Multi-half-tone imaging and dual modulation projection/dual modulation laser projection
Smaller halftone tiles are implemented on a first modulator of a dual modulation projection system. This techniques uses multiple halftones per frame in the pre-modulator synchronized with a modified bit sequence in the primary modulator to effectively increase the number of levels provided by a given tile size in the halftone modulator. It addresses the issue of reduced contrast ratio at low light levels for small tile sizes and allows the use of smaller PSFs which reduce halo artifacts in the projected image and may be utilized in 3D projecting and viewing.
1. A method for dual-modulation display, comprising:
identifying a Point Spread Function (PSF) of a set of relay optics, the PSF encoding non-uniformities in light transmitted through the relay optics from a pre-modulator to a primary modulator;
generating a Fourier Transform of the PSF of the relay optics;
determining a desired PSF and a Fourier Transform of the desired PSF for the primary modulator;
calculating a correction factor as a function of the Fourier Transforms of both the desired PSF and the PSF of the relay optics;
generating an inverse Fourier Transform of the correction factor;
applying the inverse Fourier Transform of the correction factor to input image data to the pre-modulator.
2. The method of claim 1 , wherein the PSF of the relay optics is a two-dimensional (2D) PSF.
3. The method of claim 1 , further comprising:
energizing the pre-modulator with the input image data applied with the inverse Fourier Transform of the correction factor.
4. The method of claim 1 , wherein applying the inverse Fourier Transform of the correction factor further comprises applying the inverse Fourier Transform of the correction factor during multiple halftones per frame of the pre-modulator.
5. The method of claim 4 , wherein applying the inverse Fourier Transform of the correction factor during multiple halftones per frame of the pre-modulator is synchronized with a modified bit sequence in the primary modulator to produce a compensation image that reduces the non-uniformities of the PSF of the relay optics.
6. The method of claim 4 , wherein applying the inverse Fourier Transform of the correction factor during multiple halftones per frame of the pre-modulator further comprises applying the inverse Fourier Transform of the correction factor during a single frame period of a modulation period of the primary modulator and several sub-frame time periods of a modulation period of the pre-modulator.
7. The method of claim 6 , wherein pixel elements of the primary modulator are switched on/off once during the single frame period and pixel elements of the pre-modulator are switched on/off once during a single sub-frame period and further that the single frame period comprises a plurality of sub-frame time periods.