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— Laser interferometers have found wide usage in a variety of precision measurement applications. The ability to gain precise position information with minimal change to the dynamics of the device being measured has a large set of advantages. This allows interferometer systems to be used in feedback loops for precision systems. This paper presents a tutorial on laser interferometers, their use in precision motion feedback systems, the issues faced by such systems, and some of the solutions that have been applied to these issues.
Optical Engineering, 2001
We review laser diode feedback interferometry as a general tool for sensing applications. After outlining the basic principles and the theoretical approaches used to describe the phenomenon, we present a few selected examples of applications in interferometry, as developed by various groups in recent years, such as a displacement sensor, a velocimeter or vibration sensor, and an absolute distance meter or range finder and angle sensor. Experimental results are also reported as an illustration.
Sensors
A robust laser measurement system (LMS), consisting of a sensor head and a detecting part, for simultaneously measuring five-degree-of-freedom (five-DOF) error motions of linear stages, is proposed and characterized. For the purpose of long-travel measurement, all possible error sources that would affect the measurement accuracy are considered. This LMS not only integrates the merits of error compensations for the laser beam drift, beam spot variation, detector sensitivity variation, and non-parallelism of dual-beam that have been resolved by the author’s group before, but also eliminates the crosstalk errors among five-DOF error motions in this study. The feasibility and effectiveness of the designed LMS and modified measurement model are experimentally verified using a laboratory-built prototype. The experimental results show that the designed LSM has the capability of simultaneously measuring the five-DOF error motions of a linear stage up to one-meter travel with a linear error ...
10th Int. Particle Accelerator Conf. (IPAC'19), Melbourne, Australia, 19-24 May 2019, 2019
To perform experiments on the nanometer scale at high brilliant x-ray light sources, it is highly recommended to have the mechanical components of the experiment, like lenses, mirrors and samples, as stable as possible. Since these components need to move from nanometer up to millimeter range they cannot be stabilized by only using rigid structures. For that reason an active stabilization system with fast and precise sensors needs to be developed. Here a Laserinterferometer is used, which provides picometer resolution at several MHz sample rate. In this paper we will present a laboratory setup which consists of a 6-slot Micro Telecommunication Computing Architecture generation 4 (MTCA.4) crate with standard components such MicroTCA carrier hub (MCH), central processing unit (CPU), power supply (PS) and cooling unit (CU). The Interferometer application has been setup with Deutsches Elektronen-Synchrotron (DESY) advanced mezzanine card (DAMC-FMC20) data processing unit, DESY Field Programmable Gate Array (FPGA) mezzanine card (DFMC-UNIO) universal input and output extension and DESY rear transition module (DRTM-PZT4) piezo driver. The encoder signals given by the interferometer controller are processed within the FPGA and then forwarded to the piezo amplifier RTM-board. The signal processing application includes decoding the digital feedback signal, calculating the coordinate transform for specific experimental setups and closed-loop operation based on a proportional integral derivative (PID) controller. The first results of the laboratory setup are demonstrated and briefly discussed.
Mechanism and Machine Theory, 2005
This paper presents a systematic approach for representing and estimating the Cartesian positioning errors of robot manipulators with analytical functions such as Fourier polynomials and ordinary polynomials. A Motoman SK 120 robot manipulator was employed as an experimental system to evaluate the efficacy of the approach. As a complementary part of this evaluation process, the kinematic parameters of the experimental system are also identified. The position data needed throughout this study were provided by a laser-based dynamic measurement system. The coefficients of the polynomials and the kinematic parameters are determined using the position data for a number of identification configurations. The proposed approximation and estimation approach is verified experimentally for three exemplary Cartesian space trajectories, which describe different configurations of the manipulator. The errors estimated through the polynomials are then corrected using a first-order approximation of the inverse kinematic model. The numerical and experimental results prove that the analytical functions are accurate enough to estimate manipulator position errors without needing further experimental data. The principal conclusion is that our approach of estimating position errors with some analytical functions is practical and generic, and most importantly it is effective enough to improve robot accuracy.
Optics and Laser Technology, 2001
In this paper, the displacement of an object is measured with a photothermal phase-modulating laser diode interferometer. A feedback control system is designed to reduce the measurement errors caused by the uctuations in the optical wavelength of the laser diode and the vibrations of the optical components in the interferometer. A new method is proposed to enlarge the measuring range of displacement. Using this method, the measuring range is enlarged from half wavelength to nearly 125 m and the measurement accuracy is about 1 nm. The simulation and experimental results have shown the usefulness of the method and the feedback control system.
The International Conference on Electrical Engineering, 2012
Motion control system is a system that has a special controller for controlling position, velocity or acceleration. In this paper the position control is concerned. A special application is introduced in detail which is the "gonio-photometer" laboratory which is used to measure the following: a-Luminaire luminous intensity distribution. b-Lamp luminous flux. Position control of this application is concerned having a resolution angle (0.01 degree) with the aid of a dc servo motor system and PID controller in addition to the use of brakes for maintaining better results. Simulation and calculations of the system equations are held using Matlab program. An alternative method is introduced for the position control of the application under study, which is the use of stepper motors instead of dc servo motors.
AIAA Journal, 1995
A dual beam differential laser interferometer/vibrometer measurement system was developed for studying the steady-state and dynamic behavior of low-weight high-performance mechanical systems. This newly developed optical system employs many optical and mechanical design tactics to achieve design targets such as nanometer displacement accuracy, ease of use, capability of measuring untreated structural surfaces, high-measurement bandwidths, and large-dynamic ranges. Both the optical/mechanical configurations and the design approaches adopted are discussed in detail. A flying slider and thin-film disk system currently used in the disk drive industry were used as the testbed to verify the capabilities of this newly developed nanometer structural displacement/velocity measurement system.
2010
Abstract A low-cost interferometer for piezoelectric actuator (PEA) displacement and velocity feedback was developed and described here. An initial design employed a single photodiode as a sensing element. Although fringes could be measured successfully, to obtain the direction of displacement, the PEA control input was needed. A low-cost interferometric encoder is developed that employs a pair of silicon photodiodes and a manual micropositioner stage.
Optics Communications, 2004
The potential advantages of chirped pulses for very precise measurement of distance, through frequency-domain ranging, has prompted consideration of frequency shifted feedback (FSF) lasers as sources of interferometer light. We here derive theoretical limitations to the spatial accuracy one can expect in such applications, by considering analytical expressions for the electric field emerging from a frequency shifted feedback (FSF) laser seeded by a CW laser whose finite bandwidth originates in phase fluctuations. We also consider consequences of fluctuations in cavity size. We show that, for surfaces flat within the laser footprint, such a system can provide the subwavelength accuracy of conventional interferometry but without dependence on material-dependent phase shifts. Although noise has been important for previous uses of FSF lasers in optical ranging and interferometry, we here show that a frequency modulated seeding laser can be used to better advantage than noise.
IEEE Transactions on Instrumentation and Measurement, 1996
Ab.~tract-We describe a laser-diode feedback interferometer for displacement measurements with directional discrimination and resolution better than m. This new, compact instrument consists of a small optical head and a signal processing board, which is interfaced to a personal computer. The prototype developed has a dynamic range of 2 m and an accuracy of about 5 pmlm, using a corner cube as a remote reflector. Thanks to PC interfacing, the displacement is directly available in metric units and errors due to temperature fluctuations can be corrected with software signal processing.
Sixth International Symposium on Precision Mechanical Measurements, 2013
Any linear stage has inherent geometrical errors due to manufacturing errors. The induced Abbé errors have to be compensated for the accuracy of positioning. In addition, although the commercial laser interferometer is capable for the displacement sensing to nanometer resolution, it is, however, bulky in size, expensive in cost and not able to correct the Abbé errors caused by angular errors of the moving stage. In order to minimize and simplify the interferometer as a practically useful sensor for nanopositiong stages in industrial use, this paper presents a newly developed miniature multi-degree-of-freedom measurement system (MDFMS), which is constructed by a wavelength corrected Michelson interferometer and a dual-axis autocollimator. The wavelength correction of the miniature laser interferometer is calibrated by SIOS and controlling the temperature within ±2 ºC, the wavelength stability is less than 10 -6 . After calibration, the accuracy of the miniature laser interferometer can reach 32 nm for the travel of 20 mm long. The collimator has accuracy of ±0.3 arc-sec within the range of ±30 arc-sec. This MDFMS has been integrated into the developed Micro-CMM as a feedback sensor in each axis of the coplanar stage.
IEEE Transactions on Instrumentation and Measurement, 2001
A low-cost laser sensor using optical feedback interferometry has been designed to measure velocities. With digital signal processing based on an order two autoregressive model of the optical power, an inaccuracy of about 0.5% can be reached.
Applied Sciences
This paper presents a miniature three-degree-of-freedom laser measurement (3DOFLM) system for displacement feedback and error compensation of a nanopositioning stage. The 3DOFLM system is composed of a miniature Michelson interferometer (MMI) kit, a wavelength corrector kit, and a miniature autocollimator kit. A low-cost laser diode is employed as the laser source. The motion of the stage can cause an optical path difference in the MMI kit so as to produce interference fringes. The interference signals with a phase interval of 90° due to the phase control are detected by four photodetectors. The wavelength corrector kit, based on the grating diffraction principle and the autocollimation principle, provides real-time correction of the laser diode wavelength, which is the length unit of the MMI kit. The miniature autocollimator kit based on the autocollimation principle is employed to measure angular errors and compensate induced Abbe error of the moving table. The developed 3DOFLM sy...
Mapan-journal of Metrology Society of India, 2010
The present era is witnessing advancement in digital electronics and microprocessor which enables manufacturing sector capable to produce complex components within small tolerance zone in the tune of nanometre and at one machining center. All motion control systems have some form of position feed back system fitted with the machine. Such systems are not generally accurate due to the errors in the positioning performance of the machine tool which will change over time to time due to wear, damage and environmental effects. The complex structure of multi-axis CNC machine tools produce an inaccuracy at the tool tip caused by kinematic parameter deviations resulting in manufacturing errors, assembly errors or quasi-static errors. Analysis of these errors using a laser measurement system provides the manufacturers a way to achieve better accuracy and hence higher quality output from these processes. In this communication, techniques to measure the linear positional errors of axes of CNC machine tools by a laser interferometer calibration system and accuracy enhancement using the data obtained from the calibration cycle by feeding into the machine’s controller with the help of linear error compensation package are discussed.
Robotics and Computer- …, 2003
Laser tracking systems (LTSs) employ tracking laser interferometers for coordinate measuring of precision machine tools and robots. Such coordinate measuring machines, if properly calibrated, are potentially fast, very accurate and can cover a large workspace. ...
2019
To perform experiments on the nanometer scale at high brilliant x-ray light sources, it is highly recommended to have the mechanical components of the experiment, like lenses, mirrors and samples, as stable as possible. Since these components need to move from nanometer up to millimeter range they cannot be stabilized by only using rigid structures. For that reason an active stabilization system with fast and precise sensors needs to be developed. Here a Laserinterferometer is used, which provides picometer resolution at several MHz sample rate. In this paper we will present a laboratory setup which consists of a 6-slot Micro Telecommunication Computing Architecture generation 4 (MTCA.4) crate with standard components such MicroTCA carrier hub (MCH), central processing unit (CPU), power supply (PS) and cooling unit (CU). The Interferometer application has been setup with Deutsches Elektronen-Synchrotron (DESY) advanced mezzanine card (DAMC-FMC20) data processing unit, DESY Field Pro...
Classical and Quantum Gravity
Large frame ring laser gyroscopes are top sensitivity inertial sensors able to measure absolute angular rotation rate below prad/s in few seconds. The GINGER project is aiming at directly measuring the Lense-Thirring effect with an 1% precision on an Earth based experiment. GINGER is based on an array of large frame ring laser gyroscopes. The mechanical design of this apparatus requires a micrometric precision in the construction and the geometry must be stabilized in order to keep constant the scale factor of the instrument. The proposed control is based on square cavities, and relies on the length stabilization of the two diagonals, which must be equal at micrometric level. GP2 is the prototype devoted to the scale factor control test. As a first step, the lengths of the diagonals of the ring cavity have been measured through an interferometric technique with a statistical accuracy of some tens of nanometers, and they have been locked to the wavelength of a reference optical standard. Continuous operation has been obtained over more than 12 hours, without loss of sensitivity. GP2 is located in a laboratory with standard temperature stabilization, with residual fluctuations of the order of 1 • C. Besides the demonstration of the control effectiveness, the analysis of the Sagnac frequency demonstrates that relative small and low-cost ring lasers (around one meter of side) can also achieve a sensitivity of the order of nrad/s in the range 0.01−10 Hz in a standard environment, which is the target sensitivity in many different applications, such as rotational seismology and next generation gravitational waves detectors.
Sixth International Conference on Education and Training in Optics and Photonics, 2000
This paper reviews the theoretical basis of two laser interferometry vibration measuring methods of high accuracy, i.e., frequency ratio and Bessel function minimum point. These techniques are used for low and high vibration frequencies, respectively. The most recent experimental developments are highlighted and contributions to the classic models are shown.
Applied Optics, 2013
Laser interferometers have been widely implemented for the displacement sensing and positioning calibration of the precision mechanical industry, due to their excellent measuring features and direct traceability to the dimensional definition. Currently some kinds of modified Fabry-Perot interferometers with a planar mirror or a corner cube prism as the measurement mirror have been proposed. Each optical structure of both models has the individual particularity and performance for measuring applications. In this investigation, a multi-interferometric displacement system has been proposed whose measurement mirror can be quickly and conveniently altered with a planar mirror or a corner cube reflector depending on the measuring demand. Some experimental results and analyses about the interpolation error and displacement measurements with both reflectors have been demonstrated. According to the results, suggestions about the choice of a measuring reflector and interpolation model have been presented. With the measuring verifications, the developed system with a maximum standard deviation less than 0.2081 μm in measuring range of 300 mm would be a compact and robust tool for sensing or calibrating the linear displacement of mechanical equipment.
International Conference on Space Optics — ICSO 2016, 2017
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