Retinal Image Display Using Dual Reflection-Type Holograms
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Solution Overview
Problem
The existing retinal projection devices using reflection type volume holograms suffer from dark lines and discoloration issues in the central portion of the projected image due to incomplete separation of light spectra and unnecessary diffraction.
Innovation Solution
An image display device utilizing a combination of first and second reflection type volume holograms, where the incident angle and connection angle satisfy specific conditions to prevent dark lines and discoloration, with the holograms facing each other substantially in parallel and the second hologram having a diffraction angle of approximately 0 degrees, and the incident light being p-polarized.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transmission type HOE is used to guide light flux to the retina, then the device structure is simplified, but the spectrum of diffracted light from each hologram of three colors cannot be completely separated due to low wavelength selectivity
Solution Approach 1:
The patent divides the single transmission type HOE into two separate reflection type HOEs: a deflective HOE for deflecting incident light and a condensing HOE for condensing diffracted light. This segmentation allows each hologram to be optimized for its specific function, achieving complete spectral separation while maintaining device simplicity.
Solution Approach 2:
The patent combines two reflection type HOEs with different functions (deflective and condensing) to form a pseudo transmission type HOE system. This merging of functional elements achieves the wavelength selectivity of reflection type HOEs while maintaining the optical path characteristics of transmission type HOEs.
2Measurement precision
If reflection type HOEs are used to achieve complete spectral separation, then wavelength selectivity is improved, but dark lines and discoloration occur in the central portion of the projected image due to unnecessary diffraction
Solution Approach 1:
The patent optimizes specific parameters of the reflection type HOEs, including the incident angle θi, connection angle θc, and diffraction angle. By satisfying specific angular relationships and using p-polarized light, the system achieves complete spectral separation while eliminating unnecessary diffraction that causes dark lines and discoloration in the central field of view.
Solution Approach 2:
The patent applies different functional characteristics to different regions of the HOE system. The deflective HOE is optimized for broad-angle deflection while the condensing HOE is optimized for on-axis condensing with approximately 0 degrees diffraction angle in the central portion, ensuring high image quality in the central field of view.
3Measurement precision
If the incident angle and connection angle are optimized for spectral separation, then wavelength selectivity is improved, but image quality deteriorates due to dark lines and discoloration in the central portion of the field of view
Solution Approach 1:
The patent establishes specific parameter relationships: incident angle θi and connection angle θc satisfy particular angular relationships, the diffraction angle of the central portion of the condensing HOE is approximately 0 degrees, and p-polarized light is used. These parameter optimizations simultaneously achieve complete spectral separation and eliminate dark lines and discoloration, ensuring high image quality.
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 effectively prevents dark lines and discoloration in the central portion of the projected image, ensuring high visual quality and commercial value by optimizing the hologram angles and polarization.
Implementation Method 1
the first reflection type volume hologram and the second reflection type volume hologram satisfy a Bragg condition for incident light of three colors of red, green, and blue
Implementation Method 2
the first reflection type volume hologram diffracts the incident light incident at an incident angle θi at a connection angle θc
Implementation Method 3
the first reflection type volume hologram and the second reflection type volume hologram satisfy a Bragg condition for incident light of three colors of red, green, and blue
Implementation Method 4
the second reflection type volume hologram condenses the deflected incident light
Implementation Method 5
By utilizing the wavelength selectivity of the reflection type HOE, the spectra can be completely separated and the respective projected light fluxes of the R/G/B light can be selectively diffracted in the respective holograms of R/G/B
Implementation Method 6
The incident light incident on the first reflection type volume hologram may be p-polarized light
Data Source
AI summary
An image display device in which dark lines and discoloration do not occur in the central portion of the field of view in the image projected on the retina. The present technology provides an image display device. The image display device includes a first reflection type volume hologram and a second reflection type volume hologram forming a transmission type diffraction element as a whole. The first reflection type volume hologram and the second reflection type volume hologram satisfy the Bragg condition for incident light of three colors of red, green, and blue. The first reflection type volume hologram diffracts incident light incident at an incident angle θi at a connection angle θc and deflects the incident light to the second reflection type volume hologram. The second reflection type volume hologram condenses the deflected incident light. The incident angle θi and the connection angle θc satisfy a specific condition.