Windshield Display Optics Using Polarization to Block Stray Image Light
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Solution Overview
Problem
Existing display systems that use a mirror unit to reflect image light from a display unit behind a windshield of a conveyance often result in image light being outputted outside the conveyance, leading to obstructed visibility when the mirror unit size is increased to prevent this issue.
Innovation Solution
A display system comprising an outputter behind the windshield, a reflector between the windshield and outputter, and optics with a polarizing plate that absorbs or reflects unreflected image light while allowing outside light to pass through, preventing image light from exiting the conveyance without obstructing visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the mirror unit size is increased to prevent image light from being outputted outside the conveyance, then the visibility obstruction increases
Solution Approach 1:
The patent segments the light management function by introducing a polarizing plate that selectively handles different light paths. The polarizing plate is positioned to intercept only the stray image light traveling toward the windshield, while leaving the outside light path unaffected. This segmentation allows precise control over which light rays are blocked without requiring a large mirror unit that would obstruct the driver's view.
Solution Approach 2:
The polarizing plate serves as an intermediary element between the mirror unit and the windshield. It mediates the interaction between image light and outside light by absorbing or reflecting only the polarized image light that would otherwise escape outside, while allowing non-polarized outside light to pass through freely. This intermediary component enables selective light control without the need for a large obstructive mirror.
2Object-affected harmful factors
If a polarizing plate is introduced to manage light, then the device complexity increases
Solution Approach 1:
The polarizing plate performs multiple functions simultaneously: it acts as a light absorber/reflector for image light, a polarizer for selective light management, and a visibility preserver for outside light. By consolidating these multiple light control functions into a single component, the patent avoids the need for multiple separate optical elements, thereby reducing overall device complexity while effectively preventing image light from escaping outside.
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
Effectively prevents image light from being outputted outside the conveyance while maintaining unobstructed visibility by using a polarizing plate to manage image and outside light, with optional features like λ/4 plates and correction lenses for improved image correction and light management.
Implementation Method 1
optics that includes a polarizing plate and is provided on the windshield or between the windshield and the reflector, the polarizing plate absorbing or reflecting the image light outputted from the output surface and not reflected at the reflecting surface, and allowing outside light that is light outside of the conveyance to pass through the polarizing plate
Data Source
AI summary
A display system includes: an outputter that is provided behind a windshield of a conveyance in a front-back direction of the conveyance and includes an output surface from which image light is outputted toward the windshield; a reflector that is provided between the windshield and the output surface and includes a reflecting surface at which the image light outputted from the output surface is reflected; and optics that includes a polarizing plate and is provided on the windshield or between the windshield and the reflector, the polarizing plate absorbing or reflecting the image light outputted from the output surface and not reflected at the reflecting surface, and allowing outside light that is light outside of the conveyance to pass through the polarizing plate.