LCoS Phase Shift Profile Ripple Reduction
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Solution Overview
Problem
The existing WSS devices using liquid crystal on silicon (LCoS) devices face issues with non-uniform luminosity variations across segments, leading to undesirable ripples in optical signals due to varying minimum and maximum luminosity levels, which affect the optical characteristics and steering accuracy.
Innovation Solution
A base stepped phase shift profile is selected for the programmable optical phase shift modulator, with adjustments to reduce variations in minimum and maximum luminosity levels across segments, maintaining a consistent slope and steering angle, thereby minimizing ripple in optical signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a base stepped phase shift profile is applied to the programmable optical phase modulator to steer optical beams, then the optical device functions as a blazed grating with beam steering capability, but non-uniform luminosity variations across segments produce undesirable ripples in optical signals
Solution Approach 1:
The patent applies local quality by adjusting the drive voltage or phase shift values for specific pixels or pixel groups within segments to compensate for luminosity variations. Each segment's parameters are locally optimized to achieve uniform luminosity across all segments while maintaining the overall blazed grating phase profile for beam steering.
Solution Approach 2:
The patent changes the electrical parameters (drive voltage, RMS voltage, or phase shift values) applied to different pixels or segments of the LCoS device. By dynamically adjusting these parameters, the system compensates for luminosity variations and eliminates ripples while preserving the beam steering function.
2Manufacturing precision
If varying voltages are applied to liquid crystal pixels to control light transmission and create gray scale, then the desired gray scale levels are achieved, but non-uniform luminosity variations occur across segments
Solution Approach 1:
The patent implements a feedback mechanism where the actual luminosity output of each segment is measured or calculated, and this information is used to adjust the drive voltages for subsequent frames or iterations. This closed-loop control ensures both accurate gray scale levels and uniform luminosity across all segments.
Solution Approach 2:
The patent applies preliminary correction factors or lookup tables that pre-compensate for known luminosity variations across different segments. Before displaying the actual image or optical pattern, the system pre-adjusts the voltage levels for each segment to predictably achieve uniform luminosity output.
3Measurement precision
If the slope of segments in the phase shift profile is adjusted to maintain beam steering angle, then the steering accuracy is maintained, but luminosity variations between segments increase
Solution Approach 1:
The patent introduces asymmetric adjustments to the phase shift profile where different segments have slightly modified slopes or phase values compared to the ideal symmetric blazed grating profile. These asymmetric corrections are specifically designed to equalize luminosity across segments while maintaining the overall beam steering angle through compensatory adjustments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the optical characteristics of WSS devices by reducing luminosity variations, improving signal processing and steering accuracy while maintaining the desired steering angle, thus reducing crosstalk and enhancing the overall performance of LCoS-based optical devices.
Implementation Method 1
The liquid crystal material in the LCoS device rotates the polarization of light that passes through it, the extent of the polarization rotation depending on the root-mean-square (RMS) voltage that is applied across the liquid crystal layer
Implementation Method 2
The spatial separation of spectral components is directed onto predetermined regions of the LCoS device, which can be independently manipulated by driving the corresponding pixels in a predetermined manner
Data Source
AI summary
A method selects a phase shift profile to be applied to a programmable optical phase shift modulator having an array of pixels. A base stepped phase shift profile for the modulator is selected such that when applied to the modulator, the base stepped phase shift profile allows the modulator to function as a blazed grating steering an optical beam through a prescribed angle. The base stepped phase shift profile has a plurality of segments each extending over a given number of the pixels defining a linear array of pixels. Each segment has first and last pixels in the linear array of pixels. Variations in minimum and maximum luminosity levels among the segments of the base stepped phase shift profile are reduced so that any changes to a slope of each segment arising from reducing the variations in the minimum and maximum luminosity level is maintained below a given amount.