JPH01291104A - Film thickness measuring instrument for resin film - Google Patents

Abstract

PURPOSE:To simplify the constitution and to measure the thickness of a film with high accuracy by comparing a reference light intensity pattern which has been determined in advance with a light intensity pattern contained in a state that a resin film exists on a roll. CONSTITUTION:A light beam from a light source 6 travels in the tangential direction, and a photodetector 7 using, for instance, a linear sensor outputs the light beam which has been brought to Fresnel diffraction by the roll 3, as a light intensity pattern. In a processor 8, a reference light intensity pattern in a state that no film exists on the roll 3 is stored in advance. In this state, the detector 7 which has received the light beam from the light source 6 in a state that a film 4 exists on the roller 3 outputs the light intensity pattern being different from the reference light intensity pattern, and compares both the patterns. In such a way, when the film thickness of the film 4 for moving on the roll 3 is shifted from prescribed film thickness, the light intensity pattern outputted from the detector 7 is shifted from the reference light intensity pattern in accordance with the variation quantity of the film thickness, and by comparing both the patterns, the variation quantity of the film thickness is derived.

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 glass 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, a measuring device that irradiates the film with infrared rays and detects the film thickness based on the amount of infrared rays absorbed by the film, beta rays or
A measurement device that irradiates the film with radiation such as a line and detects the film thickness based on the amount of radiation absorbed by the film, and a measurement device that irradiates the film and reference surface (roll surface) moving on a roll and scans it while irradiating it with laser light. A measuring device is used that detects the film thickness based on the displacement between the reference surface and the film surface.

[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 measuring the film thickness.

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

In addition, since radiation is used, special care must be taken in its management.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 film thickness measurement accuracy, but in either case, there is a problem that the film thickness measurement accuracy 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 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 measuring 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 that receives light from the light source and outputs a light pattern; a reference light pattern when a resin film of a predetermined thickness is present on the roll is stored; Processing means for determining whether the thickness of the resin film is the predetermined thickness by comparing the pattern with a second light pattern output from the light detection means in a state where the resin film is present on the roll. There is obtained a film thickness measuring device for a resin film characterized by having the following.

It is preferable that the above measuring device is provided with a position detecting means for detecting the position of the roll.

[Function] In the present invention, light traveling in the tangential direction of the roll surface is transmitted from the light source, the light from the light source is received by the light detection means in a state where the resin film is present on the roll, and the second light is transmitted from the light detection means. A light pattern is output. The processing means stores a reference light pattern (first light pattern) when a resin film of a predetermined thickness is present on the roll, and the processing means compares this reference light pattern with a second light pattern. Based on this comparison result, it is determined whether the thickness of the resin film is within a predetermined thickness. At this time, the position of the roll is detected by the position detection means,
It is preferable to correct the thickness of the resin film.

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

First, referring to FIG. 1, when plane light from a light source (not shown) is blocked by the edge of a shielding object (shielding plate) 1,
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.

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, as shown in Figure 2, the light source (
(not shown) to roll 3. As mentioned above, this light intensity pattern varies depending on the position of the shielding object, that is, it varies depending on the thickness of the film 4 moving on the roll 3. For example, when the thickness of the film 4 changes from dl to d2, The light intensity pattern moves by Δk (Δ=d2 d+) in the direction of change in the thickness of the film 4. Therefore, the film thickness can be measured by detecting the movement change of the light intensity pattern.

When plane light is used as shown in Figure 2, the change Δ in the light intensity pattern and the change d2-d in the film thickness are exactly the same, that is, in general, the change in the film thickness is extremely small. Therefore, the amount of change in the light intensity pattern is extremely small, and the detection accuracy of the amount of change in the light intensity pattern is not very good.In other words, the detection accuracy of the amount of change in the light intensity pattern and the detection accuracy of the film thickness are not the same. In order to improve the accuracy of detecting the amount of change in the light intensity pattern, divergent light from a point light source is used instead of plane light. Note that Fresnel diffraction also occurs in the case of diverging light.

Referring to FIG. 3, change in film thickness is calculated by Δd−(d
2 d+), the amount of change Δ in the light intensity pattern at this time is expressed by the following equation.

Δ=Δd·I (k1+kz)/+1 where 1 indicates the distance from the point light source to the contact point of the roll 3, and k2 indicates the distance from the contact point of the roll 3 to the screen 2.

Therefore, for example, if kz=3 is +, Δ=4Δd
Therefore, the amount of change in the light intensity pattern can be expanded to four times the film thickness, and as a result, the detection accuracy of the film thickness is improved.

Here, with reference to FIG. 4, the film thickness measuring device according to the present invention includes a light source 6, a photodetector 7 disposed facing the light source 6, and a processing device connected to the photodetector 7. 8
It is equipped with

The light source 6 and the photodetector 7 are arranged with a roller (not shown) in between, and the light from the light source 6 travels in the tangential direction of the roller. As the photodetector 7, for example, a linear sensor (
Alternatively, a two-dimensional COD camera) is used to receive the Fresnel diffracted light by a roller and output a light intensity pattern.

The processing device 8 stores in advance a reference light intensity pattern (first light intensity pattern) in a state where no film is present on the roller. The photodetector 7, which receives the light from the light source 6 while the film is on the roller, outputs a light intensity pattern (second light intensity pattern) different from the reference light intensity pattern. The processing device 8 that receives this second light intensity pattern compares the reference light intensity pattern with the second light intensity pattern. When the thickness of the film moving on the roll deviates from the predetermined thickness, the second light intensity pattern output from the photodetector 7 changes to the reference light intensity pattern in accordance with the amount of change in the film thickness, as described above. deviate from Therefore, by comparing the reference light intensity pattern and the second light intensity pattern, the amount of change in film thickness can be determined, and thereby the film thickness can be maintained at a predetermined thickness.

To explain in more detail, in the processing device 8, the second light intensity pattern (1(x, y
) l is the predetermined transmittance distribution ('I'(x,y))
A process of passing the signal through a filter (not shown) is performed, and a process of converging in a predetermined direction (incoming direction) is then performed. As a result, the correlation value C(y) is obtained from the following equation, and this correlation value C(y)
Find the displacement of the film thickness from the position of the maximum value.

C (y) = / I (x, y) ・T (x, y) dx
By the way, the rotating shaft of the roll may be displaced or the roll itself may vibrate due to the drive of the roll. In order to prevent errors caused by this displacement and vibration, a light source 9 and a photodetector 10 are separately arranged as shown in FIG. Then, this photodetector 10 is connected to the processing device 8. When the roll center (rotation axis) is displaced by Δr in the X direction due to vibration of the roll, the amount of change from the reference light intensity pattern of the light intensity pattern output from the photodetectors 7 and 10, respectively, is set to Δ and Δ, Then, this Δ is 5 and Δk.

Since they are equal, by subtracting them in the processing device 8, it is possible to eliminate the influence of roll vibration in the X direction. On the other hand, regarding the vibration of the roll in the Y direction,
However, by selecting preset values of 2 and 2 for the amplitude of the vibration, it is possible to keep the influence of the vibration of the roll in the Y direction within the measurement accuracy. I can do it.

Regarding roll deviation, the diameter of the roll relative to the rotation angle of the roll is measured in advance, and this measured value is sent to the processing device 8.
If it is stored in the position, the roll deviation can be corrected.

[Effects of the Invention] As explained above, in the present invention, a light intensity pattern obtained by Fresnel diffraction of light is used to obtain a predetermined reference light intensity pattern and a light intensity pattern obtained when a resin film is present on the roll. Since the thickness of the resin film is measured by comparing the values, the thickness of the resin film can be measured with extremely high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the present invention in detail, FIG. 2 is a diagram for explaining an example of measuring the thickness of a resin film according to the present invention, and FIG. 3 is a diagram for explaining the thickness of a resin film according to the present invention. FIG. 4 is a diagram showing an embodiment of the resin film thickness measuring device according to the present invention, and FIG. 5 is a diagram illustrating another example of the resin film thickness measuring device according to the present invention. It is a figure which shows another Example. 6.9... Light source, 7.10... Photodetector, 8...
Processing equipment.

Claims (1)

[Claims] 1. A measuring device for measuring the film thickness of a resin film moving along a roll surface, comprising: a light source that emits light traveling in a tangential direction of the roll surface; receive the light of
and a light detection means for outputting a light pattern,
A reference light pattern when a resin film of a predetermined thickness is present on the roll is stored, and a second light is output from the photodetector when the resin film is present on the roll and the reference light pattern. 1. A resin film thickness measuring device, comprising processing means for determining whether the thickness of the resin film is the predetermined thickness by comparing the thickness of the resin film with a pattern. 2. The resin film thickness measuring device as set forth in claim 1, further comprising a position detection means for detecting the position of the roll.