Optical system and method

• US 8,783,878 B2
• Filed: 12/18/2008
• Issued: 07/22/2014
• Est. Priority Date: 12/19/2007
• Status: Expired due to Fees

• Current Assignee: Optyka Limited
• Original Assignee: Optyka Limited
• Inventors: Shevlin, Fergal Patrick, Sqalli, Omar, Descharmes, Nicolas
• Primary Examiner(s): CHOWDHURY, SULTAN U.
• Application Number:
  US12/808,735
• Publication Number:
  US 20110102748A1
• Time in Patent Office: 2,042 Days
• Field of Search: 353/30, 353/31, 353/34, 353/38, 353/70, 353/84, 353/85, 353/94, 353/98, 353/99, 353/122, 359/10, 359/24, 359/33, 359/223.1, 359/298, 359/634, 359/707, 372/21, 372/99, 372/9, 372 12- 16, 372/101, 372/108, 349/5, 349 7- 9
• US Class Current: 353/98
• CPC Class Codes: G02B 26/0825 the reflecting element being a flexible sheet or membrane, e.g. for varying the focus flexible mirrors for cosmetic use A45D42/24
• 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: G02B 26/0858 the reflecting means being moved or deformed by piezoelectric means
• CPC Class Codes: G02B 27/0938 Using specific optical elements
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G02B 5/02 Diffusing elements; Afocal elements
• CPC Class Codes: H04N 9/3111 for displaying the colours sequentially, e.g. by using sequentially activated light sources sequential projection in colour photography G03B33/08
• 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 (100) comprises a coherent light source (101) and optical elements for directing light from the source to a target (1001). The optical elements include at least one diffusing element (141, 161) arranged to reduce a coherence volume of light from the source and a variable optical property element (151). A control system (1021) controls the variable optical property element such that different speckle patterns are formed over time at the target (1001) with a temporal frequency greater than a temporal resolution of an illumination sensor or an eye (1011) of an observer so that speckle contrast ratio in the observed illumination is reduced. The variable optical property element (151) may be a deformable mirror with a vibrating thin plate or film.

Claims

1. An optical system comprising:

a coherent light source;

a target;

optical elements for directing light from the source to the target, said optical elements including at least one diffusing element arranged to reduce a coherence volume of light from the source and a deformable mirror system arranged to change optical paths of the light over time; and

a control system arranged to control the deformable mirror system to form different speckle patterns over time at the target with a temporal frequency greater than a predetermined temporal resolution of an illumination sensor or an eye of an observer to reduce speckle contrast ratio in the observed illumination.

2. An optical system as claimed in claim 1, wherein the deformable mirror system is located between two diffusing elements.

3. An optical system as claimed in claim 1, wherein the deformable mirror system is modulated pneumatically or by an air flow.

4. An optical system as claimed in claim 1, wherein the deformable mirror system is modulated by electrostatic, piezoelectric, electromagnetic, acoustic, hydraulic, and/or mechanical actuation.

5. An optical system as claimed in claim 1, wherein the coherent light source comprises a plurality of coherent and non-coherent light sources.

6. An optical system as claimed in claim 1, wherein the target is an image forming device.

7. An optical system as claimed in claim 6, wherein a projection optical system is arranged to magnify and relays an image from the image forming device to another position.

8. An optical system as claimed in claim 1, comprising a light beam homogeniser.

9. An optical system as claimed in claim 8, wherein the light beam homogeniser is a fly'"'"'s eye lens, a tunnel integrator or a diffuser.

10. An optical system comprising:

a coherent light source;

a target;

optical elements for directing light from the source to the target, said optical elements including at least one diffusing element arranged to reduce a coherence volume of light from the source; and

a deformable mirror system arranged to change optical paths of the light over time, wherein the deformable mirror system comprises;

a deformable thin plate or film coated to reflect predetermined wavelengths of light;

actuator means arranged to impart motion to the thin plate or film such that its surface shape is continuously deformed elastically; and

a control system arranged to control the actuator to cause a sequence of motions and surface shape deformations of the thin plate or film to change a speckle pattern formed from coherent light from the coherent light source and reflected from the thin plate or film at the target over a period of time less than the predetermined temporal resolution of an illumination sensor to reduce speckle contrast ratio in the observed illumination.

11. A optical system as claimed in claim 10, wherein the control system effects surface shape deformations at a resonant frequency.

12. A optical system as claimed in claim 10, wherein the control system effects surface shape deformations at a fixed frequency.

13. An optical as claimed in claim 10, wherein the control system effects surface shape deformations at a variety of frequencies.

14. An optical system as claimed in claim 10, comprising sensing means to observe behavior of the deformable thin plate or film.

15. An optical system as claimed in claim 14, wherein the control system is arranged to use observations of the sensing means to operate in closed-loop manner to maintain desired behavior of the deformable thin plate or film.

16. An optical system as claimed in claim 14, wherein the sensing means comprises a photosensitive element.

17. An optical system as claimed in claim 10, wherein the sensing means comprises a plurality of sensors.

18. An optical system as claimed in claim 10, wherein the actuator means comprises one of a piezoelectric actuator and a pneumatic actuator.

19. An optical system as claimed in claim 10, wherein the motion is imparted to the thin plate or film one of by a mounting frame moved by the actuator means and by an air flow.

20. An optical system as claimed in claim 10, wherein the actuator means comprises a plurality of actuators.

21. An optical system as claimed in claim 14, wherein the sensing means comprises one of a piezoelectric, acoustic, electromagnetic, capacitive, current or voltage sensor.

22. An optical system comprising:

a coherent light source;

optical elements for directing light from the source to a target, said optical elements including at least one diffusing element arranged to reduce a coherence volume of light from the source and a deformable mirror system; and

a control system arranged to control the deformable mirror system to form different speckle patterns over time at the target with a temporal frequency greater than a temporal resolution of an illumination sensor or an eye of an observer to reduce speckle contrast ratio in the observed illumination,

wherein the deformable mirror system comprises;

a thin plate or film coated to reflect predetermined wavelengths of light; and

actuator means arranged to impart motion to the thin plate or film such that its surface shape is continuously deformed elastically.