Optical Sensor for Rotary Platen Synchronization
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Solution Overview
Problem
In high-speed rotary deposition systems, the lack of mechanical lock between the motor-driven spindle and the platen leads to synchronization issues between diagnostic devices and the rotating samples, making real-time monitoring and control of thin film growth parameters impossible.
Innovation Solution
An apparatus and method that uses a light source to project a circular swept path onto the rotating platen, detecting unique asymmetry features to generate a trigger pulse synchronized with the platen's rotational speed, enabling real-time synchronization of the diagnostic system with the platen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a non-positive coupling (magnetic or friction coupling) is used to connect the spindle drive to the platen, then the structural constraints are satisfied and sample transfer is enabled, but the phase angle drifts over time and synchronization is lost
Solution Approach 1:
The patent replaces the mechanical synchronization method (relying on mechanical lock between spindle and platen) with an optical detection system. A light source projects a beam onto the platen, and a detector measures the reflected light to generate a unique signal when detecting the asymmetry feature, thereby achieving synchronization without mechanical connection.
Solution Approach 2:
The patent introduces light as an intermediary to transfer information about platen position and speed. The light beam reflects off the platen surface, and the detector converts the optical signal into an electrical signal that indicates platen rotation status, enabling indirect measurement of platen synchronization.
2Productivity
If the platen rotates at high speed (above 1000 RPM), then productivity is improved, but the diagnostic device cannot diagnose sample locations in real-time due to spending many rotations on diagnosis
Solution Approach 1:
The patent uses a pre-designed asymmetry feature on the platen that is visible from the start. This feature serves as a predetermined reference point that the optical detector can immediately identify, eliminating the need for the diagnostic device to spend multiple rotations figuring out sample locations. The asymmetry feature is placed beforehand to provide instant synchronization cues.
Solution Approach 2:
The patent utilizes optical reflectivity differences (analogous to color changes) by designing an asymmetry feature with distinct optical properties compared to the rest of the platen surface. This feature reflects light differently, creating a detectable unique signal that allows the detector to instantly identify platen position and sample locations without requiring multiple rotation cycles for diagnosis.
3Reliability
If an asymmetry feature is introduced on the platen for optical detection, then synchronization can be achieved, but the platen design complexity increases
Solution Approach 1:
The patent deliberately introduces asymmetry into the otherwise symmetric platen design. A specific feature (such as a mark, pattern, or reflectivity variation) is placed at a known location on the platen. This asymmetry creates a unique optical signature that the detector can recognize, enabling the system to determine platen rotation position and speed without complex mechanical encoders or multiple sensors.
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 solution allows for real-time synchronization of the diagnostic system with the multiple sample platen, even in systems without a positive mechanical lock, ensuring accurate monitoring and control of thin film growth parameters, particularly at high rotation speeds.
Implementation Method 1
A light source projects a light beam onto a rotating platen... A detector measures light signals reflected from the platen
Data Source
AI summary
A method and apparatus for determining the synchronicity of a rotary platen (22) in a vacuum deposition chamber (24). A light source (64) projects a highly collimated light beam (66) onto the rotating platen (22), thereby tracing a circular swept path (67). The swept path (67) passes alternately through samples (20) on the platen (22) and intervening webs (58, 60). The samples (20) are significantly more reflective than the webs (58, 60). The platen (22) includes an asymmetry feature (60) along the swept path (67). A detector (62) measures light signals reflected from the platen (22) along the swept path (67), and generates a unique signal upon encountering the asymmetry feature (60). A microcontroller generates a trigger pulse synchronized to the unique signal.