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Sensor Heads

Sensor head classes

Currently, SmarAct offers four classes of sensor heads that were designed for a great variety of applications.


The sensor heads using a collimated beam are mainly used for large working ranges and distances. These heads can have a very small form factor.


A focused beam is mainly used for measurements on very small targets. The focusing sensor heads additionally offer a large angular working range.

Line focused

Line focusing sensor heads are used for an enhancement of signal intensity in one dimension. This allows improved performance in measurements on cylindrical targets, for example.

Head assemblies

Special sensor head assemblies can be used for a wide range of applications. Three sensor heads can be pre-aligned for angular measurements, for example. 

Sensor Head Overview


Head type Description Dimensions Beam waist diameter Working distance
 Head type C01:
Collimated output beam for most common applications
Ø 4 mm,
length 13 mm
400 µm 13 – 650 mm
Head type C02:
Collimated probe beam for large working distances
Ø 9 mm,
length 23 mm
~1600 µm 0 – 1000 mm
Head type C03:
Compact sensor head with large spot size for retro-reflector targets
Ø 6 mm,
length 21 mm
~1600 µm 0 – 500 mm
Head type F01:
Focused probe beam for small targets and providing high angular tolerances
Ø 6 mm,
length 21 mm
~30 µm
13 mm
Head type L01:
Line focused probe beam for rotating targets, insensitive to its wobble
~50 µm
(focused axis)~1500 µm
(orthogonal axis)
30 mm
Customized See the customization overview

Sensor head options and customizations

Differential measurements

Due to the Michelson principle, PicoScale sensor heads allow to perform differential displacement measurements of two target mirrors with a single sensor head. Therefore, the “ER” (external reference) option utilizes a beam splitter without a reference mirror so that two probe beams exit the sensor head.

Low reflectivity targets

PicoScale sensor heads allow to measure the displacement of targets that have almost arbitrary reflectivity without additional and sophisticated considerations. It can, however, be beneficial in terms of signal-to-noise ratio to increase the power in the probe beam. Therefore, the “BSR80” option utilizes a beam splitter with a 80:20 beam splitting ratio to guide more power into the probe beam.

Selection Guide for Sensor Heads

Head type Working range Angular working range Retro-reflector target?
C01 medium medium no
C02 very large low yes
C03 large low yes
F01 small large no
L01 small large no

(More sensor heads coming soon. Please also see our customization overview.)

Featured Accessory

Adapters for 1/2″ or 1″ mounts

UHV feedthroughs

Various form factors

SmarAct manufactures all products in-house so that we can efficiently design and produce customized sensor heads. This includes customized solutions for setups with specific space constraints. For example, the “FR” (front reference) option utilizes a beam splitter, where the reference mirror of the Michelson interferometer is coated to the front surface so that the probe beam exits perpendicularly compared to a standard sensor head.

UHV and cold environments

The PicoScale sensor head type C01 can be used to measure in ultra-high vacuum with the corresponding option. For measurements in cryogenic environments please contact SmarAct.

Further customizations

For more options please refer to our customization overview. Feel free to contact us if you do not find the right head for your application: together we will find a solution!

SmarAlign window

Most PicoScale sensor heads utilize the open port of the Michelson interferometer to provide the SmarAlign window – a very convenient indicator for fast initial coarse alignment.  Read more