JPS6161625B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an apparatus for measuring the amount of water contained in a sheet-like object. As a device for measuring the amount of moisture contained in a sheet-like object, there is a multiple scattering/transmission moisture meter that continuously measures the moisture contained in or adsorbed in papermaking (Japanese Patent Application No. 1983-63362). . FIG. 1 is an explanatory diagram of the structure of the moisture meter. In FIG. 1, the upper head 1 has 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 171 in a disc-shaped plate surface.
8, etc., and standard samples 19, 2 are included in some of them.
0..., 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 parallel light rays passing through the illumination window 4. On the other hand, the lower head 2 has an entrance window 6, a scattering surface 22 coated with a reflective material, a lens 11 that converges the light incident on the entrance window 6, and a sensor 12 that detects the converged incident light. The upper and lower heads 1 and 2 face 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 1.
1 and sensor 12 constitute a multiple scattering optical system, and 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 the error factors included in this signal, such as fluctuations in transmittance f (common in paper making containing waste paper in the raw material pulp).
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 r, 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 windows 4 and 5, entrance window 6
It was difficult to maintain measurement accuracy in a dusty atmosphere because the characteristics varied depending on the surface of the dust adhering to the surface, and also showed different characteristics depending on the color of the dust (white, black, gray, etc.). . Therefore, the present inventors previously invented a method and device for compensating only the amount of dust adhesion (Japanese Patent Application No. 104766/1983).
(Special Application No. 104769, 1982). According to the above invention, Mn/
The Rn signal (this is called the K value) and the amount of dust adhesion have the relationship shown in FIG. 2, and the compensation calculation formula is equation (1). 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 −Rno/Rto (2) However, Kon...K value (Mn/Rn signal) in measurement state (online) DK ₁ ...Experiment Constant F (ΔMz) determined by... Signal indicating the amount of dust adhesion Rn _d , Rt _d ... Value Rno of Rn signal and Rt signal obtained using zero sample when dust is attached to the scattering surface etc. , Rto... Values of Rn signal and Rt signal obtained using zero sample 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 amount of dust attached and the number of calibrations. show. Graph (a) is a graph obtained using the zero sample in sample holder 16, and graph (b) is obtained by placing a sheet-like object with the same physical properties as the zero sample at the position where the paper to be measured is flowed. It is a graph. 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 (a), point A is Kzo, which is the K value 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 and 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 graph (b) correspond to points A, B, C, and D in graph (a), respectively. 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) Same as in equations By the way, constant DK ₁ and 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 that passes 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 that adheres 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 this point, 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. That is, the device according to the present invention irradiates light onto an object to be measured from an irradiation window consisting of a concave lens placed close to the window surface, and directs the light that has interacted with the object multiple times close to the window surface. A multiple scattering optical system detects the light through an entrance window with a concave lens installed therein, and an irradiation window that forms a light transmission path with an opening smaller than the entrance window illuminates the object to be measured. a transmission optical system that detects the light transmitted through the object to be measured;
When there is no dust attached to the opposing surfaces of the upper and lower heads, apply the calibration signal obtained using the standard sample and periodically or as necessary, and perform the calibration signal obtained using the standard sample. and means for performing predetermined calculations using the measurement object to obtain a signal related to the physical properties of the object to be measured. 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 configuration of the apparatus shown in FIG. 6 is characterized by having a concave lens 31 installed close to the window surface, an irradiation window 4 of a multiple scattering optical system that irradiates light onto the paper 3 through this concave lens 31, and an irradiation window 4 in the optical path. A condensing lens 32 having a collar 33 is disposed, an irradiation window 5 of a transmission optical system having an aperture smaller than the aperture of the entrance window 6, and a concave lens 34 disposed close to the window surface. It has an entrance window 6 that guides incident light to the sensor 12 via a concave lens 34. 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. 8 depending on the color of the attached dust. In FIG. 8, 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 4 is as shown in FIG.
The parallel light beam 35 obtained through the lens 8 becomes scattered light projected in the 2π direction by the concave lens 31,
Ideal scattered light without dust. Therefore, if dust adheres to the window surface of the irradiation window 4, scattered light will decrease even if the dust is white.
In addition, since the concave lens 34 is installed close to the window surface of the entrance window 6, as shown in FIG.
Scattered light 36 that has been scattered through the gap between the lower heads
is easy to detect (the viewing angle from the sensor 12 is substantially expanded), and the opening of the irradiation window 5 located directly above the entrance window 6 is smaller than the opening of the entrance window 6. Therefore, the scattered light that is reflected and enters the opening of the irradiation window 5 is hardly affected by changes in the state of the opening of the irradiation window 5 (dust adhesion). For the above reason, when dust adheres to the opposing surfaces of the upper and lower heads, the Rn signal tends to decrease. In this way, the Rn signal exhibits a decreasing tendency regardless of the color of dust adhering to the scattering surface, etc., so that the compensation amounts ΔKpp and ΔMpp depend on the color of the dust, as shown in Figures 9 and 10. This is a characteristic that has a compensation coefficient that is not affected by. Figures 9 and 10
The figure shows the compensation amount Δ of the K value in the device according to the 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-black 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 to this, but 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. As explained in detail above, according to the measuring device according to the present invention, a detection signal having a certain characteristic with respect to the color of dust adhering to a scattering surface etc. is obtained, and the amount of adhering dust is calculated in a predetermined manner. 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]

Fig. 1 is an explanatory diagram of the configuration of a conventional multiple scattering/transmission moisture analyzer, Fig. 2 is a K value-dust adhesion characteristic diagram, and Figs. 3 and 4 are compensation amount and dust adhesion amount signals. 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 multiple scattering optics of the moisture meter according to the present invention. An explanatory diagram of the creation of scattered light in the system irradiation window and an explanatory diagram of the incident light in the incident window. FIG. 8 is a diagram of the Rn signal-Rt signal relationship in the moisture meter according to the present invention. FIGS. FIG. 3 is a diagram showing the relationship between the compensation amount in the meter and the dust adhesion amount signal. 1...Top head, 2...Bottom head, 3...Paper,
4 and 5...irradiation window, 6...incident window, 7...lamp, 8, 10 and 32...lens, 13...rotating sector, 16...sample holder, 31 and 34
……concave lens.

Claims (1)

[Claims] 1. An upper head and a lower head are arranged facing each other to constitute a multiple scattering type optical system and a transmission type optical system, and a sheet-like object is arranged in the gap formed by the upper and lower heads, and a sheet-like object is arranged in the gap formed by the upper and lower heads. The object is irradiated with measurement light that is light in a wavelength range that is absorbed by moisture in the object and reference light that is light in a wavelength range that is not absorbed, and the measurement light and the reference light that interact with the object. is detected by a light receiving section common to the two optical systems, and is detected by a calculation using a measurement signal and a reference signal output from the light receiving section corresponding to the measurement light and reference light, respectively. In an apparatus for measuring the amount of water in a body, the irradiating section of the multiple scattering optical system is configured such that a concave lens is installed close to the window surface to irradiate the object while diverging the incident light, and the irradiating section of the multiple scattering optical system is configured to The irradiation section of the transmissive optical system is configured to have an irradiation window with an opening smaller than the window, and when no dust is attached to the opposing surfaces of the upper and lower heads, a standard sample is used. Using the obtained calibration signal and the calibration signal obtained using the standard sample through which a calibration operation is performed periodically or as necessary, the influence of the amount of dust adhesion is removed by calculation using the measurement signal and reference signal. A device for measuring the amount of moisture in a sheet-like object, comprising means for obtaining a signal related to the amount of moisture.