3D Scanner Varifocal Unit Calibration via Reference Light Path
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Solution Overview
Problem
Existing three-dimensional scanners face challenges in accurately grasping the conditions of varifocal units, particularly liquid lenses with hysteresis characteristics, which affect the precision of focal position determination, essential for obtaining accurate three-dimensional shapes, especially in dental applications where high measurement accuracy is required.
Innovation Solution
A three-dimensional scanner that includes a reference unit within its optical system to determine the condition of the varifocal unit by analyzing light reflected from both the object and a reference unit, allowing for precise calibration and accurate shape determination without the need for additional gauges or increased device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a liquid lens is used for a varifocal unit, then the device size can be reduced and operation simplified, but it becomes difficult to correctly grasp the focal position due to hysteresis characteristics
Solution Approach 1:
The patent implements a feedback mechanism where the imaging unit captures images of the reference object at different focal positions, and the control unit analyzes these images to determine the actual focal position. This feedback loop allows the system to compensate for hysteresis effects in the liquid lens by continuously monitoring and adjusting based on actual optical performance rather than relying solely on voltage control.
Solution Approach 2:
The patent introduces a reference object with a known pattern as an intermediary element. By imaging this reference object and analyzing its focal characteristics, the system can indirectly determine the focal position of the varifocal unit. This intermediary approach allows precise focal position measurement without requiring direct physical measurement of the liquid lens state.
2Measurement precision
If additional gauges or measurement devices are added to accurately determine focal position, then measurement precision improves, but device size and complexity increase
Solution Approach 1:
The imaging unit serves multiple functions: it captures images of the measurement object for three-dimensional scanning and simultaneously captures images of the reference object for focal position determination. This multi-functional approach eliminates the need for separate dedicated focal measurement devices, maintaining measurement precision while avoiding increased device complexity.
Solution Approach 2:
The system uses its own imaging unit and existing optical path to perform self-diagnosis and self-calibration by imaging the reference object. The control unit processes the reference object images to determine focal position and automatically adjusts the varifocal unit accordingly, making the system self-sufficient without requiring external measurement equipment.
3Productivity
If the focal position is not correctly grasped, then measurement speed may be maintained, but measurement accuracy deteriorates
Solution Approach 1:
The system performs preliminary action by capturing images of the reference object at multiple predetermined focal positions before actual measurement. This pre-characterization of the reference object's appearance at different focal positions creates a lookup reference that enables rapid focal position determination during measurement, maintaining high measurement speed while ensuring accuracy.
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 accurate determination of varifocal unit conditions, ensuring precise three-dimensional shape acquisition and reducing the size of the scanner while maintaining high measurement accuracy, even with liquid lenses, by using a reference unit to correct for hysteresis and other environmental factors.
Implementation Method 1
light source unit for emitting light; varifocal unit through which light from the light source unit passes at least once
Implementation Method 2
optical sensor for detecting the light from the light source unit that has been reflected on the object body
Implementation Method 3
varifocal unit capable of changing the focal position, varifocal unit being a unit through which both of the light from the light source unit to the optical sensor via the object body and the light from the light source unit to the optical sensor via the reference unit travel at least once
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
The present invention provides a three-dimensional scanner capable of correctly grasping conditions of a varifocal unit and obtaining an accurate three-dimensional shape, and a probe. The present invention is a three-dimensional scanner for obtaining shape information of an object body. The three-dimensional scanner includes a light source unit (81), a varifocal unit (82), a reference unit (83), a light path length adjustment unit (84), an optical sensor (85), and a control unit. Varifocal unit (82) is able to change a focal position, and both of light from light source unit (81) to optical sensor (85) via an object body (200) and light from light source unit (81) to optical sensor (85) via reference unit (83) travel at least once. The control unit determines a condition of varifocal unit (82) based on light has been reflected on reference unit (83) and detected by a part of optical sensor (85), and calculates the shape information of object body (200) from light detected by optical sensor (85) using information of the condition of varifocal unit (82) that has been determined.