JP2014066663A - Visual inspection system and visual inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a visual inspection system or the like for precisely performing visual inspection of an object, such as hologram, having reflection directivity in a wide range with a simple configuration.SOLUTION: A visual inspection system 1 includes a lighting apparatus 7, an imaging apparatus 5, a condenser lens 9 provided separately from a lens of the imaging apparatus 5, and an image processing apparatus 13 or the like. When the visual inspection system 1 performs visual inspection on a hologram 3a, the hologram 3a is irradiated with inspection light 20 from the lighting apparatus 7 while conveying a hologram sheet 3. The inspection light 20 reflected from the hologram 3a in a predetermined direction is condensed by the condenser lens 9 toward the imaging apparatus 5. The condensed inspection light 20 is received by the imaging apparatus 5 for imaging. The image processing apparatus 13 performs visual inspection on the hologram 3a by use of the image captured by the imaging apparatus 5.

Description

  The present invention relates to an appearance inspection system and an appearance inspection method for inspecting an object having reflection directivity such as a hologram.

  The hologram sheet is formed on a substrate as a hologram with interference fringes of reference light irradiated on an object and object light reflected from the object. Since the design of the hologram changes depending on the viewing direction, it has a high design. Moreover, since it is difficult to form the same pattern, it has high anti-counterfeiting properties and is used for various purposes.

  The hologram sheet is manufactured, for example, by applying a photosensitive material to a substrate, exposing the photosensitive material with a laser, and then performing development, fixing processing, and the like to form a hologram on the substrate. After the hologram sheet is manufactured, an appearance inspection is performed to check whether the hologram pattern is correctly formed.

  When inspecting the pattern (appearance) of the hologram, the hologram is irradiated with inspection light at a wavelength and an incident angle that satisfy the pattern formation condition. The hologram diffracts and reflects the incident inspection light in a specific direction, so the appearance inspection is possible by receiving the inspection light reflected in this direction, imaging the pattern, and comparing it with the correct reference image is there. The characteristic of reflecting the incident light in a specific direction is referred to herein as reflection directivity.

  As shown in FIG. 7, the imaging of the pattern is performed by the imaging device 5 arranged in the reflection direction of the inspection light 20 from the hologram 3 a of the hologram sheet 3. However, it is difficult to image the inspection light 20 reflected in the above direction over the entire field of view due to the restriction of the angle of view of the imaging device 5. Therefore, there is a case where the picture is not appropriately captured at the edge of the visual field, thereby causing a problem that the accuracy of the appearance inspection is lowered.

  As a method for solving this problem, it is conceivable to use a telecentric lens or a wide imaging device for the imaging device (for example, Patent Documents 1 and 2).

JP 2006-105844 A JP 2009-133743 A

  However, when trying to inspect the appearance of a hologram over a wider range, the methods of Patent Documents 1 and 2 have a large-scale configuration such that a large number of imaging devices need to be arranged or a larger imaging device needs to be used. Therefore, there is a problem that costs increase.

  The present invention has been made in view of the above-described problems, and provides an appearance inspection system and the like that can inspect the appearance of an object having a reflection directivity such as a hologram with high accuracy over a wide range with a simple configuration. For the purpose.

  In order to achieve the above-described object, a first invention is an appearance inspection system that performs an appearance inspection of an object having reflection directivity, and is provided separately from an illumination device, an imaging device, and a lens of the imaging device. A condensing lens; and an image processing device, wherein the illumination device irradiates the object with inspection light, and the condensing lens reflects the inspection light reflected in a specific direction from the object. The imaging device receives the collected inspection light and performs imaging, and the image processing device uses the image captured by the imaging device to inspect the appearance of the object. It is an appearance inspection system characterized by performing.

  In the appearance inspection system of the present invention, inspection light irradiated from an illumination device and reflected in a specific direction from an object having a reflection directivity such as a hologram is imaged by a condensing lens provided separately from the lens of the imaging device. Focused towards the device. The imaging apparatus receives the collected inspection light and performs imaging, so that the accuracy of the image at the edge of the field of view is not lowered and the pattern of the object can be uniformly imaged. Accordingly, it is possible to perform a high-accuracy and wide-ranging appearance inspection using only a small number of small-sized imaging devices, and a simple and low-cost configuration can be achieved.

The condensing lens is preferably a Fresnel lens.
Thereby, a condensing lens can be comprised thinly and it can be set as a simpler structure.

It is desirable that the condenser lens is provided over the entire width of the inspection range of the object.
As a result, the appearance inspection of the inspection range can be performed by imaging with one imaging device, so that the configuration can be simplified.

It is desirable that the object is a hologram.
In the hologram, it is important that a pattern is correctly formed from the viewpoint of design and anti-counterfeiting, and the effect of performing an appearance inspection using the appearance inspection system of the present invention is particularly great.

  According to a second aspect of the present invention, an appearance of an object having reflection directivity is obtained by an appearance inspection system including an illumination device, an imaging device, a condensing lens provided separately from the lens of the imaging device, and an image processing device. A visual inspection method for performing inspection, wherein the object is irradiated with inspection light from the illumination device, and the inspection light reflected in a specific direction from the object is collected by the condenser lens toward the imaging device. Receiving the captured and inspected inspection light by the imaging device and performing imaging; and performing an appearance inspection of the object using the image captured by the imaging device by the image processing device; It is an appearance inspection method characterized by having.

  According to the present invention, it is possible to provide an appearance inspection system and the like that can inspect the appearance of an object having reflection directivity such as a hologram with high accuracy over a wide range with a simple configuration.

The figure which shows the structure of the external appearance inspection system 1 The figure which shows arrangement | positioning of the imaging device 5, the illuminating device 7, the condensing lens 9, etc. The figure which shows arrangement | positioning of the imaging device 5, the illuminating device 7, the condensing lens 9, etc. The figure which shows the procedure of the external appearance inspection by the external appearance inspection system 1 The figure which shows the example which used the plano-convex lens as the condensing lens 9a The figure which shows the example which makes the inspection light 20 incline on a plane with respect to the conveyance direction of the hologram sheet 3 The figure explaining the example of appearance inspection

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

(1. Schematic configuration of visual inspection system 1)
First, a schematic configuration of the appearance inspection system 1 of the present embodiment will be described with reference to FIG.

  The appearance inspection system 1 performs an appearance inspection of the hologram 3a on the hologram sheet 3 conveyed in the conveyance direction indicated by the arrow A in the figure. As shown in the figure, the appearance inspection system 1 includes an imaging device 5, an illumination device 7, a condenser lens 9, a control device 11, an image processing device 13, a sensor 15, a display device 17, and the like.

  The illuminating device 7 irradiates the hologram 3a with inspection light at a wavelength and an incident angle that satisfy the pattern formation conditions of the hologram 3a. The hologram 3a diffracts and reflects the inspection light incident at this incident angle in a specific direction. In this embodiment, the hologram sheet 3 is reflected in the normal direction.

  The condensing lens 9 condenses the inspection light reflected from the hologram 3 a toward the imaging device 5. The condensing lens 9 is provided separately from the lens of the imaging device 5, and a Fresnel lens is used in this embodiment. This will be described later.

  The imaging device 5 receives the inspection light collected by the condenser lens 9 and images the pattern of the hologram 3a. The imaging device 5 includes an optical system including a condenser lens and a diverging lens, and a line camera having an electronic imaging unit that converts a subject image that has passed through the optical system into an image signal.

  The sensor 15 detects a timing mark (not shown) formed on the hologram sheet 3. When the sensor 15 detects the timing mark, it outputs a detection signal indicating this to the control device 11.

  The control device 11 is composed of, for example, a PLC (Programmable Logic Controller). When the detection signal is input from the sensor 15, the control device 11 outputs an imaging instruction to the image processing device 13.

  The image processing apparatus 13 is configured by, for example, a computer having a control unit, a storage unit, a communication unit, and the like. When an imaging instruction is input from the control device 11, the image processing device 13 controls the imaging device 5 to capture the image of the hologram 3 a and acquires an image that is an imaging result from the imaging device 5.

  Further, the image processing device 13 performs an appearance inspection of the hologram 3 a based on the image acquired from the imaging device 5. For example, it is assumed that the acquired image and a positive image stored in advance in the storage unit are compared to determine whether they are different, and if they are different, there is a poor appearance.

  The display device 17 displays a warning based on the result of the appearance inspection by the image processing device 13 or displays an image acquired from the imaging device 5 by the image processing device 13.

(2. Arrangement of imaging device 5, illumination device 7, condenser lens 9, etc.)
FIG. 2 is a perspective view showing the arrangement of the imaging device 5, the illumination device 7, the condenser lens 9, and the like. In addition, the arrow A of FIG. 2 shows the conveyance direction of the hologram sheet 3 similarly to FIG. 1, and the arrow B shows the width direction of the hologram sheet 3 orthogonal to this conveyance direction.

  3A, 3B, and 3C are views of the arrangement of the imaging device 5, the illumination device 7, the condenser lens 9, and the like as viewed from above in the direction C and the direction D in FIG. The same applies to FIGS. 5 and 6 described later.

  As shown in FIGS. 2 and 3, in the appearance inspection system 1 of this embodiment, the imaging device 5 receives the inspection light 20 reflected from the hologram 3 a with the full width of the hologram sheet 3 while conveying the hologram sheet 3. . Thereby, the inspection range 3b (FIG. 2) is assumed to extend over the entire width of the hologram sheet 3, and an appearance inspection is performed by imaging the entire pattern of the hologram 3a in the inspection range 3b. The width of the hologram sheet 3 is about 25 cm, for example.

  In accordance with this, in the appearance inspection system 1, a long illumination device 7 and a condenser lens 9 are provided along the width direction of the hologram sheet 3 above the hologram 3a.

  The condenser lens 9 is provided, for example, at a distance of about 2 cm from the hologram 3a and close to the hologram 3a. The condenser lens 9 is arranged over the entire width of the inspection range 3b. Further, the imaging device 5 is disposed above the condenser lens 9 and is in the center portion of the planar hologram sheet 3 in the width direction.

  The illumination device 7 irradiates the inspection light 20 over the entire width of the inspection range 3b. As shown in FIG. 3, the direction of the inspection light 20 incident on the hologram 3 a is a direction along the conveying direction of the hologram sheet 3 on the plane, and the direction described above with respect to the normal direction of the hologram sheet 3 on the vertical plane. It is inclined at an incident angle.

  The hologram 3 a diffracts and reflects the inspection light 20 in the normal direction of the hologram sheet 3. The reflected inspection light 20 reaches the condenser lens 9. The condensing lens 9 condenses the inspection light 20 toward the imaging device 5. The focal point of the condensing lens 9 is set so that the collected inspection light 20 is incident on the first lens on the object side of the imaging device 5, and the distance from the condensing lens 9 to the focal point is, for example, about 85 cm.

  In this embodiment, a Fresnel lens is used as the condensing lens 9, and the condensing lens 9 is formed thin. Although a Fresnel lens is a known one, a simple explanation is that one surface is flat, but on the other surface, a plurality of regions with different curvatures of the surface shape depending on the distance from the plane center are substantially serrated. It is formed. The relationship between the curvature of each region and the distance from the center is determined to be the same as the surface shape of the convex surface of the plano-convex lens, but the thickness is reduced.

(Appearance inspection by appearance inspection system 1)
Next, the procedure of appearance inspection by the appearance inspection system 1 will be described with reference to FIG.

  In the appearance inspection system 1, when a timing mark is detected by the sensor 15 for the hologram sheet 3 being conveyed (S <b> 1), a detection signal is input from the sensor 15 to the control device 11. Then, the control device 11 outputs an image capturing instruction to the image processing device 13, and the image processing device 13 controls the image capturing device 5 to image the image of the hologram 3a (S2).

  As described with reference to FIGS. 2, 3 and the like, the illumination device 7 irradiates the inspection light 20 over the entire width of the inspection range 3b, and the hologram 3a applies the inspection light 20 to the method of the hologram sheet 3. Diffracted and reflected in the line direction. The condensing lens 9 is provided close to the hologram 3a over the entire width of the inspection range 3b, and condenses the reflected inspection light 20 toward the imaging device 5. By receiving the inspection light 20 by the imaging device 5 while conveying the hologram sheet 3, it is possible to image the entire pattern of the inspection range 3 b of the hologram 3 a.

  The image processing device 13 acquires the imaging result of the imaging device 5 as an image and compares it with a positive image stored in advance in the storage unit (S3). If it is determined that these images match (S4: Yes), the series of processing ends.

  On the other hand, if it is not determined that the images match (S4: No), the display device 17 displays a warning indicating that an appearance defect has occurred, alerts the operator (S5), and ends the process. At this time, the image picked up by the image pickup device 5 can be displayed on the display device 17, and a portion different from the positive image can be shown as a portion where an appearance defect has occurred on the image. It is also possible to give a warning by an alarm such as a voice.

  Note that the appearance inspection is not limited to comparing the image acquired from the imaging device 5 with a positive image as described above, and it is possible to determine whether the image acquired from the imaging device 5 is good or bad using various criteria. It is also possible to determine.

  As described above, in this embodiment, the inspection light irradiated from the illumination device 7 and reflected in a specific direction from the hologram 3 a is collected by the condensing lens 9 provided separately from the lens of the imaging device 5. It is condensed toward The imaging device 5 picks up the collected inspection light and performs imaging, so that even in a wide inspection range, the accuracy of the edge of the field of view is not lowered, and the pattern of the hologram 3a is uniformly imaged. It becomes possible to do. Therefore, it is possible to perform a high-accuracy visual inspection only by using a small number of small-sized imaging devices 5 and to achieve a simple and low-cost configuration.

  In particular, in this embodiment, the condensing lens 9 is provided over the entire width of the inspection range 3b of the hologram 3a, whereby the appearance inspection of the hologram 3a in the inspection range 3b can be performed with one imaging device 5, and more Simple configuration. However, it is also possible to perform an appearance inspection of the hologram 3 a using a plurality of imaging devices 5 and condenser lenses 9.

  In this embodiment, a Fresnel lens is used as the condensing lens 9, which makes it possible to make the lens thin and to have a simple configuration. However, other lenses can be used instead of the Fresnel lens. The example is the condensing lens 9a shown in FIG.

  The condensing lens 9a is a plano-convex lens having one surface convex, but even in this case, the inspection light 20 reflected from the hologram 3a can be condensed toward the imaging device 5. In addition, a convex lens having convex surfaces on both sides can also be used. However, in these cases, since the lens becomes thick, it is advantageous to use a Fresnel lens in terms of simplicity of configuration.

  In the present embodiment, the inspection light is irradiated along the transport direction of the hologram sheet 3 on a plane. However, as shown in FIG. 6, the inspection light is irradiated obliquely with respect to the transport direction of the hologram sheet 3 as necessary. It is also possible. In the present embodiment, the inspection light is reflected in the normal direction of the hologram sheet 3, but may be reflected in other directions. Even in this case, the arrangement of the condenser lens 9 and the imaging device 5 may be determined in accordance with the reflection direction of the inspection light.

  Moreover, in this embodiment, the example which performs the external appearance inspection of the hologram 3a as the external appearance inspection system 1 was demonstrated. It is important that the hologram 3a has a correct pattern formed from the viewpoint of design and anti-counterfeiting, and the effect of performing an appearance inspection using the appearance inspection system 1 is particularly great. However, the object for visual inspection is not limited to the hologram 3a as long as it has reflection directivity. As an example, an object having specularity and performing regular reflection of incident light can be cited. Even in this case, the appearance inspection system 1 of the present embodiment can be applied, and the same effect can be obtained.

In the present embodiment, a line camera is used for the imaging device 5, but the present invention is not limited to this as long as the image of the hologram 3a can be captured. For example, a CCD (Charge
An area camera including an electronic imaging unit such as a coupled device (CMOS) or a complementary metal-oxide semiconductor (CMOS) may be used. In this case, the condensing lens 9 may be provided over the entire region including the width direction in the inspection range of the hologram 3a imaged by the area camera.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

1: Appearance inspection system 3a: Hologram 5: Imaging device
7: Lighting device 9, 9a: Condensing lens
11: Control device
13: Image processing device
15: Sensor

Claims (5)

An appearance inspection system that performs an appearance inspection of an object having reflection directivity,
An illumination device, an imaging device, a condenser lens provided separately from the lens of the imaging device, and an image processing device,
The illumination device irradiates the object with inspection light,
The condensing lens condenses the inspection light reflected in a specific direction from the object toward the imaging device,
The imaging device receives the collected inspection light and performs imaging,
The image processing apparatus performs an appearance inspection of the object using an image captured by the imaging device.   The appearance inspection system according to claim 1, wherein the condenser lens is a Fresnel lens.   The appearance inspection system according to claim 1, wherein the condenser lens is provided over the entire width of the inspection range of the object.   The appearance inspection system according to claim 1, wherein the object is a hologram. Appearance inspection method for inspecting an object having reflection directivity by an appearance inspection system including an illumination device, an imaging device, a condenser lens provided separately from the lens of the imaging device, and an image processing device Because
The inspection device is irradiated with inspection light from the illumination device, the inspection light reflected in a specific direction from the object is condensed toward the imaging device by the condenser lens, and the collected inspection light is collected. Receiving light by the imaging device and performing imaging;
A step of performing an appearance inspection of the object using the image captured by the image capturing device by the image processing device;
A visual inspection method characterized by comprising:

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