3D Scanner Aperture and Tilted Bandpass Filter for Distance Accuracy
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Solution Overview
Problem
Existing 3D scanners face issues with unwanted reflections from reference reflectors causing errors in measured distances and bright background light leading to inaccuracies in 3D coordinates.
Innovation Solution
The implementation of a 3D aperture structure and a tilted optical bandpass filter to block unwanted reflections and minimize cavity reflections, enhancing distance accuracy by reducing spurious signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a narrow passband filter is placed in front of the optical detector to block bright background light, then the scanner can operate in sunlight or bright background conditions, but reflections from the bandpass filter and optical detector surface act as an etalon causing multiple reflections that increase average light travel distance and create measurement errors
Solution Approach 1:
The patent introduces a spatial dimension solution by tilting the bandpass filter at a specific angle (e.g., 45 degrees) relative to the optical axis. This angular orientation creates different optical paths for reflected light, directing etalon reflections away from the detector active area. The tilt transforms the problem from a one-dimensional optical path issue into a three-dimensional spatial arrangement where reflected beams are geometrically separated from the detection path.
Solution Approach 2:
The patent extracts and removes the harmful reflected light paths from the detection system. By tilting the filter, the unwanted etalon reflections are directed away from the detector, effectively taking them out of the measurement path. Additionally, the patent physically removes reflected light through aperture masking, where opaque structures block specific angular ranges of reflected light from reaching the detector.
2Reliability
If a reference reflector is used to measure reference distance for correcting common-mode errors, then accuracy under varying temperature and electrical conditions is improved, but unwanted signals from the reference reflector corrupt the reference distance measurement
Solution Approach 1:
The patent applies local quality by creating spatially differentiated optical paths for reference light and measurement light. The tilted filter and aperture structure are positioned to selectively transmit reference distance information while blocking spurious reflections from the reference reflector. This localized filtering approach allows the system to maintain reliable common-mode error correction by accepting only the desired reference signal components from specific angular directions.
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
Improves distance measurement accuracy by eliminating spurious reflections and cavity modes, thereby enhancing the precision of 3D coordinate determination.
Implementation Method 1
a filter having a narrow passband may be placed in front of the optical detector in the distance meter, permitting only the laser light to pass
Implementation Method 2
the optical bandpass filter is tilted so that light reflected by the active area is reflected by the optical bandpass filter away from the active area
Implementation Method 3
a 3D aperture structure having side walls and an aperture, the aperture sized to pass a first portion of the light reflected by the reference reflector, the side walls sized to block a second portion of the light reflected by the reference reflector
Implementation Method 4
A TOF laser scanner is a scanner in which the distance to a target point is determined based on the speed of light in air between the scanner and a target point
Data Source
AI summary
A three-dimensional (3D) scanner includes a light source, an optical detector, a reference reflector, and a 3D aperture structure having side walls and an aperture, the aperture sized to pass a first portion of the light reflected by the reference reflector, the side walls sized to block a second portion of the light reflected by the reference reflector. The 3D scanner further includes a tilted optical bandpass filter to block ambient background light without creating cavity reflections that might cause errors in measured distance.