MEMS Mirror Optical Scanning Polarization Control
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Solution Overview
Problem
Optical scanning apparatuses face challenges in ensuring a vignetting margin and minimizing bow when using MEMS mirrors due to their small size, and existing layouts either compromise on vignetting margin or increase apparatus thickness.
Innovation Solution
Incorporating a first polarizing member that reflects one polarization component and passes another with a half-wavelength phase difference, and a second polarizing member that introduces a quarter-wavelength phase difference, allowing the beam light to enter the deflection mirror squarely, ensuring a vignetting margin and minimizing bow, while also reducing the apparatus's thickness and size through strategic optical axis alignment and the use of a reflection mirror.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the beam light enters the deflection mirror obliquely from the side to prevent interference with emitted light rays, then the optical path can be compacted, but the effective area of the reflection surface becomes narrow making it difficult to ensure a vignetting margin
Solution Approach 1:
The patent employs asymmetric optical path design where the beam light enters the deflection mirror squarely at an angle with respect to the rotation axis, rather than symmetrically from the side. This asymmetric entry angle allows the beam to utilize the full effective area of the reflection surface while maintaining a adequate vignetting margin, resolving the contradiction between maximizing reflection area and ensuring reliable operation.
2Reliability
If the beam light squarely enters the deflection mirror at an angle with respect to the rotation axis to ensure a vignetting margin, then the vignetting margin is improved, but the optical path extends in the direction of the rotation axis increasing the thickness of the apparatus
Solution Approach 1:
The patent reconfigures the optical path by introducing a reflection mirror that redirects the beam light in a different spatial dimension. Instead of the optical path extending linearly in the direction of the rotation axis (increasing thickness), the reflection mirror folds the optical path, allowing the beam to enter squarely at an angle while keeping the apparatus thickness compact. This dimensional reconfiguration resolves the contradiction between ensuring vignetting margin and minimizing apparatus thickness.
3Manufacturing precision
If the beam light squarely enters the deflection mirror to minimize bow, then the sub-scanning line bow is reduced, but the optical path extends in the direction of the rotation axis increasing the apparatus thickness
Solution Approach 1:
The patent uses a reflection mirror to fold the optical path in a different spatial dimension, allowing the beam light to enter the deflection mirror squarely for minimal bow while preventing the optical path from extending linearly in the rotation axis direction. This dimensional folding maintains compact apparatus thickness while achieving the precision benefit of square entry.
4Shape
If a prism and quarter wavelength plate are used to form the optical path from lower incidence to upper incidence, then the optical path is configured, but the distance between the two reflection points becomes long increasing the size of the deflection mirror
Solution Approach 1:
The patent extracts and eliminates the unnecessary prism and quarter wavelength plate from the optical path configuration. By removing these components, the distance between reflection points is significantly reduced, allowing the use of a smaller deflection mirror while maintaining the required optical path functionality from lower incidence to upper incidence.
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 enables beam light to enter the deflection mirror squarely, ensuring a vignetting margin and minimizing bow, while reducing the optical scanning apparatus's thickness and size by optimizing the optical paths and using a reflection mirror to maintain parallel optical axes.
Implementation Method 1
a first polarizing member that reflects the first polarization component included in the beam light toward the deflection mirror and passes a second polarization component having a phase difference of a half-wavelength with respect to the first polarization component
Implementation Method 2
a second polarizing member that causes a phase difference of a quarter wavelength to the passing beam light
Implementation Method 3
a deflection mirror that is rotationally driven so as to reflect the beam light toward a scanned object while scanning in a main scanning direction
Data Source
AI summary
An optical scanning apparatus includes a first polarizing member and a second polarizing member between a light source and a MEMS mirror that is a deflection mirror. The first polarizing member reflects a first polarization component included in a beam light emitted from the light source so as to squarely enter the MEMS mirror and passes a second polarization component having a phase difference of a half-wavelength with respect to the first polarization component. The second polarizing member is provided between the first polarizing member and the MEMS mirror to pass the first polarization component reflected by the first polarizing member therethrough twice before and after being reflected by the MEMS mirror to change the first polarization component into the second polarization component. A rotation axis of the MEMS mirror is parallel to an optical axis of the beam light immediately before being reflected by the first polarizing member.