Optically Active Surface Topography Measurement with Point Lights
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Solution Overview
Problem
Existing methods for measuring the topography, gradients, and curvature of optically effective surfaces, such as spectacle lenses, suffer from inaccuracies and inefficiencies, particularly in achieving precise local measurements with small errors and high accuracy.
Innovation Solution
The use of point light sources with a small solid angle, combined with iterative algorithms and remote computing, allows for precise measurement and calibration of optically effective surfaces, utilizing a camera with a linearly movable image sensor and incorporating external ray tracing programs to enhance measurement accuracy and reduce computational time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used, then the measurement process is simple, but the measurement precision is insufficient and errors are large
Solution Approach 1:
The measurement system is segmented into multiple independent point light sources arranged on a spherical surface, with each light source providing illumination for a specific region. This segmentation allows precise local measurement of topography and curvature by analyzing reflections from individual light sources, thereby improving measurement precision without requiring a single complex measurement system
Solution Approach 2:
A camera system acts as an intermediary to capture reflections from the point light sources off the optically effective surface. The camera records the positions and intensities of reflected light, which are then processed through algorithms to determine surface topography, gradients, and curvature, achieving high precision measurement through the intermediary capture and processing system
2Measurement precision
If iterative algorithms with remote computing are used, then measurement accuracy increases, but computational time increases
Solution Approach 1:
The system performs preliminary calibration by measuring a calibration object with known geometry before actual measurements. This preliminary action establishes reference data and system parameters that are used during subsequent measurements, reducing the computational burden and time required for iterative algorithms during actual topography measurement
Solution Approach 2:
The patent uses a calibration object with known geometry as a copy or reference model. By measuring this known reference and comparing it with actual unknown surfaces, the system can efficiently perform iterative algorithms to determine accurate topography, gradients, and curvature without requiring extensive computational time for each measurement
3Measurement precision
If point light sources with small solid angle are used, then measurement precision improves, but the illumination coverage decreases
Solution Approach 1:
Instead of using a single light source, the system segments the illumination into multiple point light sources distributed across the spherical surface. Each light source provides precise local illumination for its specific region, and collectively they cover the entire surface area, achieving both high precision and comprehensive coverage
Solution Approach 2:
The system transitions from a single-point illumination approach to a distributed array of point light sources on a spherical surface. This dimensional change from one to many light sources in three-dimensional space allows simultaneous achievement of small solid angle precision and broad area coverage through spatial distribution
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 accurate measurement of refractive power and topography of aspherical lenses within seconds, with an accuracy of at least 102 dpt, and supports the measurement of concave and convex free-form surfaces with reduced computational times.
Implementation Method 1
capturing a brightness distribution (79) composed of luminous spots (57), the brightness distribution being caused by the light of one or more point light sources (20) that is reflected at the surface (18) to be measured
Data Source
AI summary
A method and a device for measuring the topography and/or the gradients and/or the curvature of an optically active surface of an object are disclosed. The device allows the object to be arranged in a receiving region with a contact surface for contact with the object. Inside the device, there is a plurality of point light sources that provide light that is reflected at the surface to be measured of an object arranged in the receiving region. The device includes at least one camera with an objective assembly and an image sensor for detecting a brightness distribution which is produced on a light sensor by the light of the point light sources reflected at the surface to be measured.