Holographic Recording Haze Reduction via Moveable Light Source
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Solution Overview
Problem
Haze and stray light are problematic in holographic gratings, resulting from parasitic gratings, contamination, recording beam nonuniformities, and diffraction by unused reactants, which can lead to reduced diffraction efficiency and higher diffraction orders, appearing as fixed pattern noise.
Innovation Solution
A method and system that utilize a moveable light source with a grating or deflector to produce intersecting beams, moving them in a direction parallel to the fringe vector of the holographic interference pattern to maintain stationary exposure angles, thereby canceling unwanted intensity nonuniformities and reducing haze through spatio-temporal displacement of defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stationary light source is used to form holographic interference patterns, then the recording process is simple and stable, but unwanted intensity nonuniformities and haze are introduced due to fixed pattern noise and parasitic gratings
Solution Approach 1:
The patent applies dynamics by moving the light source or recording medium during the holographic recording process. This dynamic movement causes spatio-temporal displacement of intensity nonuniformities and parasitic gratings, transforming fixed pattern noise into time-varying patterns that average out to zero, thereby reducing haze while maintaining recording stability
Solution Approach 2:
The patent employs periodic action through sinusoidal or random modulation of the light source position or recording medium movement. This periodic displacement creates time-varying interference patterns that cancel unwanted intensity nonuniformities through destructive interference, effectively reducing haze while preserving the desired holographic structure
2Object-affected harmful factors
If the light source is moved to cancel intensity nonuniformities, then haze is reduced, but the recording system becomes more complex
Solution Approach 1:
The patent applies self-service by using the movement mechanism itself to generate the cancellation effect. The same motion that simplifies the system (comparing stationary vs moving) also provides the spatio-temporal displacement needed to cancel intensity nonuniformities, eliminating the need for separate complex noise cancellation systems
Solution Approach 2:
The patent employs parameter changes by modulating the position, orientation, or other parameters of the light source or recording medium during exposure. These parameter changes create time-varying interference patterns that average out unwanted intensity nonuniformities, reducing haze while maintaining relatively simple system architecture
3Reliability
If moving the light source is used to displace intensity nonuniformities, then diffraction efficiency is maintained, but exposure time increases due to the movement required
Solution Approach 1:
The patent uses periodic action with sinusoidal or random modulation at frequencies optimized for haze cancellation. By selecting appropriate modulation frequencies and durations, the system achieves effective intensity nonuniformity cancellation within practical exposure times, balancing haze reduction with recording speed
Solution Approach 2:
The patent applies dynamics through controlled movement of the light source or recording medium. The movement is designed to be minimal yet sufficient to achieve spatio-temporal displacement of parasitic gratings, maintaining short exposure times while effectively reducing haze and preserving diffraction efficiency
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 effectively minimizes haze while maintaining high diffraction efficiency, applicable to various holographic recording materials, including photopolymers and liquid crystal mixtures, with minimal impact on grating quality and diffraction efficiency.
Implementation Method 1
a moveable light source configured to produce at least two intersecting light beams for forming a holographic interference pattern in the holographic recording medium
Implementation Method 2
During the recording process, the monomers polymerize, and the mixture undergoes a photopolymerization-induced phase separation
Implementation Method 3
the mixture undergoes a photopolymerization-induced phase separation, creating regions densely populated by liquid crystal (LC) micro-droplets, interspersed with regions of clear polymer
Implementation Method 4
The moveable light source is configured to move the two intersecting light beams in a direction such that the holographic interference pattern remains stationary however there is spatio-temporal displacement and cancellation of unwanted intensity nonuniformities
Data Source
AI summary
Methods and systems for forming holographic gratings are described herein. The methods and systems may decrease the amount of haze produced during exposure of a holographic recording medium. In some embodiments, the methods and systems include a holographic recording medium; a master hologram containing a grating; and a light source and moveable deflector configured to diffract light through the master hologram into the holographic medium to form a holographic interference pattern. The moveable deflector is configured to move in a direction parallel to the extending direction of the grating. Advantageously, moving the light in this direction allows the holographic interference pattern to remain stationary while there is a spatio-temporal displacement and cancellation of unwanted intensity nonuniformities.