Light Modulation Device Scattering Unmodulated Light for Holographic Safety
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Solution Overview
Problem
Holographic display devices using coherent light sources pose a risk to observers' eyes due to focused laser radiation, especially during malfunctions when scatter foils cannot be used as they destroy light coherence.
Innovation Solution
Incorporating an optical element with known scattering properties into the light modulation device to scatter unmodulated light in an angular range, preventing it from focusing into a single point and ensuring passive laser safety by distributing the light over an area, even during device malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a scatter foil is used to improve laser safety by scattering light, then light coherence is destroyed and holographic reconstruction cannot be achieved
Solution Approach 1:
The patent divides the optical system into two distinct functional components: a spatial light modulator for holographic modulation and a separate scattering optical element for safety. This segmentation allows each component to perform its specialized function without interfering with the other, enabling both holographic reconstruction and laser safety to coexist.
Solution Approach 2:
The scattering optical element acts as an intermediary component positioned between the light source and the spatial light modulator. It selectively scatters only the unmodulated light (zeroth diffraction order) while allowing the modulated holographic light to pass through, thus mediating between the conflicting requirements of coherence preservation and light scattering for safety.
2Object-affected harmful factors
If unmodulated light passes through the spatial light modulator during malfunction, then it focuses into a single point causing eye damage, but adding scattering elements may affect normal operation
Solution Approach 1:
The scattering optical element is pre-positioned in the optical path before the spatial light modulator. This preliminary arrangement ensures that during normal operation, the element does not interfere with the modulated light, but during malfunction when unmodulated light passes through, the scattering effect is automatically activated to prevent eye damage without requiring real-time detection or control.
Solution Approach 2:
The scattering optical element is designed with specific local properties - it has scattering characteristics that are optimized for the zeroth diffraction order (unmodulated light) while being transparent or minimally interfering with the modulated holographic light. This local quality differentiation allows the same component to serve dual purposes without compromising either function.
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
Significantly reduces the risk of eye damage by scattering light over a plane instead of focusing it, providing a high level of passive laser safety for observers, both during normal operation and in case of device failures.
Implementation Method 1
the optical element scatters the unmodulated light, which emanates from the spatial light modulator, in an angular range
Data Source
AI summary
A light modulation device for a display device, in particular a holographic display device, for the representation of two-dimensional and/or three-dimensional reconstructed scenes. The light modulation device includes at least one spatial light modulator including modulation elements for modulating incident light and an optical element of known optical characteristics. The light incident on the at least one spatial light modulator is sufficiently coherent. The at least one spatial light modulator and the optical element are combined with one another in such a way that the optical element scatters the unmodulated light emanating from the spatial light modulator into an angular range.