JPH02284010A - Measuring device for film thickness of resin film - Google Patents

Abstract

PURPOSE:To enable measurement in a wide range and high resolution by utilizing a lens system to substantially enlarge a diffracted pattern and furthermore utilizing a plurality of photodetectors and catching the change in the diffracted pattern correspondent to the change in the thickness of a resin film as the change in light intensity. CONSTITUTION:In a light receiving part 13, a first photodetector 13a corresponds to the rising part of a diffracted pattern in such a state wherein a film 17 does not exist on a roller 16. The light photodetected by respective photodetectors 13a is given to a light intensity detector 14a, respectively. Therein light intensity is detected and output as the signal of light intensity and this signal is treated in a device 15. When the thickness of the film 17 is changed, the photodetector 13a corresponding to the rising part of the diffracted pattern is changed and the intensity of light incident on the photodetector 13a is changed. Thereby the signal of light intensity output from the detector 14a is changed. In this case, the device 15 calculates the received light quantity incident on the photodetector 13a from the signal of light intensity. The photodetector 13a corresponding to the rising part of the diffracted pattern is specified by threshold value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a measuring device for measuring the thickness of a resin film such as a plastic film.

[Prior Art] Generally, in a plastic film laminating device,
It is necessary to control the film thickness to a constant level in order to improve quality and save film raw materials.

For this purpose, it is essential to accurately detect the film thickness.

Conventionally, when detecting film thickness, there are a total of 411 devices that irradiate the film with infrared rays and detect the film thickness based on the amount of infrared rays absorbed by the film, and a total of 411 devices that irradiate the film with radiation such as beta rays or X-rays. A measurement device that detects the film thickness based on the amount of radiation absorbed by the film, and a measurement device that scans and irradiates the film and reference surface (roll surface) moving on a roll with a laser beam to detect the difference between the reference surface and the film surface. A measuring device is used that detects the film thickness based on the displacement of the film.

[Problems to be Solved by the Invention] By the way, in the case of the above-mentioned measuring device that uses infrared rays, since the amount of infrared absorption varies depending on the material of the film, it is possible to use a film whose thickness is known in advance for each film material.
The amount of infrared absorption must be calibrated, and the work for calibration is extremely troublesome. Furthermore, depending on whether the base material is transparent or opaque, an infrared transmission type or infrared reflection type measuring device must be used, respectively. That is, different measuring devices must be used depending on the type of base material.

Further, when characters or the like are printed on the base material, there is a problem that infrared rays are absorbed by the printed pigment, causing an error in the total film thickness JDJ.

In the case of the above-mentioned measuring device that uses radiation, the amount of radiation absorbed similarly varies depending on the material of the film, so the amount of radiation absorbed must be calibrated in advance using a film whose thickness is known for each film material. First, the work for calibration is extremely troublesome.

Furthermore, since radiation is used, special care must be taken in its management, and in addition, the decay of atomic nuclei is irregular, so the intensity of the radiation fluctuates.

Therefore, it is necessary to increase the film thickness measurement time and average the film thickness measurement values to improve the accuracy of the film thickness meter (Fl), but in any case, there is a problem that the accuracy of the film thickness meter 311 deteriorates. .

On the other hand, in the case of a measuring device that measures the film thickness by the above-mentioned displacement, there is a problem that the film thickness measurement accuracy decreases due to the influence of the roundness of the roll and the vibrations accompanying the rotation of the roll. That is, since the film thickness is measured intermittently while rotating the roll, there is a problem in that measurement errors occur depending on the rotational position of the roll.

An object of the present invention is to provide a measurement device that can measure film thickness with extremely high accuracy with a simple configuration.

[Means for Solving the Problems] According to the present invention, there is provided a measuring device for measuring the film thickness of a resin film moving along a roll surface, which transmits light traveling in a tangential direction of the roll surface. a light source, a light receiving unit including a plurality of light receiving elements that receive light from the light source and the light receiving elements are arranged in a radial direction of the roll, and a lens system disposed between the roll and the light receiving unit; a light intensity detection means connected to the light receiving element to detect the light intensity of each light receiving element and output a plurality of light intensity signals; and a processing means for determining the film thickness of the resin film based on the plurality of light intensity signals. A resin film thickness meter 71PI device is obtained, which is characterized by a.

[Function] In the present invention, light traveling in the tangential direction of the roll surface is emitted from the light source. This light is diffracted by the resin film on the roll and enters the lens system.

This lens system is arranged between the roll and the light receiving section so that the imaging position on the opposite side of the light receiving section is near the surface of the roll. In other words, the light receiving section is substantially arranged nearby. As a result, the slope of the diffraction pattern becomes steeper and is applied to the light receiving section.

The intensity of the light received by each light receiving element is detected by the light intensity detection means, and the processing means calculates the thickness of the resin film based on the detected light intensities. In this way, since the diffracted light is received by a plurality of light receiving elements, the measurement range is widened and high resolution can be obtained.

[Example] The present invention will be described below based on examples.

First, referring to FIG. 1, if the downward light from the light source (not shown) is blocked by the edge of the shield (shielding plate) 1, then
A bright and dark pattern is created on the screen 2. That is, the first
As shown in the figure, a pattern in which the light intensity changes occurs on the right side of the shielding object 1.

This phenomenon is generally called Fresnel diffraction, and the change in light intensity on the screen 2 can be determined analytically. When the edge of the shielding object 1 moves from side to side, this light intensity pattern moves in the direction of edge movement by the same amount of movement as the edge. In other words, the distance between the point P on the screen 2 on the extension line of the edge and the first beak Q, f
itx is proportional to the distance z between the edge and the screen 2.

That is, there is a relationship xocFr, and the amount of edge displacement and the amount of movement of the diffraction pattern match.

By the way, in a film laminating apparatus, a film extruded from an extrusion molding machine is moved in a predetermined direction along rolls. Therefore, the light irradiated from the light source in the tangential direction of the roll, that is, the light irradiated onto the roll surface, is diffracted by the roll surface and a light intensity pattern (
diffraction pattern). As mentioned above, this light intensity pattern varies with the position of the shield, i.e. with the thickness of the film moving on the roll, e.g.
When the film thickness changes from dl to d2, the light intensity pattern moves by Δk (Δ−d2−d,) in the direction of film thickness change. Therefore, by detecting the moving change in the light intensity pattern, the film thickness can be measured by -11J.
can do.

Here, with reference to FIG. 2, a film thickness measuring device according to the present invention will be explained.

The film thickness meter II-j device according to the present invention includes a light source 11;
A light receiving section 13 disposed facing the light source 11 via a lens system 12, a light intensity detecting device 14 connected to the light receiving section 13, and a processing device 1 connected to the light intensity detecting device 14.
5.

light? R11 and the light receiving section 13 are arranged with the roller 16 in between, and the light from the light source 11 travels in the tangential direction of the roller 16. As shown in FIG. 3, a lens system 1 is located between the light receiving section 13 and the roller 16 on the optical axis from the light source 11.
2 is placed.

The arrangement position of the lens system 12 is determined so that one image formation position (the position of the virtual image, that is, the position of the virtual screen 12a) by the lens system 12 is near the surface of the roller 16. As a result, the enlarged diffraction pattern is incident on the light receiving section 13.

The light receiving section 13 includes a plurality of light receiving elements 13a, and these plurality of light receiving elements 13a are connected to the roller 1 as shown in FIG.
6 (the light receiving elements 13a are arranged in the order of 1st, 2nd, . . . 1st from the bottom to the top). The light receiving section 13 described above is composed of, for example, a CCD.

The light intensity detector 14 includes a plurality of light intensity detectors 14a, and each light receiving element 13a corresponds to the corresponding light intensity detector 14.
connected to a.

Here, as shown in FIG. 4, the rising portion of the diffraction pattern corresponds to the first light-receiving element 13a, and the movement range (range of the diffraction pattern) that one light-receiving element 13a receives is x
um, the change in the thickness of the film, that is, the displacement 2 of the film thickness, is z−ix×f(P+)t,tm−
It is expressed as (1).

Here, P is the light receiving intensity of the first light receiving element 13a, f
(P,) is the amount of movement (displacement) calculated from the received light intensity Pl
shows.

In other words, as will be described later, the first term on the right side of equation (1) roughly indicates a change in film thickness, and the second term indicates a fine change in film thickness.

In the light receiving section 13, when the film 17 is not present on the roller 16, the first light receiving element 13a (the light receiving element 13a located at the lowest end) corresponds to the rising portion of the diffraction pattern. In other words, the first light receiving element 13a is the base mulberry. Therefore, when the film 17 is present on the roller 16, for example, the i-th (i≧2) light receiving element 1
3a corresponds to the rising portion of the diffraction pattern.

The light received by each light receiving element 13a is detected by a light intensity detector 14a.
The light intensity is detected here and output as a light intensity signal. These light intensity signals are then input to the processing device 15.

A predetermined threshold level is preset in the processing device 15, and this threshold level is set to a light intensity corresponding to the rising portion of the diffraction pattern.

By the way, when the thickness of the film 17 changes, the light receiving element 13a corresponding to the rising portion of the diffraction pattern changes. In other words, the intensity of light incident on each light receiving element 13a changes. This changes the light intensity signal output from each light intensity detector 14a.

Processing device] 5 processes each light receiving element 13 from these light intensity signals.
The amount of light received (light intensity) incident on a is known, and the light receiving element 13a corresponding to the rising portion of the diffraction pattern is specified using the above-mentioned threshold level.

For example, it is specified that the (i+1)th light receiving element 13a corresponds to the rising portion of the diffraction pattern. Then, the processing device 15 also uses the intensity (P+++) of the light incident on the (i+1)th light receiving element 13a to
) Find the change in film thickness using the formula. In other words, the change in film thickness (z)-(i+1)x+f (P++
+).

Here, the change in film thickness is roughly determined based on (1+1)X, that is, the position of the light receiving element 13a corresponding to the rising portion of the diffraction pattern, and further, (i+
1) Since the light intensity P4,1 of the th light-receiving element 13a changes in response to minute changes in the film angle, this P1+
A minute change f(P++t) in the film thickness is determined from 1, and an actual change (2) in the film thickness is determined. In this way, changes in film thickness are continuously measured.

[Effects of the Invention] As explained above, in the present invention, a lens system is used to substantially enlarge a diffraction pattern, and a plurality of light-receiving elements are used to change the diffraction pattern in response to changes in resin film thickness. Because it detects changes in light intensity (amount of received light), it not only ensures a wide measurement range but also high resolution. Therefore, the resin film thickness can be easily measured with extremely high accuracy.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining Fresnel diffraction, FIG. 2 is a diagram showing an embodiment of the film thickness measuring device according to the present invention,
FIG. 3 is a diagram showing essential parts of the film thickness measuring device shown in FIG. 2, and FIG. 4 is a diagram for explaining the operation of the film thickness measuring device '1p1 according to the present invention. DESCRIPTION OF SYMBOLS 11... Light source, 12... Lens system, 13... Light receiving part, 14... Light intensity detection device, 15... Processing device,
16...roller, 17...film. Moe 4 figure L-i [, i+1

Claims (1)

[Claims] 1. A measuring device for measuring the film thickness of a resin film moving along a roll surface, which includes a light source that emits light traveling in a tangential direction to the roll surface, and a light receiving element that receives light from the light source. a plurality of light receiving sections in which the light receiving elements are arranged in the radial direction of the roll; a lens system disposed between the roll and the light receiving section; and a lens system connected to the light receiving elements and configured to adjust the light intensity of each light receiving element. A resin film thickness measuring device comprising a light intensity detection means for detecting and outputting a plurality of light intensity signals, and a processing means for determining the film thickness of the resin film based on the plurality of light intensity signals. .