JP5082552B2 - Optical measuring apparatus and optical measuring method - Google Patents

Description

  The present invention relates to an optical measurement apparatus and an optical measurement method for continuously measuring the surface state of a measurement object to be conveyed.

  2. Description of the Related Art Conventionally, there is known an optical measuring device that detects and inspects defects and foreign matters on the surface of a transparent glass substrate or a smooth plate material.

  This optical measurement device irradiates the surface of a measurement object with a laser beam obliquely from above, guides scattered light from the foreign matter adhering to the surface to the light receiving element by the imaging optical system, and detects the presence of foreign matter from the light receiving element output. It is something to detect.

As such an optical measuring device, the surface of a transparent measuring object is irradiated with laser light obliquely from above, and each scattered light from the front surface and the back surface is guided to two different line sensors by an imaging optical system, A device that performs front / back determination processing from two sensor outputs and generates front surface data and back surface data is known (see, for example, Patent Document 1).
JP 2004-37400 A

  However, when the scattered light is collected and received by a light receiving unit using a normal imaging optical system and a line sensor as the condensing optical system as in the above-mentioned Patent Document 1, there are the following problems. .

  FIG. 9 is a diagram showing a problem of the conventional optical measuring apparatus.

  In the figure, 100 is an object to be measured, 200 is a normal imaging optical system having a magnification m, and 300 is a line sensor. In the line sensor 300, individual sensors are arranged one-dimensionally in the front and back direction of the drawing. When the measurement object 100 having a smooth surface at the position indicated by the solid line is irradiated with the laser beam at the incident angle θ, it is reflected in the direction indicated by the arrow when there is no foreign object. At this time, if there is a foreign substance, the scattered light is guided by the imaging optical system 200 and imaged on the line sensor 300, and the presence of the foreign substance can be detected.

  On the other hand, when the measuring object 100 is displaced by d and displaced to the position 100 ′ indicated by the broken line, the laser beam is irradiated to the position displaced by d · tan θ. The scattered light of the foreign matter at the shifted irradiation position forms an image at a position shifted by m · d · tan θ from the center of the line sensor 300 in the direction orthogonal to the line by the imaging optical system 200. Therefore, there is a problem that accurate foreign object detection cannot be performed.

  In other words, in the conventional optical measuring apparatus, if the distance between the object to be measured and the imaging optical system varies, the position where the laser beam is irradiated is displaced, thereby causing the imaging position and the connection of the scattered light from the foreign matter. The image state also changes sensitively and causes an error in the detection result. Even if an area sensor is used for the light receiving unit, light can be received, but the image formation state changes, resulting in a blurred image, the detection sensitivity decreases, and an error occurs in the detection result. This problem is a serious problem when the object to be measured is soft and flexible, such as a resin sheet, and the localization of the measurement area becomes more difficult.

  In addition, in the case of a normal imaging optical system, if the magnification of the imaging optical system is high, the resolution can be increased, but the length of the measurement area is shorter than the length of the line sensor, and the measurement time is increased. It will be necessary. On the other hand, if the magnification of the imaging optical system is low, the length of the line sensor may be shorter than the length of the non-measuring region, but there is a problem that the light collecting power and resolution are lowered and sufficient detection power cannot be obtained. .

  In view of the above problems, the present invention can accurately detect the presence of a foreign object even if the distance between the object to be measured and the imaging optical system varies, and makes the measurement area sufficiently long even if the light receiving part is small. An object of the present invention is to provide an optical measuring device that can be used.

  The above object is achieved by the invention described below.

1. A light irradiating unit for irradiating a region to be measured on the surface of the measurement object to be conveyed; a condensing optical system for condensing the scattered light on the surface of the measurement object; and in optical measuring device having a light receiving portion for receiving the scattered light Te, the measurement object is curved, the laser beam so as to irradiate the tangential direction of the measurement target, the light converging optical system A first lens having a curved cross section in the transport direction of the measurement object; and a second lens having a curved cross section perpendicular to the transport direction; and When the second lens is disposed on the side close to the light receiving unit, and the distance between the measurement target region of the measurement target and the light receiving unit is L, The focal length in the cross section in the transport direction of the measurement object is L / 4, Optical measuring apparatus characterized in that the focal length at the cross section perpendicular to the feeding direction L / 2, and.

  2. 2. The optical measurement apparatus according to 1, wherein the measurement object is curved along the outer shape of a cylindrical roller.

  3. The optical measurement apparatus according to 1 or 2, wherein the laser beam is narrowed to be thinner than the thickness of the measurement object in the measurement area.

4 . The optical measurement apparatus according to any one of claims 1 to 3 , wherein the light irradiation unit is a scanning optical system, and the light receiving unit is configured by a single light receiving element.

5 . In optical measuring method using the optical measurement apparatus according to any one of 1 to 4, it is curved the measurement object having flexibility, to actuate the light irradiation portion, the curved portion of the measurement object of irradiating the tangentially the laser beam, the light focusing the scattered light from the surface of the object by the optical system collects light, it receives the condensed the scattered light by the light receiving unit, As a An optical measurement method, wherein the state of the surface of the measurement object is determined based on the amount of light.

  According to the present invention, even if the distance between the object to be measured and the imaging optical system varies, the presence of a foreign object can be accurately detected, and the measurement area can be made sufficiently long even if the light receiving portion is small. It is possible to provide an automatic measuring device.

  Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited thereto.

  FIG. 1 is a block diagram showing an overall schematic configuration of an optical measuring apparatus 1 according to the present embodiment.

  As shown in FIG. 1, the optical measuring apparatus 1 includes a light irradiation unit 10 that irradiates light to the measurement object 100, a conveyance unit 110 that includes, for example, a motor that conveys the measurement object 100, and the measurement object 100. Encoder 120 for feeding back the transport amount by the transport unit 110 to the control unit 60, the condensing optical system 20 for condensing the scattered light from the foreign matter on the measurement object 100, and the light collected by the condensing optical system 20 A light receiving unit 30 that receives light, an A / D conversion unit 40 that converts an analog output from the light receiving unit 30 into digital data, and a determination unit 50 that determines the presence of foreign matter from the A / D converted data. The display unit 70 displays the obtained results.

  The control unit 60 includes a ROM storing a predetermined operation program and a RAM as a work area, and includes a light irradiation unit 10, a transport unit 110, a light receiving unit 30, an A / D conversion unit 40, a determination unit 50, and a display unit 70. It comes to control. The control unit 60 and the determination unit 50 are preferably configured using a personal computer.

(First embodiment)
FIG. 2 is a perspective view showing an optical configuration of the optical measuring apparatus 1 according to the first embodiment. In addition, in the following figures, in order to avoid duplication of description, the same reference numerals are given to the same function members.

  As shown in the figure, the measuring object 100 is a long sheet material having flexibility, and is conveyed in the direction indicated by the arrows by conveying rollers 111, 112, 113, and the like.

  The light irradiation unit 10 includes a semiconductor laser 11 that oscillates a laser beam as a light source, and cylindrical lenses 12, 13, and 14 disposed in front of the semiconductor laser 11. By the cylindrical lenses 12, 13, and 14, the light beam from the semiconductor laser 11 is expanded in parallel with the width H in the drawing, and is condensed so as to be thinner than the thickness of the measurement object 100 in the thickness direction of the measurement object 100. ing. At least one of the cylindrical lenses 12, 13, and 14 is preferably formed as an aspherical surface. The light source is preferably a semiconductor laser that can be miniaturized, but other laser light sources such as a gas laser and a dye laser may also be used.

  The region to be measured is a position indicated by a one-dot chain line on the surface of the measurement target object 100 of the sheet material curved along the conveying roller 112, and the light beam from the semiconductor laser 11 is a curved portion of the measurement target object 100 as illustrated. It is laid out so that it is irradiated from the tangential direction.

  The condensing optical system 20 has cylindrical lenses 21 and 22 facing a measurement region indicated by a one-dot chain line. The cylindrical lens 21 disposed on the side close to the measurement object 100 is a lens having a curved cross section in the conveyance direction of the sheet material that is the measurement object 100. The cylindrical lens 22 disposed on the side close to the light receiving unit 30 is a lens in which a cross section perpendicular to the sheet material conveyance direction is formed into a curved surface.

  That is, the cylindrical lens 21 has a refractive power in the conveyance direction of the measurement object 100, and the cylindrical lens 22 has a refractive power in a direction orthogonal to the conveyance direction. Furthermore, the cylindrical lens 21 and the cylindrical lens 22 of the condensing optical system 20 have different refractive powers. At least one surface of the cylindrical lenses 21 and 22 is preferably formed as an aspherical surface.

  In the example illustrated in FIG. 2, the light receiving unit 30 is a line sensor in which individual sensors are arranged one-dimensionally in a direction orthogonal to the conveyance direction of the measurement object 100. As the line sensor, a CCD line sensor, a one-dimensional photodiode array, or the like can be applied.

  FIG. 3 is a diagram illustrating an arrangement of the light irradiation unit 10, the measurement object 100, and the condensing optical system 20 of the optical measurement device 1 illustrated in FIG. 2. FIG. 4A is a view of the optical measuring device 1 viewed from a direction orthogonal to the conveyance direction of the measurement object 100, and FIG. 4B is a diagram illustrating the optical measurement device 1 downstream of the measurement object 100 in the conveyance direction. It is the figure seen from the side.

  As shown in FIG. 3A, the measurement object 100 is curved along the outer shape of the cylindrical transport roller 112. The light beam from the semiconductor laser 11 is irradiated from the tangential direction to the curved measuring object 100. This light beam is expanded to a width H by the cylindrical lenses 12, 13, and 14, as shown in FIG. Further, as shown in FIG. 5A, the measurement object 100 is narrowed down to have a thick light flux that is thinner than the thickness t of the measurement object 100 and larger than the eccentric amount of the conveying roller 112 in the thickness direction of the measurement object 100. This is preferable in terms of suppressing the influence on the back side of the measurement object.

  Further, the condensing optical system 20 is formed so that the focal length of the cylindrical lens 21 is approximately L / 4, and the distance L between the measurement object 100 and the light receiving unit 30 is approximately L / 4, as illustrated. It arrange | positions in the position used as / 2. The cylindrical lens 22 is formed to have a focal length of approximately L / 2, and is disposed closer to the light receiving unit 30 than the position of approximately L / 2.

  As a result, the region to be measured having a width H that is substantially equal to (1 ×) in the conveyance direction of the measurement object 100 shown in FIG. The image is reduced to the illustrated width h on 30 (magnification h / H). For example, as shown in FIG. 4B, when there is a foreign object or a flaw at a position A which is a distance Ha from the center in the width direction of the measurement area, the scattered light due to the foreign substance or the flaw is converted into the cylindrical lens 21 and The light is guided by the cylindrical lens 22 and condensed at a distance ha = Ha · h / H from the center of the line sensor as the light receiving unit 30. That is, by determining which output is high among the sensors constituting the line sensor, it is possible to determine at which position in the measurement target area having the width H the foreign matter is attached.

  In this way, the measurement object is bent along the outer shape of the conveyance roller, and the light beam from the semiconductor laser is irradiated from the tangential direction of the measurement object, so that the conveyance roller is slightly decentered and measured. Even if the area is displaced, the position to be irradiated with the laser beam, which is the measurement area, is not shifted in the transport direction, and only the distance to the condensing optical system is slightly changed. Thus, there is no deviation between the imaging position of the scattered light from the region to be measured and the light receiving line of the line sensor, and an optical measuring device that can accurately detect the presence of foreign matter can be obtained. With this configuration, it is possible to provide an optical measurement apparatus that can accurately detect the presence of foreign matter in a wide range of measurement areas by sequentially transporting and measuring the measurement object.

  Furthermore, the condensing optical system is configured to have different refractive powers in the transport direction of the measurement object and the direction orthogonal to the transport direction, and the magnification in the cross section in the transport direction is high, and in the cross section orthogonal to the transport direction. By setting the magnification low, it is possible to provide an optical measuring device that can sufficiently lengthen the longitudinal direction of the measurement region even if the light receiving portion is small and can efficiently measure a wide range in a short time.

  FIG. 4 is a perspective view showing a modification of the optical measuring device 1 according to the first embodiment. Only the parts different from the optical measuring apparatus 1 shown in FIG. 2 will be described.

  The optical measuring device 1 shown in the figure is one in which the cylindrical lens 14 is omitted from the light irradiation unit 10 shown in FIG.

  The light beam from the semiconductor laser 11 is irradiated to the width H of the measurement object 100 in the thickness direction of the measurement object 100 while spreading in a direction orthogonal to the conveyance direction of the measurement object 100, and in the thickness direction of the measurement object 100. The light is condensed so as to be thinner than the thickness. At least one surface of the cylindrical lenses 12 and 13 is preferably formed as an aspherical surface.

  The configuration shown in the figure is a configuration suitable for the case where the scattered light due to the foreign substance in the measurement region indicated by the alternate long and short dash line has no directivity and is evenly scattered. By doing so, the configuration becomes simple, A lower cost optical measuring device can be obtained.

(Second Embodiment)
FIG. 5 is a perspective view showing an optical configuration of the optical measuring apparatus 1 according to the second embodiment. The optical measuring device 1 shown in FIG. 1 uses a scanning optical system using a rotating polygon mirror for the light irradiation unit 10, and the light receiving unit 30 is a single light receiving element that is not divided, for example, a photodiode. . Again, only the parts different from the optical measuring device 1 shown in FIG. 2 will be described.

  The light irradiation unit 10 shown in the figure is a scanning optical system. The light beam oscillated from the semiconductor laser 11 is converted into parallel light by a collimator lens (not shown), then scanned by the rotary polygon mirror 16 through the cylindrical lens 15, and is positioned from the position Hs on the measurement object 100 by the fθ lens 17. Irradiation is performed on a region to be measured having a width H indicated by a one-dot chain line up to He. Also in this case, it is the same that the curved measurement object 100 is irradiated from the tangential direction, and the irradiated light beam is preferably narrowed to be thinner than the measurement object in the measurement region. Reference numeral 18 denotes a reflecting mirror for detecting an initial position, and reference numeral 19 denotes a light receiving element that receives a light beam from the reflecting mirror 18. The initial position of the rotary polygon mirror 16 is detected by the signal output of the light receiving element 19. Note that a cylindrical lens may be arranged between the fθ lens 17 and the measurement object 100 so that a light beam is irradiated perpendicularly to the measurement region H with respect to the measurement region having a width H indicated by a one-dot chain line.

  In the case of the configuration as in this example, the light receiving unit 30 does not have to be the above-described line sensor, one-dimensional photodiode array, or the like, and can be configured with a single light receiving element.

  FIG. 6 is a timing chart showing the state of the light receiving unit 30 with and without foreign matter in the optical measuring device 1 according to the second embodiment. Hereinafter, detection of a foreign substance of the optical measurement apparatus 1 according to the second embodiment will be described with reference to FIG.

  In the output of the light receiving unit 30 shown in the figure, the state indicated by a indicates a case where there is no foreign substance, and the state indicated by b in the figure indicates a case where there is a foreign substance.

As shown in the figure, by detecting the rotation state of the rotary polygonal mirror 16 based on the output from the light receiving element 19 disposed in the light irradiation unit 10, the laser to the measurement area having the width H of the measurement object 100 is measured. The light scanning timing can be known. In the figure, after the time t _{0 has} elapsed from the fall of the output of the light receiving element 19, scanning of the laser beam to the measurement region having the width H is started, and scanning from Hs to He of the measurement region is performed at time t _1. Yes.

At this time, when there is no foreign object in the measurement area having the width H, the output of the light receiving unit 30 configured by a single photodiode is a noise level output because there is no scattered light (state shown by a) ). On the other hand, when there is a foreign object in the measurement area with the width H, the scattered light is received, and the photodiode output becomes a high value within the scanning time t ₁ (state shown by b). When this photodiode output becomes higher than a predetermined value, it can be determined that there is a foreign object in the measured region. Further, the distance from the position Hs to the foreign matter can be obtained by H · t ₂ / t ₁ from the elapsed time t ₂ from Hs and the scanning time t ₁ .

  Even with such a configuration, it is possible to obtain the same effects as those of the optical measurement apparatus according to the first embodiment.

  That is, the light irradiation unit is a scanning optical system and the light receiving unit is a single light receiving element, so that complicated alignment adjustment on the light receiving unit side is not required, and only the scattered light is guided onto the light receiving element. It can be set as the optical measuring device which can determine not only detection but the position. In the second embodiment, the photodiode is described as an example of the single light receiving element. However, the present invention is not limited to this, and other light receiving elements such as a photomultiplier tube are used. May be.

  Further, a configuration in which the light irradiation unit is a scanning optical system and a line sensor, a one-dimensional photodiode array, or the like is applied to the light receiving unit is possible.

  FIG. 7 is a diagram showing another modification of the condensing optical system 20. In this figure, cylindrical lenses 21 and 22 constituting the condensing optical system 20 shown in FIGS. 2, 4 and 5 are integrally formed. Also in the condensing optical system 20 shown in the figure, the surface on the measurement object side is formed to have refractive power in the conveyance direction of the measurement object 100, and the surface on the light receiving unit side is orthogonal to the conveyance direction of the measurement object 100. It is formed to have refractive power in the direction. Such a condensing optical system 20 can be easily aspherical and reduced in cost by being integrally formed of a resin material.

  FIG. 8 is a diagram illustrating another modification of the condensing optical system 20. The condensing optical system 20 shown in the figure is arranged such that the magnification of the cylindrical lens 21 is increased to be closer to the measuring object 100. With such an arrangement, the numerical aperture on the incident side of the cylindrical lens 21 can be made larger than the condensing optical system 20 shown in FIGS. 2, 4, and 5, and the condensing power is improved. An optical measuring device capable of detecting finer foreign matters can be obtained.

  The wavelength of the light beam emitted from the semiconductor laser used as the light source in the light irradiation unit 10 described in the first and second embodiments is preferably 400 nm to 850 nm in the visible region. By adjusting the wavelength in the visible region, the adjustment of the apparatus can be facilitated. In addition, it is preferable to use a light source on the short wavelength side when it is desired to detect a finer foreign substance in the above wavelength range, and a general light source on the long wavelength side is used when it is desired to lower the cost. Preferably, it is appropriately selected and used according to the purpose.

It is a block diagram which shows the schematic structure of the whole optical measuring device which concerns on this Embodiment. It is a perspective view which shows the optical structure of the optical measuring device which concerns on 1st Embodiment. It is a figure which shows arrangement | positioning of the light irradiation part of the optical measuring apparatus shown in FIG. 2, a measuring object, and a condensing optical system. It is a perspective view which shows the modification of the optical measuring device which concerns on 1st Embodiment. It is a perspective view which shows the optical structure of the optical measuring device which concerns on 2nd Embodiment. It is a timing chart which shows the state of the light-receiving part with and without the foreign substance of the optical measuring device according to the second embodiment. It is a figure which shows the other modification of a condensing optical system. It is a figure which shows the other modification of a condensing optical system. It is a figure which shows the problem of the conventional optical measuring device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical measuring apparatus 10 Light irradiation part 11 Semiconductor laser 12, 13, 14, 15 Cylindrical lens 16 Rotating polygon mirror 17 f (theta) lens 20 Condensing optical system 21, 22 Cylindrical lens 30 Light receiving part 40 A / D conversion part 50 Determination part 60 Control part 70 Display part 100 Measurement object 110 Conveyance part 111,112,113 Conveyance roller 120 Encoder

Claims (5)

A light irradiating unit for irradiating a region to be measured on the surface of the measurement object to be conveyed; a condensing optical system for condensing the scattered light on the surface of the measurement object; and In an optical measuring device having a light receiving unit that receives the scattered light,
Bending the measurement object, and irradiating the laser beam from a tangential direction of the measurement object ;
The condensing optical system includes at least a first lens in which a cross section in the conveyance direction of the measurement object is formed as a curved surface, and a second lens in which a cross section perpendicular to the conveyance direction is formed as a curved surface, The first lens is disposed on the side closer to the measurement object, the second lens is disposed on the side closer to the light receiving unit, and the distance between the measurement region of the measurement object and the light receiving unit is set. An optical measuring device, wherein L is a focal length in a cross section in the transport direction of the measurement object, and L / 2 is a focal length in a cross section orthogonal to the transport direction . The optical measurement apparatus according to claim 1, wherein the measurement object is curved along an outer shape of a cylindrical roller. 3. The optical measurement apparatus according to claim 1, wherein the laser beam is narrowed to be thinner than the thickness of the measurement object in the measurement region. The light irradiation unit is scanning optical system, the light receiving portion is optical measuring device according to any one of claims 1 to 3, characterized in that it is constituted by a single light receiving element. In the optical measuring method using the optical measuring device according to any one of claims 1 to 4,
Flexibility is curved the measurement object having,
It actuates the light irradiation unit irradiates the laser light from the tangential direction of the curved portion of the object to be measured,
The scattered light from the surface of the object is condensed by the condensing optical system,
Optical measuring method characterized by receiving the collected the scattered light by the light receiving unit, to determine the state of the surface of the object based on the amount of it.

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