# US 8,786,762 B2 · Imaging device and automatic focus adjustment method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,786,762 B2 - Document ID: US8786762B2 - Status: Granted - Kind: B2 - Application number: 13/032,972 - Filed: 2011-02-23 - Published: 2011-08-25 - Granted: 2014-07-22 - Earliest claimed: 2010-02-25 - Assignees: Olympus Imaging Corp. - Applicants: Satoru Ito - Inventors: Satoru Ito - Web page: https://patentgrep.com/patent/US8786762B2 ## CPC - G03B 13/36: Autofocus systems - G02B 7/36: using image sharpness techniques {, e.g. image processing techniques for generating autofocus signals (image data processing per se G06T; in cameras having a solid state image sensor H04N23/67)} - G03B 3/10: Power-operated focusing - H04N 23/61: based on recognised objects - H04N 23/673: {based on contrast or high frequency components of image signals, e.g. hill climbing method} - G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract An imaging device of the present invention comprises an imaging section for forming a subject image using a photographing lens and generating image data, a contrast detection section for detecting contrast values corresponding to contrast of the subject image, for every position of the photographing lens, based on the image data, a subject brightness detection section for detecting brightness evaluation values corresponding to subject brightness of the subject image for every position of the photographing lens, based on the image data, a correction section for correcting the contrast values depending on a brightness evaluation value for a corresponding position of the photographing lens and calculating corrected contrast value, and a focus detection section for detecting a focus position of the photographing lens based on the corrected contrast values that have been corrected by the correction section. ## Claims ### Claim 1 An imaging device comprising: an imaging section for forming a subject image using a photographing lens, and generating image data; a contrast detection section for detecting contrast values corresponding to contrast of the subject image, for every position of the photographing lens, based on the image data; a subject brightness detection section for detecting brightness evaluation values corresponding to subject brightness of the subject image for every position of the photographing lens, based on the image data; a correction section for correcting the contrast values depending on a brightness evaluation value for a corresponding position of the photographing lens and calculating corrected contrast values; and a focus detection section for detecting a focus position of the photographing lens based on the corrected contrast values that have been corrected by the correction section, wherein the correction section calculates a ratio relating to the brightness evaluation values as a correction coefficient, and corrects the contrast values using the correction coefficient, and wherein the correction section adjusts the correction coefficient according to the contrast values. ### Claim 2 (depends on 1) The imaging device of claim 1, wherein: the correction section compares the contrast values with a specified threshold level, and determines whether or not to adjust the correction coefficient. ### Claim 3 (depends on 2) The imaging device of claim 2, wherein: the correction section changes the threshold value according to sensitivity of the imaging section. ### Claim 4 (depends on 1) The imaging device of claim 1, wherein: the correction section determines whether or not to adjust the correction coefficient depending on subject brightness when the image data is acquired. ### Claim 5 (depends on 1) The imaging device of claim 1, further comprising: a face detecting section for detection an image portion corresponding to a face in the image data, and wherein the correction section determines whether or not to adjust the correction coefficient depending on whether or not a portion of a face is contained in the image data. ### Claim 6 An automatic focusing method for an imaging device having an image sensor, comprising: forming an image using a lens to generate image data by the image sensor; detecting contrast values corresponding to contrast of the subject image, for every position of the lens, based on the image data; detecting brightness evaluation values corresponding to brightness of the image for every position of the lens, based on the image data; correcting the contrast values depending on a brightness evaluation value for a corresponding position of the lens and calculating corrected contrast values; and detecting a focus position of the lens based on the corrected contrast values, wherein a ratio relating to the brightness evaluation values is calculated as a correction coefficient, and the contrast values are corrected using the correction coefficient to give the corrected contrast values, and wherein the correction coefficient is adjusted according to the contrast values. ### Claim 7 (depends on 6) The automatic focus adjustment method of claim 6, wherein the contrast values are compared with a specified threshold level, and it is determined whether or not to adjust the correction coefficient. ### Claim 8 (depends on 7) The automatic focus adjustment method of claim 7, wherein threshold value is changed according to sensitivity as the time of generating image data by forming the image. ### Claim 9 (depends on 6) The automatic focus adjustment method of claim 6, wherein whether or not to adjust the correction coefficient is determined depending on subject brightness when the image data is acquired. ### Claim 10 (depends on 6) The automatic focus adjustment method of claim 6, wherein whether or not to adjust the correction coefficient is determined depending on whether or not a portion corresponding to a face is contained in the image data.