Laser Focus Position Determination via Measurement Marking Scanning
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Solution Overview
Problem
Ophthalmological laser projection systems face challenges in accurately determining the focus position of laser pulses due to production tolerances and thermal expansions, leading to measurement inaccuracies and the need for focusing movements, which can affect measurement precision and require significant metrological effort.
Innovation Solution
A device and method that determine the focus position of a laser beam by scanning measurement markings on a reference area, capturing measurement signals, and establishing time values of signal edges to calculate the focus position without requiring focusing movements, using photoactive, reflecting, or absorbing designs for measurement markings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If confocal detection with variable focus adjustment is used to determine surfaces, then surface position can be determined, but focusing movements are required which adversely affect measurement accuracy and require significant metrological effort
Solution Approach 1:
The patent replaces the mechanical focusing adjustment system with an optical measurement approach. Instead of moving the focus to find surfaces, the system uses a laser beam to scan measurement markings on the surface and determines position from the temporal pattern of the detected signal, eliminating the need for mechanical focus adjustment and reducing metrological complexity
Solution Approach 2:
The patent introduces measurement markings as an intermediary element on the surface. These markings serve as reference features that modulate the laser signal when scanned, allowing surface position to be determined indirectly through signal analysis rather than direct focal point detection
2Measurement precision
If confocal detection is used to determine entry and exit surfaces, then surface positions can be found, but very weak signals are obtained requiring much metrological effort
Solution Approach 1:
The patent uses measurement markings with different optical properties (reflecting, absorbing, or photoactive designs) that create strong, distinguishable signal modulations when scanned by the laser beam. These markings effectively 'color-code' different surface regions, producing strong detectable signals rather than weak confocal reflections
3Measurement precision
If focusing movements are performed during measurement, then focus position can be determined, but measurement accuracy is adversely affected
Solution Approach 1:
The patent performs preliminary scanning of measurement markings at a fixed focus position to determine the focus offset. By establishing reference signal patterns from the markings before treatment, the system can calculate focus position without requiring additional focusing movements during the actual measurement or treatment process
Solution Approach 2:
The patent replaces mechanical focusing movements with optical signal analysis. The focus position is determined by analyzing the temporal characteristics of the laser signal as it scans the measurement markings, eliminating the need for mechanical focus adjustment and improving measurement reliability
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 allows for precise determination of the focus position without focusing movements, improving measurement accuracy and reducing metrological effort, even in cases of variable scanning speed, and provides a more efficient method for centering and beam width determination.
Implementation Method 1
the measurement marking has a photoactive design and the measurement marking creates the measurement signal when the laser beam passes over the measurement marking
Implementation Method 2
the measurement marking has a reflecting design and the measurement signal is created as a result of a laser beam which is reflected when the measurement marking is passed over
Implementation Method 3
the measurement marking has an absorbing design and the measurement signal is created as a result of a laser beam which is absorbed or not reflected or not transmitted when the measurement marking is passed over
Data Source
AI summary
In order to determine the focus position of a laser beam (60, 60a) in an ophthalmological laser projection system (1), at least one measurement marking (3) applied to a reference area (20) is passed over by means of the laser beam (60, 60a) along a scanning path. A measurement signal created by passing over the measurement marking (3) is captured. Time values from at least one signal edge created in the measurement signal when passing over edges of the measurement marking (3) are determined and the focus position is established on the basis of the time values. By scanning defined measurement markings (3) and establishing time values of signal edges created when edges of the measurement marking (3) are passed over, it is possible to determine the focus position of the laser beam (60, 60a) without focusing movements being required for this during the measurement.