Three-Mirror Laser Scan Head Layout for Compact Axis Alignment

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Solution Overview

Problem

Existing laser scan head designs face challenges in optimizing size, scan angle, scan orientation, and optical performance, particularly in combining Galvanometer and Resonant scanning modes within a compact enclosure while maintaining user-friendliness and noise isolation.

Innovation Solution

The design incorporates a configuration where the folding mirror and relay lenses tilt to align the resonant scanner and galvanometer axes parallel, reducing the need for beam tilting and incorporating a hermitically sealed block for noise isolation, allowing for a compact and user-friendly RGG scan head.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If all scanning components are placed in a compact enclosure, then the device size is reduced, but the alignment precision and optical performance deteriorate

Engineering Contradiction:
Improvescan head sizeVSAvoidalignment precision
Core Design Contradiction:
Volume of moving objectVSManufacturing precision

Solution Approach 1:

The scan head is divided into separate functional modules: resonant scanner assembly, galvanometer assemblies, and relay lens assemblies. Each module can be independently aligned and adjusted, allowing compact packaging while maintaining precise optical alignment through modular assembly procedures

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Relay lenses are introduced as intermediary optical elements between the scanners and the output. These relay lenses facilitate beam transfer and enable precise alignment of the scanning axes without requiring the scanners to be in direct proximity, thus allowing compact enclosure while maintaining alignment precision

Inventive Principle:
Principle #24Intermediary (Mediator)

2Area of stationary object

If the scanning angle is increased to cover larger area, then the scan coverage is improved, but the optical system complexity increases

Engineering Contradiction:
Improvescan coverage areaVSAvoidoptical system complexity
Core Design Contradiction:
Area of stationary objectVSDevice complexity

Solution Approach 1:

The patent employs tilted mounting of the resonant scanner and galvanometer assemblies at specific angles (e.g., 45 degrees) relative to the optical axis. This angular arrangement allows the laser beam to be deflected through larger angles to cover a broader area while maintaining a relatively compact optical path through dimensional reconfiguration of the beam trajectory

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Measurement precision

If noise isolation is enhanced for resonant scanner, then the measurement precision is improved, but the device complexity increases

Engineering Contradiction:
Improvescan position precisionVSAvoidnoise isolation structure
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The resonant scanner is physically separated from the galvanometer assemblies and placed in its own isolated mounting structure. This extraction of the noise-generating resonant scanner into a separate module allows for dedicated noise isolation measures (such as damping mounts or isolated positioning) without complicating the overall device structure, as the isolation is implemented at the module level

Inventive Principle:
Principle #2Taking out (Extraction)

4Volume of moving object

If the air space between mirrors is reduced to compact the design, then the device volume is reduced, but the optical performance deteriorates

Engineering Contradiction:
Improvescan head volumeVSAvoidoptical performance
Core Design Contradiction:
Volume of moving objectVSReliability

Solution Approach 1:

The optical components are arranged in a nested configuration where the resonant scanner, galvanometer assemblies, and relay lenses are positioned in concentric or layered arrangements. This nesting allows the beam to traverse through multiple components in a compact sequence, minimizing the air space between mirrors while maintaining sufficient optical path length for reliable beam transmission and scanning performance

Inventive Principle:
Principle #7Nested doll (Nesting)

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 configuration enables efficient scanning with reduced alignment uncertainties, compact dimensions, and effective noise isolation, enhancing the overall performance and usability of the RGG scan head.

Implementation Method 1

The folding mirror and relay lenses tilt to align the resonant scanner and galvanometer axes parallel

Methodology Applied
Scientific EffectLight reflection: Reflection

Implementation Method 2

incorporating a hermitically sealed block for noise isolation

Methodology Applied
Scientific EffectPhysical containment: Physical Containment

Data Source

PatentEP3788427B1Laser scan head design for three scanning mirrors with optics
Publication Date: 2024.10.23 THORLABS INC
  • EP3788427B1 patent drawingFigure 1
  • EP3788427B1 patent drawingFigure 2
  • EP3788427B1 patent drawingFigure 3

AI summary

A scanning device including: a first, second and third scan mirrors; a first and second relay lenses; and a mirror; wherein the rotational axis of the second scan mirror is tilted with a first angle with respect to a reference plane, the optical axis of the first relay lens is tilted with the first angle with respect to the reference plane, the optical axis of the second relay lens is parallel to the reference plane and is orthogonal to that of the first relay lens, and the rotational axis of the first scan mirror is parallel to the reference frame; and the first and second scan mirrors, and first and second relay lenses are arranged such that the respective axes of the first and second scan mirrors, and first and second relay lenses lie on a plane that is tilted at the first angle with respect to the reference plane.