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Related Concept Videos

Displacement Current01:19

Displacement Current

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Ampère's law, in its usual form, does not work in places where the current changes with time and is not steady. Thus, Maxwell suggested including an additional contribution, called the displacement current, Id, to the real conduction current I.
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Position and Displacement01:31

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The position of an object defines its location relative to a convenient frame of reference at any particular time. A frame of reference is an arbitrary set of axes from which the position and motion of an object are described. Earth is often used as a frame of reference, and we often describe the position of an object as it relates to stationary objects on Earth. For example, a rocket launch could be described in terms of the position of the rocket with respect to Earth as a whole. On the other...
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Position and Displacement Vectors01:00

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To describe the motion of an object, one should first be able to describe its position (where it is at any particular time). More precisely, the position needs to be specified relative to a convenient frame of reference. A frame of reference is an arbitrary set of axes from which the position and motion of an object are described. Earth is often used as a frame of reference to describe the position of an object in relation to stationary objects on Earth.
Further, several important kinds of...
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Significance of Displacement Current01:27

Significance of Displacement Current

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A displacement current is analogous to a real current in Ampère's law, participating in Ampère's law the same way as the usual conduction current. However, it is produced by a changing electric field. Displacement current is defined in terms of a time-varying electric field, and also has an associated displacement current density. By adding a term accounting for displacement current, Maxwell modified the existing Ampère's law, which is now called generalized Ampère's law.
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Angular Velocity and Displacement01:08

Angular Velocity and Displacement

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Uniform circular motion is motion in a circle at a constant speed. Although this is the simplest case of rotational motion, it is very useful for many situations and is used to introduce rotational variables. When a particle is moving in a circle, the coordinate system is fixed and serves as a frame of reference to define the particle’s position. Its position vector from the origin of the circle to the particle sweeps out the angle θ, which increases in the counterclockwise direction...
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Frequency-dependent Selection01:21

Frequency-dependent Selection

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When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness.
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Polydyne displacement interferometer using frequency-modulated light.

Masoud Arablu1, Stuart T Smith1

  • 1Center for Precision Metrology at UNC Charlotte, Charlotte, North Carolina 28223, USA.

The Review of Scientific Instruments
|June 6, 2018
PubMed
Summary
This summary is machine-generated.

This study introduces a polydyne displacement interferometer using a frequency-modulated (FM) signal to diffract a laser beam. The new method achieves sub-50 nm displacement measurement accuracy compared to a reference interferometer.

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Area of Science:

  • Optics and Photonics
  • Metrology and Measurement Science

Background:

  • Acousto-Optic Modulators (AOMs) are used for laser beam manipulation.
  • Interferometry is a key technique for precise displacement measurements.

Purpose of the Study:

  • To develop and validate a novel polydyne displacement interferometer.
  • To assess the accuracy and stability of the new interferometer design.

Main Methods:

  • Utilizing a frequency-modulated (FM) signal to diffract a He-Ne laser beam via an Acousto-Optic Modulator (AOM).
  • Employing a Michelson interferometer topology with a polydyne displacement interferometer setup.
  • Measuring displacement via phase analysis of synchronized harmonic pairs derived from discrete Fourier transform (DFT) of photodetector signals.

Main Results:

  • Displacement measurements showed less than 50 nm difference compared to a commercial heterodyne interferometer for scans up to 10 μm.
  • Drift tests indicated environmental factors (temperature, pressure, humidity) and Abbe/thermal expansion effects contribute to deviations.

Conclusions:

  • The polydyne displacement interferometer demonstrates high accuracy for displacement measurements.
  • Environmental factors and physical effects must be considered for optimal performance and error analysis.