Semi-spherical Transmissive Window for MEMS Light Scanner
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Solution Overview
Problem
MEMS mirror scanners face interference issues due to sub-reflection from transmissive windows, which affect image quality and pose eye safety concerns, especially when the incident light and scan direction are in the same plane, making it challenging to design effective anti-reflection coatings and increasing light loss.
Innovation Solution
The optical scanner package features a semi-spherical or ellipsoidal transmissive window with curvatures in two axes, allowing different inclinations for incident and emission positions, reducing sub-reflection interference and facilitating easy anti-reflection coating design, along with a method for manufacturing this package using glass substrates and bonding techniques to maintain vacuum conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transmissive window is used to maintain vacuum, then vacuum integrity is improved, but sub-reflection interference increases
Solution Approach 1:
The patent applies a semi-spherical or ellipsoidal curvature to the transmissive window surface. This curvature changes the reflection geometry so that sub-reflected light is directed away from the scan region, reducing interference while maintaining the window's vacuum sealing function.
Solution Approach 2:
The transmissive window is designed with asymmetric curvature characteristics (semi-spherical or ellipsoidal rather than perfectly spherical), creating different reflection properties for incident light versus sub-reflected light. This asymmetric geometry enables angular separation of light paths to eliminate interference.
2Loss of energy
If anti-reflection coating is applied to increase transmittance, then light loss is reduced, but perfect ARC is impossible and sub-reflection remains
Solution Approach 1:
Instead of trying to eliminate sub-reflection through imperfect ARC, the patent converts the harmful sub-reflected light into a beneficial directional component by using curvature. The sub-reflection is redirected to serve the vacuum sealing function while avoiding the scan region, turning a harmful effect into a useful geometric feature.
Solution Approach 2:
The curved surface of the transmissive window provides inherent optical geometry that reduces the need for complex ARC structures. The curvature itself manages light paths, simplifying the coating requirements while achieving effective light control.
3Object-affected harmful factors
If the transmissive window is inclined to separate sub-reflected light, then interference is reduced, but the scanner element structure becomes more complex
Solution Approach 1:
The patent achieves light separation through the intrinsic curvature of the transmissive window itself, rather than requiring external inclination structures. The semi-spherical or ellipsoidal shape provides the necessary angular separation functionality, eliminating the need for additional mechanical inclination components.
Solution Approach 2:
The curved transmissive window performs multiple functions simultaneously: it maintains vacuum integrity, provides optical light path management, and achieves sub-reflection separation. This multi-functionality eliminates the need for separate structural components, reducing overall device complexity.
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 solution reduces sub-reflection interference, simplifies anti-reflection coating design, minimizes light loss, and allows for larger scan angles with reduced air resistance, enabling thinner and more efficient transmissive windows while maintaining high vacuum integrity.
Implementation Method 1
sub-reflection (see reference numeral 72) which is reflected from the surface of the transmissive window
Implementation Method 2
anti-reflection coating (ARC) may be applied to increase the transmittance of a transmissive window 50
Data Source
AI summary
The present disclosure relates to an optical scanner package comprising a scanner element, a lower substrate having an inner space, and a semi-spherical transmissive window. The semi-spherical transmissive window has different inclinations in an incident position thereof and in an emission position thereof, and interference caused by sub-reflection can thus be reduced. Since the incident angle α and the maximum emission angle β are small, anti-reflection coating design is easy, and light loss can be reduced. There is an advantage in that, even when the optical scanning angle (OSA) γ of a laser is large, the maximum emission angle β is small, and emitted laser light thus has a small change in characteristics. In addition, since there are curvatures on both sides of two axes, there is little restriction regarding the incident direction even in the case of two-axis driving.