Wavelength-Dependent Reflection Film for OLED Virtual Image Displays
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Solution Overview
Problem
Virtual image display apparatuses, such as head-mounted displays, face challenges in achieving high contrast and uniform color balance while extending the life of the light source, particularly when using OLEDs, as they often result in deviations in color balance and reduced luminance, affecting image quality and visibility.
Innovation Solution
Incorporating a reflection film with wavelength-dependent reflectance characteristics in the light guide optical path, which adjusts reflectance inversely proportional to brightness across different wavelength ranges, ensuring uniform color balance and extending the life of the light source by optimizing luminance and reducing color deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If OLED is used for light emitting part to achieve higher contrast, then image contrast is improved, but color balance deviates and luminance decreases
Solution Approach 1:
The patent applies parameter changes by introducing a reflection film with wavelength-dependent reflectance characteristics. This film selectively reflects different wavelengths of light at different rates, compensating for the color balance deviations caused by OLED aging. The reflectance ratio between blue (430-490nm) and green (491-580nm) wavelength ranges is specifically controlled to maintain uniform color balance over time.
2Illumination intensity
If OLED is used for light emitting part to achieve higher contrast, then image contrast is improved, but light source life is reduced
Solution Approach 1:
The patent uses parameter changes by designing a reflection film whose wavelength-dependent reflectance characteristics are specifically tailored to compensate for OLED aging effects. The film's reflectance ratio between different wavelength ranges is optimized to maintain uniform color balance, thereby extending the effective operational life of the OLED light source.
3Reliability
If reflection film with wavelength dependence is introduced to correct color balance, then color balance uniformity is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by implementing a reflection film with spatially varying reflectance characteristics. The film's reflectance ratio is locally optimized for different wavelength ranges (higher for blue 430-490nm, lower for green 491-580nm) to compensate for color balance deviations. This localized optical property adjustment corrects color uniformity without requiring complex mechanical or electronic systems.
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 solution achieves high-contrast, uniformly balanced images with extended light source life, maintaining clear see-through vision by balancing transmittance and reflectance, even when using OLEDs, thereby enhancing the overall visual recognition and image quality in virtual image display systems.
Implementation Method 1
a reflection film having light transmissivity and having wavelength dependence that provides higher reflectance for light in a blue wavelength range (430 nm to 490 nm) than reflectance for light in a green wavelength range (491 nm to 580 nm)
Data Source
AI summary
In an image generation unit, a light emitting part is formed using a self-emitting OLED device, and thereby, high-contrast images can be formed and the life of the light emitting part and the life of the virtual image display apparatus are extended. Even when the light emitted in the light emitting part has deviation in color balance, a half-mirror layer that has light transmissivity and realizes see-through vision is a reflection film having wavelength dependence, and thereby, a uniform color balance of image lights is achieved and images in good conditions are visually recognized.