Non-Confocal Z Position Detection for Ophthalmic Laser Patient Interfaces
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Solution Overview
Problem
Conventional ophthalmic laser systems require complex confocal detection configurations for Z position calibration, which are cumbersome and prone to alignment issues.
Innovation Solution
An ophthalmic laser system utilizing a non-confocal detection configuration with a high numerical aperture objective lens and a light intensity detector without a pinhole or confocal lens, allowing for simpler Z direction calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a confocal detection configuration is used for Z position calibration, then measurement precision is improved, but device complexity increases and alignment difficulty increases
Solution Approach 1:
The patent removes the confocal lens and pinhole from the detection system, extracting only the essential light intensity detection function. This simplifies the device structure while maintaining the ability to detect Z position through back-reflected light intensity variations, directly resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The system uses the back-reflected light from the patient interface optical element itself as the detection target, eliminating the need for separate confocal components. The optical element's own reflective properties are exploited to provide calibration information, reducing system complexity while maintaining detection capability.
2Measurement precision
If a confocal detection configuration is used for Z position calibration, then measurement precision is improved, but ease of operation deteriorates due to alignment requirements
Solution Approach 1:
By removing the confocal lens and pinhole components, the patent eliminates the precise alignment requirements between these elements. The simplified detector only needs to receive back-reflected light, which occurs naturally at the objective lens axis, dramatically improving ease of operation while maintaining sub-micron depth resolution through light intensity analysis.
3Device complexity
If a non-confocal detection configuration is used, then device complexity is reduced and ease of operation is improved, but measurement precision may deteriorate
Solution Approach 1:
The patent changes the detection parameter from spatial filtering (confocal pinhole) to light intensity measurement. By monitoring the intensity of back-reflected light as the objective lens moves in Z, the system achieves sub-micron depth resolution through parameter analysis rather than spatial filtering, maintaining precision while reducing complexity.
Solution Approach 2:
The system combines the high numerical aperture objective lens with a simple light intensity detector to achieve performance comparable to complex confocal systems. The high NA lens provides strong light collection and precise focal control, compensating for the absence of confocal components and maintaining measurement precision.
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
The system achieves sub-micron depth resolution in Z position detection and eliminates the need for precise alignment of confocal components, resulting in a more robust and efficient calibration process.
Implementation Method 1
an objective lens configured to focus the parallel light beam to a focus point
Implementation Method 2
a light intensity detector... configured to detect a light beam that has been reflected back by the optical surface of the patient interface optical element and has passed through the objective lens
Data Source
AI summary
An ophthalmic laser system uses a non-confocal configuration to determine a laser beam focus position relative to the patient interface (PI) surface. The system includes a light intensity detector with no confocal lens or pinhole between the detector and the objective lens. When the objective focuses the light to a target focus point inside the PI lens at a particular offset from its distal surface, the light signal at the detector peaks. The offset value is determined by fixed system parameters, and can also be empirically determined by directly measuring the PI lens surface by observing the effect of plasma formation at the glass surface. During ophthalmic procedures, the laser focus is first scanned insider the PI lens, and the target focus point location is determined from the peak of the detector signal. The known offset value is then added to obtain the location of the PI lens surface.