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quDIS

Interferometric Displacement Measurement

  • quDIS Interferometric Distance Measurement - three channels in the 19" rack.
  • Overview
  • Applications
  • Sensor Heads
  • Accessoires
  • Downloads
The quDIS is a confocal displacement sensor, based on a Fabry-Pérot or Michelson interferometer, with highest signal stability of < 0,05 nm and a contrast independent measuring algorithm.

Next to displacement and distance measurement, vibration analysis is possible with a 25 kHz bandwidth in free space or glass rods & fibers as cavities.

Key Features

Confocal displacement sensor
Fiber interferometer
< 0.05 nm signal stability
20 … 1400 mm working distance
25 kHz bandwidth
Contrast independent, no periodical artifacts
3 sensor axes, multiple devices
Flexible fiber-based sensor heads

Applications

Slow drifts
Vibration analysis
Position and angles
Velocity and acceleration
Quality control
Fail-safe procedures
Beam interrupt compensation

Applications

The quDIS is a confocal displacement sensor with a high signal stability and a contrast independent measurement algorithm. The quDIS is a a laser interferometer configurable as a Fabry-Pérot or Michelson setup. Its high precision is required in various high-end applications in science and industry.

Sample positioning for X-ray diffraction measurements in synchrotron facilities

X-ray generation in a synchrotron with a crystalline sample.
A synchrotron accelerates charged particles – mostly electrons – close to the speed of light. When these particles are then accelerated transversely by magnetic fields, X-rays are produced. Their short wavelength is ideal for crystallography.

X-ray crystallography is used to determine the atomic and molecular structure of a crystal. The crystalline structure causes an incident X-ray beam to be diffracted in many specific directions. By measuring the angles and the intensity of these diffracted beams, a three-dimensional image of the electron density in the crystal can be obtained and thus the molecular structure can be identified.

In synchrotrons, charged particles like electrons are accelerated to very high speeds and then laterally deflected once or multiple times at regular intervals by bending magnets and other insertion devices. The X-rays produced by the acceleration of these charged particles are emitted in dozens of thin beams, directed at a beamline adjacent to the accelerator. A synchrotron can generate a much more focused, or brilliant, beam of radiation with highest intensities.

quDIS displacement and angle measurement for sample positioning in a beam line.
Schematic measurement setup for high-resolution positioning of crystalline samples for X-ray crystallography in a synchrotron beamline. The sample is rotated through several angles in a vacuum chamber with a goniometer while the detector measures the diffraction angles. The quDIS measures the distances between the fixed sensor heads and the sample surface and determines the positioned angles in a closed loop with the goniometer.

The X-rays in a beamline hit a crystalline sample and get diffracted by its lattice. By rotating the sample through several angles in a vacuum chamber while the X-ray detector measures the diffraction angles, the crystalline structure can be analyzed.

In this application, the quDIS displacement sensor measures the distances between the fixed sensor heads and the sample surface and determines the positioned angles of the sample. It measures the movement of the goniometer stage in a closed-loop setup with sub-nanometer accuracy.


Thermal deformation of a satellite in simulated space environment

A “classic” Cassegrain design used in space telescope
Schematic view of a “classic” Cassegrain design used in space telescopes: a parabolic primary mirror and a hyperbolic secondary mirror that reflect the light back down through a hole in the primary. Folding the optics makes this a compact design.

A space telescope is superior to a ground-based one because there is no light pollution or atmospheric aberrations, providing a more stable image, and offering unprecedented angular resolution over a large field. The disadvantages are the high costs and difficult maintenance, therefore the design and the construction must be very carefully prepared.

A Cassegrain reflector, like most large professional telescopes, has a parabolic primary mirror and a hyperbolic secondary mirror that reflects light back down through a hole in the primary. The mirrors and optical systems determine the final performance. Optical telescopes typically have mirrors polished to an accuracy of about a tenth of the desired wavelength.

quDIS longterm displacement measurement of the telescopes metering truss in a simulated space environment.
The design and the materials of the metering truss and it’s response to the harsh environments in space has to be tested on Earth. Enclosing the whole setup, controlling parameters like temperature and pressure and measuring the deformation by quDIS can simulate the operating conditions.

The metering truss, e.g. a graphite-epoxy frame, is the optical telescope assembly and keeps the working parts of the telescope firmly aligned. It must be able to withstand the frequent changes from direct sunlight to the darkness of the Earth’s shadow, resulting in large temperature fluctuations, and at the same time be stable enough to allow extremely accurate alignment of the telescope. It is surrounded by multi-layer insulation that keeps the temperature inside the telescope stable.

The design and materials of the measuring truss and its response to the harsh environment in space must be tested on Earth. By enclosing the entire structure, controlling parameters such as temperature and pressure, and measuring the deformation with multiple quDIS axes, the deformation can be determined under simulated conditions. In this case, twelve quDIS axes were used to measure the deformation of the cylindrical measuring truss in multiple directions with the highest precision and low drift over a long period of time.

Sensor Heads

All applications require different constrains for collimation, focusing and the beam profile, depending on their reflecting targets. The shaping of the laser beam is achieved by different sensor heads. All these sensor heads for quDIS are based on optical fibers, well-established in the telecommunication market.

Next to standard collimators and established focusing heads, qutools designs special heads for applications in harsh environments.

CB 2.3

Collimated beam, standard sensor head

quDIS Fabry-Pérot collimator with reference plane at the fiber end with an external mechanical stop.
quDIS Fabry-Pérot collimator with reference plane at the fiber end with an external mechanical stop.
Interferometer type Fabry-Pérot
Targets Mirror, retroreflector
Working range 20 … 5000 mm
Spot size (2w0) 2.3 mm @ 1600 mm
Angular tolerance ±34.0/±2.7 mrad
@50/1400 mm
Connector FC/PC


CB 2.3 APC

Collimated beam without reference reflex for individual usage

quDIS beam shaper, sensor head without a reference plane for collimated beams.
quDIS beam shaper, sensor head without a reference plane for collimated beams.
Interferometer type none – only beam shaping
Targets Mirror, retroreflector
Working range 20 … 5000 mm
Spot size (2w0) 2.3 mm @1600 mm
Angular tolerance ±34.0/±2.7 mrad
@50/1400 mm
Connector FC/APC


FF 50

Focused beam with fixed focal length

quDIS Fabry-Pérot sensor head with a fixed focal length at 50mm after the reference.
quDIS Fabry-Pérot sensor head with a fixed focal length at 50mm after the reference.

Interferometer type Fabry-Pérot
Targets Mirror, high reflective surface
Focal length 50 mm
Spot size (2w0) 0.5 mm
Connector FC/PC


FA 50-1400

Focused beam with adjustable focal length

quDIS Fabry-Pérot sensor head with an adjustable focal length between 50mm and 1.4 meters.
quDIS Fabry-Pérot sensor head with an adjustable focal length between 50mm and 1.4 meters.

Interferometer type Fabry-Pérot
Targets Mirror, high reflective surface
Focal length range 50 … 1400 mm
Spot size (2w0) <1 mm
Connector FC/PC


MI SR50:50

Michelson sensor head with different splitting ratios SR for different reflecting targets

quDIS Michelson sensor head with a collimated beam. The the second beam is reflected back at the side of the beamsplitter cube.
quDIS Michelson sensor head with a collimated beam. The second beam is reflected back at the side of the beamsplitter cube.
Interferometer type Michelson
Targets Mirror, retroreflector
Focal length range 50 … 1400 mm
Spot size (2w0) 2.3 mm
Beam splitting ratio 50:50, 80:20, 90:10
Connector FC/APC


MI OR SR50:50

Michelson sensor head with open reference and different splitting ratios SR

quDIS Michelson sensor head with a collimated beam and an open reference. The second beam is travels through the window on the side of the beam splitter cube.
quDIS Michelson sensor head with a collimated beam and an open reference. The second beam travels through the window on the side of the beam splitter cube.
Interferometer type Michelson, open reference
Targets Mirror, retroreflector
Focal length range 50 … 1400 mm
Spot size (2w0) 2.3 mm
Beam splitting ratio 50:50, 80:20, 90:10
Connector FC/APC

Accessoires and Upgrades

Distance Measurement

Determination of absolute distances within the wavelength range and compensation beam interruptions.

Ambient Measurement Unit (AMU)

Analysis of environmental parameters like temperature, pressure and relative humidity.
Failure correction, Measurement of refractive index.

quCATCH

Fibre coupling unit for fast and automatic laser coupling.
Quick calibration measurement even at separated locations.

Reflectors

Different reflector solutions: Retroreflectors, plane or parabolic mirrors.
Temperature caused deformation and signal stabilisation.

Downloads

quDIS brochure 11/2021 2.5 MB pdf
quDIS whitepaper 06/2020 0.9 MB pdf
quDIS manual 07/2022 1.4 MB pdf
quDIS datasheet 11/2021 0.1 MB pdf
quDIS AMU datasheet 09/2021 0.1 MB pdf