New Technology Development of Scanning Galvanometer

In the dynamic landscape of laser technology, the development of scanning galvanometers has undergone significant advancements. This article explores the latest technological innovations and challenges in the field, shedding light on applications, precision, and thermal considerations.

Technological Advances in Scanning Galvanometer Systems

A basic x-y scanning system may appear straightforward with two reflective mirrors driven by motors to redirect laser beams to specific areas. The working area's focus is ensured by a set of flat (f-) lenses within the x-y system software. For Nd:YAG lasers, the typical working range is 40×40 square millimeters (ff-=100mm) to 180×180 square millimeters (ff-=254mm). Advanced harmonic current lasers and diode lasers operate within the range of 40×40 square millimeters (ff-=100mm) to 120×120 square millimeters (ff-=163mm). The actual working range depends on the focal length of the flat lenses. Larger working areas and longer working distances are achieved by replacing flat lenses with focusing and movable lenses in front of the scanning galvanometer.

In diverse applications, high-precision positioning rates are crucial. For instance, with an f- lens focal length of 163mm, a scanning rate of up to ten meters per second can be achieved within a 120×120mm2 working area. However, even slight angular errors in the small mirror of the galvanometer can cause significant laser beam displacement on the working plane. Therefore, precision is paramount in the galvanometer drive, mirror glass, and reflection mirror mounting. Additionally, the heat generated by the galvanometer motor and controller electronic components can cause thermal drift, resulting in positioning errors. To address this, advanced solutions include water-cooled scanning galvanometers like Superscan-II-LD, ensuring long-term reliability even under continuous operation.

Reducing Scanning Galvanometer Internal Stress with New Technological Applications

In laser marking applications, the choice of reflective mirrors for scanning galvanometers includes those made from quartz substrates, with thicknesses ranging from 2.0 to 7.0mm, depending on mirror specifications and angular acceleration. Coated with an electrolyte solution, the mirror provides sufficient reflectance (>98.0%) within a matched wavelength range, making it suitable for powers up to 500W/cm2. However, emerging applications, such as high-polymer electron beam welding, present new challenges.

For precise control of product workpiece temperatures, especially in high-temperature environments, non-contact measurements are conducted using high-temperature sensors. In this scenario, radiation heat data signals must be reflected back along the laser beam path, for instance, by the galvanometer lens. The typical wavelength range for high-temperature measurements is 1.7 to 2.1 micrometers. Reflective coatings with an additional layer of aluminum on the back of quartz substrates effectively address challenges in this wavelength range.

Addressing Challenges in High-Power Applications of Scanning Galvanometer

In new applications requiring higher power, such as remote-controlled laser welding, laser cutting, or scanning heat treatment processes, output powers ranging from hundreds of watts to several kilowatts pose new challenges for scanning galvanometer heads. Despite highly reflective materials, a portion of the light source (<2%) may scatter and be absorbed by the mirror substrate or surrounding components. This becomes a significant concern as the internal heat generated by high-power lasers can lead to thermal drift and unreliable long-term performance fluctuations.

Therefore, water-cooling becomes essential for scanning equipment, although it may not entirely solve the problem. This is because it cannot prevent the thermal load on the quartz mirror and the resulting damages, such as adhesive deformation or loosening, or common failures in the galvanometer drive due to rotor and rolling bearing heating. In this context, new glass technology is indispensable.

Quartz's major drawback is its low thermal conductivity, resulting in poor cooling characteristics. Silicon-based materials, such as silicon or carbon-carbon composites, offer higher thermal conductivity. Using silicon-based materials allows for thinner substrates while mitigating overall weight, offering an optimal design solution in terms of reliability, weight, heat transfer, and moment of inertia, with careful solid model calculations for mirror substrate mechanical structure design.