3D Measurement of Semi-Transparent Objects Using Chromatic Confocal Light Guides
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for three-dimensional measurement of semi-transparent objects like teeth face challenges due to strong volume scattering, leading to reduced resolution and the need for complex, compact devices with fixed microlens and pinhole patterns that compromise measurement point distribution and spectrum distribution.
Innovation Solution
A measuring arrangement using a broadband light source, light guides, a lens with large chromatic aberration, and a color measurement unit that allows for independent measurement and evaluation point distributions, enabling high-precision measurements with a compact, easily handled device by separating the illumination and detection paths and using unilluminated light guides for background measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed microlens and pinhole pattern is used, then the device structure is simplified, but the measurement point distribution and spectrum distribution are compromised
Solution Approach 1:
The patent segments the measurement function by separating the illumination path (microlens array) from the detection path (pinhole array), allowing each to be independently optimized. The light guides are arranged in a grid pattern on the object side while the detection pins are arranged to match the desired measurement point distribution on the detector side, eliminating the need for a fixed coupled microlens-pinhole pattern.
2Measurement precision
If light guides are illuminated for measurement, then measurement data is obtained, but stray light and background noise increase
Solution Approach 1:
The patent implements temporal multiplexing by alternately illuminating different subsets of light guides in a periodic sequence. At any given moment, only a portion of the light guides are active, which reduces the total stray light and background noise compared to having all light guides illuminated simultaneously, while still allowing complete measurement through accumulation of multiple frames.
3Area of stationary object
If all light guides are used for measurement, then measurement coverage is maximized, but background measurement capability is lost
Solution Approach 1:
The patent divides the light guide array into multiple independently controllable groups or subsets. By selectively illuminating different subsets in different time periods, the system can perform background measurements (by illuminating non-measurement subsets) while maintaining full measurement coverage capability through the combined data from all subsets across multiple measurement cycles.
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 solution allows for high-precision, three-dimensional shape measurement of semi-transparent objects with optimal measurement point and spectrum distribution, simplifying evaluation and enabling efficient stray light suppression, while maintaining a compact and user-friendly device design.
Implementation Method 1
suitable optics with a focal length that is strongly dependent on the wavelength are used to image the focus or foci of a broadband light source
Implementation Method 2
the multifocal illumination pattern is generated via light guides arranged between the light source and the lens
Implementation Method 3
a spectrally dispersive device on which the light reflected from the object can be imaged via the lens
Data Source
Figure 1~2b
AI summary
Method for measuring the shape of at least one section of an object (8), in particular a semi-transparent object such as at least one section of a tooth, using a light source (1) for generating light with preferably a broadband spectrum in a device (3) for generating a multifocal illumination pattern, a lens (6) with a large chromatic aberration for imaging foci of the illumination pattern onto the object, and a detection device (12) for determining the wavelength spectra of the foci confocally imaged onto the object via the lens, wherein a spectral peak position of each focus is determined from the respective wavelength spectrum, from which position the extent of the object in the direction of the imaging beam (Z coordinate) is calculated, wherein the multifocal illumination pattern is formed via optical waveguides (5) arranged between the light source (1) and the lens (6) with a large chromatic aberration, wherein the lens (6) images object-side ends of the optical waveguides onto the object and images light remitted by the object onto the object-side ends of the optical waveguides, and wherein light guided and remitted by the optical waveguides is guided to the detection device (12). In order to make it possible to carry out highly accurate measurements with structurally simple measures, wherein the intention is to enable both the best possible distribution of measuring points on the sample and optimum spectrum distribution in the detection device, provision is made for the object-side illumination pattern to be formed via the optical waveguides (5) in such a manner that an object-side distribution of measuring points is independent of an illumination-side and detection-side microlens or pinhole distribution.