Variable Focal Length Lens Device Using Rotating Liquid Crystal Layers
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Solution Overview
Problem
Existing lens devices with variable focal length, such as those using Alvarez lenses with liquid crystal films, face challenges in reducing size while maintaining functionality, as the size of the lens region is less than the liquid crystal film, and additional space is required for translation, leading to increased size in the in-plane direction.
Innovation Solution
A lens device comprising a first and second liquid crystal layer, each with a circular center portion and annular portions, where the layers are rotatable relative to each other without changing the distance between them, and the inner and outer diameters of the annular portions satisfy specific relationships to achieve a vortex alignment pattern, allowing for variable focal length without increasing the in-plane size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If two liquid crystal films are translated in the in-plane direction to change focal length, then the thickness of the lens in the optical axis direction is reduced, but the size in the in-plane direction increases due to required translation space
Solution Approach 1:
Instead of translating the liquid crystal films in the in-plane direction, this patent rotates the films relative to each other around the optical axis. This inversion of the movement direction (from in-plane translation to rotation around the optical axis) allows the lens to achieve variable focal length while maintaining a compact in-plane footprint, as the rotation occurs within the existing circular boundary of the liquid crystal films
Solution Approach 2:
The patent introduces rotational movement around the optical axis as a new degree of freedom. By rotating the liquid crystal films relative to each other while maintaining their positions in the in-plane direction, the system achieves focal length variation without requiring additional translation space, effectively utilizing the rotational dimension to solve the size contradiction
2Adaptability or versatility
If the lens moves in the optical axis direction to change focal length, then the focal length is variable, but the thickness of the HMD in the optical axis direction increases
Solution Approach 1:
The patent replaces the mechanical translation mechanism (moving the lens along the optical axis) with a rotational mechanism. By rotating the liquid crystal films relative to each other, the optical path and focal length are modified without requiring physical displacement of the lens assembly in the optical axis direction, thus maintaining a thin HMD profile while achieving variable focal length
Solution Approach 2:
The patent changes the optical parameters of the liquid crystal films by rotating them, which alters the effective refractive index distribution and focal length. This parameter-based control allows focal length variation without mechanical movement of the lens along the optical axis, avoiding the increase in HMD thickness
3Ease of manufacture
If the size of the lens region is made equal to the liquid crystal film size, then the lens utilization is maximized, but additional translation space is still required leading to increased in-plane size
Solution Approach 1:
The patent introduces dynamic rotational adjustment of the liquid crystal films relative to each other. This dynamic mechanism allows the lens to achieve variable focal length within the fixed circular boundary of the liquid crystal films, maximizing the utilization of the lens region without requiring additional translation space beyond the film diameter
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 lens device achieves a compact size with variable focal length by rotating the liquid crystal layers relative to each other, maintaining the lens region's size equivalent to the liquid crystal layers, thus overcoming the size increase issue in existing technologies.
Implementation Method 1
the center portion of the first liquid crystal layer has a vortex alignment pattern where α1=m×0.5 in a case where m represents an integer of 1 or more, and the n-th annular portion from the center portion of the first liquid crystal layer has a vortex alignment pattern where α1=(m+n)×0.5
Implementation Method 2
A lens device comprising: a first liquid crystal layer; and a second liquid crystal layer
Data Source
AI summary
Provided is a small lens device where a focal length is variable. Each of first and second liquid crystal layers includes a circular center portion and a plurality of annular portions, the first and second liquid crystal layers are rotatable relative to each other, inner diameters and outer diameters of the n-th annular portions from the center portions of the first and second liquid crystal layers are the same, and in polar coordinates of r and φ, in a case where a pattern where an angle θ1 of an optical axis in a region where φ is φ1 satisfies a relationship represented by Expression 3: {α1×φ1+θ0n1}−3°≤θ1≤{α1×φ1+θ0n1}+3° (where θ0n1 represents an angle of the optical axis of each of the center portion and the annular portions at φ1=0°) is set as a vortex alignment pattern, the center portion of the first liquid crystal layer has a vortex alignment pattern where α1=m×0.5, the n-th annular portion of the first liquid crystal layer has a vortex alignment pattern where α1=(m+n)×0.5, the center portion of the second liquid crystal layer has a vortex alignment pattern where α2=−(m×0.5), and the n-th annular portion of the second liquid crystal layer has a vortex alignment pattern where α2=−(m+n)×0.5.