Laser Projection System with Potassium Gadolinium Tungstate
An apparatus and method for enhancing light using stimulated Raman scattering in a potassium gadolinium tungstate (KGW) crystal. The stimulated Raman scattering is utilized to add wavelength diversity for reduced speckle and to change the color of the light to a more desirable combination of wavelengths. Digital projection is one application that may benefit from lower speckle and shifted color. Color-based stereoscopic projection is enabled by the addition of stimulated Raman bands at specific wavelengths.
1 . An optical apparatus comprising:
a potassium gadolinium tungstate (KGW) crystal;
a green laser; and
a digital projector;
wherein the green laser illuminates the KGW crystal; a stimulated Raman scattering in the KGW crystal enhances an aspect of a light output from the KGW crystal; and the light output of the KGW crystal illuminates the digital projector.
2 . The apparatus of claim 1 wherein the aspect of the light output from the KGW crystal is a speckle characteristic of the light output from the KGW crystal.
3 . The apparatus of claim 1 wherein the light output from the KGW crystal comprises a band of green light and a band of red light.
4 . The apparatus of claim 1 wherein the aspect of the light output from the KGW crystal is a color of the light output from the KGW crystal.
5 . The apparatus of claim 1 further comprising:
a multipass cell;
wherein the green laser illuminates the KGW crystal with a plurality of passes that are determined by the multipass cell.
6 . The apparatus of claim 1 further comprising:
a KGW resonant cavity;
wherein a resonant optical condition for the KGW crystal is determined by the KGW resonant cavity.
7 . The apparatus of claim 1 wherein the green laser has a green laser resonant cavity and the KGW crystal is located inside the green laser resonant cavity.
8 . The apparatus of claim 1 wherein a light output from the digital projector meets Digital Cinema Initiative color requirements.
9 . The apparatus of claim 8 wherein the light output of the KGW crystal is separated into a first wavelength band and a second wavelength band; and the first wavelength band is used to form a first-eye image of a stereoscopic image projected from the digital projector; and the second wavelength band is used to form a second-eye image of the stereoscopic image.
10 . The apparatus of claim 1 wherein the green laser comprises a fiber laser.
11 . A method of despeckling comprising:
generating a green laser beam from a green laser;
focusing the laser beam into a potassium gadolinium tungstate (KGW) crystal;
generating stimulated Raman scattering light in the KGW crystal;
using the stimulated Raman scattering light to enhance an aspect of a light output from the KGW crystal; and
using the light output of the KGW crystal to illuminate a digital projector.
12 . The method of claim 11 wherein the aspect of the light output from the KGW crystal is a speckle characteristic of the light output from the KGW crystal.
13 . The method of claim 11 wherein the light output from the KGW crystal comprises a band of green light and a band of red light.
14 . The method of claim 11 wherein the aspect of the light output from the KGW crystal is a color of the light output from the KGW crystal.
15 . The method of claim 11 wherein the green laser beam illuminates the KGW crystal with a plurality of passes that are determined by a multipass cell.
16 . The method of claim 11 wherein the green laser beam illuminates the KGW crystal with a resonant optical condition that is determined by a KGW resonant cavity.
17 . The method of claim 11 wherein the green laser has a green laser resonant cavity and the KGW crystal is located inside the green laser resonant cavity.
18 . The method of claim 11 wherein a light output from the digital projector meets Digital Cinema Initiative color requirements.
19 . The method of claim 11 further comprising:
separating the light output of the KGW crystal into a first wavelength band and a second wavelength band;
using the first wavelength band to form a first-eye image of a stereoscopic image in the digital projector; and
projecting the stereoscopic image from the digital projector.
20 . The method of claim 11 wherein the green laser comprises a fiber laser.