LENS SHADING CALIBRATION FOR CAMERAS
First Claim
1. A method for performing lens shading correction, the method comprising:
- generating a plurality of base surface measurements of a camera module type, the plurality of base surface measurements comprising a base surface measurement for each illuminant of a plurality of illuminants;
measuring a shading profile specific to each camera module of the camera module type to calculate a module-specific calibration surface;
creating a module-specific corrected surface measurement for each illuminant of the plurality of illuminants based on the plurality of base surface measurements of the camera module type and the module-specific calibration surface; and
wherein, each camera module of the plurality of camera modules is operable to be used in a mobile computing device.
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Abstract
Embodiments of the present invention are directed to methods and systems for performing automatic lens shading correction using module-specific calibrations. According to one aspect of the invention, a method is provided that is performed over three main stages. During a first stage, radial symmetric component data is determined that is common to camera modules of the type to be calibrated. During the second stage, the actual measurement of the shading profile of one or more specific camera modules is performed. In the third and final stage is the extrapolation stage, the base measurement surfaces of a camera module type determined in the first stage are extrapolated and modified with the module-specific Bezier correction surface and calibration data of the second stage. The output surfaces of this third and final stage are used to correct for the shading profile in the camera module, depending on the light-source estimation.
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Citations
30 Claims
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1. A method for performing lens shading correction, the method comprising:
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generating a plurality of base surface measurements of a camera module type, the plurality of base surface measurements comprising a base surface measurement for each illuminant of a plurality of illuminants; measuring a shading profile specific to each camera module of the camera module type to calculate a module-specific calibration surface; creating a module-specific corrected surface measurement for each illuminant of the plurality of illuminants based on the plurality of base surface measurements of the camera module type and the module-specific calibration surface; and wherein, each camera module of the plurality of camera modules is operable to be used in a mobile computing device. - View Dependent Claims (2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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5. The method according to claim 61, wherein a base surface measurement of the plurality of base surface measurements comprises at least one of:
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a plurality of relative illumination characteristics of a lens comprised in the camera module; a profile of a chief ray angle of a sensor comprised in the camera module; a spectral response of an infrared filter comprised in the camera module.
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27. An image capture device, said device comprising:
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an image capture module comprising a lens, an image sensor and an image signal processor, the image capture module being configured to generate an image of a scene comprising a set of image data; a memory, communicatively coupled to the image capture module, and configured to store the set of image data and a plurality of programmed instructions; and a processor, communicatively coupled to the memory, and configured to execute the plurality of programmed instructions and to perform a lens shading correction method on the set of image data, the method comprising; i) referencing a plurality of base surface measurements corresponding to a type of the image capture module and a shading profile specific to the image capture module to create a plurality of module-specific corrected surface measurements; ii) determining an illuminant present in the scene; iii) selecting a module-specific corrected surface measurement from the plurality of module-specific corrected surface measurements to correspond to the illuminant; and iv) applying the selected module-specific corrected surface measurement to the image data. - View Dependent Claims (28)
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29. A computer readable medium containing program instructions embodied therein for causing a camera module in an image capture device to perform lens shading correction, the program instructions comprising:
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instructions to reference, from a memory in an image capture device, a plurality of base surface measurements of a camera module type corresponding to the camera module, the plurality of base surface measurements comprising a base surface measurement for each illuminant of a plurality of illuminants; instructions to reference, from the memory, a shading profile specific to the camera module of the camera module type to calculate a module-specific calibration surface; instructions to create a module-specific corrected surface measurement for each illuminant of the plurality of illuminants based on the plurality of base surface measurements of and the module-specific calibration surface; instructions to capture a scene with the camera module; instructions to determine an illuminant in the scene captured by the camera module; and instructions to apply the module-specific corrected surface measurement corresponding to the determined illuminant to an image data corresponding to the scene. - View Dependent Claims (30)
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Specification