JP3104161B2 - Multi-layer sheet thickness measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved apparatus for measuring the thickness of a multi-layer sheet plastic, and more particularly, to a method for measuring the thickness of each layer of a multi-layer sheet plastic discontinuously or continuously (in-line). To provide an effective device for measurement.

[0002]

2. Description of the Related Art Today, many synthetic sheets are formed by laminating various sheets having different functions in multiple layers in order to enhance their functions. In such a multilayer laminated sheet, various functions of the sheet, such as the adhesive strength between the layers, gas barrier properties and gas selective permeability, largely depend on the state of formation of each layer. For this reason, when manufacturing such a multilayer sheet, it is necessary to know not only the strength and the overall thickness of the sheet but also the thickness of each layer individually and to perform appropriate quality control.

[0003] In general, as a device for measuring the thickness of each layer of a multilayer sheet, there are known a thickness measuring device utilizing interference by an incoherent light source and a thickness measuring device utilizing infrared absorption.

Here, in a thickness measuring apparatus utilizing interference by an incoherent light source, an incoherent light source is used, and light from the light source is firstly split by a beam splitter.
Means for splitting the amplitude into the second split light and the second split light, combining the measurement light and the reference light again to generate interference light, and allowing the split first split light to enter the multilayer film as the measurement light,
Measuring light means for measuring reflected light, reference light means for making the second branched light incident on a mirror as reference light and reflecting the same, and detecting the position of the mirror when the interference light is generated, thereby forming a multilayer. It can be seen that the film is constituted by a thickness detecting means for detecting the thickness of each layer of the film.

[0005] On the other hand, a thickness measuring device utilizing infrared absorption utilizes Lambertbeer's law.
By utilizing the difference in the absorption wavelength band with respect to the reference amplitude or their combined amplitude in the infrared absorption region ranging from 0.8 μm to several tens of μm, infrared rays in the absorption wavelength band of a specific resin are transmitted through the multilayer sheet and absorbed by the specific resin. This is an apparatus that applies the fact that the amount of infrared rays in the absorption wavelength band to be applied is in a relationship proportional to the thickness of the specific resin. The apparatus can also measure the thickness of each layer of the running multilayer sheet.

[0006]

By the way, the thickness measuring apparatus utilizing the interference by the incoherent light source has the following drawbacks and is not in a sufficiently satisfactory state. One is that an incoherent light source with a very wide wavelength range is used, so that the measurement light causes a refractive index dispersion in the multilayer sheet according to the wavelength, and the dispersion increases as the thickness of the multilayer sheet increases. In a multilayer sheet having a large thickness, interference with reference light becomes unclear due to dispersion of measurement light, and the thickness of each layer may not be measured accurately. And, especially when continuously measuring the thickness of each layer of the running multi-layer sheet, the multi-layer sheet is running with respect to the measuring device, so that it is vibrated or tilted,
No matter how much the mirror is reciprocated, the measurement light cannot interfere with the reference light within the coherence length of the incoherent light source. Even if interference occurs, the signal due to the interference light will be small, and the unevenness of the surface of the running multilayer sheet will cause a mixture of the scattered light noise generated by scattering of the measurement light and the signal due to the interference light. Therefore, it is extremely difficult to detect a signal due to the interference light. Therefore, it is extremely difficult to measure the thickness of each layer of the running multilayer sheet. The measurement apparatus is suitable for measurement in a state in which a thin multilayer sheet is stationary and fixed in a laboratory or the like in a batch (off-line) manner, but cannot be applied to an inline method.

[0007] The apparatus utilizing infrared absorption can measure the thickness of each layer as described above, but has the drawback that the thickness of each layer cannot be measured in the following cases. . It is generally and widely used. For example, in the case of a five-layer sheet, first, it is often the case that three kinds of resin components are used to laminate five layers, and the structure is shown in FIG. That is, the first layer 32 and the fifth layer 36 are the same and another second resin component is used as the central layer (the third layer 34) as one resin component, and the second layer 33 and the fourth layer 35 are the same as the other resin components. And five layers as the third resin component. In such a case, when each layer thickness is measured by the apparatus, the result is that only three layers are measured. That is, (first layer 32 + fifth layer 3
6), (central layer 34), and (second layer 33 + fourth layer 35) three layer thickness measurement. After all, in the measuring device,
Even if they are alternately laminated, if the same resin component is present in that layer, they are all summed and measured as one layer thickness, so it is not possible to measure the thickness of each layer individually. Can not.

The present invention has been made in view of the above-mentioned disadvantages of the prior art, and its main object is to provide a multilayer sheet-like plastic.
From thinner films to thicker laminates,
It is an object of the present invention to provide a multi-layer sheet-like plastic thickness measuring device capable of measuring the thickness of each layer individually and continuously (inline) with high accuracy and instantaneously.

[0009]

That is, the above object can be easily achieved by the following means. First, according to the first aspect of the present invention, a light source and light from the light source are amplitude-divided into first and second branch lights by a beam splitter, and are combined as measurement light and reference light again to generate interference light. Light generating means (A) for inputting the divided first branched light as measuring light into a multi-layer sheet-like plastic (hereinafter referred to as a multi-layer sheet) and reflecting the same. Reference light means (C) for causing the split second branched light to enter a mirror as reference light and to reflect the same.
And a thickness detecting means (D) for detecting the thickness of the multilayer sheet by detecting the position of the mirror when the interference light is generated. the, especially both with low coherent light source, the measurement light unit (B), like the multilayer sheet
Compressed air to suppress vibration and tilt of plastic
Contactless suppression means according to (E) is characterized that you are additionally provided.

The invention according to a second aspect is characterized in that the light source has a center wavelength and a spectral half width such that the coherence length of the light source is 10 μm to 40 μm.

[0011] The invention described in claim 3 is the first invention.
And the thickness detecting device (D) according to claim 2 , wherein the thickness detecting means (D) attenuates noise caused by the scattered light from the multilayer sheet surface caused by the measuring light means (B). However, it is characterized in that a signal caused by the interference caused by the interference light generating means (A) is provided with a band-pass filter (F) for preventing attenuation. Scattering of the measurement light may occur when the surface of the running multilayer sheet has fine irregularities, but this is effective as a measure to eliminate the influence on the layer thickness measurement accuracy.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Each of the above inventions will be described below in detail. The multilayer sheet-like plastic to be measured (hereinafter, multilayer sheet) is a sheet-like laminate of two or more layers composed of the same or different resin components.
There is no limitation as it is appropriately determined within a range called a sheet shape. The sheet shape is generally referred to as a sheet shape from a thin film-like laminate to a thicker laminate, but it is approximately 20 μm to 2 mm when numerically exemplified. The number of layers is generally up to about 10 layers. Further, the resin component to be laminated and the lamination structure are not particularly limited,
Unless the same resin component is subsequently laminated, for example, 2
The thickness of each layer can be instantaneously measured for any number of layers as long as the layers are alternately laminated using various kinds of resin components.

The resin component to be laminated is a generally known thermoplastic resin, but it may be a thermosetting resin. Therefore, the composite sheet may be a composite multilayer sheet in which each sheet of both components is composited. In addition, since the present invention is based on the transmission and reflection of light having a specific wavelength, it is not possible to measure an opaque material that does not transmit the light at all, but it can be measured even if the light cannot be seen at all with the naked eye. In some cases. In other words, since low coherent light emitted from the low coherent light source according to the present invention can be measured when transmitted through the multilayer sheet, transparency is not particularly limited.

In general, an apparatus for measuring a multilayer sheet using an incoherent light source includes an incoherent light source such as a halogen lamp, the above-described interference light generating means (A), measuring light means (B), and reference light means (C). ) And thickness detecting means (D) for each layer.

In the present invention, a low coherent light source is used as the light source instead of using an incoherent light source found in a conventional halogen lamp or the like. In other words, by using the light source, the measuring light reflected on the plastic surface has low coherence regardless of the thickness of the running multi-layer sheet regardless of its thickness, even in a wide range, and even if there is some vibration or inclination. Since it can interfere with the reference light within the range of the coherence length of the light source, the thickness of each layer can be measured accurately.

Here, the low coherent light source means a light source that emits low coherent light. More specifically, the light source has a narrower spectral width than an incoherent light source such as a halogen lamp and a light source such as a coherent light source such as a semiconductor laser. This means that the light source has a light output and directivity. Light sources having such properties include superluminescent diodes (hereinafter referred to as SLDs), edge-reflection light-emitting diodes, and the like. Among these, a light source having a center wavelength and a spectral half width so that the coherence length is 10 μm to 40 μm is preferable.

In addition, since the low coherent light source emits low coherent light having a narrower spectral width than the incoherent light source, the measuring light itself hardly disperses in the multilayer sheet, and therefore, even if it becomes a thicker laminate. In addition, since the interference with the reference light does not become unclear due to the dispersion of the measurement light, the thickness of each layer can be accurately measured.

[0018] If the particular vibration Toka inclination of the multilayer sheet in the traveling appears large, because there is a risk to bring an influence on the measurement accuracy, eliminates this risk, in order to measure in a more stable state, the billing Item 1 Measurement light means
Along with (B), non-contact suppression means (E) by compressed air is added.
It was done . This is intended to suppress the occurrence of vibration or tilt by injecting compressed air at least to the multilayer sheet surface at the incident position of the first branch light, and various means are conceivable. However, among them, the following means are preferably used.

It is a nozzle for ejecting compressed air having a circumferential direction, a plane for guiding the compressed air ejected from the nozzle between the nozzle and the multilayer sheet, and an air for maintaining a constant air flow rate by the compressed air ejected from the nozzle. A pneumatic non-contact suppressing device including a reservoir and an air inlet for supplying compressed air to the air reservoir. According to the suppressor, when the compressed air ejected from the nozzle passes through the gap between the multilayer sheet and the plane, the multilayer sheet is sucked into the plane by the negative pressure effect of the Bernoulli effect of the fluid, and the gap between the multilayer sheet and the plane Since the air cushion effect of air prevents the contact between the multilayer sheet and the plane, the multilayer sheet can be gripped at a substantially constant distance from the plane in a non-contact manner. In contrast, vibration or tilting can be suppressed, and it becomes easier for the measurement light reflected on the multilayer sheet to interfere with the reference light, and the thickness of each layer of the multilayer sheet is measured. be able to.

According to the third aspect of the present invention, since the band-pass filter (F) is added to the thickness detecting means (D), the band-pass filter (F) is effective not only for a stationary multilayer sheet but also for a traveling multilayer sheet. Measures. That is, the frequency of the noise due to the scattered light is determined by the traveling speed in the manufacturing process of the multilayer sheet, while the frequency of the signal due to the interference light is determined by the speed at which the mirror is reciprocated. If the speed of the reciprocating operation of the mirror is adjusted so that the frequency of the signal due to the light is sufficiently large or small, the noise due to the scattered light can be reduced by the band-pass filter (F).
On the other hand, since the signal due to the interference light is not attenuated by the bandpass filter (F), the signal due to the interference light becomes sufficiently larger than the noise due to the scattered light, and the signal due to the interference light can be detected. It is further advantageous to measure the thickness of each layer of the multilayer sheet.

Further, according to the third aspect of the present invention,
Since the non-contact suppressing means (E) and the band-pass filter (F) are provided at the same time, the above-described operations are simultaneously performed, and the moving multi-layer sheet as well as the stationary multi-layer sheet is used. Since the thickness of each layer can be stably measured with higher accuracy, a more stable multilayer sheet thickness measuring device can be obtained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings, but the present invention is not limited to the embodiments.

In the apparatus for measuring a thickness of a multilayer sheet,
The principle of measurement by the low coherent light source of the present invention will be described with reference to the optical path diagram of FIG. As the light source, a low coherent light source 2 is used.
The light is collimated by the condenser lens to become parallel light, and is amplitude-divided into two parallel lights by the beam splitter 4. The split first branched light passes through the first focusing lens and is guided to the multilayer sheet 7. At that time, reflection occurs at the interface between the layers, which is reflected as measurement light 8. The other split second branched light is incident on the movable mirror surface 11 and reflected by the second focus lens. This becomes the reference light 12. The reflected measurement light 8 and reference light 12 return to the beam splitter 4 again, become combined light 13, and are guided to the light receiving element 15 through the light receiving lens, where they are photoelectrically converted. Further, the light receiving circuit detects a signal due to the interference light, further obtains a process such as an envelope detection and the like, guides the signal to an arithmetic unit, where it is converted into each layer thickness of the multilayer sheet.

Here, the low coherent light source 2 used as the low coherent light is not particularly limited by the center wavelength and the half width of the spectrum. However, since the following problem may occur, the coherence length is reduced. 10 μm
It is desirable that the light source be a low-coherent light source having a center wavelength and a spectral half-width of about 40 μm. That is, the problem is that if the center wavelength is λ and the spectral half-value width is △ λ, the coherence length 1 is expressed by Equation 1.

[0025]

1 = λ ² / Δλ

By increasing the coherence length, when the measurement light 8 reflected at each boundary surface of the multilayer sheet 7 interferes with the reference light 12, if there is a layer having a thickness smaller than the coherence length, two layers sandwiching that layer Since the interference due to the boundary surface overlaps, it becomes difficult to separate the two interferences, and a problem arises in that the minimum thickness that can be separated is considerably large. Conversely, if the coherence length is shortened,
When approaching the incoherent light source and the traveling multilayer sheet 7 vibrates or tilts, the optical axis of the measurement light 8 reflected by the multilayer sheet 7 and the optical axis of the reference light 12 do not become substantially perpendicular. , The measurement light 8 is within the range of the coherence length approaching the incoherent light source.
It is difficult to interfere with.

More specifically, as the low coherent light source described above, for example, an SLD having a central wavelength of 780 nm and a coherence length of 35 nm having a spectral half width of 17 nm, a central wavelength of 840 nm and a coherence length of 35 μm having a spectral half width of 20 nm, or a central wavelength 840 nm
And a coherence length of 23 μm with a spectrum half width of 30 μm
SLD and the like. The center wavelength and the spectrum half width are not limited to the above examples, and may be any center wavelength and spectrum half width so that the coherence length is 10 μm to 40 μm.

FIG. 2 is a cross-sectional view of a main part of the apparatus in which the measurement principle shown in FIG. Here, 1 is a housing, 3 is a condensing lens for collimating coherent light emitted from the low coherent light source 2, and 5 is a first beam splitter 4
This is a first focus lens that collects the branched light.

[0029] Then 6 is a pressure type non-contact inhibition device incorporating an example of a non-contact suppression means by the compressed air (E). The suppressor 6 includes a pressurized air jet nozzle 20 having a circumferential directionality, a flat surface 21 for guiding the pressurized air from the nozzle 20 between the multilayer sheet 7 (running the process), and a nozzle 20.
An air reservoir 22 for making the air flow velocity of the compressed air from the air constant,
An air inlet 23 for supplying compressed air to the air reservoir 22 is provided. When the compressed air ejected from the nozzle 20 passes through the gap between the multilayer sheet 7 and the plane 21, the multilayer sheet 7 is suctioned to the plane 21 by the negative pressure effect of Bernoulli effect of the compressed air and the gap between the multilayer sheet 7 and the plane 21. Is smaller, the multilayer sheet 7 can be held in a substantially constant distance from the plane 21 in a non-contact manner by preventing the multilayer sheet 7 from coming into contact with the plane 21 by the cushioning effect of compressed air. Further, a through hole 24 is provided to allow the measurement light 8 to pass through the pneumatic non-contact suppressing device 6 and to guide the measurement light 8 to the multilayer sheet 7. The through hole 24 not only allows the measurement light 8 to pass therethrough, but also serves to replenish the air with a large negative pressure effect in order to partially prevent the negative pressure effect due to the Bernoulli effect from increasing. I also have it. In addition,
The multilayer sheet 7 may be disposed on the restraining device 6 (upside down positional relationship in FIG. 2) so as to be gripped in a non-contact manner.

The multilayer sheet 7, which is the object to be measured, has fine irregularities on its surface in order to provide appropriate slipperiness and smoothness. If the running multilayer sheet 7 is measured, the measuring light 8 Are scattered and noise is generated by the scattered light. Here, the frequency of the noise due to the scattered light is determined by the spatial frequency of the fine irregularities and the traveling speed,
In practice, if the frequency due to the fine irregularities can be regarded as a frequency in a limited range, the frequency of the noise due to the scattered light is determined by the traveling speed.

Reference numeral 9 denotes a second focusing lens for condensing the second split light by the beam splitter 4, and reference numeral 10 denotes a movable mirror driving unit for operating the movable mirror 11;
1 comprises a stage 25 using a precision cross roller guide or the like for guiding parallel movement and a drive motor 26 connected to and attached to the stage 25. The drive motor 26 is preferably a linear motor such as a linear ultrasonic motor or a linear stepping motor. When the drive motor 26 is driven, the movable mirror surface 11 reciprocates as shown by the arrow in FIG. 1, so that the optical path length of the reference light 12 can be changed. Therefore, the speed of the change of the optical path length of the reference light 12 can be changed by the speed at which the drive motor 26 is driven. Therefore, when the reference light 12 and the measurement light 8 interfere with each other, the frequency of the signal due to the interference light is changed to the movable mirror surface 11 Is determined by the speed of the drive motor 26 for reciprocating.

The movable mirror position detecting element (not shown) for detecting the position of the movable mirror surface 11 is an element such as a potentiometer, a micrometer, a PSD, or the number of oscillation pulses when the drive motor 26 is a motor operated by a pulse. Can be substituted. The movable mirror surface position detecting element is provided on the stage 25, and detects a position when the movable mirror surface 11 reciprocates. The information of the detected position is converted into a digital signal by an A / D converter (not shown), and is guided to a computer (not shown). The drive motor 26
Is a motor operated by a pulse, the number of oscillation pulses may be directly led to a computer and used as information on the position. Further, if it is assumed that the speed of the reciprocating movement of the movable mirror surface 11 is constant, the moving distance can be obtained by multiplying the speed by which the movable mirror surface 11 moves, so that information on the position of the movable mirror surface 11 is stored in a computer (not shown). It is also possible to obtain only by operation. Reference numeral 14 denotes a light receiving lens that receives the combined light 13 and guides the combined light 13 to a light receiving element.

Here, it is preferable that the light receiving element 15 has excellent spectral sensitivity in a wavelength range similar to the center wavelength of the low coherent light source 2. Therefore, for example, the low coherent light source 2
If the center wavelength is 780 nm or 840 nm in the above example, a photodiode such as a silicon photodiode or a PIN silicon photodiode having a spectral sensitivity peak in a similar wavelength range is more preferable.

Reference numeral 16 denotes a light receiving circuit for processing a signal based on the interference light. Reference numeral 19 denotes a holder for fixing the low coherent light source 2, which is provided with a Peltier element (not shown) in order to prevent the low coherent light source 2 from deteriorating due to a rise in temperature and from unstable light output. The coherent light source 2 is cooled, and automatic temperature control (ATC) and automatic output control (A
(PC).

The condensing lens 3, the first focusing lens 5, the second focusing lens 9, the light receiving lens 14 and the beam splitter 4 may be very ordinary ones. By integrating the lens 5, the second focus lens 9 and the light receiving lens 14 with the beam splitter 4, the number of parts is reduced, the apparatus is simplified, and the number of adjustment points is reduced as much as possible. In addition, the integration greatly reduces the reflection loss reflected by each component.

FIG. 3 is a front view of the apparatus shown in FIG. 2, that is, the traverse apparatus having the housing 1 mounted thereon. This makes it possible to traverse the housing 1 in the width direction of the multilayer sheet 7 (not shown) and perform measurement. Although not shown, the housing 1 is traversed in the width direction via the linear guide 17 by rotating the ball screw 18 using a servo motor, a linear motor, or the like as a drive source.

The thickness detecting means (D) according to the third aspect .
The band pass filter (F) attached to the light receiving circuit 16
The operation is described below in detail with reference to the block diagram of FIG. The incident light is photoelectrically converted by the light receiving element 15 and is subjected to current-voltage conversion by the amplifier 27.
The band pass filter 28 is entered. Bandpass filter 2
Reference numeral 8 denotes a filter having a narrow passband and abruptly attenuating outside the passband in order to attenuate noise due to scattered light based on fine irregularities on the surface of the multilayer sheet 7 and not to attenuate signals due to interference light. Is required. That is, a band-pass filter that is configured by a high-order filter having at least a fourth or higher filter stage and has a Chebyshev or Butterworth filter characteristic is preferable. If the traveling speed of the multilayer sheet 7 is constant, the frequency of the noise due to the scattered light is constant within a limited range of frequencies for the above-described reason. If the speed at which the movable mirror surface 11 is reciprocated is adjusted so that the frequency of the signal due to the interference light is sufficiently increased with respect to the frequency of the noise due to the scattered light, the noise due to the scattered light is reduced by the bandpass filter 28. Since the signal due to the interference light is not attenuated by the bandpass filter 28, the signal due to the interference light is sufficiently larger than the noise due to the scattered light, and the signal due to the interference light can be detected. Thereafter, the signal based on the interference light processed by the band-pass filter 28 is amplified by the AC amplifier 29, rectified by the rectifier 30, and envelope-detected by the low-pass filter 31.
This envelope signal is converted into a digital signal by an A / D converter (not shown) and is guided to a computer (not shown).

The thickness of each layer of the multilayer sheet 7 is finally calculated by a computer. That is,
The envelope signal of the interference light guided from the light receiving circuit 16 is represented by A
From the digital signal obtained by the / D conversion and information on the position of the movable mirror surface 11 derived from the movable mirror surface position detection element,
The position of the movable mirror surface 11 at the time of occurrence of interference is specified, and the thickness of each layer of the multilayer sheet 7 is calculated based on the result.

Finally, how the thickness of each layer is actually measured by the apparatus for measuring the thickness of the multilayer sheet-like plastic of the present invention constituted as described above will be described with a concrete example. . FIG. 5 shows an example of the multilayer sheet 7 to be measured by the apparatus of the present invention, which is a multilayer sheet 7a having three layers and five layers and a total thickness of 300 μm. In particular,
The first layer 32 and the fifth layer 36 are made of nylon, and the second layer 33 and the fourth layer
The layer 35 is made of an adhesive, and the third layer 34 is made of poval. While the multilayer sheet 7a is running, the side of the first layer 32 is gripped in a non-contact manner by the pneumatic non-contact suppressing device 6 and the measuring light 8 is incident. Are reflected by the respective boundary surfaces 37, 38, 39, 40, 41 and 42 and return to the beam splitter 4. On the other hand, the reference light 12 is reflected by the movable mirror surface 11 and is reflected by the beam splitter 4.
Return to At this time, the optical path length of the reference light 12 corresponding to each boundary surface of the multilayer sheet 7a can be changed by the movable mirror surface 11. FIG. 6 shows the relationship between the peak of the envelope signal due to the interference light from the light receiving circuit 16 and each boundary surface of the multilayer sheet 7a when measuring the multilayer sheet of FIG. 6, the horizontal axis represents the position of the movable mirror surface 11, and the vertical axis represents the magnitude of the envelope signal due to the interference light at each boundary surface. Here, the positions of the movable mirror surface 11 indicating the peaks 43, 44, 45, 46, 47, and 48 are represented by L1, L2, L3, L4, L5, L6.
The refractive index of the first layer 32 and the fifth layer 36 is n1, the refractive index of the second layer 33 and the fourth layer 35 is n2, the refractive index of the third layer 34 is n3, and the refractive index of air is 1. Then, the thickness d1 of the first layer 32, the thickness d2 of the second layer 33, and the thickness d of the third layer 34
3. The thickness d4 of the fourth layer 35 and the thickness d5 of the fifth layer 36 are
Equations (2) to (6) can be used.

[0040]

## EQU2 ## d1 = (L2-L1) / n1

## EQU00003 ## d2 = (L3-L2) / n2

D3 = (L4-L3) / n3

D4 = (L5-L4) / n2

D5 = (L6-L5) / n1

The band pass filter 28 shown in FIG.
Was examined in the running multi-layer sheet 7a of FIG. That is, in the envelope signal of the interference light by the light receiving circuit 16, the noise due to the scattered light and the change in the signal due to the interference light are examined depending on the presence or absence of the bandpass filter 28, and the result is shown in FIG. FIG. 9 shows a case where the band-pass filter 28 is provided. Obviously, the noise due to the scattered light in FIG. 8 is attenuated in FIG. 9 by the bandpass filter 28, indicating that the signal due to the interference light has been detected. That is, it can be understood that the addition of the band pass filter (F) in the third aspect is more effective.

[0042]

COMPARATIVE EXAMPLE As an example of the low coherent light source 2 according to the present invention, in order to compare interference by an SLD with interference by a halogen lamp, which is a conventional incoherent light source, interference when an object to be measured is tilted off-line. The change in signal due to light was examined. That is, when the object to be measured is a slide glass, a sample table for gripping the slide glass is provided, and the sample table is mounted on the gonio stage, and when the sample table is gradually tilted, the change in signal magnitude due to interference light is measured. And shown in FIG. The horizontal axis represents the inclination angle of the sample table, and the vertical axis represents the normalized interference value when the maximum signal intensity due to the interference light is set to 1. From this, it is apparent that the normalized coherence value of the low coherent light source 2 does not decrease even when the sample stage is tilted. Therefore, according to the low coherent light source 2, even if the multilayer sheet 7 running in the film manufacturing process vibrates or tilts, a signal due to interference light is obtained, and the thickness of each layer of the multilayer sheet 7 can be measured. I understand.

[0043]

Since the present invention is configured as described above, the following effects can be obtained.

In the stationary state, of course, during running (inline,
In a multi-layer sheet (on-line), non-contact and instantaneous high-precision measurement can be performed without destroying the thickness of each layer.

Even if the multilayer sheet itself is opaque by eye measurement, and even if the total thickness is as thick as about 2 mm, it is possible to measure each layer with high accuracy.

[Brief description of the drawings]

FIG. 1 is an optical path diagram showing a measurement principle according to the apparatus of the present invention.

FIG. 2 is a sectional view of a main part of the device of the present invention.

FIG. 3 is a front view of a traverse device equipped with a main part of the present invention.

FIG. 4 is a block diagram showing a light receiving circuit in the device of the present invention.

FIG. 5 is a view showing a cross section of a multilayer sheet in the apparatus of the present invention.

FIG. 6 is a measurement example of a multilayer sheet in the apparatus of the present invention.

FIG. 7 is a graph of the tilt angle of the sample table versus the normalized interference value in the apparatus of the present invention and the conventional apparatus.

FIG. 8 is a measurement example when there is no band pass filter (F).

FIG. 9 is a measurement example when there is a bandpass filter (F).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Low coherent light source 3 Condensing lens 4 Beam splitter 5 First focus lens 6 Pneumatic non-contact suppressor 7 Multilayer sheet 7a Multilayer sheet 8 Measurement light 9 Second focus lens 10 Movable mirror surface drive unit 11 Movable mirror surface 12 See Light 13 Synthesized light 14 Light receiving lens 15 Light receiving element 16 Light receiving circuit 17 Linear guide 18 Ball screw 19 Low coherent light source holder 20 Nozzle 21 Flat surface 22 Air pool 23 Air inlet 24 Through hole 25 Stage 26 Drive motor 27 Amplifier 28 Band pass filter 29 AC amplifier 30 Rectifier 31 Low-pass filter 32 First layer 33 Second layer 34 Third layer 35 Fourth layer 36 Fifth layer 37 Interface between air and first layer 38 Interface between first layer and second layer 39 Interface between two layers and third layer 40 Interface between third layer and fourth layer 41 Interface between the fourth layer and the fifth layer 42 Interface between the fifth layer and the air 43 Interference peak at the interface 35 44 Interference peak at the interface 36 45 Interference peak at the interface 37 46 Interference peak at the interface 38 47 Interface 39 48 interference peak of interface 40

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01B 11/00-11/30

Claims (3)

(57) [Claims] 1. A light source and interference light generating means for amplitude-dividing light from the light source into first and second split lights by a beam splitter, forming measurement light and reference light, and combining them again to generate interference. (A), measuring light means (B) for making the divided first branched light enter the multilayer sheet-like plastic as measuring light and reflecting the same, and the second divided light.
Reference light means (C) for making the reflected light incident on the mirror as reference light and reflecting the same, and detecting the thickness of each layer of the multilayer sheet-like plastic by the position of the mirror when the interference light is generated. A multilayer sheet-like plastic thickness measuring device comprising: a thickness detecting means (D);
The light source is a low coherent light source, and the measurement light source
Step (B) shows the vibration and tilt of the multi-layer sheet plastic
Non-contact suppression means (E) using compressed air for suppressing air pollution
A thickness measuring apparatus for a multi-layer sheet-like plastic, characterized in that a thickness is added . 2. The thickness measuring apparatus according to claim 1, wherein the low coherence light source has a center wavelength and a spectral half width such that a coherence length of the light source is 10 μm to 40 μm. 3. The thickness detecting means (D) attenuates noise based on scattered light from the multilayer sheet-like plastic surface provided by the measuring light means (B) and provided by the interference light generating means (A). 3. The thickness measuring apparatus according to claim 1, further comprising a band pass filter (F) for preventing a signal caused by the interference light from being attenuated.