Laser Beam Control in Opthalmology – Focus on the Eye

Piezo tip/tilt mirror

The use of piezo-based tip/tilt mirror systems and ultrasonic drives from PI guarantees the precision required for the refractive correction of visual acuity. The drives are used to control and focus the laser beam.

When corneal tissue is removed with laser beams to model the shape of the cornea in the optical axis, the resulting refractive power of the cornea matches the length of the eyeball again. For laser beam control, piezo-driven tip/tilt mirror systems not only offer the required accuracy but high accelerations and a great dynamic bandwidth as well. They are compact and can be integrated in higher-level systems, even in small spaces. They allow an optical deflection area of up to 120 mrad, extremely fast response behaviour (10ms to 1ms with mirror) as well as position resolutions into the nanoradian range. Piezo actuators are the driving force behind these one-, two- or three-axis systems.

In the case of tip/tilt mirror systems with several motion axes, piezo drives are used in parallel-kinematics positioning systems. Unlike serial systems, there is only one moving platform with a common pivot point. Integrated high-resolution position sensors ensure high linearity values of better than 0.25% over the full travel range and a repeatability of typically 5µrad.

Ceramic PILine® ultrasonic motors also allow extremely high velocities and acceleration while having very compact dimensions. The patented drive principle makes them self-locking when at rest. The precision micro linear stage M 663 achieves velocities of up to 400mm/s and travel ranges up to 19mm with resolutions up to 0.1µm.

PI additionally offers drive electronics and servo controllers that are adapted to the positioning systems and thereby simplify integration in customer systems.

For further information please contact PI-Medical.

Image: Compact piezo tip/tilt mirror with two orthogonal axes and 100 mrad optical deflection angle with 0.0005 mrad resolution; length 38mm.

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