SU1651168A1 - Method for measuring indicatrices of brightness of light diffusing coatings - Google Patents

Abstract

The invention relates to photometry media. The goal is to simplify the measurement method with. The method is carried out by measuring the luminance of the coatings deposited on the substrate at different angles of illumination and sighting. New in sposb is coating on a substrate, which is made in the form of a sphere, obtaining a sphere image in the plane of the sensitive element of the photometer, element-wise photometry of the polarity of the obtained image and determining the zenith angle of illumination, zenith and azimuth angles of observation of each photometric element by its linear coordinates on the image of the sphere and the set scattering angle (the angle between the optical axes of the illuminator and photometer). The simplification of the method consists in reducing the number of angular displacements of the elements of the measuring setup that implements the method, from the required three displacements with all known methods to one. 4 il. i (L

Description

about ate

The invention relates to photometry of media and can be used in the study of the reflective characteristics of light-scattering structural materials.

The purpose of the invention is to simplify the measurement method.

Fig. 1 is a schematic diagram of a device implementing the proposed method; in fig. 2 - mutual angular position on the sphere; in fig. 3 - the sphere in the plane of the sensitive element of the photometer; Fig. 4 shows a part of the results of photometry of an image of a sphere coated with aluminum powder with a scattering angle of 45 °.

The unit vectors (Fig. “2) characterize the direction to the illuminator O, the photometer H and the normal to the surface of the photometric element dS (N) The E curve determines the lighting limit of the part of the sphere. The F curve shows the cross section of the sphere with a plane containing vectors 15 and N. The point С0 determines the center of the sphere. On the three spherical triangle O, H, N defined by it by three vectors O, H, N

The illumination angle (in the plane of incidence containing the O and N vectors), 0c is the zenith angle of observation (in the plane of the H and N vectors), fn is the azimuthal angle of observation (the angle between these planes) tf. the angle is scattered between the vectors 0 and H (Fig. 1), A is the azimuthal angle between the planes, observable vectors иГ and H and vectors N and H, respectively.

Point C is the center of the circle of the image of the Sphere, R is the radius of the image of the sphere, the trace of the plane F (Fig. 2) is the axis of symmetry of the image of the illuminated part of the sphere, the coordinate axis CVL coincides with this axis of symmetry, the midpoint of the image of the photometric Element of size 18 y-Dy has linear coordinates x, y. The values of Ax and D, y are determined by the linear spatial resolution of the photometer in the plane of its image (Fig. 3).

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The device contains (, FIG. F; a fixedly mounted photometer 1, whose optical axis passes through the center of a spherical sample (sphere) 2. A fixed illuminator 4 is mounted on a rigid guide 3, representing a flat arc, which moves along arc 3, changing the angle of the scattering of the OS within (Xtf & i 800) so that its optical axis ice time is in the same plane, which also contains the optical axis of the photometer -1, and passes through the center of the sphere 2. As auxiliary elements, useful when defining image parameters spherical sample, the device contains an additional illuminator 5, illuminating sphere 2 so that its entire side facing the photometer is fully illuminated together with the main illuminator 4, as well as a thin rigid rod holder 6, the axis of which passes through the center of the sphere and is located exactly in that the same plane as the optical axes of the photometer and illuminator; and a removable thin rod 7, which is an extension of the rod holder 6 from the diametrically opposite side of the sphere and is mounted strictly coaxially with it.

16511684

The method of measuring the indicatrix of the light scattering coatings is carried out as follows.

The coating under investigation is applied on the surface of sphere 2 in a uniform layer, and the sphere is installed together with rods 6 and 7 into the measuring device. At a predetermined angle of the photometer to the axis of the photometer, they are mounted on the guide 3 illuminator 4. As a photometer, for example, a scanning photometric system with recording and video control devices (ICU) is used. Illuminate the sphere with 2 illuminators 4 and 5. They direct the optical axis of the photometer, corresponding to the center of its field of view, to the center of the sphere and obtain an image of the fully illuminated side of the sphere in the plane of the sensitive element of the photometer and recorded if necessary). With the help of special service devices of internal controllers, for example, coordinate reference points (or in other ways, for example, by successive movement of the platform on which the photometer is installed, in horizontal and vertical directions) coordinates of the sphere image are determined (in the auxiliary coordinate system of the internal control screen or plate- 35 forms): upper limit YB, lower

By these

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YM, left X and right Xg values in the same coordinates find the position of the center of the image circle.

Хс (Хп + ХА) / 2;

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and determine the radius of the circle image

R (Xn-XA) / 2 (Ye-YH) / 2

(image scales along the axes X, Y of the internals must be equalized). If necessary, turn the photo- meter to-. the circle of the axis coinciding with its optical axis ensures that the images of rods 6 and 7, defining the axis of symmetry of the image of the illuminated part of the sphere, are strictly along one of the coordinate axes, for example, the Y axis In the installed position on the image of the sphere impose a new coordinate system

The coating under study is applied on the surface of sphere 2 with a uniform layer, and the sphere is installed together with rods 6 and 7 into the measuring device. At a predetermined scattering angle about to the axis of the photometer, the illuminator 3 is mounted on the 4 "4" illuminator. For example, a scanning photometric system with recording and video monitoring devices (ICU) is used as the photometer. Illuminate the sphere with 2 illuminators 4 and 5. They direct the optical axis of the photometer, corresponding to the center of its field of view, to the center of the sphere and obtain an image of the fully illuminated side of the sphere in the plane of the sensitive element of the photometer and recorded if necessary). With the help of special service devices of internal controllers, for example, coordinate reference points (or in other ways, for example, by successive movement of the platform on which the photometer is installed, in horizontal and vertical directions) coordinates of the sphere image are determined (in the auxiliary coordinate system of the internal control screen or Platform): upper bound YB, lower

By these

YM, left X and right Xg values in the same coordinates find the position of the center of the image circle.

40

Хс (Хп + ХА) / 2;

and determine the radius of the circle image

R (Xn-XA) / 2 (Ye-YH) / 2

(image scales along the axes X, Y of the internals must be equalized). If necessary, turn the photo- meter to-. the circle of the axis coinciding with its optical axis ensures that the images of rods 6 and 7, defining the axis of symmetry of the image of the illuminated part of the sphere, are strictly along one of the coordinate axes, for example, the Y axis In the installed position on the image of the sphere impose a new coordinate system

The xYy is centered at XG, Yc and the y axis is directed along the Y axis. After that, the additional illuminator 5 is turned off, the rod 7 is removed, and the surface brightness is measured in the image of the 4 part of the sphere illuminated by the illuminator. At the same time, the brightness of each photometer's element dS, separated by an elementary field of view, characterized by coordinates (x, y) in the superimposed on the image in this way on the image of the xCy coordinate system, is converted into an electrical signal proportional to it. The luminances of each of the elements dS (x, y) measured in this way are related to the angular coordinates 00; 0ts; C,; as indicated in Figures 2 and 3, are expressed in terms of the linear coordinates x, y, the image radius R and the scattering angle as follows:

sml

(one)

cos 9n cos cosO + sint sin0, .cos A;

cos x2 + y2 (cosoi-cosQMcos00) /

/ (sin0Hsin00).

The illuminated part of the sphere (the illuminated hemisphere) contains areas, the whole set of illumination angles of which 00 is in the range from 0 to 90. these sites on the sphere (the location of their images on the image of the sphere). Thus, photometry of the image of a sphere at each of the set scattering angles Od gives a multitude of results corresponding to certain areas of the angles Q, He and Photometry within 0 # 180 extends this set and includes all possible angles of illumination ( 0-Ј90490) and observations (0. 0 ": 90 °, -180 CHS = 180 °). The resulting data sets L (Q0; 0H; Cft.) Are, for example, stored in a computer memory and processed to obtain functional dependencies (indicatrices) of luminance on lighting angles and observations

"R

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Since the scattering of the set of angular coordinates of the studied areas of the coating (90; @ and, (ri)) partially overlaps when photometry at several angles, the final set of results L (0Q; 0 ", Sri) may be redundant, so that the random composition can be estimated - JQ schA measurement errors and, thus, the reliability of their results r is increased

Example. Photometry at each of the set angles Qi is carried out according to the results of two measurements: the image of the ball with the illumination illuminator and without illumination is recorded. Both data sets, taking into account the calibration parameters of the equipment, are processed on a computer and their element-wise subtraction is performed. This eliminates the influence on the reflective characteristics of the intrinsic (thermal) radiation of the ball and the radiation reflected from it from the surrounding space.

FIG. 4 shows an example of photometry of one of the obtained images of a sphere). The luminance distributions (in relative units) are shown over the cross sections of the image of a sphere corresponding to constant x coordinate values (Fig. 3). The numbers on the curves indicate the x / R values to which they correspond (for the sake of clarity and to avoid unnecessarily cumbersome only data sampling at x & O) is far from complete. Similar results were obtained for other scattering angles: up in increments of 15 °. Processing by expressions (1) - (4) of the received data arrays, similar to that shown in FIG. 4, and the reorganization of these arrays, performed on a computer, makes it possible to determine the indicatrices L (9 "; 9ts, ($ c) for the coating studied (reliable: results obtained for ranges of angles 0, bn Ј 83 °). The given% example shows the high efficiency of the measurement method, especially when using scanning photometers complete with computer-controlled computing systems.Thus, the advantages of the proposed measurement method are the following: no need to change the angular positions of the sample; your realizing

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instead of moving its elements along the three corners, there is only one movement: the angle between the optical axes of the illuminator and the photometer changes (the required rotation of the flat sample in two degrees of freedom in space corresponds to a different, uniform in space, orientation of the set of surface elements of the sphere separated by the elementary fields of view of the photometer, whose full field of view must encompass the entire sphere).

Claims (1)

A three-fold reduction in the required operations for changing the angular positions of the measuring device nodes in relation to the investment methods helps to simplify the measurement method. The method of measuring the indicatrix of the light scattering coatings, which consists in applying the investigated coating on the substrate, illuminating bgo with a uniform beam of radiation, measuring the brightness of the coating from different directions at discretely varying angles between the optical axis of the illuminator and the photometer, Fig 50 50 The angular coordinates of the illuminator and photometer in the coordinate system associated with the normal to the surface of the sample and the plane of incidence of radiation, characterized in that, in order to simplify the method, the test coating is applied to the surface of the substrate in the form of a sphere to obtain an image of a sphere in the plane sensitive element of the photometer. determine the center of the circle image of the sphere and the radius of the circle, find the axis of symmetry of the image of the illuminated part of the sphere, impose on the image a rectangular coordinate system, the beginning of which coincides with the center of the circle of the image of the sphere, and one of the axes coincides with the axis of symmetry of the image of the illuminated part of the sphere the luminance of the coating elements in the image of the illuminated part of the sphere, and the determination of the angular coordinates of the illuminator and photometer for each measured element of the substrate coating is carried out in two linear coordinates its image in the coordinate system superimposed on the image of the sphere and the angle between the optical axes of the illuminator and the photometer Fig z FIG. 3 05 P