Development of Novel Technology in Reducing Speckle Noise in Projectors and Displays using Laser Light Source by DNP
In spite of LED’s advantages over high pressure mercury lamp as a light source for displays, projectors as well as illumination, offering a longer life cycle and reduced power consumption, not to mention the possibility of downsizing the optical components, the laser light source are prone to generate speckle noise which appears as a fine mottled splashing causing scintillation. To overcome this issue, DNP has developed a new technology which is based on multi-recording and light-forming functions of holograms with an aim to reduce speckle noise that is the cause of scintillation. DNP has used volume hologram functions capable of reproducing the same image in the same position no matter which point on the hologram the light beam is projected upon.
The new technique projects the laser light source as a beam on various points of the hologram in a repeated manner with an optical scanning device, like scan-mirror, where the angle of incidence on the images reproduced on the screen constantly changes, generating numerous interference patterns. As a result of this, the interference patterns are averaged, whereby reducing the speckle noise. Furthermore, as the laser beam shaping and homogenizing of light intensity can be carried out with hologram, optical equipment such as diffuser and the lens array are no longer needed. The application of this new technology can be extended to sensors, such as 3D scanners as well as image devices.