RU2035721C1 - Method of checking transparency of flat light-translucent materials - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: material tested is illuminated by two identical parallel light beams at normal to its surface during material transportation under production. Flat white non-transparent substrate is disposed under one illuminated parts at the side being opposite to the material. Black substrate is disposed under the other part. Light fluxes φ_w and φ_o, are indicated which are dissipated by one and other parts of material at opposite direction in identical small solid angles Ω oriented at identical angles v to each incident beam. Transparency of the material is judged from dc = φ_o,э/φ_w,э-φ_o/φ_w, where φ_w,э and φ_o,э are light fluxes measured by the same method for standard sample of the same material with known transparency. EFFECT: improved precision of measurement. 6 dwg

Description

 The invention relates to methods for monitoring the physical parameters of flat light-transmitting materials, for example paper, and can be used for continuous quality control of a paper web directly during the manufacturing process of it.

 Closest to the claimed method is the standard method for measuring transparency adopted in the domestic paper industry, GOST 8874-72, according to which the paper sample under investigation is illuminated normally with a parallel light beam to its surface, light fluxes scattered by the sample in the opposite direction are successively measured in cases when either a flat opaque white or black substrate is placed on the opposite side of the sample, and the prose is calculated using the known formula Sample cleanliness.

 The disadvantages of the method include selectivity, the need to cut out samples, i.e. destruction of the finished product, the duration of the order of 5 minutes per measurement and, as a result, the inability to use the method for continuous quality control of the paper web directly during its production for operational intervention in the technological process, especially for its automation.

 The invention allows to increase the measurement speed and create a method suitable for continuous non-destructive testing of the quality of the paper web directly during the technological process of production of light-transmitting materials.

где Φ_ω,э и Φ _{о, э} аналогично измеренные световые потоки для эталонного образца того же материала известной прозрач- ности.This is achieved by the fact that the material under investigation is illuminated with two identical parallel light beams normally to its surface sequentially along the path of material drawing during its production, and a flat white opaque substrate is placed under one of the illuminated areas on the opposite side of the material, and black is recorded under the other, luminous fluxes Φ _ω and Φ _o scattered respectively by those and other sections of the material in the opposite direction in the same small solid angles Ω oriented at the same angles φ to each of the incident beams, and the transparency of the investigated material is judged by the difference
δχ

where Φ _{ω, e} and Φ 0 _{, e are} similarly measured light fluxes for a reference sample of the same material of known transparency.

 In FIG. 1 is a diagram for controlling the transparency of planar light-transmitting materials; figure 2 presents a section aa in figure 1; figure 3 section BB in figure 1; figure 4 shows a laboratory installation for implementing the proposed method; figure 5 shows a graph for determining the transparency of the sample; figure 6 shows a device for controlling the transparency of a sample installed directly at the output of a paper machine.

скорости протяжки изображено на фиг.1 стрелкой, а на фиг.2 и 3 символом

(от наблюдателя). Под световым пучком 2 с противоположной стороны от материала помещают плоскую белую (рассеивающую) непоглощающую подложку 4 ("белый" участок материала), а под световым пучком 3 такую же черную подложку 5 поглощающую ("черный" участок). Свет, рассеянный "белым" и "черным" участками материала в обратном направлении, регистрируют в пределах одинаковых малых телесных углов 6 и 7 (Ω < < 2 π), при этом каждый из телесных углов ориентирован в плоскости, перпендикулярной к направлению протяжки материала, под одним и тем же углом φ к каждому из падающих пучков.The studied material 1, for example, a moving paper web (paper), is illuminated with two identical parallel light beams 2 and 3 normally to its surface sequentially along the path of material broaching during its production. Vector direction

drawing speed is shown in figure 1 by an arrow, and in figures 2 and 3 by a symbol

(from the observer). A flat white (scattering) non-absorbing substrate 4 (“white” section of the material) is placed under the light beam 2 on the opposite side of the material, and under the light beam 3, the same black substrate 5 is absorbing (the “black” section). Light scattered by the “white” and “black” sections of the material in the opposite direction is recorded within the same small solid angles 6 and 7 (Ω <<2 π), with each of the solid angles oriented in a plane perpendicular to the direction of the material’s pulling, at the same angle φ to each of the incident beams.

 To verify the operability of the method, a laboratory setup (Fig. 4) was assembled, including a radiation source 8, a lens 9, a photodetector 10, a white substrate 4, a black substrate 5, an amplifier 11, an analog-to-digital converter 12, an indicator board 13, a casing 14, a modulator fifteen.

 The installation works as follows.

The light from source 8 (IR LED AL-107), passing through the lens 9, normally falls in parallel beam onto the surface of the test material 1, the diameter of the light spot on the paper (material) was about 1 cm. On the opposite side of the paper, it is placed either flat under the spot white backing 4 (whatman 5x5 cm ² ), or black backing 5 (black velvet). The light scattered by the paper in the opposite direction is captured by the photodetector 10 (photodiode FD-256) with a photodetector surface diameter of about 3 mm. The photodetector is located in a plane perpendicular to the machine direction of the paper, at a distance of about 5 cm from the spot of light, while the angle between the incident beam and the direction to the center of the photodetector is φ 40 ^about . The photo signal I from the photodetector is amplified by an amplifier 11, converted to digital form using an analog-to-digital converter 12 and displayed on a display panel 13. To eliminate the influence of possible spurious illumination, the photometric part of the installation is enclosed in a translucent blackened casing 14. In addition, for the same purpose, the source light is modulated by a modulator 15, which simultaneously controls the amplifier, providing synchronous detection of only the useful signal.

где Φ _о,пр световой поток, рассеянный калькой в обратном направлении в телесном угле 2 π при черной подложке;
Φ_∞,пр аналогичный световой потолок при белой подложке, в качестве которой использовалась непрозрачная (бесконечно толстая) стопа той же кальки.Using the described setup, measurements were made on tracing paper samples produced by the Leningrad Paper and Cardboard Factory Kommunar of various transparency, which was previously measured at the factory quality laboratory on a leukometer according to the prototype method, according to which it was calculated by the formula
χ _ol = 1-

where Φ _{о, pr is the} light flux scattered by tracing paper in the opposite direction in a solid angle of 2 π with a black substrate;
Φ _{∞, a} similar light ceiling with a white substrate, which was used as an opaque (infinitely thick) foot of the same tracing paper.

1-

для разных участков исследованных образцов.At the setup, the photosignals I _ω and I _о were measured, which are proportional to the light fluxes Φ _ω and Φ _o scattered by tracing paper in the direction of the photodetector with a white and black substrate, respectively. The transparency of tracing paper was determined by the formula
χ 1-

1-

for different sections of the studied samples.

Заявляемый способ контроля прозрачности может быть реализован, например, в устройстве для контроля прозрачности кальки, предназначенном для установки непосредственно на выходе бумагодалительной машины (фиг.6). Устройство включает в себя модулятор 15, источник 8 излучения, линзу 9, полупрозрачное зеркало 16, зеркало 17, два идентичных фотоприемника 10, два одинаковых кожуха 14, белую 4 и черную 5 подложки, усилитель 11, аналого-цифровой преобразователь 12, блок 18 обработки, запоминающее устройство 19 и индикаторное табло 13.Comparative results of the measurements are shown in figure 5, where the horizontal values and the confidence errors (p 0.95) of transparency χ _pr , samples measured by the prototype method, and the vertical values of transparency χ of the same samples measured in the laboratory installation by the proposed method. Figure 5 shows that there is a linear relationship between both transparencies, which makes it possible to judge the transparency of any paper under investigation by the difference δχ χ χ _{e of} its transparency χ and the transparency χ _{e of a} sample of the same paper taken as a standard, measured by the present method. It can be seen that the magnitude of this difference is reduced to the following form:
δχ χ-χ _e =

The inventive method of controlling transparency can be implemented, for example, in a device for controlling the transparency of tracing paper, designed to be installed directly at the output of a paper machine (Fig.6). The device includes a modulator 15, a radiation source 8, a lens 9, a translucent mirror 16, a mirror 17, two identical photodetectors 10, two identical casings 14, a white 4 and a black 5 substrate, an amplifier 11, an analog-to-digital converter 12, a processing unit 18 , a storage device 19 and an indicator board 13.

 The device operates as follows.

The radiation source 8 (IR LED, for example, type AL-107) is fed from the modulator 15 by a pulsed current of frequency f _about , stabilized in amplitude. The modulated light from the source 8, passing through the lens 9, forms a parallel beam that incident on the translucent mirror 16, with half of the radiation passing through the mirror 16 and incident on the ordinary mirror 17. Parallel light beams 2 and 3 reflected from both mirrors normally fall on the surface moving test material (paper web), the vector of the speed of drawing the web is shown in Fig.6 with an arrow. On the opposite side of the tracing paper, under the beam 2 there is a flat opaque white substrate 4, and under the beam 3 there is a black substrate 5. The light scattered by the paper in the opposite direction is captured by two identical photodetectors 10 (for example, FD-256 photodiodes), which are located in a plane perpendicular to the direction paper broadening, the angle φ between the axis of the incident beam and the direction from the center of the spot of light to the center of the photodetector surface of one and the other photodetector is the same. To eliminate possible spurious illumination, the photometric parts of both measuring channels are enclosed in opaque blackened covers 14. The photo signals from both photodetectors are fed to two identical amplifiers 11, each of which includes a photocurrent converter, a narrow-band filter with a frequency f _o and a synchronous detector controlled by a modulator 15. The amplified signals are fed to an analog-to-digital converter 12, where the analog photo signals are converted to digital codes, and then to the processing unit 18. The latter works as follows.

которое заносится в запоминающее устройство 19. При желании это значение может быть выдано на индикаторное табло 13. В режиме "измерение" (т.е. при протягивании в измерительном зазоре полотна измеряемой кальки) происходит отсчет n значений сигналов I_ω и I_о, усреднение этих значений и вычисление прозрачности исследуемой кальки
χ 1-

По желанию оператора на индикаторное цифровое табло может выводиться либо χ либо δχ χ χ_э Через определенное время t происходит новое накопление отсчетов I_ω и I_o и процесс обработки повторяется.In the “standard” mode (that is, when a similar tracing paper adopted for the standard moves in the measuring gap of the sample), n values of the signals I _{ω, e} and I _{o, e} from both amplifiers are counted, then they are averaged and the transparency value of the standard is calculated χ _e = 1-

which is entered in the storage device 19. If desired, this value can be displayed on the indicator board 13. In the "measurement" mode (that is, when drawing the tracing paper of the measured tracing paper in the measuring gap), n values of the signals I _ω and I _о are counted, averaging these values and calculating the transparency of the tracing paper
χ 1-

At the request of the operator on a display digital display can be displayed either x or δχ χ χ _e after a certain time t, there is a new accumulation of samples and I _ω I _o and the process is repeated.

The measurement time of the transparency of the investigated paper is determined by the time of a sufficient averaging of the photographic signals I _ω and I _о and at the existing speeds of drawing the paper web does not exceed seconds, which is significantly less than the measurement time by the prototype method.

Claims (1)

 METHOD FOR CONTROLLING TRANSPARENCY OF PLANE LIGHT-TRANSMITTING MATERIALS, during which flat white and black substrates are placed under the test material, the test material is illuminated with the light flux normally to its surface, the light flux scattered by the test material and one of the substrates in the direction opposite to the incident light is recorded. , characterized in that the test material in the area of the second substrate is illuminated with an additional light flux directed normally to e of the surface, the light flux scattered by the test material and this substrate in the direction opposite to the incidence of light on the test material is recorded, and the transparency of the test material is judged by the magnitude of these fluxes, while the light flux is recorded in the same solid angles oriented at the same angles to each from light streams incident on the material under investigation.

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