Interferometer
Laser interferometer is a high precision, accurate tool for fine distance measurement. At sub-nanometer level, it is finer then any other optical or mechanical gauges. Typical applications include machine tool calibration, motion system calibration and direct distance encoding for high performance positioning systems as shown in the following figure:
Interferometer detects distance by optical interference of two beams: reference beam and measurement beam. So when the DUT moves, phase changes occur in the measurement beam with respect to the reference beam resulting bright (in-phase) and dark (out-of-phase) fringe signals. Measurement resolution can be the counting of the dark-bright transitions at 1/2 laser wavelength or higher by interpolating the dark-bright fringe transition. Accuracy, on the other hand, is directly related to the laser wavelength accuracy. In high accuracy systems, ambient sensors are used to monitor media temperature, pressure and humidity to yield accurate distance measurement.
In typical motion systems rotary encoders or optical Linear Scales are often the means for position encoding and closed loop controls. The rotary or linear encoder is typically mounted in the base frame of a mechanical stage inches below the work object, therefore, hysteresis, backlash, creeping and pitch/yaw related positioning errors are often associated with such a system.
With interferometer, it can measure distance at the specific location of a work object, therefore, removing such effects. Unlike traditional interferometers, CMEI’s interferometer is a highly adaptable, solid-state laser interferometer. Besides the fine lasing wavelength that offers accurate, reliable distance measurement, it provides absolute measurement too. It is compact, long life and consumes little power making it ideal for encoder applications in fine motion systems while offering too the fine precision and accuracy for machine calibration applications. Furthermore, the CMEI interferometer generates a pair of encoder like quadrature (A-Quad-B) outputs at period half (or quarter) the optical wavelength directly portable to high precision, high accuracy motion control (encoding) system. It includes essentially a high accuracy “home” sensor.
CMEI laser based on ECL architecture
Using semiconductor lasers in an ECL configuration, the CMEI laser offers narrow lasing linewidth, i.e. high spectrum purity, high SMSR and low RIN. In addition, it is high output power with stable lasing wavelength. It is ideal not only for interferometry applications but also as sources lasers for telecom, medical, and other industrial applications as well.
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