# US 6,025,907 A · Apparatus and method for measuring characteristics of optical pickup and/or optical disc > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,025,907 A - Document ID: US6025907A - Status: Granted - Kind: A - Application number: 09/182,905 - Filed: 1998-10-29 - Granted: 2000-02-15 - Earliest claimed: 1997-10-31 - Assignees: Sony Precision Engineering Center (Singapore) PTE Ltd.; Disk Ware Co. Ltd. - Inventors: Akihito Nakayama; Kenji Shintani; Shunsuke Kohama; Yukari Hashimoto - Web page: https://patentgrep.com/patent/US6025907A ## CPC - G11B 7/22: Apparatus or processes for the manufacture of optical heads, e.g. assembly - G11B 7/0037: with discs - G11B 7/123: Integrated head arrangements, e.g. with source and detectors mounted on the same substrate - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract A device for measuring characteristic values of an optical pickup and/or an optical disc capable of detecting tracking signals for measuring characteristic values even if optical disc rotation is not subjected to eccentricity. The device for measuring characteristic values of an optical pickup and/or an optical disc 1 samples outputs of photodetectors of an optical pickup 2 as signals A to F directly by a sample-and-hold circuit 8 and an analog-to-digital converter 10 to store the resulting digital data in a second memory 11. An arithmetic-logic unit 12d measures tracking error signals based on the digital data stored in the second memory 11. A signal generating circuit 25 then sends a sine wave signal to a tracking coil 2b for moving the laser light illuminated on the optical disc along the radius of the disc. ## Claims ### Claim 1 An apparatus for measuring characteristics of an optical pickup and/or an optical disc comprising: focusing servo control means responsive to an output of a photoelectric converting unit of the optical pickup for controlling a focal point position of a laser light beam illuminated on the optical disc, so as to form the laser light beam on a recording surface of the optical disc; laser control means for controlling the optical pickup for reciprocating the laser light along the radius of the optical disc; and characteristics detection means for detecting a signal for generating tracking error signals from an output of the photoelectric converting device of the optical pickup, for detecting a vicinity of a transition point in the movement direction of the illuminated position of the reciprocated laser light, for removing a signal portion of the signal generating the tracking error signals in the vicinity of the transition point and for measuring the characteristic values of the optical pickup and/or the optical disc based on the signal from which the signal portion in the vicinity of the transition point is removed. ### Claim 2 (depends on 1) The apparatus for measuring characteristics of an optical pickup and/or an optical disc as claimed in claim 1 wherein said laser control means imparts an optional wave form signal to a tracking coil adapted for moving the laser light along the radius of the optical disc for reciprocating the illuminated position of the laser light along the radius of the optical disc. ### Claim 3 (depends on 1) The apparatus for measuring characteristics of an optical pickup and/or an optical disc as claimed in claim 1 wherein said characteristics detection means detects the control amount of said laser control means for detecting sensitivity of a tracking coil adapted for moving the laser light along the radius of the optical disc based on the control amount of the laser control means, track pitch as defined by the optical disc and on the tracking signals. ### Claim 4 A method for measuring characteristics of an optical pickup or an optical disc comprising: controlling the focal position of the laser light illuminated on the optical disc based on an output of the photoelectric converting device of the optical pickup so as to focus the laser light on a recording surface of the optical disc; controlling the optical pickup for reciprocating the illuminated position of the laser light along the radius of the optical disc; detecting a signal for generating tracking error signals from an output of the photoelectric converting device of the optical pickup; detecting the vicinity of a transition point of the movement direction of the illuminated position of the reciprocated laser light; removing a signal portion of the signal for generating the tracking error signals lying in the vicinity of the transition point; and measuring the characteristic values of the optical pickup and/or the optical disc based on the signal from which the signal portion lying in the vicinity of the transition point is removed. ### Claim 5 (depends on 4) The method for measuring characteristics of an optical pickup or an optical disc as claimed in claim 4 wherein an optional wave form signal is imparted to a tracking coil moved radially of the optical disc for reciprocating the illuminated position of the laser light along the radius of the optical disc. ### Claim 6 (depends on 4) The method for measuring characteristics of an optical pickup or an optical disc as claimed in claim 4 further comprising: detecting the control amount of the laser control means for detecting the sensitivity of the tracking coil adapted for moving the laser light along the radius of the optical disc based on the control amount of the laser control means, track pitch defined by the optical disc and on the tracking signals.