JPS626482Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is a thickness measuring device that measures the thickness of a long film such as a plastic film during its manufacturing process by utilizing the interference phenomenon of transmitted light. Regarding.

For example, when a white light beam is irradiated perpendicularly to a film from a light source, the transmitted light from the film has 2nD (where n is the optical refractive index of the film and D is the thickness of the film) due to reflection inside the film. ) contains light out of phase. By the way, when measuring the spectrum of such transmitted light, due to the optical interference phenomenon caused by phase-shifted light,
The received light intensity at each wavelength, expressed in a graph where the vertical axis is the received light intensity of transmitted light and the horizontal axis is the wavelength, is λ = 2nD/k (k is the interference order of light)
It is shown that the maximum (or minimum) occurs at a wavelength that satisfies the equation. By determining the two wavelengths at which this maximum (or minimum) occurs, the value of k is determined, and by substituting the known value of the refractive index n, the thickness D of the film can be determined.

In order to measure the thickness of a film using this interference phenomenon of transmitted light, it is necessary to place the part that irradiates the film with light and the part that receives the transmitted light at positions facing each other across the film. However, the transport path of the film whose thickness is to be measured is usually already set, and transport means such as rollers are provided at each part of the transport path, and there may not be enough space around the film. is normal. If we dare to create a space around the film for the irradiating part and the light receiving part without a transport means, the film will not be supported over a long distance, and the film will not be able to reach the position where the thickness should be measured. Inconveniences such as flapping may occur.

To solve this problem, it is conceivable to connect optical fibers to the light source section and the detection section, respectively, and guide the tips of the fibers toward the film side, so that the tips of each optical fiber constitute a light emitting section and a light receiving section. .

In this way, the irradiating section and the light receiving section can be compactly integrated, and there is no need to secure a large space around the film for the irradiating section and the light receiving section. It can be provided at any position. Further, by moving the irradiating section and the light receiving section in a direction across the film, the thickness of each part in the width direction of the film can be measured.

However, when the irradiating section and the light receiving section for the film are configured using optical fibers in this way, the following new problems arise.

The first problem occurs when the tip of the optical fiber, which is the irradiating part or the receiving part, is moved across the film. When the tip of the optical fiber is moved, the curved shape of the middle part of the optical fiber changes. When the curved shape of the optical fiber changes in this way, the optical signal passing through the optical fiber is affected by the change in the shape of the optical fiber, and the light intensity distribution curve changes.

The second problem is that optical interference information focused on one point on the film surface cannot be obtained. In other words, it is desirable to irradiate the irradiation light spot-wise on one point on the film surface and to receive only the transmitted light that passes through one point on the film surface, but the irradiation light from the optical fiber is not a little diffused. , a wide area on the film is irradiated, and a light receiving section made of an optical fiber takes in transmitted light corresponding to this wide area. In short, the light incident on the light-receiving optical fiber includes optical interference information over a wide range, making accurate thickness measurement difficult.

The present invention solves the above-mentioned problems when the light irradiation part for the film and the transmitted light reception part are composed of optical fibers. The purpose of this invention is to eliminate changes in the thickness of the film, and to capture optical interference information focused on a single point on the film surface to enable accurate thickness measurement.

Therefore, in order to achieve the above object, the present invention provides a moving means for integrally moving a white light source section and a detection section for detecting the intensity distribution of light transmitted through the film with respect to wavelength in a direction across the film; An irradiation optical fiber and a light reception optical fiber are connected at one end to the light source section and the detection section, and the other ends are led out to positions opposite to each other via a film, and when the light source section and the detection section are moving, the two ends are connected to each other. The film thickness measurement method is equipped with a holding means for holding both optical fibers so that the curved state of the optical fibers is maintained constant, and a pair of focusing means consisting of a focusing lens and a slit attached to the tips of each optical fiber. Configured the device.

FIG. 1 is a schematic diagram of an apparatus according to an embodiment of the present invention. The light source section 1 is composed of a box containing a xenon lamp and the like. The xenon lamp is
Although it is used as a light source that emits white light, other white light sources may also be used. The optical fiber 2 has one end connected to the light source section 1, and the light beam from the light source section 1 is transmitted to the optical fiber 2 through this connection.
You will be guided inside.

The detection unit 3 is for measuring the spectrum of light transmitted through a film 5, which will be described later, and includes a spectrometer such as a prism or a diffraction grating, and an image sensor for measuring the spectrum. The image sensor is constructed by linearly arranging light-receiving elements, but any image sensor may be used as long as it can measure light intensity in a short time in accordance with the spectrum of light. One end of an optical fiber 4 is connected to the detection section 3, and the light that has passed through the film 5 is guided from the optical fiber 4 to the spectroscope in the detection section 3 via this connection. The film whose thickness is measured is:
Usually, a transparent film is used, but any colored film may be used as long as it can transmit light.

The film 5 is made to run perpendicularly to the plane of the paper at a predetermined speed by a known film feeding device (not shown), and the light source section 1 and the detection section 3 are installed on a flat movable table 6. be done. The moving platform 6 can be moved in the direction of the arrow by means of a suitable known moving device such as a roller. The other end of the optical fiber 2, one end of which is connected to the light source section 1, extends to an appropriate position below the film 5 via the lower part of the moving table 6.
The other end extends to a suitable location above the film 5 so as to be able to receive the focused beam 7 emanating from the other end of the optical fiber 2 .

One end of a holding rod 8 is attached to the lower surface of the moving table 6, and a gripping portion 9 is formed at the other end of the holding rod 8. The lower optical fiber 2 is held by a gripping portion 9 of a holding rod 8, and this gripping allows the optical fiber 2 to be held even when the movable table 6 repeatedly reciprocates in the direction of the arrow. , can maintain the curved state shown in the drawing. Further, one end of another holding rod 10 is attached to the right side surface of the moving table 6. A gripping portion 11 is formed at the other end of the holding rod 10, and the upper optical fiber 4 is held in a curved state in the same manner as described above by being gripped by this gripping portion 11. can be retained.

An electrical signal related to the spectrum of light detected by the detection unit 3 is input to the computer 13 via an electric wire 12 connected to the detection unit 3 . The electronic computer 13 is fixed to the installation surface, and performs calculation processing of the thickness of the film 5 based on the electrical signal from the detection section 3 inputted via the electric wire 12.

The fixed support 14 is fixed to the installation surface and consists of a vertical rod 141 and a horizontal rod 142, and the right end of the horizontal rod 142 is rigidly connected to the upper end of the vertical rod 141.

Next, the features of the present invention will be explained. That is, in the figure, there is a gap between the other end of the lower optical fiber 2 and the other end of the upper optical fiber 4.
A convex lens 15, slits 16 and 17, and a convex lens 18 are installed in this order from the bottom to the top. These convex lenses 15 and 18
The slits 16 and 17 are attached by attachment means (not shown) so that they can move together with the optical fibers 2 and 4 as the moving table 6 moves in the direction of the arrow.

FIG. 2 is an enlarged schematic diagram of the portion surrounded by the chain line in FIG. 1, for explaining in more detail the features of the present invention described above. The white light ray 7 from the optical fiber 2 below,
They are indicated by reference numerals 71 and 72 in FIG.
One of the white light beams 71 is focused by the first convex lens 15 located above the lower optical fiber 2 onto the thickness measurement point 19 of the film 5, and then focused by the first convex lens 15 located above the lower optical fiber 2. The light is focused onto the upper optical fiber 4 by two convex lenses 18 . Therefore, the transmitted light of the film 5 received by the upper optical fiber 4 contains sufficient information regarding the thickness of the film.
As a result, the detection unit 3
In this detection unit 3, the transmitted light input to the
The spectral measurements required for the film thickness measurement process can easily be made. The slits 16 and 17 block the other light ray 72 emitted from the lower optical fiber 2 so that the film 5 is not irradiated with the other light ray 72. This is because the convex lens 15 and the like have an optical property of causing chromatic aberration near their ends, so this is to remove the light rays from the portion of the convex lens that causes chromatic aberration.

As explained above, according to the present invention, the light irradiation part for the film and the light reception part for the transmitted light are respectively constituted by optical fibers, so a large space is not required for the irradiation part and the light reception part. figure,
The thickness of the film can be measured at any position along the film transport path.

Moreover, since the optical fiber moves together with the light source section and the detection section, and its curved shape is held constant by the holding means, the light intensity distribution curve does not change due to a change in the curved shape. Therefore, the thickness of each part of the film in the width direction can be measured as necessary.

Furthermore, since a focusing means consisting of a focusing lens and a slit is attached to the tip of each optical fiber, the irradiated light is irradiated onto a single point on the film in the form of a spot and is not diffused. In this case, only the transmitted light that passes through one point on the film is received, and thereby, the optical interference information of one point on the film can be supplied to the detection section, and the thickness can be accurately measured.

In this case, since the chromatic aberration caused by the converging lens is removed by the slit, unnecessary light information due to the chromatic aberration does not enter the light-receiving optical fiber, and from this point of view as well, accurate thickness measurement is possible.

In addition, since the optical fiber is provided with a holding means, it is possible to use this holding means to set the focusing means at the tip of the optical fiber, so that even though it has the focusing means, it is possible to set the focusing means at the tip of the optical fiber. , the structure of the tip of the optical fiber can be relatively simplified, and as a result, the irradiating part and the light receiving part, which are composed of the optical fiber and the focusing means, can be arranged without any problem in a narrow space on the surface of the film. can.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus according to an embodiment of the present invention, and FIG. 2 is an enlarged schematic diagram of the main parts thereof. 1...Light source part, 2, 4...Optical fiber, 3...
...Detection section, 5...Film, 15, 18...Convex lens, 16, 17...Slit.

Claims (1)

[Claims for Utility Model Registration] A moving means for integrally moving a white light source section and a detection section for detecting the intensity distribution of light transmitted through the film with respect to wavelength in a direction across the film; An irradiating optical fiber and a light receiving optical fiber are connected at one end and the other end is led out to a position facing each other via a film, and the curved state of both optical fibers is constant during movement of the light source section and the detection section. A holding means for holding both optical fibers so that the optical fibers are maintained at the same temperature, and a pair of focusing means each consisting of a focusing lens and a slit attached to the tip of each optical fiber, respectively. Device.