Laser Interferometers
Laser interferometers are precision instruments used to measure distances and distances-related parameters accurately. The instrument is based on the principle of interfering laser beams reflected off a known surface. Two laser beams are launched in different directions, after reflection they are brought to intersect. When these two beams are made to interfere in the detectors, their intensity is measured. The interference of two beams depends on two factors: the relative path difference of the two beams, and the relative phase difference between them. This interference pattern can be used to determine the distance to the surface.
Laser interferometers are used in many applications to measure displacement and surface topography. In general, these devices are adapted to measure distances in the range of millimeters or micrometers. The resolution of the device is limited by several factors such as the laser wavelength, the optics used, and the detector size. Depending on the application, a resolution of a few microns can be achieved using prolonged integration time.
Industrial applications such as precision machining, inspection, image processing and quality control are widely used. These applications include measuring the distortion of optics, measuring the linear or angular displacements of machine parts, or 3D mapping surfaces. These measurements can be carried out under ambient conditions, or in harsh environments such as extreme temperatures or laser radiation environments.
Apart from industrial applications, laser interferometers are also used for scientific purposes in laboratories. With these devices optical elements can be tested for precision and quality, as well as for thermal and mechanical stability. Some important experiments such as measurement of the speed of light, can also be done using interferometers.
The laser interferometers are classified into two major categories: Michelson and Fizeau type. Michelson type interferometers are the most widely used interferometers. It consists of two mirrors which are adjusted in such a manner that the light beams are reflected in opposite directions. The fluctuations of the beam intensity, due to interference, is measured in detectors at the two collection points.
Fizeau type interferometers are used for measuring extreme short distance. It consists of two interference pieces, a fixed reference piece and a stationary object being measured, which are arranged in parallel planes. The light is split into two beams and passed onto the reference piece and the object piece. After reflection, the two beams interfere and the total light intensity can be measured. By changing the distance between the two parallel planes, the distance between the two objects can be calculated.
In conclusion, laser interferometers are one of the most accurate and precise instruments to measure distances. They play an important role in both industrial and scientific applications, which require high accuracy and precision. This makes them one of the most important products in the field of metrology.
