JP7199945B2 - optical measuring device - Google Patents

Description

The present invention relates to an optical measuring device for measuring components such as moisture content, thickness, coating amount, etc. of paper, sheets, films, etc., which are conveyed on a production line.

For example, in a production line such as a factory, the traverse system is one of the methods for extensively measuring the components to be measured (e.g., moisture content, thickness, coating amount, etc. of paper, sheets, films, etc.) transported on the line. has traditionally been used.

In the traverse system, a wide range of components can be measured by moving the measuring device over the object to be measured at a predetermined speed in a direction orthogonal to the direction in which the object is conveyed.

Conventionally, as a measuring device employing this type of traverse system, for example, a measuring device disclosed in Patent Document 1 below is known. In the measuring apparatus disclosed in Patent Document 1, a laminate film is the object to be measured, and a non-contact thickness detection sensor is reciprocated at a constant speed over a width wider than the laminate film in the width direction of the conveyed laminate film. Thereby, the thickness of the laminate film in the width direction is measured by scanning the non-contact thickness sensor by zigzag traversing in the oblique direction of the laminate film.

JP 2003-181905 A

The traverse system, as shown in FIG. 6, performs measurement by scanning the measuring object W in the width direction with the measuring machine 21 . Since the purpose is to measure the component distribution in the width direction of the object W to be measured, the measurement range is from end to end in the width direction of the object W to be measured. When the film of the object W to be measured is fed, the object W to be measured moves during scanning, and the measurement area (the area surrounded by a circle in FIG. 6) changes from the width direction to the oblique direction as indicated by the dotted line. If the measurement area is slanted, a non-measurable area (a hatched area in FIG. 6) occurs, and if there is a large difference between the traverse speed and the film feeding speed, the non-measurable area increases. Also, even if the film feeding speed increases, the traverse system continues to scan the film from end to end in the width direction, so the measurement range does not change and only the non-measurable region increases.

As described above, in the conventional measuring device that employs the traverse system disclosed in the above-mentioned Patent Document 1, the measuring device (non-contact thickness sensor) traverses in a zigzag direction and scans the oblique direction of the object to be measured. Therefore, it was not possible to simultaneously measure a plurality of points in the direction perpendicular to the conveying direction of the object to be measured. Moreover, if there is a large difference between the feed speed for conveying the object to be measured and the moving speed of the measuring machine of the traverse system, there is a problem that the non-measurable area becomes large.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an optical measuring apparatus capable of measuring an object over a wide range by reducing the non-measurable area.

In order to achieve the above object, an optical measuring device according to claim 1 of the present invention is an optical measuring device for measuring a component of a measurement object transported at a predetermined speed or at a predetermined interval,
a light source unit that irradiates the object to be measured with light having a plurality of different wavelengths including the wavelength of the absorption peak of the object to be measured;
It is composed of a plurality of lenses arranged on the side of the object to be measured . a first lens that collects light with a plurality of lenses;
A plurality of bandpass filters that disperse the light condensed by the first lens into light of a plurality of different wavelengths including the wavelength of the absorption peak of the measurement target;
one line sensor that simultaneously detects the lights of the different wavelengths separated by the band-pass filter;
A plurality of filters are arranged between the first lens and the band-pass filter, and the light collected by the first lens is transferred to the band-pass filter so that a plurality of images do not overlap each other on the detection surface of the line sensor. a second lens that simultaneously forms an image on the detection surface of the line sensor via a filter;
a storage unit that stores a calibration curve showing the relationship between the component of the standard substance for each measurement object and the measured value;
A measurement unit that measures the components of each wavelength at the plurality of positions based on the measurement values of the light detected by the line sensor by splitting the light into the plurality of different wavelengths and the calibration curve stored in the storage unit. and

The optical measuring device according to claim 2 is characterized by using a mirror instead of the first lens.

The optical measuring device according to claim 3 is the optical measuring device according to claim 1 or 2 ,
The light source unit is a light source in which a plurality of rod-shaped light sources, lamps, or LEDs are arranged.

The optical measuring device according to claim 4 is the optical measuring device according to claim 3 ,
The light source unit is characterized by comprising a diffusion plate for uniformizing the irradiation surface.

The optical measuring device according to claim 5 is the optical measuring device according to claim 4 ,
The light source unit is characterized by comprising a reflector with a high reflectance for efficiently applying light to the irradiation surface.

According to the present invention, it is possible to simultaneously measure the components at a plurality of locations in the direction perpendicular to the conveying direction of the object to be measured. As a result, the non-measurable area can be reduced compared to the conventional traverse system, and a wider range of measurement can be performed.

(a) A diagram showing a schematic configuration of an optical measuring device according to the present invention, (b) a schematic cross-sectional view of a light source section. FIG. 4 is a schematic view of measuring reflected light with the optical measuring device according to the present invention; FIG. 5 is a schematic perspective view showing another configuration of the detection section of the optical measuring device according to the present invention; It is a figure which shows an example of the calibration curve used for the optical measuring apparatus which concerns on this invention. It is a figure which shows the optical spectrum of a polyethylene film. FIG. 4 is an explanatory diagram of a measurement outline of the traverse system;

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated in detail, referring attached drawings.

[Overview of the present invention]
Objects are known to have characteristic absorption peaks at specific wavelengths. FIG. 5 shows the spectra measured when the polyethylene film had a thickness of 50 μm and when it had a thickness of 100 μm. In FIG. 5, the horizontal axis is wavelength and the vertical axis is absorbance.

Here, the absorbance is a dimensionless quantity that indicates how much the intensity of light is weakened when light passes through a certain object in spectroscopy. For example, polyethylene film has one peak at 2300 nm. This indicates that the polyethylene film absorbs and attenuates light with a wavelength of 2300 nm. Further, as shown in FIG. 5, the absorbance when the polyethylene film has a thickness of 100 μm is double the value when the polyethylene film has a thickness of 50 μm. It can be seen from this that the absorbance increases in proportion to the concentration and the optical path length.

Here, if a calibration curve showing the relationship between the component (e.g., thickness, concentration, etc.) of the reference substance to be measured and the absorbance is used, the component (e.g., thickness, concentration, etc.) can be determined by measuring the absorbance. can be measured.

In addition, as a reference wavelength, a wavelength (e.g., 2100 nm) that is close to the absorption peak of the measurement target and has no absorption of the target component is simultaneously measured and calculated, thereby correcting intensity changes due to factors other than the absorption peak of the measurement target. can be used, and the measurement accuracy is improved.

Therefore, in the present invention, for example, a single line sensor corresponding to a wavelength of 900 to 2550 nm is provided with a compound-eye optical system in which a plurality of lenses and band-pass filters are attached. can be measured simultaneously.

[Regarding the configuration of the optical measuring device]
The optical measuring device according to the present invention is preferably employed in a production line such as a factory, for example, and measures paper, sheets, films, etc. transported on the line at a predetermined speed / predetermined interval, and measures moisture, thickness, It has a function to measure components such as coating amount over a wide range.

As shown in FIG. 1(a), the optical measuring apparatus 1 of this embodiment includes a light source unit 2, a detection unit 3, a storage unit 4, a measurement unit 5, and a display unit 6 in order to realize the functions described above. It is roughly configured with

As shown in FIGS. 1(a) and 1(b), the light source unit 2 includes a light source 2a that linearly irradiates light having a plurality of different wavelengths including the absorption peak wavelength to the measurement object W. It consists of a linear light source unit. A bar-shaped halogen heater, for example, is used for the light source unit 2 . A diffusion member including a light diffusion plate 2b for suppressing unevenness in the amount of light is arranged on the irradiation surface of the light source unit 2 facing the object W to be measured. Further, in the light source section 2, a reflector 2c for efficiently applying light to the irradiation surface is arranged on the opposite side of the light diffusion plate 2b with the light source interposed therebetween. As the light source unit 2, a light source in which a plurality of rod-shaped light sources, lamps, or LEDs (light emitting diodes) are arranged can be used.

The light source unit 2 is installed on one side or both sides so as to illuminate the measurement area as shown in FIG. 2 when measuring reflected light with the optical measurement device 1 . FIG. 2 illustrates the case where the light source units 2 are installed on both sides of the measurement area.

The detection unit 3 detects light from a plurality of positions P1, P2, . , and includes an optical lens 11 , a bandpass filter 12 and a line sensor 13 . In the following, two wavelengths, ie, the measurement wavelength λ1 at the absorption peak of the object W to be measured and the reference wavelength λ2 close to the absorption peak of the object W to be measured, will be described as an example of a plurality of different wavelengths.

The optical lens 11 forms an image of the light from the object W to be measured on the detection surface of the line sensor 13, and is composed of a first lens 11A and a second lens 11B. In addition, in FIG. 1, the first lens 11A and the second lens 11B are simply represented by one lens.

The first lens 11A is arranged on the measurement object W side and is composed of one or more lenses. In order to widen the field of view for measurement and to form an image without aberration, the first lens 11A is constructed by using a plurality of groups of doublet lenses, for example, a combination of one convex lens and one concave lens. preferable. As shown in FIG. 1, the first lens 11A has a plurality of positions P1, P2, . collects light from

Like the first lens 11A, the second lens 11B is composed of one or more lenses. In order to form an image without aberration, the second lens 11B is constructed by using a plurality of groups of doublet lenses similar to the first lens 11A, which is a combination of one convex lens and one concave lens. is preferred. A plurality of second lenses 11B (two in the example of FIG. 1) are arranged between the first lens 11A and the bandpass filter 12. Light from a plurality of positions P1, P2, .

A triplet lens in which one convex lens is sandwiched between two concave lenses can also be used as the second lens 11B. Although FIG. 1 illustrates a case where there are two second lenses 11B, if the number of the second lenses 11B and the bandpass filters 12 is increased, the wavelengths can be divided by the number of the second lenses 11B and the bandpass filters 12. can be measured. Furthermore, if the field of view for measurement is sufficient, the first lens 11A may be omitted.

Further, as shown in FIG. 3, the first lens 11A used to widen the viewing angle in the detection section 3 can be replaced with two mirrors 11C and 11D. In FIG. 3, the first mirror 11C is, for example, a convex mirror, collects the light emitted from the light source unit 2 and transmitted or reflected by the object W to be measured, converts it into parallel light, and guides it to the second mirror 11D. The second mirror 11D is, for example, a plane mirror, and guides parallel light to the second lens 11B.

Although FIG. 3 shows an example in which a convex mirror is used as the first mirror 11C and a plane mirror is used as the second mirror 11D, a spherical mirror or a parabolic mirror may be used. In addition, although FIG. 3 shows an example in which two mirrors are used instead of the first lens 11A, the number of mirrors may be one or three or more, and a system combining the first lens 11A and mirrors may also be used.

The bandpass filter 12 is arranged between the optical lens 11 and the line sensor 13, and the light from a plurality of positions P1, P2, . is divided into a measurement wavelength λ1 and a reference wavelength λ2 and passed.

The line sensor 13 is arranged after the bandpass filter 12, and simultaneously receives light from a plurality of positions P1, P2, . To detect. The line sensor 13 corresponds to near-infrared light wavelengths of, for example, 900 to 2550 nm, and is used by dividing the light receiving region by the number of wavelengths to be measured. Here, since the number of wavelengths to be measured is two (measurement wavelength λ1, reference wavelength λ2), the light receiving area is divided into two, and the optical lens 11 (first lens 11A , second lens 11B) and the light of the measurement wavelength .lambda.1 and the light of the reference wavelength .lambda.2 that have passed through the band-pass filter 12 are simultaneously detected.

The storage unit 4 stores a calibration curve for each object W to be measured. The calibration curve is based on the components of the standard substance for each measurement target W, for which the measured values (for example, the absorbance ratio to the concentration indicated by the black circles in FIG. 4) are known in advance for the components (for example, moisture, thickness, coating amount, etc.). It is a linear approximation of the relationship with the measured value. In addition to the absorbance ratio described above, the measured values include light intensity, transmittance, reflectance, and the like.

The measurement unit 5 calculates the ratio R (=I1/I2) of the intensities I1 and I2 of the light having the measurement wavelength λ1 and the reference wavelength λ2 from the plurality of positions P1, P2, . Based on the calibration curve stored in the storage unit 4, the components (for example, water content, thickness, coating amount, etc.) at a plurality of positions P1, P2, . . . , Pn are measured. That is, the measurement unit 5 stores components (for example, thickness, concentration, etc.) corresponding to the ratio R of the light intensities I1 and I2 of the measurement wavelength λ1 and the reference wavelength λ2 from the plurality of positions P1, P2, . . . , Pn. It is calculated from the calibration curve stored in the unit 4.

Although the ratio R of the light intensities I1 and I2 is calculated in this example, the ratio of transmittance or absorbance may be calculated. , Pn of the object W to be measured are associated with the pixels of the line sensor 13, and the amount of components and the position information are linked, the measurement unit 5 can obtain the measurement wavelength λ1 and the reference wavelength The intensity of light at λ2, or transmittance, absorbance, reflectance, etc., can be measured simultaneously.

The display unit 6 is composed of a display device such as liquid crystal or EL, and displays the component distribution of the measurement object W measured by the measurement unit 5 as a measurement result on a display screen.

Next, a method of measuring components (for example, thickness and concentration) of the object W to be measured using the optical measuring apparatus 1 configured as described above will be described.

From a plurality of positions P1, P2, . is detected by the detector 3 .

That is, in the detection unit 3, the first lens 11A of the optical lens 11 collects light from a plurality of positions P1, P2, . The light is divided into the measurement wavelength λ1 and the reference wavelength λ2, and images are simultaneously formed on the detection surface of the line sensor 13 by the two second lenses 11B.

For example, focusing on the light from the position P1 of the object W to be measured in FIG. The pass filter 12 separates the light into the measurement wavelength λ1 and the reference wavelength λ2, which are simultaneously imaged on the detection surface of the line sensor 13 by the two second lenses 11B. The same applies to light from other positions P2, . . . , Pn. be done.

Then, the measurement unit 5 uses the calibration curve stored in the storage unit 4 to reference the components of the plurality of positions P1, P2, . A ratio R (=I1/I2) between the intensities I1 and I2 of the light of wavelength λ2 is measured. At this time, positional information of a plurality of positions P1, P2, . At the same time, the component distribution determined by the ratio R is measured. By taking the ratio R between the light intensities of the measurement wavelength λ1 and the reference wavelength λ2, it is possible to correct the intensity change due to factors other than the absorption of the object W to be measured and improve the measurement accuracy. Although the light intensity ratio R is calculated here, the transmittance or absorbance ratio may be calculated.

By the way, in the above-described embodiment, the configuration corresponding to only two wavelengths, ie, the measurement wavelength λ1 and the reference wavelength λ2 has been described as an example. can be set up and configured. Further, the line sensor 13 is not limited to one that corresponds to near-infrared light, and may be one that corresponds to other wavelength regions (for example, ultraviolet light, visible light, etc.).

As described above, according to the present embodiment, when measuring the components of the measurement target, it is possible to simultaneously measure the components at a plurality of locations on the surface of the measurement target in the width direction perpendicular to the transport direction of the measurement target. As a result, it is possible to perform measurements at a higher speed than the conventional traverse system, to make the unmeasurable area extremely small, and to perform measurements over a wider range.

Although the best mode of the optical measuring device according to the present invention has been described above, the present invention is not limited by the description and drawings according to this mode. In other words, other forms, embodiments, operation techniques, etc. made by those skilled in the art based on this form are all included in the scope of the present invention.

REFERENCE SIGNS LIST 1 optical measuring device 2 light source unit 2a light diffusion plate 2b reflector 3 detection unit 4 storage unit 5 measurement unit 6 display unit 11 optical lens 11A first lens 11B second lens 11C first mirror 11D second mirror 12 bandpass filter 13 line sensor 21 measuring machine W measurement object

Claims (5)

An optical measuring device for measuring a component to be measured that is conveyed at a predetermined speed or at a predetermined interval,
a light source unit that irradiates the object to be measured with light having a plurality of different wavelengths including the wavelength of the absorption peak of the object to be measured;
It is composed of a plurality of lenses arranged on the side of the object to be measured . a first lens that collects light with a plurality of lenses;
A plurality of bandpass filters that disperse the light condensed by the first lens into light of a plurality of different wavelengths including the wavelength of the absorption peak of the measurement target;
one line sensor that simultaneously detects the lights of the different wavelengths separated by the band-pass filter;
A plurality of filters are arranged between the first lens and the band-pass filter, and the light collected by the first lens is transferred to the band-pass filter so that a plurality of images do not overlap each other on the detection surface of the line sensor. a second lens that simultaneously forms an image on the detection surface of the line sensor via a filter;
a storage unit that stores a calibration curve showing the relationship between the component of the standard substance for each measurement object and the measured value;
A measurement unit that measures the components of each wavelength at the plurality of positions based on the measurement values of the light detected by the line sensor by splitting the light into the plurality of different wavelengths and the calibration curve stored in the storage unit. An optical measuring device comprising: 2. An optical measuring device according to claim 1 , wherein a mirror is used in place of said first lens. 3. The optical measuring apparatus according to claim 1, wherein the light source unit is a light source in which a plurality of rod-shaped light sources, lamps, or LEDs are arranged. 4. The optical measuring device according to claim 3 , wherein the light source unit has a diffuser plate for making the irradiation surface uniform. 5. The optical measuring apparatus according to claim 4 , wherein said light source unit has a reflector with a high reflectance for efficiently applying light to said irradiation surface.

Images