Compound Holographic Optical Element for Diffuse Light Collimation
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Solution Overview
Problem
Existing methods fail to effectively collimate diffuse light due to limitations in diffraction efficiency and wavelength selectivity, particularly when there are changes in the playback setup compared to the recording setup, and simple light baffles do not redirect rays congruently.
Innovation Solution
A compound holographic optical element comprising three holographic optical elements, where the first reflection hologram records a continuous lens to receive a diverging light beam and diffract it as a collimated beam, the second reflection hologram receives and diffracts this beam further, and the third hologram, a transmission hologram, redirects it as a collimated beam, achieving efficient collimation by reducing angular and wavelength selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a simple light baffle is used to limit the cone angle of diffused light, then the angular spread is reduced, but the light rays are lost and not redirected congruently
Solution Approach 1:
A light redirecting member is introduced as an intermediary between the diffuser and the output. This member includes a first surface that receives diffused light and a second surface that redirects light rays congruently while maintaining optical path integrity, thereby reducing angular spread without losing light energy
Solution Approach 2:
The simple mechanical light baffle is replaced with an optically engineered light redirecting member that uses refractive or reflective surfaces to actively redirect light rays rather than merely blocking them, substituting passive mechanical obstruction with active optical redirection
2Device complexity
If a single hologram is used to collimate light, then the setup is simple, but it fails when there are changes in the playback setup compared to the recording setup
Solution Approach 1:
The single holographic element is segmented into multiple holographic elements (first, second, and third holograms) that work in sequence. Each element performs a specific collimation function, and the segmented system maintains collimation stability even when playback setup conditions change from recording conditions
Solution Approach 2:
The multi-element holographic system is designed to perform multiple collimation functions simultaneously - receiving light from various angles, correcting for setup variations, and producing collimated output - making it universally applicable across different playback configurations
3Loss of energy
If holographic elements with high angular and wavelength selectivity are used, then diffraction efficiency is high, but the system cannot handle changes in playback setup or different light sources
Solution Approach 1:
The selective diffraction function is segmented across multiple holographic elements, where the first hologram handles broad angular acceptance, the second handles wavelength variations, and the third produces final collimation. This segmentation allows each element to maintain high efficiency for its specific function while the overall system gains adaptability
Solution Approach 2:
The system utilizes parameter changes in the holographic elements - varying the thickness, grating spacing, and recording conditions of each element - to create a cascade of diffraction events that collectively maintain high efficiency while accommodating setup variations and different light sources
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 configuration allows for efficient collimation of diffuse light with high diffraction efficiency, maintaining collimation even with minor changes in the playback setup, and can handle both coherent and incoherent light sources, including broadband LEDs, by optimizing the thickness and lamination of holograms and adjusting the diffuser position.
Implementation Method 1
the first reflection holographic optical element will have recorded within it a continuous lens configured to receive light from a diverging light beam and diffract the received light as a first collimated light beam
Implementation Method 2
the second reflection holographic element having within it a second holographically reflective structure configured to receive the first collimated light beam and diffract the first collimated light beam as a second collimated light beam
Implementation Method 3
The third holographic optical element is configured to receive the second collimated light beam and diffract it as a third holographic light beam
Data Source
AI summary
A collimator can be made of a compound holographic optical element made of three holographic optical elements. The first reflection holographic optical element will have recorded within it continuous lens configured to receive light from a diffuse light beam and diffract the received light as a first collimated light beam. The second reflection holographic optical element will have recorded within it a regular hologram that is configured to permit the light from the diffuse light source to transmit through it to reach the first reflection holographic element, the second reflection holographic element having within it a second holographically reflective structure configured to receive the first collimated light beam and diffract the first collimated light beam as a second collimated light beam. The third transmission holographic optical element is configured to receive the second collimated light beam and diffract it as a third holographic light beam.