Actuator Movable Portion Shape for Optical Scanner Inertia
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Solution Overview
Problem
Existing optical scanners using torsional oscillators face challenges in manufacturing due to the difficulty in controlling the shape of movable plates with octagonal shapes, leading to large variations and high moment of inertia, which affects their performance in pivotal motion.
Innovation Solution
The design includes a movable portion with a shape that decreases in length stepwise from the swing axis, formed by anisotropically etching a silicon substrate, reducing shape variation and moment of inertia, and featuring a rectangular shape with perpendicular and parallel sides, truncated corners, and angled portions to enhance precision and pivoting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If an octagonal shape is used for the movable plate, then the moment of inertia is reduced, but the manufacturing precision deteriorates due to difficulty in controlling the shape during anisotropic etching
Solution Approach 1:
The patent changes the movable plate shape from octagonal to rectangular with rounded corners. This asymmetric modification maintains the moment of inertia reduction benefit while significantly improving manufacturability through anisotropic etching, as rectangular shapes align better with the crystallographic directions of silicon substrates used in the etching process
Solution Approach 2:
The patent modifies the geometric parameters of the movable plate by rounding the corners of the rectangular shape. This parameter change allows the shape to be precisely controlled during anisotropic etching while still achieving reduced moment of inertia compared to traditional designs, resolving the contradiction between shape control precision and moment of inertia reduction
2Weight of moving object
If the movable plate length parallel to the swing axis is reduced, then the moment of inertia decreases, but the resonance frequency may shift away from the optimal scanning range
Solution Approach 1:
The patent optimizes the length parameter of the movable plate parallel to the swing axis to achieve the desired resonance frequency range (4-40 kHz). By carefully controlling this dimension along with the rounded corner radius, the design reduces moment of inertia while maintaining the resonance frequency within the optimal scanning range
Solution Approach 2:
The patent designs the movable plate with rounded corners that dynamically balance the mass distribution, allowing the structure to achieve both reduced moment of inertia and appropriate resonance frequency characteristics for optical scanning applications
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 allows for reduced shape variation and moment of inertia, enabling the movable portion to pivot at resonance frequencies suitable for optical scanning with suppressed dynamic distortion, improving manufacturing precision and scanning performance.
Implementation Method 1
a connecting portion that extends from the movable portion and torsionally deforms in response to the swinging of the movable portion
Implementation Method 2
the movable portion, the support portion, and the connecting portion are formed by anisotropically etching a silicon substrate
Data Source
AI summary
An actuator including a movable portion that swings about a swing axis, a connecting portion that extends from the movable portion and torsionally deforms in response to the swinging of the movable portion, and a support portion that supports the connecting portion, wherein the movable portion is so shaped that the length thereof parallel to the swing axis decreases stepwise with distance from the swing axis in a plan view, and the movable portion, the support portion, and the connecting portion are formed by anisotropically etching a silicon substrate.