Nonlinear effects of phase blurring on Fourier transform holograms

Abstract

Liquid-crystal light valves can have intensity-dependent resolution. We find for a nematic liquid-crystal light valve that this effect is well modeled as a phase that has been blurred by a linear space-invariant filter. The phase point-spread function is measured and is used in simulations to demonstrate that it introduces intermodulation products to the diffraction patterns of computer-generated Fourier transform holograms. Also, the influence of phase blurring on a pseudorandom-encoding algorithm is evaluated in closed form. This analysis applied to a spot array generator design indicates that nonlinear effects are negligible only if the diameter of the point-spread function is a small fraction of the pixel spacing.

Suppression of the zero-order diffracted beam from a pixelated spatial light modulator by phase compression

“…In addition, it has been studied in multiwavelength holographic image projection where the hologram designed for one wavelength appears as a scaled phase for the other wavelengths [17]. Phase scaling error produces extra noise in the reconstructed image and reduces the diffraction efficiency by introducing an on-axis component (i.e., extra ZOD beam) [18]. The phase scaling effect is detrimental in these examples.…”

Fundamental properties of spatial light modulators for the approximate optical computation of Fourier transforms: a review

“…However, phase-only light valves have limited phase resolution, which leads to frequency dependent diffraction efficiency. A useful model for this effect is to convolve the desired phase modulation with a phase point spread function 33 of the SLM. The desired modulation is a 2modded linear phase ramp ͑as was used in the model of the pixelated SLM͒ that is then convolved with a point spread function to produce the blurred phase.…”

“…14, 33, and 34 leads me to believe that the effects of blurring on discretely addressed SLMs are quite a bit more severe than this idealized estimate. For real-world SLMs, I suspect that the diffraction efficiency is more severely affected both by both blurring ͑due to a nonabrupt, e.g., Gaussian-shaped, blur 33 ͒ and pixelation ͑due to less than 100% fill factors and blurring in the write-side monitor͒. Despite the idealized nature of the models presented in this section, these simple results do provide useful information on the selection of SLM characteristics to achieve good utilization of optical power and SBWP.…”