# US 5,347,340 A · Camera having a focus detection device and interchangeable lens > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,347,340 A - Document ID: US5347340A - Status: Granted - Kind: A - Application number: 08/136,108 - Filed: 1993-10-14 - Granted: 1994-09-13 - Earliest claimed: 1992-10-15 - Assignees: Nikon Corporation - Inventors: Shinichi Tsukada - Web page: https://patentgrep.com/patent/US5347340A ## CPC - G02B 7/28: Systems for automatic generation of focusing signals - G03B 13/36: Autofocus systems - G03B 17/14: interchangeably - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - 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) ## Abstract A focus detection device for a camera which corrects the focal point position of an interchangeable camera lens. The focal point position is corrected according to data indicating interchangeable lens characteristics, and according to data indicating characteristics of a focus detection device. The data indicating characteristics of the interchangeable lens is data representing the field curvature of the interchangeable lens which is stored in a memory located in the interchangeable lens. The data indicating characteristics of the focus detection device is data representing the size of a detection aperture of the focus detection device, a direction of detection, and a position of the detection region within a photographic image surface. This data is stored in a memory located in the camera. Reliable focal point correction may be performed when the interchangeable lens is mounted on a camera loaded with a focus detection device having optional detection aperture size, detection direction, and detection position. Furthermore, the quantity of data which has to be stored in the memory of the interchangeable lens is decreased. Focal point correction for an interchangeable lens may also be performed when plural focus detection devices in the camera perform focal point detection in plural detection regions. ## Claims ### Claim 1 A focus detection device for a camera which is capable of accommodating an interchangeable lens, comprising: (a) focus detection means for performing focus detection in a detection region, and for outputting a focal point position; (b) memory means for storing data representing a field curvature of the interchangeable lens, and for storing data representing characteristics of the focus detection means; and (c) correction means for correcting the focal point position output by the focus detection means based upon the data stored in the memory means representing the field curvature of the interchangeable lens and based upon the data representing characteristics of the focus detection means. ### Claim 2 (depends on 1) The focus detection device, as recited in claim 1, wherein the data representing the characteristics of the focus detection means is data representing the size of a detection aperture of the focus detection means, a detection direction, and a position of the detection region. ### Claim 3 (depends on 1) The focus detection device as recited in claim 1, wherein the memory means includes a first memory located in the interchangeable lens for storing data representing the field curvature of the interchangeable lens, and a second memory located in the camera for storing data representing the characteristics of the focus detection means. ### Claim 4 (depends on 1) The focus detection device as recited in claim 1, wherein the data representing the field curvature of the interchangeable lens is coefficients of an equation defining field curvature of the interchangeable lens, and the equation is a polynomial having image height as a variable. ### Claim 5 (depends on 4) The focus detection device, as recited in claim 4, wherein the field curvature is a field curvature in a radial direction and in a tangential direction of the interchangeable lens. ### Claim 6 (depends on 1) The focus detection device, as recited in claim 1, wherein the data representing the field curvature of the interchangeable lens is data representing plural field curvatures corresponding to plural stop states of the interchangeable lens. ### Claim 7 (depends on 6) The focus detection device, as recited in claim 6, wherein the field curvature is the field curvature in the radial direction and in the tangential direction of the interchangeable lens. ### Claim 8 (depends on 6) The focus detection device, as recited in claim 6, wherein the data representing the field curvature of the interchangeable lens is coefficients of polynomials which represent field curvature of the interchangeable lens, and the polynomials have image height as a variable. ### Claim 9 (depends on 1) The focus detection device, as recited in claim 1, wherein the detection region is a region within a photographic image surface located in the camera. ### Claim 10 A camera, comprising: (a) a camera body; (b) an interchangeable lens mountable on the camera body; (c) a focus detection device located in the camera body which performs focus detection for a detection region, and which outputs a focal point position; (d) a lens memory located in the interchangeable lens which stores data representing a field curvature of the interchangeable lens; (e) a camera memory located in the camera body which stores data representing characteristics of the focus detection device; and (f) a correction unit which corrects the focal point position based upon the data stored in the interchangeable lens and the data stored in the camera memory. ### Claim 11 (depends on 10) The camera, as recited in claim 10, wherein the data representing characteristics of the focus detection device is data indicating the size of a detection aperture of the focus detection device, a detection direction, and a position of the detection region. ### Claim 12 (depends on 10) The camera, as recited in claim 10, wherein the data representing the field curvature of the interchangeable lens is coefficients of an equation defining field curvature of the interchangeable lens, and the equation is a polynomial having image height as a variable. ### Claim 13 (depends on 12) The camera, as recited in claim 12, wherein the field curvature is a field curvature in a radial direction and in a tangential direction of the interchangeable lens. ### Claim 14 (depends on 10) The camera, as recited in claim 10, wherein the data representing the field curvature of the interchangeable lens is data representing plural field curvatures corresponding to plural stop states of the interchangeable lens. ### Claim 15 (depends on 14) The camera, as recited in claim 14, wherein the field curvature is the field curvature in the radial direction and in the tangential direction of the interchangeable lens. ### Claim 16 (depends on 14) The camera, as recited in claim 14, wherein the data representing the field curvature of the interchangeable lens is coefficients of polynomials which represent field curvature of the interchangeable lens, and the polynomials have image height as a variable. ### Claim 17 (depends on 10) The camera, as recited in claim 10, wherein the detection region is a region within a photographic image surface located in the camera body. ### Claim 18 A camera, comprising: (a) a camera body; (b) an interchangeable lens mountable on the camera body; (c) a first focus detection device located in the camera body which performs focus detection in a first detection region, and which outputs a first detected focal point position; (d) a second focus detection device located in the camera body which performs focus detection in a second detection region, and which outputs a second detected focal point position corresponding to the second detection region; (e) a lens memory located in the interchangeable lens which stores data representing a field curvature of the interchangeable lens; (f) a camera memory located in the camera body which stores data representing characteristics of the first detection device, and data representing characteristics of the second detection device; and (g) a correction unit which corrects the focal point position based upon the data stored in the interchangeable lens and the data stored in the memory located in the camera body.