JP2002305741A - Image pickup device for printed mater of high reflectivity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device that uses a means in place of a conventional collimator lens so as to pick up an image of a printed matter of high reflectivity just as an actual thing. SOLUTION: The image pickup device 20 is provided with a surface light source 21, an optical film 22 on the surface of which a prism pattern is formed and that has a function equivalent to that of a prism collimating a light emitted from the surface light source 21, a half mirror 24 that reflects the collimated light onto an object 23 in parallel with a visual axis, and a two-dimensional CCD camera 25 that receives the light reflected in the object 23 and picks up an image of the object 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus for imaging a surface of a printed matter having a surface with a large light reflectance such as gold or silver to check whether or not the printed matter is correctly printed.

[0002]

2. Description of the Related Art Many imaging apparatuses of this type have been proposed. One example is disclosed in Japanese Patent Application Laid-Open No. Hei 9-136403.
FIG. 7 shows a "monitoring device for a printed matter having a glossy portion" described in Japanese Patent Application Laid-Open No. H10-209,878.

This monitoring device comprises an encoder 3 and a light source 4
, A collimator lens 5, a half mirror 6, a television camera 7, a timing control circuit 8, and an image processing circuit 9.
And a monitor 10.

The same pattern is repeatedly printed on the printed matter 1 to be monitored by the monitoring apparatus by the plate cylinder 2, and each pattern includes a portion having a large light reflectance such as gold or silver. Shall be The printed material 1 is traveling in the direction of arrow A by the plate cylinder 2 and a transport roller (not shown).

[0005] The encoder 3 is directly connected to the rotary shaft of the plate cylinder 2 and emits a pulse signal indicating the rotational position of the plate cylinder 2.

The light source 4 is a flash light source, and is composed of a strobe.

[0007] The collimator lens 5 converts the light emitted from the light source 4 into parallel light. The light source 4 is disposed at a position of the focal length f of the collimator lens 5.

[0008] The half mirror 6 reflects parallel light rays from the collimator lens 5 and vertically enters the printed matter 1 and transmits specularly reflected light from the printed matter 1.

The television camera 7 comprises a two-dimensional image sensor, for example, a three-CCD color television camera using three CCDs. The television camera 7 receives specularly transmitted light from the printed matter 1 that has passed through the half mirror 6.

The timing control circuit 8 receives the pulse signal from the encoder 3 and determines the IN sequence on the plate cylinder 2 based on the diameter of the plate cylinder 2 and the distance between the axis of the plate cylinder 2 and the center position of the television camera 7. The number of pulses until a predetermined portion of the drawn pattern moves to the center of the television camera 7 is counted, a light emission timing signal is sent to the light source 4, and the television camera 7 receives a timing signal indicating an imaging timing. The image processing circuit 9 transmits a timing signal indicating a timing at which the captured image is taken into the image memory.

An image processing circuit 9 stores an image input from the television camera 7 in a built-in image memory, and
0 is displayed as a still image on the screen.

The monitoring apparatus shown in FIG. 7 having the above configuration operates as follows.

The illumination light emitted from the light source 4 is converted into a parallel light by the collimator lens 5, reflected by the Hermirror 6, and vertically incident on the printed matter 1. The light incident on the printed matter 1 is specularly reflected, transmitted through the half mirror 6, and incident on the television camera 7.

As described above, the illumination light is radiated coaxially, and is specularly reflected on the printed matter 1 and thereafter enters the television camera 7. For this reason, an image is captured so that a glossy portion such as gold or silver is raised.

[0015]

Generally, when a printed matter having a high light reflectance is imaged by a camera using a strobe or continuous light, halation occurs, and a problem occurs in that a printed pattern cannot be accurately imaged.

Further, since the camera lens itself reflects off the subject, there is a problem that the camera lens is reflected in the captured image.

[0017] As in the monitoring apparatus shown in Fig. 7, the collimator lens generates parallel light, and the reflected light from the subject enters the television camera via the half mirror to avoid these problems to some extent. Is possible.

However, the collimator lens has a disadvantage that the irradiation area is small, and therefore, only a small visual field can be secured.

That is, in general, the maximum diameter of the collimator lens is 80 mm, and therefore, only a field of view having a maximum diameter of 80 mm can be secured. Furthermore, this diameter 8
If a rectangular visual field is to be secured from a 0 mm visual field, only a smaller visual field can be secured. Normally, the field of view required in a printed matter monitoring device is 160 mm × 12
It is 0 mm, and if a collimator lens is used as in the monitoring device shown in FIG. 7, it is impossible to secure a field of view of 160 mm × 120 mm.

In addition, the collimator lens is extremely expensive, and the manufacturing cost of a monitoring device using the collimator lens must increase.

Further, when an image is picked up by using illumination light from a collimator lens, there is a problem that coloring is poor.

Further, the biggest problem with the use of a collimator lens is that the collimator lens is suitable for imaging a glossy portion such as a transparent varnish, but is not suitable for printed matter having a surface with a higher light reflectance. Is not suitable, and when such printed matter is imaged using a collimator lens, problems such as halation and reflection of a camera lens still occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has an image pickup apparatus that enables a printed matter having a high light reflectance to be imaged in the same manner as a real object by using means instead of a collimator lens. It is intended to provide a device.

[0024]

According to the present invention, there is provided an optical film having a surface light source and a prism pattern formed on a surface thereof. At least one optical film that converts light into parallel light, a half mirror that reflects parallel light to a subject in parallel with the visual axis, and imaging means that receives light reflected from the subject and captures an image of the subject. An imaging device is provided.

The optical film has the same function as a prism, and converts plane light emitted from a surface light source into parallel light. A part of the parallel light is reflected by the half mirror, further reflected by the subject, and then imaged by the imaging means.
As described above, according to the imaging apparatus, it is possible to capture an image even on a printed matter having a surface with high light reflectance.

According to a second aspect of the present invention, it is preferable that the image pickup apparatus further includes a light absorber that is disposed on a side of the half mirror opposite to the surface light source and absorbs light transmitted through the half mirror. .

With this light absorber, irregular reflection of light in the vicinity of the half mirror can be prevented, and the imaging means can be prevented from capturing an image other than the subject.

The surface light source may be, for example, a tubular halogen lamp, a reflecting mirror disposed behind the halogen lamp, and a diffuser for diffusing light emitted from the halogen lamp. And can be composed of

Further, as described in claim 4,
The imaging device can include two optical films.
In this case, these two optical films are such that the surfaces on which the prism patterns are formed both face the surface light source, and the directions in which the prisms constituting the prism patterns in each optical film extend are orthogonal to each other. Is placed.

Alternatively, as described in claim 5, the optical film closer to the surface light source is disposed so that the surface on which the prism pattern is formed faces the surface light source,
The other optical film is arranged such that the surface opposite to the surface on which the prism pattern is formed faces the surface light source,
Further, these two optical films can be arranged such that the directions in which the prisms constituting the prism pattern in each optical film extend are orthogonal to each other.

[0031]

FIG. 1 is a schematic diagram showing the configuration of an imaging device 20 according to one embodiment of the present invention.

The image pickup device 20 according to the present embodiment includes a surface light source 21, an optical film 22 having a prism pattern formed on the surface thereof, and converting light emitted from the surface light source 21 into parallel light. And a half mirror 24 that reflects part of the parallel light to the subject 23 in parallel with the visual axis and transmits the remaining parallel light, and an imaging unit that receives the light reflected from the subject 23 and captures an image of the subject 23. Two-dimensional CCD camera 25, half mirror 24 and two-dimensional CCD
The two-dimensional CCD camera 25 is disposed between the
And a light absorber 27 disposed on the half mirror 24 on the opposite side of the surface light source 21 to absorb light transmitted through the half mirror 24. .

The subject 23 is a printed matter in which the same pattern is repeatedly printed, and each pattern includes a portion having a large light reflectance such as gold or silver. That is, the subject 23 corresponds to the printed matter 1 in the monitoring device shown in FIG.

For example, the subject 23 includes a medicine bag, a tablet package, an aluminum vapor-deposited film for keeping warm or cool, and the like.

The subject 23 is traveling in the direction of arrow A by a transport roller or other transport means (not shown).

The surface light source 21 includes a tubular xenon (Xe) lamp 21a, a curved reflecting mirror 21b disposed behind the xenon lamp 21a, an opal glass 21c disposed in front of the xenon lamp 21a, and an opal glass. And two opal acrylics 21d arranged adjacent to the glass 21c.

The opal acrylic 21d has a cloudy color and has a property of diffusing incident light. That is, when light emitted from a point or line light source passes through the opal acrylic 21d, the light is changed to planar light. For this reason, the light emitted from the tubular xenon lamp 21a, which is a line light source, passes through the opal acrylic 21d and becomes flat light as if emitted from a surface light source.

However, since the opal acrylic 21d has low heat resistance, the opal glass 21c having a large heat resistance is provided between the xenon lamp 21a and the opal acrylic 21d in order to prevent the opal acrylic 21d from the heat generated by the xenon lamp 21a. Are located.

FIG. 2 is a perspective view of the optical film 22.

The optical film 22 includes a polyester film 22a and a prism pattern 22b made of an acrylic resin formed on the polyester film 22a, and has the same characteristics as the prism.

In the optical film 22 shown in FIG. 2, all the prisms constituting the prism pattern 22b have the same shape and are arranged at equal intervals, but the shape of the prism pattern 22b is It is not limited to this.

For example, as shown in FIG. 3, it is not necessary that all the prisms constituting the prism pattern 22b have the same shape. For example, each prism may have a different height, or each prism may have a different base length. Further, the interval between the prisms does not need to be constant.

As such an optical film 22, for example, there is a film sold by Sumitomo 3M Limited under the name of "3M BEF brightness increasing film".

The optical film 22 has a prism pattern 2
It has a property that light incident from the 2b side is emitted as parallel light from the polyester film 22a side.

In the image pickup device 20 according to the present embodiment, the optical film 22 is disposed so that the prism pattern 22b faces the direction of the surface light source 21. For this reason, the irradiation light, which has become plane light from the xenon lamp 21a, which is a line light source, passes through the opal acrylic 21d, passes through the optical film 22, and becomes parallel light.

The half mirror 24 is an ordinary half mirror generally used, and is arranged at an angle of 45 degrees with respect to the optical axis of the light irradiated from the optical film 22. Part of the irradiation light from the optical film 22 is reflected by the half mirror 24 and reaches the subject 23. The remaining irradiation light passes through the half mirror 24 and reaches the light absorber 27.

The surface of the light absorber 27 is coated with black body furnace paint or matte black paint. For this reason,
The light that has reached the light absorber 27 is absorbed by the black paint applied to its surface and is not reflected.

The imaging device 20 according to the present embodiment having the above-described structure performs the following operation.

Light emitted from a tubular xenon (Xe) lamp 21a as a line light source passes through an opal glass 21c, is diffused by an opal acrylic 21d, and becomes plane light.

When the plane light passes through the optical film 22, as described above, the optical film 22 has a property of converting incident light into parallel light. Emit.

A part of the parallel light from the optical film 22 is reflected by the half mirror 24 and reaches the subject 23. The remaining parallel light passes through the half mirror 24,
The light reaches the light absorber 27 and is absorbed by the light absorber 27.

The light absorber 27 absorbs light transmitted through the half mirror 24, thereby preventing irregular reflection near the half mirror 24. If the light absorber 27 is not installed, the component color of the paint applied to the object placed at the place where the light absorber 27 is arranged is reflected by the half mirror 24 due to irregular reflection occurring near the half mirror 24. Thus, the component color may be imaged by the two-dimensional CCD camera 25. However, by disposing the light absorber 27 on the opposite side of the surface light source 21 with respect to the half mirror 24, the two-dimensional CCD camera 25 Imaging of component colors can be prevented.

The parallel light reflected by the half mirror 24 and reaching the subject 23 is further reflected by the subject 223, passes through the half mirror 24, passes through the dustproof glass 25, and reaches the two-dimensional CCD camera 25. .

The two-dimensional CCD camera 25 captures an image of the subject 23 by the reflected light from the subject 23.

The image of the subject 23 captured by the two-dimensional CCD camera 25 is processed, for example, by the image processing circuit 9 of the monitoring apparatus shown in FIG.
0 is displayed as a still image on the screen.

As described above, according to the imaging device 20 of the present embodiment, the optical film 22 having the same function as the prism is used instead of the collimator lens used in the conventional imaging device. The plane light from the light source 21 is made parallel light.

The collimator lens has a drawback that the irradiation area is small, and therefore, only a small visual field can be secured. However, unlike the collimator lens, the size of the optical film 22 in this embodiment is not limited, Can be taken. For this reason, the collimator lens cannot secure a field of view of 160 mm × 120 mm as a field of view normally required in a printed matter monitoring apparatus. However, according to the imaging apparatus 20 according to the present embodiment, such a field of view cannot be ensured. Can be secured.

Further, since it is not necessary to use an expensive collimator lens, the manufacturing cost of the imaging device can be greatly reduced.

Further, the collimator lens is suitable for imaging a glossy portion such as a transparent varnish, but is not suitable for printed matter having a surface having a higher light reflectance.
When such a printed matter is imaged using a collimator lens, problems such as halation and reflection of a camera lens have occurred. However, according to the imaging device 20 according to the present embodiment, such a large light reflectance is obtained. It is possible to image the printed matter in the same way as the real thing. For this reason, by configuring the camera of the printing still image apparatus using the imaging apparatus 20 according to the present embodiment, it is possible to monitor a printed matter having a high light reflectance, which was not possible in the past.

In the imaging device 20 according to the present embodiment, since the surface light source 21 can be used,
Unlike a point light source such as a strobe light used in the conventional imaging apparatus shown in FIG.
It is possible to perform imaging closer to the actual color.

As described above, the optical film 22 has a property of converting incident light into parallel light. This property will be further described below with reference to FIG.

FIG. 4A is a front view of the optical film 22 viewed from the direction X (see FIG. 2) in which each prism in the prism pattern 22b extends, and FIG.
Optical film 2 viewed from a direction Y (see FIG. 2) orthogonal to
FIG. 2 is a side view of FIG.

As shown in FIG. 4A, the optical film 2
The light incident on 2 is emitted as parallel light 31 when viewed from the X direction.

On the other hand, as shown in FIG.
Light incident on the optical film 22 is emitted so as to spread right and left when viewed from the Y direction.

By utilizing such properties of the optical film 22, the function of the imaging device 20 according to the above-described embodiment can be improved.

That is, in the imaging device 20 according to the above-described embodiment, one optical film 22 is used, but by utilizing the above-described properties of the optical film 22,
It is also possible to use two optical films.

FIG. 5 shows a first arrangement example when two optical films are used.

In the first arrangement example shown in FIG. 5, the two optical films 22A and 22B are both arranged such that the prism pattern 22b faces the surface light source 21. Furthermore, the two optical films 22A and 22B are arranged so that the direction in which each prism constituting the prism pattern 22b in each of the optical films 22A and 22B extends, that is, the direction X is orthogonal to each other.

As described above, the two optical films 22A,
By arranging 22B such that the directions X are orthogonal to each other, it becomes possible to change the plane light emitted from the surface light source 21 to parallel light while expanding the plane light to a larger plane.

FIG. 6 shows a second arrangement example when two optical films are used.

In the second arrangement example shown in FIG. 6, of the two optical films 22A and 22B, the first optical film 22A closer to the surface light source 21 is the prism pattern 2A.
2b is disposed so as to face the surface light source 21, and the other second optical film 22B is a polyester film 2B.
2a is arranged so as to face the surface light source 21. Further, the two optical films 22A, 22B are formed by the prism patterns 22 on the respective optical films 22A, 22B.
direction in which each prism constituting b extends, that is,
They are arranged such that directions X are orthogonal to each other.

According to the second arrangement example as shown in FIG. 6, similar to the first arrangement example shown in FIG. 5, the plane light emitted from the surface light source 21 is expanded into a larger plane to form a parallel light. It is possible to change to

[0073]

As described above, according to the imaging apparatus of the present invention, a surface light source is formed by using an optical film having the same function as a prism instead of the collimator lens used in the conventional imaging apparatus. Is converted into parallel light. The collimator lens has a small illuminated area, and therefore has a field of view that is usually required in a print monitor.
A visual field of 60 mm × 120 mm could not be secured. On the other hand, the size of the optical film in the imaging device according to the present invention is not limited, and can be any size. Therefore, such a visual field can be secured.

Further, since it is not necessary to use an expensive collimator lens, it is possible to greatly reduce the manufacturing cost of the imaging device.

Further, although the collimator lens is suitable for imaging a glossy portion such as a transparent varnish, it is not suitable for a printed matter having a surface having a higher light reflectance than the collimator lens. According to the method described above, it is possible to capture an image of such a printed matter having a large light reflectance in the same manner as the real thing. For this reason, it is possible to monitor a printed matter having a high light reflectance, which was impossible in the related art.

In the imaging device according to the present invention,
Since it is possible to use a surface light source, unlike a point light source such as a strobe used in the conventional image pickup device shown in FIG. It is possible to do.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an imaging device according to an embodiment of the present invention.

FIG. 2 is a perspective view of an optical film in the imaging device shown in FIG.

FIG. 3 is a perspective view showing another example of the optical film.

FIG. 4 is a front view (A) and a side view (B) showing the properties of an optical film.

FIG. 5 is a side view showing a first arrangement example of two optical films.

FIG. 6 is a side view showing a second arrangement example of two optical films.

FIG. 7 is a schematic diagram illustrating an example of a conventional imaging device.

[Explanation of symbols]

 20 Imaging device according to one embodiment of the present invention 21 Surface light source 21a Xenon lamp 21b Reflector mirror 21c Opal glass 21d Opal acrylic 22 Optical film 22a Polyester film 22b Prism pattern 23 Subject 24 Half mirror 25 Two-dimensional CCD camera 26 Dustproof glass 27 Light Absorber

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/225 H04N 5/225 CF term (Reference) 2G051 AA34 AB11 BB03 BB07 BB11 BB20 CA03 CB01 CC20 DA06 EA11 EA12 2H042 BA01 BA16 CA12 CA17 5C022 AA01 AA14 AB13 AB15 AB45 AC42 CA07 5C054 AA07 CA04 CC02 CC05 CE08 CH01 EA01 ED07 FB03 HA01 HA03

Claims (5)

[Claims] 1. A surface light source, an optical film having a prism pattern formed on a surface thereof, at least one optical film for converting light emitted from the surface light source into parallel light, An image pickup apparatus comprising: a half mirror that reflects light from a subject in parallel with the image capturing device; and an image pickup unit that receives light reflected from the subject and captures an image of the subject. 2. The imaging device according to claim 1, further comprising a light absorber disposed on a side of the half mirror opposite to the surface light source and absorbing light transmitted through the half mirror. 3. The surface light source includes: a tubular halogen lamp; a reflector disposed behind the halogen lamp; and a diffusion plate for diffusing light emitted from the halogen lamp. 3. The method according to claim 1, wherein
An imaging device according to claim 1. 4. The image pickup apparatus includes two optical films, and the two optical films are formed such that both surfaces on which the prism patterns are formed face the surface light source, and each of the optical films The imaging device according to any one of claims 1 to 3, wherein the plurality of prisms are arranged such that directions in which the prisms constituting the prism pattern extend are orthogonal to each other. 5. The imaging device includes two optical films, and the optical film closer to the surface light source is:
The surface on which the prism pattern is formed is arranged so as to face the surface light source, and the other optical film is arranged such that the surface on the opposite side to the surface on which the prism pattern is formed faces the surface light source. The two optical films are arranged so that the directions in which the prisms constituting the prism pattern in each optical film extend are orthogonal to each other. The imaging device according to claim 1.