# US 9,519,976 B1 · Calibrating stereoscopic cameras > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,519,976 B1 - Document ID: US9519976B1 - Status: Granted - Kind: B1 - Application number: 13/015,655 - Filed: 2011-01-28 - Granted: 2016-12-13 - Earliest claimed: 2011-01-28 - Assignees: Lucasfilm Entertainment Company Ltd. - Applicants: Jeffrey Saltzman - Inventors: Jeffrey Saltzman - Web page: https://patentgrep.com/patent/US9519976B1 ## CPC - H05B 45/22: using optical feedback - H04N 13/246: Calibration of cameras - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract A stereoscopic camera calibration target includes: first illumination points on a first surface; second illumination points on a second surface, the first and second surfaces being planar, parallel to each other, and spaced from each other; and circuitry that sets a strobe frequency of the first and second illumination points. A method includes: moving a calibration target in front of a stereoscopic camera, the calibration target comprising first points on a first surface and second points on a second surface, the first and second surfaces being planar, parallel to each other, and spaced from each other; capturing, using the stereoscopic camera, an image sequence of the calibration target, the image sequence comprising pairs of left and right images of at least some of the first and second points; determining a calibration value for the stereoscopic camera using the image sequence; and processing the image sequence using the calibration value. ## Claims ### Claim 1 A calibration target for a stereoscopic camera, the calibration target comprising: a first planar surface having a first plurality of illumination points arranged thereon; a second planar surface parallel to and spaced apart from the first planar surface, the second planar surface having a window formed therein through which at least a portion of the first planar surface is visible and having a second plurality of illumination points arranged on at least two sides of the window; and circuitry, coupled to the first and second pluralities of illumination points, configured to set a strobe frequency of the first and second pluralities of illumination points. ### Claim 2 (depends on 1) The calibration target of claim 1, wherein each of the illumination points in the first plurality of illumination points is of a color in a first plurality of colors and each of the illumination points in the second plurality of illumination points is of a color in a second plurality of colors, the first plurality of colors not comprising any of the colors in the second plurality of colors. ### Claim 3 (depends on 2) The calibration target of claim 2, wherein the first plurality of illumination points and the second plurality of illumination points are color coded according to a predefined pattern. ### Claim 4 (depends on 1) The calibration target of claim 1, wherein the second planar surface is smaller than the first planar surface such that at least a portion of the first planar surface is visible through the window in and around. ### Claim 5 (depends on 4) The calibration target of claim 4, wherein the first and second surfaces are rectangular. ### Claim 6 (depends on 1) The calibration target of claim 1, wherein the first plurality of illumination points are arranged on the first surface in a first plurality of rows and the second plurality of illumination points are arranged on the second surface in a plurality of seconds rows perpendicular to the first plurality of rows. ### Claim 7 (depends on 6) The calibration target of claim 6, further comprising a plurality of supports coupled between the first and second planar surfaces, each of the plurality of supports having a length substantially equal to a distance the first and second planar surfaces are spaced apart from each other wherein the second illumination points are arranged in a second row on the second surface, the second row perpendicular to the first row. ### Claim 8 (depends on 1) The calibration target of claim 1, wherein the circuitry is configured to sets the strobe frequency based on user input to the circuitry. ### Claim 9 (depends on 1) The calibration target of claim 1, wherein the circuitry is configured to set strobe frequency based at least in part on a shutter speed value of the stereoscopic camera. ### Claim 10 (depends on 9) The calibration target of claim 9, wherein the circuitry comprises an interface for receiving a frame speed value and a shutter angle value, and wherein the circuitry determines the shutter speed based on the frame speed and shutter angle. ### Claim 11 (depends on 1) The calibration target of claim 1, wherein each of the first and second pluralities of illumination points comprises a light emitting diode controlled by the circuitry. ### Claim 12 (depends on 1) The calibration target of claim 1, wherein each of the first and second pluralities of illumination points comprises a light tube controlled by the circuitry. ### Claim 13 A method comprising: moving a calibration target in front of a stereoscopic camera, the calibration target comprising first points on a first planar surface and second points on a second planar surface parallel to and spaced apart from the first planar surface, the second planar surface having a window formed therein through which at least a portion of the first planar surface is visible; capturing, using the stereoscopic camera, an image sequence of the calibration target, the image sequence comprising pairs of left and right images of at least some of the first and second points; determining a calibration value for the stereoscopic camera using the image sequence; and processing the image sequence using the calibration value. ### Claim 14 (depends on 13) The method of claim 13, wherein the first and second points include illumination points, and the method further comprises strobing the illumination points at a strobe frequency while capturing the image sequence. ### Claim 15 (depends on 14) The method of claim 14, further comprising determining a frame speed, the strobe frequency selected based on the frame speed. ### Claim 16 (depends on 13) The method of claim 13, wherein the first points are out of focus in the image sequence. ### Claim 17 (depends on 16) The method of claim 16, further comprising performing a center-finding technique. ### Claim 18 (depends on 13) The method of claim 13, wherein determining the calibration value comprises: (i) creating a virtual calibration target, and virtual stereoscopic camera with the image sequence, in a virtual world (ii) identifying representations of at least some of the first and second points in the image sequence, and (iii) adjusting the virtual stereoscopic camera to match the identified representations. ### Claim 19 A system comprising: a stereoscopic camera; and a calibration target for the stereoscopic camera, the calibration target comprising first points on a first planar surface and second points on a second planar surface parallel to and spaced apart from the first surface, the second planar surface having a window formed therein through which at least a portion of the first planar surface is visible and having a second plurality of illumination points arranged on at least two sides of the window. ### Claim 20 (depends on 19) The system of claim 19, wherein the first and second points include illumination points, and the system further comprise circuitry that sets a strobe frequency of the illumination points. ### Claim 21 (depends on 20) The system of claim 20, wherein the circuitry sets the strobe frequency to any of multiple predefined strobe frequencies; and wherein the set strobe frequency is based at least in part on a shutter speed of the stereoscopic camera. ### Claim 22 (depends on 21) The system of claim 21, wherein the circuitry comprises an interface for receiving a frame speed value and a shutter angle value, and wherein the circuitry determines the shutter speed based on the frame speed and shutter angle.