Speckle-reduction in virtual and augmented reality systems and methods
An imaging system includes a diffusing element configured to couple portions of a light beam back into a laser diode. The system includes a diode laser driven into a chaotic regime by a combination of a diffuser and a modulated drive current such that it emits light across a frequency spectrum having an envelope between 3 and 10 nanometers wide. The system further includes a diffusing element at least 0.1 mm to 0.5 mm away from the diode laser to couple portions of the light beam back into the laser diode. Another embodiment is directed to using the diffusing element to illuminate a flat panel display or a spatial light modulator.
1. A system for reducing laser speckling, comprising:
a laser diode configured for generating a light beam having a wavelength within a visible spectrum;
a modulator configured for varying a current for driving the laser diode; and
a diffuser having a random or pseudo-random patterned surface configured for causing at least a portion of the light beam to reflect off the random or pseudo-random patterned surface and scatter back into the laser diode as reflected rays to generate a chaotic laser pattern, wherein the diffuser is further configured for causing a portion of the light beam to pass therethrough as transmitted rays.
2. The system of claim 1 , wherein the diffuser has a feature size in the range of 1 to 100 microns.
3. The system of claim 1 , further comprising a second diffuser disposed on an opposite side of the diffuser from the laser diode, wherein the second diffuser configured for receiving the transmitted rays of the portion of the light beam passing through the diffuser.
4. The system of claim 1 , further comprising a display screen configured for receiving the chaotic laser pattern and presenting an image derived from the chaotic laser pattern.
5. The system of claim 4 , further comprising a head-mounted frame configured for positioning the display screen in front of the eyes of a user of the display screen.
6. The system of claim 4 , wherein the display screen comprises an eyepiece waveguide in which the chaotic laser pattern is injected.
7. The system of claim 4 , further comprising an optical coupler subsystem configured for coupling the chaotic laser pattern to the display screen.
8. The system of claim 1 , further comprising a multimode fiber configured for enabling multiple light modes of the chaotic laser pattern to propagate at different reflection angles within the multimode fiber.
9. The system of claim 1 , further comprising a homogenizer for smoothing out irregularities chaotic laser pattern to create a uniform pattern.
10. The system of claim 1 , wherein the modulator is configured for varying the current for driving the laser diode, such that the chaotic laser pattern has a spectral width of 3 nm to 10 nm.
11. A system for reducing laser speckling, comprising:
a laser diode configured for generating a light beam having a wavelength within a visible spectrum;
a modulator configured for varying a current for driving the laser diode; and
a diffuser having a random or pseudo-random patterned surface configured for causing 2-4 percent of the light beam to reflect off the random or pseudo-random patterned surface and scatter back into the laser diode as reflected rays to generate a chaotic laser pattern.
12. A system for reducing laser speckling, comprising:
a laser diode configured for generating a light beam having a wavelength within a visible spectrum;
a modulator configured for varying a current for driving the laser diode; and
a diffuser having a random or pseudo-random patterned surface configured for causing at least a portion of the light beam to reflect off the random or pseudo-random patterned surface and scatter back into the laser diode as reflected rays to generate a chaotic laser pattern, wherein the diffuser is spaced 0.1 mm to 0.5 mm away from the laser diode.
13. A method for reducing laser speckling, comprising:
generating a laser beam having a wavelength within a visible spectrum;
amplitude modulating the laser beam
reflecting at least a portion of the modulated laser beam off of a random or pseudo-random patterned surface back into the modulated laser beam, thereby generating a chaotic laser pattern; and
transmitting at least a portion of the modulated laser beam through the random or pseudo-random patterned surface.
14. The method of claim 13 , wherein the random or pseudo-random patterned surface has a feature size in the range of 1 to 100 microns.
15. The method of claim 13 , further comprising displaying an image derived from the chaotic laser pattern.
16. The method of claim 13 , further comprising smoothing out irregularities chaotic laser pattern to create a uniform pattern.
17. The method of claim 13 , wherein the laser beam is amplitude modulated, such that the chaotic laser pattern has a spectral width of 3 nm to 10 nm.
18. A method for reducing laser speckling, comprising:
generating a laser beam having a wavelength within a visible spectrum;
amplitude modulating the laser beam; and
reflecting 2-4 percent of the light beam of the modulated laser beam off of a random or pseudo-random patterned surface back into the modulated laser beam, thereby generating a chaotic laser pattern.