Figure 8 Rib Optical Mirror Resonant Frequency
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Solution Overview
Problem
Optical deflectors used in high definition projectors face a trade-off between resonant frequency and dynamic face-deflection peak-to-valley amount, where increasing resonant frequency to meet speed requirements often results in excessive deformation, and reducing deformation leads to insufficient resonant frequency.
Innovation Solution
An optical deflecting mirror device with a mirror and a figure '8'-shaped reinforcement rib on its rear surface, symmetrically aligned along the rocking axis, which consists of two coupled ring-shaped reinforcement ribs, enhancing rigidity and moment of inertia to balance both parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the optical deflecting mirror device is made thinner to increase resonant frequency, then the resonant frequency increases, but the rigidity decreases causing excessive deformation
Solution Approach 1:
The patent combines a thin mirror substrate with strategically placed reinforcement ribs to create a composite structure. The mirror maintains its thin profile (40μm) for high resonant frequency, while the ribs (extending 150-200μm from the surface) provide localized rigidity support, preventing bowl-shaped deformation without significantly increasing overall thickness or weight
Solution Approach 2:
Instead of uniformly thickening the entire mirror, the patent applies reinforcement ribs only at specific locations where structural support is most needed. The ribs are positioned to counteract the natural deformation patterns that occur during large-angle rocking, providing localized stiffness enhancement while preserving the thin overall structure for high resonant frequency operation
2Strength
If the optical deflecting mirror device is made thicker to increase rigidity, then the rigidity increases reducing deformation, but the moment of inertia increases causing resonant frequency to decrease
Solution Approach 1:
The patent creates a composite structure where a thin mirror substrate (40μm) is combined with surface-mounted reinforcement ribs. This composite approach provides the rigidity of a thicker structure without the penalty of increased moment of inertia, because the ribs are attached to the surface rather than requiring uniform thickness throughout the entire mirror volume
Solution Approach 2:
Instead of increasing rigidity by adding thickness in the Z-dimension (which would increase moment of inertia), the patent extends reinforcement elements in the X-Y plane by creating ribs that protrude from the mirror surface. This dimensional approach to reinforcement provides structural support without significantly increasing the mirror's overall mass or moment of inertia about the rocking axis
3Strength
If a ring-shaped reinforcement rib is added to increase rigidity, then the dynamic face-deflection is reduced, but the moment of inertia increases reducing resonant frequency
Solution Approach 1:
The patent enhances the ring-shaped reinforcement concept by adding a central rib that provides localized support at the mirror center. This central reinforcement addresses the specific deformation pattern that occurs during rocking without requiring a complete circumferential rib structure, thereby providing necessary rigidity with minimal additional mass and moment of inertia
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 the suppression of dynamic face-deflection peak-to-valley amount while increasing resonant frequency, ensuring the optical characteristics meet the requirements for high definition projectors by optimizing the structural design of the optical deflecting mirror device.
Implementation Method 1
the figure '8'-shaped reinforcement rib consists of two ring-shaped reinforcement ribs coupled to each other along the rocking axis... enhancing rigidity and moment of inertia
Data Source
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AI summary
An optical deflecting mirror device includes a circular or elliptical mirror (1a) with a reflective front surface, and a figure "8"-shaped reinforcement rib (1b, 1b') provided on a rear surface of the mirror (1a) symmetrically along a rocking axis (X) of the mirror (1a). The figure "8"-shaped reinforcement rib (1b, 1b') includes two ring-shaped reinforcement ribs (1b-1, 1b-2; 1b'-1, 1b'-2) coupled to each other along the rocking axis (X).