JPS6225984B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a device for measuring properties of sheet-like objects. As a device for measuring the properties of sheet-like objects, there is a multiple scattering/transmission moisture meter that continuously measures the moisture contained in or adsorbed in papermaking (Japanese Patent Application No. 63362/1982). FIG. 1 is an explanatory diagram of the structure of the moisture meter. In FIG. 1, the detection head 1 includes irradiation windows 4 and 5.
, a scattering surface 21 coated with a reflective material, and two through holes are provided in the disk-shaped plate surface, with a reference light filter 14 in one hole and a measurement light filter 15 in the other hole.
A rotary sector 13 that is embedded and supported and rotates continuously at a constant speed, and a plurality of through holes 17 in a disc-shaped plate surface.
18... etc., and standard sample 1 is included in some of them.
9, 20, etc., and rotates at a predetermined angle periodically or as needed by a control signal given from the outside. It has a lamp 7, a lens 8, a mirror 9 and a lens 10 for creating a light beam and a parallel light beam passing through the illumination window 5. On the other hand, the lower head 2 has an entrance window 6 and a scattering surface 2 covered with a reflective material.
2, and a lens 1 that converges the light incident on the entrance window 6.
1 and a sensor 12 that detects the converged incident light. The upper and lower heads 1 and 2 are opposed to each other with a sheet of paper 3 in between, and include a lamp 7, a lens 8, an irradiation window 4, scattering surfaces 21 and 22, an entrance window 6, and a lens 11.
The sensor 12 constitutes a multiple scattering optical system, and the lamp 7, mirror 9, lens 10, irradiation window 5, entrance window 6, lens 11, and sensor 12 constitute a transmission optical system. In normal measurement conditions, the through hole 17 is placed above the irradiation window 4 and the through hole 1 is placed above the irradiation window 4.
8 are positioned above the irradiation window 5, and the paper 3 is irradiated with intermittent light from the rotating sector 13 from the irradiation windows 4 and 5, and the light that interacts with the paper 3, that is, the measurement in the multiple scattering optical system. A time series signal consisting of light Mn, reference light Rn, measurement light Mt and reference light Rt in the transmission optical system is detected by the sensor 12, and sent to the next stage calculation/control unit (not shown) to perform predetermined calculations. It is now possible to measure the moisture content of paper. In addition, in the calibration state, the sample holder 16 is rotated intermittently with no paper 3 between the upper and lower heads 1 and 2, and a standard sample, that is, a zero sample, is placed above the irradiation windows 4 and 5. Samples, span samples, check samples, etc. are arranged in sequence, and signals corresponding to measurement lights Mn and Mt and reference lights Rn and Rt from each sample are obtained. In such a moisture meter, the signal used for actual calculation in the calculation/control section is the Mn signal (signal corresponding to measurement light Mn) as a moisture signal.Hereinafter, the signals corresponding to each light are called Rn signal, Mt signal, Rt signal. (called a signal)
The ratio of the Mn and Rn signals, that is, the Mn/Rn signal, is used to calculate error factors included in this signal, such as fluctuations in transmittance f (which is common in papermaking where raw material pulp contains waste paper).
Compensation calculations are performed using the Rn/Rt signals. The reason why the Mn/Rn signal and Rn/Rt signal are used in calculations is to cancel characteristic fluctuations of the lamps, sensors, etc. that make up the optical system, and to cancel changes in the characteristics of the lamps, sensors, etc. that make up the optical system, and to
Variables that affect each signal of Mt and the optical properties of paper,
That is, the number of layers n, transmittance f, reflectance γ, and water content.
MW, exhibits the sensitivity characteristics shown in the table below,
This is because the sensitivity of the Mn/Rn signal increases with respect to the water content, and the sensitivity of the Rn/Rt signal increases with respect to the transmittance f.

[Table] By the way, it is ideal that the Mn/Rn signal and the Rn/Rt signal are not affected by factors other than desired factors, but in reality, each signal of Rn, Mn, Rt, and Mt is affected by the scattering surface 21. 22, irradiation window 4 and 5, entrance window 6
It varies depending on the amount of dust attached to the surface, etc., and the color of the dust (white, black, gray, etc.)
It has been difficult to maintain measurement accuracy in a dusty atmosphere because the characteristics vary depending on the type of material. Therefore,
Previously, the present inventors invented a method and device for compensating only the amount of dust adhesion (Japanese Patent Application No. 104766/1986).
(Special Application No. 104769, No. 104769). According to the above invention,
The Mn/Rn signal (this is called the K value) and the amount of dust adhesion have the relationship shown in Figure 2, and the compensation calculation formula is (1)
The formula becomes In addition, in equation (1), the amount of compensation is DK ₁・F
(ΔMz). K=Kon−DK ₁・F(ΔMz) (1) ΔMz=Rn _d /Rt _d −Rn _p /Rt _p (2) However, Kon...K value (Mn/Rn signal) in measurement state (online) DK ₁ ...Constant F (ΔMz) determined by experiment...Signal indicating the amount of dust adhesion
Rn _d , Rt _d ...When dust is attached to the scattering surface, the Rn signal obtained using zero sample and
Rt signal values Rn _p , Rt _p ...Rn signal and Rt signal values obtained using zero samples when no dust is attached to the scattering surface, etc. In Figure 2, the vertical axis is the K value, and the horizontal axis is the K value. Shows the amount of dust attached and the number of calibrations. Graphi is a graph obtained by using the zero sample in the sample holder 16, and Graphi is a graph obtained by disposing a sheet-like object having the same physical properties as the zero sample at the position where the paper, which is the object to be measured, flows. In addition, at the site where the detection head is actually installed, the amount of attached dust increases proportionally with time, so when calibration is performed at regular intervals, the amount of attached dust corresponds to the number of times of calibration, so the amount of attached dust is Proportional to the number of calibrations. In the graph, point A has a K value of Kz _p when no dust is attached to the scattering surfaces of the upper and lower heads, each window, etc. Point B is a plot of the value after the calibration after a certain period of time (this is called the first calibration), and the amount of dust adhesion d=
d ₁ , K value=Kz ₁ . Similarly, point C is
Due to the second calibration, dust adhesion amount d=
d ₂ , K value = Kz ₂ , D point is due to the third calibration, dust adhesion amount d = d ₃ , K value = Kz ₃
It is. On the other hand, points A, B', C', and D' in the grapho correspond to points A, B, C, and D in the graphi. The reason why the K value differs depending on the position where the sample is placed is that when a sheet-like sample is placed at the position where the paper is actually flowed, the degree of multiple scattering is due to the sample in the sample holder. This is thought to be because it is extremely large in comparison. Similarly, the Rn/Rt signal (referred to as the M value) also exhibits the same characteristics as shown in FIG. 2, and the compensation calculation formula for the M value is equation (3). M=Mon−DK ₂・F(ΔMz) (3) However, Mon...M value (Rn/Rt signal) in measurement state (online) DK ₂ ...Constant F(ΔMz) found by experiment...(1 ), constants DK ₁ and DK in equations (1) and (3)
DK ₂ can be considered a constant in places where the dust color is constant, but when the dust color changes, DK ₁ and DK ₂
It also changes. Moreover, the site where the detection head is installed often has an atmosphere containing a mixture of paper dust (white), paper dust + carbon (gray), carbon (black), etc. (1)
It is difficult to completely compensate for the influence of dust using equations and equations (3). Figures 3 and 4 show the compensation amount DK ₁・F (ΔMz)≡ΔKpp and DK ₂・F (ΔMz) in equations (1) and (3).
FIG. 2 is a characteristic diagram of Mz)≡ΔMpp. The suffix 1 attached to the graph in each figure indicates the characteristics when white dust (paper powder) adheres to the scattering surface or the like. Similarly, subscript 2
is a characteristic when gray-white dust (paper powder + a small amount of carbon) is attached, subscript 3 is a gray-black dust (paper powder + a large amount of carbon), and subscript 4 is a characteristic when black dust (carbon) is attached. The meanings of these subscripts are the same in FIG. 5, which will be described later. FIG. 5 shows the relationship between the Rn signal and the Rt signal using zero samples in the detection head of FIG. 1. As is clear from Figure 5, the Rn signal shows an increasing characteristic when white dust is attached, whereas it shows a decreasing characteristic when black or near-black dust is attached. . on the other hand,
The Rt signal has a decreasing characteristic regardless of the color of the dust. The above phenomenon occurs because the light transmitted through the irradiation window 4 becomes scattered light due to the presence of white dust, and the light that has been multiple scattered in the gap formed by the upper and lower heads is scattered by the white dust adhering to the irradiation window 5. Therefore, it is considered that this occurs because more light is incident on the entrance window 6. The present invention has been made in view of these points, and is aimed at obtaining accurate measurement signals regardless of the amount and properties of dust adhering to the scattering surface (opposing surface), irradiation window, entrance window, etc. It is an object of the present invention to provide a device that obtains a detection signal having constant characteristics for each color and compensates for the influence of the amount of attached dust by calculation. The structure of the present invention is such that an upper head and a lower head are disposed facing each other to constitute an irradiating section and a light receiving section.
A sheet-like object is disposed in the gap formed by the lower head, and the light from the irradiation section is irradiated onto the object through the irradiation window, so that the light interacts with the object multiple times,
A multiple scattering optical system detects the object through an entrance window, and irradiates the object with light from an irradiation window that sandwiches the object and faces almost directly to the entrance window, and transmits light through the object through the entrance window. A transmission optical system for detecting light is provided, and each optical system detects a measurement light signal and a reference light signal, and uses these signals to obtain a signal corresponding to the characteristics of the object, and to detect the characteristics of the upper and lower heads. In an apparatus that performs a calibration operation by irradiating light from the irradiation section onto a standard sample provided inside the - head when the object is not present in between, the two irradiation windows and the entrance window are made of a scattering material. using the calibration signal obtained by the calibration operation with no dust attached to the opposing surfaces of the upper and lower heads, and the calibration signal obtained by the calibration operation applied periodically or as necessary. The purpose is to compensate for errors caused by dust adhesion. The present invention will be explained in detail below. FIG. 6 is an explanatory diagram of the configuration of a measuring device according to an embodiment of the present invention. Number 1 is the number given in Figure 6.
Components that are the same as those in the drawings have the same meaning, so their explanations will be omitted here. The features of the device in FIG. 6 include scattering materials 31, 32 and 33 such as opal glass and milky glass
is used to construct the irradiation window 4 of the multiple scattering optical system, the irradiation window 5 of the transmission optical system, and the entrance window 6 of both optical systems. Furthermore, in Japanese Patent Application Laid-Open No. 49-66194 (Apparatus for Measuring Characteristics of Thin Materials), a structure is shown in which the apertures of the radiation source and detector are covered with a diffusing material. A diffusing material is used in order to be able to measure the moisture content with high sensitivity even with light paper.On the other hand, in the present invention, when dust adheres to the opposing surfaces of the upper and lower heads, it is possible to measure the moisture content with high sensitivity. A scattering material is used to prevent the detection light from being affected differently, and the purposes and effects of using the scattering material are different between this known example and the present invention.Furthermore, in the present invention, the irradiation windows 4 and 5 and the entrance window 6
In addition to being made of scattering material, the calibration signal obtained by the calibration operation with no dust attached to the window surfaces and scattering surfaces of the upper and lower heads 1 and 2, and the calibration after dust has adhered. The configuration is characterized in that dust compensation is performed using a calibration signal obtained through operation. In the above configuration, the rotating sector 13 and sample holder 16 perform the same operations as in FIG. 1, and the sensor 12 detects time-series signals of Rn, Mn, Rt, and Mt and sends them to the calculation/control unit . The relationship between the Rn signal and the Rt signal at this time changes as shown in FIG. 7 depending on the color of the attached dust. In FIG. 7, the vertical axis is the rate of change of the Rn signal with respect to the Rn signal when the amount of dust adhesion is zero, and the horizontal axis is the rate of change of the Rt signal in the same situation.
Graphs C ₁ , C ₂ , C ₃ and C ₄ are graphs obtained by depositing the above-described white dust, gray-white dust, gray-black dust, and black dust on each window surface, scattering surface, etc. As shown in the figure, the Rn signal is at its maximum when no dust is attached to the window surface, scattering surface, etc., and when dust is attached, it shows a decreasing tendency regardless of its color. That is, unlike the characteristics shown in FIG. 5, when dust adheres to the opposing surfaces of the upper and lower heads, the Rn signal always decreases. This phenomenon can be considered as follows. The light from the irradiation window is a parallel light beam obtained through the lens 8, and becomes scattered light that is projected in the 2π direction by the scattering material 31, and becomes ideal scattered light in the absence of dust. In addition, when the scattered light that has been scattered through the gap between the upper and lower heads is repeatedly scattered between the irradiation window 5 and the entrance window 6 and enters the window, each window surface is
and 33, the ideal scattering surface is when no dust is attached. For this reason,
When dust adheres to the window surfaces of the irradiation windows 4 and 5 and the entrance window 6, scattered light decreases even if the dust is white. For the above reason, when dust adheres to the opposing surfaces of the upper and lower heads, the Rn signal tends to decrease. As shown in Figures 8 and 9, the Rn signal tends to decrease regardless of the color of the dust adhering to the scattering surface, etc., so that the compensation amounts ΔKpp and ΔMpp change depending on the color of the dust, as shown in Figures 8 and 9. The characteristic has a compensation coefficient that is not affected by . FIGS. 8 and 9 show the compensation amount Δ of the K value in the device according to the present invention.
It shows the relationship between the compensation amount ΔMpp of Kpp and M value and the dust adhesion amount signal ΔMz, and the data
The mark indicates white dust, the mark ○ indicates gray-white dust, the mark △ indicates gray dust, and the mark □ indicates black dust. Although the above embodiments have been described with respect to a moisture meter for papermaking, the present invention is not limited thereto, and includes devices for measuring physical quantities of sheet-like objects, such as a device for measuring film thickness. Furthermore, in the above embodiment, the Mn/Rn signal and the Rn/
Although predetermined calculations are performed using the Rt signal, the present invention is not limited to this, and may be an apparatus that performs calculations using other signals. Furthermore, the opening of each window is
The same effects as in the above-mentioned embodiment can be obtained even if the structure is made up of members constituting the above-mentioned embodiment. As explained in detail above, the measuring device according to the present invention obtains a detection signal having a certain characteristic for the color of dust adhering to a scattering surface, etc., and calculates the amount of adhering dust by a predetermined calculation. Since the compensation is performed, highly accurate measurement signals can be obtained regardless of the amount and properties of dust adhering to the scattering surface, etc.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the configuration of a conventional multiple scattering/transmission moisture analyzer, Figure 2 is a K value-dust adhesion characteristic diagram, and Figures 3 and 4 are diagrams showing the compensation amount and dust adhesion amount signal. 5 is a diagram showing the relationship between the Rn signal and the Rt signal, FIG. 6 is an explanatory diagram of the configuration of a moisture meter according to an embodiment of the present invention, and FIG. 7 is a diagram showing the Rn signal in the moisture meter according to the present invention. Rt signal relationship diagram, Figures 8 and 9
The figure is a diagram showing the relationship between the compensation amount and the dust adhesion amount signal in the moisture meter according to the present invention. 1... Upper head, 2... Lower head, 3... Paper, 4 and 5... Irradiation window, 6... Entrance window, 7... Lamp, 8, 10
and 11...lens, 13...rotating sector, 16...sample holder, 21 and 22...scattering surface, 31,3
2 and 33...Scattering material (opening).

Claims (1)

[Claims] 1. An upper head and a lower head are disposed facing each other to constitute an irradiation section and a light receiving section, and a sheet-like object is disposed in the gap formed by the upper and lower heads, and the light from the irradiation section is directed through the irradiation window. a multiple scattering optical system that irradiates the object from the object and detects the light that interacts with the object multiple times through an entrance window; and an irradiation window that sandwiches the object and faces almost directly to the entrance window. A transmission optical system is provided to irradiate the object with light and detect the light transmitted through the object through the entrance window, and each optical system detects a measurement light signal and a reference light signal, and these signals are detected by each optical system. to obtain a signal corresponding to the characteristics of the object, and when the object is not present between the upper and lower heads, the light from the irradiation section is irradiated to a standard sample provided inside the - head. In an apparatus that performs a calibration operation, the two irradiation windows and the entrance window are made of a scattering material, and a calibration signal obtained by a calibration operation with no dust attached to the opposing surfaces of the upper and lower heads; 1. A characteristic measuring device for a sheet-like object, characterized in that errors due to dust adhesion are compensated for using a calibration signal obtained through a calibration operation performed periodically or as needed.