Laser Galvo: A High-Precision, High-Speed Laser Scanning Component

A laser galvo, also known as a laser scanner, is an exceptional vector scanning component. It integrates multiple key components, including the X-Y optical scan heads, an electronic drive amplifier, and optical mirrors. When the controller sends a signal, the signal is processed by the drive amplification circuit, which then precisely drives the optical scan head. Consequently, the deflection of the laser beam on the X-Y plane is finely controlled.

The Working Principle of the Laser Galvo

The working principle of the laser galvo, a special type of oscillating motor, lies in the torque generated by the coil in a magnetic field. Unlike a rotating motor, its rotor is equipped with a mechanical torsion spring or an electronically provided restoring torque. This torque's magnitude is closely related to the rotor's deviation angle from the equilibrium position. When current flows through the coil, the rotor deflects until the deflection angle corresponds to the amount of current. At this point, the electromagnetic torque balances with the restoring torque, allowing the rotor only to deflect without rotating. This characteristic allows the laser galvo to accurately reflect the current's magnitude, a design concept inspired by the current meter but replacing the traditional needle with a mirror.

Key Components of the Laser Galvo

The galvo comprises several key components, including the moving coil, core, suspension, damping, indicator, and zero adjustment.

The moving coil, one of the crucial components of the laser galvo, is meticulously suspended between the poles of a strong horseshoe magnet and the core. It is designed with a rectangular or circular cross-section, wrapped with n turns of fine wire, closely related to the current to be measured. The unique placement of the moving coil allows it to rotate freely around a vertical axis. The horseshoe design of the magnet ensures a radial distribution of the magnetic field.

The shape of the core corresponds to the coil, such as a spherical core for a circular coil and a cylindrical core for a rectangular coil. The core provides a low magnetic resistance path for the magnetic flux, generating a strong magnetic field, which in turn enhances the deflection torque and increases the sensitivity of the moving coil galvo.

The suspension system is critical for ensuring the accuracy of the galvo. It is made of thin phosphor bronze strips that serve as coil leads, while another lead is in the form of a thin wire spiral guiding from the bottom of the coil, known as the lower suspension. Some precision galvos require fine leveling to keep the suspension coil straight and centered, avoiding contact with the magnet or the core's pole pieces. Other types of galvos use a tension suspension with straight strips providing tension from both sides.

Moreover, the system uses eddy current damping, generating damping torque through eddy currents in a metal former. The indicator part involves a small mirror attached to the suspension device. Light is projected onto the suspension device through a glass window on the instrument's exterior and reflected on a scale for reading. The scale is usually about 1 meter away from the mirror. Finally, a torque head is provided for zero adjustment to adjust the coil's position and its zero setting.

The laser galvo plays a crucial role in laser marking, engraving, and welding fields. Its core components include the drive board and high-speed oscillating motor, forming a high-precision, high-speed servo control system. The system’s high precision is attributed to the fine detection of current, ensuring the accuracy of the deflection angle. The high speed is reflected in the galvo's ability to quickly change angular velocity, achieving rapid beam movement. Additionally, the compact and small design of the laser galvo makes it highly suitable for various integrated applications.