Dual Optical Sheet for Uniform Luminance in Surface Light Sources

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Solution Overview

Problem

Surface light source devices face challenges in achieving uniform in-plane luminance distribution due to lower luminance in intermediate regions between light emitters, which cannot be adequately addressed by conventional light diffusing sheets, leading to inefficiencies and the need for additional light diffusing components.

Innovation Solution

The use of a dual optical sheet configuration where the first optical sheet has unit shaped elements extending in a direction intersecting the arrangement direction, and the second optical sheet has elements extending in a direction perpendicular to the first, with specific angle and proportion criteria to enhance light condensing and diffusing functions, reducing the need for separate diffusing sheets.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a light diffusing sheet with strong light diffusing effect is used to equalize in-plane luminance distribution, then in-plane luminance uniformity is improved, but light source utilization efficiency deteriorates

Engineering Contradiction:

Improvein-plane luminance uniformityVSAvoidlight source utilization efficiency

Core Design Contradiction:

Manufacturing precisionVSLoss of energy

Solution Approach 1:

The patent combines the light condensing function and light diffusing function into a single optical sheet. The optical sheet includes a body portion and unit shaped elements that simultaneously perform both functions, eliminating the need for a separate light diffusing sheet and thereby maintaining light source utilization efficiency while achieving uniform in-plane luminance distribution.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The optical sheet is designed to perform multiple functions: it acts as both a light condensing sheet (enhancing front direction luminance) and a light diffusing sheet (equalizing in-plane luminance distribution). This multi-functionality resolves the contradiction by achieving luminance uniformity without requiring an additional component that would reduce light efficiency.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Manufacturing precision

If a separate light diffusing sheet is added to equalize in-plane luminance distribution, then in-plane luminance uniformity is improved, but device complexity increases

Engineering Contradiction:

Improvein-plane luminance uniformityVSAvoidnumber of optical components

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges the functions of the light condensing sheet and light diffusing sheet into a single integrated optical sheet. This optical sheet includes a body portion and unit shaped elements that simultaneously provide light condensing (enhancing front direction luminance) and light diffusing (equalizing in-plane luminance) effects, thereby reducing the total number of components while achieving the desired luminance uniformity.

Inventive Principle:

Principle #5Merging (Combining)

3Illumination intensity

If conventional light condensing sheets are used to enhance front direction luminance, then front direction luminance is improved, but in-plane luminance uniformity deteriorates

Engineering Contradiction:

Improvefront direction luminanceVSAvoidin-plane luminance uniformity

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

The optical sheet integrates both light condensing and light diffusing functions into a single component. The unit shaped elements are configured to simultaneously enhance front direction luminance (light condensing effect) and equalize in-plane luminance distribution (light diffusing effect), thereby resolving the contradiction between these two functions without requiring separate components.

Inventive Principle:

Principle #5Merging (Combining)

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 effectively reduces in-plane luminance variation, enhances front direction luminance, and obscures the image of light sources, improving light utilization efficiency and potentially eliminating the need for separate diffusing sheets.

Implementation Method 1

unit lenses, each having a shape corresponding to part of a circle or an ellipse in a section (main section) perpendicular to the longitudinal direction, are most commonly used as the unit shaped elements. Such an optical sheet can change the travel direction of light and adjust the angular distribution of luminance

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

a light diffusing sheet for diffusing light from the light source to shade (obscure) the image of the light source

Methodology Applied

Scientific EffectLight diffusion: Scattering

Data Source

PatentUS8696187B2Surface light source device, optical member, and display device

Publication Date: 2014.04.15 DAI NIPPON PRINTING CO LTD

AI summary

An optical member includes a first optical sheet, and a second optical sheet disposed on the light exit side of the first optical sheet. The optical sheets each include a body portion, and unit shaped elements arranged side by side on the body portion. The ratio of the height of the unit shaped elements relative to the arrangement pitch of the unit shaped elements in the first optical sheet is smaller than that in the second optical sheet.