JPS6073406A - Infrared-ray thickness meter - Google Patents

Abstract

PURPOSE:To measure the thickness of even an extremely thin film precisely by making P-polarized light incident at a Brewster angle. CONSTITUTION:A light source part 2 has an infrared-ray generation part 21 which generates intermittently infrared rays 20 containing at least two wavelength components, i.e. wavelength component (measured wavelength lambdas) showing the absorption characteristics of an extremely thin film 1 running at a high speed as shown by an arrow and wavelength component (reference wavelength lambdaR) showing nonabsorption characteristics, and a polarizer 22 which polarizes the infrared rays 20 into P-polarized light having an oscillation component parallel to the incidence surface of the film 1. A photoscanning part 3 allows the P-polarized light 23 of the light source 2 to scan on the film 1 within a specific + or -DELTAtheta angle range about the Brewster angle thetaB determined by the refractive index of the film 1. A signal processing part 7 make transmitted light signals (b) and (c) of incident light 23 incident at the Brewster angle thetaB effective as to light projected upon the film 1 to obtain thickness data (g) on the basis of which the thickness of the film is determined.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention utilizes the specific absorption of infrared rays by plastics to continuously increase the thickness of a film, especially a transparent or translucent film that is extremely thin and runs with fluctuations. Regarding infrared thickness #1 suitable for measurement.

[Prior Art 1] When a plastic film is irradiated with infrared rays, an infrared spectrum is obtained that is related to the specific absorption and thickness of the material. Infrared film thickness gauges are based on the principle that the amount of absorption of a specific wavelength of infrared rays is proportional to the thickness of the film.
On the contrary, it attempts to determine the film thickness by measuring the amount of transmitted light.
Various devices using this principle are known, such as in Japanese Patent No. 155. However, the measurement target in conventional equipment is
This is a film with a thickness of up to 10 μl+, whereas films produced using currently developed film manufacturing technology have an extremely thin film with a thickness of 0.5 to 5.0 μl+. There is a problem in that conventional devices cannot be applied to films as they are, or even if they are applied, they cannot be accurately measured.

This is because when a parallel beam of infrared light is irradiated onto a film to be measured, mutual interference due to internal multiple reflections occurs on the top and bottom surfaces of the film, increasing measurement errors and eventually making it impossible to measure the film thickness. , and as the thickness of the film becomes extremely thin, the amount of specific absorption of the irradiated infrared rays decreases, resulting in a poor signal-to-noise ratio of the detection signal, and two reasons why it is not possible to obtain the resolution required by increasing the film thickness. [Object of the Invention] The main object of the present invention is to eliminate optical interference, in other words, to improve the accuracy of measuring the thickness of a film by preventing internal multiple reflections of the film from occurring.

Another object of the present invention is to make it possible to obtain a desired resolution even with an extremely thin film, regardless of the sensitivity limit of the detection system for light transmitted through the film.

Ultra-thin films include those that are left still, as well as films that run continuously.

Another object of the present invention is to take sufficient measures against fluctuations in a continuously running film.

Another object of the present invention is to enable simultaneous photometry at the same location to continuously and accurately measure the thickness of a film traveling at high speed.

Because there are error factors that depend on the optical system, electrical system, and sample system in thickness measurement, it is necessary to frequently check the calibration curve.To overcome this, so-called three-wavelength (or multi-wavelength) photometry is used. This is because conventional two-liquid length time-division photometry using a rotary plate equipped with an interference filter inevitably includes measurement errors when the film is running at high speed.

Still another object of the present invention is to provide a calibration means, preferably an automatic calibration means, to prevent errors such as changes over time depending on the wavelength characteristics of the optical system including the light source and the photodetection system. It is.

[Summary of the invention] A polarizer that intermittently generates infrared rays in a band including at least two wavelength components, a wavelength component exhibiting absorption characteristics unique to the film and a wavelength component exhibiting non-absorption characteristics, and polarizes the infrared rays into P-polarized light. A light source section including a light source section, and an infrared ray output from the light source section are emitted from an oblique direction with respect to the film surface of the film at a predetermined angle, that is, the Brewster angle determined by the material of the film, and the projector is centered around the projecting angle. an optical scanning section that causes the infrared rays to scan the film by continuously changing the infrared rays within a predetermined angular range, and a reflected light that receives the reflected infrared light projected onto the film and corresponds to the intensity of the received light. A reflected light receiver that outputs a signal, which receives the transmitted infrared light projected onto the film, separates it into at least the above two wavelength components, and outputs a transmitted light signal according to the received intensity of each spectral light. a transmitted light spectrometer that receives the reflected light signal and the transmitted light signal, removes background noise from the reflected light signal and the transmitted light signal, identifies the reflected light signal, and detects the minimum reflection signal. A signal processing unit that validates a transmitted light signal at a light intensity and calculates thickness data that is the basis for quantifying the thickness of the film based on the validated transmitted light signal of at least the three wavelength components. When P-polarized light parallel to the incident plane or incident on the film at Brewster's angle, there are no reflected light components on the top and bottom surfaces of the film, and optical interference is eliminated. It becomes transmitted light, eliminating characteristic absorption in the film and eliminating energy loss. Some films are left stationary at a predetermined location, while others run continuously and are accompanied by fluctuations.For this reason, if the light is incident at a single star angle, the transmitted light signal from only the outside is effective. By using the fact that there is light reflected from the film when the light is incident at a angle other than Brewster's angle, the light scanning section and the reflected light receiving section detect the reflected light and the incident light is adjusted to the Brewster's angle. It constitutes a part of the signal processing unit that identifies whether the light is incident at the Brewster angle, and calculates film thickness data based on the transmitted light signal only when the light is incident at the Brewster angle. In addition, instead of time-division photometry that irradiates different locations as in the past, it uses simultaneous photometry (wavelength-division photometry) at the same location to continuously and accurately measure the thickness of a film traveling at high speed. . Note that the wavelength-division photometry described above is not limited to using only two wavelengths, and in some cases, wavelength-division photometry of multiple wavelengths is effective.

The second invention includes all of the above-mentioned specific inventions in its main parts, and includes an optical path converting section that converts the optical path of transmitted light so that the infrared rays projected onto the film are transmitted through the film multiple times, It is characterized by increasing the absorption ability of the wavelength component of the infrared rays that transmits through the film, which exhibits absorption characteristics unique to the film.In the case of Brewster's angle incidence, there is no multiple reflection light inside the film and the energy loss is negated. Moreover, since the actual optical path length is achieved using a multi-pass optical system with oblique incidence related to Brewster's angle, rather than normal incidence to the film as in conventional methods, it is possible to detect light transmitted through the film even if the film is extremely thin. It is possible to obtain the desired resolution regardless of the sensitivity limit of the system.

A third invention includes all of the above-mentioned specific inventions in its main part, and the subject film is continuously moved and the film is detected based on the reflected light signal outputted from the reflected light receiving section in accordance with the fluctuations caused by the running of the film. It is characterized by comprising a light scanning control section that automatically corrects the set light projection angle related to the Brewster angle, and preferably the light scanning section includes a vibrating mirror, and the set light projection angle in the light scanning control section is set. The angle is corrected by servo control.

And, the fourth invention includes all of the above-mentioned specific inventions in the main part, and similarly to the third invention, the subject film runs continuously, and a signal for calculating thickness data that is the basis for quantifying the thickness of the film is provided. The present invention is characterized in that it further includes a data processing section that calculates the true thickness of the film based on the thickness data output from the processing section and a preset thickness conversion function.

Preferably, the light source section, the light scanning section, the reflected light receiving section, and the transmitted light spectroscopic section are configured integrally, and the rod structure is arranged so as to be movable in the width direction of the film.

Then, a sample film of the same type is fixed on the same plane as the running surface of the film on the outside in the width direction of the running film, and the above-mentioned rod structure is moved to this sample film position to collect data of the sample film. , the data of the subject film is automatically calibrated using the data of the sample film, and the calibrated thickness data is output to the data processing section.

Hereinafter, the present invention will be specifically explained with reference to embodiments shown in the accompanying drawings together with other features.

[Example] FIG. 1 is a basic configuration diagram of the embodiment.

1 is an ultra-thin film that runs at high speed in the direction of the arrow (hereinafter referred to as the film), 2 is the wavelength component that exhibits absorption characteristics specific to film 1 (hereinafter referred to as the measurement wavelength) and non-absorption characteristics. wavelength component (hereinafter referred to as reference wavelength)
an infrared ray generator 21 that intermittently generates infrared rays 20 including at least two wavelength components of
This is a light source unit that includes a polarizer 22 that polarizes 0 to polarized light having a vibration component parallel to the incident plane of the film 1, that is, P polarized light. Reference numeral 3 denotes a light scanning unit that scans the P-polarized light 23 from the light source unit 2 on the film 1 from an oblique direction in a predetermined angular range ±Δθ centering on the Brewster angle θB determined by the material (particularly the refractive index) of the film 1. It consists of a vibrating mirror 30 and a driving section 31 that drives the vibrating mirror 30.

- 4 is a reflected light receiving section which receives reflected light 4 () of the P-polarized light 23 projected onto the film 1 and outputs an electric signal corresponding to the received light intensity, that is, a reflected light signal a; 41, a cone mirror 421 and a reflected light detector 43.

Reference numeral 5 denotes an optical path conversion unit that converts the optical path of the transmitted light 50 so that the P-polarized light 23 projected onto the film 1 passes through the film 1 multiple times, and 6 represents the transmitted light that has transmitted through the film 1 multiple times. 51, the received light is split into at least the above two wavelength components λS and λR, and an electrical signal (hereinafter referred to as a transmitted light signal) corresponding to the intensity of each spectral light is generated.
A transmitted light/spectroscopic section that outputs a measurement wavelength signal b for the wavelength λS and a reference wavelength signal C for the wavelength λ;
0 is a flat reflecting mirror.

7 receives the reflected light signal a, the measurement wavelength signal S, and the reference wavelength signal C, and also receives the intermittent signal d output from the light source section 2 and the periodic signal e output from the optical scanning section 3.
and identifies the received reflected light signal a and activates the transmitted light signals S and C of the incident light 23 only when it is incident at the Brewster angle θB among the light projected onto the film 1. At the same time, it is a signal processing unit that calculates thickness data g, which is the basis for quantifying the thickness of the film, based on the validated transmitted light signals S and C. The control circuit section 70 provides a control signal f to the controller, and the signal calculation circuit section 71 calculates thickness data and provides the thickness data g to an external device (not shown).

The intermittent light generated by the infrared generation section 21 is transmitted to the vibrating mirror 3
It receives an angular deflection of ±Δθ about the incident angle set by 0, that is, the Brewster angle θB. The angularly polarized intermittent light enters the polarizer 22, and only the P-polarized light component is emitted. For example, a wire grid type polarizer is used as the polarizer 22. 7. .

When the P-polarized light 23 that has passed through the polarizer 22 is incident on the film 1 to be measured, part of it is reflected as reflected light 40 and the rest is transmitted as transmitted light 50 and reaches the reflecting mirror 52 . At this time, if the angle of incidence on the film 1 is Brewster's angle, there will be no reflected light 40 and only transmitted light 50, and no optical interference will occur.

The light reflected by the reflecting mirror 52 enters the film 1 again, and only the transmitted light 51 passes through the reflecting mirror 6.
0 to the transmitted light/spectroscopy section. Reflection mirror 5
2, a concave mirror is used so that when the incident angle of the first pass with respect to the film 1 is Brewster's angle θB, the other side always becomes θB.

In addition, although the example in Figure 1 is a two-pass multipath system,
As shown in FIG. 2, if a pair of reflecting mirrors 53 and 54 are provided facing each other with the film 1 in between, a four-pass multi-pass system is constructed. In general, it is possible to easily configure an n-bus multipath system depending on the resolution of the transmitted light detection system.

The light incident on the transmitted light/spectroscope unit 6 has a measurement wavelength component λS
and a reference wavelength component λR, the respective light intensities are simultaneously detected using respective detectors, and the measurement wavelength signal and the reference wavelength signal C are input to the signal processing unit 7.

On the other hand, reflected light 40 of the light 23 incident on the film 1
is collected by a condensing mirror 41 and reflected light detector 4
The light is guided to 3. At this time, since the optical axis also fluctuates due to fluctuations in the object to be measured (wavering and fluctuation of the film), the cone mirror 42 is used to prevent detection errors due to optical axis deviation. The reflected light 40 guided to the reflected light detector 43 is converted into an electric signal, that is, a reflected light signal a, and is input to the signal processing section 7.

Next, the specific configuration of each of the above sections will be explained.

As shown in FIG. 3, the light source section 2 includes an infrared generation section 21 and a P-polarized light polarizer 22.
Now, the light from the light source 24 of the halogen lamp is collected by a condensing mirror 25 and condensed by a slit 26. The light passing through the slit 26 is periodically blocked by the chopper 27 and becomes intermittent light.

The intermittent light becomes parallel light by the collimating lens 28 and enters the broadband cut filter 29 . The broadband cut filter 29 passes infrared rays in a band including the measurement wavelength λS, the reference wavelength λR, and a wavelength component used as reflected light, and cuts other wavelength components. The emitted infrared rays 20 enter the polarizer 22. Wire grid type polarizer 22
polarizes this infrared ray 20 into P-polarized light. Note that the polarizer 22 can also be configured to be included in the infrared ray generation section 21.

In correlation with the chopper 27, a chopping detector 27D
is provided. The chopping detector 27D is composed of, for example, a photo ink converter, and outputs a chopping synchronization signal d as an intermittent signal synchronized with intermittent light from the light source.

FIG. 4 shows a schematic configuration of the transmitted light/spectroscopy unit 6.

In the figure, transmitted light 51 that has passed through the film is filtered by a bandpass filter 61 to only infrared rays near the measurement wavelength λS and reference wavelength λR, narrowed down by an entrance slit 62, and then guided to a collimating mirror 63. . The parallel light reflected by the collimating mirror 63 is guided to the diffraction grating 64 and separated into spectra. The spectral light is reflected again by the frimate mirror 63 to form a spectral band on the output slit surface. Spectrum measurement wavelength λ
At the same time, the spectral light 65 with the measurement wavelength λS is emitted through the slit 67 formed at the location corresponding to S, and at the same time, the reference wavelength λ
A spectral light 66 having a reference wavelength λR is emitted through a sulin 68 formed at a location corresponding to R.

The emitted light beams 65 and 66 are sent to respective photodetectors 65D.

The light is received at 66D. From the photodetectors 65D and 66D,
Measurement wavelength signal C according to the intensity of spectral light, reference wavelength signal C
is output. Note that the means for separating the light into the measurement wavelength λS and the reference wavelength λR may be replaced by a prism instead of the diffraction grating 64.

Furthermore, regarding the measurement wavelength and reference wavelength detectors 65D and 66D, those having good sensitivity in the characteristic absorption wavelength region of the film to be measured are used. In an example in which a polyethylene terephthalate film (PET film) is used as film 1, the measurement wavelength is 2440, and the reference wavelength is 240.
It is preferable to use 0+on, in which case 1 to 2.5
PbS, which has good sensitivity in the μm1 band, is used. 2.5
In the case of an object having a characteristic absorption wavelength in the ~3.5 μm band, Pb5e is used.

Furthermore, regarding the reflected light detector 43 (FIG. 1), since the reflected light 40 is generally weaker than the transmitted light 50, it has higher sensitivity than the detectors 65D and 6'6D, and has a wavelength at which the influence of interference can be ignored. It is necessary to have a detection wavelength width (a wavelength shorter than the measurement wavelength is better). For this reason, in the example, a Si7 otodiode is used, and a 700 to 1
The reflected light in the wavelength range of 000r+m is used.

Next, the optical scanning section 3 is illustrated in FIG. The same figure (A), (
B) shows the scanning mechanism of the mirror 30, and FIG. 3C shows the control mechanism for the scanning center.

A cylindrical shaft member 32 is fixed to the center of the lower end of the mirror 30 and supported by a fixed shaft 33 so that the mirror 30 can swing freely around the axis of the shaft 33.

A mirror drive arm 34 for swinging the mirror 30 is connected to the shaft member 32, and a pin 36 is slidably inserted into a long hole 35 at the tip of the arm 34. It is eccentrically fixed to a rotating sector 37 which is a semicircular portion cut out in the circumferential direction.

The rotation sector 37 is rotated in the direction of the arrow in the figure by the synchroch 3 motor 38. When the synchronous motor 38 rotates, the mirror drive arm 34 swings around the axis of the shaft 33, as shown by the dashed line in FIG.
0 also periodically oscillates (vibrates) around its oscillation center.

Correlating with this, the rotating sector 37 is provided with a vibrating mirror synchronization detector 37D composed of a photointerrupter, as clearly shown in FIG.
D outputs a vibrating mirror synchronization signal e which is switched by the edge of the rotating sector 37.

The mirror vibrating section shown in FIGS. 5(A) and 5(B) is fixed to a moving table 39 shown in FIG. 5(C). The movable table 39 is slidably provided on a support base 391, and when a control signal f is input to a pulse motor 393 having a threaded rotating shaft 392, the movable table 39 is controlled to move left and right as shown by arrows in the figure. . When the movable table 39 moves, the entire mirror vibrating section is displaced with respect to the absolutely fixed axis 33, and the center of vibration of the vibrating mirror 30 is controlled. In addition, the moving table 3
9 has a spring 3 on its anti-drive side to prevent backlash.
94 are provided. Further, the vibration and movement mechanism of the mirror 30 is not limited to the one shown in FIG. 5, but may be an electromechanical structure using a strain element such as a piezo element, or an acousto-optic structure using ultrasonic waves. In addition to control accuracy, it has the advantage of compactness.

FIG. 6 shows an external configuration diagram of the film thickness measuring device of the example. 3A is a front view of the film 1 in the width direction, and FIG. 1B is a sectional view taken along the line BB of <A). The film 1 is guided by rollers or guide members (not shown) and runs continuously with some degree of vertical freedom.
Waves sway in the vertical direction.

Reference numeral 101 denotes a scanner frame in which an upper frame 102 above the film 1 and a lower frame 103 below the film 1 are integrally connected. A guide stand 104 extending over the width of the film 1 is installed on the lower frame 103, and a movable stand 105 is connected via a rack and pinion 106 and rails and wheels 107 so as to be able to slide along this guide stand 104. .

The photometry unit 108 is placed on the movable table 105 and includes a light projecting unit 109 in which the light source unit 2 and the light scanning unit 3 described above are constructed.
and the reflected light receiving section 4 and the transmitted light/spectroscopic section 6, which were also mentioned above.
The above-mentioned signal processing section 7 is also built into the photometry section 108. On the other hand, at the lower part of the upper frame 102, a reflective mirror holding frame 1 is provided.
11 are arranged in series, and a reflecting mirror (concave mirror) 52 having a length equal to or longer than the width of the film 1 is held.

The film thickness measuring device of this example is also equipped with an automatic calibration function, and the photo ink club 112 attached to the lower part of the moving table 105 is a detector that generates a timing signal for automatic calibration. The automatic interrupter 112 is provided on one side of the scanner frame 101 and protrudes from the lower frame 103, and generates a signal to the outside when light is blocked by the base plate 113.

Above this base plate 113 is a scanner frame 10.
A standard sample holder 114 is installed so as to extend from the film 1 toward one width edge of the film 1, and a standard sample film made of the same material as the film 1 is held in the standard sample holder 114.

A standard sample film (not shown) is fixed so as to be flush with the specified running surface of the film 1. Further, as can be seen from the figure, a gap 115 is formed between the standard sample holder 114 and the edge of the film 1 in the width direction. This air gap 115 is connected to the measurement wavelength signal (
It is used when calculating a signal correction coefficient from the reference wavelength signal (V(λS)) and the reference wavelength signal (V(λR)).

The movement of the moving table 105 is controlled by a scanner control section 116 attached to the scanner frame 101. Further, the photometry section 108 is connected to a data processing section 117 attached to the scanner frame 101 by a telescopic cable (not shown), and receives a signal from a signal processing section built into the photometry section 108 . An operation panel 118 is formed in the data processing section 117, and includes an arithmetic control means such as a microcomputer or a microprocessor therein.

Note that the data processing section 117 may include the signal processing section described above. The signal processing section will be described in detail below.

Further, in the configuration of FIG. 6, the reflecting mirror 52 is connected to the film 1.
However, if it is difficult to obtain a long concave mirror, a fixed concave mirror having a length equal to or larger than the width of may be configured. In this case, a long concave mirror is unnecessary and a short one can suffice. Functionally, this example uses simultaneous photometry at the same location, so there is no problem even if there is a slight deviation in the optical path.

Next, FIG. 7 shows specific details of the signal processing section 7, which includes a vibrating mirror control circuit 70 and a thickness data calculation circuit 71.

The control circuit 70 for the vibrating mirror includes a differential amplifier 701 to which the reflected light signal a of the reflected light detector 43 is input, a timing generation circuit 702 to which the chopper synchronization signal d of the chopper synchronization detector 27D is input, and a sample hold circuit 703. and 7
04, signal separation circuit 705 and smoothing circuit 706 into which the vibrating mirror synchronization signal e of the vibrating mirror synchronization detector 37D is input
707, a differential amplifier 708, and a drive circuit 709 for the pulse motor 393.
Even if the angle changes, the vibration center of the vibrating mirror 30 is tracked and controlled so that it always maintains the incident angle of Brewster's angle θB.

The principle of follow-up control is illustrated in FIG. As shown in FIG. 2A, when the film 1 to be measured is running on a prescribed running surface, the light is incident at the Brewster angle θB. The incident light 23 is scanned (deflected) in a range of ±Δθ around θB, the intensity of the reflected light 40 is detected, the variation angle ±α of the fluctuating film 1 is detected, and the deflection is reversed to cancel the variation.
This is to control the movement of the vibration center of the vibrating mirror by α. Figure (B) shows the reflected light intensity when the film 1 is on the specified running surface (fluctuation angle 0), when it sways upward (10a), and when it sways downward (-α). A graph is shown in which the incident angle θ is plotted on the horizontal axis. A sine wave sampled around the Brewster angle θB is shown below this graph, and changes in the reflected light intensity at that time are shown in (CI), (C2), and (03), respectively. If this is separated by the positive and negative rectangular waves of the vibrating mirror synchronization signal e, and the DC component of each half cycle is subtracted from the one on the +Δθ side, we can determine how much the object to be measured moves from the reference position. The fluctuation angle ±a of the dolphin is known, and the vibration center of the vibrating mirror 30 is moved in a direction (so as to perform 1,000 angle control) to cancel the fluctuation angle a by the subtracted value (potential difference).

FIG. 9 shows an example of a specific waveform of the vibrating mirror control circuit 70, and its operation will be explained. Note that the alphanumeric characters a, al-a7. in parentheses in FIG. fl, f2 correspond to the signal names in FIG. 7, and (al) to (al) and (fl), (f
Similar to (a), the vertical axis of the graph 2) represents voltage and the horizontal axis represents time.

In FIG. 7, a reflected light signal a inputted from a reflected light detector 43 is processed by a differential amplifier 701 and a sample hold circuit 703 to eliminate background noise (BGM) caused by dark current of the detector and the influence of ambient light. ) is removed to obtain a signal a1 (FIG. 9(al)). The hold timing of the sample hold circuit 703 is based on a timing signal output from the timing generation circuit 702 at an appropriate time during the light-shielding period based on the signal d input from the chopper synchronization detector 27D.

From the output a1 of the differential amplifier 701, only the signal during the light projection period of the signal a1 is taken out by the sample and hold circuit 704 to obtain the signal a2 (FIG. 9(a2), the same applies hereinafter). The hold timing of the sample hold circuit 704 is based on a timing signal output by the timing generation circuit 702 at an appropriate time during the light projection period.

The signal a2 is converted by the signal separation circuit 705 into a half period of the vibration period of the vibrating mirror, that is, on the +Δθ side (signal a3).
and -Δθ side (signal a4). The timing of separation is determined by a vibrating mirror synchronization detector 37. D is the signal e from 6 separated signals a3. a4 are smoothed by smoothing circuits 706 and 707, respectively, and are smoothed as shown in FIG. 9 (as) and (a
It is converted into a flat DC signal as shown in 6).

The signal a5 and the signal a6 are input to the + and - input terminals of the differential amplifier 708, and the differential amplifier 708 outputs a difference signal a7 between the two signals (FIG. 9 (a7)). This difference signal a7 is a signal proportional to the deviation between the incident angle (the angle between the film to be measured and the photometric beam) and the target Brewster angle θB. That is, a positive signal means that the vibration center of the vibrating mirror is located at an incident angle greater than θB, and a negative signal means that the vibration center of the vibrating mirror is at an incident angle smaller than θB. Furthermore, when the center of vibration is θB,
Strictly speaking, the difference signal a7 does not become Ov, but by appropriately adjusting the comparison voltage of the direction discrimination circuit (sign detection circuit) section in the pulse drive circuit 709, it can be corrected to Ov.

The pulse drive circuit 709 outputs a drive signal f to the pulse motor 393 so that the input signal a7 approaches Ov (more precisely, the voltage when the vibration center of the vibrating mirror is at θB).

That is, if the signal is positive, it outputs a signal r1 that moves it in the negative direction, and if it is a negative signal, it outputs a signal f2 that moves it in the positive direction (in the example of the signal in FIG. 9, it moves in the negative direction, so
The pulse signal shown in (fl) is output for a predetermined number of cylinders proportional to the positive signal). By performing the above operation continuously, even if the film 1 to be measured changes in angle, the vibration center of the vibrating mirror 30 always maintains the incident angle of Brewster's angle θB.

In this example, servo control is performed to keep the center of vibration of the vibrating mirror 30 at the incident angle of Brewster's angle θB, but instead of this, the minimum of the reflected light signal a obtained by scanning with the vibrating mirror etc. It is also possible to provide a minimum value detection circuit for detecting the value, and to enable the transmitted light signals S and C at the timing of detecting the minimum value.

Next, the thickness data calculation circuit 71 will be explained.

The circuit 71 includes a background noise removal circuit 711 to which the measurement wavelength signal C of the measurement wavelength detector 65D is input, and a background noise removal circuit 712 to which the reference wavelength signal C of the reference wavelength detector 66D is input. A signal e from the oscillating mirror synchronization detector 37D is inputted to the sample and hold circuits 713 and 714, the timing generation circuit 702 that provides timing signals to the background noise removal circuits 71.1 and 712 and the sample and hold circuits 713 and 714. At the same time, there is a timing generation circuit 715 to which the automatic calibration activation signal 11 output from the automatic calibration detector (photointerrupter) 112 is input, and the outputs of the respective sample hold circuits 713 and 714 are input to the timing generation circuit 715. When the timing signal is input, the outputs of the signal correction coefficient calculation circuit 716, which calculates the ratio of the two human input signals when there is no film, and the sample and hold circuits 713 and 714 are input, and the outputs of the signal correction coefficient calculation circuit 716 are inputted. output is input,
When the other timing signal of the timing generation circuit 715 is input and there is a film, the logarithmic ratio of both external signals is taken.
The status signal 1 generated by the g ratio circuit 717 and the timing generation circuit 715 is input to the log ratio circuit 717.
and an external output circuit 718 that outputs the output of the external data processing section 117 to the external data processing section 117. Timing generation circuit 71
The status signal i of No. 5 is also input to the data processing unit 117 in order to distinguish between the film to be measured and the standard sample data. Note that an electronic cooling control circuit 719 is connected to the measurement wavelength detector 6SD and the reference wavelength detector 66D in order to obtain stable detection signals at all times.

The operation of the thickness data calculation circuit 71 is as follows: First, the transmitted light transmitted through the film 1 to be measured is divided into the measurement wavelength λS and the reference wavelength λ.
The signals S and C obtained by the respective detectors 65D and 66D after being separated into R are sent to the respective background noise removal circuits 7.
11.712, and these circuits 711 and 712 remove noise components such as dark current and disturbance light of the detectors 65D and 66D. The sample and hold circuits 713 and 714 control the film 1 during the light projection period.
Only the signal that passes through is extracted. The outputs of both sample and hold circuits 713 and 714 are always signals generated by the timing generation circuit 702 and sampled at the same timing. In other words, the measurement wavelength signal V (λS) and the reference wavelength signal ■ (λR) always under the same conditions (in the same part of the film to be measured, on the same optical path)
It is.

The timing generation circuit 715 generates the vibrating mirror synchronization signal e and the automatic calibration timing detector 11. ：Using the automatic calibration timing signal 11 from 2, the signal correction coefficient calculation circuit 71
6, the log ratio circuit 717 and the external output circuit 718, and the data processing unit 11
A status signal i is output to 7. Based on the status signal i, the data processing unit 117 identifies whether the thickness data signal g is data of the film to be measured or data of the standard sample. As shown in the timing chart of FIG. 10, the status signal maintains a high level when the photometer 108 (see FIG. 6) is at the standard sample position, and when it moves from that position to the left in the figure, Falling from a high level.

In response to the falling edge, the timing signal generation circuit 715 generates a signal for the signal correction coefficient calculation timing, and the circuit 716
Activate. What is input to the external circuit 716 is
Measurement wavelength signal ■ at a location where the film to be measured does not exist in the measurement optical path (gap 115 in FIG. 6). (λS) and reference wavelength signal■. (λR). Signal correction coefficient calculation circuit 7
16 calculates the ratio of these two signals by 1 based on the timing signal as shown in equation (1).

■. (λR) The determined ratio value is stored in a storage means in the circuit 716 and read out at an appropriate timing to the log ratio circuit 716.
7 is output. In addition, in another configuration, the data processing unit 1
17 may be output.

The log ratio circuit 717 receives a control timing signal from the timing generation circuit 715, that is, a measurement wavelength signal ■θB when there is a fill to be measured or a standard sample in the measurement optical path and the incident angle of the measurement light is the Brewster angle θB. (λ
S) and the reference wavelength signal θB (λR) are received, the ratio of these signals is multiplied by 1 to the correction coefficient read from the circuit 716, and the result is subjected to a logarithmic operation to obtain the thickness data A.
I put it on.

Expressed as a formula, it becomes formula (2).

This circuit 717 linearizes changes in light intensity to changes in thickness. The analog thickness data obtained by the circuit 717 is converted into a digital signal by an external output circuit 718 in synchronization with the control timing of the timing generation circuit 715, and is output to the data processing unit 117 as digital thickness data g. . Particularly, the timing for the standard sample is shown in FIG. Timing for log ratio calculation is determined according to the falling edge of the vibrating mirror synchronization signal, external output timing is determined in accordance with the falling edge of this timing, and the thickness data signal of the standard sample is output. The data processing unit 117 identifies and stores the data as standard sample data based on the high-level status signal i indicating the standard sample period. Standard sample data is obtained by reciprocating the photometer 108 (FIG. 6) at least twice.

The data processing unit 117 calculates the true thickness of the film to be measured. Before measurement, standard sampling 117 (
The standard thickness of the film set in Figure 6 (A))
is input to the data processing unit 117 from the operation panel 118. Standard thickness d. Then, the actual measurement data signal g from the photometry unit 108 is read at the timing when the status signal i indicates that it is at the standard sample position (the value is assumed to be A), and the ratio is calculated as shown in equation (3). It is used as the thickness conversion coefficient when measuring the actual film thickness.

d.

K2=−・・・・・・(3) A.

Using 2 as this coefficient, thickness calculation is continuously performed during one or more reciprocations thereafter. Assuming that the actual thickness data is A, the following equation (4) is calculated.

d = 2XA (4) The film thickness value d obtained by calculating the above equation (4) can be output to a desired output device, such as a chart recorder, printer, CRT, etc. . In addition, the output contents include display of the profile of the object to be measured in the flow direction and width direction, and the thickness d set from the operation panel. (For example, if the thickness is 2 μm, ±0.5μ “1
(in the event that the value deviates from the range), an alarm may be sounded to warn the user, or the film may be used as a thickness control signal for film manufacturing equipment.

Note that the data processing unit 117 according to the above embodiment has a standard thickness d. Input the actual measurement data A0 of the standard sample to calculate the thickness of subsequent actual measurements using the thickness conversion coefficient of 2. However, the actual measurement data A0 of the standard sample
. The result is that the true thickness can be quantified without compromising the standard sample (eliminating all equipment related to the standard sample). In other words, the number of passes of the film is determined by the configuration of the multipass system.
Since the absorbance of the film is also known in advance, the true film thickness d is the measured and output thickness data A.

It corresponds uniquely to . Therefore, a function (continuous quantity or discrete quantity as plotted) is set up to quantify the true thickness of the film using thickness data A as a variable, and a storage means (preferably ROM) in which this function is stored is stored as data. The processing section 117 is prepared for this purpose. When the type of film is different, for example, the ROM may be replaced as appropriate depending on the type of film. This can be achieved by providing versatility to the device through simple means.

[Effects] As described in detail above, according to the infrared thickness meter according to the present invention, by making P-polarized light incident at the Brewster angle, optical interference caused by ultra-thin films can be reduced by making ultra-thin films. However, by accurately measuring the film thickness, a multi-pass optical system can be used to overcome the lack of resolution in the detection system for the transmitted light of ultra-thin films, and at the same time, it is possible to eliminate measurement errors caused by fluctuations in the object to be measured using the reflected light. By detecting the minimum, it can be controlled and effectively prevented. Furthermore, because the photometry was carried out simultaneously at the same location, both errors due to optical axis fluctuations when scanning the photometer and errors due to differences in photometering parts in conventional three-wavelength time-division photometry for objects traveling at high speed are generated. It never gets wet. When the automatic calibration means is also used, it is possible to effectively prevent errors due to changes over time that depend on the wavelength characteristics of the optical system including the light source and the detector.

By the way, the object to be measured is a 4.0 μm (7) PET film, the measurement wavelength is λ5=2440++m, λR=2400
nm, reflected light detection wavelength range 700 to 11000n, mirror vibration frequency 25Hz, mirror vibration angle ±3゛,
In the above-mentioned infrared thickness meter with a chopping frequency of IKHz and two passes of transmitted light, the vibration center setting angle was 58 degrees, and the measurement accuracy was ±0.1 microbeats.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram of an embodiment according to the present invention, Fig. 2 is an optical path diagram showing another example of a multi-pass optical system, Fig. 3 is a detailed view of the light source section, and Fig. 4 is a transmitted light/spectroscopic diagram. FIG. 5 is a detailed view of the optical scanning section, FIG. 5 is a plan view, FIG. 5B is a side view, and FIG. 5C is a perspective view of the moving table. FIG. 6 shows an external configuration diagram of the embodiment (A> is a front view,
(B) is a sectional view taken along the line B-B of (A). Fig. 7 is a 70 circuit diagram of the signal processing section, Fig. 8 (A), (B),
(CI), (C2), and (C3) are explanatory diagrams of the principle of servo control of the optical scanning section, and FIGS. 9(a), (al), and (a) respectively.
2), (a3). (a4), (a5), (a6), (a7), (fl) and (r2) are waveform diagrams showing examples of waveforms of each part of the vibrating mirror control circuit. FIG. DESCRIPTION OF SYMBOLS 1... Film, 2... Light source part, 3... Light scanning part, 4... Reflected light receiving part, 5... Optical path conversion part, 6...
- Transmitted light/spectroscopy unit, 7... Signal processing unit, 20... Infrared light, 22... Polarizer for P polarization, θB... Brewster angle, 40... Reflected light, 51... Transmitted light. Patent applicant: Kurashiki Boseki Co., Ltd. Representative: Patent attorney: Two idiots Figure 1. Figure 2 21! ! Figure 4 6

Claims (10)

[Claims] (1) A light source that intermittently generates infrared rays in a band that includes at least two wavelength components: a wavelength component that exhibits absorption characteristics unique to the film and a wavelength component that exhibits non-absorption characteristics, and includes a polarizer that polarizes this infrared rays into P-polarized light. and projecting infrared rays output from the light source section from an oblique direction at a predetermined angle with respect to the film surface of the film, and continuously varying the infrared rays within a predetermined angular range around the projection angle. a light scanning unit configured to scan the infrared rays on the film; a reflected light receiving unit configured to receive reflected infrared light projected onto the film and output a reflected light signal according to the received light intensity; a transmitted light spectrometer that receives transmitted infrared light projected onto the infrared rays, separates it into at least the above two wavelength components, and outputs a transmitted light signal according to the received intensity of each of the spectral lights; receives the transmitted light signal, removes the background noise of the reflected light signal and the transmitted light signal, identifies the reflected light signal, and enables the transmitted light signal at the minimum reflected light intensity; An infrared thickness meter comprising: a signal processing section that calculates thickness data that is a basis for quantifying the thickness of a film based on the transmitted light signal of at least the above three wavelength components. (2) The infrared thickness gauge according to claim (1), wherein the polarizer is disposed in the optical path between the optical scanning section and the film surface. (3) A light source that intermittently generates infrared rays in a band that includes at least two wavelength components: a wavelength component that exhibits absorption characteristics unique to the film and a wavelength component that exhibits non-absorption characteristics, and includes a polarizer that polarizes this infrared rays into P-polarized light. and projecting infrared rays output from the light source section from an oblique direction at a predetermined angle with respect to the film surface of the film, and continuously varying the infrared rays within a predetermined angular range around the projection angle. a light scanning unit configured to scan the infrared rays on the film; a reflected light receiving unit configured to receive reflected infrared light projected onto the film and output a reflected light signal according to the received light intensity; The optical path of the transmitted light is changed so that the infrared rays projected onto the film pass through the film multiple times, and the absorption ability of the boyfriend component exhibiting absorption characteristics unique to the film is enhanced among the infrared rays transmitted through the film. a transmitted light spectrometer that receives the transmitted infrared light projected onto the film, separates it into at least the above two wavelength components, and outputs a transmitted light signal according to the received intensity of each of the spectral lights. a part that receives the reflected light signal and the transmitted light signal, removes background noise from the reflected light signal and the transmitted light signal, respectively, identifies the reflected light signal, and detects the transmitted light signal at the minimum reflected light intensity. An infrared ray thickness sensor comprising: a signal processing section that activates an optical signal and calculates thickness data that is a basis for quantifying the thickness of the film based on the activated transmitted optical signal of at least the three wavelength components. Total. (4) A light source that intermittently generates infrared rays in a band that includes at least two wavelength components: a wavelength component that exhibits absorption characteristics unique to the film and a wavelength component that exhibits non-absorption characteristics, and includes a polarizer that polarizes this infrared rays into P-polarized light. and projecting the infrared rays output from the light source section obliquely at a predetermined angle to the film running surface of the traveling film, and continuously within a predetermined angular range around the projecting angle. a light scanning unit configured to vary the infrared rays so that they scan the film; a reflected light receiving unit that receives reflected infrared light projected onto the film and outputs a reflected light signal according to the received light intensity; a light scanning control section that automatically corrects the set projection angle according to vibrations caused by the running of the film based on the reflected light signal; a transmitted light spectrometer that separates the light into two wavelength components and outputs a transmitted light signal according to the received intensity of each of the spectral lights, and receives the reflected light signal and the transmitted light signal, and removing the background noise of each of the transmitted light signals, identifying the reflected light signal and activating the transmitted light signal at the minimum reflected light intensity, and based on the activated transmitted light signal of at least the three wavelength components; An infrared thickness meter characterized by comprising a signal processing section that calculates thickness data that is the basis for quantifying the thickness of a film. (5) The infrared thickness gauge according to claim (4), wherein the optical scanning section includes a vibrating mirror, and the setting projection angle in the optical scanning control section is corrected by servo control. (6) A light source that intermittently generates infrared rays in a band that includes at least two wavelength components: a wavelength component that exhibits absorption characteristics unique to the film and a wavelength component that exhibits non-absorption characteristics, and includes a polarizer that polarizes this infrared rays into P-polarized light. and projecting the infrared rays output from the light source section obliquely at a predetermined angle to the film running surface of the traveling film, and continuously within a predetermined angular range around the projecting angle. a light scanning unit configured to vary the infrared rays so that they scan the film; a reflected light receiving unit that receives reflected infrared light projected onto the film and outputs a reflected light signal according to the received light intensity; a transmitted light spectrometer that receives the transmitted infrared light projected onto the film, separates it into at least the two wavelength components, and outputs a transmitted light signal according to the received intensity of each of the spectral lights, and the reflected light receiving the signal and the transmitted light signal, removing background noise of the reflected light signal and the transmitted light signal, respectively, and identifying the reflected light signal to enable the transmitted light signal at the minimum reflected light intensity; a signal processing unit that calculates thickness data that is a basis for quantifying the thickness of the film based on the activated transmitted light signal of at least the two wavelength components; and the thickness data output from the signal processing unit and the true value of the film. An infrared thickness meter comprising: a predetermined thickness conversion function for quantifying the thickness of the film; and a data processing section that calculates the thickness of the film based on the predetermined thickness conversion function. (7) The light source section, the light scanning section, the reflected light receiving section, and the transmitted light spectroscopic section are integrally constructed, and this integral structure is movable in the width direction of the film (
6) Infrared thickness gauge described in section 6). (8) A sample film of the same type as the film is fixed on the same plane as the film running surface on the outside in the width direction of the running film, and the integrated structure is movable to the fixed sample film position. An infrared thickness gauge according to claim (7). (9) The infrared thickness meter according to claim (8), wherein the thickness data is automatically calibrated based on a transmitted light signal from the fixed sample film. (10) The data processing section includes a storage means that stores a thickness conversion function capable of uniquely quantifying the true thickness of the film using the thickness data output from the signal processing section as a variable. The infrared thickness gauge described in item (6).