Projector optimized for modulator diffraction effects

• US 9,915,820 B2
• Filed: 03/15/2013
• Issued: 03/13/2018
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: IMAX Corporation
• Original Assignee: IMAX Theatres International Limited (IMAX Corporation)
• Inventors: Kurtz, Andrew F., Nothhard, Gary E.
• Primary Examiner(s): Thomas, Brandi
• Application Number:
  US14/776,350
• Publication Number:
  US 20160033757A1
• Time in Patent Office: 1,824 Days
• Field of Search: None
• CPC Class Codes: A45C 13/00 Details; Accessories
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G03B 21/008 using micromirror devices
• CPC Class Codes: G03B 21/2033 LED or laser light sources
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/3161 using laser light sources using laser beams scanning the display screen H04N9/3129
• CPC Class Codes: H04N 9/3164 using multiple light sources

Abstract

An optical system that includes a micro-mirror array optical modulator that can selectively modulate an incident light beam having a defined narrow spectral bandwidth to encode data thereon based on commands to an ON-state or an OFF-state of a micro-mirror. The micro-mirror array optical modulator can redirect light by diffraction and reflection to provide an output modulated light beam that exhibits a diffraction handedness dependent described by an arrangement of diffraction orders that depend in part on the narrow spectral bandwidth of light incident thereupon. An optical element has an optimized limiting aperture for defining portions of a modulated light beam that are blocked and remaining portions that are transmitted. An ON-state efficiency and an OFF-state contrast of an optically transmitted modulated light beam can depend on the diffraction handedness of the output modulated light beam relative to a size and a shape of the optimized limiting aperture.

Claims

1. An optical system for modulating an incident light beam, the optical system comprising:

an illumination source for providing the incident light beam having a defined narrow spectral bandwidth that is 10 nm or less;

an optical element having an aperture of a size and a shape for transmitting portions of a modulated light beam and blocking remaining portions of the modulated light beam; and

a micro-mirror array optical modulator for selectively modulating the incident light beam to encode data thereon based on commands to an ON-state or an OFF-state of one or more micro-mirrors to form the modulated light beam, the micro-mirror array optical modulator being selected from a plurality of micro-mirror array optical modulators by being matched to the size and shape of the aperture in that the modulated light beam has an ON-state light efficiency and an OFF-state contrast that depend on a diffraction handedness pattern of the modulated light beam relative to the size and the shape of the aperture, wherein the optical system is configured to have an f-number in a range of F/3.5 to F/6.

2. The optical system of claim 1, wherein a micro-mirror in the micro-mirror array optical modulator is smaller than 20 wavelengths of the incident light beam.

3. The optical system of claim 1, wherein the micro-mirror array optical modulator is configured for outputting the modulated light beam with the diffraction handedness pattern that is defined by a relative arrangement of at least a primary order of diffraction and dominant secondary orders of the ON-state relative to an unpowered state.

4. The optical system of claim 1, wherein the diffraction handedness pattern is based on a tilt of a micro-mirror of the micro-mirror array optical modulator.

5. The optical system of claim 1, wherein the diffraction handedness pattern is a left-handed pattern, a right-handed pattern, or an intermediate pattern.

6. The optical system of claim 1, wherein the micro-mirror array optical modulator is testable to determine a characteristic diffraction handedness pattern for one or more spectral bandwidths.

7. The optical system of claim 6, wherein the micro-mirror array optical modulator is configured to be tested using incident light having a selected spectral bandwidth directed at the micro-mirror array optical modulator and characterizing an arrangement of diffraction orders relative to an unpowered state zero order.

8. The optical system of claim 1, wherein the illumination source includes a first illumination source and a second illumination source that are configured to provide visible light and to have a narrow spectra bandwidth that is less than or equal to 7 nm.

9. The optical system of claim 1, wherein the size of the aperture is based on system light efficiency, contrast, image quality, modulation transfer function, or efficiency variability across the micro-mirror array optical modulator.

10. The optical system of claim 9, wherein the shape and the size of light blocking portions of the aperture are configured to block light at edges of a primary diffraction order and at least one adjacent secondary diffraction order.

11. The optical system of claim 1, wherein the micro-mirror array optical modulator is a digital micro-mirror device.

12. The optical system of claim 1, wherein the optical system is an optical projection system for providing images to a display surface.

13. The optical system of claim 1, wherein the optical element is a projection lens.

14. The optical system of claim 1, further comprising a second illumination source for providing a second incident light beam having a second defined spectral bandwidth to a second micro-mirror array optical modulator that is selected based on a desired performance of light efficiency and contrast of the second modulated light beam from the second micro-mirror array optical modulator depending on the size and shape of the aperture.

15. The optical system of claim 14, wherein the narrow spectral bandwidth and the second spectral bandwidth are non-overlapping.

16. The optical system of claim 14, wherein the aperture of the optical element is configured to transmit a different effective f-number for the narrow spectral bandwidth than for the second spectral bandwidth.

17. An optical system for modulating an incident light beam, the optical system comprising:

an illumination source for providing the incident light beam having a defined narrow spectral bandwidth that is 10 nm or less;

a micro-mirror array optical modulator for selectively modulating the incident light beam to encode data thereon based on commands to an ON-state or an OFF-state of one or more micro-mirrors to form the modulated light beam; and

an optical element having an aperture of a size and a shape for transmitting portions of a modulated light beam and blocking remaining portions of the modulated light beam, the size and the shape of the aperture being matched to the micro-mirror optical modulator in that the modulated light beam has an ON-state light efficiency and an OFF-state contrast that depend on a diffraction handedness pattern of the modulated light beam relative to the size and the shape of the aperture, wherein the optical system is configured to have an f-number in a range of F/3.5 to F/6.

18. The optical system of claim 17, wherein a micro-mirror in the micro-mirror array optical modulator is smaller than 20 wavelengths of the incident light beam.

19. The optical system of claim 17, wherein the micro-mirror array optical modulator is configured for outputting the modulated light beam with the diffraction handedness pattern that is defined by a relative arrangement of at least a primary order of diffraction and dominant secondary orders of the ON-state relative to an unpowered state.

20. The optical system of claim 17, wherein the diffraction handedness pattern is based on a tilt of a micro-mirror of the micro-mirror array optical modulator.

21. The optical system of claim 17, wherein the illumination source includes a first illumination source and a second illumination source that are configured to provide visible light and to have a narrow spectra bandwidth that is less than or equal to 7 nm.

22. The optical system of claim 17, wherein the shape and the size of light blocking portions of the aperture are configured to block light at edges of a primary diffraction order and at least one adjacent secondary diffraction order.