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Galvo Mirror Systems: Beam Diameter

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Larger Beam Diameter Scanning Galvo Systems




  • For Larger(<10mm) Beam Diameters
  • Silver-Coated Mirrors
  • 1D and 2D Kits Available
  • Easy Integration into OEM Systems
  • Analog Control Electronics

Features

  • Moving Magnet Motor Design for Faster Response
  • High-Precision Optical Mirror Position Detection
  • Analog PD Control Electronics with Current Damping
    and Error Limiter
  • Protected Silver Mirror Coating
  • Custom Coatings (e.g., Aluminum) Available upon Request

Galvo Motor/Mirror Assembly
The galvo consists of a galvanometer-based scanning motor with an optical mirror mounted on the shaft and a detector that provides positional feedback to the control board. The moving magnet design for the GVS series of galvanometer motors was chosen over a stationary magnet and rotating coil design in order to provide the fastest response times and the highest system resonant frequency. The position of the mirror is encoded using an optical sensing system located inside of the motor housing.

Due to the large angular acceleration of the rotation shaft, the size, shape and inertia of the mirrors become significant factors in the design of high performance galvo systems. Furthermore, the mirror must remain rigid (flat) even when subjected to large accelerations. All these factors have been precisely balanced in our galvo systems in order to match the characteristics of the galvo motor and maximize performance of the system.

Scanning Galvo Mirror Assembly and Driver Board
All Thorlabs scanning galvo mirror systems feature a mounted single- or dual-axis mirror/motor assembly and driver card(s). Shown to the right is the 10 mm 1D galvo mirror and driver card with heatsink. The mirror assembly features multiple mounting holes and a rotatable collar mount for the mirror/motor. A flying lead allows connection to the driver board. Please see below for additional mounting options and accessories.

Servo Driver Board
The Proportional Derivative (PD) servo driver circuit interprets the signals from the optical position detecting system inside the motor and then produces the drive voltage required to rotate the mirror to the desired position. The scanner uses a non-integrating, Class 0 servo that is ideal for use in applications that require vector positioning (e.g., laser marking), raster positioning (printing or scanning laser microscopy), and some step-and-hold applications. Furthermore, the proportional derivative controller gives excellent dynamic performance. The circuit includes an additional current term to ensure stability at high accelerations. The same driver board is used in all of our galvo systems.

System Operation
The servo driver must be connected to a DC power supply, the galvo motor, and an input voltage source (the monitoring connection is optional). For continuous scanning applications, a function generator with a square or sine wave output is sufficient for scanning the galvo mirror over its entire range. For more complex scanning patterns, a programmable voltage source should be used. The ratio between the input voltage and mirror position is switchable between 0.5, 0.8, and 1. For the GVS011 and GVS012 systems, the ±10 V input produces the full angular range of ±20° with a scaling factor of 0.5. The control circuit also provides monitoring outputs that allow the user to track the position of the mirror. In addition, voltages proportional to the drive current being supplied to the motor and the difference between the command position and the actual position of the mirror are supplied by the control circuit.

Closed-Loop Mirror Positioning
The angular orientation (position) of the mirror is optically encoded using an array of photocells and a light source, both of which are integrated into the interior of the galvanometer housing. Each mirror orientation corresponds to a unique ratio of signals from the photodiodes, which allows for the closed-loop operation of the galvo mirror system.

The GVS011 and GVS012 systems can be driven to scan their full ±20° range at a frequency of 65 Hz when using a square wave control input voltage and 130 Hz when using a sine wave. For a ±0.2° small angle, the step response is 400 µs. The maximum scan frequency is 1 kHz and the angular resolution is 0.0008° (15 μrad, with GPS001 Linear Power Supply).

Scan Lens Mounting Bracket
The GVS012(/M) two-channel galvo mirror pair is compatible with our GAS012 mounting bracket (sold below). This bracket allows the galvo mirrors to be mounted along with one of our F-Theta or Telecentric Scan Lenses (see photo to the right). The complete assembly can be easily integrated into a standard breadboard- or optical table-based optomechanical setup.

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