Transverse Thermal Lens Measurement for Optical Elements
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Solution Overview
Problem
Existing methods for determining the working area of heat-generating radiation penetrating an optical element are hindered by heat-related optical property changes, which cause inhomogeneous temperature and refractive index distributions, leading to significant focal length shifts and lens effects, especially in materials like glass lenses and laser crystals.
Innovation Solution
The method involves directing heat-generating radiation through the optical element in a first direction and using measuring radiation in a second, transverse direction to determine the calibration variable focus position shift and beam path change, allowing for precise determination of the working range by intersecting the measurement radiation with the focus of the heating radiation, thereby measuring the thermal lens without disrupting the working radiation path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If measuring radiation is directed through the optical element in the same direction as heat-generating radiation, then the thermal lens effect can be measured, but the measurement device interferes with the working radiation path and requires additional components
Solution Approach 1:
The patent transitions the measurement from the longitudinal direction (same as heat-generating radiation) to the transverse direction (perpendicular to heat-generating radiation). This dimensional change allows the measuring radiation to intersect the thermal lens effect without traveling through the optical element in the working beam path direction, thereby eliminating the need for beam splitters or mirrors in the working radiation path.
Solution Approach 2:
The patent introduces a transverse measuring radiation as an intermediary method to detect the thermal lens effect. Instead of directly measuring along the working beam path, the measuring radiation passes through the optical element perpendicularly, using the thermal lens characteristics (refractive index changes) as an intermediary indicator to infer the thermal lens effect without interfering with the working radiation.
2Measurement precision
If beam splitters or mirrors are used to introduce measuring radiation into the working beam path, then thermal lens measurement is possible, but the working radiation path is disrupted and system complexity increases
Solution Approach 1:
The patent extracts the measurement function from the working beam path by using transverse measuring radiation. The measurement of thermal lens effects is separated from the longitudinal working radiation path, allowing the working radiation to pass through the optical element undisturbed while the measuring radiation independently probes the thermal lens characteristics from a perpendicular direction.
3Reliability
If the measuring device is placed in the path of working radiation, then thermal lens can be measured, but the working area determination is hindered by additional components
Solution Approach 1:
The patent uses transverse measuring radiation to measure the thermal lens effect from a direction perpendicular to the working radiation path. This allows the measurement device to be positioned without interfering with the working beam path, enabling accurate working area determination by separately measuring the focal position shift caused by thermal lensing without adding components to the working radiation path.
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 enables precise determination of the working area, allowing for reproducible use of laser radiation in applications like welding and soldering, and can measure thermal lenses in operational optical elements without coupling measurement radiation into or out of the working beam path, facilitating in-situ measurements during processes like welding or soldering.
Implementation Method 1
heat-generating radiation that penetrates an optical element upstream of the working area
Implementation Method 2
With conventional glass lenses, the thermal lens is noticeable by shifting the focal point in the direction of the lens
Implementation Method 3
a beam deflection of the measurement radiation which passes through the optical element is determined
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The method involves implementing an optical element in a direction from a heat generating radiation and implementing in another direction (18) for the determination of the characteristic changes of the optical element from a measuring radiation (16). The measuring radiation is aligned to the optical element in such a way that the latter direction runs transverse to the former direction. An independent claim is included for an arrangement for determination of thermal-conditioned characteristic change of an optical element.