Method for calculating circular symmetrical microlens/color filter array shift
View Patent ↗An image sensor formed with shifts among the optical parts of the sensor and the photosensitive parts of the sensor. Exemplary methods of calculating the desired shift are described and include a circular, symmetric design for the shift. The exemplary methods can also be used to calculate a correction coefficient for performing shading correction on signals that are output from the array and digitized.
1. A method of calculating microlens shift for groups of pixels, the method comprising the acts of:
for each group of pixels of a pixel array, calculating a microlens shift for each pixel contained in the group by:
calculating a radial distance that the pixel is away from a center of the pixel array, the pixel being associated with a microlens;
converting the radial distance to an image height percentage;
determining a chief ray angle based on the image height percentage; and
using the chief ray angle to determine the microlens shift for the microlens;
computing an average shift for each group of pixels by averaging the microlens shifts for the pixels contained in the group; and
using the average shift as the desired shift for the respective group of pixels.
2. The method of claim 1 , wherein the desired shift is in a direction from a center of the respective group of pixels toward the center of the pixel array.
3. The method of claim 1 , wherein the act of determining a chief ray angle comprises obtaining a chief ray angle curve for an imaging lens used in connection with the microlens.
4. The method of claim 1 , further comprising the acts of: determining a distance from the microlens to the underlying pixel in a substrate; determining a wavelength for incoming light; and determining optical properties for any dielectric layers that may be located between said microlens and said substrate.