# US 2021/0333149 A1 · Common-path cube corner interferometer and interference technique > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0333149 A1 - Document ID: US20210333149A1 - Status: Published application - Kind: A1 - Application number: 17/240,950 - Filed: 2021-04-26 - Published: 2021-10-28 - Earliest claimed: 2020-04-27 - Assignees: Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences - Applicants: Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences - Inventors: Ruyi WEI; Lamei DI - Web page: https://patentgrep.com/patent/US20210333149A1 ## CPC - G01J 3/0208: {using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction} - G01J 3/4532: {Devices of compact or symmetric construction (G01J3/4531 takes precedence)} - G01J 3/0243: {having a through-hole enabling the optical element to fulfil an additional optical function, e.g. a mirror or grating having a throughhole for a light collecting or light injecting optical fiber} - G01J 3/45: Interferometric spectrometry - G01J 3/4535: {Devices with moving mirror (G01J3/4532 takes precedence)} - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) ## Abstract The present disclosure relates to a common-path cube-corner retroreflector interferometer with a large optical path difference and high stability, and an interference technique thereof. The interferometer adopts an asymmetric common-path beam splitting structure using right-angled cube-corner retroreflectors, comprising a semi-transmissive and semi-reflective beam splitter, a plane mirror, a first right-angled cube-corner retroreflector, a second right-angled cube-corner retroreflector and an optical path difference element. The incident light is divided into a first transmitted beam and a second reflected beam, which are respectively reflected by the plane mirror and the right-angled cube-corner retroreflectors several times and then split again, two beams of which become interference outputs along directions perpendicular to an incident direction of the incident light, and the other two beams become interference outputs along directions parallel to the incident light. The present disclosure also provides an interference technique based on the interferometer described above. ## Claims ### Claim 1 A common-path cube corner interferometer, comprising: a semi-transmissive and semi-reflective beam splitter, a plane mirror, a first right-angled cube-corner retroreflector, a second right-angled cube-corner retroreflector and an optical path difference element; wherein: the semi-transmissive and semi-reflective beam splitter splits incident light into a first transmitted beam and a second reflected beam; the plane mirror is vertically arranged relative to the semi-transmissive and semi-reflective beam splitter; the first right-angled cube-corner retroreflector and the second right-angled cube-corner retroreflector are asymmetrically arranged at either side of the semi-transmissive and semi-reflective beam splitter, and a base plane of the first right-angled cube-corner retroreflector is parallel to an incident direction of the incident light, while a base plane of the second right-angled cube-corner retroreflector is perpendicular to the incident direction of the incident light; the first beam is sequentially reflected by the plane mirror, the first right-angled cube-corner retroreflector, the plane mirror, the second right-angled cube-corner retroreflector, the plane mirror, and then returns to the semi-transmissive and semi-reflective beam splitter for splitting into the first transmitted beam and the first reflected beam; the second beam is sequentially reflected by the plane mirror, the second right-angled cube-corner retroreflector, the plane mirror, the first right-angled cube-corner retroreflector, the plane mirror, and then returns to the semi-transmissive and semi-reflective beam splitter for splitting into the second reflected beam and the second transmitted beam; the first reflected beam and the second transmitted beam are parallel to the incident light; and the optical path difference element is arranged at a random position in an optical path where the second beam is reflected by and then returns to the semi-transmissive and semi-reflective beam splitter, or at a random position in an optical path where the first beam is transmitted by and then returns to the semi-transmissive and semi-reflective beam splitter, so that an optical path difference is generated between the first beam and the second beam. ### Claim 2 (depends on 1) The common-path cube corner interferometer according to claim 1, wherein the first right-angled cube-corner retroreflector and the second right-angled cube-corner retroreflector are at different distances from the semi-transmissive and semi-reflective beam splitter. ### Claim 3 (depends on 1) The common-path cube corner interferometer according to claim 1, wherein the first right-angled cube-corner retroreflector and the second right-angled cube-corner retroreflector are at different distances from the plane mirror. ### Claim 4 (depends on 1) The common-path cube corner interferometer according to claim 1, wherein the first right-angled cube-corner retroreflector and the second right-angled cube-corner retroreflector are both two-sided right-angled cube-corner retroreflectors or three-sided right-angled cube-corner retroreflectors. ### Claim 5 (depends on 4) The common-path cube corner interferometer according to claim 4, wherein the optical path difference element consists of a prism or a combination of reflecting mirrors. ### Claim 6 (depends on 1) An interference technique based on the common-path cube-corner interferometer according to claim 1, wherein: incident light enters the common-path cube-corner interferometer in a form of parallel or converging light, so that an incident direction of the incident light is parallel to a base plane of a first right-angled cube-corner retroreflector and perpendicular to a base plane of a second right-angled cube-corner retroreflector; the incident light is split by a semi-transmissive and semi-reflective beam splitter (2) into a first transmitted beam and a second reflected beam; the first beam, after being incident into a plane mirror firstly, is reflected to the first right-angled cube-corner retroreflector; the first beam is then reflected by the first right-angled cube-corner retroreflector to the plane mirror for the second time; next, the first beam it is again reflected by the plane mirror to the second right-angled cube-corner retroreflector, and the first beam is reflected by the second right-angled cube-corner retroreflector to the plane mirror for the third time; and the first beam is reflected by the plane mirror to the semi-transmissive and semi-reflective beam splitter; the second beam, after being incident into a plane mirror firstly, is reflected to the second right-angled cube-corner retroreflector; the second beam it is then reflected by the second right-angled cube-corner retroreflector to the plane mirror for the second time; next, the second beam is again reflected by the plane mirror to the first right-angled cube-corner retroreflector, and the second beam is reflected by the first right-angled cube-corner retroreflector to the plane mirror for the third time; and the second beam is reflected by the plane mirror to the semi-transmissive and semi-reflective beam splitter; the first beam passes through an optical path difference element before reaching the semi-transmissive and semi-reflective beam splitter, or the second beam passes through the optical path difference element before reaching the semi-transmissive and semi-reflective beam splitter; the first beam is split again by the semi-transmissive and semi-reflective beam splitter into a first transmitted beam and a first reflected beam; the second beam is split again by the semi-transmissive and semi-reflective beam splitter into a second transmitted beam and a second reflected beam; and the first transmitted beam and the second reflected beam are superimposed along a direction perpendicular to the incident direction of the incident light to form interference fringes; and the first reflected beam and the second transmitted beam are superposed along a direction parallel to the incident direction of the incident light to form interference fringes. ### Claim 7 (depends on 2) The common-path cube corner interferometer according to claim 2, wherein the first right-angled cube-corner retroreflector and the second right-angled cube-corner retroreflector are at different distances from the plane mirror. ### Claim 8 (depends on 2) The common-path cube corner interferometer according to claim 2, wherein the first right-angled cube-corner retroreflector and the second right-angled cube-corner retroreflector are both two-sided right-angled cube-corner retroreflectors or three-sided right-angled cube-corner retroreflectors. ### Claim 9 (depends on 6) The common-path cube corner interferometer according to claim 6, wherein the optical path difference element consists of a prism or a combination of reflecting mirrors. ### Claim 10 (depends on 1) The interference technique according to claim 1, wherein the first right-angled cube-corner retroreflector and the second right-angled cube-corner retroreflector are at different distances from the semi-transmissive and semi-reflective beam splitter. ### Claim 11 (depends on 1) The common-path cube corner interferometer according to claim 1, wherein the first right-angled cube-corner retroreflector and the second right-angled cube-corner retroreflector are at different distances from the plane mirror. ### Claim 12 (depends on 10) The common-path cube corner interferometer according to claim 10, wherein the first right-angled cube-corner retroreflector and the second right-angled cube-corner retroreflector are at different distances from the plane mirror. ### Claim 13 (depends on 1) The common-path cube corner interferometer according to claim 1, wherein the first right-angled cube-corner retroreflector and the second right-angled cube-corner retroreflector are both two-sided right-angled cube-corner retroreflectors or three-sided right-angled cube-corner retroreflectors. ### Claim 14 (depends on 10) The common-path cube corner interferometer according to claim 10, wherein the first right-angled cube-corner retroreflector and the second right-angled cube-corner retroreflector are both two-sided right-angled cube-corner retroreflectors or three-sided right-angled cube-corner retroreflectors. ### Claim 15 (depends on 13) The common-path cube corner interferometer according to claim 13, wherein the optical path difference element consists of a prism or a combination of reflecting mirrors. ### Claim 16 (depends on 14) The common-path cube corner interferometer according to claim 14, wherein the optical path difference element consists of a prism or a combination of reflecting mirrors.