Holographic Sight Optics Design for High Light Throughput
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Solution Overview
Problem
Existing see-through optical sights for close combat suffer from low light throughput, color dispersion, and laser speckle issues, with current holographic sights requiring complex optics and alignment, and previous substrate-guided approaches failing to provide adequate field-of-view and eye relief while maintaining image quality.
Innovation Solution
A substrate-guided holographic sight using two coupled holographic optical elements with a thin transparent plate and a miniature LED module for diffusive illumination, optimized using ray-tracing techniques to achieve high light throughput and aberration-free reticle imagery without noticeable color shifts or speckle, and capable of large aperture sizes and low-cost mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional collimated optics are used for see-through sights, then the reticle image appears in the same plane as the target plane enabling precise targeting, but light throughput is low due to unavoidable losses from semitransparent optics
Solution Approach 1:
The patent replaces traditional mechanical optical systems (semitransparent mirrors, beam splitters) with a holographic optical element that uses light field modulation and total internal reflection to guide light paths, eliminating the need for multiple optical interfaces and reducing light loss
Solution Approach 2:
The patent utilizes total internal reflection at the substrate interface to guide light through the holographic element, leveraging the phase transition of light at the critical angle to achieve efficient light transmission without absorption losses
2Loss of energy
If narrowband reflecting dichroic mirrors are implemented to mitigate light throughput loss, then light transmission improves, but the system requires narrow bandwidth laser diodes which introduces laser safety concerns and speckle issues
Solution Approach 1:
The patent changes the spectral response parameter by using broadband transmission holograms instead of narrowband reflecting dichroic mirrors, allowing the system to work with broadband light sources and eliminating the need for narrowband laser diodes
Solution Approach 2:
The patent converts the previously harmful effect of broadband light causing color dispersion into a benefit by using a single broadband transmission hologram that simultaneously guides multiple wavelengths without requiring separate optical paths for different colors
3Loss of energy
If substrate-guided holographic optics are used to achieve high light throughput, then light transmission improves to >90%, but complex multi-element optics are needed to compensate aberrations requiring individual time consuming alignment
Solution Approach 1:
The patent merges multiple optical functions (beam guidance, aberration correction, image formation) into a single integrated holographic optical element, eliminating the need for separate optical components and their corresponding alignment procedures
Solution Approach 2:
The patent pre-corrects optical aberrations during the hologram recording process by incorporating compensating phase terms in the hologram design, so that aberration correction is built into the element itself rather than requiring post-fabrication alignment of multiple components
4Volume of moving object
If single hologram approach is used for compact see-through sight, then device compactness improves, but color dispersion occurs for broad-band light sources and unwanted shift in virtual image position occurs with laser-based narrow-band sources
Solution Approach 1:
The patent changes the recording wavelength parameter by recording the hologram at a wavelength different from the playback wavelength, and incorporates dispersion compensation terms in the hologram design to correct for wavelength-induced image position shifts
Solution Approach 2:
The patent introduces an intermediate wavelength parameter in the hologram recording process that acts as a mediator between the playback wavelength and the desired image position, allowing the system to compensate for wavelength drift and maintain stable image positioning
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
The solution provides a compact, reliable, and cost-effective see-through weapon sight with high light transmission, reduced parallax, and improved image quality, suitable for close combat up to 1000 m, ensuring shooter safety and precise targeting.
Implementation Method 1
a substrate-guided holographic lens coupled to a substrate-guided holographic grating through TIR in the substrate-guided holographic sight substrate
Implementation Method 2
two coupled holographic optical elements paired with a thin transparent plate
Data Source
AI summary
A method for design and fabrication of holographic optical elements for a compact holographic sight is proposed. The method includes use of ray-trace software to design holographic elements having optical power using an intermediate hologram with parameters obtained through minimization of the merit function defining image quality.