High brightness projection systems and methods
A hybrid projector architecture combines steered light with unsteered light. In some embodiments the steered light is narrowband light and the unsteered light is broadband light. Splitting between the steered and unsteered light may be determined based on luminance level. For example, the unsteered light may contribute a large proportion of the light for luminance levels up to a threshold. The steered light may contribute an increasing proportion of the light as luminance values rise above the threshold.
1. An image projection system comprising:
a first projector operative to project first modulated light onto a screen, the first projector comprising a first spatial light modulator;
a second projector operative to project second modulated light onto the screen superposed with the first modulated light, the second projector comprising a light steering module;
a controller operative to process image data comprising pixel values defining target illumination levels for a target image to be displayed and to generate control signals for the first spatial light modulator and the light steering module, wherein the processing comprises splitting light output between the first and second projectors in such a manner that the second modulated light includes a portion of the light for each of the pixels of the image and the first modulated light makes up a majority of the light for those pixels of the image for which the target illumination level is less than a first threshold level,
wherein the processing of the image data further includes splitting the target image into a light steering image portion for illumination by the second modulated light and a light non-steering image portion for illumination by the first modulated light, wherein the splitting of the target image is based on a function or look-up table.
2. The image projection system according to claim 1 wherein the controller is configured to generate a modified target image by processing comprising raising the pixel values defining the target image to the power γ where γ>1 and to base the control signals for the second projector on the modified target image.
3. The image projection system according to claim 1 wherein the controller is configured to perform the splitting on a pixel-by-pixel basis based on the target illumination levels.
4. The image projection system according to claim 2 wherein the controller is configured to maintain a fixed ratio of luminance of the second modulated light to luminance of the first modulated light for pixels having target illumination levels below the first threshold level.
5. The image projection system according to claim 4 wherein the controller is configured to control the second projector so that the ratio of the second modulated light to the first modulated light exceeds the fixed ratio for pixels having target illumination levels exceeding the first threshold.
6. The image projection system according to claim 5 , wherein the fixed ratio is less than 20%.
7. The image projection system according to claim 1 wherein a maximum achievable illumination level by the second projector for any pixel of the second modulated light is at least 10 times greater than a maximum achievable illumination level by the first projector for any pixel of the first modulated light.
8. The image projection system according to claim 1 wherein the controller comprises the lookup table (LUT) and the controller is configured to split the light output between the first and second light projectors based on outputs from the LUT.
9. The image projection system according to claim 1 wherein the second projector comprises a second spatial light modulator, the controller is configured to apply an alignment warping to the image data to yield warped image data and to drive the second spatial light modulator using the warped image data.
10. The image projection system according to claim 1 wherein the controller is configured to perform a check to determine whether display of the target image is feasible and, if the check determines that display of the target image is not feasible the controller is configured to perform tone mapping on the image data to yield tone mapped image data and to continue the processing with the tone mapped image data.
11. The image projection system according to claim 1 wherein the first projector comprises a broadband light source.
12. The image projection system according to claim 11 wherein the broadband light source is arranged to illuminate the first spatial light modulator uniformly.
13. The image projection system according to claim 11 wherein the broadband light source comprises a source of white light.
14. The image projection system according to claim 1 wherein the second projector comprises a narrowband light source.
15. The image projection system according to claim 14 wherein the narrowband light source comprises one or more laser diodes.
16. The image projection system according to claim 15 wherein the narrowband light source comprises red-light-emitting, green-light-emitting and blue-light-emitting laser diodes.
17. The image projection system according to claim 16 wherein the light steering module comprises a plurality of phase modulators and light emitted by the red-light-emitting, green-light-emitting and blue-light-emitting laser diodes is respectively steered by first, second and third ones of the plurality of phase modulators.
18. The image projection system according to claim 16 wherein the controller implements a forward model that computes a predicted light field for light that has been steered by the light steering module, the forward model comprising separate point spread functions for light emitted by the red-light-emitting, green-light-emitting and blue-light-emitting laser diodes.
19. The image projection system according to claim 18 wherein the forward model is an iterative model.
20. The image projection system according to claim 18 wherein the forward model models a steered component of light from the light steering module and an unsteered component of the light from the light steering module.