US 4,575,193 A · Optical spatial frequency filter

Abstract

An optical spatial frequency filter of the type having a pair of birefringent elements with means for changing the polarization state of light between them is given a substantially color dependent spatial frequency response. The filter comprises a wavelength dependent means for changing the polarization state of light between the birefringent elements such that the polarization state of light of a first color is changed by a first amount and the polarization state of light of a second color is changed by a second amount sufficiently different from the first amount such that the spatial frequency response of the spatial frequency filter is substantially color dependent. The filter is particularly useful with a color image sensor of the type having a first sampling frequency in a first color and a second sampling frequency different from the first in a second color. The filter is made to have a frequency response in the first and second colors in relation to the respective first and second sampling frequencies of the sensor. The filter has the advantage that, when used with the color image sensor, aliasing is selectively reduced in each color without reducing resolution in the other colors.

Claims10

Dependent claims

An optical spatial frequency filter comprising;

at least one pair of birefrigent elements for separating a ray of unpolarized white light into three or more spaced apart rays of light and means for changing the polarization state of light between the birefrigent elements, wherein the means for changing the polarization state of light changes the polarization state of light of a first color by a first amount, and changes the polarization state of light of a second color by a second amount different from the first amount such that light of said first color is split into a first subset of one or more of said rays, separated by a first distance in a given direction, and light of said second color is split into a second subset of two or more of said rays, separated by a second distance larger than said first distance in said given direction, whereby the spatial frequency response of the spatial frequency filter is color dependent and higher for said first color than for said second color.

Dependencies are inferred from the claim text.

Optical spatial frequency filter

Life of this patent

Optical spatial frequency filter

Life of this patent

Abstract

Claims10