# US 2013/0155397 A1 · Rotation Angle Detecting Apparatus And Surveying Instrument > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0155397 A1 - Document ID: US20130155397A1 - Status: Published application - Kind: A1 - Application number: 13/718,329 - Filed: 2012-12-18 - Published: 2013-06-20 - Earliest claimed: 2011-12-19 - Assignees: Topcon Corporation - Inventors: Kaoru Kumagai; Tetsuji Anai; Kazuki Osaragi; Fumio Ohtomo - Web page: https://patentgrep.com/patent/US20130155397A1 ## CPC - G01B 11/26: for measuring angles or tapers; for testing the alignment of axes - G01C 15/002: {Active optical surveying means (optical plumbing G01C15/105)} - G01D 5/2457: {Incremental encoders having reference marks} - G01D 5/3473: {Circular or rotary encoders} - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S) - 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 rotation angle detecting apparatus comprises a bearing holder, a rotation shaft rotatably supported by said bearing holder, a shaft portion space formed in said rotation shaft, a bearing holder space formed in said bearing holder, a first condenser lens in said shaft portion space and having an optical axis that coincides with a center line of said rotation shaft, a second condenser lens in said bearing holder space and on an extension of a center line of said rotation shaft, an angle detection pattern at a focal position of one of said first and said second condenser lens, and an image sensor at a focal position of the other of said condenser lens, wherein said image sensor detects a projection image of said angle detection pattern projected onto said image sensor, and a displacement of said projection image involved by the rotation of said rotation shaft is detected. ## Claims ### Claim 1 A rotation angle detecting apparatus, comprising a bearing holder, a rotation shaft rotatably supported by said bearing holder, a shaft portion space formed in said rotation shaft, a bearing holder space formed in said bearing holder, a first condenser lens which is accommodated in said shaft portion space and has an optical axis that coincides with a center line of said rotation shaft, a second condenser lens which is provided in said bearing holder space and also provided on an extension of a center line of said rotation shaft, an angle detection pattern provided at a focal position of one of said first condenser lens and said second condenser lens, and an image sensor provided at a focal position of the other of said first condenser lens and said second condenser lens, wherein said image sensor detects a projection image of said angle detection pattern projected onto said image sensor, and a displacement of said projection image involved by the rotation of said rotation shaft is detected. ### Claim 2 (depends on 1) The rotation angle detecting apparatus according to claim 1, wherein a reference position can be set on said image sensor, and a rotational displacement amount of said angle detection pattern with respect to said reference position is detected. ### Claim 3 (depends on 1, 2) The rotation angle detecting apparatus according to claim 1 or claim 2, wherein said angle detection pattern is detected by said image sensor, a center position of an angle detection pattern image is detected based on said angle detection pattern, and a tilt angle of said rotation shaft is detected based on a deviation between the detected center position of said angle detection pattern image and said reference image on said image sensor and based on a focal length of said first condenser lens or said second condenser lens. ### Claim 4 (depends on 1, 2, 3) The rotation angle detecting apparatus according to any one of claims 1 to 3, wherein said angle detection pattern has a line-segment pattern in which line segments extending in a radial direction are arranged on a total circumference at a predetermined angle pitch and a ring-like track formed of said line segments is provided. ### Claim 5 (depends on 1, 2, 3, 4) The rotation angle detecting apparatus according to any one of claims 1 to 4, wherein said angle detection pattern has a circular pattern of one circle or a plurality of concentric circles with the center of said angle detection pattern as a center. ### Claim 6 (depends on 1, 2, 3, 4, 5) The rotation angle detecting apparatus according to any one of claims 1 to 5, wherein said angle detection pattern has a plurality of concentrically multiply-formed ring-like tracks. ### Claim 7 (depends on 1, 2, 3, 4, 5, 6) The rotation angle detecting apparatus according to any one of claims 1 to 6, wherein said angle detection pattern is detected when a detection line is set on said image sensor and a detection signal of said angle detection pattern is extracted from a signal obtained by scanning said detection line. ### Claim 8 (depends on 7) The rotation angle detecting apparatus according to claim 7, wherein said detection line is a straight line which runs through the center of said angle detection pattern on said image sensor and is set to fall within the range including each track in accordance with each track in a direction orthogonal to each radius that equally divides the circumference as required. ### Claim 9 (depends on 5) The rotation angle detecting apparatus according to claim 5, wherein said angle detection pattern is detected when a detection line is set on said image sensor and a detection signal of said angle detection pattern is extracted from a signal obtained by scanning said detection line, and said detection line is a straight line which runs through the center of said angle detection pattern on said image sensor and cuts across said circular pattern. ### Claim 10 (depends on 7) The rotation angle detection apparatus according to claim 7, wherein said detection line is a circle which is included in said track and has the center of said angle detection pattern on said image sensor as its center. ### Claim 11 (depends on 1) A surveying instrument, comprising a base unit, a frame rotatably provided on said base unit through a first rotation shaft having a vertical shaft center line, a telescope unit rotatably provided on said frame through a second rotation shaft having a horizontal shaft center line, a first rotation angle detecting apparatus which is provided between said first rotation shaft and said base unit and has the configuration according to claim 1, and a second rotation angle detecting apparatus which is provided between said second rotation shaft and said mount and has the configuration according to claim 1.