Dual-Cell Liquid Crystal Iris for Uniform Gray Shades
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional liquid crystal irises for miniature cameras, such as those in smartphones, face challenges in achieving high contrast ratios with uniform transmittance at intermediate gray levels over a range of light input angles, leading to nonuniform exposure and unsatisfactory performance.
Innovation Solution
A dual-cell liquid crystal iris design where the director field of the second liquid crystal device is a mirror image of the first, with parallel alignment of surface-contacting directors, reducing angular variation of intermediate transmittances by ensuring light passes through each device in optimal orientations, achieving a high contrast ratio and uniform gray levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional TN liquid crystal device is used for camera iris, then a high contrast ratio is achieved, but the transmittance at intermediate gray levels becomes nonuniform over a range of incident light angles
Solution Approach 1:
The liquid crystal device is divided into two separate liquid crystal cells arranged in optical series, each with complementary director fields. This segmentation allows each cell to contribute differently to the overall optical performance, with the first cell providing high contrast ratio and the second cell compensating for angular dependence to maintain uniform intermediate transmittance across viewing angles.
Solution Approach 2:
The director fields of the two liquid crystal cells are configured with asymmetric orientations relative to each other. The first cell has a director field oriented at a specific angle, while the second cell has a director field oriented at a complementary angle, creating an asymmetric configuration that balances high contrast ratio with angular independence of intermediate transmittance.
2Device complexity
If a single liquid crystal device is used for camera iris, then device complexity is reduced, but uniform transmittance at intermediate gray levels over a range of light input angles cannot be achieved
Solution Approach 1:
The liquid crystal device is divided into two separate liquid crystal cells arranged in optical series, each with complementary director fields. This segmentation allows each cell to contribute differently to the overall optical performance, with the first cell providing high contrast ratio and the second cell compensating for angular dependence to maintain uniform intermediate transmittance across viewing angles.
3Illumination intensity
If liquid crystal iris provides high contrast ratio, then light blocking capability is improved, but uniform exposure over the light-sensitive area cannot be ensured due to angular dependence
Solution Approach 1:
The liquid crystal device is divided into two separate liquid crystal cells arranged in optical series, each with complementary director fields. This segmentation allows each cell to contribute differently to the overall optical performance, with the first cell providing high contrast ratio and the second cell compensating for angular dependence to maintain uniform intermediate transmittance across viewing angles.
Solution Approach 2:
The director fields of the two liquid crystal cells are configured with asymmetric orientations relative to each other. The first cell has a director field oriented at a specific angle, while the second cell has a director field oriented at a complementary angle, creating an asymmetric configuration that balances high contrast ratio with angular independence of intermediate transmittance.
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 dual-cell design significantly reduces angular variation of intermediate transmittances, making it suitable for camera applications by providing a high contrast ratio and maintaining uniform gray levels over a wide range of light input angles.
Implementation Method 1
electro-optic liquid crystal camera iris
Implementation Method 2
The cell gap is chosen as 4.23 μm to satisfy the 'first minimum' condition Δn·d/λ=0.866 to provide maximum throughput at the design wavelength
Data Source
AI summary
A high-contrast electro-optic liquid crystal camera iris (10) provides angle independent transmission for uniform gray shades. The liquid crystal iris comprises a combination of first and second liquid crystal devices (12, 14) arranged in optical series and positioned between optical polarizers (46, 48). The director field (18) of the second liquid crystal device is a mirror image of the director field (16) of the first liquid crystal device, and the first and second liquid crystal devices are placed together so that the azimuthal directions (42) of the surface-contacting directors (18c, 22c) are in parallel alignment at the adjoining or confronting surfaces of the substrates (242, 321) of the first and second liquid crystal devices. The liquid crystal iris provides, therefore, less angular variation of intermediate transmittances compared with that provided by prior art liquid crystal irises.