Switchable Aperture Optical Distance Meter for Retroreflective and Diffuse Targets
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Solution Overview
Problem
Conventional laser trackers struggle to accurately measure distances on diffusely scattering targets without retroreflective markers due to insufficient receiving optical unit capability, leading to accuracy losses and interference from multiple reflections and shadows, which complicates production and increases costs.
Innovation Solution
An optical distance meter with a receiving channel that adapts aperture size and includes a switchable attenuation element and correction optical unit to optimize beam capture and reduce interference, allowing for precise measurements on both retroreflective and diffusely scattering targets by adjusting aperture settings and using a partially-transparent beam splitter to minimize shadows and boomerang signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the receiving optical unit uses a large aperture to capture weak signals from diffusely scattering targets, then signal capture capability is improved, but measurement accuracy deteriorates due to multiple reflections and shadows
Solution Approach 1:
The receiving aperture is made dynamically adjustable through an iris diaphragm mechanism, allowing the system to switch between a large aperture for capturing weak signals from diffusely scattering targets and a small aperture for maintaining measurement accuracy on retroreflective targets. This dynamic adaptation resolves the contradiction by enabling the aperture size to change based on the target type being measured.
2Measurement precision
If the receiving optical unit uses a small aperture to avoid multiple reflections and shadows, then measurement accuracy is improved, but signal capture capability deteriorates
Solution Approach 1:
The iris diaphragm enables dynamic adjustment of the aperture size, allowing the system to use a large aperture when measuring diffusely scattering targets to maximize signal capture, and switch to a small aperture when measuring retroreflective targets to eliminate multiple reflections and shadows. This resolves the contradiction by making the aperture size adaptive to the measurement requirements.
3Reliability
If a fixed large aperture is used for reflector-less measurement, then signal capture is improved, but interference from multiple reflections increases
Solution Approach 1:
The system uses a dynamically adjustable iris diaphragm that reduces the aperture size during retroreflective target measurements to eliminate multiple reflections and shadows, then opens the aperture fully for diffusely scattering target measurements to maximize signal capture. This dynamic adjustment resolves the contradiction between signal capture and interference reduction.
4Object-generated harmful factors
If a fixed small aperture is used for retroreflective measurement, then multiple reflections are reduced, but signal capture capability deteriorates
Solution Approach 1:
The iris diaphragm mechanism allows the system to dynamically open the aperture to its full size when measuring diffusely scattering targets, maximizing signal capture capability, and close the aperture when measuring retroreflective targets to eliminate multiple reflections. This resolves the contradiction by making the aperture size adaptive to the target type.
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
The solution enhances measurement accuracy to sub-micron levels on retroreflective targets and improves signal capture on diffusely scattering targets, reducing errors and production complexity while maintaining high sensitivity.
Implementation Method 1
A target point can be represented in this case by a retroreflective unit (for example, corner cube prism), which is targeted using an optical measuring beam, in particular a laser beam
Implementation Method 2
the reflected beam is registered using registration means of the measuring device or the distance meter
Data Source
AI summary
An optical distance meter configured to carry out a distance measurement in a first measuring mode, in which the distance meter is set for distance measurement on a retroreflective target, and a second measuring mode, in which the distance meter is set for distance measurement on a diffusely scattering target. In this case, a first aperture of the receiving channel is set in the first measuring mode, which is smaller than an aperture set in the second measuring mode.