02F 1/133638: {Waveplates, i.e. plates with a retardation value of lambda/n} - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS ## Abstract The invention corresponds to wide signal period with simple structure by providing a relative position detection means for optically detecting a relative position of displacement of an object to be measured in a measuring direction. The invention includes a target mounted on the object to be measured and irradiated with light from a light source; a light receiver for detection of a relative position for receiving light by changing polarization state of reflected light at the target with respect to the light; and a relative position information output unit for outputting relative position information based on displacement of the target in the measuring direction. The target may include a reflector mounted on the object to be measured and a plurality of birefringent members provided on the reflector and having a thickness changing from a tip to a base end along the measuring direction. ## Claims ### Claim 1 A relative position detection means for optically detecting a relative position of displacement of an object to be measured along a measuring direction, comprising: an optical member mounted on the object to be measured and irradiated with light from a light source; a light receiver for detection of relative position for receiving light by changing polarization state of reflected light at the optical member with respect to the light; and a relative position information output unit for outputting relative position information based on displacement of the optical member along the measuring direction based on a change of polarization state of the reflected light received at the light receiver for detection of relative position, wherein the optical member comprises: a reflector mounted on the object to be measured; and a plurality of birefringent members provided on the reflector, the plurality of birefringent members including a first birefringent member having a thickness changing from a tip to a base end along the measuring direction, and a second birefringent member having a thickness changing from a tip to a base end along a direction different from the measuring direction. ### Claim 2 (depends on 1) The relative position detection means according to claim 1, wherein the light receiver for detection of relative position detects a change of polarization state of the reflected light along with movement of the optical member along the measuring direction, the relative position information output unit outputs the relative position information of the optical member based on a signal obtained by photoelectric conversion of a change of polarization state of the reflected light. ### Claim 3 (depends on 1) The relative position detection means according to claim 1, wherein the light receiver for detection of relative position comprising: a beam splitter for splitting the reflected light into two; a first polarizing beam splitter for transmitting P component and reflecting S component of one reflected light split by the beam splitter; a first light receiving element for receiving transmitted light of the first polarizing beam splitter; a second light receiving element for receiving reflected light of the first polarizing beam splitter; a second polarizing beam splitter for transmitting P component and reflecting S component of another reflected light split by the beam splitter; a quarter wavelength plate interposed between the beam splitter and the second polarizing beam splitter; a third light receiving element for receiving reflected light of the second polarizing beam splitter; and a fourth light receiving element for receiving transmitted light of the second polarizing beam splitter. ### Claim 4 (depends on 1) The relative position detection means according to claim 1, wherein the birefringent members are configured by arranging a plurality of different birefringent members in parallel along the measuring direction, or is configured by laminating a plurality of different birefringent members along an incident direction of the light. ### Claim 5 (depends on 4) The relative position detection means according to claim 4, wherein the birefringent members are configured by laminating a plurality of birefringent members with different crystal axis direction along an incident direction of the light. ### Claim 6 (depends on 1) The relative position detection means according to claim 1, wherein a correction prism is provided at any of front stage side or rear stage side of the birefringent members with respect to the light source. ### Claim 7 (depends on 1) The relative position detection means according to claim 1, wherein two light receivers for detection of relative position are arranged along the measuring direction, and it is arranged to estimate and correct wavelength variation amount based on a difference of phase fluctuation amount of polarization state of the reflected light detected by each light receiver for detection of relative position. ### Claim 8 (depends on 1) The relative position detection means according to claim 1, wherein a polarizing plate is further arranged between the light source and the birefringent members. ### Claim 9 (depends on 1) The relative position detection means according to claim 1, wherein an azimuth correction unit for performing azimuth correction to the reflected light is further arranged at the light receiver for detection of relative position. ### Claim 10 A displacement detection device for optically detecting a displacement of an object to be measured along a measuring direction, comprising: a light source for irradiating light; a light source side beam splitter for splitting the light from the light source into two; a relative position detection means for detecting relative position of the displacement of the object to be measured along the measuring direction based on a change of polarization state of reflected light with respect to one light split by the light source side beam splitter; an absolute position detection means for detecting absolute position of the displacement of the object to be measured along the measuring direction based on a change of light quantity of reflected light with respect to another light split by the light source side beam splitter, wherein the absolute position detection means and the relative position detection means are arranged on in-line with respect to the measuring direction of the object to be measured, wherein the relative position detection means comprising: an optical member mounted on the object to be measured and irradiated with light from the light source; a light receiver for detection of relative position for receiving light by changing polarization state of reflected light at the optical member with respect to the light; and a relative position information output unit for outputting relative position information based on the displacement of the optical member along the measuring direction based on a change of polarization state of the reflected light received at the light receiver for detection of relative position, wherein the optical member comprises: a reflector mounted on the object to be measured; and a plurality of birefringent members provided on the reflector, the plurality of birefringent members including a first birefringent member having a thickness changing from a tip to a base end along the measuring direction, and a second birefringent member having a thickness changing from a tip to a base end along a direction different from the measuring direction. ### Claim 11 (depends on 10) The displacement detection device according to claim 10, wherein the light receiver for detection of relative position detects a change of polarization state of the reflected light along with movement of the optical member along the measuring direction, and the relative position information output unit outputs the relative position information of the optical member based on a signal obtained by photoelectric conversion of a change of polarization state of the reflected light. ### Claim 12 (depends on 10) The displacement detection device according to claim 10, wherein the absolute position detection means comprising: a prism mounted on the object to be measured and irradiated with the light from the light source via a mirror; a light receiver for detection of absolute position for receiving light by changing light quantity of reflected light at the prism with respect to the light; and an absolute position information output unit for outputting absolute position information based on displacement of the prism along the measuring direction based on a change of the light quantity of the reflected light received at the light receiver for detection of absolute position, wherein at top surface side of the prism, a variable reflection film, in which reflection characteristic varies along the measuring direction, is provided.