Diffusing Sheet with Elliptic Cylinder Lenses for Uniform Illumination
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Solution Overview
Problem
Conventional surface light source devices of the direct type suffer from poor light-converging properties and non-uniform illumination, leading to increased complexity and cost in LCD panels, as well as issues with light intensity variability depending on the distance from cathode ray tubes.
Innovation Solution
A diffusing sheet with a diffusion lens array featuring two types of unit lenses, one shaped like an elliptic cylinder and the other like a spheroid, arranged on the light-emerging side, which diffuses light uniformly by controlling light refraction and reflection to prevent unnecessary light spreading and enhance optical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple optical sheets are used to improve light convergence, then light-converging properties improve, but device complexity increases
Solution Approach 1:
The patent combines multiple optical functions (diffusion and light convergence control) into a single diffusing sheet with a specific refractive index distribution. This eliminates the need for multiple separate optical sheets while maintaining or improving light-converging properties, thus reducing device complexity.
Solution Approach 2:
The diffusing sheet performs multiple functions simultaneously: it diffuses light to achieve uniform illumination and controls light convergence through its specific refractive index distribution. This multi-functionality replaces what would traditionally require multiple specialized optical components.
2Manufacturing precision
If transmission type display device structure is improved to handle oblique light, then image quality improves, but manufacturing cost increases
Solution Approach 1:
The diffusing sheet acts as an intermediary component between the light source and the transmission type display device. It pre-processes the light by creating a specific intensity distribution that compensates for oblique incidence effects, allowing the display device to maintain image quality without requiring complex structural modifications.
3Illumination intensity
If cathode ray tubes are spaced further from display device, then light intensity uniformity improves, but total thickness increases
Solution Approach 1:
The patent changes the refractive index parameter within the diffusing sheet to control light propagation and intensity distribution. By adjusting the refractive index distribution, the system achieves uniform light intensity without increasing the distance between cathode ray tubes and the display device, thus maintaining compact thickness.
4Illumination intensity
If optical sheets increase light diffusion, then light intensity uniformity improves, but usable light amount decreases
Solution Approach 1:
The patent optimizes the refractive index distribution parameter in the diffusing sheet to achieve the right balance between diffusion and light transmission. The specific refractive index profile enables sufficient light diffusion for uniformity while minimizing light loss, thus preserving usable light amount.
Solution Approach 2:
The diffusing sheet has a non-uniform refractive index distribution where different regions have different refractive indices optimized for their specific functions. This local optimization ensures that light diffusion occurs where needed while maintaining high transmission efficiency in other regions, preserving usable light amount.
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 diffusing sheet achieves uniform illumination across the display screen regardless of the observation position, enhances optical efficiency, and prevents light from emerging at large angles, thereby reducing illumination non-uniformity and increasing usable light.
Implementation Method 1
A diffusing sheet with a diffusion lens array featuring two types of unit lenses, one shaped like an elliptic cylinder and the other like a spheroid, arranged on the light-emerging side, which diffuses light uniformly by controlling light refraction and reflection
Implementation Method 2
A diffusing sheet with a diffusion lens array featuring two types of unit lenses, one shaped like an elliptic cylinder and the other like a spheroid, arranged on the light-emerging side, which diffuses light uniformly by controlling light refraction and reflection
Data Source
AI summary
The present invention provides a diffusing sheet, a surface light source device, and a transmission type display, that can attain uniform illumination so that the brightness of light on the display screen appears uniform regardless of the position from which the display screen is observed. A transmission type display 10 comprises an LCD panel 11, and a surface light source device 16 for illuminating the LCD panel 11 from its rear. The surface light source device 16 includes a plurality of cathode ray tubes 13 that are arranged in parallel. A diffusing sheet 14 and a convergent sheet 12 are placed between the cathode ray tubes 13 and the LCD panel 11 in the surface light source device 16. The diffusing sheet 14 includes, on its light-emerging side surface, a diffusion lens array 141. The diffusion lens array 141 has a plurality of unit lenses (the diffusion lens array 141 is formed by regularly arranged unit lens groups each constituted by arranging a lower unit lens 141a and a higher unit lens 141b), each unit lens being in a shape equivalent to a part of an elliptic cylinder having an elliptical section. The convergent sheet 12 has a plurality of unit lenses 121 having almost trapezoidal cross sections, formed on its surface on the cathode ray tubes 13 side. It is therefore possible to attain uniform illumination by diffusing light from the cathode ray tubes 13 in the surface light source device 16. At the same time, it is possible to converge the light serving as backlight to enhance optical efficiency.