SU750288A1 - Method of determining scattered reflecting power - Google Patents

Description

(54) METHOD OF DEFINITION OF DIFFUSE REFLECTION COEFFICIENT

one

The invention relates to the field of photometry, spectrophotometry and spectroscopy of light-scattering media and can be used to measure reflection coefficients and spectroscopy of weakly absorbing light. . highly scattering samples.

There is a known method for determining the diffuse reflectance factor, based on the fact that using photomet-. A diffuse illumination of the sample and the reference, placed in the center of the sphere, is created on the orb and the intensity of the radiation reflected along the surface 1 is recorded.

The disadvantages of this method are the need to place the sample and the reference in the photometric ball 20 and the luminosity is low.

The closest in technical essence to this image is a known method for determining the diffuse reflectance 25, based on the fact that the sample and the standard are illuminated with a directional beam of light normal to the surface and the intensity of the light reflected from them is measured f2.JQ

The test sample and the reference sample (standard) in this method are placed in a photometric ball, illuminated alternately along the normal to the surface with a directional light beam, angle integral diffusely reflected fluxes are measured, and the diffusion coefficient is determined by the ratio and known diffuse reflection coefficient of the standard reflection specimen.

This method requires that samples be placed in a photometric ball, therefore it cannot be used for measurements with samples of large sizes and in a continuous, for example, technological process.

The aim of the present invention is to expand the field of application of the method by providing the possibility of measuring the reflectance of samples of all sizes and in a continuous process.

This goal is achieved by recording the intensity of the radiation and Jj reflected from the sample and the reference at an angle of 0, V 65 ° to the normal, and determine the coefficient

diffuse reflection of the sample r "s according to the formula

.P J JirlSv

where is the diffuse reflectance of the standard.

This goal is also achieved if the illumination is made at an angle of О V 65 to the normal, and is recording the intensities and radiation reflected normal to the surface.

The drawing is a graph illustrating the error in determining the diffuse reflectance coefficient by the proposed method.

Studies have shown that when illuminating a semi-infinite scattering layer parallel to a beam of light at an arccos | Lip angle to the normal, the intensity of the radiation reflected at an arccosju angle at 1 (or 1 1) is described by the formula

, o (,,,,). (- K-;, „

where (SjUQ is the illumination created by the feeding beam on the surface of the layer; Ctf is the parameter depending on the scattering indicatrix of the elementary volume; is the parameter depending on the scattering indicatrix and the ratio between the absorption and scattering indices.

The diffuse reflection coefficient G when directed to an angle of arccos JUQ is equal to

, g-V4T {1 2.)

Accordingly, the diffuse reflection coefficient R under diffuse illumination is

.

Formulas (1) - (3) are applicable at H 0.4; about 0.4; 7 0.3.

It can be seen from formulas (1) - (2) 1 that illuminating the sample and the standard along the normal to the surface (ju 1) and recording the intensity of the reflected radiation of Hb and Hd at an angle V arccos | , you can determine the diffuse reflectance of the sample when illuminated by the normal by the formula

- l 2.5S 3T {3).

(M

It can be seen from formulas (1) - (2) that the same value can be determined by the same formula {if the sample and the light are illuminated with a directed light beam at an angle V to the normal, and the intensities of the reflected radiation Lo5 are recorded and normalized to the surface.

Note that by knowing the value on the basis of formulas (2) and (3), it is possible to determine the diffuse reflection coefficients of the sample under directional illumination T-o (o) at an arbitrary 5 angle arccos (o O) and under diffuse lighting formulas

jtgjMg on (o) - (Gob) 3, (5)

p, / „0.78. (6)

Example. To determine the diffuse reflectance of a scattering sample, the sample and the standard are illuminated normal to the surface and c the radiation intensities of the Craw and 3j reflected from the sample and the reference are recorded at an angle V 48 -. Let the diffuse reflectance coefficient of the reference when illuminated at a Tg-f of 0.95, and the meter readings proportional to the SOB and Zet f are respectively equal: NQ 60 divisions and N37 80 divisions. Then Gob 0.713.

By the formulas (5) and (6), it is also possible to calculate the Gob () and Kob1 + 2ND values

Q (),

ROS - The use of the proposed technical solution in comparison with the known one allows to measure the diffuse reflectance of samples of any size, to carry out measurements in a continuous mode and, in particular, to monitor industrial samples in a continuous process.

The error in determining the diffuse reflection coefficient by the proposed method is illustrated in the drawing, which shows the dependence of the measured reflection coefficient on the true one at two values of the angle V 0 ° and V 48 ° for samples with i different scattering indicatrices and different ratios between absorbance and scattering .

Circles show data, crosses - V 48 °, right -

Nm

The research and drawing show that the smallest error is provided at V 48.

Using formulas (5) (6), the proposed method also allows determining the diffuse reflectance of a sample) with directional illumination at an arbitrary angle arccos jUo and the diffuse reflectance Cob P diffuse illumination, widely used in diffuse reflectance spectroscopy 5.

Claims (2)

Claims 1. A method for determining the diffuse reflectance based on the fact that a sample and a standard are illuminated with a directional beam of light. normal to the surface and measure the intensity of the light reflected from them, characterized in that, in order to expand the field of application of the method by providing the possibility of measuring the reflection coefficient of samples of all sizes and in a continuous process, the radiation intensities 3 and reflected from the sample and etalozt on an angle of O C V 65 ° to the normal, and determine the diffuse reflectance of the sample by the formula , (t) 2coSV at Jst - coefficient of diffuse otgde Gat razheni standard. 2. The POP.1 method, characterized in that the illumination is produced at an angle O 1 jp 4 65 to the normal, and the intensities of the Zdb and Odt radiation reflected along the normal to the surface are recorded. . Information sources, taken into account in the examination 1. Ivanov A.P. Optics of scattering media. Minsk, Science and Technology, 1969, m.108. 2. Ivanov A.P. Optics of scattering media. Minsk, Science and Technology, 1969, p.98 (prototype).