Surveying Beam Offset for Close-Range Distance Accuracy
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Solution Overview
Problem
Existing surveying instruments face significant measurement accuracy issues in close range due to partial shading of the detector by optical unit components, leading to systematic errors in distance measurements.
Innovation Solution
The surveying instrument employs a targeting state indicator to automatically adjust the measuring beam's direction, shifting it out of the shaded detector area, using beam deflection elements and angle determining units to enhance light impingement on the detector, thereby reducing measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measuring beam is targeted centrally on the retro-reflective target, then the target recognition and angle measurement are optimized, but the reflected beam is shaded by the optical unit component, leading to increased measurement errors in close range
Solution Approach 1:
Instead of targeting the beam centrally on the retro-reflective target, the patent inverts the approach by deliberately targeting a peripheral region of the target. This causes the reflected beam to hit a peripheral region of the detector that is not shaded by the optical unit component, thereby eliminating the shading effect while maintaining measurement accuracy through beam offset compensation.
Solution Approach 2:
The patent applies different targeting strategies to different regions of the retro-reflective target. The central region is used for angle measurement and target recognition, while a peripheral region is specifically targeted for distance measurement to avoid detector shading. This local differentiation resolves the contradiction between central targeting benefits and shading avoidance.
2Measurement precision
If the measuring beam is targeted on a peripheral region of the retro-reflective target, then the detector shading is avoided, but the beam must be deliberately misaligned from the target center
Solution Approach 1:
The patent employs a feedback mechanism where the system first determines the angular position and identifies the retro-reflective target using central targeting, then calculates the required beam offset to target a peripheral region. This feedback loop automatically adjusts the beam direction based on target characteristics and geometry, eliminating the need for manual alignment and simplifying operation despite the complex targeting strategy.
Solution Approach 2:
The system performs self-alignment by automatically determining the retro-reflective target's position and calculating the appropriate peripheral targeting offset. The instrument adjusts its own beam direction based on the detected target geometry and desired measurement parameters, making the complex peripheral targeting transparent to the user and maintaining ease of operation.
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
This approach improves distance measurement accuracy in close range by increasing the amount of light impinging on the detector, minimizing errors, and ensuring precise coordinate determination of retro-reflective targets.
Implementation Method 1
Retroreflectors have the characteristic of simply inversing the direction of the incoming light beam, when the centre of the retroreflector is targeted, and reflecting the incoming light beam in inverse direction with a beam-offset, when a peripheral region of the retroreflector is targeted.
Implementation Method 2
The emitted optical radiation is configured for electro-optical distance measurements, e.g. on the basis of a time-of-flight or phase measurement principle
Implementation Method 3
A recognition and/or measurement of this type of target object in angle coordinates can be performed using a position-sensitive optical receiving element in the device, for example with an area sensor in CCD or CMOS technology, a PSD on the basis of the lateral photoelectric effect
Data Source
Figure 1a~1d
Figure 2
Figure 3a~4c
AI summary
The present invention relates to a surveying instrument and method for accurately determining the distance to a, in particular retro-reflective, target in the close range for a specific setup of the surveying instrument, where the central part of the received ray bundle is shaded by a component of the optical unit of the surveying instrument. When targeting on the target in an on-target state, such as according to the state of the art, the accuracy of the distance measurement decreases in the close range, say the closer the target is located to the surveying instrument, due to spatial and temporal inhomogeneities of the beam profile. The present invention proposes to target on the target in a misaligned targeting state, such that the reflected measuring beam impinges on a part of the detector surface, which is not shaded, thereby leading to an increased measuring accuracy. By shifting the impinging position of the reflected measuring beam on the detector surface such, that it is shifted out of the shaded part of the detector, by averaging the distance measurement values of the spatially inhomogeneous beam profile. In order to further increase the measuring accuracy, the distance measuring values can furthermore be averaged over time. The present invention furthermore relates to a computer program product, wherein the computer program product is saved on a machine-readable carrier, particularly saved on a surveying instrument according to the present invention, or a computer-data-signal for the implementation of an inventive method.