OCT Reference Arm Switching for Wide-Range Laser Machining
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Solution Overview
Problem
Conventional optical coherence tomography (OCT) devices in laser machining systems have limited measuring ranges, requiring multiple reference sections and complex control mechanisms, which increase costs, space requirements, and adjustment efforts, while also limiting distance measurements at the edges of the scanning field.
Innovation Solution
An OCT device with a reference arm structure that utilizes both positive and negative measuring ranges by employing a controllable switching element to switch between reference sections, allowing for a compact and cost-effective design that extends the measuring range without the need for numerous reference sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple reference sections with different lengths are used to extend the measuring range, then the measuring range is improved, but the device complexity and number of components increase
Solution Approach 1:
The patent applies dynamics by making the reference arm length adjustable through a motor-driven mechanism. The reference arm can be dynamically extended or retracted to match different optical path length differences, allowing a single reference arm to replace multiple fixed-length reference sections. This dynamic adjustment capability resolves the contradiction by providing extended measuring range without proportionally increasing the number of reference sections.
Solution Approach 2:
The patent changes the parameter of reference arm length from fixed to variable. By using a motor-driven extension mechanism, the reference arm length can be continuously adjusted to compensate for different optical path length differences caused by scanner deflection angles. This parameter change allows a single reference arm to cover the entire scanning range, eliminating the need for multiple discrete reference sections.
2Measurement precision
If a large number of reference sections are provided to cover the entire scanning range, then the measuring range is improved, but the space requirements and manufacturing costs increase
Solution Approach 1:
The patent makes the single reference arm universal by enabling it to perform multiple functions through dynamic length adjustment. The same reference arm serves all measuring positions across the entire scanning range by being extended or retracted as needed, rather than requiring separate dedicated reference sections for each position. This multi-functionality reduces the total number of components and associated manufacturing costs.
Solution Approach 2:
The motor-driven extension mechanism provides dynamic adaptability, allowing the reference arm to be configured for different measuring scenarios. This single dynamic component replaces multiple static components, reducing manufacturing complexity and cost while maintaining the ability to cover the entire scanning range.
3Adaptability or versatility
If the optical path length changes with scanner deflection, then the scanning functionality is improved, but the OCT measuring range becomes insufficient at the edges of the scanning field
Solution Approach 1:
The patent implements feedback by using the scanner deflection angle information to control the extension state of the reference arm. The system monitors the scanner position and automatically adjusts the reference arm length to compensate for the changing optical path length difference. This feedback mechanism ensures that the measuring range remains sufficient across the entire scanning field, including at the edges where optical path length changes are most significant.
Solution Approach 2:
The control unit receives scanner deflection angle signals and uses this information to drive the motor mechanism that adjusts the reference arm length. This closed-loop feedback ensures that the reference arm is always at the appropriate length to maintain measurement capability across the full scanning range, resolving the edge-of-field measuring range insufficiency.
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 enables a significant reduction in the number of required reference sections, allowing for continuous distance measurements across a wide range, including areas with varying heights due to mechanical tolerances, while maintaining a compact and cost-effective setup.
Implementation Method 1
Optical coherence tomography (OCT) uses interference effects to determine distance differences with respect to a reference distance
Data Source
AI summary
An optical coherence tomography device for a laser machining system for measuring distance to an object in a predetermined distance range comprises: a measuring arm for directing a measuring light beam at the object; a reference arm for guiding a reference beam with a plurality of reference sections having different measuring ranges; and a controllable switching element for switching between the reference sections of the reference arm. The measuring range of each reference section comprises a negative active measuring range and a positive active measuring range, between which a dead zone is located. The dead zone of one of the reference sections is overlapped by a positive or negative active measuring range of at least one other reference section. The positive and negative active measuring ranges of the reference sections together cover the predetermined distance range.