Characteristics Of Spatial Light Modulators Research Articles

Analysis of reconstruction quality for computer-generated holograms using a model free of circular-convolution error.

Continuous complex-amplitude computer-generated holograms (CGHs) are converted to discrete amplitude-only or phase-only ones in practical applications to cater for the characteristics of spatial light modulators (SLMs). To describe the influence of the discretization correctly, a refined model that eliminates the circular-convolution error is proposed to emulate the propagation of the wavefront during the formation and reconstruction of a CGH. The effects of several significant factors, including quantized amplitude and phase, zero-padding rate, random phase, resolution, reconstruction distance, wavelength, pixel pitch, phase modulation deviation and pixel-to-pixel interaction, are discussed. Based on evaluations, the optimal quantization for both available and future SLM devices is suggested.

Rapid detection of highly reflective surface defects based on digital micromirror device

The typical defect detection method is based on the use of conventional cameras with limited dynamic range and image processing algorithm. Their identification efficiency is low particularly for industrial application because the light intensity from some highly reflective surfaces can easily exceed the maximum intensity limit of the sensor. In this paper, we take advantage of the fast spatial light modulation characteristics of the DMD system. By generating highlight defect datasets and training the neural network (i.e., mask region-based convolutional neural network), the defects covered by strong light can be detected quickly and automatically.

Low power spatial light modulator with pharaonis phoborhodopsin

Spatial light modulation (SLM) has been theoretically analysed in pharaonis phoborhodopsin ( ppR) and its mutants based on nonlinear intensity induced excited-state absorption, to achieve large percentage modulation at low power. Amplitude modulation of probe laser read beam ( I p′) transmissions at 560, 512 and 390 nm, corresponding to the peak absorption of ppR O, ppR KL and ppR M intermediate states, respectively, of ppR photocycle, by write beam intensity ( I m′) at 498 nm, corresponding to the peak absorption of the initial ppR state, have been analysed using the rate equation approach, considering all six intermediate states in its photocycle. The SLM characteristics are shown to be sensitive to the normalized small signal absorption coefficient ( β) and the rate constants of intermediates. For a given I m′ range, there is an optimum value of β ( β opt) for maximum percentage modulation. We can achieve 100% modulation of the read beam if the initial ppR state does not absorb the respective probe beams. The SLM characteristics of F86D ppR have also been used to design an all-optical XOR logic gate. High dynamic range and sensitivity can be achieved at low write beam intensities in ppR compared to wild-type bacteriorhodopsin (WT-bR).

Spatial light modulation with pharaonis phoborhodopsin

A detailed and accurate analysis is presented of the low power spatial light modulation (SLM) characteristics of pharaonis phoborhodopsin (ppR) based on nonlinear intensity induced excited-state absorption. Amplitude modulation of probe laser read beam transmissions at 390 and 488 nm, corresponding to the peak absorption of ppRM and ppRL states of the ppR photocycle by write beam intensity-induced population changes at 498 nm, corresponding to the peak absorption of the initial ppR state, have been analysed using the rate equation approach. The SLM characteristics are shown to be sensitive to the normalised small signal absorption coefficient (β), the rate constants of intermediates and absorption cross-section of the ppR state at probe wavelength (σ1p). There is an optimum value of β for which maximum percentage modulation can be achieved. It is shown that for ppRM and ppRL states, at typical values, modulation up to 35.9% and 97.2% can be achieved for a laser write beam intensity of 5 mW/cm2 and 1 W/cm2 respectively. It is shown that 100% modulation of the read beam can be achieved for σ1p=0. SLM with ppR can be achieved at lower pump powers compared to wild type bacteriorhodopsin. The analysis demonstrates the usefulness of ppR for device applications due to its unique spectral characteristics, especially as a UV filter.

Analysis of low power spatial light modulation characteristics of bacteriorhodopsin

Summary We present a detailed and accurate analysis of low power spatial light modulation characteristics of bacteriorhodopsin (bR) based on nonlinear intensity induced absorption. Amplitude modulation of probe laser read beam transmissions at 410 nm and 640 nm, corresponding to the peak absorption of MII and O states of D96N bR and WT bR respectively, by the modulation laser write beam intensity-induced population changes at 570 nm has been analyzed, considering all intermediate states with both forward and backward transitions in the respective bR photocycles, using the rate equation approach. The SLM characteristics are shown to be sensitive to the normalized small signal absorption coefficient β, rate constants of MII and O intermediate states and the absorption cross-section of the initial B state at the probe wavelength (σBp). There exists an optimum value of β for which maximum percentage modulation can be achieved. It is shown that for extended MII state lifetime of 250 s in D96N bR and O state lifetime of 2.2 s in WT bR, with σBp= 0, 100% modulation of read beam transmissions can be achieved, leading to high dynamic range and sensitivity for low laser write beam intensities of 50 μW/cm2 and 4 mW/cm2 at 570 nm, respectively.

Analysis of spatial light modulation characteristics of C60

Spatial light modulation based on nonlinear absorption of light by excited-state molecules in C60–toluene solution is demonstrated. Amplitude modulation of probe laser beam transmissions at 747 and 885 nm, corresponding to the peak absorption of T1 and S1 states, by the modulation laser beam intensity induced population changes at 532 nm has been analyzed using the rate equation approach, for various values of the small-signal absorption coefficient. It is shown that for T1 and S1 states, modulation up to 100% and 94.5% can be achieved for a laser beam intensity of 800 W/cm2 and 1 kW/cm2 at 532 nm, respectively.

Spatial light modulator phase depth determination from optical diffraction information

A noninterferometric technique is presented for determining the phase modulating characteristics of spatial light modulators. Examining the far-field diffraction pattern intensity distribution for specific input functions enables the phase modulation to be calculated. Results are compared with usual interferometric techniques for a liquid crystal based modulator.

Spatial light modulation characteristics of reverse saturable absorber

Construction of a spatial light modulator (SLM) using reverse saturable absorber molecules is suggested. The SLM characteristics are derived using a recently proposed steady-state kinetic analysis. Results are presented for the rhodamine 6G dye molecules.

Liquid crystal television spatial light modulators

The spatial light modulation characteristics and capabilities of the liquid crystal television (LCTV) spatial light modulators (SLMs) are discussed. A comparison of Radio Shack, Epson, and Citizen LCTV SLMs is made.