Optical Element with Spaced Diffraction Gratings
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Solution Overview
Problem
Existing optical elements with diffraction gratings face challenges in precise adjustment and alignment due to adhesive contraction, leading to changes in grating intervals and inclination, affecting the optical performance.
Innovation Solution
The optical element employs translucent substrates with diffraction gratings and gap materials to control substrate spacing and orientation with high precision, using fillers with matching refractive indices to minimize refraction and reflection, and allows for angular adjustments based on light observation to achieve precise grating alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If two translucent substrates are adhered using an adhesive agent in a state of being opposed to each other, then the optical element can be assembled, but changes in intervals between diffraction gratings and inclination will be generated due to adhesive contraction
Solution Approach 1:
A gap material is introduced as an intermediary substance between the first and second translucent substrates. This gap material maintains a predetermined interval between the substrates, preventing the adhesive agent from causing direct contact and subsequent contraction that would alter the grating intervals. The gap material acts as a spacer that preserves the precise spacing required for optical performance.
Solution Approach 2:
The refractive index of the gap material is specifically selected to match or closely approximate the refractive index of the translucent substrates. This parameter matching minimizes optical refraction and reflection at the interfaces, eliminating adverse optical effects while maintaining the mechanical spacing function.
2Ease of manufacture
If adhesive agent is used to adhere substrates, then assembly is achieved, but inclination with respect to off-plane direction will be generated
Solution Approach 1:
The gap material serves as a mediator that maintains the parallel orientation of the two substrates. By filling the space between the substrates with a material of matched refractive index, it prevents the adhesive from creating uneven bonding forces that would cause inclination. The gap material ensures both substrates remain parallel to each other and to the diffraction gratings.
3Manufacturing precision
If diffraction gratings are arranged with high precision, then optical performance is improved, but alignment adjustment becomes complex
Solution Approach 1:
The gap material with matched refractive index enables the optical element to self-align optically. When light passes through the gap material and diffraction gratings, the matched refractive indices minimize refraction and reflection, allowing the system to maintain precise alignment without requiring complex external adjustment mechanisms. The optical paths are preserved naturally through the matched index interface.
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 enables precise control of diffraction grating intervals and orientations, enhancing the optical performance by maintaining accurate alignment and reducing optical distortions, thus improving the light flux splitting and pupil expansion capabilities.
Implementation Method 1
a first adhesive layer which includes a first gap material which is interposed between the second surface and the third surface and which adheres the second surface and the third surface
Implementation Method 2
a first filler with a refractive index equal to that of the first substrate and the second substrate is filled between the second surface and the third surface in the effective region
Implementation Method 3
it is possible to suppress refraction, reflection, and the like on the second surface and the third surface
Implementation Method 4
a first diffraction grating which is provided on at least one of the first surface and the second surface, a second diffraction grating which is provided on at least one of the third surface and the fourth surface
Data Source
AI summary
In an optical element, a first diffraction grating, a second diffraction grating, a third diffraction grating, and a fourth diffraction grating are formed in each of a first surface of a first substrate, a fourth surface of a second substrate, a fifth surface of a third substrate, and an eighth surface of a fourth substrate. Each substrate is fixed by (a first adhesive layer, second adhesive layer, and a third adhesive layer) adhesive layers including a gap material. A first filler with a refractive index equal to that of the first substrate and the second substrate is filled between the first substrate and the second substrate and a third filler formed of air or a medium with a refractive index equal to that of air is filled between the second substrate and the third substrate.