| 摘要 |
The invention provides an illuminator comprising a laser source and an Electrically Switchable Bragg Grating (ESBG) device disposed along the path of the beam emitted by said laser. The laser and ESBG form part of an apparatus for illuminating an electronic display to provide a viewable image. At least one viewable surface illuminated by laser light exhibits speckle. The ESBG device is configured to generate a time sequential set o f speckle cells by operating on one or both of the optical phase or ray-angular characteristics o incoming light. The optical characteristics of the ESBG are changed by applying a time varying electric field to the ESBG. A human eye observing the display integrates said speckle cells to provide an apparently de-speckled final image. The ESBG device may be characterised as a variable diffractive axicon, a variable sub-wavelength grating or a variable diffractive diffuser. The ESBG device may comprise similarly characterised first and second gratings disposed in series. The laser source and ESBG device may be two-dimensional arrays. |
