Facet Lens Temperature Compensation for Eye Topography
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Solution Overview
Problem
The temperature dependence of plastic facet lenses used in eye topography measurement systems causes inaccuracies, limiting their practical use to a narrow temperature range of 20±5°C, making them impractical for actual applications.
Innovation Solution
Incorporating temperature sensors to determine the facet lens temperature and storing the temperature-dependent emission angles in a control and evaluation unit, which adjusts the image recording evaluations accordingly, allowing for temperature-independent topography measurement across a broader range (10°C to 40°C).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the facet lens is manufactured from plastic, then the ease of manufacture is improved, but the temperature stability deteriorates causing beam angle changes
Solution Approach 1:
The patent applies parameter changes by detecting temperature variations and dynamically adjusting evaluation parameters (beam angles, normal vectors) to compensate for thermal effects on the plastic facet lens, maintaining measurement accuracy across different temperatures
Solution Approach 2:
The patent implements feedback by using temperature sensors to continuously monitor the facet lens temperature and using this information to dynamically adjust the evaluation of beam angles and normal vectors, compensating for temperature-induced changes in real-time
2Adaptability or versatility
If the temperature range is extended, then the adaptability is improved, but the measurement precision deteriorates due to temperature-dependent beam angle changes
Solution Approach 1:
The patent changes evaluation parameters (beam angles, normal vectors) based on detected temperature to maintain measurement precision across an extended temperature range from 10°C to 40°C, allowing the system to adapt to different environmental conditions without sacrificing accuracy
3Measurement precision
If temperature compensation is implemented, then the measurement precision is improved, but the device complexity increases due to additional temperature sensors and processing
Solution Approach 1:
The patent introduces temperature sensors as intermediary elements that detect thermal conditions and provide data to the control unit, which then adjusts evaluation parameters accordingly, serving as a mediator between the physical temperature environment and the measurement evaluation process
Solution Approach 2:
The patent changes evaluation parameters (beam angles, normal vectors) based on detected temperature to maintain measurement precision, using software-based parameter adjustment rather than complex hardware modifications to keep the system relatively simple
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
Enables accurate and reliable eye topography measurement over a wide temperature range without the need for active temperature control or using temperature-stable materials, ensuring the system's usability in various environments.
Implementation Method 1
temperature sensors additionally being present for determining the temperature of the facet lens
Implementation Method 2
the temperature-dependent change in the angles of the beams emerges from the change in the optical power of the facet lens as a result of a change in the geometry and/or the refractive index of the plastic
Data Source
AI summary
A device and method of compensating for the temperature dependence of a facet lens used for determining the topography of an eye. According to the invention, temperature sensors are present for determining the temperature of the facet lens. In addition, the temperature dependence of the beam angles of the beam bundles is stored in a control and evaluation unit, which, in addition to the temperature of the facet lens transmitted by the temperature sensors, are taken into account by the control and evaluation unit when evaluating the recordings of the image recording unit. The device and method are described in the context of facet lenses that are used to determine the topography of an eye. However, in principle, they are usable wherever an existing temperature dependence, in particular of optical components, should be compensated for.