SU993011A1 - Interferometer for measuring large displacements - Google Patents

Description

The invention relates to a measurement technique and can be used, in particular, for interference measurements of large displacements in geodesy, metrology, mechanical engineering, etc.

Michelson-type interferometers are known for measuring large (up to several tens of meters of displacements, in which the measurement is made by counting interference fringes as the end section of the detector travels along the entire measured distance 1.

However, in these interferometers, to obtain the desired length, reduced to vacuum, it is necessary to additionally measure the refractive index of air, for which it is necessary to measure temperature, pressure and humidity, followed by a calculation; refractive index, or use an additional interferometer specifically designed to determine the refractive index of air.

Closest to the proposed technical entity is an interferometer for measuring large displacements, containing the source

light, a beam splitter, dividing the luminous flux into two beams, a fixed reflector located in one beam, a movable reflector located in another beam with the possibility of moving the axis of this beam, and a recording unit with an interference band counter G 2 J.

The disadvantage of such an interferometer is the low measurement performance due to the need to use additional measuring means to determine the refractive index of air, for example, temperature and air pressure sensors, from whose indications the refractive index is calculated and the corresponding correction is introduced to the measured distance.

20

In addition, the interferometer is characterized by an insufficiently high accuracy of measurement, apparently, that the refractive index is determined by

Claims (2)

25 is usually at the location of the interferometer, while it is necessary to know the value of the index of averaging, averaged along the entire measurement path along which the reflector moves. This circumstance is important iTjH path lengths, calculated in tens of meters. Thus, the availability of additional measurement tools increases: -1.1 the volume of measurement operations and thereby reduces the performance of measurements, and the lack of a possibility to obtain a value of the refractive index strictly averaged along the path reduces the accuracy of the final measurement result. The purpose of the invention is to increase productivity and accuracy of measurement due to. eliminating the need for additional measurements to determine the air conditioning index and to ensure immediate and the length given to vacuum. This goal is achieved by the fact that an interferometer for measuring large variables of the nearest CE. It is fitted with a vacuum chamber made with the possibility of movement in the direction coinciding with the direction of movement of the subversive corner reflector, and the latter is installed inside this chamber. The vacuum chamber is made in the form of a corrugated tube made of vacuum rubber with the ability to compress and stretch along its axis, the front end of the corrugated tube is equipped with a metal plate with a transparent window for the passage of the light flux, the rear end of this tube is equipped with a metal plate connected to a movable reflector, and electromagnets are attached to the plates. FIG. 1 shows a diagram of an interferometer for measuring large trans 1; in fig. 2 shows an embodiment of a vacuum chamber with a movable angular reflector placed in it. The interferometer contains (Fig. 1J light source 1, a beam splitter 2 for dividing the luminous flux into reference and remote beams, fixed angular reflector 3, installed in the reference beam, vacuum camera 4, mounted for movement along guides 5 along C1SI of the remote beam, displacement (:: angled reflector b, mounted inside the vacuum chamber 4 II remote beam with the possibility of movement within the chambers The chambers in the direction of movement itself: amers, and a recording unit 7 with a; a quad, 8 interference fringes; Vacuum chamber 4 of Fig. 2) is made in the form of a corrugated tube 9 made of special vacuum rubber with internal spacer rings (not shown to prevent atmospheric flattening). pressure and has a front metal plate. 10 with a transparent window 11 and a rear metal plate 12, to which a movable corner reflector 6 is firmly attached (the corrugated tube 9 can be rectangular or square, important It is necessary that its structures provide the possibility of compression and expansion according to the type of fur. The front 10 and rear 12 metal plates have protrusions 13 that allow the camera 4 to move along the guides 5. On the plates 10 and 12, electromagnets 14 and 15 are rigidly mounted, providing for their inclusion strong adhesion to the platform 11 carrying the guides 5. The interferometer works in the following way. When moving the movable corner reflector 6 in the chamber 4 (figure 1), the counter 8 of the interference fringes produces an account of the interference fringes. When the moving corner reflector 6 in the chamber reaches the final position, the counting of the strips is stopped (without turning off the counter 8 to save the counted number of strips, but by blocking the path to the luminous flux) and moving the camera 4 along the measurement line at a fixed position of the movable corner reflector 6 to those until it again assumes its original position in chamber 4. Then the movable corner reflector b is moved in the fixed chamber again, resuming the counting of bands, etc. This process is repeated until the movable corner reflector 6 has covered the entire measured distance. The operation of the device can be explained in more detail on the basis of FIG. 2. First, with the electromagnets 14 and 15 turned off, the vacuum chamber 4 is set to its original position, in which the movable corner reflector b is located at the end of the measured line. Then an electromagnet 14 is switched on, which rigidly fixes the front metal plate 10 on the platform 16, and the rear metal plate 12 with a movable corner reflector b is moved towards the beam splitter 2. At the same time, the chamber 4 is compressed and the difference in the path of the interference beams changes by changing the vacuum path remote beam, the counter of 8 interference bands produces counting bands. After the chamber 4 is compressed to some end position shown by dotted line in FIG. 2, the electromagnet 15 is turned on, thereby rigidly fixing the position of the movable corner reflector b, and the electromagnet 14 is turned off, thus releasing the front plate of the chamber 4, as a result of which the chamber expands and occupies a new position, having been moved along the measurement line. Then, turning on the electromagnet 14, fix the position of the front metal plate 10, turn off the electromagnet 15, freeing the rear metal plate 12 with the movable corner reflector 6, move this reflector b, compressing the chamber 4, etc. At the same time, when the electromagnet 15 is turned on, each roz.az is stopped, and when the electromagnet 14 is turned on, the counter of 8 interference fringes resumes. It should be noted that it is absolutely unnecessary when compressing the camera 4 d each time moving the movable corner reflector by one and the same amount. Compression and stretch 4 serves only to ensure the movement of this reflector b in vacuum over the entire path, and the accumulation counter 8 of interference fringes works only during the displacement of this reflector b, which occurs in discrete sections, and the lengths of these sections can to be arbitrary, since in sum they in any case constitute the total length of the measured distance. The use of the proposed interferometer provides direct obtaining of the length reduced to vacuum, without determining the refractive index of air and without enclosing the entire measured distance into the vacuum tube, which allows for improved performance and accuracy of measurement. Claim 1. Interferometer for measured large displacements containing a light source, a beam splitter dividing the luminous flux into two beams, a fixed reflector located in one beam, a movable reflector located in another beam movable along the axis of this beam, and a recording unit with an interference meter counter, characterized in that, in order to increase the productivity and accuracy of measurement, it is provided with a vacuum chamber adapted to move in the direction coinciding 2. The interferometer according to claim 1, characterized in that the vacuum chamber is made in the form of a corrugated tube made of vacuum rubber with the ability to compress and stretch along its axis, the front end The corrugated tube is equipped with a metal plate with a transparent window for the passage of the luminous flux, the rear end of this tube is equipped with a metal plate connected to a movable reflector, and electromagnets are attached to the plates. Sources inf Forms taken into account during the examination 1. Yu.V. Kolomiytsev. Interferomtstsll. L., Mechanical Engineering, 1976, p. 189,194., 2. In the same place 191, rice .. 89 (prototype. V v v