Optical Element Resin Substrate Thermal Expansion Control
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Solution Overview
Problem
In display devices using diffraction elements, the deformation of resin substrates due to thermal expansion and interference exposure leads to changes in diffraction angles, resulting in undesirable performance, as the hologram layer adhered to the substrate deforms, affecting the formation of interference fringes.
Innovation Solution
An optical element with a hologram layer adhered to a resin substrate, supported by a holder portion with a lower thermal expansion coefficient and higher elastic modulus than the substrate, which includes convex and concave portions for contact and pressing, respectively, to stabilize the substrate during interference exposure and usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the resin substrate is used to support the hologram layer, then the device can be manufactured with ease and kept lightweight, but the resin substrate deforms due to thermal expansion during interference exposure and usage, causing deterioration in diffraction performance
Solution Approach 1:
The patent combines a resin substrate with a holder portion made of a material having a smaller thermal expansion coefficient (such as metal or ceramic) to create a composite structure. This composite structure maintains the ease of manufacture and lightweight properties of the resin substrate while adding thermal stability through the holder portion, thereby preventing deformation during interference exposure and usage.
2Device complexity
If the resin substrate is used to support the hologram layer, then the device structure can be simplified, but the resin substrate expands or contracts with environmental temperature changes, causing the hologram layer to deform and diffraction angles to change significantly
Solution Approach 1:
The patent creates a composite structure where a holder portion with low thermal expansion coefficient is integrated with the resin substrate. This composite design maintains structural simplicity while providing thermal stability, ensuring that the hologram layer remains undistorted and diffraction angles remain consistent across varying environmental temperatures.
Solution Approach 2:
The patent changes the thermal expansion parameter by introducing a holder portion made of material with a smaller thermal expansion coefficient than the resin substrate. This parameter change compensates for the thermal expansion of the resin substrate, maintaining the dimensional stability of the hologram layer and consistent diffraction performance across temperature variations.
3Productivity
If the hologram material is adhered to the resin substrate and interference exposure is performed, then the diffraction element can be formed, but the hologram material expands or contracts during exposure, causing the resin substrate to deform and interference fringes to form with incorrect diffraction angles
Solution Approach 1:
The patent employs a composite structure consisting of a resin substrate and a holder portion with low thermal expansion coefficient. During interference exposure, this composite structure prevents the resin substrate from deforming due to thermal expansion or contraction of the hologram material, ensuring that interference fringes are formed with precise and correct diffraction angles while maintaining efficient production.
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 suppresses deformation of the resin substrate, maintaining consistent diffraction performance across varying environmental temperatures, ensuring stable and desired diffraction characteristics in the hologram layer.
Implementation Method 1
the holder portion has a thermal expansion coefficient smaller than that of the resin substrate... as a result of the resin substrate expanding or contracting in accordance with an environmental temperature
Implementation Method 2
the other of the holder portion and the resin substrate includes a pressing surface that presses the contact surface
Implementation Method 3
One of the resin substrate and the holder portion may include a concave portion, and the other of the resin substrate and the holder portion may include a convex portion that is inserted into the concave portion
Data Source
AI summary
An optical element includes a hologram layer, a resin substrate to which the hologram layer is adhered, and a holder portion that supports the resin substrate and has a thermal expansion coefficient smaller than that of the resin substrate. One of the holder portion and the resin substrate includes a contact surface along an axis extending in a plate thickness direction of the resin substrate, and the other of the holder portion and the resin substrate includes a pressing surface that presses the contact surface.