Intraoral Scanner Reflector Calibration Without Feedback Sensors
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Solution Overview
Problem
Calibration of MEMS-based scanners in handheld dental OCT systems is complex and costly, limiting their use due to high Q-factor and the need for additional sensors in closed-loop operations.
Innovation Solution
An intraoral scanner with a MEMS-based scanning reflector calibrated for open-loop control using an inverse system filter, eliminating the need for feedback sensors by directly measuring scanner nonlinearity with a calibration target and applying an inverse filter to stabilize the scanning beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop operation with additional sensors is used for MEMS scanner calibration, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and removes the additional sensors and closed-loop control systems from the MEMS scanner calibration process. By using open-loop control with pre-calibrated lookup tables and inverse system filters, the solution eliminates the need for feedback sensors, thereby reducing device complexity and cost while maintaining calibration precision through alternative mathematical compensation methods.
Solution Approach 2:
The patent replaces the mechanical/physical feedback sensor system with a computational approach using inverse system filters and lookup tables. Instead of using physical sensors to measure and correct scanner position in real-time, the system uses pre-computed correction algorithms that run on the control processor, substituting a mechanical measurement system with a software-based solution.
2Measurement precision
If closed-loop operation with additional sensors is used for MEMS scanner calibration, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the expensive additional sensors and closed-loop control hardware from the system. By implementing open-loop control with pre-calibrated lookup tables and inverse system filters stored in memory, the solution eliminates the need for costly feedback sensors, thereby reducing manufacturing cost while maintaining calibration precision through computational compensation.
Solution Approach 2:
The patent uses inexpensive lookup tables and software-based inverse system filters instead of expensive physical sensors. The calibration data is stored in memory as discrete lookup tables that can be easily updated or replaced, providing a low-cost alternative to permanent hardware sensor installations.
3Stability of the object's composition
If low-pass filtering is used for MEMS scanner calibration, then stability is improved, but bandwidth and performance are constrained
Solution Approach 1:
The patent changes the control approach from analog low-pass filtering to digital inverse system filtering. By using inverse system filters that are specifically designed for the MEMS scanner's transfer function, the system can maintain stability while preserving bandwidth. The inverse filter compensates for the scanner's resonant behavior mathematically rather than attenuating it, allowing the scanner to operate at higher frequencies without instability.
Solution Approach 2:
The patent replaces the traditional analog low-pass filter with a digital inverse system filter implemented in software. This substitution allows for more sophisticated control that can maintain stability while preserving the scanner's bandwidth, as the inverse filter can be designed to compensate for specific resonant frequencies rather than uniformly attenuating all high-frequency signals.
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
Simplifies the calibration process, reduces system complexity and cost, and ensures stable scanning without additional sensors, enabling efficient operation in handheld devices.
Implementation Method 1
a scanning reflector that is energizable to direct a scanning beam toward a surface in a raster pattern and to direct a beam reflected from the surface toward a detector
Data Source
AI summary
An intraoral scanner is disclosed for use with a dental optical coherence tomography system. The scanner has a scanning reflector that is energizable to direct a scanning beam in a raster pattern toward a sample surface. The scanning reflector is further to direct a reflected beam from the sample surface toward a detector. The scanning reflector is calibrated to direct the scanning and reflected beams in an open-loop control mode. A dental optical coherence tomography system and a method for calibration of a scanning reflector are also disclosed.