The interferometer

Basic principles[ edit ] Figure 2.

The interferometer

Basic principles[ edit ] Figure 2. Formation of fringes in a Michelson interferometer Figure 3. Colored and monochromatic fringes in a Michelson interferometer: Interference wave propagation Interferometry makes use of the principle of superposition to combine waves in a way that will cause the result of their combination to have some meaningful property that is diagnostic of the original state of the waves.

This works because when two waves with the same frequency combine, the resulting intensity pattern is determined by the phase difference between the two waves—waves that are in phase will undergo constructive interference while waves that are out of phase will undergo destructive interference.

Waves which are not completely in phase nor completely out of phase will have an intermediate intensity pattern, which can be used to determine their relative phase difference.

Most interferometers use light or some other form of electromagnetic wave.

Interferometry - Wikipedia Configuration[ edit ] Figure 2. Path of light in Michelson interferometer.
Michelson interferometer - Wikipedia Laser interferometry is a well established method for measuring distances with great accuracy.

Each of these beams travels a different route, called a path, and they are recombined before arriving at a detector. The path difference, the difference in the distance traveled by each beam, creates a phase difference between them.

It is this introduced phase difference that creates the interference pattern between the initially identical waves. This could be a physical change in the path length itself or a change in the refractive index along the path.

The fringes can be interpreted as the result of interference between light coming from the two virtual images S'1 and S'2 of the original source S. The characteristics The interferometer the interference pattern depend on the nature of the light source and the precise orientation of the mirrors and beam splitter.

If, as in Fig. If S is an extended source rather than a point source as illustrated, the fringes of Fig. Interferometers and interferometric The interferometer may be categorized by a variety of criteria: Homodyne versus heterodyne detection[ edit ] In homodyne detectionthe interference occurs between two beams at the same wavelength or carrier frequency.

The phase difference between the two beams results in a change in the intensity of the light on the detector. The resulting intensity of the light after mixing of these two beams is measured, or the pattern of interference fringes is viewed or recorded.

The heterodyne technique is used for 1 shifting an input signal into a new frequency range as well as 2 amplifying a weak input signal assuming use of an active mixer. A weak input signal of frequency f1 is mixed with a strong reference frequency f2 from a local oscillator LO.

These new frequencies are called heterodynes. Typically only one of the new frequencies is desired, and the other signal is filtered out of the output of the mixer. The output signal will have an intensity proportional to the product of the amplitudes of the input signals.

In this circuit, the incoming radio frequency signal from the antenna is mixed with a signal from a local oscillator LO and converted by the heterodyne technique to a lower fixed frequency signal called the intermediate frequency IF.

Michelson interferometer - Wikipedia

This IF is amplified and filtered, before being applied to a detector which extracts the audio signal, which is sent to the loudspeaker. Double path versus common path[ edit ] See also: Common path interferometer Figure 4. Four examples of common path interferometers A double path interferometer is one in which the reference beam and sample beam travel along divergent paths.

Examples include the Michelson interferometerthe Twyman-Green interferometerand the Mach-Zehnder interferometer. After being perturbed by interaction with the sample under test, the sample beam is recombined with the reference beam to create an interference pattern which can then be interpreted.

The interferometer

Other examples of common path interferometer include the Zernike phase contrast microscopeFresnel's biprismthe zero-area Sagnacand the scatterplate interferometer. Other examples of wavefront splitting interferometer include the Fresnel biprism, the Billet Bi-Lens, and the Rayleigh interferometer.

Two wavefront splitting interferometers InYoung's interference experiment played a major role in the general acceptance of the wave theory of light.

If white light is used in Young's experiment, the result is a white central band of constructive interference corresponding to equal path length from the two slits, surrounded by a symmetrical pattern of colored fringes of diminishing intensity. In addition to continuous electromagnetic radiation, Young's experiment has been performed with individual photons, [10] with electrons, [11] [12] and with buckyball molecules large enough to be seen under an electron microscope.

The result is an asymmetrical pattern of fringes. The band of equal path length, nearest the mirror, is dark rather than bright. InHumphrey Lloyd interpreted this effect as proof that the phase of a front-surface reflected beam is inverted.

Interferometer | Definition of Interferometer by Merriam-Webster

Other examples of amplitude splitting interferometer include the MichelsonTwyman—GreenLaser Unequal Path, and Linnik interferometer. A precisely figured reference flat is placed on top of the flat being tested, separated by narrow spacers.

The reference flat is slightly beveled only a fraction of a degree of beveling is necessary to prevent the rear surface of the flat from producing interference fringes.

The interferometer

Separating the test and reference flats allows the two flats to be tilted with respect to each other. By adjusting the tilt, which adds a controlled phase gradient to the fringe pattern, one can control the spacing and direction of the fringes, so that one may obtain an easily interpreted series of nearly parallel fringes rather than a complex swirl of contour lines.

Separating the plates, however, necessitates that the illuminating light be collimated.Interferometer definition, a device that separates a beam of light into two ray beams, usually by means of reflection, and that brings the rays together to produce interference, used to measure wavelength, index of refraction, and astronomical distances.


Interferometry (in this case “astronomical interferometry”) is a technique that astronomers use to obtain the resolution of a large telescope by using multiple smaller telescopes. For LIGO to operate at full sensitivity, its laser has to shine at kilowatts, but LIGO's laser enters the interferometer at most at Watts.

And just as it is impossible to build a km-long interferometer, building a kW laser is also a practical impossibility. interferometer - any measuring instrument that uses interference patterns to make accurate measurements of waves measuring device, measuring instrument, measuring system - instrument that shows the extent or amount or quantity or degree of something.

Interferometer definition is - an apparatus that utilizes the interference of waves (as of light) for precise determinations (as of distance or wavelength). an apparatus that utilizes the interference of waves (as of light) for precise determinations (as of .

Interferometer definition is - an apparatus that utilizes the interference of waves (as of light) for precise determinations (as of distance or wavelength). an apparatus that utilizes the interference of waves (as of light) for precise determinations (as of . The Michelson interferometer is a common configuration for optical interferometry and was invented by Albert Abraham Michelson. Using a beam splitter, a light source is split into two arms. Each of those light beams is reflected back toward the beamsplitter which then combines their amplitudes using the superposition principle. The EDU-MINT1 interferometer kit is designed to explore the experimental uses of a Michelson Interferometer, while the EDU-BT1 and EDU-QE1 analogy demonstrations are designed to explore concepts in quantum mechanics.

Young’s Double-slit Interferometer. A genius who started reading at the young age of two, Thomas Young (), was an English polymath who did a simple but unique experiment.

LIGO's Interferometer | LIGO Lab | Caltech