JPS61250854A - Reproducing device for optical card - Google Patents

Abstract

PURPOSE:To improve the output characteristic and the defocus characteristic by increasing the image forming performance of a line sensor in the arranging direction of a photodetector cell more than the image forming performance in the direction orthogonal to the arranging direction so as to decrease the incident angle of light and the reflection angle of light from an optical recording medium to the line sensor. CONSTITUTION:An optical recording medium 2 is provided to an optical card 1, and in order to reproduce the information recorded on the optical recording medium 2, a light source 3 such as a light emitting diode irradiating a lighting light and the line sensor 4 receiving a reflected light from the recording medium face, so-called read light, are provided. In order to form the image of the read light on a photodetection part 5 of the line sensor 4, an image forming lens 6 is arranged between the optical card 1 and the line sensor 4. In the image forming lens 6, the image forming performance in the arranging direction Z of a photodetector cell S of the line sensor 4 is increased more than that in the direction X orthogonal to the direction Z.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical card reproducing device for reproducing recorded information on an optical recording medium provided on an optical card.

[Summary of the invention]

The present invention provides an optical card reproducing apparatus that irradiates light from a light source onto an optical recording medium of an optical card and receives the reflected light with a line sensor to reproduce recorded information. For the imaging lens installed between the line sensor and the line sensor, the imaging performance in the direction in which the light receiving cells of the line sensor are arranged is higher than the imaging performance in the direction perpendicular to the arrangement direction. The purpose of this is to reduce the angle of incidence of light on the recording medium and the angle of reflection of light from the optical recording medium toward the line sensor, thereby improving output characteristics, defocus characteristics, and the like.

[Conventional technology]

Generally, bank cards, credit cards.

2. Description of the Related Art Optical cards or so-called optical cards are known that use an optical recording medium as a data recording medium in identification cards, other memory cards, and the like.

This optical card generally has a configuration as shown in FIG. 10, and a strip-shaped optical recording medium 102 is provided on a substrate of a rectangular optical card 101 in parallel to the longitudinal direction X of the card. A plurality of trunks T are parallel to each other in a direction Z orthogonal to the longitudinal direction X of this optical recording medium 102.
is recorded and formed on the optical recording medium 102. In these valley tracks T, information signals are optically readably recorded as a so-called array of pits P, as shown in the first figure.

A reproducing device for reproducing information signals recorded on the optical recording medium 102 of such an optical card 101, a so-called optical card reader, has a schematic configuration as shown in FIG. 12. In FIG. 12, light emitted from a light source 103 such as a light emitting diode or a lamp is collected by a condenser lens 108, and is transmitted to an optical recording medium of an optical card 101 via a cylindrical lens 109 as necessary. 102 is irradiated. Here, a transparent protective film 110 made of transparent resin or the like is provided on the surface of the optical recording medium 102 of the optical card 101, and the irradiation light is directed in a normal direction perpendicular to the surface of the transparent protective film 110. The light is incident at a predetermined incident angle θ with respect to Y, is reflected by the surface of the optical recording medium 102, and is emitted from the surface of the transparent protective film 110 at a reflection angle θ equal to the above incident angle. This reflected light, that is, the reading light of the track T, is received by the line sensor j-104 via the imaging lens 106.

As shown in FIG. 13, the light receiving section 105 of the line sensor 104 has a plurality of cells serving as light receiving units, so-called photo cells or light receiving cells S arranged in a line in the direction of arrow Z parallel to the track T. It is composed of Then, the imaging lens 106 moves one track T consisting of a row of pillars recorded on the optical recording medium 102 of the optical card 101 to the light receiving section 10 of the line sensor 104.
The line sensor 104 electrically scans each party optical cell S to form a pit image IP on the track T.
The electric signal detected by the image IP is extracted and the information is reproduced.

[Problem that the invention seeks to solve]

Incidentally, it is preferable that the incident angle θ of light from the light source 103 to the optical card 101 and the reflection angle θ of light toward the line sensor 104 are smaller.

This is because information recorded on the optical recording medium 102 is reproduced through the transparent protective film 110 provided on the surface of the optical card 101, so when the angle θ is increased, so-called coma aberration increases. Line sensor 10
This is because the contrast of the image on 4 deteriorates and there is less margin when defocusing.

On the other hand, for the imaging lens 106, one track T (length of several mm to several mm) of the optical card 101 is used.
The light receiving part 10 of the line sensor 104 without distortion or magnification variation.
5, a lens with a large aperture and wide field of view is required.

For this reason, if an attempt is made to reduce the angle θ, the end outer frame of the imaging lens 106 will partially block the illumination light from the light source 103, so θ cannot be made too small. Problems such as comatic aberration and defocus margin cannot be solved.

In particular, in the case of an optical card recording and reproducing device that not only reproduces information but also records information at the same time, a recording laser beam or the like is directed onto the optical recording medium 102 of the card from the direction of the arrow Y in FIG. Since it is necessary to make the light incident, the arrangement position of the imaging lens 106 is further restricted by this recording optical system, and the above-mentioned angle θ has to become large.

In view of these conventional circumstances, the present invention aims to improve the angle of incidence, An object of the present invention is to provide an optical card reproducing device that can reduce the reflection angle θ and improve output characteristics, telefocus characteristics, and the like.

[Means for solving problems]

An optical card playback device according to the present invention includes an optical card provided with an optical card, a light source for irradiating the optical recording medium with illumination light, and receiving reflected light from the optical recording medium. a line sensor for reproducing information recorded on the recording medium; and a lens for focusing the reflected light on the line sensor, the lens configured to receive light from the line sensor. It is characterized in that the imaging performance in the cell arrangement direction is higher than the imaging performance in a direction perpendicular to the arrangement direction.

[For production]

By providing anisotropy to the imaging performance of the imaging lens and shortening the width of the imaging lens in the direction perpendicular to the arrangement direction of the line sensor's light receiving cells, 1. Can be made smaller.

〔Example〕

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic perspective view showing an embodiment of the present invention. In FIG. 1, an optical device 1 is provided with an optical recording medium 2 as described above.

In order to reproduce information recorded on this optical recording medium 2, a light source 3 such as a light emitting diode that emits illumination light, and a line sensor 4 that receives reflected light from the surface of the recording medium, so-called reading light, are provided. ing. In order to image this reading light onto the light receiving section 5 of the line sensor 4, an imaging lens 6 is provided between the optical card 1 and the line sensor 4.
This imaging lens 6 enhances the imaging performance in the arrangement direction Z of the light receiving cells S of the line sensor 4 than the imaging performance in the direction X perpendicular to this direction Z. There is. Specifically, as shown in FIG. 2, the length 2a of the lens 6 in the Z direction is longer than the length 2b in the X direction.
2 l:l) is formed. 5. For example, for a circular lens made of glass or transparent plastic, both ends in the X direction (shaded areas in Figure 2) are removed, or the external shape shown in Figure 2 is created from the beginning. The lens 6 having a substantially rectangular front shape may be formed by molding using a mold or the like.

When using the imaging lens 6 having such a shape, N8,
In other words, the numerical aperture is the value NAz in the Z direction and the value NA in the X direction.
NAz=a/f NAx21)/f where f causes anisotropy of the numerical aperture NN, like the focal length of a lens.

Here, the numerical aperture NN of the lens generally limits the spatial frequency band transmitted to □ when forming an image.

Therefore, when a row of pits P as shown in FIG. 8 is imaged using the imaging lens 6 having anisotropy in numerical aperture NA as described above, The light intensity distribution of the pit image IP on the surface of the light receiving section 5) is as follows:
It is schematically represented as shown in FIG. In other words, the Z direction,
The light intensity distribution in the directions is like the curves Iz and Ix in Fig. 5, and the end shape of the intensity distribution curve Iz in the Z direction is steeper than the end shape of the intensity distribution curve Ix in the X direction. It has a slope, and the so-called "sag" or "waveform rounding" is small.

Note that when a conventional circular imaging lens is used, the light intensity distribution of the image with respect to the row of the above-mentioned bits P is schematically shown in Figure 6, and the light intensity distribution for one bit image is As shown in FIG. 7, the intensity distribution appears as curves Iz and Ix that are equal in both the Z and X directions. However, when a circular lens with a diameter of 2a is used, there is a disadvantage that the angle θ becomes larger than when using the imaging lens 6 with a length of 2b in the X direction in FIG. This is as stated above.

By the way, the optical recording medium 2 is detected by the line sensor 4.
When reading out the pinot l-P of the I/rack T recorded in the track T, the light intensity distribution in the longitudinal direction of the track T or in the direction of the arrow Z, which is the direction in which the light receiving cells S are lined up, greatly affects the reproduced signal. Therefore, the influence of the light intensity distribution in the direction of arrow X on the reproduced signal is small.

Therefore, even when using an imaging lens 6 with a short length in the X direction and low imaging performance in the X direction as shown in FIG. 2, even if the imaging lens 6 has a long length in the Z direction and If the imaging performance is sufficiently high, problems such as distortion of the reproduced signal waveform and code amount interference can be avoided.
There is no risk of any influence occurring, and since the length in the X direction can be shortened, the incident angle θ of the illumination light from the light source 3 to the optical card 1 and the reflection angle θ to the line sensor 4 can be reduced.
can be made small, so-called coma aberration can be reduced, and output characteristics and defocus characteristics can be improved.

According to experiments conducted by the present inventors, the diameter of the pill l-P is 8
An optical card recorded with a pattern with a pitch of 16 μm and a magnification of 56 times and N8 (numerical aperture) in the Z direction is 0.
．． When reproduced using the imaging lens No. 17, the above a and b
It has been confirmed that even if the ratio is 4 (b/a = 1/4), signal reproduction can be performed with a sufficient SN ratio.

Furthermore, as shown in FIG. 1, regarding the support structure of the imaging lens 6, arcuate portions 6A and 6B at both ends in the Z direction:
If the lens 6 is configured to be held between the support frames 7A and 7B, the side 6C or 6D at the end of the lens 6 in the X direction can be brought as close as possible to the illumination light or the recording beam. This makes it possible to further reduce the angle θ.

Here, the minimum realizable value θml of the above angle θ when using a circular lens with a diameter of 2a, and the imaging lens 6 in FIG.
The difference △θ(
=19m1-θrn2) is approximately, however, dl is lens 6
According to this embodiment, the incident angle and reflection angle can be improved by about this Δθ.

This is particularly effective in the case of an optical card recording and reproducing device capable of not only reproducing but also recording, as in the second embodiment shown in FIG. That is, in FIG. 8, a laser beam LB for information recording is irradiated from a direction Y perpendicular to the surface of the optical recording medium 2 of the optical card 1. This laser beam LB is emitted from a laser light source such as a laser diode and is passed through an optical deflector 11.
The beam is deflected by the beam and is incident on the optical recording medium 2 via the objective lens 12. The imaging lens 6 has the same structure as in FIGS. 1 and 2, and the other configurations are also the same as in FIG. 1, so corresponding parts will be described with the same reference numerals. Omitted.

In the case of the second embodiment shown in FIG. 8, if the end of the imaging lens 6 blocks part of the recording laser beam LB, there is a risk that effective recording will not be possible. Conventionally, it was difficult to reduce the angle θ, but by using the imaging lens 6 shaped like this embodiment, the length of the lens in the X direction can be shortened, so the angle θ can be reduced. It can be made small, and the output characteristics and defocus characteristics of the line sensor 4 can be improved.

Furthermore, in an actual optical card reader, as in the third embodiment shown in FIG. The reflected light or reading light is reflected by the optical card 1 and made incident on the optical recording medium 2 of the optical card 1.
In many cases, the configuration is such that the light is reflected by a mirror 14 and received by the line sensor 4 via an imaging lens 6 having a substantially rectangular front shape as shown in FIGS. 1 and 2 described above.

When a conventional circular imaging lens is used as the mirror 14 used here, the width of the imaging beam in the X direction through the lens becomes a dog, and a correspondingly larger mirror is required. If the imaging lens 6 of this embodiment is used, the width of the imaging beam in the X direction can be reduced, and the width of the mirror 14 can also be reduced, which is effective in making the entire device thinner and smaller. 2. The present invention is not limited to the above-mentioned embodiments. For example, the pill-P may be formed into a circular shape, an oval shape, etc. other than a rectangular shape. Of course, the structure of the system or recording system is not limited to the illustrated example.

〔Effect of the invention〕

As for the external dimensions of the imaging lens, even if the length in the direction The angle of incidence of illumination light and the angle of reflection of reading light on the optical card can be reduced without any adverse effects, and the output characteristics and focus characteristics can be improved, which is effective in making the device thinner and smaller.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing one embodiment of the present invention, FIG. 2 is a schematic front view of an imaging lens, FIG. 3 is a schematic front view of a bit string, and FIGS. 4 and 5 are two embodiments. A diagram showing the light intensity distribution of Pino 1 to image by the imaging lens of the example, FIGS. 6 and 7 are diagrams showing the light intensity distribution of the pit image by the conventional circular imaging lens, and FIG. 8 is a diagram showing the light intensity distribution of the pit image by the conventional circular imaging lens. FIG. 9 is a schematic diagram showing a third embodiment of the present invention, FIG. 1-0 is a schematic front view showing an example of an optical card, and FIG.
Figure 1 is a schematic front view showing the bit string of track T;
The figure is a schematic diagram showing a conventional example. FIG. 18 is a schematic front view showing a light receiving section and a bit image of a line sensor. i, ioi...Optical card 2.102...Optical recording medium 3.103...Light source 4.104...Line sensor date 5,105
...... Light receiving section 6, IO2 ... Imaging lens T ......) Rack P
・・・・・・・・・・・・・・・・・・Pit S...
・・・・・・・・・・・・Light receiving cell A convex 1 P. Ntretsuji Nagita each JF plane view Figure 3 Ai East lens 61 Hanpi... Toy elephant IP light 5 Fish uniform -Shunzuya Figure 5 Bi・/l-I Elephant IP Old Intensity Minute Figure 6, Early XsI! The light intensity of the P. Toy IP 6 is shown by the Red Shins 6. Indicates the focus row, t! Shinagi IiE side view Figure 1I Twisted view showing the night visit Figure 12

Claims (1)

[Scope of Claims] An optical card provided with an optical recording medium, a light source for irradiating the optical recording medium with illumination light, and receiving reflected light from the optical recording medium and recording it on the recording medium. a line sensor for reproducing the received information; and a lens for forming an image of the reflected light onto the line sensor, the lens forming an image in the arrangement direction of the light-receiving cells of the line sensor. An optical card playback device characterized in that the performance is higher than the imaging performance in a direction perpendicular to the arrangement direction.