Dental 3D Camera Using Oscillating Sensor for Depth Measurement
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Solution Overview
Problem
Existing methods for three-dimensional measurement of dental objects using time-varying projection patterns with mechanically driven projection means are prone to positioning errors and require significant space, leading to faulty image data and an increased camera size.
Innovation Solution
A camera design that uses focusing optics to adjust the focal distance step-by-step between fixed scan positions, with a sensor moving oscillatingly to record intensity changes, allowing for error-free and compact three-dimensional measurement by determining contrast and sharpness differences between images taken at varying focus positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanically driven projection gratings are used to generate time-varying projection patterns, then three-dimensional measurement can be performed, but positioning errors occur leading to inaccurate measurement data
Solution Approach 1:
The patent replaces the mechanically driven projection grating with a digital light projector (LCD-based) that generates projection patterns electronically. This substitution eliminates mechanical moving parts, drive mechanisms, and associated positioning errors, thereby improving measurement accuracy and control reliability while maintaining the capability to generate time-varying projection patterns.
2Measurement precision
If mechanically driven projection gratings are used, then three-dimensional measurement is enabled, but the camera size increases due to installation space requirements
Solution Approach 1:
By replacing the mechanical projection grating system with a digital light projector, the patent eliminates the need for large mechanical components, drive mechanisms, and associated installation space. This allows the camera to achieve three-dimensional measurement capability in a more compact form factor.
Solution Approach 2:
The patent changes the operational mode from mechanical movement to electronic control, allowing the projection pattern to be varied through digital signals rather than physical displacement. This parameter change enables compact design while maintaining measurement functionality.
3Measurement precision
If the sensor moves oscillatingly between multiple positions, then depth information can be extracted through focus variation, but the device complexity increases
Solution Approach 1:
The patent introduces a focusing optic as an intermediary element that creates a movable focal plane without requiring physical movement of the sensor or projection system. By adjusting the focal distance of the focusing optic, the system achieves focus variation for depth measurement while keeping the sensor and projector stationary, thereby reducing mechanical complexity.
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 and error-free three-dimensional measurement of dental objects with a compact camera design, capable of simultaneous three-dimensional and color measurement, using a deph-from-defocus method to calculate depth data from intensity profiles.
Implementation Method 1
a focusing optic that maps the projection pattern in a sharp plane at a defined focal distance relative to the dental camera, wherein the projection pattern projected onto the object is reflected back from the object as an observation beam and is recorded by means of a sensor
Implementation Method 2
The sensor is moved oscillating back and forth laterally to the beam path of the observation beam, with the first image being captured in a first sensor position and the second image being captured in a second sensor position
Data Source
Figure 1
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Figure 4~6
AI summary
The invention relates to a method and to a camera (1) for the three-dimensional measurement of a dental object (2), comprising at least one light source (4), which emits an illumination beam (5), at least one projection means (9), which produces a projection pattern (30, 40), a focusing optical unit (6), which images the projection pattern (30, 40) in a sharp plane (7) at a defined focal distance (8) in relation to the dental camera (1), wherein the projection pattern (30, 40) projected onto the object (2) is reflected by the object (2) as an observation beam (10) and is recorded by means of a sensor (11). In the measurement of the object (2), the focusing optical unit (6) is controlled in such a way that the focal distance (8) of the sharp plane (7) in relation to the camera (1) is changed incrementally between a plurality of defined scanning positions (12, 13, 14, 54), wherein a first recording (35) and at least a second recording (36) are performed by means of the sensor (11) for each scanning position (12, 13, 14, 54), wherein the sensor (11) or the projection means (9) is moved back and forth in an oscillating manner laterally to the beam path of the observation beam, wherein the first recording (35) is recorded in a first sensor position (18) of the sensor (11) and the second recording (36) is recorded in a second sensor position (19) of the sensor (11), and wherein during the oscillating motion the sensor (11) is moved by a distance (20) between the first sensor position (18) and the second sensor position (19) along a first sensor axis parallel to the rows of the sensor pixels or along a second sensor axis parallel to the columns of the sensor pixels, which distance corresponds to the width of a pixel (33, 34) of the sensor (11), or wherein the first recording (35) is recorded in a first position of the projection means (9) and the second recording (36) is recorded in a second position of the projection means (9), wherein during the oscillating motion the projection means (9) is moved by a distance (20), which is dimensioned in such a way that the projection pattern (30, 40) is moved in the plane (7) of the sensor (11) by the width of a pixel (33, 34) of the sensor (11) along a first sensor axis parallel to the rows or along a second sensor axis parallel to the columns.