Optical Scanner Reducing Size via Overlapping Torsion Bars
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Solution Overview
Problem
Existing optical scanners for projectors have large dimensions due to the arrangement of torsion bars and mirrors, leading to increased size and mass, which in turn require more driving force and result in inefficiencies in two-dimensional scanning.
Innovation Solution
The optical device features a movable portion rotatable about a first axis, a frame portion rotatable about a second axis, and a light reflecting plate that overlaps the shaft portions in the thickness direction, allowing for reduced size and increased light reflecting area while preventing stray light, using electromagnetic or piezoelectric driving methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the inner movable plate and second torsion bar are arranged so as not to overlap in plan view, then the structure is simple and easy to manufacture, but the overall dimensions increase depending on the dimensions of the mirror
Solution Approach 1:
The patent applies dimensionality change by transitioning from a planar arrangement to a three-dimensional overlapping arrangement. The light reflecting plate and second torsion bar are positioned to overlap when viewed from the thickness direction, utilizing the Z-axis dimension to resolve the spatial conflict. This allows the components to occupy the same projected area without physical interference, thereby reducing the overall device dimensions while maintaining structural integrity and manufacturability
2Area of moving object
If the dimensions of the inner movable plate increase, then the light reflecting area increases, but the second torsion bar needs to be arranged outside resulting in increased dimensions of the outer movable plate
Solution Approach 1:
The patent resolves this contradiction by allowing the second torsion bar to extend in the thickness direction and overlap with the light reflecting plate in plan view. This vertical arrangement enables the torsion bar to be positioned within the projected area of the light reflecting plate rather than outside it, allowing the outer movable plate dimensions to match the light reflecting plate dimensions without additional expansion
3Area of moving object
If the dimensions of the outer movable plate increase, then the mass of the outer movable plate increases, but the length of the first torsion bar increases and driving force required increases
Solution Approach 1:
The patent reduces the mass of the outer movable plate by enabling the second torsion bar to extend vertically and overlap with the light reflecting plate. This arrangement allows the outer movable plate to have dimensions matching only the light reflecting plate area, eliminating the need for additional material to accommodate externally positioned torsion bars, thereby reducing both mass and the driving force required
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 two-dimensional scanning with reduced device size, increased light reflecting area, and minimized stray light, while also reducing the moment of inertia and preventing warping of the light reflecting plate.
Implementation Method 1
a light reflecting plate which is separated from the first shaft portion in a thickness direction of the light reflecting plate and overlaps at least a part of the first shaft portion, as viewed from the thickness direction
Implementation Method 2
the interaction between the magnetic field which is generated from each coil by the application of a voltage and the magnetic field generated between a pair of permanent magnets causes the outer movable plate to be rotated about the X-axis together with the inner movable plate
Data Source
AI summary
An optical scanner is an optical device including a base portion that is rotatable about the Y-axis, a frame portion that is rotatable about the X-axis intersecting the Y-axis, and a shaft portion that supports the base portion so as to be rotatable about the Y-axis with respect to the frame portion. The optical scanner includes a light reflecting plate that is fixed to the base portion and includes a light reflecting portion with a light reflecting property. The frame portion is provided so as to surround the base portion. The shaft portion includes one end connected to the base portion and the other end connected to the frame portion. The light reflecting plate is separated from the shaft portion in the thickness direction of the light reflecting plate and overlaps the shaft portion, as viewed from the thickness direction.