# US 2013/0155166 A1 · Optical scanning apparatus and image forming device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0155166 A1 - Document ID: US20130155166A1 - Status: Published application - Kind: A1 - Application number: 13/718,514 - Filed: 2012-12-18 - Published: 2013-06-20 - Earliest claimed: 2011-12-19 - Assignees: Ricoh Company, Ltd. - Inventors: Naoto WATANABE; Toshiaki TOKITA; Kohji SAKAI; Nobuaki KUBO; Masayuki MURANAKA - Web page: https://patentgrep.com/patent/US20130155166A1 ## CPC - B41J 2/473: {using multiple light beams, wavelengths or colours} - B41J 2/471: {using dot sequential main scanning by means of a light deflector, e.g. a rotating polygonal mirror} - G02B 26/123: {Multibeam scanners, e.g. using multiple light sources or beam splitters} - G02B 26/127: {Adaptive control of the scanning light beam, e.g. using the feedback from one or more detectors (G02B27/0031 takes precedence)} - G02B 26/129: {Systems in which the scanning light beam is repeatedly reflected from the polygonal mirror} - G03G 15/043: with means for controlling illumination or exposure (G03G15/041 takes precedence) - G03G 15/505: {Detecting the speed, e.g. for continuous control of recording starting time} - B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract An optical scanning apparatus includes a light source, an optical deflector having a rotary polygon mirror to deflect a light beam from the light source, a scanning optical system configured to focus the light beam deflected by the optical deflector on a target surface, a sync detecting sensor configured to determine a write start timing on the target surface, and a processing unit configured to correct detection data of the sync detecting sensor based on a measured value of a time needed for one revolution of the rotary polygon mirror. ## Claims ### Claim 1 An optical scanning apparatus, comprising: a light source; an optical deflector having a rotary polygon mirror to deflect a light beam from the light source; a scanning optical system configured to focus the light beam deflected by the optical deflector on a target surface to be scanned; a sync detecting sensor configured to determine a write start timing on the target surface; and a processing unit configured to correct detection data of the sync detecting sensor based on a measured value of a time needed for one revolution of the polygon mirror. ### Claim 2 (depends on 1) The optical scanning apparatus according to claim 1, wherein the processing unit is configured to determine a write start timing on a target surface different from the target surface based on the corrected detection data. ### Claim 3 (depends on 1) The optical scanning apparatus according to claim 1, wherein the processing unit is configured to determine a write start timing on the target surface based on the corrected detection data. ### Claim 4 (depends on 1) The optical scanning apparatus according to claim 1, wherein the processing unit is configured to correct the detection data of the sync detecting sensor in accordance with the formula: (the corrected detection data)=(a measured value T of a time needed for one revolution of the rotary polygon mirror)/(an average Tave of history data of the measured value). ### Claim 5 (depends on 2) The optical scanning apparatus according to claim 2, wherein the processing unit is configured to determine a first write start timing on a first target surface based on the detection data of the sync detecting sensor, and determine a second write start timing on a second target surface based on the corrected detection data, and wherein a face of the polygon mirror which deflects the light beam used to determine the first write start timing is the same as the face of the polygon mirror which deflects the light beam used to determine the second write start timing. ### Claim 6 (depends on 3) The optical scanning apparatus according to claim 3, wherein the light source and the sync detecting sensor are mounted on a single substrate. ### Claim 7 (depends on 1) An image forming device comprising: a photoconductive drum; and the optical scanning apparatus according to claim 1, wherein the optical scanning apparatus is arranged to optically scan the photoconductive drum by the light beam. ### Claim 8 An image forming device including a processing unit to control the image forming device, the processing unit comprising: a first sync signal generating part configured to detect scanning timing of a first photoconductor and generate a first sync signal; a first counter configured to receive the first sync signal and a first pixel clock and measure a rotational period of a rotary polygon mirror; a first pixel clock generating part configured to adjust the frequency of the first pixel clock to make the rotational period measured by the first counter equal to a predetermined value; and a false sync signal generating part configured to generate a false sync signal for measuring timing of scanning of a second photoconductor, based on the first sync signal and the first pixel clock. ### Claim 9 (depends on 8) The image forming device according to claim 8, wherein the first pixel clock generating part outputs the first pixel clock and a frequency correction value which is a difference between a frequency of the first pixel clock and a predetermined frequency, and wherein the processing unit further comprises: a second pixel clock generating part configured to output a second pixel clock that is in sync with the first sync signal, at a frequency corrected by the frequency correction value; and a third pixel clock generating part configured to output a third pixel clock that is in sync with the false sync signal, at the frequency corrected by the frequency correction value. ### Claim 10 (depends on 8) The image forming device according to claim 8, wherein the first counter is configured to measure an input interval of the first sync signal for each of the faces of the polygon mirror and output an average of the intervals of the first sync signal measured for the number of the faces of the polygon mirror. ### Claim 11 (depends on 9) The image forming device according to claim 9, wherein an initial value of the frequency of the second pixel clock and an initial value of the frequency of the third pixel clock are predetermined individually. ### Claim 12 (depends on 11) The image forming device according to claim 11, wherein the processing unit further comprises: a fourth pixel clock generating part configured to generate a fourth pixel clock which is oscillated in sync with the first sync signal at a frequency obtained from a first initial frequency setting value corrected by the frequency correction value, or oscillated in sync with the false sync signal at a frequency obtained from a second initial frequency setting value corrected by the frequency correction value. ### Claim 13 (depends on 8) The image forming device according to claim 8, wherein the processing unit further comprises: a second sync signal generating part configured to detect a timing of scanning of a third photoconductor by a third light beam deflected by the polygon mirror and generate a second sync signal; and a second false sync signal generating part configured to generate a second false sync signal which measures timing of scanning of a fourth photoconductor by a fourth light beam deflected by the polygon mirror, using the first pixel clock. ### Claim 14 (depends on 13) The image forming device according to claim 13, further comprising: a fifth pixel clock generating part configured to output a fifth pixel clock that is in sync with the second sync signal at a frequency corrected by the frequency correction value; and a sixth pixel clock generating part configured to output a sixth pixel clock that is in sync with the second false sync signal at the frequency corrected by the frequency correction value. ### Claim 15 (depends on 14) The image forming device according to claim 14, wherein an initial value of the frequency of the second pixel clock, an initial value of the frequency of the third pixel clock, an initial value of the frequency of the fifth pixel clock, and an initial value of the frequency of the sixth pixel clock are predetermined individually. ### Claim 16 (depends on 15) The image forming device according to claim 15, wherein the processing unit further comprises: a seventh pixel clock generating part configured generate a seventh pixel clock which is oscillated in sync with the second sync signal at a frequency obtained from a third initial frequency setting value corrected by the frequency correction value, or oscillated in sync with the second false sync signal at a frequency obtained from a fourth initial frequency setting value corrected by the frequency correction value.