Radiometric calibration using temporal irradiance mixtures
AssigneeMicrosoft Corporation
InventorsYasuyuki Matsushita, Bennett S. Wilburn
Life of this patent
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Abstract
A method of calibrating a brightness value measured by a camera with an amount of light received by the camera includes creating a series of measurements, wherein for each measurement the amount of light received at an image plane in the camera is controlled to be a known ratio of two opposed irradiance values: a high irradiance value and a low irradiance value. Each ratio is correlated with the brightness value measured by the camera. A function is obtained describing the correlation.
Claims20
A method of calibrating a brightness value measured by a camera with an amount of light received by the camera, the method comprising:
- creating a series of measurements, by moving the camera at a constant velocity relative to a target or by moving the target at a constant velocity relative to the camera, wherein a relative motion between the camera and target is in a plane substantially parallel to a plane of the target, wherein for each measurement the amount of light received at an image plane in the camera is controlled to be a known ratio of two opposed irradiance values:
- a high irradiance value and a low irradiance value;
- correlating each ratio with the brightness value measured by the camera;
- and
- obtaining a function describing the correlation.
A method of calibrating a brightness value measured by a camera with an amount of light received by the camera, the method comprising:
- taking a single exposure image with the camera by moving the camera at a constant velocity relative to a target or by moving the target at a constant velocity relative to the camera, wherein a relative motion between the camera and target is in a plane substantially parallel to a plane of the target, the image being divided spatially into a plurality of patches, the exposure being divided in time into a plurality of frames, each frame representing a fraction of exposure time, wherein the amount of light received at a patch is constrained to one of two opposed irradiance values:
- a high irradiance value and a low irradiance value, and wherein the plurality of patches exhibit the high irradiance values and the low irradiance values for varying numbers of frames, to sample a range between the two opposed irradiance values;
- for each patch, determining a ratio of the number of frames in which the patch exhibits the high irradiance value to the number of frames in which the patch exhibits the low irradiance value;
- correlating each ratio with the brightness value measured by the camera;
- and
- obtaining a function describing the correlation.
A calibration system comprising:
- a camera configured to measure a brightness value and receive an amount of light at an image plane in the camera, wherein a series of measurements are created by moving the camera at a constant velocity relative to a target or by moving the target at a constant velocity relative to the camera, and wherein a relative motion between the camera and target is in a plane substantially parallel to a plane of the target, and wherein for each measurement the amount of light received at an image plane in the camera is controlled to be a known ratio of two opposed irradiance values, comprising a high irradiance value and a low irradiance value;
- and
- a computer processor configured to correlate each ratio with the brightness value measured by the camera and obtain a function describing the correlation.
Dependencies are inferred from the claim text.