Counter-Rotating Disk Prisms Stabilize Surveying Instruments
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Solution Overview
Problem
Existing surveying instruments with rotating scanning modules generate Coriolis forces during handheld or unstable measurements, affecting stability and measurement accuracy.
Innovation Solution
A surveying instrument with a pair of disk prisms and an arithmetic control module that controls the deflection of the distance measuring light to suppress Coriolis forces by balancing the mass and angular velocity of the prisms, allowing stable measurements even in unstable conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If a continuously rotating prism is used to scan the distance measuring light, then the laser scanner can be reduced in size and weight for handheld use, but Coriolis force is generated that affects measurement stability
Solution Approach 1:
The single rotating prism is segmented into a pair of prisms that rotate in opposite directions. Each prism rotates at the same speed but in reverse, creating equal and opposite Coriolis forces that cancel each other out. This segmentation allows the system to maintain the compact handheld form factor while eliminating the destabilizing Coriolis force effect.
Solution Approach 2:
The second prism acts as a counterweight to the first prism, with both prisms having equal mass and rotating at equal speeds in opposite directions. The Coriolis force generated by one prism is counterbalanced by the equal and opposite Coriolis force from the other prism, stabilizing the measurement system during handheld operation.
2Reliability
If the laser scanner is mounted on a rigid tripod for stable measurement, then measurement stability is improved, but the device becomes less portable and more complex to set up
Solution Approach 1:
By segmenting the rotating prism into a pair of oppositely rotating prisms, the system eliminates Coriolis force effects that would otherwise require a rigid tripod for stable measurement. This allows the device to be operated handheld or on unstable surfaces without compromising measurement stability, significantly improving ease of operation and portability.
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
Stabilizes the attitude of the surveying instrument and achieves accurate three-dimensional point cloud data acquisition by minimizing Coriolis forces, ensuring stable measurements in handheld or non-level conditions.
Implementation Method 1
an optical axis deflector disposed on a reference optical axis of the distance measuring module and configured to deflect the distance measuring light with respect to the reference optical axis
Implementation Method 2
Coriolis force is generated as prisms rotate, and there is a possibility that this Coriolis force affects a supporting attitude of the laser scanner in an unstable support such as a handheld state and affects stability of measurement
Data Source
Figure 1
Figure 2A~3
Figure 4A~4C
AI summary
A surveying instrument includes a distance measuring module (2) configured to project a distance measuring light (21) and to receive a reflected distance measuring light (22) from an object and to perform a distance measurement, an optical axis deflector (9) disposed on a reference optical axis of the distance measuring module and configured to deflect the distance measuring light, an optical axis deflection motor driver (8) configured to drive the optical axis deflector, an attitude detector (6), a measuring direction detector (7) configured to detect a projection direction with respect to the reference optical axis of the distance measuring light, a storage module (5), and an arithmetic control module (4) configured to synchronously control the distance measuring module, the attitude detector, and the optical axis deflector, wherein the optical axis deflector includes a pair of disk prisms (17, 18) composed of optical prisms, and the arithmetic control module is configured to drive the optical axis deflector via the optical axis deflection motor driver and to scan the distance measuring light in a predetermined scan pattern and to reversely rotate one of the disk prisms with respect to the other so as to suppress generation of Coriolis force.