FAQ's

Yes, as it uses the same hardware and software platform. Also an upgrade of a single wave to spectroscopic ellipsometer is possible.

Yes! BAM operation is a "subset" of the imaging ellipsometer. However, applicability of an imaging ellipsometer as a BAM depends on the laser power. We recommend at least 20mW, better 50mW lasers when using the imaging ellipsometer as a BAM is intended.

In the imaging ellipsometer, the polarization state of the light beam in front of the polarizer (P) is made circular to provide constant output regardless of the P angle position. This means that ca. half of the power is lost in the polarizer for the imaging ellipsometer.
The EP³-BAM uses the near p-polarization of the laser without alteration, because for BAM operation P is always close to 0 deg. Thus, the "efficiency" in terms of laser power is twice as high compared to the imaging ellipsometer.

There are many different ellipsometry methods. The idea is always the same: analyze how the state of polarization is altered due to reflection caused by the sample. Thus, this information characterizes the sample.

We use nulling ellipsometry for 3 reasons:
a) Nulling ellipsometry allows one to make the image "dark" at a certain region of the sample. If there is a difference in the optical properties of the sample, those other regions are "bright", because the nulling conditions are not fulfilled for those regions. Thus, we get a contrast that may be directly visualized by a camera. This is what we call "real-time ellipsometric contrast".
b) Nulling ellipsometry is very sensitive compared to other methods, thus giving high contrast, especially for very thin films.
c) Nulling ellipsometry offers the ability to measuring in four zones => for isotropic materials, the expected result after rotating a polarizer, compensator or analyzer 180 ° is the same as without rotation. There are four possible combinations of polarizer/compensator and compensator/analyser that give the same result. The advantage of this is that the average is, to a large extent, free of systematic errors.

In principle one could also use many other methods in an imaging system. But this would have several disadvantages: for example in "rotating analyzer" elli, one rotates the analyzer constantly. This
means that the image would be very bright most of the times, and only sometimes it gets a little darker. Thus, the sensitivity is not very high for very thin films. Also, one needs a very high dynamic range camera and very linear camera response. Several images have to be collected and then the final image is recalculated from
this by lengthy fourier transform. This is not "real-time", thus the convenience of our fast imaging is not available in such a system. This latter point is true for most non-nulling types of ellipsometers.

The disadvantage of the nulling concept is that the "measurement" of a precise ellipsometric value on one spot takes longer, because nulling requires a more complex movement of some optical components.

Imaging ellipsometry, in contrast to scanning ellipsometry, is based on analyzing ellipsometric contrast micrographs at different positions of the optical components to obtain a delta and psi – map. This procedure is the reason for the unique lateral resolution of imaging ellipsometer and the short measurement time in comparison to scanning methods. The laser spot has to illuminate the complete field of view. In case of 2x objective a beam expander is needed to fulfill this requirement.

The camera is digitized with 8 bits. However, sometimes less is more. The bit depth does not not limit the measurement process, nor the linearity, but it has a positive effect on the data transfer. Please note that the measurement is not "photometric" in our system in the sense that we do not use the camera signal directly. It is important to stress this because competitors use 14bit cameras in a completely different ellipsometric measurement procedure. Therefore, their data quality is not higher than ours, regardless of the camera bit depth. If you want to compare – please have a look at the results – you are invited to send us a sample for a contest!

Yes, the database may be upgraded very easily if n and k data and dispersion function, resepectivly are available. Also the results of optical modeling can be saved as a new material.

It really depends on your equipment, the environmental conditions and the aim of your work. If you have the impression that vibrations are disturbing your system, give us a call and ask for a site evaluation. In most cases we will find a solution for your setup.

Vibrations in a laboratory or production building are often generated by running machinery like pumps and motors. In addition, HVAC equipment and the traffic passing nearby can be a source of vibrations. Last but not least wind and seismic activity can affect the building structure at low frequencies.

Passive vibration isolation is based on the mechanical low pass characteristic of a spring-mass-damper setup. A passive isolator reduces the ambient vibration for frequencies above its resonance. Within the resonance the vibrations get amplified!
For this reason passive isolation systems require a big mass, e.g. a heavy granite block, and soft springs with good damping, e.g. air springs, in order to achieve a low resonance frequency (typically 2 to 5 Hz). The amplification within the resonance and the long settling time after impacts are the drawback of passive isolators.

Active vibration isolation measures and counteracts the vibration in a closed loop feedback system. Therefore, a resonance at the systems Eigenfrequency is eliminated, keeping your equipment well isolated even at low frequencies above 0.7 Hz.

Yes, in most cases. The Accurion Halcyonics systems start isolating as low as 0.7 HZ, so the resonance vibrations around 2 to 5 Hz inherent in passive systems are avoided.

The Halcyonics systems dampen the vibration level up to 40 dB (99.0%) above 10 Hz in most cases. To verify this, Accurion has a vibration measuring tool that will visualize the current level of vibration at your site. With this data printed out as a graph we will discuss the possibilities and the results you can expect. Please call or write to arrange for a vibration analysis at your site.

Certainly! At Accurion, we think that the most demanding and exacting test is the one under the real conditions found in a customer’s environement. Just call or write for a demo.

Yes, there are technical limits.
a) Limits for heavy loads and/or high vibration amplitudes:
the electromagnetic actuators used in the active isolation system provide a limited force and stroke. For heavy loads and/or high vibration amplitudes it might happen that force or stroke of the actuators is not big enough to compensate the vibration
b) Limits for very small amplitudes:
the sensors used in the active system provide a limited sensitivity. Especially for low frequencies the sensitivity decreases rapidly. In a very calm environment it might happen that the vibration level is below the sensitivity of the sensor. In this case there will be no isolation.

As a standard feature a software solution and an USB cable is included with every Micro and Vario systems, so you can switch the isolation on and off from your computer.

The Halcyonics_Micro and Workstation Series come with a flat top surface. As an option we offer tapped top plates with ¼”-20 threads on 1” centres or alternately M6 on 25 mm centres. In addition, customer specific drill and tap patterns are possible.

Accurion’s Halcyonics department has developed acoustic enclosures to prevent sound and air currents from interference with sensitive instruments. These covers may be used with the active vibration isolation units or as stand-alone systems.

Accessories to the active vibration isolation systems include rigid support frames, the acoustic covers and a vibration analysis tool named the “Explorer”. Other Accessories may be manufactured to match our customers’ needs.

There is no service interval. After the 48-hours endurance test the systems are calibrated and sealed to run 24 hours a day, 365 days a year. By design there are no serviceable parts on the active vibration isolation systems except the fuses which protect the electronics from excess voltage surges.

Halcyonics choose to go this way to avoid actuators based on piezoelectric elements. Although these components allow for precise and rapid positioning in many fields of technology, the naturally small amplitudes necessitate high driving voltages. Besides possible interference with the sensitive instruments atop an active vibration isolation system, the high electric potential in the range of several hundred Volts will increase efforts in safety related design changes and tests for CE conformity (a kind of safety regulation for the consumer in the EC). In addition, a resonance is observed with piezo actuators as it is with pneumatic systems, although at different frequencies and amplitudes.
 
The R&D department of Halcyonics was able to develop an improved electromagnetic actuator that is equipped with a magnet made of a Neodymium based material rather than a Ferritic. The former shows a much stronger magnetic field in relation to mass and size, so that the complete actuator unit could be made much smaller and less heavy than its predecessor and still working at a convenient voltage of only 24 VDC.

Although we try to offer matching answers to the most frequently asked questions, there are some which we have not heard of.
Please contact us per e-mail.

When the company Halcyonics was founded in 1997, one of the partners suggested the name. Its origins go back to the Greek mythological figure Alcyone, one of the Plejades and daughter of Aeolus, the god of winds.

She was married to Ceyx, king of Thessaly, who went one day on a voyage on a ship. Since he and his wife had angered Zeus, the god killed Ceyx by sending a thunderstorm, drowning Alcyones husband.

When she learned about the fate of her companion, she threw herself from the cliff into the sea to join Ceyx in death. The gods had pity with the couple and turned the lovers into Halcyon birds, which have their names from the same Alcyone character.

When the couple, now as birds, returned back to shore, Alcyones father Aeolus calmed the seas to allow them to build a nest in safety. In the eastern part of the Mediterranean Sea the time around the end of the year, when the wind has calmed and the sea is flat, is still named the "Halcyon days." This term has found its way into general language, describing a calm and peaceful time in general.

Halcyonics active vibration isolation systems provide the scientists of the modern days with a calm surface, independent of the time of the year, without sacrificing themselves or a family member.

For more information about the Greek mythology character of Alcyone, see:
http://en.wikipedia.org/wiki/Alcyone

and on the Halcyon birds, the Kingfisher:
http://en.wikipedia.org/wiki/Tree_kingfisher