# US 9,752,901 B2 · Scale and optical encoder > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,752,901 B2 - Document ID: US9752901B2 - Status: Granted - Kind: B2 - Application number: 14/721,455 - Filed: 2015-05-26 - Published: 2015-12-03 - Granted: 2017-09-05 - Earliest claimed: 2014-05-27 - Assignees: Mitutoyo Corporation - Applicants: Mitutoyo Corporation - Inventors: Yoshiaki Kato - Web page: https://patentgrep.com/patent/US9752901B2 ## CPC - G01D 5/34715: {Scale reading or illumination devices} - G01D 5/24438: {Special design of the sensing element or scale} - G01D 5/347: using displacement encoding scales - G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR ## Abstract A scale and an optical encoder capable of maintaining an accuracy of a reference position irrespective of an error in attaching a detection head are provided. The scale according to the present invention is a scale including main-signal scale gratings having grating patterns of a predetermined pitch, and a reference-signal pattern, in which the main-signal scale gratings are arranged in parallel in a direction perpendicular to a length measurement axis of the main-signal scale gratings and are different from each other in phase by ½, and the reference-signal pattern is formed on the length measurement axis of the main-signal scale gratings. The optical encoder according to the present invention includes a light source, main-signal light source gratings, reference-signal light source gratings, main-signal receiver gratings, and a reference-signal receiver element. ## Claims ### Claim 1 A scale comprising first and second main-signal scale gratings having grating patterns of a predetermined pitch, and a reference-signal pattern, wherein: each of the two main-signal scale gratings comprises transmitting parts and non-transmitting parts, the non-transmitting parts of each of the two main-signal scale gratings are arranged at the predetermined pitch in parallel to a length measurement axis of the scale, and the non-transmitting parts of the first main-signal scale grating are shifted by one half the predetermined pitch from the non-transmitting parts of the second main-signal scale grating, and the reference-signal pattern is formed on a length measurement axis of the first main-signal scale grating and on a length measurement axis of the second main-signal scale grating. ### Claim 2 (depends on 1) The scale according to claim 1, wherein a part of the grating patterns of the main-signal scale gratings is disturbed, whereby the reference-signal pattern is formed. ### Claim 3 (depends on 1) The scale according to claim 1, wherein the reference-signal pattern extends to cross the first and the second main-signal scale gratings in a direction perpendicular to the length measurement axis of the scale, and the reference-signal pattern does not disturb the grating patterns for the first main-signal scale grating and disturbs the grating patterns for the second main-signal scale grating. ### Claim 4 (depends on 1) The scale according to claim 1, wherein the reference-signal pattern comprises a non-transmitting part that extends in the direction perpendicular to the length measurement axis of the scale and interrupts light, and the length of the reference-signal pattern in the length measurement direction is equal to the length of half the cycle of the pitch of the main-signal scale gratings. ### Claim 5 (depends on 1) The scale according to claim 1, wherein the reference-signal pattern is a transmitting part extending in the direction perpendicular to the length measurement axis of the scale. ### Claim 6 (depends on 1) The scale according to claim 1, wherein a plurality of the reference-signal patterns are provided. ### Claim 7 (depends on 1) The scale according to claim 1, wherein: the first and second main-signal scale gratings arranged in parallel form one pair, and a plurality of pairs of the first and the second main-signal scale gratings are arranged in parallel in the direction perpendicular to the length measurement axis of the scale. ### Claim 8 (depends on 1) An optical encoder comprising: the scale according to claim 1; a light source; main-signal light source gratings that are arranged between the light source and the scale to form a main-signal interference fringe in collaboration with the main-signal scale gratings; reference-signal light source gratings that are arranged between the light source and the scale to form a reference-signal interference fringe in collaboration with the reference-signal pattern; main-signal detection means that detects a main signal from the main-signal interference fringe; and reference-signal detection means that detects a reference signal from the reference-signal interference fringe, wherein: the main-signal light source gratings comprise gratings formed to have a pitch so that two or more interference fringes formed by the two or more main-signal scale gratings and the main-signal light source gratings have the same phase, and the reference-signal light source gratings comprise gratings formed to have a pitch so that two or more interference fringes formed by the two or more main-signal scale gratings and the reference-signal light source grating are different from each other in phase by ½. ### Claim 9 (depends on 8) The optical encoder according to claim 8, wherein: the main-signal light source gratings and the reference-signal light source gratings are arranged in parallel to each other in a length measurement direction of the scale, the main-signal detection means is arranged in parallel to the main-signal light source gratings so as to be opposed to the main-signal light source gratings with the scale interposed therebetween, and the reference-signal detection means is arranged so as to be opposed to the reference-signal light source gratings with the scale interposed therebetween.