JPH04115010U - thickness gauge - Google Patents

Abstract

(57) [Summary] [Purpose] Rather than measuring the thickness by determining the amount of attenuation of light that passes through the film, it is possible to accurately determine the thickness without errors by measuring the thickness using a new method. Our goal is to provide a thickness gauge that can. [Structure] A lens 3 that collects reflected or transmitted light in two paths based on the thickness of the film, a spectrometer 4 that separates the incident light into a wavelength spectrum and creates interference fringes, and its output spectrum. Linear C that converts data into electrical signals
CD5, a Fourier transform calculation unit 8 that converts frequency component data of interference fringes into time component data, a thickness calculation unit 9 that calculates thickness data from the output data, and a thickness display that displays the thickness. 10.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention measures film thickness online during the film manufacturing process. Regarding the thickness gauge.

0002

[Conventional technology]

Traditionally, devices that measure film thickness online have been equipped with radiation or infrared radiation. It is transmitted through a constant film and is absorbed and attenuated at a constant rate depending on the thickness of the film. A device called WEB GAGE that calculates the thickness of a film from the amount of transmitted light. There is.

0003 This thickness gauge includes a radiation thickness gauge that uses radiation and an infrared thickness gauge that uses infrared rays. be. A radiation thickness meter uses a radioactive element as a radiation source, and its radiation is measured as radiation. It uses β-rays emitted from linear elements. The amount of attenuation due to the transmission of β-rays is It is determined by the weight per unit area, and the unit surface of the object is determined from the amount of attenuated transmission. You can find out the weight per stack and, by extension, its thickness. Thickness measurement using this β ray is Regardless of the substance being measured, it has the advantage of being able to measure even opaque objects.

0004 Infrared thickness gauges use infrared light at a certain wavelength determined by the material of the film. Because infrared rays have the property of attenuating when transmitted, the wavelength determined by the material Light is irradiated and the thickness is measured based on the amount of attenuation. The film is transparent in visible light. The thickness is calculated from the amount of attenuation due to transmission, as it passes through the lume with almost no attenuation. This method is generally not used.

[0005]

[Problem that the idea aims to solve]

By the way, the radiation thickness gauge uses radioactive elements as a radiation source as mentioned above. Therefore, the amount of β-ray radiation from radioactive elements is essentially non-uniform and has undefined statistical fluctuations. For example, when measuring the thickness of a thin film of 10 μm or less, it is possible to measure with high accuracy. cannot be determined. Furthermore, the instability of the radiation amount and the rate of absorption by the film On the other hand, the resolution is limited because the rate of absorption and attenuation by air is large. , measurement of thin films is difficult.

[0006] In addition, with an infrared thickness gauge, the direction of the light source from the front side of the film and the back side of the film is measured. Interference fringes occur due to the interference of light on two different paths, and data from transmitted light interferes. The fringes cause sinusoidal fluctuations, making high-resolution measurements difficult. Furthermore, the film surface An equivalent attenuation occurs based on the loss of light intensity caused by surface reflection, and an equivalent attenuation occurs due to transmission. Attenuation cannot be measured accurately.

[0007] This invention was made in view of the above points, and its purpose is to Instead of measuring thickness by determining the amount of attenuation of light that passes through the film, a new method is used to measure thickness. We offer a thickness gauge that can accurately determine the thickness without error by measuring the thickness. It is about providing.

[0008]

[Means to solve the problem]

The present invention, which solves the above-mentioned problems, is designed to reduce the amount of light emitted from a light source while driving. Collects reflected light or transmitted light from two paths based on the thickness of the film from the film sheet. An optical system that separates the light incident from the optical system into a spectrum of wavelengths and creates interference fringes. Create a spectrometer and detect the intensity of light at each wavelength from the wavelength spectrum of the spectrometer's output. and a linear CCD that detects interference fringe data and converts it into an electrical signal, Fourier transform calculation unit that converts frequency component data of interference fringes into time component data and a thickness calculation unit that receives the output of the Fourier transform calculation unit and converts it into thickness data. , and a thickness display section that displays calculated thickness data. It is something.

[0009]

[Effect]

Light is emitted from a light source onto a moving film sheet, and the light is generated from the thickness of the film sheet. A spectrometer separates the optical data from the two paths to create interference fringes. This interference fringe data is It is converted into an electric signal in the CCD and sent to the Fourier transform calculation section and the thickness calculation section. This is treated as thickness data and displayed on the thickness display section.

0010

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. In the figure, 1 is the thickness This is a film sheet whose strength is to be measured. 2 transmits film sheet 1 It is a light source that emits light. The light transmitted through film sheet 1 is passed through the lens (optical system) The light is focused by 3. 4 consists of a diffraction grating, a prism, and a lens system. In addition to the spectral patterns absorbed by the film components, there are also two paths of different optical inputs. It is a spectrometer that generates interference fringes. 5 represents each of the spectra of light separated by the spectrometer 4. It is a linear CCD that detects the intensity of light for each wavelength, converts it into an electrical signal, and outputs it.

0012 6 is a CPU that calculates the output data of the linear CCD 5, and eliminates noise etc. of the input signal. A low-pass filter (hereinafter referred to as LPF) 7 that removes high frequencies of Fourier transform the input data to convert frequency space data to time space data. From the Fourier transform calculation unit 8 and the periodic interval of the interference fringes expressed by the time interval, It is comprised of a thickness calculation section 9 that calculates the thickness of the film sheet 1.

[0013] 10 is a thickness display unit that displays thickness data calculated by the thickness calculation unit 9 of the CPU 6; It is.

[0014] Next, the operation of the embodiment configured as described above will be explained. Emit light from light source 2 and transmit the film sheet 1. This light is divided into two types: light that passes through the film as is, and light that passes through the film screen. It is reflected from the output surface of film sheet 1, reflected again at the incidence surface, and exits from film sheet 1. This results in two lights with different paths. FIG. 2 shows the state in which the light takes two paths. In the figure, the same reference numerals are used for parts equivalent to those in FIG. D detects light It is a detector. (A) Figure shows the case of transmitted light, (B) Figure shows the case of reflected light. ing. In either case, reflection from both sides of the film sheet 1 causes two routes. light is occurring.

[0015] The transmitted light is focused by a lens 3 and guided to a spectrometer 4. Spectrometer 4 is a component of A diffraction grating separates incident light into a spectrum of wavelengths. Linear CCD5 is on. The intensity of light for each wavelength is detected from the spectrum of the emitted light. At this time, the interference fringes Data is detected.

[0016] Data of interference fringes detected by the linear CCD 5 is sent to the CPU 6. C Data is processed in the PU6 as follows. LPF7 is a high frequency component such as noise. The interference fringe data is Fourier-transformed by removing the interference fringe frequency components and passing only the frequency components of the interference fringe. It is input to the conversion calculation section 8. The Fourier transform calculation unit 8 converts the frequency component data of the interference fringes into The data is converted into time component data and input to the thickness calculation section 9. Thickness calculation section 9 input data The thickness data of film sheet 1 is calculated from. In this way, CPU6 smell The data converted into thickness data is displayed on the thickness display section 10.

[0017] As explained above, according to this example, if the film is transparent, It is possible to measure down to the submicron order. In an infrared thickness gauge, the object to be measured Since the infrared absorption wavelength band differs depending on the component, the infrared absorption wavelength band varies depending on the measurement film. In order to select the absorption wavelength band, it is necessary to change the infrared filter, and the absorption coefficient and A comparison table or calibration curve with film thickness was required. In the device of this example As mentioned above, any object that transmits light is not limited to film, but can also include glass plates and plastic plates. The thickness of the plastic board, etc., is also sensitive to light waves in a wide range of wavelengths from visible light to infrared light. Accurate measurements can be made without making any changes to the length of the belt or the like.

[0018]

[Effect of the idea]

Measuring film thickness by interference fringes rather than by attenuation Since we decided to do this, we are now able to obtain accurate thickness without any errors. , the practical effect is great.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a thickness gauge according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of generation of interference fringes.

[Explanation of symbols]

1 Film sheet 2 Light source 3 Lens (optical system) 4 Spectrometer 5 Linear CCD 8 Fourier transform calculation section 9 Thickness calculation section 10 Thickness display section

Claims (1)

[Scope of utility model registration request] 1. An optical system (3) that collects reflected light or transmitted light from a traveling film sheet (1) in two paths based on the thickness of the film caused by light projected from a light source (2); , a spectrometer (4) that separates the light incident from the optical system (3) into a spectrum of wavelengths and creates interference fringes; and a spectrometer (4) that separates the light incident from the optical system (3) into a spectrum of wavelengths, and calculates the intensity of light for each wavelength from the spectrum of wavelengths output from the spectrometer (4). a linear CCD (5) that detects interference fringe data and converts it into an electrical signal; and a Fourier transform calculation unit (8) that converts frequency component data of the interference fringe into time component data. A thickness calculation section (9) that receives the output of the Fourier transform calculation section (8) and converts it into thickness data.
and a thickness display section (1) that displays the calculated thickness data.
0).