# US 2014/0191119 A1 · Single track three-channel encoder with differential index > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0191119 A1 - Document ID: US20140191119A1 - Status: Published application - Kind: A1 - Application number: 13/737,756 - Filed: 2013-01-09 - Published: 2014-07-10 - Earliest claimed: 2013-01-09 - Assignees: Avago Technologies General IP (Singapore) Pte. Ltd. - Inventors: Marcin Kamil Augustyniak; Aun Choon Chong; Kek Leong Yap - Web page: https://patentgrep.com/patent/US20140191119A1 ## CPC - G01D 5/34715: {Scale reading or illumination devices} - 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 An optical encoder is disclosed. Specifically, a three-channel encoder is disclosed which utilizes a single track for all three channels. An index channel is provided on the same optical track as the first and second channels which are used to determine incremental angular position. Thus, a more compact and simple three-channel encoder is provided. ## Claims ### Claim 1 An encoder for use in an optical encoding system, comprising: an emitter configured to emit light; a detector configured to receive at least a portion of the light emitted by the emitter and convert the received light into one or more electrical signals which are used to generate three output signals, wherein the light used to generate the three output signals at least one of passed through and was reflected by a single optical track of a coding element, and wherein one of the three output signals comprises a differential index signal. ### Claim 2 (depends on 1) The encoder of claim 1, wherein the detector comprises a sensor area that includes an array of incremental photodiodes, a first index photodiode that generates a first index output, and a second index photodiode that generates a second index output, the second index output being subtracted from the first index output to generate the differential index signal. ### Claim 3 (depends on 2) The encoder of claim 2, wherein the array of incremental photodiodes are arranged between the first index photodiode and the second index photodiode. ### Claim 4 (depends on 3) The encoder of claim 3, wherein the first index photodiode comprises a width that is at least four times larger than a width of an incremental photodiode in the array of index photodiodes. ### Claim 5 (depends on 4) The encoder of claim 4, wherein the second index photodiode comprises a width that is substantially equal to the width of the first index photodiode. ### Claim 6 (depends on 2) The encoder of claim 2, wherein the single optical track comprises an index bar, an index window, and at least one non-index bar that separates the index bar from the index window. ### Claim 7 (depends on 6) The encoder of claim 6, wherein a distance between a center of the index window and a center of the index bar substantially equals a distance between a center of the first index photodiode and a center of the second index photodiode. ### Claim 8 (depends on 1) The encoder of claim 1, wherein the single optical track is at least one of radially and linearly-oriented. ### Claim 9 A system for translating physical motion of a device into an electrical signal, the system comprising: an encoder comprising: a sensor area that includes an array of incremental photodiodes, a first index photodiode, and a second index photodiode; a coding element having a single optical track that includes an index bar, an index window, and at least one non-index bar, the coding element being mechanically coupled to the device, the single optical track being positioned in proximity to the sensor area; and signal processing circuitry coupled to the sensor area and being configured to output at least three output signals, at least one of the three output signals corresponding to an index signal that is generated based on inputs received from the first index photodiode and the second photodiode. ### Claim 10 (depends on 9) The system of claim 9, wherein the index signal is generated by subtracting an input received from the second index photodiode from an input received from the first index photodiode. ### Claim 11 (depends on 10) The system of claim 10, wherein the index signal is generated when the index window overlies the second index photodiode and the index bar overlies the first index photodiode. ### Claim 12 (depends on 9) The system of claim 9, wherein a distance between a center of the index window and a center of the index bar substantially equals a distance between a center of the first index photodiode and a center of the second index photodiode. ### Claim 13 (depends on 9) The system of claim 9, wherein the array of incremental photodiodes include an A-signal photodiode, a B-signal photodiode, an AB-signal photodiode, and a BB-signal photodiode. ### Claim 14 (depends on 13) The system of claim 13, wherein the array of incremental photodiodes are used to produce an A-channel output signal and a B-channel output signal. ### Claim 15 A coding element configured for use in an optical encoding system, the coding element comprising: an optical track having an index bar, an index window, and at least one non-index bar, the index bar and index window being spaced apart from each other in such a way as to produce an index signal in addition to an A-channel output signal and a B-channel output signal. ### Claim 16 (depends on 15) The coding element of claim 15, wherein the index bar and the at least one non-index bar comprise non-reflective sections of the coding element. ### Claim 17 (depends on 15) The coding element of claim 15, wherein the index window comprises at least one of a reflective and optically-transmissive material. ### Claim 18 (depends on 15) The coding element of claim 15, wherein the optical track is substantially linear. ### Claim 19 (depends on 15) The coding element of claim 15, wherein the optical track is radially-disposed. ### Claim 20 (depends on 15) The coding element of claim 15, wherein the index window is at least one-and-a-half times wider than the at least one non-index bar.