JPS6222006A - Measuring instrument for film thickness - Google Patents

Abstract

PURPOSE:To take an accurate measurement without contacting nor the influence of a shift in the position of a film to be measured by calculating the quantities of absorption in the object film for light beams which are transmitted through two band-ass filters and differ in wavelength and then calculating the film thickness from the quantities of absorption. CONSTITUTION:Light from a light source 2 is transmitted through a magnetic tape 1, transmitted through two different-wavelength band-pass filters 8b and 8c through a rotary disk 8, and converted by a photodetector 4 photoelectrically. The magnetic film 1b of the tape 1 has wavelength dependency, so the output of the photodetector 4, i.e. the quantities of different-wavelength transmitted light beams are converted into digital values in series by an A/D converter 5 and a processing circuit 6 calculates the ratio of the both or the gradient of transmission characteristics between the two wavelengths to find its transmission start wavelength, thereby obtaining an output proportional to the film thickness. Consequently, an accurate measurement is taken without contacting nor the influence of a shift in the position of the film.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a film thickness measuring device for measuring the film thickness of a coating film for controlling and monitoring a coating machine in a manufacturing line for, for example, magnetic tape. It is.

[Conventional technology]

Figure 4 is a configuration diagram of a conventional eddy current type film thickness measuring device.
) is a magnetic tape, which has a coating film (1b) of magnetic material on a base material (1a) such as polyester. CIυ is a detector, which has an excitation winding (ltb) wound around a core (lla), and is excited by an oscillator 4.

Next, the operation will be explained. An excitation magnetic field is generated between the open ends of the core (lla), but the excitation impedance changes if a magnetic body is located close to the core (lla). This change varies depending on the time, size, position, etc. of the magnetic body, so if this change in impedance is detected, the thickness of the magnetic body can be detected under conditions of constant characteristics, constant position, and constant width.

[Problem that the invention seeks to solve]

Conventional film thickness measuring devices cannot be sensitively and stably measured unless the distance between the film to be measured and the detector is kept constant and the film and the detector are in close contact with each other, and cannot be incorporated into a production line.

The present invention has been made to solve the above-mentioned problems, and provides a film thickness measuring device that is non-contact and is not affected by changes in the position of the film to be measured.

[Means for solving problems]

The film thickness measuring device according to the present invention includes: a light source; a light receiver that transmits light from the light source to a film to be measured and receives the light;
The apparatus includes a rotary plate provided on the optical path and having first and second narrow band filter sections and a light shielding section, and a processing circuit that calculates the film thickness from the output of the light receiver.

[Effect]

In the film thickness measuring device according to the present invention, a processing circuit determines the amount of light absorbed by the film to be measured after passing through each narrowband filter, and calculates the film thickness from this amount of absorption.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram of the present invention, and the same number 0 as in Fig. 4 indicates the same thing. (The illusion is a light source with a wavelength band that passes through the magnetic tape (1), (3) is a lens, (4) is a light receiver, (5) is an A/D converter, (6) is a digital processing circuit, (7) ) is the motor, and (8) is the rotary plate attached to the shaft of the motor (7), whose plan view is shown in Figure 2. In Figure 2, the shaded area (8a) is the light shielding part that does not transmit light. , the white part (8b) is the first narrow band filter part, and the dotted part (8c)' is the previous filter part (8b).
is a second narrow band filter section having a different wavelength.

Returning to Fig. 1, (9) drives the motor (7) and transmits the position information of the rotary plate (8) to the digital processing circuit (
This is a pulse drive circuit that outputs to 6). FIG. 3 is a characteristic diagram showing the wavelength dependence of the light transmittance of the magnetic tape (1).

Next, the operation will be explained.

The light emitted from the light source (2) is focused by a lens (3) and transmitted through the magnetic tape (1). Depending on the position of the rotary plate (8), this transmitted light is blocked or transmitted through narrow band filters (8b) (8c) of different wavelengths. This transmitted light is photoelectrically converted by a light receiver (4). By the way, the magnetic tape (1) is composed of a base material (1a) and a coating film (1b).Since the base material (1a) is a transparent material such as polyester, almost 100% of light passes through it, and the coating film The transmission characteristic of (1b) has wavelength dependence as shown by the solid line in the second factor. Moreover, the characteristics are as shown by the dashed dot line when the film is thicker.
When it is thin, the transmission start wavelength differs depending on the thickness, as shown by the dotted line. On the other hand, the change in the light intensity of the light source (2), etc. is the same as the transmission start wavelength, but the slope is different. Therefore, the output of the photoreceiver (4) is measured by A/D in time series to measure the amount of transmission of different wavelengths.
The converter (5) converts it into a digital value, and the digital processing circuit (6) calculates the ratio of the two or the slope of the transmission characteristic between the two wavelengths, and then determines the transmission start wavelength to generate an output proportional to the film thickness. can be obtained stably. By the way, the motor (7
) is driven by the pulse drive circuit (9) and the information is input to the digital processing circuit (6) to detect when the light does not enter the receiver (4) and when the light transmitted through the narrow band filter (8b) You can understand the relationship between when light is entering the filter (8c) and when light is passing through the filter (8c), and by taking the difference from when no light is entering, and taking this as the true value, it is not affected by dark current. Become something.

〔Effect of the invention〕

As described above, according to the present invention, the film thickness is determined from the wavelength dependence of the light transmittance of the film to be measured, so even if the position of the film to be measured changes, it is not affected by the dark current of the photoreceptor. The film thickness can be measured accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a film thickness measuring device according to an embodiment of the present invention, FIG. 2 is a plan view of the rotary plate in FIG. FIG. 4 is a configuration diagram of a conventional film thickness measuring device. In the figure, (lb) is a magnetic coating film as a film to be measured, (2) is a light source, (4) is a light receiver, (5) and (6) are an A/D converter and a digital processing circuit, respectively. Processing circuit, (8) rotating plate, (8a) light shielding part, (8b)
(8c) is a first narrowband filter section, and (8c) is a second narrowband filter section. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (6)

[Claims] (1) A light source that emits light in a wavelength band that passes through the film to be measured;
a light receiver that transmits light from the light source through the film to be measured, receives the transmitted light, and converts it photoelectrically; a first narrow band filter section that transmits light of a first wavelength; and a light receiver that transmits light of a first wavelength; A rotary plate configured such that a second narrow band filter section that transmits light and a light shielding section that does not transmit light are sequentially arranged in the circumferential direction and rotated so that the respective sections are sequentially interposed on the path of the light. . A film thickness measuring device comprising a processing circuit for determining the amount of light absorbed by the film to be measured at both wavelengths from the output of the light receiver and calculating the thickness of the film to be measured from the absorption amount. (2) A film thickness measuring device according to claim 1, characterized in that the film to be measured is moved in a direction perpendicular to the direction of incident light, and the film thickness is continuously measured. . (3) The processing circuit is an A/D converter that converts the output of the photoreceiver.
3. The film thickness measuring device according to claim 1, comprising a converter and a digital processing circuit that digitally processes the output of the A/D converter to calculate the film thickness. (4) The film thickness measuring device according to claim 3, wherein the digital processing circuit calculates the ratio of the amount of light transmitted at each wavelength and calculates the film thickness from the ratio. (5) The film thickness according to claim 3, wherein the digital processing circuit calculates the transmission start wavelength from the slope of the amount of light transmitted at each wavelength between two wavelengths, and calculates the film thickness from this. measuring device. (6) The film thickness measuring device according to claim 4 or 5, wherein the digital processing circuit performs calculations using the difference between the value in the light shielding part and the value in each narrow band filter part. .