Mirror Display Device Switching Optical States for Vehicle Rearview
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Solution Overview
Problem
Existing rearview mirrors for vehicles suffer from inadequate display characteristics when used as both mirrors and image displays, particularly due to the use of half mirrors which reduce light transmission and reflection efficiency, and liquid crystal anti-dazzle mirrors do not adequately account for viewing direction-dependent transmittance of TN-type liquid crystal cells.
Innovation Solution
A mirror display device comprising a monitor display element emitting polarized light, a reflection-type polarization plate, an absorption-type polarization plate, and a liquid crystal cell, configured to switch between reflective and transmissible states based on the viewing direction, ensuring optimal display characteristics by prioritizing transmission direction according to the user's perspective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a half mirror is used to enable both mirror function and image display function, then the device can serve dual purposes, but the light amount becomes approximately half in both transmission and reflection causing the screen to be dark
Solution Approach 1:
The patent applies a liquid crystal cell that can dynamically change its optical properties between two states: a reflective state for mirror function and a transmissive state for image display. This dynamic switching capability allows the device to optimize light transmission for each specific function, avoiding the compromise of using a static half mirror that reduces light amount in both modes.
Solution Approach 2:
The invention changes the optical parameters of the liquid crystal cell based on the required function. By applying different voltages, the liquid crystal cell alters its refractive index and optical axis orientation, thereby switching between reflecting polarized light (mirror mode) and transmitting polarized light (display mode), achieving high efficiency in both functions without the light loss inherent in half mirror designs.
2Object-affected harmful factors
If TN-type liquid crystal cells are used in anti-dazzle mirrors, then the device can provide anti-dazzle functionality, but the transmittance differs according to viewing directions resulting in insufficient display characteristics
Solution Approach 1:
The patent introduces an asymmetric optical element with different optical properties in different regions or directions. This element compensates for the viewing-angle-dependent transmittance characteristics of TN-type liquid crystal cells by providing direction-specific optical correction, ensuring uniform and high display visibility across all viewing directions while maintaining the anti-dazzle functionality.
Solution Approach 2:
The invention employs an asymmetric optical element that introduces deliberate asymmetry into the optical system to counterbalance the asymmetric viewing characteristics of the TN liquid crystal cell. This asymmetric compensation ensures that the overall system provides consistent display quality and anti-dazzle performance regardless of the viewer's position or angle.
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 device effectively exhibits suitable display characteristics by adjusting its optical states to prioritize image transmission or reflection based on the user's viewing direction, enhancing visibility and functionality as both a mirror and an image display, regardless of the vehicle's handedness or user's position.
Implementation Method 1
a liquid crystal cell which transmits the polarized light vibrating in the first direction while rotating a vibration direction of the polarized light by 90 degrees
Implementation Method 2
a reflection-type polarization plate for transmitting the polarized light vibrating in the first direction and reflecting polarized light vibrating in a second direction orthogonal to the first direction
Implementation Method 3
an absorption-type polarization plate for transmitting the polarized light vibrating in the first direction and absorbing the polarized light vibrating in the second direction
Data Source
AI summary
Provided is a mirror display device including a monitor display element for emitting image light vibrating in a first direction in an image display state; and a mirror optical element provided on the display surface side relative to the monitor display element. The mirror optical element can switch reflective and transmissible states. The reflective state is that light vibrating in a first direction from an absorption-type polarization plate side is converted to vibrate in a second direction by a liquid crystal cell to be reflected by a reflection-type polarization plate, and converted to vibrate in the first direction by the liquid crystal cell to be emitted from the absorption-type polarization plate. The transmissible state is that light vibrating in the first direction from a reflection-type polarization plate side is transmitted through the cell as it is, to be emitted from the absorption-type polarization plate.