Catadioptric Lens Assembly Reducing Form Error and Birefringence
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Solution Overview
Problem
Existing polarized, catadioptric lens systems face challenges in achieving high form accuracy and low birefringence due to large thickness variations in molded plastic lenses, which result in significant form error and birefringence.
Innovation Solution
The optical lens assembly includes a middle-lens disposed between an eye-lens and a display-lens, with each lens having an active lens region. The eye-lens has a substantially constant thickness, while the middle-lens has a maximum thickness greater than the eye-lens by at least a factor of 2, and the display-lens has a reflective polarizer to optimize light transmission and polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single molded plastic lens is used in a catadioptric lens system, then the device complexity is reduced, but the manufacturing precision deteriorates due to large thickness variations causing significant form error and birefringence
Solution Approach 1:
The single molded plastic lens is divided into multiple separate lens components (first lens, second lens, third lens) that are assembled together. Each lens component can be manufactured independently with controlled thickness variations, and the assembly is bonded using optical adhesive to form the complete lens system, thereby reducing form error and birefringence while maintaining manageable device complexity
Solution Approach 2:
The lens system combines multiple lens components made from different materials or configurations, bonded together using optical adhesive. This composite structure allows each component to be optimized for specific optical functions while the combination achieves the overall system performance, reducing the impact of thickness variations and improving form accuracy
2Device complexity
If a single molded plastic lens is used in a catadioptric lens system, then the device complexity is reduced, but the manufacturing precision deteriorates due to large thickness variations causing significant birefringence
Solution Approach 1:
The single molded plastic lens is divided into multiple separate lens components (first lens, second lens, third lens) that are assembled together. Each lens component can be manufactured independently with controlled thickness variations, and the assembly is bonded using optical adhesive to form the complete lens system, thereby reducing form error and birefringence while maintaining manageable device complexity
Solution Approach 2:
The lens system combines multiple lens components made from different materials or configurations, bonded together using optical adhesive. This composite structure allows each component to be optimized for specific optical functions while the combination achieves the overall system performance, reducing the impact of thickness variations and improving form accuracy
3Manufacturing precision
If the eye-lens has a substantially constant thickness, then the manufacturing precision is improved, but the device complexity increases due to the need for multiple lens components
Solution Approach 1:
The single molded plastic lens is divided into multiple separate lens components (first lens, second lens, third lens) that are assembled together. Each lens component can be manufactured independently with controlled thickness variations, and the assembly is bonded using optical adhesive to form the complete lens system, thereby reducing form error and birefringence while maintaining manageable device complexity
Solution Approach 2:
Different regions of the lens system have different thickness characteristics optimized for their specific functions. The eye-lens is designed with substantially constant thickness for form accuracy, while other lens components may have varying thicknesses optimized for their optical functions, allowing each component to be manufactured with appropriate precision
4Reliability
If the middle-lens has a maximum thickness greater than the eye-lens by at least a factor of 2, then the optical performance is improved, but the device complexity increases due to the need for precise thickness control
Solution Approach 1:
The single molded plastic lens is divided into multiple separate lens components (first lens, second lens, third lens) that are assembled together. Each lens component can be manufactured independently with controlled thickness variations, and the assembly is bonded using optical adhesive to form the complete lens system, thereby reducing form error and birefringence while maintaining manageable device complexity
Solution Approach 2:
The thickness parameter of the middle-lens is specifically designed to be greater than the eye-lens by at least a factor of 2, which optimizes the optical performance of the lens system. This parameter change is achieved through careful design and manufacturing of the individual lens components, with the understanding that the assembly will be bonded using optical adhesive to maintain the desired optical characteristics
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 reduces form error and birefringence, improving the contrast, efficiency, and primary image brightness of the lens assembly, while also simplifying the injection molding process.
Implementation Method 1
the display-lens has a reflective polarizer to optimize light transmission and polarization
Implementation Method 2
the reflective polarizer transmits at least 50% of the normally incident light having a first polarization state and reflects at least 50% of the normally incident light having an orthogonal second polarization state
Implementation Method 3
each of the first through third at least partially light transmitting layers transmits at least 30% of the normally incident light having a first polarization state, and each of the second and third at least partially light transmitting layers rejects at least 30% of the normally incident light having an orthogonal second polarization state
Data Source
AI summary
An optical lens assembly includes a middle-lens disposed between, and bonded to, an eye-lens and a display-lens, each of the lenses including an active lens region defined as a maximum lens region configured to transmit an image emitted by a display therethrough. A first at least partially light transmitting film is disposed on, and substantially conforming to, a curved first major surface of the eye-lens. A second at least partially light transmitting film is disposed between, and substantially conforming to each of, a curved second major surface of the eye-lens and a curved first major surface of the middle-lens. A first retarder layer is disposed between, and substantially conforming to each of, a second major surface of the middle-lens and a first major surface of the display-lens; and a third at least partially light transmitting film is disposed on, and substantially conforming to, a curved second major surface of display-lens.