JP4958492B2 - Image reader - Google Patents

Description

  The present invention relates to an image reading apparatus used for confirming a printing unit of a medium in which a transparent hologram film is pasted on a printing unit, such as a banknote, a gift certificate, or a certificate.

  Japanese Unexamined Patent Application Publication No. 2005-33589 is an example of this type of image reading apparatus that has been generally used. The image reading apparatus described in this publication irradiates a medium such as a banknote with light from LEDs linearly arranged in a housing, and images light reflected by the medium with a CCD. Such an apparatus is used for authenticity determination of bills and the like.

JP 2005-33589 A

  However, in recent years, for security purposes, media with a transparent hologram film affixed on prints and prints have emerged, and simply by imaging such media, the hologram appears in the image and Although it can be confirmed, it has been extremely difficult to image the print or printed portion under the hologram.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus that can clearly image a printing portion under a hologram film.

  An image reading apparatus according to the present invention includes a line-type imaging device for imaging a medium having a transparent hologram film attached on a printing unit, and an illumination arranged in a line parallel to an imaging line passing on the medium. Means, a first polarizing plate disposed in front of the illuminating means and polarizing the light emitted from the illuminating means, and disposed between the illuminating means and the line-type imaging device, and polarizes the light reflected by the medium. A second polarizing plate, the first polarizing plate having a first polarization transmission axis substantially perpendicular to the imaging line, and the second polarizing plate being substantially parallel to the imaging line. It has two polarization transmission axes.

  In observing the printed portion under the hologram film, the image reading apparatus according to the present invention includes a first polarizing plate disposed in front of the line-shaped illumination means, and the illumination means and the line-type imaging device. An arranged second polarizing plate is used. In this case, by specifying the direction of the first polarization transmission axis of the first polarizing plate and the direction of the second polarization transmission axis of the second polarizing plate, respectively, the printed portion under the hologram film is very clearly specified. It has been confirmed by experiments that images can be clearly captured. As a result of the experiment, the first polarizing plate has a first polarization transmission axis extending in a direction substantially perpendicular to the imaging line, and the second polarizing plate extends substantially parallel to the imaging line. If the second polarization transmission axis is provided, the hologram can be lost at the time of imaging, whereby the characters and the image pattern of the printing unit can be reliably confirmed.

  The second polarization transmission axis is preferably in the range of 85 ° to 95 ° with respect to the first polarization transmission axis. The second polarization transmission axis does not need to be strictly orthogonal to the first polarization transmission axis, and the initial purpose can be achieved even if they intersect within this range.

  The incident angle of the illumination means is preferably 25 ° to 35 ° with respect to the imaging optical axis passing through the imaging line. This angle is an angle at which the illumination is difficult to be reflected on the image sensor.

  Further, the hologram film is preferably capable of observing the hologram from a direction of 360 degrees, that is, from any direction, the printing part is color printing, and the illumination means is preferably white LEDs arranged linearly on the substrate. is there. When the hologram film and the printing part are under such conditions, the printed part can be projected most vividly by using a white LED.

  According to the present invention, it is possible to capture a clear image of the printed portion under the hologram film.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an image reading apparatus according to the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, a security part G is provided on a medium (for example, banknotes, gift certificates, certificates, passports, etc.) A, and this security part G has a printing section S printed or printed. A transparent hologram film H is pasted thereon. The image reading apparatus 1 is used for confirming characters and image patterns in the printing unit S of the security part G having the above-described configuration. The transmissive hologram film H changes the color of the hologram depending on the viewing angle or becomes transparent, and the hologram can be observed from a direction of 360 degrees, that is, from any direction. Image patterns and characters.

  As shown in FIGS. 2 and 3, the image reading apparatus 1 is disposed below the three rows of conveying rollers arranged in parallel, and the casing 2 is formed flat because the lower portion of the conveying roller rows 3 is a narrow space. ing. A rectangular imaging window 4 extending in a direction orthogonal to the conveyance direction B is formed in the housing 2, and a dustproof glass 9 is fitted in the imaging window 4. The imaging window 4 has a length sufficient to ensure the entire length of the imaging line L (see FIG. 4) extending corresponding to the imageable portion of the line-type CCD (imaging device) 10. ing. Note that the imaging line L is a linear virtual line extending on the surface of the medium A, and the imaging element 10 may be a CMOS.

  Further, a pair of first and second illumination means 5 and 6 extending in parallel with the imaging window 4, that is, in parallel with the imaging line L, are arranged in the housing 2. The mounting boards 5a and 6a of the illumination means 5 and 6 are fixed to the housing 2 and extend in parallel with the imaging line L. A plurality of white LEDs 5b, 6b arranged in a line in parallel with the imaging line L are fixed on the surface of each mounting substrate 5a, 6a, and each LED 5b, 6b emits light toward the imaging window 4. .

  One illuminating means 5 and the other illuminating means 6 are in a mirror-symmetrical relationship with respect to the planar imaging optical axis P1 perpendicular to the transport direction B and extending through the imaging line L. , 6 has an incident angle α of 25 ° to 35 ° with respect to the imaging optical axis P1. In this way, by irradiating the medium A with light from an oblique direction, reflection of illumination light by the CCD 10 is appropriately prevented. In addition, the use of two rows of illumination means 5 and 6 also increases the amount of light.

  Between the mounting boards 5a and 6a of the illumination means 5 and 6, a long and narrow gap is formed so as to allow the imaging optical axis P1 to pass therethrough. The light reflected by the medium A is reflected toward the side wall 2b of the housing 2 by the first reflecting mirror 7 fixed to the bottom wall 2a of the housing 2, and this reflected light is reflected on the side wall 2b of the housing 2. Reflected toward the CCD 10 by the fixed second reflecting mirror 8. The CCD 10 and the second reflecting mirror 8 face each other in the housing 2, thereby making it possible to extend the optical path and flatten the housing 2. In front of the CCD 10, an image forming lens group 12 for appropriately making the light reflected by the second reflecting mirror 8 incident on the line CCD 10 is disposed.

  Further, as shown in FIGS. 2 to 4, the light emitted from the illumination means 5, 6 is used to achieve confirmation of only the printing part S of the security part G provided on the medium A by the line-type CCD 10. A first polarizing plate 20 is disposed in front of the illumination means 5 and 6. Specifically, the 1st polarizing plate 20 is affixed on each LED5b and 6b so that the light emission surface of LED5b and 6b of each illumination means 5 and 6 may be covered. Further, a second polarizing plate 30 is disposed between the illumination means 5 and 6 and the line CCD 10. Specifically, the second polarizing plate 30 is attached to the front surface of the CCD 10 between the imaging lens group 12 and the CCD 10. It is also possible to arrange the second polarizing plate 30 in front of the imaging lens group 12.

  Further, as shown in FIG. 5, the first polarizing plate 20 has a first polarization transmission axis 20a extending substantially perpendicular to the imaging line L, and as shown in FIG. The polarizing plate 30 has a second polarization transmission axis 30 a extending substantially parallel to the imaging line L. In this case, the second polarization transmission axis does not necessarily need to be orthogonal to the first polarization transmission axis 20a, and the initial purpose can be achieved as long as it is within the range of 85 ° to 95 °.

Next, the operation of the image reading apparatus 1 will be briefly described.
As shown in FIG. 4, the white light emitted from the LEDs 5 b and 6 b passes through the first polarizing plate 20 and is applied to the security portion G of the medium A. At this time, the P wave is cut by the first polarizing plate 20, and only the S wave light is applied to the security portion G. When the security portion G is irradiated with light, S-wave light (diffracted light and regular reflection light) and diffuse reflection light are generated in the security portion G. This light is incident on the imaging lens group 12 via the first and second reflecting mirrors 7 and 8.

  The light emitted from the imaging lens group 12 passes through the second polarizing plate 30 and is incident on the line CCD 10. At this time, S-wave light is cut by the second polarizing plate 30, and only P-wave light enters the CCD 10, and the security portion G is imaged. The security portion G is imaged while the medium A is fed at a predetermined speed by the transport roller row 3.

  In the image reading apparatus 1 configured as described above, when observing the color printing portion S under the hologram film H, the first polarizing plate 20 disposed in front of the line-shaped illumination means 5 and 6, and the illumination means 5 6 and a second polarizing plate 30 disposed between the line-type CCD 10 are used. In this case, by specifying the direction of the first polarizing transmission axis 20a of the first polarizing plate 20 and the direction of the second polarizing transmission axis 30a of the second polarizing plate 30, respectively, the hologram film H is very clearly defined. It has been confirmed through experiments that the lower printing portion S can be clearly imaged. As a result of the experiment, the first polarizing plate 20 has a first polarization transmission axis 20a extending substantially perpendicular to the imaging line L, and the second polarizing plate 30 is relative to the imaging line L. By having the second polarization transmission axis 30a extending substantially in parallel, the hologram can be erased at the time of imaging, thereby ensuring confirmation of the printed characters and printed image pattern of the printing unit S on the monitor screen. Can be done.

  The experimental results of the image reading device 1 will be described below.

[Comparative Example 1]
As shown in FIGS. 7 and 8, regarding the first polarizing plate 20 and the second polarizing plate 30, unlike the present invention, the first polarizing plate 20 extends substantially parallel to the imaging line L. The second polarizing plate 30 has a second polarizing transmission axis 30a extending substantially orthogonal to the imaging line L. When the security portion G is imaged by the line CCD 10 under such a situation, as shown in FIG. 7, the hologram portion of the hologram film H is not seen on the monitor screen, and the printing portion S is affected by the hologram. It becomes extremely difficult to observe. This is also apparent from FIG. 13A showing the enlarged “N” of “NIPPON 1000”. Further, as shown in FIG. 8, in the imaging result, it can be seen that the average density around the hologram film H is 114.8 LSB, whereas the density at the location of the hologram film H is 220 LSB. Thus, a density difference is also seen on the graph, and it can be seen that the influence of the hologram remains when the security portion G is imaged.

[Comparative Example 2]
As shown in FIGS. 9 and 10, regarding the first polarizing plate 20 and the second polarizing plate 30, unlike the present invention, the first polarizing plate 20 extends substantially perpendicular to the imaging line L. The second polarizing plate 30 has a second polarization transmission axis 30 a extending at an angle of 45 ° with respect to the imaging line L. When the security portion G is imaged by the line CCD 10 under such circumstances, the hologram portion of the hologram film H is slightly transparent on the monitor screen as shown in FIG. It becomes difficult to observe due to the influence of This is also apparent from FIG. 13 (b) showing the enlarged “N” of “NIPPON 1000”. Further, as shown in FIG. 10, in the imaging result, it can be seen that the average density around the hologram film H is 95.4LSB, whereas the density at the location of the hologram film H is 175LSB. Thus, a density difference is also seen on the graph, and it can be seen that the influence of the hologram remains when the security portion G is imaged.

[Example]
As shown in FIGS. 11 and 12, with respect to the first polarizing plate 20 and the second polarizing plate 30, the first polarizing plate 20 extends substantially orthogonal to the imaging line L. The second polarizing plate 30 has a polarization transmission axis 30 a that has a polarization transmission axis 20 a and extends substantially parallel to the imaging line L. When the security portion G is imaged by the line CCD 10 under such circumstances, the hologram portion of the hologram film H is completely transparent as shown in FIG. 11, and the printing portion S is not affected by the hologram. It is possible to observe, and the printed characters and printed image patterns of the printing unit S can be found reliably on the monitor screen. This is also apparent from FIG. 13C showing the enlarged “N” of “NIPPON 1000”. Further, as shown in FIG. 12, in the imaging result, the average density around the hologram film H is 119.7LSB on the graph, and the density at the location of the hologram film H is also the same as the surrounding density. It can be seen that the influence of the hologram disappears when G is imaged.

It is a perspective view which shows an imaging medium. 1 is a cross-sectional view showing an image reading apparatus according to the present invention. It is sectional drawing which follows the III-III line of FIG. 1 is a perspective view schematically showing an image reading apparatus according to the present invention. It is a perspective view which shows the direction of a 1st polarization transmission axis. It is a perspective view which shows the direction of a 2nd polarization transmission axis. 10 is a plan view showing an image according to Comparative Example 1. FIG. 10 is a graph showing a concentration distribution in Comparative Example 1. 10 is a plan view showing an image according to Comparative Example 2. FIG. 10 is a graph showing a concentration distribution in Comparative Example 2. It is a top view which shows the image imaged with the image reader concerning this invention. It is a graph which shows concentration distribution in an embodiment. It is a figure which shows an experimental result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image reader 5, 6 ... Illuminating means, 5a, 6a ... Board | substrate, 5b, 6b ... LED, 10 ... CCD (imaging element), 20 ... 1st polarizing plate, 20a ... 1st polarized light transmission axis, DESCRIPTION OF SYMBOLS 30 ... 2nd polarizing plate, 30a ... 2nd polarized light transmission axis, A ... Medium, S ... Printing part, H ... Hologram film, P1 ... Imaging optical axis, L ... Imaging line, (alpha) ... Incident angle.

Claims (4)

A line-type imaging device for imaging a medium having a transparent hologram film affixed on the printing unit;
Illuminating means arranged in a line parallel to the imaging line passing on the medium;
A first polarizing plate disposed in front of the illuminating means and polarizing light emitted from the illuminating means;
A second polarizing plate disposed between the illuminating means and the line-type imaging device and polarizing light reflected by the medium;
The first polarizing plate has a first polarization transmission axis that is substantially perpendicular to the imaging line, and the second polarizing plate is a second polarization transmission axis that is substantially parallel to the imaging line. An image reading apparatus comprising:   The image reading apparatus according to claim 1, wherein the second polarization transmission axis is within a range of 85 ° to 95 ° with respect to the first polarization transmission axis.   The image reading apparatus according to claim 1, wherein an incident angle of the illumination unit is 25 ° to 35 ° with respect to an imaging optical axis passing through the imaging line. The hologram film is capable of observing a hologram from a direction of 360 degrees, the printing unit is color printing, and the illumination unit is a white LED linearly arranged on a substrate. Item 2. The image reading device according to Item 1.

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