Laser marking requires highly precise control of angular position and velocity within laser beam and mirror assemblies. With the custom development of the MII1900P sensor head, our customer was provided 1.2 million counts per revolution of precision for controlling their product.

The Challenge

Laser marking systems use lasers to engrave or mark a variety of products, ranging from electronic components to medical devices to food packaging. The technique involves steering a laser beam with speed and precision using high quality mirrors driven by highly responsive voice-coil motors called galvanometers. Controlling the angular position and velocity of galvanometers requires very small but highly accurate non-contact rotary optical encoders.

The Solution

The Mercury 1200 analog encoder was chosen by a leading supplier of laser marking systems to provide their servo control system with incremental Sin/Cos feedback. It was paired with a tiny 12mm diameter optical disk which, after 7 bit interpolation in the customer’s electronics, provided over 200 thousand counts per revolution. For even higher accuracy systems requiring even tighter line control, the custom MII1900P sensor head was designed to provide more than 1.2 million counts per revolution.

The Benefit

The Mercury 1200 sensor on a glass disk achieves up to 120nm cyclical error with customer supplied gain, offset and phase corrections. The compact design provides this highly accurate feedback in a total package less than 9mm high. The MII1900P encoder reduces that cyclical error to only 30nm (while still reducing the total package height by almost 2mm) allowing the customer to mark with industry leading resolution and line quality.

Specifications

M1200 Dimensions15.2x 8.8 x 5.6mm
MII1900P Dimensions18.9 x 18.2 x 5.4mm
InterfaceAnalog Sin/Cos with index
Grating Dimensions12 OD x 6 ID x 0.9mm
Grating Period20µm
System Resolution30 & 5µrad
Sensor Weight2.6g