Dual-Cell Liquid Crystal Iris for Uniform Gray Shades
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Prior art liquid crystal irises for camera applications fail to provide a high contrast ratio with uniform transmittance at intermediate gray levels over a range of light input angles, making them unsuitable for miniature camera applications like smartphones.
Innovation Solution
A dual-cell liquid crystal iris configuration where the director field of the second liquid crystal device is a mirror image of the first, with parallel alignment of surface-contacting directors, reduces 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
1Reliability
If a TN liquid crystal device is used as a camera iris to achieve high contrast ratio, then the contrast ratio is improved, but the transmittance at intermediate gray levels becomes nonuniform over a range of incident angles
Solution Approach 1:
The single liquid crystal device is divided into two separate liquid crystal devices arranged in optical series. Each device has a different director field configuration (one with positive dielectric anisotropy and one with negative dielectric anisotropy), allowing them to compensate for each other's angular dependence and achieve uniform intermediate transmittance while maintaining high contrast ratio
Solution Approach 2:
The invention changes the dielectric anisotropy parameter of the liquid crystal devices by using one device with positive dielectric anisotropy and another with negative dielectric anisotropy. This parameter change allows the devices to have opposite angular dependence characteristics, which when combined, cancel out the angular variation and provide uniform intermediate transmittance
2Ease of operation
If liquid crystal iris designs are used to control light amount, then light control capability is improved, but angular dependence causes nonuniform exposure over the light-sensitive area
Solution Approach 1:
The system is segmented into two liquid crystal devices with opposite dielectric anisotropy signs, arranged in optical series. This segmentation allows each device to handle different aspects of light control, with their combined effect providing both excellent light control capability and uniform exposure across the light-sensitive area by canceling angular dependence
Solution Approach 2:
The invention uses a composite structure of two liquid crystal devices with different material properties (positive and negative dielectric anisotropy). This composite approach combines the light control capabilities of liquid crystal technology while eliminating the angular dependence issue that causes nonuniform exposure
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 configuration achieves a high contrast ratio of 1,000 with minimal angular variation of intermediate transmittances, making it suitable for camera applications by ensuring consistent light control across various angles.
Implementation Method 1
Electro-optic liquid crystal camera iris
Implementation Method 2
the birefringence of Δn＝0.1126 at the 550 nm design wavelength
Implementation Method 3
a positive dielectric constant anisotropy of 3.8
Data Source
AI summary
A high-contrast electro-optic liquid crystal camera iris provides angle independent transmission for uniform gray shades. The liquid crystal iris comprises a combination of first and second liquid crystal devices arranged in optical series and positioned between optical polarizers. The director field of the second liquid crystal device is a mirror image of the director field of the first liquid crystal device, and the first and second liquid crystal devices are placed together so that the azimuthal directions of the surface-contacting directors are in parallel alignment at the adjoining or confronting surfaces of the substrates 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 iris.