Diffusely reflective materials with a reflectance. Optics. The law of reflection of light. Reflection coefficient. Diffuse reflectance measurement

The surface of objects rendered with a simple Lambertian diffuse reflection lighting model looks faded and matte. It is assumed that the source is point, and therefore objects that are not directly hit by light appear black. If the source is a point source and is a narrow beam, then:
I = I l * k d * cosq * cos c b , where
b is the angle formed by the searchlight beam and the direction to the point (see ),
c - coefficient of narrowness: the more with, the already a bunch.
The law does not take into account scattered light.

However, the objects of real scenes are also affected by scattered light reflected from objects in the environment, for example, from the walls of a room. Scattered light corresponds to a distributed source. Since such sources require large computational costs to calculate, in computer graphics they are replaced by the intensity factor for scattered light, a constant that enters the formula in a linear combination with the Lambert term:
I = I a * k a + I l * k d * cosq , where
I a is the scattered light intensity,
k a is the intensity factor for scattered light (0<= k a <= 1).

Let two objects be given, equally oriented relative to the source, but located at different distances from it. If you find their intensity according to this formula, then it will be the same. This means that when objects overlap, they cannot be distinguished, although the intensity of the light is inversely proportional to the square of the distance from the source, and the object lying further from it should be darker.

If we assume that the light source is at infinity, then the diffuse term of the illumination model will turn to zero. In the case of a perspective transformation of the scene, the distance r from the projection center to the object can be taken as a proportionality factor for the diffuse term. But if the projection center lies close to the object, then 1/r 2 changes very quickly, that is, for objects lying approximately at the same distance from the source, the intensity difference is excessively large.

As experience shows, greater realism can be achieved with linear attenuation. In this case, the illumination model looks like this:
I = I a * k a + (I l * k d * cosq * cos c b )/(r + const),
r it is necessary that there is no disco effect (effect of abrupt transitions),
const - so that division by zero does not occur.

If the viewpoint is assumed to be at infinity, then r is determined by the position of the object closest to the viewpoint. This means that the nearest object is illuminated at the full intensity of the source, and more distant objects at a reduced intensity. For colored surfaces, the lighting model is applied to each of the three primary colors: red (R), green (G), and blue (B).

The values ​​of the reflection coefficients of some specific surfaces are given in Table. 5.

Due to the fact that objects with different brightness can fall into the field of view, it is introduced concept of adaptive brightness (B a ), which is understood as the brightness to which the visual analyzer is adapted (tuned) at a given time. Approximately, we can assume that for images with direct contrast, the adaptive brightness is equal to the brightness of the background, and for images with reverse contrast, it is equal to the brightness of the object. The sensitivity range of the visual analyzer is very wide: from 10 -6 to 10 6 cd/m 2 . The best working conditions correspond to the levels of adaptive brightness ranging from several tens to several hundreds cd/m 2 .

Table 5

The values ​​of the reflection coefficients of some surfaces

It should be borne in mind that providing the required contrast value is only a necessary, but still insufficient condition for the normal visibility of objects. You also need to know how this contrast is perceived in given conditions. For its assessment of the visual perception of objects, the concept is introduced threshold contrast :

where  B since - threshold brightness difference, i.e. the minimum difference between the brightness of the object and the background, which is still detected by the eye. Thus, the value To since determined by the differential discrimination threshold. To obtain an optimal operational discrimination threshold, it is necessary that the actual value of the difference between the brightness of the object and the background be 10–15 times greater than the threshold value. This means that for normal visibility, the contrast value calculated by formulas (1) must be greater than the value To since 10 - 15 times. Thus, the ratio of the contrast value of the object of observation to its value (characteristic of the ability of the eye to perceive the object) is called visibility :

. (4)

The value of the threshold contrast depends on the brightness of the background and on the angular dimensions α about observation of objects. It should be noted that larger objects are visible at lower contrasts, and that the required threshold contrast decreases with increasing brightness.

For an approximate estimate of the magnitude of the direct threshold contrast, the paper proposes an empirical formula:

, (5)

where: α about is the angular size (measured in arc minutes) of the observed object (see Fig. 4 below). Functional coefficients φ 1 (α about ) and φ 2 (α about ) depend on the angular size of the observed object and the brightness of the background:

; (5 1)

for 0,01 ≤ B f ≤ 10 – k φ1 = 75;

; (5 2)

for B f > 10 – k φ1 = 122;

; (5 3)

k φ2 = 0,333; ξ = 3,333; p 0 = –0,096, p 1 = –0,111, p 2 = 3,55∙10 – 3 , p 3 = –4,83∙10 – 5 , p 4 = 1,634∙10 – 7 ; q 0 = 2,345∙10 – 5 , q 1 = –0,034, q 2 = 1,32∙10 – 3 , q 3 = –2,053∙10 – 5 , q 4 = 7,334∙10 – 4 .

Formulas (5 1) - (5 3) are obtained as a result of the approximation of the tabular values ​​of the functional coefficients φ 1 (α about ) and φ 2 (α about ) , given in .

To estimate the value of the inverse threshold contrast for 1′ ≤ α about ≤ 16′ an approximation of another empirical formula is proposed:

, (6)

where: r 0 = –0,51, r 1 = -0,151, r 2 = 3,818∙10 –3 , r 3 = –3,94∙10 –5 , r 4 = –1,606∙10 –7 , r 5 = 2,095∙10 –10 .

When the angular sizes of the observed objects exceed 16 arc minutes ( α about > 16′), you can use the formula:

, (6′)

where K por(16′) is the threshold contrast value calculated by formula (6) for α about = 16′ .

The relationship between the angular and linear dimensions of the observed objects for the general case is illustrated in Fig. . 4, where: l about –linear size of the observed object; l x and l y are the distances from the observation point (the location of the human eye) to the center of the observed object, taken horizontally and vertically, respectively; β about is the angle of deviation of the plane of the observed object from the horizontal. Quantities l about ,l x ,l y and β about determined by the characteristics and organization of a particular workplace. The rest, indicated in Fig. 4 quantities are auxiliary: l embankment is the direct distance from the observation point to the center of the observed object; h embankment is the normal distance from the observation point to the plane of the observed object; β embankment is the angle of view relative to the plane of the observed object; α 1 and α 2 - auxiliary corners.

Rice. 4. Connection of angular ( α ) and linear ( l about) sizes of observed objects

The geometry of the drawing in fig. 4 defines the following expressions for auxiliary quantities:

;
; (7)

;
(8)

and, therefore, the angular size of the observed object can be determined as:

α about = α 2 – α 1 . (9)

The magnitude of external illumination has a great influence on the conditions of visibility of objects. However, this effect will be different when working with images that have direct or reverse contrast. An increase in illumination with direct contrast leads to an improvement in visibility conditions (value To etc increases) and, conversely, with reverse contrast - to a deterioration in visibility (the value To about decreases).

With an increase in illumination, the value To etc increases because the brightness of the background increases more than the brightness of the object (the reflectance of the background is greater than the reflectance of the object). Value To about at the same time, it decreases, since the brightness of the object practically does not change (the object glows), and the brightness of the background increases.

In many cases, light signals of varying intensity may be in the operator's field of vision. At the same time, excessively bright objects can cause an undesirable state of the organs of vision - blindness. especially strong Negative influence the work of the organs of vision is affected by elements with high brightness, which can be excessively bright parts of lamps (for example, the filament of incandescent lamps) or other light sources - direct action, as well as their mirror reflections - reflected action. Blinding brightness is determined by the size and brightness of the luminous surface, as well as the level of brightness of adaptation of the organs of vision. The minimum brightness levels that begin to cause a blinding effect can be approximately determined by the empirical formula:

, (10)

where Ω cn is the solid angle of observation of the luminous surface by the operator (in steradians), the value of which can be approximately determined as the ratio of the area of ​​the luminous surface to the square of the distance from this surface to the organs of vision.

It should be borne in mind that the actual brightness levels of the observed objects should be estimated using formulas (2) and (3), and with the help of formula (10) only a check of the actual brightness levels for the appearance of a blinding effect can be carried out. For normal perception of the brightness of the observed objects, it is necessary that the following inequality is fulfilled:

B cn < B cn min , (11)

where B cn is the brightness of the blinding surface, determined by formulas (2) - (3).

Thus, in order to create optimal conditions for visual perception, it is necessary not only to ensure the required level of brightness and contrast of perceived light signals, but also to eliminate excessive uneven distribution of brightness in the field of view. In cases where it is impossible to use formula (9), you can use the data in Table. 6 or consider the uneven distribution of brightness levels in the field of view as acceptable if their difference does not exceed 1 to 30 .

Table 6

Years' works. Voloshin Maximilian. THE VALOR OF THE POET. 1. Edit the poem like the text of an overseas dispatch: Dryness, clarity, pressure - every word is on the alert.

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M., ; Red Smoke: Tales. - M.,; Gladyshev from reconnaissance: Tales. - M.,; Echelon; Inevitability: Novels. He did a lot of translations of Mari and Udmurt poets. From time to time he also tried his hand at prose. Op. Maximilian Aleksandrovich Voloshin () - one of major poets the first third of the 20th century. This is a talented artist, a multifaceted lyricist, who has gone from symbolist, esoteric poems to civil-journalistic and scientific-philosophical poetry, through anthroposophical predilections - to the “ideal of the City of God”.

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You must log in within 24 hours. Otherwise, the account will be deleted! Registered users get a lot of benefits: Publish poetry - realize your talent! Create selected collections of authors and poems! Chat with like-minded people! Write reviews, participate in poetic duels and contests!. Maximilian Voloshin. Description. Maximilian Aleksandrovich Voloshin is one of the greatest poets of the first third of the 20th century.

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Selected works and letters. M. A. Voloshin. Price. rub. Maximilian Aleksandrovich Voloshin is one of the greatest poets of the first third of the 20th century. This is a talented artist, a multifaceted lyricist, who has gone from symbolist, esoteric poems to civil-journalistic and scientific-philosophical poetry, through anthroposophical predilections - to the "ideal of the City of God."

Voloshin M.A., Valor of the poet: Selected works and letters. series: New Library of Russian Classics: obligatory copy Parade, g., p., Description of the book. Maximilian Aleksandrovich Voloshin () is one of the greatest poets of the first third of the 20th century. This is a talented artist, a multifaceted lyricist, who has gone from symbolist, esoteric poems to civil-journalistic and scientific-philosophical poetry, through anthroposophical predilections - to the “ideal of the City of God”.

INTERSTATE STANDARD

PAPER,

CARDBOARD AND PULP

MEASURING THE DIFFUSE REFLECTION COEFFICIENT

Official edition

INTERSTATE COUNCIL FOR STANDARDIZATION, METROLOGY AND CERTIFICATION

Foreword

1 DEVELOPED by the Ukrainian Research Institute of Pulp and Paper Industry (UkrNIIB)

INTRODUCED State Committee of Ukraine on standardization, metrology and certification

2 ADOPTED by the Interstate Council for Standardization, Metrology and Certification on October 21, 1994, (Minutes No. 6-94)

3 This International Standard is the complete authentic text international standard ISO 2469-77 Paper, paperboard and pulp. Measurement of the diffuse reflection coefficient” with additions reflecting the needs of the national economy (highlighted in italics in the text)

4 Decision of the Committee Russian Federation on standardization, metrology and certification dated July 25, 1996 No. 480 interstate standard GOST 30116-94 (ISO 2469-77) was put into effect directly as state standard Russian Federation since January 1, 1997

5 INSTEAD OF GOST 7690-76 in part general requirements to measuring instruments

© IPK Standards Publishing House, 1997

This standard cannot be fully or partially reproduced, replicated and distributed as an official publication on the territory of the Russian Federation without the permission of the State Standard of Russia

1 Scope .................................................1

3 Definitions..............................................1

4 Equipment and materials...............................2

4.1 Reference instruments and measuring instruments ..........2

4.2 Initial exemplary measuring instruments ............... 3

4.3 Reference measuring instruments for diffuse reflectance .............................................................3

4.4 Working gauge plates....................................

4.4.1 Calibration of working gauge plates..........

4.4.2 Use of work plates..........................

4.4.3 Washing the working calibration plates.......................

5 Sampling ...............................................

6 Preparing specimens for testing ..............................

7 Testing ..............................................

8 Processing the results....................................

Annex A Initial exemplary measuring instruments

whiteness from barium sulphate ........

A.1 Instruments and materials ..........................

A.2 Manufacture of tablets from barium sulphate ........

A.3 Quality requirements for barium sulphate tablets. . .

GOST 30116-94 (ISO 2469-77)

INTERSTATE STANDARD

PAPER, CARDBOARD AND PULP Diffuse reflectance measurement

Paper, board and pulp. Measurement of diffuse reflection iactor

Introduction date 1997-01-01

1 AREA OF USE

1 This International Standard applies to paper, paperboard, pulp and specifies requirements for the measurement of diffuse reflectance used to determine the whiteness of pulp, paper, paperboard and the opacity of paper.

GOST 2603-79 Acetone. Specifications

GOST 3158-75 Barium sulfate. Specifications

GOST 6709-72 Distilled water. Specifications

GOST 7004-93 Cellulose. Sampling for testing

GOST 8047-93 Paper and cardboard. Acceptance rules. Sampling to determine average quality

GOST 24104-88 Laboratory balance general purpose and exemplary. General specifications

3 DEFINITIONS

For the purposes of this International Standard, the following terms apply with their respective definitions:

3.1 Diffuse reflection coefficient R is the ratio of the radiation flux reflected by the body to the radiation flux reflected in

Official edition

under the same conditions with an absolute reflective diffuser, expressed as a percentage.

3.2 Own factor diffuse reflectance Du - the diffuse reflectance of a layer of material or an opaque foot.

3.3 The state special standard of units of color coordinates and chromaticity coordinates is an absolute reflective diffuser, the diffuse reflection coefficient of which is equal to one.

3.4 Initial exemplary instrument for measuring the diffuse reflectance coefficient - a set of exemplary measures, consisting of standard samples having nominal diffuse reflectance values ​​from 6C to 95%, certified using the state special standard of units of color coordinates and color coordinates.

The original exemplary measuring instrument is used for certification and verification of sets of standard samples of the diffuse reflection coefficient.

3.5 Exemplary instrument for measuring the diffuse reflection coefficient - a set of standard samples with nominal values ​​of the diffuse reflection coefficient from 60 to 95%, certified by the method of comparison with the original exemplary measuring instrument.

An exemplary measuring instrument is used for primary and periodic verification of instruments for measurements such as photometers, as well as for periodic calibration of working calibration plates.

4 EQUIPMENT AND MATERIALS

4.1 Reference instruments and measuring instruments

To measure the diffuse reflectance in the determination of whiteness and opacity, a photometric instrument is used that meets the following requirements:

The instrument shall either diffusely illuminate the surface of the standard or test specimen with light from a photometric ball and measure the luminous flux reflected perpendicular to the surface of the standard or test specimen, or illuminate the surface of the standard or test specimen with a directed light beam incident perpendicular to the surface of the standard or test specimen and measure from - luminous flux - with the help of a photometric ball;

The total area of ​​the holes of the photometric ball should not exceed 10% total area its surface;

The opening of the receiving device must allow testing of samples with a diameter of at least 30 mm;

A black ring must be installed on the opening of the receiving device, the inner diameter of which equal to the diameter holes of the receiving device, and the outer diameter allocates a solid angle with a semi-angle at the top (15.5 ± 0.5) ° relative to the center of the hole for the test sample;

Only the reflected beams contained within the cone, the apex of which is on the surface of the test specimen and the semi-angle at the apex of which does not exceed 4°, shall pass through the opening of the receiving device;

The error of the instrument due to non-linearity after calibration should not exceed 0.3% of the value of the diffuse reflection coefficient;

The spectral characteristics of filters should be specified in the standards for specific test methods, since the choice of filters depends on the optical index (whiteness, opacity) determined based on the measurement of the diffuse reflectance;

Standard calibration plates must be included with the instrument.

Note - Setting up the device and measuring the diffuse reflection coefficient must be carried out in accordance with the instruction manual for the device. Depending on the filter used, the values ​​of the diffuse reflection coefficient will differ.

4.2 Initial exemplary measuring instruments

Initial exemplary means of measuring the coefficient

diffuse reflection - freshly prepared tablets obtained by pressing from barium sulfate powder according to GOST 3158 h.d.a. (Appendix A) or plates of reflective neutral glass, which diffusely reflects all the rays of light falling on it.

The original exemplary measuring instruments with a known diffuse reflectance are used to calibrate the exemplary instruments of industry and basic metrological laboratories and to certify exemplary measuring instruments for the diffuse reflectance to determine whiteness and opacity.

4.3 Reference measuring instruments for diffuse reflectance

Exemplary measuring instruments must be made of neutral glass, which diffusely reflects all rays of light incident on it, or other equivalent material and meet the following requirements:

The value of the diffuse reflectance should be close (within 10%) to the diffuse reflectance of the tested product sample and should remain constant throughout the entire service life;

Must have the same diffuse reflectance over the entire surface;

The surface should be matte, smooth, but not shiny, should not contain luminescent impurities.

Exemplary instruments for measuring the diffuse reflection coefficient are used for primary and periodic verification of instruments and must be certified once a year.

Standard measuring instruments for diffuse reflectance should be stored in dark place in solid packaging, work surface must be protected from contamination.

4.4 Working check plates

Working calibration plates ~ two plates, which must be made of neutral glass or other equivalent material that diffusely reflects all the rays of light falling on it, and calibrated on a reference instrument; used to set up the device.

The value of the diffuse reflectance of the working calibration plates should be close (within 10%) to the diffuse reflectance of the product under test.

4.4.1 Calibration of work plates

Working calibration plates are calibrated with standard or original standard measuring instruments for the diffuse reflection coefficient.

4.4.1.1 Working calibration plates are periodically calibrated on a working device with exemplary measuring instruments with an error of ± 0.1%. The diffuse reflectance of the working test plate is determined as the average arithmetic value three measurements, which should not differ by more than 0.3% of the diffuse reflectance value of the reference measuring instrument.

4.4.1.2 Working calibration plates are calibrated on the instrument with original standard measuring instruments with an error of ±0.1%.

4.4.2 Use of work plates

One test plate should be used as a working test plate and the other as a reference.

Before each series of measurements, the working calibration plate must be checked with a control one.

If the values ​​of the diffuse reflectance of the working calibration and control plates differ, then they are washed in accordance with the requirements set out in 4.4.3.

If the difference in the values ​​of the diffuse reflection coefficients after washing remains, then the control and working calibration plates are calibrated with exemplary measuring instruments.

4.4.3 Washing the working calibration plates

The plates are washed in distilled water according to GOST 6709 with a soft brush made of synthetic fiber detergent containing no luminescent substances, rinsed with distilled water and dried.

5 SAMPLING

5.1 Pulp sampling - according to GOST 7004, paper and cardboard - according to GOST 8047.

6 PREPARATION OF SPECIMENS FOR TESTS

6.1 Preparation of samples for testing should be carried out in accordance with the requirements of the standard for the method for determining a specific indicator.

7 TESTING

7.1 The spectral characteristic of the radiation is set using a light source and filters, depending on the optical index to be determined.

7.2 Testing - in accordance with the standard for the method for determining a specific indicator.

8 PROCESSING THE RESULTS

8.1 Processing of results - in accordance with current normative documents on the method of determining a specific indicator.

APPENDIX A (informative)

Initial exemplary means of measuring whiteness from barium sulphur.

The initial exemplary means of measuring ^ lys are tablets from powder of barium sulfate, obtained by<5 сования и сна бженные свидетельством, в котором указаны спектральные коэффиц иенты диф ф узного отражения для оптической геометрии прибора, соответствующей ч, настояшего стандарта.

A certificate with the specified characteristics of the kTTCCTawli measuring media is issued by special laboratories.

A.1 Instruments and materials

A!, 1 Powder of barium sulfate must comply with GOS T,

3158. The value of the diffuse reflection coefficient ^ serH of barium oxide must be determined by specially created laboratories ^

A.1.2 Sernokisba tablet press Dimensions of tablets: diameter - 45 mm, thickness - 5 mm.

Note - A press that meets the requirements ^ d, 2 manufactured by the company

^UGT^ K5 2 Lr " nK, Spit ^ ^" Loroshkovs* ggrs-ss 431.

A. 1.3 Porcelain spoon.

ALA Soft synthetic fiber brush.

AL.5 Synthetic detergent, not containing fluorescent substances.

AL.6 Acetone, analytical grade according to GOST 2603.

AL.7 Distilled water according to GOST 6709.

A. 1.8 Laboratory scales for general purposes according to G ost 24Sh4 with absolute according to. weighing error ±0.001 g.

A.2 Manufacture of tablets from barium sulfate

A.2.1 The press must be clean and dry.

A.2.2 For the manufacture of one tablet, 12 g of barium sulphate is needed.

A.2.3 Powder for tablet compression should be > chabi with a porcelain spoon.

A.2.4 The mold of the press is filled with sulphuric acid powder, covered with a glass plate with a matte surface and pressed

A.2.5 Remove the frosted glass plate from the working surface formed as a result of tablet pressing. The finished tablet is carefully removed and visually inspected under grazing light. The working surface of the tablet should be matte, smooth, and should not have shiny, deep depressions or elevations.

Prepare two or three tablets. The values ​​of the diffuse reflectance coefficients of finished tablets should differ by no more than ±0 j %. otherwise, the tablets are not made correctly.

A.2.6 After the tablet has been made, the mold is carefully washed with a brush with distilled water and synthetic detergent and air dried.

^ ^ 1 ^ 1 in a closed container. Not

it is allowed to pour the rest of the powder into a container in which it is stored

A.3 Quality requirements for sulfate tablets

A.3.1 Diffuse reflectance values ​​for finished tablets

prepared from barium sulphate stored in the same container, should not differ from each other by more than ± 0.1% and must correspond to the value indicated on the container.

A.3.2 The value of the diffuse reflectance of the tablets should not change within two weeks.

A.3.3 The value of the diffuse reflectance of tablets should not change with changes in air humidity.

NOTE The diffuse reflectance values ​​of correctly prepared tablets over the entire visible range with a wavelength of 400-700 nm should be as determined by special laboratories in relation to an absolute reflective scatterer.

UDC 676.1.06.001.4:006.354 OKS 88.040; 85.060 K69 OKP 54 0000

Key words: paper, cardboard, diffuse reflectance, materials, interstate standard, definitions, devices, terms, cellulose

Editor T.S.Sheko Technical editor V.I. Prusakova Proofreader V.S.

Ed. persons. No. 021007 dated 10.08.95. Handed over to the set 11/26/96. Signed for publication on 12/19/96. Conditions.print.l. 0.70. Uch.-ed.l.0.55. Circulation 204 copies. C 4159. Law. 695.

IPK Standards Publishing House 107076, Moscow, Kolodezny per., 14.

Typed at the Publishing House on a PC

Branch of IPK Publishing house of standards - type. "Moscow printer"

GOST 30116-94
(ISO 2469-77)

Group K69

INTERSTATE STANDARD

PAPER, CARDBOARD AND PULP

Diffuse reflectance measurement

Paper, board and pulp. Measurement of diffuse reflection factor

OKS 88.040; 85.60
OKP 54 0000

Introduction date 1997-01-01

Foreword

1 DEVELOPED by the Ukrainian Research Institute of Pulp and Paper Industry (UkrNIIB)

INTRODUCED by the State Committee of Ukraine for Standardization, Metrology and Certification

2 ADOPTED by the Interstate Council for Standardization, Metrology and Certification on October 21, 1994 (minutes N 6-94)

Voted to accept:

3 This standard is the full authentic text of the international standard ISO 2469-77 "Paper, paperboard and paper pulp - Measurement of diffuse reflectance" with additions reflecting the needs of the national economy (in the text italicized)

4 By Resolution of the Committee of the Russian Federation for Standardization, Metrology and Certification of July 25, 1996 N 480, the interstate standard GOST 30116-94 (ISO 2469-77) was put into effect directly as the state standard of the Russian Federation from January 1, 1997.

5 TO REPLACE GOST 7690-76 in terms of general requirements for measuring instruments

1 AREA OF USE

1 AREA OF USE

1 This International Standard applies to paper, paperboard, pulp and specifies requirements for the measurement of diffuse reflectance used to determine the whiteness of pulp, paper, paperboard and the opacity of paper.

2 REGULATORY REFERENCES

This standard uses references to the following standards:

GOST 2603-79 Acetone. Specifications

GOST 3158-75 Barium sulfate. Specifications

GOST 6709-72 Distilled water. Specifications

GOST 7004-93 Cellulose. Sampling for testing

GOST 8047-93 Paper and cardboard. Acceptance rules. Sampling to determine average quality

GOST 24104-88* Laboratory scales for general purposes and exemplary. General specifications
_________________
* GOST 24104-2001 is valid on the territory of the Russian Federation. - Note "CODE".

3 DEFINITIONS

For the purposes of this International Standard, the following terms apply with their respective definitions:

3.1 Diffuse reflection coefficient - the ratio of the radiation flux reflected by the body to the radiation flux reflected under the same conditions by an absolute reflective diffuser, expressed as a percentage.

3.2. Intrinsic diffuse reflectance - the diffuse reflectance of a layer of material or an opaque stack.

3.3. The state special standard of units of color coordinates and chromaticity coordinates is an absolute reflective diffuser, the diffuse reflection coefficient of which is equal to one.

3.4. The original exemplary instrument for measuring the diffuse reflection coefficient is a set of exemplary measures consisting of standard samples having nominal values ​​of the diffuse reflection coefficient from 60 to 95%, certified using the state special standard of units of color coordinates and color coordinates.

The original exemplary measuring instrument is used for certification and verification of sets of standard samples of the diffuse reflection coefficient.

3.5 Exemplary instrument for measuring the diffuse reflection coefficient - a set of standard samples with nominal values ​​of the diffuse reflection coefficient from 60 to 95%, certified by the method of comparison with the original exemplary measuring instrument.

An exemplary measuring instrument is used for primary and periodic verification of instruments for measurements such as photometers, as well as for periodic calibration of working calibration plates.

4 EQUIPMENT AND MATERIALS

4.1 Reference instruments and measuring instruments

To measure the diffuse reflectance in the determination of whiteness and opacity, a photometric instrument is used that meets the following requirements:

- the instrument shall provide diffuse illumination of the surface of the standard or test specimen with light from a photometric ball and measurement of the light flux reflected perpendicular to the surface of the standard or test specimen, or illumination of the surface of a standard or test specimen with a directed beam of light incident perpendicular to the surfacestandard or test sample, and measurement of the reflected light flux - using a photometric ball;

- the total area of ​​the holes of the photometric ball should not exceed 10% of the total area of ​​its surface;

- the opening of the receiving device must allow testing samples with a diameter of at least 30 mm;

- a black ring shall be installed on the opening of the receiving device, the inner diameter of which is equal to the diameter of the opening of the receiving device, and the outer diameter allocates a solid angle with a half-angle at the apex (15.5 ± 0.5) ° relative to the center of the hole for the test sample;

- only reflected beams contained inside a cone, the apex of which is located on the surface of the test specimen and the semi-angle at the apex of which does not exceed 4°, shall pass through the opening of the receiving device;

- instrument error due to non-linearity after calibration should not exceed 0.3% of the diffuse reflection coefficient value;

- spectral characteristics of light filters should be specified in the standards for specific test methods, since the choice of light filters depends on the optical index (whiteness, opacity) determined on the basis of measuring the diffuse reflection coefficient;

- standard calibration plates must be included in the instrument set.

Note - Setting up the device and measuring the diffuse reflection coefficient must be carried out in accordance with the instruction manual for the device. Depending on the filter used, the values ​​of the diffuse reflection coefficient will differ.

4.2 Initial exemplary measuring instruments

The initial exemplary measuring instruments for the diffuse reflection coefficient are freshly prepared tablets obtained by pressing from barium sulfate powder according to GOST 3158 analytical grade. (Appendix A) or plates of reflective neutral glass, which diffusely reflects all the rays of light falling on it.

The original exemplary measuring instruments with a known diffuse reflectance are used to calibrate the exemplary instruments of industry and basic metrological laboratories and to certify exemplary measuring instruments for the diffuse reflectance to determine whiteness and opacity.

4.3 Reference measuring instruments for diffuse reflectance

Exemplary measuring instruments must be made of neutral glass, which diffusely reflects all rays of light incident on it, or other equivalent material and meet the following requirements:

- the value of the diffuse reflectance must be close (within 10%) to the diffuse reflectance of the tested product sample and must remain constant throughout the entire service life;

- must have the same diffuse reflectance over the entire surface;

- the surface should be matte, smooth, but not shiny, should not contain luminescent impurities.

Exemplary instruments for measuring the diffuse reflection coefficient are used for primary and periodic verification of instruments and must be certified once a year.

Exemplary instruments for measuring the diffuse reflection coefficient should be stored in a dark place in a solid package, their working surface must be protected from contamination.

4.4 Working check plates

Working calibration plates - two plates that must be made of neutral glass or other equivalent material that diffusely reflects all the rays of light falling on it, and calibrated on a reference instrument; used to set up the device.

The value of the diffuse reflectance of the working calibration plates should be close (within 10%) to the diffuse reflectance of the product under test.

4.4.1 Calibration of work plates

Working calibration plates are calibrated with standard or original standard measuring instruments for the diffuse reflection coefficient.

4.4.1.1 Working calibration plates are periodically calibrated on a working device with exemplary measuring instruments with an error of ± 0.1%. The diffuse reflectance of the working test plate is determined as the arithmetic mean of three measurements, which should not differ by more than 0.3% of the diffuse reflectance of the reference measuring instrument.

4.4.1.2 Working calibration plates are calibrated on the instrument with original exemplary measuring instruments with an error of ±0.1%.

4.4.2 Use of work plates

One test plate should be used as a working test plate and the other as a reference.

Before each series of measurements, the working calibration plate must be checked with a control one.

If the values ​​of the diffuse reflectance of the working calibration and control plates differ, then they are washed in accordance with the requirements set out in 4.4.3.

If the difference in the values ​​of the diffuse reflection coefficients after washing remains, then the control and working calibration plates are calibrated with exemplary measuring instruments.

4.4.3 Washing the working calibration plates

The plates are washed in distilled water according to GOST 6709 with a soft synthetic fiber brush with a detergent that does not contain luminescent substances, rinsed with distilled water and dried.

5 SAMPLING

5.1 Pulp sampling - according to GOST 7004, paper and cardboard - according to GOST 8047.

6 PREPARATION OF SPECIMENS FOR TESTS

6.1 Preparation of samples for testing should be carried out in accordance with the requirements of the standard for the method for determining a specific indicator.

7 TESTING

7.1 The spectral characteristic of the radiation is set using a light source and filters, depending on the optical index to be determined.

7.2 Testing - in accordance with the standard for the method for determining a specific indicator.

8 PROCESSING THE RESULTS

8.1 Processing of results - in accordance with the current regulatory documents for the method of determining a specific indicator.

APPENDIX A (informative). Initial exemplary means of measuring whiteness from barium sulfate

APPENDIX A
(reference)

The initial exemplary means for measuring whiteness are tablets made from barium sulfate powder, obtained by pressing and provided with a certificate indicating the spectral diffuse reflectance coefficients for the optical geometry of the instrument, in accordance with 4.1 of this standard.

A certificate with the specified characteristics of the attestation of measuring instruments is issued by special laboratories.

A.1 Devices and materials

A.1.1 Barium sulfate powder must comply with the requirements of GOST 3158. The value of the diffuse reflectance of barium sulphate must be determined by specially created laboratories.

A.1.2 Barium sulphate tablet press. Tablet sizes: diameter - 45 mm, thickness - 5 mm.

Note - A press that meets the requirements of A.1.2, manufactured by Carl Zeiss Ober Kochen, Germany, under the trade name "Powder Press 45".

A.1.3 Porcelain spoon.

A.1.4 Soft synthetic fiber brush.

A.1.5 Synthetic detergent free of luminescent substances.

A.2.3 Powder for tablet compression should be taken with a porcelain spoon.

A.2.4 The mold of the press is filled with barium sulfate powder, covered with a glass plate with a matte surface and pressed.

A.2.5 Remove the frosted glass plate from the working surface formed as a result of pressing the tablet. The tablet must be removed from the press mold intact. The finished tablet is carefully removed and visually inspected under gliding light. The working surface of the tablet should be matte, smooth, should not have shiny areas, depressions and elevations.

Prepare two or three tablets. The values ​​of diffuse reflection coefficients of finished tablets should differ by no more than ±0.1%; otherwise, the tablets are not made correctly.

A.2.6 After making the tablet, the press mold is thoroughly washed with a brush with distilled water and synthetic detergent and air dried.

A.2.7 Powder of barium sulfate should be stored in a closed container. It is not allowed to pour the remains of the powder into the container in which it is stored.

A.3 Quality requirements for barium sulfate tablets

A.3.1 The values ​​of the diffuse reflectance of finished tablets prepared from barium sulfate stored in the same container should not differ from each other by more than ± 0.1% and should correspond to the value indicated on the container.

A.3.2 The value of the diffuse reflectance of the tablets should not change within two weeks.

A.3.3 The value of the diffuse reflectance of tablets should not change with changes in air humidity.

NOTE The diffuse reflectance values ​​of correctly prepared tablets over the entire visible range with a wavelength of 400-700 nm should be as determined by special laboratories in relation to an absolute reflective scatterer.



The text of the document is verified by:
official publication
M.: IPK Standards Publishing House, 1997