3D Scanner Aperture and Tilted Filter for Reflection-Free Ranging
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Solution Overview
Problem
Existing 3D scanners face issues with unwanted reflections from reference reflectors causing errors in distance measurements, particularly in bright light conditions, and multiple reflections through optical detectors leading to inaccurate 3D coordinate determination.
Innovation Solution
Incorporation of a 3D aperture structure and a tilted optical bandpass filter to block unwanted reflections and minimize cavity reflections, ensuring accurate distance measurements 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 light conditions, but reflections from the bandpass filter and optical detector create an etalon effect causing multiple reflections and distance measurement errors
Solution Approach 1:
The patent extracts and removes the harmful reflected light paths by introducing a beam steering mechanism that directs unwanted reflections away from the optical detector. The system separates the useful returning laser light from the harmful etalon reflections, allowing the filter to block background light without creating measurement errors.
Solution Approach 2:
The patent introduces a beam steering mechanism as an intermediary element between the optical detector and the incoming light. This intermediary actively directs the light paths, steering useful signals to the detector while redirecting harmful reflections away, thus mediating between the filter's light blocking function and the detector's measurement function.
2Measurement precision
If a reference reflector is used to measure reference distance for correcting common-mode errors, then accuracy is improved, but unwanted signals from the reference reflector corrupt the measurement resulting in reduced accuracy
Solution Approach 1:
The patent extracts and removes unwanted reflections from the reference reflector measurement path by using the beam steering mechanism to direct these harmful signals away from the optical detector, while allowing the useful reference distance measurement signals to pass through to the detector.
Solution Approach 2:
The patent applies different optical path treatments to different portions of the light field. The beam steering mechanism selectively processes useful reference signals versus unwanted reflections, giving different local qualities to different light paths based on their utility for measurement.
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 accuracy by eliminating spurious reflections and cavity errors, enhancing the precision of 3D coordinate determination in various lighting conditions.
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 reflections from the bandpass filter and a reflecting surface of the optical detector may act as an etalon, resulting in multiple reflections of the returning laser light
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
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.