Digital point spread function (DPSF) and dual modulation projection (including lasers) using DPSF
A digital PSF for use in a dual modulation display. The invention allows the use of less than optimal point spread (PSF) functions in the optics between the pre-modulator and primary modulator of a dual modulation projection system. This technique uses multiple halftones per frame in the pre-modulator synchronized with a modified bit sequence in the primary modulator to produce a compensation image that reduces the errors produced by the sub-optimal PSF. The invention includes the application to dual modulation and dual modulated 3D viewing systems.
1. A projector comprising:
a pre-modulator configured to modulate light into a first image;
a primary modulator configured to further modulate the light to produce a desired image;
one or more relay optics configured to transfer the modulated light of the first image to the primary modulator, wherein the transfer optics are further configured to spread pixels of the first image so that each pixel of the first image illuminates a plurality of pixels of the primary modulator; and
a controller configured to energize the pre-modulator with a backlight image based on image data of the desired image, the backlight image further comprising an adjustment of pixels of the backlight image to compensate for imperfections of the relay optics;
wherein the compensation comprises a difference between a desired point spread function (PSF) of light transferred from the pre-modulator to the primary modulator and a PSF of the relay optics.
2. The projector according to claim 1 , wherein the backlight image comprises a convolution of a low-resolution version of the desired image and the difference.
3. The projector according to claim 1 , wherein the compensation comprises a compensation scheme selected from a plurality of compensation schemes based on the desired image.
4. The projector according to claim 1 , wherein the compensation comprises a non-linear equation application adjusted based on the desired image.
5. The projector according to claim 1 , wherein the compensation comprises a compensation scheme selected or derived based on a spatial frequency parameter of the image and a wavelength of light being modulated.
6. The projector according to claim 1 , wherein the compensation comprises a plurality of compensation schemes applied to different portions of the backlight image.
7. The projector according to claim 1 , wherein the projector comprises a multi-color channel projector each channel comprising a similar configuration of a pre-modulator, primary modulator, and relay optics, and said controller energizing each pre-modulator with image data comprising a backlight image of each color channel along with a color specific compensation.
8. The projector according to claim 7 , wherein the compensation comprises an inverse of a non-uniformity of spreading of pixels of the pre-modulator onto multiple pixels of the primary modulator according to wavelengths of light modulated in each channel.
9. The projector according to claim 6 , wherein the pre-modulator comprises one of a transmissive modulator and a reflective modulator, and the primary modulator comprises one of a transmissive modulator and a reflective modulator.
10. The projector according to claim 1 , wherein the pre-modulator and primary modulators are digital micromirror device (DMD) modulators or liquid crystal on silicon (LCoS) modulators.
11. The projector according to claim 1 , wherein the pre-modulator is energized by compensated pre-modulator images comprising left and right images of a 3D image, and wherein the projector is part of a system for displaying an viewing 3D images comprising glasses comprising filters corresponding to the left and right images comprising filter passbands encompassing wavelengths of the left and right images.
12. The projector according to claim 11 , wherein wavelengths of the left image originate from a laser light source illuminating a pre-modulator while being energized with a compensated pre-modulator left image corresponding the illuminating wavelengths in a left image time frame; wavelengths of the right image originate from a laser light source illuminating the pre-modulator while being energized with a compensated pre-modulator right image corresponding to the illuminating wavelengths in a right image time frame.
13. The projector according to claim 12 , wherein the projector is part of a system for displaying and viewing 3D images and the modulated desired images are passed via wavelength selective filters in 3D viewing glasses such that modulated wavelengths of the left images of the 3D images are passed by a left filter of the 3D viewing glasses and modulated wavelengths of the right images of the 3D images are passed by a right filter of the 3D viewing glasses and the filters comprise passbands that are offset relative to the wavelengths being viewed through the passbands such that wavelengths of compensated half-tone images further modulated into desired left and right images by the primary modulator are passed via passbands that encompass and are shifted toward longer wavelengths compared to the wavelengths of the intended image wavelengths passed through the passbands.