# US 8,783,878 B2 · Optical system and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,783,878 B2 - Document ID: US8783878B2 - Status: Granted - Kind: B2 - Application number: 12/808,735 - Filed: 2008-12-18 - Published: 2011-05-05 - Granted: 2014-07-22 - Earliest claimed: 2007-12-19 - Assignees: Optyka Limited - Applicants: Fergal Patrick Shevlin; Omar Sqalli; Nicolas Descharmes - Inventors: Fergal Patrick Shevlin; Omar Sqalli; Nicolas Descharmes - Web page: https://patentgrep.com/patent/US8783878B2 ## CPC - G02B 27/48: Laser speckle optics - 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)} - G02B 26/0858: {the reflecting means being moved or deformed by piezoelectric means} - H04N 9/3111: {for displaying the colours sequentially, e.g. by using sequentially activated light sources (sequential projection in colour photography G03B33/08)} - H04N 9/3161: {using laser light sources (using laser beams scanning the display screen H04N9/3129)} - H04N 9/3164: {using multiple light sources} - G02B 5/02: Diffusing elements; Afocal elements - 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)} - G02B 27/0938: {Using specific optical elements} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## 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 ### Claim 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. ### Claim 2 (depends on 1) An optical system as claimed in claim 1, wherein the deformable mirror system is located between two diffusing elements. ### Claim 3 (depends on 1) An optical system as claimed in claim 1, wherein the deformable mirror system is modulated pneumatically or by an air flow. ### Claim 4 (depends on 1) 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. ### Claim 5 (depends on 1) An optical system as claimed in claim 1, wherein the coherent light source comprises a plurality of coherent and non-coherent light sources. ### Claim 6 (depends on 1) An optical system as claimed in claim 1, wherein the target is an image forming device. ### Claim 7 (depends on 6) 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. ### Claim 8 (depends on 1) An optical system as claimed in claim 1, comprising a light beam homogeniser. ### Claim 9 (depends on 8) 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. ### Claim 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. ### Claim 11 (depends on 10) A optical system as claimed in claim 10, wherein the control system effects surface shape deformations at a resonant frequency. ### Claim 12 (depends on 10) A optical system as claimed in claim 10, wherein the control system effects surface shape deformations at a fixed frequency. ### Claim 13 (depends on 10) An optical as claimed in claim 10, wherein the control system effects surface shape deformations at a variety of frequencies. ### Claim 14 (depends on 10) An optical system as claimed in claim 10, comprising sensing means to observe behavior of the deformable thin plate or film. ### Claim 15 (depends on 14) 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. ### Claim 16 (depends on 14) An optical system as claimed in claim 14, wherein the sensing means comprises a photosensitive element. ### Claim 17 (depends on 10) An optical system as claimed in claim 10, wherein the sensing means comprises a plurality of sensors. ### Claim 18 (depends on 10) An optical system as claimed in claim 10, wherein the actuator means comprises one of a piezoelectric actuator and a pneumatic actuator. ### Claim 19 (depends on 10) 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. ### Claim 20 (depends on 10) An optical system as claimed in claim 10, wherein the actuator means comprises a plurality of actuators. ### Claim 21 (depends on 14) An optical system as claimed in claim 14, wherein the sensing means comprises one of a piezoelectric, acoustic, electromagnetic, capacitive, current or voltage sensor. ### Claim 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.