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Galvo Mirror Laser Scanning Scheme: Design and Application

The main advantages of galvanometric laser scanning are high speed and high precision, widely used in fields such as laser processing, life sciences, and medical diagnosis. Position sensors are integrated into motor design to provide predictable linear time-invariant (LTI) systems with closed-loop servo control. The mechanical angle can reach ±20 degrees, and the scan rate varies from several Hz to several kHz; low inertia systems with smaller reflection mirrors commonly have faster speeds than heavier systems. Galvoes can be used single-axis, or they can be combined into multi-axis configurations, or complemented by techniques such as resonance or polygonal scanners to achieve more complex scan shapes.

The infrastructure of galvo control can be analog, digital, or hybrid. Axis angle sensors are built into the galvo structure, reducing motion mass and improving system performance, so high-performance position detectors are essential. Modern galvoes use dynamic magnetic design to provide a high torque ratio. For small systems, a small motor is usually used to drive relatively large loads. If the load approaches or exceeds the rotor inertia, harmful mechanical resonance may occur, which can be suppressed by notch filters. The factory settings of amplifiers for notch, PID, and others provide stable and reliable performance for users.

Design and application of single-axis and dual-axis galvoes

Single-axis galvo kits generally include galvo reflection mirrors, servo amplifiers, and connecting cables. Coating options for the reflection mirror include broadband coating for infrared and visible light and dielectric coating for specific single or multiple wavelengths. A complete galvo application also requires the purchase of various accessories, servo coolers, galvo mounting fixtures, signal sources, and light sources. Dual-axis galvoes are the core building block for processing and three-axis systems. A matched and tuned XY dual-axis galvo is critical for building a high-performance scanning system, and the two reflection mirrors must ensure precise alignment of the optical path.

In addition, the dual-axis galvo scan head is compatible with various lasers and provides the best spot size, working distance, and field of view through selected lenses, improving laser processing speed. The following are the XG and DCB series scan heads, which have a wide range of applications when combined with appropriate lasers and lenses: marking; cutting solar cell membranes; surface treatment and deep engraving; semiconductor material cutting, scribing, and trimming; low-power welding and sintering.

Design and application of three-axis scan head

The three-axis scan head includes a standard XY dual-axis scan head and a Z-axis electric focus without the need for an fθ lens. The flexible three-axis scan head is very suitable for three-dimensional non-flat surface marking, with a field of view up to one square meter, so only a single-pass scan can handle the entire solar cell panel, and the focused spot diameter can be as low as 22 µm, and the heat can be controlled by intentional defocusing.

The three-axis scan head uses a post-objective scan configuration, where the moving reflection mirror is located behind the objective lens. The laser enters from the right, passes through the beam expander and objective lens in turn, and is then focused onto the work surface by the scanning reflection mirror. The curved surface is the focusing result of the beam expander being stationary (the same is true for scanning with an fθ lens), and in order to provide a flat field of view, only need to move the beam expander, and the controller calculates the correction amount for any XY position and adjusts the Z-axis focus accordingly.

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