SU64225A1 - Method and instrument for measuring visibility - Google Patents

Description

The known devices for measuring visibility have the common feature that they are based on the use of a veiling brightness, which serves to reduce the visible contrast to the threshold of the contrast sensitivity of the observer's eye. Such are Vigand's wedge visibility meter and Sharonov's smoke meter.

The veiling brightness in the specified devices is created by a special illuminator, the incoming BI design of the device and; emitting light in the presence of outdoor lighting. Since in these cases there is no definite relationship between the velocities of the observed objects and the veiling brightness, the latter is included in all the equations relating the desired quantities, as a quantity is not known.

In order to eliminate the unknown veiling power, it is necessary to construct one extra equation, for which additional observation must be made on a special object that is independent of the others.

This is one of the main drawbacks of the existing types of notable devices for measuring

visibility, considered from the point of view of the requirements imposed on travel meters.

The next very significant drawback of these devices is the iB that the inconsistency of local illumination leads to fluctuations in the artificial veiling power of the instrument and, consequently, to distortions In the results of observations.

The subject matter of the invention is a method for measuring visibility, according to which an image of an object is observed through a photometric device which weakens luminance and veils it with an unabated image of the same object, which is superimposed on the first by optical means.

To implement this method, various walking-type visibility meters can be built, which make up a special group of devices for determining visibility and will be characterized by the use of improper (natural) sampling brightness, which is in a certain relation to the velocities of the objects observed. Due to this feature, such walking visibility meters will not have the disadvantages inherent in meters with their own (artificial) veiling power, which will allow them to be classified as devices that are quite suitable for determining visibility under hiking conditions. In FIG. 1 shows a diagram of the device in an exemplary structural design; FIG. 2 is a side view of the device, FIG. 3 is a diagram of another embodiment of the device; FIG. 4 is a side view of the device shown in FIG. 3. Inside the case 1, a creeping mirror 2 (glass plate with plane-parallel surfaces) and a pair of ordinary mirrors 3 and 4 are reinforced, of which the first, parallel to mirror 2, is fixed, the second, approximately parallel to mirror 2, is able to change its position during the rotation of eentov 5 to 6 (Fig. I and 2). The mobility of the mirror 4 is achieved either by means of strengthening it in a gimbal, in which rings abut VI1NTA 5 and 6, or by fitting it onto three point supports, one of which is fixed and the other two are formed by the tips of screws 5 and 6. In the latter In the case of mirrors 4, three corresponding conical sockets are drilled and the mirror is pressed to the support by means of three small springs (in the drawing of Figs. 1 and 2, the second variant of the device is shown). Between the mirrors 3 and 2 there is an absorbing lin 7, any part of which, thanks to the rotation of the cremallea 8, can be located before the eye of the observer. The system of collecting lenses 9 and 0 "of the above mirrors serves to form the corresponding strength fields; its optical axis leaves an angle of 45 ° with the plane of the mirror 2. The connection of the parallel optic system I and 12 and a special scale bar (Hia drawing e is shown) transforms the described trio and the stereoscopic scale meter. .p1m.Ap The light rays emanating from a pair of contrasting surfaces Am, An and some third surface of the AG, passed through the lens 9, are divided into two parts on the surface of mirror 2. One part of the rays, reflecting from mirror 2, goes to mirror 3 and, reflecting from it, goes further through the absorbing wedge 7, mirror 2 and forms the first image of the observed surfaces. Another part of the rays, passing the mirror 2 and reflecting sequentially from mirrors 4 and 2, forms the second image. Thus, the observer will see through the ocular 10 two images of the surfaces Am, An and AG. Acting with screws 5 and 6, they give the mirror 4 such a position, with a brightness of p and p (images of surfaces Am and An), received by the first way, would be covered with brightness P (by the image of surface Ar), obtained by the second way. After that, rotating Cremalleu 8, the wedge 7 is inserted, i.e., it is given a position where, at a very small displacement to one side of this position, the contrasting colors of the PC and PD become indistinguishable, and, at the reverse displacement, protrude separately. The transparency of that part of the wedge through which contrasting materials are considered, read by the appropriate scale, will be equal to the desired ratio of the coefficients) Indeed, let b be the transparency of mirror 2, ig is the reflection coefficient for mirror 3 (also for mirror 4), is the reflection coefficient for mirror 2, corresponding to these angles of incidence of the rays, is the transparency of the wedge 7. Since the possible changes in the inclination of the mirror 4 are practically small, then the values of ii, 12 and h can be considered independent of what direction none of the rays they are taken. Suppose that the luminances of the images of the surfaces Am, A „and Ar obtained by the optical system described above are equal to РЬ PS and РЗ, BI assuming that ii 12 13) Then the luminances of the first images will be equal respectively to Rt gl 1 Pn gl P2 (3) luminance second images of Pt g2 PI Pn §2 P2 (4) Pr g2 PS where: gl Til h is and g li ig ig. You can put: PI k p (5) p ,. Then relations (3) and (4) can be rewritten by Pt SIP ™ RP Si Pn (6) Pr Si Pr Pm 2 pm Pn S2 Pn Pr S2 RG, sj k t 1, i, ig Sa k ii la Ia The first two equalities in (6) and the last in- (7) constitute the initial condition. Taking into account (2) we get L i,., 9, FIG. 3 and 4, the two collecting lines 1 and 2 with the help of inclined mirrors 3 and 4 give a double image of the observed surfaces A ™, AP and AG on a small screen 5 located inside the case. Lens G has a variable aperture in front of it, lens 2 is a constant. Mirror 3 is fixed motionless, mirror 4 is capable of somewhat changing its position under the action of the antenna 6 and 7, just as it takes place in the first device. The images of the observed surfaces are viewed through the ocular 8. It is easy to see that if the first image of the surfaces is obtained through the lens D and the second image is obtained through the lens 2, then the desired value will be equal to the square of the ratio of the relative apertures of the corresponding diaphragms di and d-2, i.e. fdlV 2 / The scale used to determine the relative aperture of the variable aperture can be easily listed to determine the value of L. Nature of the invention 1. A method for measuring visibility, according to which the image is The object, observed through a photometric fixture weakening the brightness, is veiled by the brightness of another image, which is based on the image of an object, which is superimposed by comparison to another image of this object, the brightness of which is attenuated by a photometric device. 2. An apparatus for carrying out the method according to claim 1, provided with a weakening photometric device installed on the path of the rays coming from objects into the ocular, and a 45 ° angle to the direction of the ray of a plane-parallel plate that differs by using two mirrors, one of which is rotary, providing obtaining of two images of an object combined with each other, the brightness of one of which can be weakened by a photometric device.

FIG. one

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FIG. 2

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FIG. 3

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FIG. four