Compound Speckle Characterization Method and Reduction by Optical Design

Abstract

Speckle and the compound speckle can be reduced by angle diversity. In laser projection displays, simple, low cost and efficient speckle reduction techniques require smart optical design. Using a MEMS scanner together with a condenser lens, laser beams with different illumination angles are obtained on the diffuser surface with low speckle contrast ratio (CR). After homogenizing within a rod integrator, the speckle field illuminates a display panel, and is projected onto the screen which forms the compound speckle. Characterization method to evaluate the compound speckle reduction efficiency is analyzed and discussed in a simplified optical system. The preliminary speckle reduction is demonstrated in a commercial projector where a 600 mW green laser has been used as the illumination source, and the compound speckle CR is brought down from 0.38 to 0.14.

Full speckle suppression in laser projectors using two Barker code-type diffractive optical elements

“…Therefore, when one period of the DOE is larger than D∕2 D 0 , only one maximum of the correlation function is inside a central peak of the Q function, and with good accuracy, only one term with an index i 0 can be left in the sums (24), (25) for the calculation of C 2…”

“…The Barker code-type DOE is used to generate a wide spatial-frequency band and to increase the beamwidth to a diameter of the input numerical aperture of the objective lens independent of the initial width of the laser beam. In [24,25], a generalization of this method was proposed. However, in the method, only an aperture along the beamscanning direction can be used for speckle suppression.…”

Speckle reduction using phase plate array and lens array

“…Speckle is a drawback of laser display for it can downgrade the image quality greatly. To solve this problem, numerous methods have been proposed, such as: using a deformable mirror 3 or a scanning mirror 4,5 to realize angle diversity; using a broad-area vertical-cavity surface-emitting laser 6 or random lasers 7 to realize wavelength diversity; using a staircase element 8 or a refractive steppers 9 to realize optical path difference; rotating independent speckle patterns 10 or a magneto-optical disk 11 to realize polarization diversity; using a light pipe 12 or a multimode optical fiber bundle 13 to realize time averaging and so on. J. I. Trisnadi firstly proposed the speckle reduction method using Hadamard phase diffuser 14,15 .…”

P-177: Principle and Design of a Binary Phase Modulator Based on the Electro-Optic Effect for Speckle Reduction in Laser Displays

“…Speckle reduction techniques should be introduced to improve the image quality in laser displays [1][2][3]. In our previous publication [4], a speckle reduction method by a twodimensional (2D) binary phase diffuser (BPD) generated from orthogonal arrays (OAs) was reported.…”