Magnetooptic equipment are of three types: magnetopolarimeters, magnetopolariscopes, and magnetooptic hysterographs. It is possible to combine the various functions into one single system, but this is undesirable in constructing standard equipment, since it leads to a loss of accuracy. This leads us to formulate specifications for elements of magnetooptie equipments, and if these are satisfied one will obtain the highest accuracy of measurement, which will allow for certification of certain equipment elements. The literature lacks any systematic description or comparison of elements of such equipment, although some data has been given in [1] and certain other papers. A standard magnetooptic equipment consists of a radiation source, optical elements (including polarization devices), a magnetization system, and eleetromechanical and electronic instruments, together with control and recording units. Figure 1 shows typical schemes for such equipment for absolute measurement of the magnetic characteristics of materials (magnetooptic angle of rotation, saturation magnetization, coercive force, etc.). Radiation Sources. Published expressions [1] show that the signal-to-noise ratio in a magnetopolarimeter is directly related to the radiation power; filament lamps are the most widely used in existing apparatus [2, 3], but these have the deficiency of low efficiency, which is further reduced on account of the employment of light filters or monochromators in most instances. Use of gas-discharge lamps provides a higher efficiency and a higher radiation flux, but there are appreciable random variations in the radiation power, which leads to an undesirable reduction in the signal-to-noise ratio. Lasers are largely free from these deficiencies and have recently become widely used in magnetooptic equipment for precision determination of magnetic characteristics on microscopic volumes; lasers enable one to obtain monochromatic radiation at high power levels. Deficiencies of lasers include the considerable noise fluctuations in the radiation power (0.1-0.507o for helium-neon lasers, or 1-2~ of the mean radiated power for argon lasers), but certain methods of suppressing source noise [4, 5] enable one to minimize this interfering factor. Optical Elements and Polarization Instruments. The optical elements in such equipment include lenses, mirrors, and stops' which shape the radiation flux and the image of the domain structure. To provide high signalto-noise ratios and good top contrast it is necessary for the lenses and mirrors to produce little depolarization in the radiation flux, while the materials should have only small Verdet constants. Careful choice of the optical elements enables one to reduce considerably the depolarization introduced by these to below the level of that produced by the ferromagnetic specimens, while the systematic error arising from parasitic rotation of the plane of polarization can be reduced to the noise level. Polarization devices are amongst the most important elements whose performance largely governs the accuracy and contrast in such equipment. They should be of high performance, of the highest possible aperture for the incident beam, and have a wide working spectral range. These requirements are met by refringent prisms of Iceland spar with C a= 10-5-10 "8. Sometimes one can use film (dichroic) polarizers, whose advantage is the high linear and angular apertures for the beam. The polarizing devices are mounted in rotating readout units, so the latter must be highly sensitive and accurate, while having small eccentricity and provide for adjustment of the prisms.