Spatial Light Modulator Tilt for Hologram Exposure
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Solution Overview
Problem
The contact copying method for producing high-resolution holograms results in unintentional faulty exposures due to interference effects, leading to incorrect pixel exposures, especially in 'grey-scale' images, causing variations in diffraction efficiency and falsifying stored information.
Innovation Solution
Tilting the surface normal of a spatial light modulator and a polarization-dependent beam splitter cube by a small angle (0.01° to 0.1°) to prevent interference-induced intensity fluctuations, which eliminates incorrect exposures by minimizing multiple reflections between the modulator and optical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the contact copying method is used to produce high-resolution holograms, then the manufacturing precision is improved, but interference effects cause incorrect pixel exposures and falsify stored information
Solution Approach 1:
The patent applies anti-reflective coatings to optical components in the beam path. These coatings are designed to minimize reflections at specific wavelengths and angles, converting the harmful interference effects into beneficial reduction of spurious reflections. The coatings have optimized refractive indices and thicknesses that create destructive interference for reflected waves while maintaining transmission, thereby eliminating the incorrect exposures that were falsifying the holographic data.
Solution Approach 2:
The patent modifies several parameters of the optical system to eliminate interference effects. This includes changing the angles of incidence of light beams on optical components, adjusting the wavelengths of laser sources, and modifying the physical dimensions and spacing of optical elements. By carefully selecting and optimizing these parameters, the system avoids resonant conditions that would create harmful interference patterns, thereby ensuring accurate pixel exposure while maintaining high resolution.
2Adaptability or versatility
If multiple optical components are placed in the beam path for spatial modulation, then the adaptability is improved, but multiple reflections between components cause interference and exposure errors
Solution Approach 1:
The patent applies anti-reflective coatings to all optical interfaces in the beam path, including beam splitters, modulators, and lenses. These coatings are engineered to minimize reflections at the specific wavelengths and angles used in the holographic system. By converting potentially harmful spurious reflections into transmitted light or absorbing them, the coatings eliminate interference effects while preserving the essential multiple reflections needed for spatial modulation and beam control.
Solution Approach 2:
The patent implements different anti-reflective coating solutions at different locations in the optical system. Each optical component receives coatings optimized for its specific position, angle of incidence, and wavelength requirements. This localized optimization ensures that each interface minimizes harmful reflections without compromising the overall spatial modulation capability of the system.
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 solution effectively reduces incorrect exposures, ensuring accurate reproduction of holographic images by stabilizing the energy dose and preventing interference effects, thereby enhancing the quality of high-resolution, individualized holograms.
Implementation Method 1
modulating the light beam with respect to its polarization state using a spatial light modulator
Implementation Method 2
A polarization-dependent beam splitter positioned between the LCoS modulator and the film reflects polarized light
Implementation Method 3
The diffraction patterns in the master diffract the light, causing it to be reflected back into the holographic film. There, it interferes with the coherent light used to illuminate the master. An interference pattern is thus formed in the holographic film
Implementation Method 4
The diffraction patterns in the master diffract the light, causing it to be reflected back into the holographic film
Data Source
Figure 1~2
AI summary
The device (200) has a beam guide optic (80) feeding a light of a light source to a spatial light modulator (50) e.g. digital micro-mirror device modulator, and supply a modulated light (22''') from the spatial light modulator. An upper surface normal (59) of the spatial light modulator is tilted opposite to an upper surface normal of a boundary surface (44) of a polarization-dependent beam splitter cube part (40) of the beam guide optic. The upper surface normal of the spatial light modulator passes the modulated light after the modulation at the spatial light modulator. An independent claim is also included for a holo-light.