Optical Stack Polarizer Alignment Using a Wavelength-Tuned Half-Wave Retarder
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional manufacturing processes for optical stacks require costly and time-consuming steps to align the reflection axis of reflective polarizers and absorption axis of absorbing polarizers, often leading to increased defects and higher production costs due to the use of achromatic half-wave retarders.
Innovation Solution
An optical stack design incorporating a reflective polarizer with orthogonal transmission and reflection axes, a half-wave retarder with optimized retardance, and an absorbing polarizer, where the half-wave retarder is disposed between the reflective and absorbing polarizers, minimizing color shifts and reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional manufacturing processes are used to align the reflection axis of reflective polarizers and absorption axis of absorbing polarizers, then the optical stack can be assembled, but the manufacturing time and process expense increase
Solution Approach 1:
The patent changes the optical parameters of the half-wave retarder by optimizing its retardance for specific wavelengths (blue and red regions). This parameter optimization enables the retarder to compensate for wavelength-dependent phase shifts, allowing the reflection axis and absorption axis to be aligned without costly cutting and rotation operations. The specific retardance values are tuned to achieve effective alignment across the display's emission spectrum.
Solution Approach 2:
The half-wave retarder acts as an intermediary optical element between the reflective polarizer and absorbing polarizer. It mediates the alignment issue by introducing controlled phase shifts that compensate for the misalignment between the reflection axis and absorption axis, thereby enabling effective polarization without mechanical realignment operations.
2Reliability
If achromatic half-wave retarders are used to align polarizers, then the optical performance is maintained, but the production costs increase
Solution Approach 1:
Instead of using an achromatic half-wave retarder that performs uniformly across all wavelengths, the patent applies local quality by optimizing the retarder's performance for specific critical wavelengths (blue and red regions) where the display's emission spectrum has significant energy. This targeted approach maintains optical performance where it matters most while reducing manufacturing costs.
Solution Approach 2:
The patent changes the retardance parameter of the half-wave retarder from a fixed achromatic value to wavelength-specific optimized values. By tuning the retardance for blue and red wavelengths separately, the patent achieves effective polarization alignment without requiring expensive achromatic materials, thereby reducing production costs while maintaining necessary optical performance.
3Ease of manufacture
If the half-wave retarder is optimized for specific wavelengths, then the manufacturing cost is reduced, but the optical performance across all wavelengths may be compromised
Solution Approach 1:
The patent optimizes the half-wave retarder's retardance parameter for specific wavelengths (blue and red regions) that correspond to the display's emission spectrum peaks. This parameter optimization reduces manufacturing costs by avoiding expensive achromatic materials while maintaining effective optical performance in the critical wavelength regions where the display operates.
Solution Approach 2:
The patent applies local quality by focusing the half-wave retarder's optimization on specific wavelength regions (blue and red) rather than attempting uniform performance across the entire visible spectrum. This approach maintains optical performance where it is most needed for display operation while reducing manufacturing costs.
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 design reduces color shifts and manufacturing costs by optimizing the half-wave retarder for specific wavelengths, allowing for easier and cheaper production while maintaining optical performance.
Implementation Method 1
The reflective polarizer includes mutually orthogonal transmission and reflection axes. For substantially normally incident light and a first polarization state, the reflective polarizer reflects at least about 60% of the incident light for at least a first wavelength less than the cut-off wavelength and transmits at least about 50% of the incident light for at least a second wavelength greater than the cut-off wavelength.
Implementation Method 2
For substantially normally incident light, the half-wave retarder has a first retardance of less than about 250 nanometers (nm) at the first wavelength and a second retardance at the second wavelength. A deviation of the first retardance from a first half-wave retardance corresponding to the first wavelength is less than a deviation of the second retardance from a second half-wave retardance corresponding to the second wavelength.
Implementation Method 3
For substantially normally incident light and the first polarization state, the absorbing polarizer has a first transmittance at the first wavelength and a greater second transmittance at the second wavelength.
Data Source
AI summary
An optical stack includes a reflective polarizer, an absorbing polarizer, and a half-wave retarder. The half-wave retarder is disposed between the reflective and absorbing polarizers. For substantially normally incident light and a first polarization state, the reflective polarizer reflects at least about 60% of the incident light for at least a first wavelength less than a cut-off wavelength and transmits at least about 50% of the incident light for at least a second wavelength greater than the cut-off wavelength. For substantially normally incident light, the half-wave retarder has a first retardance of less than about 250 nanometers (nm) at the first wavelength and a second retardance at the second wavelength. A deviation of the first retardance from a first half-wave retardance corresponding to the first wavelength is less than a deviation of the second retardance from a second half-wave retardance corresponding to the second wavelength.