There are many types of interferometers. Here are the five most common interferometers.

The first is the Newton Interferometer Newton Interferometer

The Quasimonochromatic point source on the left is a point source with a nearly single wavelength. Quasimonochromatic means single wavelength, and point source is point source.

After the point source passes through the lens and becomes parallel light, it hits the lower elliptical object to be tested. The object to be tested may be an object such as a lens, and the plane under the object to be tested is a reference plane, which is usually used as a reference surface. The flatness, that is, the Surface irregularity, must be 1/10λ or more. The larger the denominator, the better the flatness.

The second is the Michelson Interferometer.

When the Michelson interferometer is compared with the Newtonian interferometer, it will be found that it is not a point source, the light source is somewhat scattered, and the light passes through the middle beam splitter O after passing through the first lens, so that part of the light is reflected to the reflection. The mirror M2 is reflected back to the beam splitter O, and a part of the light penetrates the compensator C. After reaching the mirror M1, it is reflected back to the beam splitter O to synthesize the same light, and the result is hit on the D (Detector), so we You can see a circle of stripes on the Detector, which is the interferogram A. So the Michelson interferometer is usually used to measure the change of the distance. When we want to measure the distance, we only need to measure the original interference fringe A. Then, the mirror M2 is moved backward, the interference fringe B is measured, and then the distance can be calculated from the change of the stripe A~B.

The third is the Fizeau Interferometer

The Fizeau interferometer is the most common interferometer at present. It is also the simplest architecture and the most convenient one. The laser beacon laser source is the upper left. The laser source is a very good single-wavelength source. After several procedures in the middle. When passing through the Reference flat reference surface, part of the light is reflected, and part of the light penetrates into the flat under fest surface to be reflected and then reflected back. Therefore, the result we see is the difference between the reference surface and the surface to be tested. When the reference planes are different, the measured surface stripe to be tested will be different. The disadvantages of this interferometer are: It is easily affected by external forces such as wind direction, vibration, and air changes, and must be placed on the earthquake-proof table in a closed room. In order to clearly see the interference fringes, it is also known as the non-co-path interferometer.

The fourth is the Mach-Zehnder interferometer

The extended source at the lower left is an extended source similar to the Michelson interferometer. The light source is split into two passes after the first Beam-splitter, each passing through a Mirror mirror and then synthesized by a second Beam-splitter. After a light, the result is hit on the Detector. Because the middle is divided into two light sources, the space and distance can be adjusted greatly, so it is more suitable for measuring large or penetrating objects, for example: Can be used to measure large areas of glass. Place the object under test between the first Beam-splitter and Mirror mirror on the path, we can see the difference between path A, path B and the object to be tested. This is also a non-co-path interferometer. Its disadvantages are: It is easily affected by external forces such as air changes. The advantages are: It can measure objects with large volume or area.

The fifth is the Twyman-Green interferometer

The Twyman-Green interferometer is similar to the Michelson interferometer. When a light source comes in, after the BEAM EXPANDER makes the light source larger, it is divided into two lights by the middle BEAMSPLITTER, and then reflected back to the detector. Interferometers have different application ranges, directions and restrictions.