3D Contour Detection for Semi-Transparent Objects Using Modulated Illumination
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Solution Overview
Problem
Existing methods for acquiring contour data of semi-transparent objects, such as dental objects, face challenges with high background signal levels and insufficient signal-to-noise ratios, particularly in full-field illumination and multipoint illumination techniques.
Innovation Solution
The method employs offset grids of illumination points from multiple illuminations projected onto a sensor, where the distance between pixels is smaller than the distance between illumination points, with intensity and frequency modulation of radiation, and phase-selective detection to evaluate differences in neighboring pixel signals, using collinear or angled illumination sources to determine contour data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If full-field illumination is used to illuminate the semi-transparent object, then the illumination coverage is improved, but the background signal level increases due to scattering and the illumination intensity requirement increases
Solution Approach 1:
The patent segments the full-field illumination into multiple discrete illumination points arranged in a grid pattern. Instead of illuminating the entire field uniformly, the object is illuminated at specific discrete points, which reduces the overall scattering and background signal while maintaining adequate coverage through the distributed arrangement of illumination points across the measurement area.
2Illumination intensity
If multipoint illumination is used to reduce illumination intensity requirements, then the illumination intensity is reduced, but the signal-to-noise ratio becomes insufficient and sensitivity to ambient light decreases
Solution Approach 1:
The patent combines multiple multipoint illumination patterns from different illumination sources into a coherent measurement system. By using multiple offset grids and combining their signals through correlation processing, the system achieves both reduced illumination intensity requirements and improved signal-to-noise ratio, as the combined signal provides better statistical reliability while maintaining low intensity per source.
Solution Approach 2:
The patent employs periodic modulation of the illumination sources at different frequencies. This allows the system to use low-intensity periodic illumination while achieving high measurement precision through frequency-selective detection. The periodic action enables differentiation of the modulated signal from ambient light and noise, improving the signal-to-noise ratio without requiring high continuous illumination intensity.
3Measurement precision
If offset grids of illumination points from multiple illuminations are used with modulation, then the signal-to-noise ratio is improved and background signals are reduced, but the device complexity increases
Solution Approach 1:
The patent implements a multi-functional optical system where the same optical components (beam expanders, microlens arrays, beam splitters) serve multiple purposes: generating illumination patterns, directing light paths, and enabling both measurement and reference beam functions. This universal use of components reduces overall device complexity despite the sophisticated measurement technique, as fewer specialized components are needed compared to having separate systems for each function.
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 enhances the signal-to-noise ratio and reduces background signals, allowing for accurate recording of contour data with improved sensitivity and reduced crosstalk between illumination points.
Implementation Method 1
the radiation from the illumination points of the multipoint illuminations being modulated in terms of their intensities and a frequency- and/or phase-selective detection of the first and second illumination points
Implementation Method 2
optical device, preferably for confocal or OCT or depth of focus - beam paths
Implementation Method 3
an interference and/or autocorrelation measurement is used, a reference beam being split off from the bundle of rays in a beam splitter
Implementation Method 4
Radiation reflected from the dental area is received by a detector comprising an array of sensing elements for measuring the intensity of each of a plurality of imaging light rays returning from the spots
Data Source
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AI summary
The invention relates to a method for detecting contour data of a three-dimensional object, wherein a grid of illumination points of a multi-point illumination is projected onto the object using an optical device and these illumination points are then projected back onto a sensor comprising pixels. In order to achieve an improvement of the signal-noise ratio and to reduce the background signal, it is proposed that a grid of illumination points of at least two multi-point illuminations are projected onto the object, that the beams of the illuminating points of the multi-point illuminations are modulated in intensity and that a frequency-selective and/or phase-selective detection is performed of mutually associated first and second illumination points back-projected onto the sensor, wherein the first illumination points derive from a first of the at least two multipoint illuminations and the second illumination points derive from a second of the at least two multipoint illuminations and wherein differences in intensity and/or frequency of the measurement signals of adjacent pixels of the sensor on which the mutually associated first and second image points are depicted are evaluated for the purposes of determining the contour data.