Capacitive Mirror Actuator Tilt Control via Comb Electrodes
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Solution Overview
Problem
The actuator using a piezoelectric element in conventional mirror devices exhibits hysteresis and creep characteristics, making it difficult to control the degree of tilt of the mirror precisely.
Innovation Solution
The mirror device incorporates a movable comb electrode positioned closer to the second hinge than the first hinge, allowing for precise control of the mirror's tilt by detecting changes in capacitance between the movable and fixed comb electrodes, which extends the range where the degree of tilt can be accurately detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a piezoelectric element is used in the actuator, then the mirror can be tilted, but hysteresis and creep characteristics make it difficult to control the degree of tilt precisely
Solution Approach 1:
The patent introduces a feedback control mechanism using capacitance sensors (comb electrodes) to detect the actual mirror tilt angle. The detected capacitance value is fed back to the control unit, which adjusts the piezoelectric actuator output to compensate for hysteresis and creep effects, enabling precise control of the mirror tilt degree.
2Adaptability or versatility
If the movable comb electrode is disposed far from the fixed comb electrode, then the detection range can be extended, but the capacitance change becomes too small to detect accurately
Solution Approach 1:
The patent extends the detection range by utilizing the rotational movement dimension of the mirror. By positioning the comb electrodes appropriately and detecting capacitance changes during rotation, the system achieves a wide detection range (from -45 degrees to +45 degrees) while maintaining measurement precision through the rotational position-dependent capacitance variation.
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 precise control of the mirror's tilt and extends the range where the tilt can be detected, overcoming the hysteresis and creep issues associated with piezoelectric actuators.
Implementation Method 1
an actuator on which a piezoelectric element is stacked and a mirror coupled to the tip end of the actuator. This mirror device applies a voltage to the piezoelectric element to allow the actuator to curve, thereby tilting the mirror.
Implementation Method 2
a movable comb electrode coupled to the mirror; and a fixed comb electrode fixed to the base and facing the movable comb electrode. The actuator is controlled based on a capacitance between the movable comb electrode and the fixed comb electrode.
Data Source
AI summary
A mirror device includes a mirror, an actuator tilting the mirror, a first hinge coupling the mirror to the actuator, a base, a second hinge coupling the mirror to the base, a movable comb electrode coupled to the mirror, and a fixed comb electrode fixed to the base. The actuator is controlled based on a capacitance between the movable comb electrode and the fixed comb electrode. The movable comb electrode is disposed on a portion of the mirror closer to the second hinge than to the first hinge.