Semi-Transparent Object Contour Detection with Spatially Segmented Light
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Solution Overview
Problem
Existing methods for recording contour data and optical properties of semi-transparent objects, such as teeth, face limitations in resolution and are affected by scattered radiation, requiring additional operations that can irritate patients and restrict precise surface and depth information capture.
Innovation Solution
A method using a bundle of rays divided into spatially distanced parallel individual light rays, with a beam shifter to adjust the rays' spacing and a combination of laser diodes with offset central wavelengths to enhance resolution and reduce scattered radiation interference, allowing for precise contour recording and differential measurements across varying wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a broad band spatially partially coherent light source is used for interferometric measurement, then the measurement can be performed on semi-transparent objects, but the resolution in the z direction (depth resolution) is restricted
Solution Approach 1:
The patent divides the broad band light source into multiple discrete wavelength components using a diffraction grating. Each wavelength component interferes separately to produce autocorrelation signals at different depth positions, thereby achieving high depth resolution without requiring a complex short-coherence-length light source setup
Solution Approach 2:
The patent transforms the problem from temporal coherence domain to spectral domain by using a diffraction grating to separate wavelengths spatially. This allows depth information to be extracted from the spectral distribution rather than from temporal coherence properties, improving depth resolution
2Measurement precision
If white light interferometry is used to measure surface contours, then even optically raw objects can be measured, but the scattered radiation from the depth of semi-transparent objects disturbs the measurement
Solution Approach 1:
The patent separates the light into discrete wavelength components that can be independently detected. By analyzing autocorrelation signals for each wavelength separately, the system can distinguish between surface-reflected light and scattered radiation from deeper layers, filtering out the harmful scattered radiation
Solution Approach 2:
The patent introduces an autocorrelation analysis as an intermediary processing step between light detection and surface measurement. This mathematical operation enhances the surface signal while suppressing scattered radiation, acting as a filter against the harmful interference
3Manufacturing precision
If the bundle of rays is focused through a focusing optical system, then the spatial resolution is improved, but the scattered radiation from the object depth still affects the contour recording
Solution Approach 1:
The patent combines spatial segmentation through focusing optics with spectral segmentation through a diffraction grating. This dual segmentation allows the system to maintain high spatial resolution while separately analyzing different wavelength components to reject scattered radiation signals
Solution Approach 2:
The patent applies different optical treatments to different spatial regions: the focusing optical system provides high spatial resolution for the direct reflected beam, while the autocorrelation analysis provides scattering rejection for signals from different depths, creating locally optimized measurement quality
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 precise recording of both surface and depth information with improved resolution and reduced scattered radiation influence, facilitating accurate contour data capture for semi-transparent objects like teeth, including flexible tissues like mucosa, and supports caries diagnosis in the near-infrared range.
Implementation Method 1
the bundle of rays is divided before impingement upon the beam splitter into spatially distanced parallel individual light rays
Implementation Method 2
the bundle of rays is passed through a beam splitter and is preferably guided to the object through a focusing optical system; a reference beam is split off in the beam splitter
Implementation Method 3
guided to the object through a focusing optical system
Implementation Method 4
a reference beam is split off in the beam splitter and is reflected by a reference mirror movable along the reference beam
Implementation Method 5
the beam reflected from the object and from the reference mirror are brought together in the beam splitter and transferred into an image sensor having pixels, whereby temporally and/or spatially altered signal patterns can be recorded
Implementation Method 6
a combination of laser diodes with offset central wavelengths to enhance resolution and reduce scattered radiation interference
Data Source
AI summary
A method and device for detecting the contour data and/or optical characteristics of an object, such as a tooth or a tooth restoration, based on an interference and/or autocorrelation measurement using an image sensor. To permit an exact surface detection in addition to a determination of the optical characteristics of the object, individual light beams strike the object, which are located at a distance from one another in such a way that no impact of reflected individual light beams takes place on immediately adjacent pixels of the image sensor.