Apparatus and method for eliminating artifacts in active pixel sensor (APS) imagers
View Patent ↗An active pixel sensor (APS) that includes circuitry to eliminate artifacts in digital images. The APS includes a comparator for comparing a signal level from a pixel to an adjusted saturation voltage to determine if the pixel is saturated. If the pixel is saturated, the signal output from the pixel is replaced with an analog voltage having a maximum value corresponding to a brightest pixel in the image.
1. A method of operating an imager, comprising:
obtaining an analog pixel value from an imaging pixel of an image sensor;
analog to digital converting the analog pixel value to obtain a digital pixel value corresponding to the analog pixel value;
comparing the obtained digital pixel value to a predetermined saturated value;
determining the obtained digital pixel value meets or exceeds the predetermined saturated value; and
replacing the obtained digital pixel value with a different digital pixel value corresponding to a predetermined brightest pixel value, wherein the predetermined brightest pixel value is independent of digital pixel values of imaging pixels and the image sensor.
2. The method of claim 1 , wherein the predetermined digital pixel value is a predetermined value that is less than said predetermined saturated value.
3. An imaging system comprising:
an imaging pixel of an image sensor providing an analog pixel value;
an analog to digital converter for converting the analog pixel value to a digital pixel value corresponding to the analog pixel value; and
a digital circuit for receiving and processing the digital pixel value, the digital circuit being configured to:
compare the digital pixel value from the analog to digital converter to a predetermined saturated value,
determine that the digital pixel value meets or exceeds the predetermined saturated value, and
replace the digital pixel value that with a predetermined brightest pixel value, wherein the predetermined brightest pixel value is independent of digital pixel values of imaging pixels in the image sensor.
4. The imaging system of claim 3 , wherein the predetermined value is less than said predetermined saturated value.
5. The imaging system of claim 3 , wherein the predetermined value corresponds to a predetermined brightest-possible pixel value.
6. An imaging system comprising:
an analog to digital converter for converting received analog pixel values of an image to corresponding digital pixel values, and
a digital block adapted to (1) receive the digital pixel values output by the analog to digital converter, (2) identify one or more received pixel values that are at or above the predetermined saturation value, and (3) output a predetermined maximum digital value for each of the one or more received pixel values that are at or above a predetermined saturation value, wherein the predetermined maximum digital value is independent of the digital pixel values.
7. A method of operating an imager, the method comprising:
obtaining analog pixel values from imaging pixels of an image sensor;
analog to digital converting the analog pixel values to obtain digital pixel values corresponding to the analog pixel values;
comparing the obtained digital pixel values to a predetermined saturated value;
identifying one or more obtained pixel values that meet or exceed the predetermined saturated value; and
replacing each of the one or more obtained digital pixel values that meet or exceed the predetermined saturated value with a different digital pixel value corresponding to a singular maximum value of the obtained digital pixel values that is less than the predetermined saturated value.