LFA-3404 Linear Focus Actuator


LFA-3404 Linear Focus Actuator: is a high performance compact positioning actuator. It was specifically developed for applications requiring both high precision and high-speed positioning over a short to medium stroke. This product mates the voice coil motor to a perfectly smooth flexure guidance system and a very high resolution position feedback encoder.  The LFA is well suited for optical focusing and other micro-positioning applications in markets such as semiconductor, medical, optical testing, scanning microscopy, circuit board assembly and micro manufacturing.  The LFA-3404 has a 34 mm diameter clear aperture through its center, and 4mm of available stroke. Different configurations of stroke length, force constant, optic mounting, and other options are available as needed.  The LFA3404 comes stock with either a M26 or M25 Threaded mount. Other threaded holes exist.

Voice Coil Motor: The motor used in the LFA is a custom signed moving coil motor optimized using advanced computer modeling.  The magnets used in Equipment Solutions motors have some of the highest magnetic flux densities available. Its coil characteristics, including the resistance and inductance, were closely designed to match the capabilities of the SCA814 Servo Controlled Amplifier.  The motor can drive the stage to unparalleled accelerations and peak velocities.

Flexure Stage Guidance: The LFA series uses flexures for guidance along the motion axis.  Flexures provide perfectly smooth motion.  When designed and used properly they can have infinite lifetime.   The LFA flexure and motor configuration is symmetric about a central axis where an optic is usually mounted.  The resultant optical axis is coaxial with the motion axis of the flexure and the force vector of the motor, and this axis passes through the center of mass of the moving system, thus producing no net torques.   The LFA flexure is stiff in all 5 cross-axes to the motion axis, except there is a small parasitic rotation about the motion axis that is proportional to the position on the motion axis.  This parasitic motion is inherent in flexure systems, but which axis is left to the choice of the designer.   ESI chose the parasitic axis to be a rotation about the motion axis that doesn’t affect the intended application for most customers.  Most LFAs are used in optical applications where a rotation of the optic about the optical axis is not an issue.

Position Feedback: In its standard configuration the LFA uses a non-contact optical analog position encoder that makes it directly compatible with the SCA814 Servo Controller Amplifier  . The 50 nanometer positioning repeatability described in the specifications section assumes this sensor technology. The analog nature of the position sensor promotes the exceptionally high positioning resolution and bandwidth.  For compatibility with digital servo systems the LFA-2010 can be optionally configured with a digital quadrature encoder.




Clear Aperture 34 mm
Range of Motion 4 mm
Positioning Resolution 50 nm
Peak Force 40 lbs (for 10 sec.)
Max Continuous Force 5 lbs
Motor Constant 2 lbs/Amp
Coil Resistance 2.3 ohms
Coil Inductance 420 uH
Non-Linearity <+/- 0.5%
Repeatability, Short Term 100 nm
Repeatability, Long Term 50 ppm/1000hrs
Temperature Stability +/- 250 nm/°C
Hysteresis None
Dead-band None
Travel Non-Straightness <0.5 um
Flexure Parasitic Rotation 0.1 degrees  per mm travel
Dimensions 89mm (approx. dia.) x 57 mm
Total Mass 1.0 kg
Moving Mass 90 g




pdfLFA-3404 Linear Fouc Actuator Brochure provides a brief presentation of the products features and specifications.

pdfVoice Coil Stage Interfacing and User Manual  deatils installation, operation and maintenance of the product.

zipLFA-3404 Linear Foucs Actuator Interface Drawings presents the mechanical details necessary for integration of the product .

zipLFA-3404 Typical Motor Force Constant