Cylindrical Optical Element Index Profiling with Multi-Wavelength Detection
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Solution Overview
Problem
Existing methods for determining the refractive index profile of cylindrical optical objects with periodic layers face challenges due to microscopic refractive index fluctuations, which cause diffraction blur and make it difficult to distinguish zero-order from higher-order beams, often requiring prior knowledge of the object's structure and complex data processing.
Innovation Solution
The method involves scanning the object with at least two light beams of different wavelengths, mathematically processing spatially identical intensities to identify and eliminate higher-order beam intensities, using a line sensor and mathematical operations like multiplication and addition to enhance accuracy, and applying an intensity threshold to refine the detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single wavelength light beam is used for scanning, then the measurement process is simple, but higher-order beam intensities cannot be eliminated and interfere with zero-order beam detection
Solution Approach 1:
The patent changes the wavelength parameter of the light beam by performing scans at multiple wavelengths (e.g., 635nm, 840nm, 970nm, 1040nm, 1550nm). This allows the system to capture intensity distributions at different wavelengths and eliminate higher-order beam intensities through mathematical processing, thereby improving zero-order beam detection accuracy while maintaining operational simplicity through automated multi-wavelength scanning.
2Measurement precision
If multiple wavelengths are used to eliminate higher-order beams, then detection accuracy improves, but the device complexity and data processing requirements increase
Solution Approach 1:
The system uses the measured intensity distributions themselves to eliminate higher-order beam effects. By capturing intensity data at multiple wavelengths and applying mathematical processing (multiplication, addition, or subtraction of normalized intensities), the system self-corrects for diffraction effects without requiring external calibration or complex optical filtering components.
Solution Approach 2:
The patent employs a universal mathematical processing approach that can eliminate higher-order beam intensities regardless of the specific number or wavelengths of light sources used. The same mathematical operations (normalization, multiplication, addition, or subtraction) apply across different wavelength combinations, making the system adaptable and reducing the need for wavelength-specific calibration procedures.
3Ease of operation
If prior knowledge of object structure is used to identify zero-order beams, then beam identification is easier, but the method loses versatility for unknown structures
Solution Approach 1:
The patent uses wavelength as a discriminating parameter to identify zero-order beams without requiring prior structural knowledge. Since higher-order diffraction angles are wavelength-dependent while zero-order beams maintain consistent angular positions across wavelengths, the system can automatically identify zero-order beams by comparing intensity distributions at multiple wavelengths, enabling universal application to unknown structures.
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 refractive index profile without prior knowledge of the object's structure, simplifying the process and improving detection accuracy by clearly distinguishing zero-order beams from higher-order beams.
Implementation Method 1
a focused optical beam is scanned transversely to the cylindrical longitudinal axis of the optical object to be measured... and the deflection angle of the refracted light beam emerging from the object is measured
Implementation Method 2
The layers act as a transparent diffraction grating, where the light beam penetrating the object is further diffracted... leading to diffraction blur due to different deflection angles and exit points
Data Source
Figure 1~2
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AI summary
The invention relates to a method for determining an index-of-refraction profile of an optical object (22), which has a cylindrical surface (26) and a cylinder longitudinal axis (25), said method comprising the following method steps: (a) scanning the cylindrical surface (26) of the object (22) at a plurality of scanning locations (23) by means of optical beams (21) which are incident perpendicularly to the cylinder longitudinal axis (25); (b) capturing, by means of an optical detector (7; 8), a location-dependent intensity distribution of the optical beams (21) deflected in the optical object (22); (c) determining the angles of deflection of the zero-order beams for each scanning location (23) from the captured intensity distribution, comprising eliminating beam intensities of higher-order beams from the intensity distribution so that an angle-of-deflection distribution is obtained for the zero-order beams, and (d) calculating the index-of-refraction profile of the object (22) on the basis of the angle-of-deflection distribution, wherein method steps (a) and (b) are carried out with light beams having at least two different wavelengths and, in order to eliminate beam intensities of higher-order beams, same-location intensities of the intensity distributions for the different wavelengths are mathematically processed with each other, more particularly multiplied by and/or added to each other.