What is the difference between localized and non localized interferometry of Michelson interferomete

The differences are as follows: 1. The definitions are different.

Localized interference: In the overlapping region of coherent light waves, the interference fringes are only distributed in certain places in the interference region, then this interference is localized interference. Non-localized interference: In the overlapping region of coherent light waves, there are interference fringes everywhere, then this interference is non-localized interference.

2. Different regions.

Localization is a certain region, and despite the use of an extended light source, clear interference fringes can still be observed The area where clear interference fringes can be observed is called a localized area, and non-localized is any region of space.

3. The interference conditions are different.

Localization of interference: In the overlapping region of the coherent optical wave field, due to the influence of temporal coherence and spatial coherence, the distribution area of the interference fringes will be affected by different interference conditions.

The interference fringes produced by point source illumination are non-localized interference, and the light emitted by the two imaginary coherent point sources formed by reflection is coherent in the whole space, similar to water wave interference, that is, the interference fringes can be seen at any point in space, so it is called non-localized interference.

The interference fringes illuminated by the extended light source are localized interference, e.g., the isoinclined fringes are localized at infinity and can only be imaged in the back focal plane with a convex lens or directly observed with the human eye. Equal-thickness fringes are localized at the junction of the virtual image of one reflective surface and the other reflective surface, and can only be observed by imaging with a convex lens.

Directly use the laser plus beam expander to interfere without frosted glass before interference, and then observe on the frosted glass screen after interference, which is the easiest to adjust and observe

Localization is actually the intersection of two beams that you want to interfere with. For example, in the case of isotilt interference, two reflectors are required to be parallel, and the coherent light reflected back at the same angle is parallel, then their intersection is infinite, and only the convex lens can be used to converge within a limited distance, or the annular fringes can be seen by direct observation by the eye.

Its inventor was American physicist Albert Abraham Michelson. The principle of the Michelson interferometer is that an incident light beam is divided into two beams by a beamsplitter and then reflected back by the corresponding plane mirror, because the two beams of light have the same frequency, the same direction of vibration, and a constant phase difference (i.e., the interference condition is satisfied), so interference can occur.

The different pathlengths of two beams of light in interference can be achieved by adjusting the length of the interference arm and changing the refractive index of the medium, so that different interference patterns can be formed. Interference fringes are equal path path trajectories, so to analyze the pattern produced by a certain interference, it is necessary to find a function of the position distribution of the optical path difference of coherent light.

The difference between so-called localized and non-localized interference is that the interference is not confined to certain regions of space.

If the interference fringes are limited to certain regions of space, then it is localized interference, such as if the light source uses an extended light source. If the interference fringes appear in all areas of space, it is alocal interference, such as using a point light source.

For the observation method, the non-localized interference of the observation point light source can be observed directly with the screen, and the localized interference of the extended light source needs to be placed in front of the screen to gather the light on the screen to observe the interference.

An interferometer is a precision instrument that relies on the principle of light interference to measure length or length change. Commonly used in laboratories is the Michelson interferometer, which is an instrument that uses the partial amplitude method to generate two beams of light to achieve interference. This experiment is to introduce the principle, structure and preliminary adjustment method of Michelson interferometer, and use it to verify the characteristics and change law of equal inclination and equal thickness interference fringes produced by the partial amplitude method introduced in university physics, and learn to measure the wavelength of laser with the method of measuring the length of the interferometer.

Michelson interferometers consist mainly of beamsplitters, compensating plates, and two flat mirrors (one fixed and one removable, mounted on two arms perpendicular to each other). When the two mirrors are perpendicular, the isotilt interference fringes can be observed; When the two mirrors are at a small angle to each other, the interference fringes of equal thickness can be observed. For an isotropic interference fringe, it is a set of concentric rings alternating light and dark.

When the distance between the two plane mirrors changes, the phenomenon of annular fringes "gushing" or "trapping" from the center can be observed, and the density of the fringes changes, and whenever the distance between the two plane mirrors changes by half a wavelength, there will be a toroidal fringe "gushing" or "trapping" from the center, so as long as the number of annular fringes "gushing" or "trapping" and the distance of the two mirrors are recorded, the wavelength of the light source can be measured. For the interference fringes of equal thickness, it is a set of linear fringes with light and dark, and the fringes appear to bend with the change of the distance between the two plane mirrors, which can be observed experimentally.

An interferometer is a precision instrument, and its minimum index can be achieved, so it should be used with care. Do not touch the optical surface of various mirrors with your hands or other things; When adjusting the handwheel screw, the action should be gentle, not strong torsion, strong plate, not adjustable too tight, so as not to deform the mirror; The handwheel can only be rotated in one direction during the measurement, and the beginning and end readings should be taken when the **bright spot is maximum; The reading is composed of three parts: the main ruler, the big wheel, and the small wheel, the main ruler and the large wheel are not estimated, and the small wheel can be read and estimated.