In this paper, the relationship between the spatial coherence of light field and the speckle contrast in a laser based projection display system is studied under the consideration of human visual percept. By using a varifocal liquid-crystal lens and a monochromatic CCD, a system which is used for simulating the human eye is set up to record the speckle pattern. An efficient method for controlling the spatial coherence by using a dielectric elastomer actuator (DEA) is proposed. The results show that the total efficiency for energy utilization is more than 60% during our experiment. When the distance between the observer and the screen is large enough (<3 meters), the speckle contrast can be eliminated well at last (<4%) and the observer won’t feel the speckle phenomenon.
In this paper, the laser speckle pattern on human retina for a laser projection display is simulated. By introducing a
specific eye model ‘Indiana Eye’, the statistical properties of the laser speckle are numerical investigated. The results
show that the aberrations of human eye (mostly spherical and chromatic) will decrease the speckle contrast felt by
people. When the wavelength of the laser source is 550 nm (green), people will feel the strongest speck pattern and the
weakest when the wavelength is 450 nm (blue). Myopia and hyperopia will decrease the speckle contrast by introducing
large spherical aberrations. Although aberration is good for speckle reduction, but it will degrade the imaging capability
of the eye. The results show that laser source (650 nm) will have the best image quality on the retina. At last, we
compare the human eye with an aberration-free imaging system. Both the speckle contrast and the image quality appear
different behavior in these two imaging systems. The results are useful when a standardized measurement procedure for
speckle contrast needs to be built.
Image restoration for constructing high-spatial-resolution images in an imaging system which realizes indirectly far-filed
imaging by integrating the microlenses array with LCD is reported. We have investigated the indirectly far-field imaging
condition where adjacent sampling points contribute the detected signal. Experimental setup with microlens of 500 μm
diameter and 8 mm focal length is built to prove this condition by studying performance of image restoration using
modified point spread function (PSF). Since any one iterative method is not optimal for all image deblurring problems,
some deblurring algorithms including direct deconvolution and iterative deconvolution are applied to our imaging system
and we compared the effectiveness of these iterative procedures to choose right one for our use.