SU798503A1 - Visibility meter - Google Patents

Description

The invention relates to optical devices, and more particularly, to visual meters of visibility, working by the method of photometric blanking and designed to determine the degree of visibility of various objects and their contrasts.

Known visibility meters with veiling brightness, based on the method of photometric blanking, made in the form of a monobinocular telescope with two independent comparison half-fields. In front of one of the objects of the telescope, a nozzle with an optical 15 wedge is installed (to obtain a veiling brightness). In front of another lens, the same nozzle and collimator are fixed, containing a black mark placed in the focus of the achromatic 20 lens. In these devices, damping is achieved by imposing an additional veiling brightness on the image in question. The latter is formed by bifurcating 25 of the image observed in the field of view and then combining the object under consideration with the corresponding section of another image. As the veiling brightness increases 30, the brightness of the main image decreases. Obtaining two images and changing their brightness is carried out either using the polarizing prism of Wollaston (polarizing visibility meter) / or using an optical achromatic wedge (measuring visibility range) [1].

The disadvantages of these devices include a large error in measuring the degree of visibility of objects.

The closest to the proposed technical essence visibility measuring device is composed of sequentially Raspaud ^g decomposition collimator and the telescope, which is mounted between the wedge achromatic [2].

The disadvantage of this device is the large relative measurement error for large values of the degree of visibility.

The purpose of the invention is to increase the accuracy of measurements and eliminate its dependence. from the measured size.

This goal is achieved by the fact that in the known device, consisting of successively arranged 798503 collimators and a telescope, between which an achromatic wedge is installed, it is equipped with a square aperture diaphragm installed in front of the achromatic wedge and a photometric wedge installed 1 behind the achromatic wedge. '-

The drawing shows a schematic diagram of the proposed visibility meter.

The device contains a collimator formed by components 1,2 and 3, an telescope formed by components 4 and 5, an achromatic wedge 6 between them in parallel with the rays, a square aperture diaphragm 7 in front of it, followed by a photometric wedge 8 with a variable transmittance. Both wedges 6 and 8 have the possibility of joint movement relative to the aperture diaphragm, perpendicular to the optical axis. In this case, it is rational to perform the achromatic and photometric wedges of a rectangular shape.

The device operates as follows.

During the measurement, the achromatic wedge 6 and the photometric wedge 8 move perpendicular to the optical axis and partially overlap the aperture diaphragm 7, which is the entrance pupil of the telescope objective 4. The luminous flux from the object under study and the background on which it is viewed, passing through the collimator 1,2,3, the aperture diaphragm 7, is divided into two streams in the plane of the wedge 6 and forms two images of the same picture in the focal plane of the eyepiece 5. One of them is formed by the light flux passing through the 6.8 wedges and lens 4, the other image, additional, by the light flux passing through the part of the aperture diaphragm 7, not blocked by the 6.8 wedges, and the lens

4. Both of these images in the field of view of the telescope are offset relative to each other by an amount proportional to the refracting angle of the wedge and the increase in the telescope 4,

5. As wedges 6.8 move beyond the aperture diaphragm 7, the brightness of the main rejected image decreases, and the brightness of another non-rejected image superimposed on it increases. At some position of the wedges, the observed deviated image of the object is extinguished, this position is a reference for determining the ³ degree of visibility of the object. The latter is determined from the expression

V-th = - “>

where b = -CA-

- the relative effective area of the wedge;

- the area of the aperture diaphragm, overlapped by a wedge;

- area of aperture diaphragm;

- light transmission coefficient of the Photometric wedge.

show that the introduction

S ΐ

Calculations _; of a square aperture diaphragm and a photometric wedge of variable density makes it possible to reduce by 4 times the relative error in measuring the degree of visibility, making it practically constant in the measurement range from 10 to 100.

Claims (1)

Claim Meter visibility, consisting of successively arranged __ collimator and the telescope IU ³ forward which is mounted achromatic wedge distinguishing with I that, in order to increase the accuracy of measurement and to eliminate its dependence on the measured velichi40 us, it is provided with a square aperture diaphragm placed in front of an achromatic wedge, and a photometric wedge installed behind the achromatic wedge.