Speckle suppression in projection displays by using a motionless changing diffuser

Abstract

Speckle suppression in projection displays with the laser light source can be achieved by imaging a changing diffuser with random phase cells onto the screen. Theoretical expressions for the speckle contrast in this method have been earlier obtained in the case when different realizations of the phase diffuser produce statistically independent patterns of the light field on the screen [J. W. Goodman]. In the present paper, these expressions are generalized in the case when different realizations of the phase diffuser produce partly correlated speckle patterns. Both cases when the diffuser just fills or overfills the projection optics are considered. Possible structure of a motionless changing diffuser is presented. It includes the dynamic diffractive optical element (DDOE) and a light homogenizer. The DDOE can be based on the electrically controlled spatial light modulator with a deformable polymer layer (SLMDPL). The SLMDPL can handle high light power and therefore, can be used in projection displays with powerful laser beams.

Speckle Suppression by Integrated Sum of Fully Developed Negatively Correlated Patterns in Coherent Imaging

“…Using DOEs in laser scanning displays, the scanning spot was split into several randomly-spread small spots [6], or modulated with phase arrays [7][8][9][10]. In systems projecting full-frame images, the DOE functioned as a changing diffuser to generate partially coherent illumination [11][12][13][14]. In holographic projection displays, a phase-only DOE encoding a target image was displayed in an LCoS spatial light modulator (SLM), and the Fourier transform of the DOE, showing the target image, was projected onto the screen [15][16][17][18].…”