Laser Radar Focus Mechanism with Anti-Weight Spring Compensation

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Solution Overview

Problem

Conventional focus mechanisms in laser radar systems lack the desired accuracy and stability due to large focus stages being far from beam-forming optical components, making precise alignment and temperature stability challenging.

Innovation Solution

A focus stage with a linear guide and motor configuration, including first and second linear encoders to provide precise carriage position, and an actuator-spring combination to compensate for orientation-dependent gravitational forces, ensuring stable and accurate focus adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional translation mechanism is used to focus the laser beam, then the focus stage can be positioned, but alignment is difficult and stability over a wide temperature range is problematic

Engineering Contradiction:

Improvefocus accuracyVSAvoidstability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

A spring mechanism is introduced to counteract the weight of the focus stage and corner cube assembly. The spring is pre-loaded to provide an upward force that balances gravity, ensuring that the stage remains stable and does not drift due to gravitational effects when the motor is not actively driving the stage. This improves reliability and stability over temperature ranges.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

Two linear encoders are positioned on opposite sides of the corner cube to measure its position. By taking measurements from both encoders and averaging them, the system compensates for potential tilt or misalignment errors, providing more accurate feedback on the actual position of the corner cube. This enhances measurement precision and alignment accuracy.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If the focus stage is positioned a significant distance from beam-forming optical components, then the corner cube can be translated for focusing, but alignment is difficult and errors associated with tips and tilts are not fully reduced

Engineering Contradiction:

Improverange measurement accuracyVSAvoidalignment difficulty

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The spring mechanism supports the weight of the corner cube and focus stage, reducing the load on the translation mechanism. This allows for more precise positioning with less mechanical play and improved repeatability, enhancing range measurement accuracy.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The dual linear encoder configuration provides redundant position measurements that can be averaged to compensate for angular errors. When the corner cube is tilted during translation, each encoder measures a slightly different position; averaging these measurements cancels out the tilt-induced errors, providing accurate position feedback despite alignment imperfections.

Inventive Principle:

Principle #23Feedback

3Device complexity

If a single linear encoder is used to measure carriage position, then the system is simpler, but position measurement accuracy is reduced due to potential tilt errors

Engineering Contradiction:

Improveencoder configurationVSAvoidcarriage position accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Inventive Principle:

Principle #23Feedback

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 provides repeatable corner cube position, accommodates various orientations, and operates effectively over a large temperature range, reducing errors in focus position and range measurement accuracy.

Implementation Method 1

An actuator and an elastic member are coupled to a focus adjustment optical element so as to compensate orientation-dependent forces. In some examples, the actuator is configured to apply a force to the focus adjustment optical element so as to compensate an orientation-dependent gravitational force.

Methodology Applied

Scientific EffectGravitational force: Gravitation

Implementation Method 2

An actuator and an elastic member are coupled to a focus adjustment optical element so as to compensate orientation-dependent forces. In other examples, the elastic member is a spring.

Methodology Applied

Scientific EffectElastic force: Elasticity

Implementation Method 3

First and second linear encoders are oppositely situated along the axis and provide an indication of carriage position based on a combination of encoder signals from the first and second linear encoders.

Methodology Applied

Scientific EffectLinear encoder measurement:

Implementation Method 4

the focus adjustment optical element is configured to adjust a focus of a beam on a target in a laser radar and is a corner cube or roof prism.

Methodology Applied

Scientific EffectCorner cube reflection: Retroreflector

Data Source

PatentUS9644720B2Orientation independent focus mechanisms for laser radar

Publication Date: 2017.05.09 NIKON CORP

AI summary

Focus arrangements for laser radar and other applications provide compensation of orientation-dependent gravitational forces. A linear stage can be preloaded and provided with balanced linear encoders so that gravitational force induced pitch, yaw, and roll can be reduced, detected, or compensated. Alternatively, movable focus elements can be secured to actuator driven spring assemblies that are controlled to compensate orientation-dependent gravitational forces.