Optical Deflector Asynchronous Drive Voltage Harmonic Suppression
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Solution Overview
Problem
Existing two-dimensional optical deflectors face challenges in suppressing resonant harmonic frequency components in drive voltages, leading to higher frequency vibrations and limited deflection angles, making them impractical for image display applications like projectors.
Innovation Solution
The use of asynchronous saw-tooth drive voltages with a predetermined phase difference for the outer piezoelectric actuators, ensuring that the rising and falling periods of the drive voltages are adjusted to suppress resonation with the natural frequency of the mirror's vibrating system, allowing for longer linear deflection periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If synchronous saw-tooth drive voltages are used to drive the outer piezoelectric actuators, then the mirror can be rocked with respect to the Y-axis for vertical deflection, but harmonic frequency components in the drive voltages resonate with the natural frequencies of the mechanically-vibrating system of the mirror, causing higher frequency vibration
Solution Approach 1:
The patent applies asymmetry by using asynchronous drive voltages with different phases for the first and second groups of outer piezoelectric actuators. Specifically, the drive voltage for the first group has a phase different from that for the second group, which asymmetrically distributes the harmonic frequency components and prevents them from coinciding with the natural frequencies of the mirror system, thereby suppressing resonance while maintaining deflection functionality.
Solution Approach 2:
The patent changes the phase parameter of the drive voltages applied to different groups of actuators. By adjusting the phase difference between drive voltages for the first and second groups of outer piezoelectric actuators, the harmonic frequency components are shifted away from the natural frequencies of the mirror system, eliminating resonance without reducing the fundamental deflection frequency.
2Object-affected harmful factors
If the natural frequencies are made much larger than the fundamental frequency of the drive voltages to avoid resonance, then resonance is suppressed, but the mechanically-vibrating system becomes hardened and it becomes difficult to rock the mirror at a larger deflection angle
Solution Approach 1:
Instead of increasing natural frequencies (which would harden the system), the patent uses asymmetric phase distribution in drive voltages to suppress resonance. This allows the system to maintain its mechanical compliance and achieve larger deflection angles while avoiding resonance through phase-based harmonic suppression rather than frequency-based stiffening.
3Object-affected harmful factors
If synchronous sinusoidal-wave drive voltages with frequency much larger than natural frequencies are used, then resonance is avoided, but the linearly-deflected period within one period becomes too small, making it impractical for image display apparatus
Solution Approach 1:
The patent uses asynchronous saw-tooth wave drive voltages with different phases for different actuator groups, which suppresses harmonic resonance while maintaining a long linear deflection period suitable for image display. This asymmetric phase approach allows the use of lower fundamental frequencies with adequate linear periods, unlike the synchronous high-frequency sinusoidal approach.
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 approach effectively suppresses resonant harmonic frequency components and enables longer linear deflection periods, making the optical deflector suitable for image display applications such as projectors while maintaining stable operation.
Implementation Method 1
outer piezoelectric actuators 6a-1 to 6a-4 and 6b-1 to 6b-4... serving as cantilevers for rocking the mirror 1 through the movable frame 2 with respect to a Y-axis of the mirror perpendicular to the X-axis
Implementation Method 2
A difference in phase between the first and second saw-tooth waves is a predetermined value to suppress resonation of harmonic frequency components of the first and second drive voltages with a natural frequency of a mechanically-vibrating system of the mirror
Data Source
AI summary
An optical deflector includes a mirror, a movable frame for supporting the mirror, a support body surrounding the movable frame, and a first group of piezoelectric actuators and a second group of piezoelectric actuators alternating with the first group of piezoelectric actuators. A driver applies a first drive voltage having first saw-tooth waves to the first group of piezoelectric actuators, and applies a second drive voltage having second saw-tooth waves opposite in phase with the first saw-tooth waves to the second group of piezoelectric actuators. A difference in phase between the first and second saw-tooth waves is a predetermined value to suppress resonation of harmonic frequency components of the first and second drive voltages with a natural frequency of a mechanically-vibrating system of the mirror with respect to the axis thereof depending upon the piezoelectric actuators.