JP3099462B2 - Cylindrical surface inspection method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting a cylindrical surface for inspecting defects on a cylindrical surface, for example, scratches and uneven plating on the surface of a cylinder for a gravure printing press.

[0002]

2. Description of the Related Art In order to detect defects such as scratches and uneven plating on the surface of a cylinder for a gravure printing press, conventionally, visual inspection and surface observation with an optical microscope have been performed. There is no known inspection method or inspection apparatus suitable for the method.

[0003]

However, it is difficult to find minute defects by visual inspection. Further, in surface observation using an optical microscope, it takes time to perform observation over a wide range of the surface of the cylinder. Therefore, there is a demand for the development of an inspection method and apparatus suitable for inspecting defects on the surface of a cylinder, instead of the appearance inspection and the optical microscope inspection.

The present invention has been made to meet such a demand, and an object of the present invention is to provide a cylindrical surface inspection method and a cylindrical surface inspection method capable of performing a defect inspection over a wide range of the surface of a cylinder in a short time. It is to provide a device.

[0005]

In order to achieve the above object, a method for inspecting a cylindrical surface of the present invention is directed to a method for inspecting a cylindrical surface of a light source. On the other hand, the step of making the light enter from the normal direction of the surface of the test area, and converting the optical path of the reflected light in the normal direction of the surface of the test area with respect to the incident light into one direction along the longitudinal direction of the cylindrical surface Forming a two-dimensional image corresponding to the surface of the test area by two-dimensionally projecting the light whose path has been changed, and wherein the cylindrical surface has a cylindrical shape.
Ru outer surface der of the subject.

[0006]

[0007]

According to another aspect of the present invention, there is provided an apparatus for inspecting a cylindrical surface, comprising: a light source means; and a light emitted from the light source means. Incident means for entering the light from the normal direction of the surface, conversion means for converting the optical path of the vertically reflected light from the surface of the test area to the incident light into one direction along the longitudinal direction of the cylindrical surface, and the direction conversion Projecting the two-dimensionally projected light to form a two-dimensional image corresponding to the surface of the region to be inspected, an imaging unit for capturing the two-dimensional image, and an image obtained by the imaging unit. A binarizing means for forming a binarized signal corresponding to light and dark caused by a surface defect on the surface of the test area, and determining whether or not there is a defect on the surface of the test area based on the binarized signal Means.

[0009] Instead of the determination means, an output means for outputting a binarized distribution of the image based on the binarized signal may be provided.

According to an embodiment of the present invention, a cylindrical surface inspection apparatus having an image pickup means is provided by moving the incident means, the conversion means, and the image pickup means integrally along the longitudinal direction of the cylindrical surface. The apparatus further includes longitudinal scanning means for scanning the surface of the test area along the longitudinal direction of the surface.

According to an embodiment of the present invention, the cylindrical surface in the above-described method and apparatus is an outer surface of a cylindrical subject.

[0012]

According to the method and the apparatus of the present invention, the optical path of the reflected light in the direction normal to the surface of the test area with respect to the light incident from the direction normal to the surface of the test area is the longitudinal direction of the cylindrical surface. By being converted into one direction along the direction, the test area surface as a curved surface is projected as a planar image.

[0013]

FIG. 1 shows a conceptual apparatus configuration for achieving a cylindrical surface inspection method according to the present invention as a first embodiment of the present invention. In this embodiment, for the sake of simplicity, it is assumed that there is no light path shield such as a mechanical device existing on the light path.

In FIG. 1, a cylinder 2 to be measured is
Is a cylinder for a gravure printing machine, for example, and its outer surface is mirror-finished by plating or the like. In the following description, the direction along the longitudinal direction of the cylinder 2 is defined as a Y-axis direction, and the radial direction of the cylinder 2 is defined as a Z-axis direction.
A surface light source 4 and a screen 6 are arranged on both ends of the cylinder 2 in the Y-axis direction.

As shown in FIG. 2 in particular, the surface light source 4 includes a parabolic mirror 8, a light source 10 disposed inside the parabolic mirror 8, and a circular shielding plate 1 for covering a central portion of the parabolic mirror 8 in a circular shape.
2 is provided. The light (hereinafter, referred to as measurement light) H emitted from the surface light source 4 is a plane light having a circular cross section of a light beam. That is, the measurement light H emitted from the surface light source 4 travels in a virtual hollow cylindrical shape as indicated by reference numeral 24.

Referring again to FIG. 1, the cylinder 2 is
It is arranged coaxially with the hollow cylindrical shape formed by the measurement light H emitted from the surface light source 4 and on the inner peripheral side of the hollow cylindrical shape.

Here, the cylindrical surface formed by the surface in a partial region T in the longitudinal direction of the cylinder 2 is defined as an inspection surface. As viewed from the surface light source 4, an annular half mirror 16 is disposed coaxially with the cylinder 2 on the optical path of the measurement light H on the outer peripheral side of the cylinder 2 on the near side of the region T.
The half mirror 16 has an inner peripheral surface facing the surface light source 4 as a transmitting surface and an outer peripheral surface facing the screen 6 as a reflecting surface.

Further, an annular mirror 18 is coaxially arranged on the outer peripheral side of the half mirror 16. This mirror 1
In 8, the outer peripheral surface of the cylinder 2 and the inner peripheral surface facing the screen 6 are reflection surfaces.

FIG. 3 shows an optical system as described above in which a cylinder 2
FIG. 3 shows a cross section along the longitudinal direction of FIG. However, since the above-described optical system is substantially rotationally symmetric with respect to the longitudinal axis of the cylinder 2, only a cross section above the cylinder 2 is shown.

The operation of the apparatus according to the first embodiment will be described below with reference to FIGS.

The measuring light H emitted from the surface light source 4 travels in the direction of the arrow along the Y-axis direction, and is inspected by the half mirror 16 along the Z-axis direction on the inspection surface (area T) of the cylinder surface 2a.
Toward the cylindrical surface at. That is, the measurement light H is incident on the inspection surface of the cylinder surface 2a from the normal direction of the inspection surface.

Next, the reflected light H 'reflected on the inspection surface of the cylinder surface 2a is reflected upward along the Z-axis direction of the cylinder 2 so as to follow the outward path in reverse, and further reflected on the mirror-18. Is reflected toward the screen 6 along the Y-axis direction. The reflected light H 'reflected by the mirror 18 is projected on the screen 6. The projected image 22
Corresponds to an image in which the measured surface on the surface of the cylinder 2 is shown two-dimensionally in an annular shape. With this projected image 22, the inspection surface of the cylinder surface 2a can be observed. In addition, each Mira-16,1
The inspection surface can be scanned along the longitudinal direction of the cylinder surface 2a by moving the mirror group including the mirror 8 or the cylinder 2 along the Y-axis direction by appropriate means.

Each of the mirrors 16 and 18 as shown in FIGS.
According to the arrangement, the width of the inspection surface per one inspection along the Y direction is determined according to the size of each of the mirrors 16 and 18. For example, as shown in FIGS. 4 and 5, when each of the mirrors 16 and 18 is small (FIG. 4), the width T _{1 of the} inspection surface is also small, and when each of the mirrors 16 and 18 is large (FIG. 5). It is larger width T ₂ of the the inspection surface (T _2> T _1).

Therefore, by appropriately selecting the size of each of the mirrors 16 and 18, the number of inspections can be minimized, and more reliable inspection can be performed over the entire surface of the cylinder 2. Become. Further, since the inspection light H is incident on the surface of the cylinder 2 from the normal direction, each of the mirrors -1
By appropriately selecting the inner diameters of the cylinders 6 and 18, it becomes possible to inspect cylinders of various diameters.

Next, the image 22 projected on the screen 6
FIGS. 6 and 7 show a method for detecting a defect on an inspection surface from a pattern.
This will be described with reference to FIG.

If there is a defect on the inspection surface of the cylinder surface 2a, for example, a convex portion 26 (FIG. 6) due to uneven plating or a concave portion 28 (FIG. 7) such as a relatively large scratch, the incident direction from the inspection surface with respect to the incident direction. The reflected light H ', which should be reflected vertically, is disturbed by the flaw, travels with a spread proportional to the distance L from the inspection surface to the screen 6, and is projected on the screen 6 as a distribution of light and dark. You. That is, the distribution of the reflected light of the reflected light H 'is dense in the bright portion W on the light and dark distribution, and similarly sparse in the dark portion B. This difference in light and darkness is enlarged on the screen 6 to a size that can be sufficiently visually confirmed.

When a relatively small flaw is present as a defect on the inspection surface of the cylinder surface 2a, the reflected light H 'from the inspection surface is reflected by the reflected light from the flaw and the reflected light from the part without the flaw. Includes interference light with light. Therefore, interference fringes are observed in the projected image 22 on the screen 6.

In the above embodiment, since it is assumed that there is no shield in the optical path such as a mechanical element, the inspection surface by one inspection covers the entire circumference in the region T of the cylinder 2 and The projected image 22 is projected as a continuous ring. However, in an actual device, the optical path is shielded by a mechanical device or the like. Therefore, the inspection surface that can be inspected by one inspection is a part of the region T in the circumferential direction. Therefore, each of the mirrors 16 and 18 does not necessarily have to have an annular shape, but may have an arc shape that covers a part of the region T in the circumferential direction. Similarly, the cross-sectional shape of the luminous flux of the measurement light H emitted from the surface light source 4 does not necessarily need to be an annular shape, but may be an arc that forms a part of the annular shape.

FIG. 8 shows a second embodiment of the present invention. In this embodiment, each mirror-1 in the apparatus shown in the first embodiment is used.
It has a drive system for the cylinders 6, 18, and the cylinder 2, and the same components as those in the first embodiment are denoted by the same reference numerals.

In FIG. 8, the detection unit 30 includes a mirror group including mirrors 16 and 18 (not shown in FIG. 8). The positional relationship of the mirror group with respect to the cylinder 2 is the same as in the first embodiment. The detection unit 30 is fixed to a moving rail 32 arranged near the cylinder 2 along the Y-axis direction. This moving rail 3
2 is a detection unit 30 driven by the Y-axis motor 34.
And can move along the Y-axis direction integrally.

One end of the rotary shaft 36 substantially coincident with the longitudinal center axis of the cylinder 2 is connected to a drive shaft 40a of the θ-axis motor 40 via a drive side bearing 38, and the other end is driven side bearing 42 It is rotatably supported by. Accordingly, the cylinder 2 rotates in the θ direction around the rotation axis 36 by the drive of the θ-axis motor 40.

The Y-axis motor 34 and the θ-axis 40 are controlled by a motor controller 44. Commands such as drive, stop, and rotation speed of the motors 34 and 40 by the motor control unit 44 are:
It is provided by an operator operating an input device such as a control box 46 attached to the motor control unit 44, for example.

In the second embodiment, as shown in FIG. 9, mechanical elements such as bearings 38 and 42 for supporting the cylinder 2 partially block the optical path. Therefore, the image projected on the screen 6 is not an image over the entire circumference of the inspection surface in the circumferential direction, but is an image 22 partially shielded as shown in FIG. Therefore, by operating the control box 46,
By rotating the cylinder 2, the inspection is performed over the entire circumference of the inspection surface in the circumferential direction. Further, by operating the control box 46, the detection unit 30 is moved in the Y-axis direction, and the inspection is repeated while scanning the inspection surface in the Y-axis direction, so that the entire cylinder surface 2a is finally inspected.

FIG. 11 shows a third embodiment of the present invention. A CCD camera 48 for capturing the image 22 on the screen 6 is attached to the detection unit 30 in this embodiment. In the present embodiment, an image obtained from the projection image 22 of the inspection surface by the CCD camera 48 is digitally converted into a bright / dark (white / black) binary image and the scanning of the inspection surface is automated. In this way, the inspection is automated. In the third embodiment, the same components as those in the second embodiment are denoted by the same reference numerals.

In FIG. 11, the central management unit 50 is set with information on the initial conditions of the inspection from input means (not shown) such as a keyboard attached thereto. Here, the initial conditions include the length of the cylinder 2, the binarization level, the determination level of the determination unit 64 described below, and the like. The setting signal S1 as information on these initial conditions is given to a system control unit 52 that controls the entire inspection apparatus. Also, this system control unit 5
2 generates a monitor signal S2 for each part of the inspection device such as the movement amount of the CCD camera 48, and feeds back the monitor signal S2 to the central management unit 50. Thereby, the centralized management unit 50 executes monitoring of the entire inspection apparatus.

When the system control unit 52 to which the setting signal S1 is supplied as described above supplies the test start signal S3 to the timing generation unit 54, the test is performed as follows.

First, the projected image 22 by the CCD camera 48
A description will be given of the determination of a defect based on the image pickup. The timing generator 54 supplies an imaging timing signal S5 to a camera controller 56 that controls the imaging signal S4 of the CCD camera 48. Thereby, the CCD camera 48 captures the projected image 22.

The surface of the cylinder 2a corresponding to this imaging area is divided in the longitudinal direction and the circumferential direction of the cylinder 2 according to the field of view of the CCD camera 48, as shown in FIGS. Each square T _ij in FIGS. 12 and 13
(i = 1,2,3... n, j = 1,2,3... n) correspond to one imaging region.

The image signal of the CCD camera 48 is supplied to a binarization processing unit 58 via a camera control unit 56, and is binarized. The binarized signal S6 by the binarization processing unit 58
Is provided to the image memory 60 and stored therein. The stored binarized signal S6 is provided to a counting control unit 62 that controls the white / black counting. Count control unit 62
Counts the white / black of the binarized signal based on the count start signal S7 of the timing generator 54, and supplies the counting result to the determiner 64. The determination unit 64 determines the presence or absence of a defect based on the counting result of the counting control unit 62, and displays the determination result on a display unit 66 such as a display.

As the display section 66, a buzzer, a lamp, or the like that notifies an operator of the presence of a defect may be used.
Further, instead of the determination unit 64 and the display unit 66, a configuration may be employed in which the binarization distribution obtained by the binarization processing unit 58 is output to an output unit such as a printer or a display. In this case, the operator determines whether or not there is a defect by referring to the output binarized distribution.

On the other hand, the scanning of the inspection surface is performed by a CCD provided from the timing generator 54 to the position signal generator 68.
This is executed based on the movement timing signal S8 of the camera 48. The position signal generator 68 is further provided with a position information signal S9 of the CCD camera 48 from the system controller 52. The position signal generator 68 determines the amount of movement of the CCD camera 48 based on the movement timing signal S8 and the position information signal S9,
A position signal S10 as a movement command of the camera 48 is given. As a result, the motor control unit 44
The 4 and θ-axis motors 40 are driven to automatically move the CCD camera 48 in the circumferential direction (the column direction in FIGS. 12 and 13) and the length direction (the row direction in FIGS. 12 and 13) of the cylinder 2. . Along with this automatic movement, from the imaging of the projected image 22 by the above-described CCD camera 48, the determination of a defect based thereon is performed over a desired region or the entire surface of the cylinder surface 2a.

According to the third embodiment, the detection unit 3
The 0 and / or area light source 4 need only be large enough to cover the viewing angle of the CCD camera 48. Therefore, the detection unit 30 and / or the surface light source 4 does not need to cover the entire circumference of the cylinder 2, and may have an arc-shaped cross section partially covering the circumference of the cylinder 2 as shown in FIG. Is possible. According to this downsizing, a work space for replacing the cylinder 2 is largely secured.

When comparing the second and third embodiments, in the second embodiment, as shown in FIG.
The optical path length L of the reflected light H 'from the mirror 18 to the screen 6 varies depending on the position in the Y direction, and the magnification of the defect changes.

On the other hand, in the third embodiment, the area of one inspection is more limited than in the second embodiment due to the viewing angle and resolution of the CCD camera 48, and the required number of measurements is increased compared to the second embodiment. I do. However, at any position of the cylinder 2, the reflected light H ′ from the inspection surface
Since the distance to reach 8 is kept constant, there is an advantage that the magnification does not change.

In each of the above embodiments, the outer peripheral surface of the cylinder 2 was used as the surface to be inspected. However, the present invention is not limited to this, and the inner peripheral surface of the hollow cylindrical member whose inner peripheral surface is a mirror surface is used. It can also be applied to inspections. In this case, by arranging the mirrors 16 and 18 on the inner surface side of the hollow cylindrical object so that the optical paths of the measuring light H and the reflected light H 'pass through the inside of the hollow cylindrical object, the same as in the above embodiments. Inspection can be performed.

[0046]

As described above, according to the method and the apparatus for inspecting a cylindrical surface of the present invention, it is possible to project a curved surface of a region to be inspected as a two-dimensional image. Defect detection is easier than inspection and optical microscope inspection, and defect inspection can be performed over a wide area of a cylindrical surface in a short time.

[Brief description of the drawings]

FIG. 1 is a configuration diagram conceptually showing a cylindrical surface inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining an operation of the surface light source in FIG. 1;

FIG. 3 is an optical path diagram showing an optical path at an upper part of a cylinder of the apparatus of FIG. 1;

FIG. 4 is a view corresponding to FIG. 3, and is an optical path diagram showing an optical path when a mirror is small.

FIG. 5 is a view corresponding to FIG. 3, and is an optical path diagram showing an optical path when a mirror is large.

FIG. 6 is an explanatory diagram for explaining the principle of defect detection in the method and apparatus of the present invention, and is a diagram showing a light beam distribution on a screen when a convex portion exists on an inspection area surface.

FIG. 7 is an explanatory view corresponding to FIG. 6, and is a view showing a light beam distribution on a screen when a concave portion exists on the inspection area surface.

FIG. 8 is a configuration diagram showing a second embodiment of the present invention.

FIG. 9 is a diagram showing the device of FIG. 8 as viewed from the direction of arrow ix-ix.

FIG. 10 is a plan view showing an image projected on a screen of the apparatus of FIG. 8;

FIG. 11 is a configuration diagram showing a third embodiment of the present invention.

FIG. 12 is an explanatory diagram showing an example in which the inspection area on the cylinder surface is divided according to the viewing angle of the CCD camera in the third embodiment.

FIG. 13 is a development view showing the cylinder surface in FIG.

14 is a diagram showing an example of a cross-sectional shape of the detection unit in FIG.

FIG. 15 is an optical path diagram for explaining a change of an optical path length from a mirror to a screen according to a position of a detection unit.

[Explanation of symbols]

4 surface light source (light source means), 2 cylinder (cylindrical subject), 2a cylinder surface (cylindrical surface), 6 screen (projection means), 16 half mirror (conversion means), 18
... mirror (conversion means), 34 ... Y-axis motor (longitudinal scanning means), 40 ... θ-axis motor (circumferential scanning means), 48
... CCD camera (imaging means), 58 ... Binarization processing section (binarization means), 64 ... Determination section (determination means).

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-57-28239 (JP, A) JP-A-50-158387 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/952-21/954 G01B 11/30

Claims (6)

(57) [Claims] 1. A method for inspecting a mirror-like cylindrical surface, wherein light emitted from a light source is directed in a direction normal to the surface of a test region formed by at least a part of the cylindrical surface. And a step of converting the optical path of the reflected light in the direction normal to the surface of the test area with respect to the incident light into one direction along the longitudinal direction of the cylindrical surface. by projecting two-dimensionally, characterized forming a two-dimensional image corresponding to the subject region surface, Tona is, the cylindrical surface is an outer surface of the subject having a cylindrical shape, that Cylindrical surface inspection method. 2. An apparatus for inspecting a mirror-like cylindrical surface.
Te, a light source unit, the light emitted from the light source means, at least the cylindrical surface
The direction of the normal to the surface of the test area
Means for causing light to enter from an opposite direction, and an optical path of vertically reflected light from the surface of the test area with respect to the incident light
Into one direction along the longitudinal direction of the cylindrical surface
Conversion means, and two-dimensionally projecting the light whose direction has been changed.
Projecting means for forming a two-dimensional image corresponding to the surface of the test area
If an imaging means for capturing a two-dimensional image described above, on the basis of the image obtained by the imaging means, the detected region
Generates a binary signal corresponding to the light and dark caused by surface defects on the surface.
Generating a binarized distribution of the image based on the binarized means and the binarized signal.
Output means for applying pressure to the cylindrical surface.
Inspection equipment. 3. An apparatus for inspecting a mirror-like cylindrical surface for surface defects.
A light source means, and light emitted from the light source means, at least on a cylindrical surface.
The direction of the normal to the surface of the test area
Means for causing light to enter from an opposite direction, and an optical path of vertically reflected light from the surface of the test area with respect to the incident light
Into one direction along the longitudinal direction of the cylindrical surface
Conversion means, two-dimensionally projecting the light whose direction has been changed, and
Projection means for forming a two-dimensional image corresponding to the surface, imaging means for imaging the two-dimensional image, and a test area based on the image obtained by the imaging means
Generates a binary signal corresponding to the light and dark caused by surface defects on the surface.
And the presence or absence of a defect on the surface of the inspection area based on the binary signal.
Determining means for determining the cylindrical surface.
Inspection equipment. 4. The apparatus according to claim 1, wherein said incident means, conversion means, and image pickup means
By moving it integrally along the length of the cylindrical surface
Scanning the surface of the test area along the longitudinal direction of the cylindrical surface.
The apparatus according to claim 1, further comprising a longitudinal scanning means.
4. The cylindrical surface inspection apparatus according to 2 or 3. 5. The cylindrical surface is moved along a circumferential direction of the cylindrical surface.
In this way, the surface of the test area is
The apparatus further comprises a circumferential scanning means for scanning.
A cylindrical surface inspection apparatus according to any one of claims 2 to 4.
Place. 6. The method according to claim 1, wherein the cylindrical surface is outside the cylindrical subject.
The surface according to any one of claims 2 to 5, wherein the surface is a surface.
Item 2. A cylindrical surface inspection apparatus according to item 1.