Compact Heads-Up Display Layout Using Polarized Folded Optics
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Solution Overview
Problem
Existing heads-up display systems face challenges in minimizing the volume required for projecting images while maintaining high reflectivity and transmission efficiency across different polarization states, leading to potential heating and damage from infrared radiation.
Innovation Solution
The use of a reflective polarizer and mirrors with specific polarization properties, combined with quarter wave plates, to optimize the path of image rays, minimizing volume usage and ensuring efficient transmission and reflection based on polarization, and incorporating cold mirrors to manage infrared radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional heads-up display optical systems are used, then image projection function is achieved, but the system volume is large and occupies excessive space
Solution Approach 1:
The patent combines multiple optical components (polarizer, mirrors, beam splitter) into a compact integrated optical system where components are closely spaced and share common optical paths. The polarizer is positioned adjacent to the beam splitter, and mirrors are arranged in a compact folded configuration, merging functions into a small volume while maintaining optical performance
Solution Approach 2:
The patent uses folded optical paths with mirrors arranged in three-dimensional space to achieve compact volume. By folding the optical path multiple times within a small footprint and using vertical stacking of components, the system achieves long optical paths in a compact dimensional footprint
2Object-affected harmful factors
If conventional optical components are used without polarization selectivity, then simplified design is achieved, but infrared radiation causes heating and potential damage
Solution Approach 1:
The patent applies polarization-selective properties specifically to the polarizer and mirror components that are in the direct optical path of the projected image, while allowing other components to have broader spectral transmission. The polarizer is positioned to selectively transmit or reflect polarized visible light while blocking infrared, and cold mirrors are used in specific locations to reflect infrared away from heat-sensitive components
Solution Approach 2:
The patent converts the harmful infrared radiation into a beneficial filtering mechanism by using polarizing components and cold mirrors that reflect infrared radiation away from the optical system. The infrared radiation that would normally cause heating is instead redirected, and the polarization-selective components use the infrared energy to demonstrate their filtering capability while protecting the system
3Object-affected harmful factors
If polarization-selective components are added to manage infrared radiation, then infrared protection is improved, but light transmission efficiency may deteriorate
Solution Approach 1:
The patent optimizes the spectral parameters of the polarizer and mirror coatings to achieve high visible light transmission (greater than 80% in the 450-650 nm range) while maintaining effective infrared reflection. The cold mirrors are designed with specific reflectivity parameters (greater than 90% in the infrared range) to maximize infrared blocking while minimizing visible light loss. The polarizer transmission axis is optimized to maximize visible light throughput
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 achieves a compact heads-up display design that efficiently projects images with minimal volume, reduces heating, and protects against infrared damage, while maintaining high reflectivity and transmission efficiency.
Implementation Method 1
the reflective polarizer transmits at least 80% of the incident light having a first polarization state and reflects at least 80% of the incident light having an orthogonal second polarization state
Implementation Method 2
each of the first and second mirrors reflects at least 80% of the incident light for at least one of the first and second polarization states
Data Source
AI summary
An optical system includes a reflective polarizer (20), and a display (10), first mirror (30a), and second mirror (30b) disposed on a same side of the reflective polarizer (20). The reflective polarizer (20) transmits an image emitted by the display (10) after the image is reflected by the first and second mirrors (30a, 30b). A mid-plane defined by intersection points between an optical axis of the system and the display (10), reflective polarizer (20), and second mirror (30b) has one-pass through four-pass regions having respective areas, A1 through A4. The one-pass region includes portions of the emitted image rays (15) that pass at least one time across the one-pass region, the two-pass region includes portions of the image rays (15) that pass at least two times across the two-pass region, the three-pass region includes portions of the image rays (15) that pass at least three times across the three-pass region, and the four-pass region includes portions of the image rays (15) that pass four times across the four-pass region, such that the ratio A4/A3 is between approximately 0.15 and approximately 0.40.