SU881571A1 - Device for measuring transparent media refractive index gradient - Google Patents

Description

The invention relates to a measuring technique, and more specifically to optical devices designed to study the distribution and fluctuations of the refractive index of transparent ones. A device for measuring the refractive index gradient containing a lighting slit at the focus of the lighting lens and a diaphragm from a set of transparent colored glasses in the focal plane of the objective lens is known. parts or a color aperture in the lighting part of the device, and a narrow slit aperture in the receiving part Dispersant prisms, which are located in the illumination, are also located. parts of the device G. If there is no optical heterogeneity, then the light rays coming from different points pass through the same place of the diaphragm and the entire image field is painted in one color depending on the setting of the device. When inhomogeneities are introduced into the receiving aperture, the lighting slit areas are colored in different colors, which leads to a change in the color distribution in the image, all areas of the medium deflecting light at the same angle are colored the same. The sensitivity of this method cannot be made sufficiently large, since diffraction noise limits the minimum thickness of the color bands to about 0.15 mm. The use of such devices is also limited due to the low color saturation of the images and the low sensitivity of photographic materials, especially in cases where there is a large non-uniformity of the distribution of the gradients of the refractive index in space, and the structure of the regions with both small and large gradients of the refractive index exists. -bets The closest technical solution to the invention is a device for measuring the gradient of the refractive index of transparent media, comprising a light source and a lens successively installed along the light beam, a slit diaphragm, main lenses between which the test medium is located, and a receiving part with a grating consisting

from the system of transparent and opaque bands 2.

The deviation of the rays in the heterogeneity is determined by the displacement of the shadows from the diaphragm. The most laborious operation in this case is the identification of shadows, especially if the heterogeneities have a complex shape and the shadows are split in two, mixed up and interchanged. Attempts to resort to special techniques - to highlight strokes, changing their thickness or coloring also do not always allow to perform an unambiguous interpretation of the image.

The purpose of the invention is to increase the information content of the shadow image of transparent media.

This goal is achieved by the fact that in a device for measuring the gradient of the refractive index of transparent media, which contains a white light source and a lens, aperture, main objectives, between which there is a test medium, and a receiving part with a grating consisting of a system of transparent and opaque bands; between the first main object along the light beam and the medium under study, there is a dispersing prism with parallel edges, overlapping the entire parallel light The beam entered through the lens, and the slit diaphragm and grating are installed perpendicular to the gradient of the refractive index of the prism, and the diaphragm, grating and prism are made with the possibility of synchronous circular rotation.

The drawing shows a block diagram of the device.

The device circuit includes a white light source 1 with a continuous or linear spectrum (incandescent lamp, arc, mercury lamp), a lens 2 forming the source image, a diaphragm 3 in the form of a flat slit, a main lens 4, a dispersing prism 5 with parallel edges, glued from different sorts of glass with different dispersion Zz / hell / but the same value of the refractive indices for one of the colors (for example, a prism made of glasses TK-B and F-1 does not deflect the rays of yellow light), the studied medium 6 enclosed in with transparent walls free from optical irregularities, the main objective of the receiving system 7 installed. Near its focus is a flat grid 8, consisting of a system of transparent and opaque strips, a lens 9 forming an image of the medium under investigation, and a recording device 10, with the slot and grid installed perpendicular to the direction of deflection of the light rays in the prism 5 and the entire system diaphragm - prism - grating is extended with the possibility of synchronous rotation around the longitudinal optical axis of the device,

The device works as follows.

White light emitted from source 1 passes through lens 2, which forms the image of the source, a flat-slit diaphragm located at the focus of the main lens 3, comes out in the form of a parallel beam, which enters the dispersing prism, deflecting light by an angle depends on the wavelength and does not Exceed f / f, where is the maximum deflection of the beam in the focal plane and the receiving lens of the shadow device, at which the light is not vignetted by the elements of the device; f is the focal distance of the Receiving Lens, for the most common IAB-451 device; 25 mm, f mm.

A set of beams of light of different colors coming at different angles falls on the test medium. In the absence of disturbances, the rays in it do not deviate and arrive at the main lens. In this case, in its focal plane, a spectrally colored expanded slit image is obtained in which each color is spaced apart

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Claims (2)

from the axis of the system, where sU is the displacement of the beam; is the deflection angle of the rays at the output of the prism; f is the focal distance of the main lens; D is the defocus amount, the distance from the focus to the plane of the receiving grating / S is the distance from the medium plane under investigation to the main objective of the receiving system. Separate sections of the slit image are overlapped with a flat grid consisting of a system of transparent and opaque strips, and an image of the medium being colored into a system of color strips is observed in the image plane of the string 9. The thickness and color of the bands depends on the angle of deflection of the light and the chosen thickness of the bars of the lattice and their position. By moving the grating in a direction parallel to the direction of deflection of the light in the prism, you can get different color bands. During the course of physical processes in the medium under study, the local value of the gradient of the refractive index and, accordingly, the deflection angle of the beam passing through the given region of the medium and its position j relative to the lattice, change. The original color distribution of the image is disturbed, and new, previously closed colors appear in the image. The resulting image is recorded using a photo, movie camera or video recorder. Since this system registers the deflection of beams in only One direction, perpendicular to the slit and the grating strips, to analyze fluctuations of the refractive index gradient in all directions, which is important in analyzing spatial disturbances of complex shape, the slit, prism, and grating are designed to be synchronous rotation around the optical axis of the system, a device for measuring the refractive index of transparent media compared to the best examples of similar equipment allows substantial expand the amount of information on the distribution and nature of the disturbance groschienta refractive index. For quantitative measurements in most cases there is no need to resort to photometric measurement of a photo or a film. The color image obtained in this device has a high juiciness, contrast and color saturation, provides a significant increase in the information content of the internal spatial structure of the studied physical inhomogeneities of the emitted physical processes in cf de compared with traditional methods (Diaphragm - grating color method), which allows measure a number of new characteristics of the movement dynamics of transparent media (for example, convective velocity — the transfer rate of characteristic perturbation structures). The device can be successfully used in laboratory conditions in the study of transparent inhomogeneities in aero- and gas dynamics, in hydrophysics, power engineering, and other areas of application of traditional thematic methods, especially in cases where the disturbances are inhomogeneous distribution in space, and Of interest is the structure of the region, region, and with large and small variations of the refractive index gradient, which cannot be fully understood and interpreted using well-known instruments and devices. . Apparatus of the Invention A device for measuring the gradient of the refractive index of transparent media, comprising a light source and a lens, a slit diaphragm, main objectives, between which the medium under study is located, and a receiving part with a grating consisting of a transparent and opaque strip system, characterized by a light source. the fact that, in order to increase the informativity, between the first main beam along the light beam and the medium under study is placed a dispersing prism with parallel bubbled facets, the overlapping light beam transmitted through the lens, and the slotted aperture grille and mounted perpendicularly to the gradient of the refractive index of the prism, the diaphragm, the grating and the prism are arranged to synchronous rotating circular. Sources of information taken into account in the examination 1. L. Vasiliev. Shadow methods. M., Science, GRFML, 1968, p. 40-49. 2. In the same place 84-89 (prototype).