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Unit for communication in scientific instruments
Hucl, Václav
We made device for communication between the computer and devices connected to the communication CAN (Controller Area Network) bus in the laboratory. This equipment generates four independent branches of the bus, which can communicate with each other, but short circuit, disconnection or other disorder in one of the branches does not affect the other three branches. Using the CANHUB card we can also interface devices connected CAN bus to a computer via USB or Ethernet. The hub consists of two AMIS-42770 integrated circuits. CAN/USB and CAN/Ethernet interface functionality is provided by a pair of Freescale 56F805 microcontrollers. The maximum communicating speed is 800 kbps while the devices in all braches of the bus must be set up to the same communication speed.
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System for stabilizing femtosecond lasers
Čížek, Martin
We describe a device intended for stabilizing optical frequency combs with respect to high-grade RF oscillators. The whole designed system is modular and can be adapted to actual conditions given mainly by level, frequency and signal to noise ratio of the processed signals. The device is based on a specialized integrated circuit (IC) that contains functional blocks for direct digital synthesis, digital phase detection, limiters, programmable dividers and control logic. The specialized IC is accompanied by specially developed control electronics based on a microcontroller that allows communication via CAN bus. This allows remote management of the whole system and integrating it into complex automated experiments with optical frequency synthesizers. The device is used for stabilizing offset or repetition frequency of the optical frequency comb. To ensure best possible conditions for a fast first-order controller the setup is extended by a slower second-order controller with a high dynamic range. This second-order controller is built around a specialized 18-bit AD/DA card and a software application in LabView environment. The bandwidth of the closed control loop can be up to single MHz. The only limiting factor is the tuning speed of the femtosecond laser.
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Nano-stage with a large range of positionig for AFM microscopy
Číp, Ondřej
We present a new concept of long-range positioning stage for scanning probe microscopy. We developed the stuck planchet moving stage where X-Y axes of positioning are controlled by two incremental piezoelectric actuators. We demonstrated moving range up to 7 mm of positioning in both axes. The absolute position of the stage is measured by two optical linear encoders. The resolution of the positioning is about 10 nm.
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Active Angular Alignment of Gauge Blocks in Double-Ended Interferometers
Buchta, Zdeněk
This paper presents a method implemented in a system for automatic contactless calibration of gauge blocks designed at ISI ASCR. The system combines low-coherence interferometry and laser interferometry, where the first identifies the gauge block sides position and the second one measures the gauge block length itself. A crucial part of the system is the algorithm for gauge block alignment to the measuring beam which is able to compensate the gauge block lateral and longitudinal tilt up to 0.141 mrad. The algorithm is also important for the gauge block position monitoring during its length measurement.
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Raman tweezers: principle and applications
Bernatová, Silvie ; Samek, Ota ; Pilát, Zdeněk ; Ježek, Jan ; Kaňka, Jan ; Šiler, Martin ; Zemánek, Pavel
Raman tweezers combines the optical trap for non-contact micromanipulation of micro-objects with Raman spectroscopy for chemical analysis of the sample. This combination presents an efficient tool for concurrent spectroscopic analysis of chemical composition and micromanipulation allowing sorting or probing of mechanical properties of the sample. Raman tweezers were successfully used for example in characterization of biomolecules like DNA, for sorting of cells and investigation of the link between their chemical and mechanical properties.
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Advanced Laser Measuring Systems in Nanometrology
Lazar, Josef ; Hrabina, Jan ; Holá, Miroslava ; Vychodil, M.
We present a development of a nanometrology system combining local probe microscopy and precise positioning and measuring in the nanoscale. The positioning operates in short range with a focus on precision; displacement measurement controls the sample stage in six degrees of freedom with high-resolution interferometry. The system is designed to operate as a national standard for nanometrology. The contribution presents collaborative work with Meopta company.
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Multidimensional interferometric measuremenr system for AFM microscopy - national standard for nanometrology
Hrabina, Jan
We present the design and performance characteristics of 6-axis interferometric measurement system for local probe microscopy. Described measurement tool was developed in colaboration with the Czech Metrological Institute in Brno and it is intended to solve as a national nanometrological standard. The system in based on a commercial nanopositioning sample table controlled by piezoelectric transducers, a metrological frame and a laser interferometric setup for dimensional measurements in six degrees of freedom.
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Detection standing wave within Fabry-Perot Cavity
Holá, Miroslava
This contribution follows up with project Interferometry with compensation of the refractive index of air. This inteferometric technique was based on differential interferometry setup for measurement in the subnanometer scale in atmospheric conditions. One of the important limiting factor in any optical measurement are fluctuations of the refractive index of air representing a source of uncertainty on the 10-6 level when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of overdetermined interferometric setup where the reference length is derived from a mechanical frame made from a material with very low thermal coefficient on the 1*E-8 level (Zerodur - Schott). The optical setup consists of three interferometers sharing the same beam path where two measurement differentially the displacement while the third evaluates the changes in the measuring range acting as a tracking refractometer. The concept of stabilization of wavelength against the mechanical reference is realized within passive Fabry-Perot cavity. The link between the wavelength and mechanical reference here is in principle simple, the laser optical frequency has to be locked to the resonance of the passive cavity either through tracking the transmission maximum or reflection minimum. The key component for position sensing inside of a passive Fabry-Perot cavity is low-loss transparent photodetector. The transparent photodetector made in cooperation with Institute of Physics of the ASCR - Department of Thin Films and Nanostructures (work group A. Fejfar). Transparent photodetector is made of fused silica substrate, active photo resistive silicon layer with side titanium electrode and a set of antireflection coatings optimized for minimum reflectivity. Optimized AR coating for 532 nm.
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