Optical Sheet Layout for Driver-Side Viewing Angle Suppression
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Solution Overview
Problem
Conventional optical sheets for vehicle display devices installed in front passenger seats fail to effectively control image light emission towards the driver's side and windshield reflection, leading to visibility issues for the driver.
Innovation Solution
An optical sheet with a trapezoidal light transmitting portion and a light absorbing portion between adjacent transmitting portions, configured to control light emission angles within specific ranges, reducing relative transmittance to 1% or less in certain directions and maintaining light transmittance at 100% in others.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional optical sheet with light transmitting portions extending in one direction is used, then the viewing angle can be controlled in the direction perpendicular to the extending direction, but the viewing angle cannot be controlled in the parallel direction, causing image light to be visible from lateral directions including the driver's side
Solution Approach 1:
The light transmitting portions are configured with a trapezoidal cross-section where the width in the first direction varies along the extending direction, creating asymmetric light transmission properties. This asymmetry enables different viewing angle characteristics in perpendicular directions, blocking lateral light toward the driver while maintaining front viewing capability
Solution Approach 2:
The invention extends the control dimension by making the light transmitting portions extend in an oblique direction rather than purely in the first or second direction. This oblique extension introduces a new geometric dimension that simultaneously controls viewing angles in both perpendicular directions, solving the limitation of conventional sheets that could only control one direction
2Illumination intensity
If a conventional optical sheet is used to control viewing angle, then front direction emission is maintained, but light emission at ±20° to ±30° lateral angles remains visible, interfering with driver visibility
Solution Approach 1:
The optical sheet implements spatially varying light transmission properties through the oblique extension of light transmitting portions. Different regions of the sheet exhibit different light transmission characteristics, with the oblique geometry creating zones that selectively block light at specific angles while transmitting light in the front direction
3Adaptability or versatility
If conventional optical sheets are used in front passenger seat displays, then display function is provided, but image light reflects on the windshield, causing visibility interference for the driver
Solution Approach 1:
The asymmetric trapezoidal configuration of light transmitting portions creates directional light transmission properties that prevent symmetric reflection patterns. This asymmetry in the oblique direction specifically directs light away from windshield reflection angles while maintaining display functionality for the front passenger
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 optical sheet effectively controls image light emission and reflection, ensuring minimal visibility from the driver's side and maximizing light transmission for the front passenger, while maintaining overall luminance.
Implementation Method 1
an optical functional layer including a plurality of light transmitting portions having a predetermined cross-section and extending in one direction, and a light absorbing portion formed between the adjacent light transmitting portions
Implementation Method 2
The predetermined cross-section of the light transmitting portion is a trapezoid, with a shorter upper base being a light-incident side
Data Source
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AI summary
The present disclosure provides an optical sheet comprising a substrate layer, and an optical functional layer stacked on one surface of the substrate layer, wherein the optical sheet has a rectangular shape including a pair of first sides extending in a first direction and a pair of second sides extending in a second direction in a plan view; the optical functional layer includes a plurality of light transmitting portions having a predetermined cross-section and extending in one direction, and a light absorbing portion formed between the adjacent light transmitting portions; the predetermined cross-section of the light transmitting portion is a trapezoid, with a shorter upper base being a light-incident side; when a light transmittance in a third direction perpendicular to the first direction and the second direction is regarded as 100%, a relative transmittance, that is a ratio of a light transmittance in a direction ±30° inclined toward the first direction with respect to the third direction, is 1% or less; and an extending direction of the light transmitting portion has an angle of 5° or more and 20° or less, with respect to the second direction.