Total Station Calibration Using Collimated Light and Camera Images
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Solution Overview
Problem
Traditional manual calibration of total stations for surveying is time-consuming and prone to errors due to mechanical imperfections and environmental influences, leading to misalignment of optical axes with the sighting axis.
Innovation Solution
A method and apparatus for total station calibration that uses a collimated calibrating light beam to determine collimation errors by capturing images with a camera, allowing automatic calibration of multiple measurement channels based on the position of the light beam in the image, with a calibrated reference measurement channel serving as a basis for relative collimation error determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual calibration methods are used, then calibration can be performed, but the process is time-consuming and prone to errors
Solution Approach 1:
The patent replaces manual mechanical calibration procedures with an automated optical system. A collimated light beam is emitted through the objective lens and captured by a camera, with the processing unit automatically calculating collimation errors based on the captured image data, eliminating the need for manual sighting and measurement operations
Solution Approach 2:
The calibration system performs self-calibration using its own internal components (objective lens, camera, and processing unit). The system emits the collimated light beam through its objective lens and captures the beam's position using its camera, automatically determining collimation errors without requiring external calibration equipment or manual intervention
2Measurement precision
If manual calibration is performed, then collimation errors can be determined, but the process requires experience and is prone to errors
Solution Approach 1:
The patent replaces manual calibration operations with an automated optical-electronic system. The processing unit automatically processes camera images to determine collimation errors, eliminating the need for operator experience and manual measurement skills
Solution Approach 2:
The patent introduces a camera as an intermediary to capture the position of the collimated light beam. This intermediary device provides objective, measurable data that the processing unit uses to calculate collimation errors, replacing subjective manual measurement with objective digital imaging
3Ease of manufacture
If traditional calibration is used, then measurement channels can be calibrated, but it requires manual sighting at external objects
Solution Approach 1:
The calibration system uses its own objective lens and camera to perform calibration. The objective lens is used to emit the collimated light beam, and the camera captures the beam's position, allowing the system to self-calibrate without requiring external objects or separate calibration equipment
Solution Approach 2:
The objective lens serves dual functions: it focuses light during normal surveying operations and emits collimated light beams during calibration. The camera also serves dual purposes by capturing images for surveying and capturing the collimated light beam position for calibration, eliminating the need for separate calibration hardware
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 method reduces calibration time and errors by enabling precise, automated alignment of optical axes with the sighting axis, improving measurement accuracy without the need for manual sighting at external objects.
Implementation Method 1
a collimated calibrating light beam enters the centre unit via an objective of the centre unit for further propagation towards the camera
Data Source
AI summary
The present disclosure relates to a total station and to method of calibrating a total station (500). The total station comprises a centre unit (510) mounted on an alidade (520) for rotation about a first axis (130), wherein the alidade is mounted on a base (540) of the total station for rotation about a second axis (150) orthogonal to the first axis such that a sighting axis (170) of the total station is rotatable about a rotation point. The centre unit includes a plurality of measurement channels, wherein a measurement channel is associated with a measuring device (512, 514, 518) having an optical axis and wherein at least one measuring device is a camera (512) configured to capture images. The method comprises determining a collimation error relative to the sighting axis for any one of the plurality of measurement channels, thereby providing a calibrated reference measurement channel. The method comprises rotating the centre unit around at least the first axis to a predetermined position at which a collimated calibrating light beam enters the centre unit via an objective of the centre unit for further propagation towards the camera. The collimated calibrating light beam is related to (i) at least one measurement channel to be calibrated if the calibrated reference measurement channel is the measurement channel associated with the camera or (ii) said calibrated reference measurement channel if the calibrated reference measurement channel is a measurement channel other than the measurement channel associated with the camera. The method further comprises capturing at least one image with the camera, wherein the collimated calibrating light beam is detectable in the at least one image, and determining a relative collimation error between the measurement channel associated with the camera and the at least one measurement channel to be calibrated if the calibrated reference measurement channel is the measurement channel associated with the camera, or between the measurement channel associated with the camera and the calibrated reference measurement channel if the calibrated reference channel is a measurement channel other than the measurement channel associated with the camera, based at least on a position of an image point corresponding to the collimated calibrating beam in the at least one captured image.