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US 2017/0318240 A1Published application
Methods and apparatus for automated noise and texture optimization of digital image sensors
AssigneeQUALCOMM Incorporated
InventorSang Cheol Yu
Life of this patent
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Abstract
Systems and methods are disclosed for calibrating an image sensor using a source image taken from the image sensor and comparing it to a reference image. In one embodiment, the method may involve determining the luminance and chrominance values of portions of the image at successive frequency levels and calculating a standard deviation at each frequency level for both the source image and the reference image. The standard deviation values may be compared and a difference determined. Using unit vector search vectors, noise values may be calculated to determine sensor calibration values.
Claims30
A method of tuning a noise level of an image sensor, the method comprising:
- determining a first set of frequency levels of an image produced by the image sensor using a set of low pass filters, the set of low pass filters comprising at least one bilateral low pass filter;
- determining a first set of chrominance noise values and luminance noise values corresponding to each frequency level of the first set of frequency levels;
- calculating a target set of noise values associated with each frequency level of the first set of frequency levels, the target set of noise values calculated based on comparing the first set of chrominance and luminance noise values to a second set of chrominance and luminance noise values of a reference image, the reference image captured using a calibrated image sensor;
- determining a first set of noise values associated with the image using a coarse search, the coarse search based on a first set of vectors, wherein each noise value of the first set of noise values corresponds to a frequency level of the first set of frequency levels;
- determining a second set of noise values associated with the image using a fine search, the fine search comprising a second set of vectors, wherein the second set of vectors are determined based on a noise value difference between the target set of noise values and the first set of noise values, wherein each noise value of the second set of noise values corresponds to a frequency level of the first set of frequency levels;
- updating a coefficient of the at least one bilateral low pass filter based on a difference between the second set of noise values and the first set of noise values;
- and
- adjusting the noise level of each pixel of the image sensor via applying the at least one bilateral low pass filter with the updated coefficient according to the target set of noise values.
5 more elements
An apparatus for tuning a noise level of an image sensor, the apparatus comprising:
- an image sensor configured to produce an image;
- a processor configured to:
- determine a first set of frequency levels of the image produced by the image sensor using a set of low pass filters, the set of low pass filters comprising at least one bilateral low pass filter;
- determine a first set of chrominance noise values and luminance noise values corresponding to each frequency level of the first set of frequency levels;
- calculate a target set of noise values associated with each frequency level of the first set of frequency levels, the target set of noise values calculated based on comparing the first set of chrominance and luminance noise values to a second set of chrominance and luminance noise values of a reference image, the reference image captured using a calibrated image sensor;
- determine a first set of noise values associated with the image produced by the image sensor using a coarse search, the coarse search based on a first set of vectors, wherein each noise value of the first set of noise values corresponds to a frequency level of the first set of frequency levels;
- determine a second set of noise values associated with the image produced by the image sensor using a fine search, the fine search comprising a second set of vectors, wherein the second set of vectors are determined based on a noise value difference between the target set of noise values and the first set of noise values, wherein each noise value of the second set of noise values corresponds to a frequency level of the first set of frequency levels;
- and
- update a coefficient of the at least one bilateral low pass filter based on a difference between the second set of noise values and the first set of noise values;
- and
- adjust the noise level of each pixel of the image sensor via applying the at least one bilateral low pass filter with the updated coefficient.
8 more elements
An apparatus, comprising:
- means for determining a first set of frequency levels of an image produced by an image sensor using a set of low pass filters, the set of low pass filters comprising at least one bilateral low pass filter;
- means for determining a first set of chrominance noise values and luminance noise values corresponding to each frequency level of the first set of frequency levels;
- means for calculating a target set of noise values associated with each frequency level of the first set of frequency levels, the target set of noise values calculated based on comparing the first set of chrominance and luminance noise values to a second set of chrominance and luminance noise values of a reference image, the reference image captured using a calibrated image sensor;
- means for determining a first set of noise values associated with the image produced by the image sensor using a coarse search, the coarse search based on a first set of vectors, wherein each noise value of the first set of noise values corresponds to a frequency level of the first set of frequency levels;
- means for determining a second set of noise values associated with the image produced by the image sensor using a fine search, the fine search comprising a second set of vectors, wherein the second set of vectors are determined based on a noise value difference between the target set of noise values and the first set of noise values, wherein each noise value of the second set of noise values corresponds to a frequency level of the first set of frequency levels;
- and
- means for updating a coefficient of the at least one bilateral low pass filter based on a difference between the second set of noise values and the first set of noise values;
- and
- means for adjusting a noise value of each pixel of the image sensor via applying the at least one bilateral low pass filter with the updated coefficient.
6 more elements
A non-transitory, computer-readable medium comprising instructions executable by a processor of an apparatus, that causes the apparatus to:
- determine a first set of frequency levels of an image produced by an image sensor using a set of low pass filters, the set of low pass filters comprising at least one bilateral low pass filter;
- determine a first set of chrominance noise values and luminance noise values corresponding to each frequency level of the first set of frequency levels;
- calculate a target set of noise values associated with each frequency level of the first set of frequency levels, the target set of noise values calculated based on comparing the first set of chrominance and luminance noise values to a second set of chrominance and luminance noise values of a reference image, the reference image captured using a calibrated image sensor;
- determine a first set of noise values associated with the image produced by the image sensor using a coarse search, the coarse search based on a first set of vectors, wherein each noise value of the first set of noise values corresponds to a frequency level of the first set of frequency levels;
- determine a second set of noise values associated with the image produced by the image sensor using a fine search, the fine search comprising a second set of vectors, wherein the second set of vectors are determined based on a noise value difference between the target set of noise values and the first set of noise values, wherein each noise value of the second set of noise values corresponds to a frequency level of the first set of frequency levels;
- update a coefficient of the at least one bilateral low pass filter based on a difference between the second set of noise values and the first set of noise values;
- and
- adjust a noise value of each pixel of the image sensor via applying the at least one bilateral low pass filter with the updated coefficient.
5 more elements
Dependencies are inferred from the claim text.