JP3145445B2 - Optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine-readable optical recording medium, and more particularly to an optical recording medium encoded and recorded by a hologram or a diffraction grating.

[0002]

2. Description of the Related Art Conventionally, it is well known in Japanese Patent Application Laid-Open No. 49-17152 to record code information according to the direction of a diffraction grating or the direction of interference fringes of a hologram. For example, as shown in FIG. 6, a recording body 1 recorded in the form of a hologram composed of a diffraction grating or parallel interference fringes.
When illumination light is applied from the normal direction, the light is diffracted, and the diffraction direction is a direction perpendicular to the direction of the grating or the interference fringes. Therefore, code information can be recorded by dividing the direction in which the grating or the interference fringe is oriented or the diffraction direction so as to correspond to the information. For example, as shown in FIG. 6, by dividing the diffraction direction into four and associating the reference numerals 1 to 4, any one of the four information can be recorded by one recording medium (in this case, Sign 1
Is recorded. ).

In order to read such a recording medium 1, photodetectors D1 to D4 for detecting diffracted light in respective diffraction directions are arranged, and recorded information is read from the number of the photodetector on which the diffracted light is incident. it can. Specifically, as shown in the perspective view of FIG. 7, for example, light from the light source 2 is condensed on the recording medium 1 by the lens 3 as necessary, and the diffracted light is directed obliquely above the recording medium 1. Photodetector D arranged so as to surround it
What is necessary is just to detect by 1-D4.

To increase the number of pieces of information that can be recorded by one recording medium, it is conceivable to increase the number of divisions and increase the number of photodetectors arranged for reading correspondingly. However, the error rate increases from the point of reading accuracy, which is not preferable. Actually, as shown in FIG. 6, it is practical to divide into about four directions.

In order to increase the number of pieces of recordable information, it is conceivable to record a plurality of diffraction gratings or holograms in an overlapping manner (multiplex recording). For example, when two diffraction gratings are overlapped, the number of records that can be performed by one recording medium is 10
(1 and 1, 2 and 2, 3 and 3, 4 and 4, 1
And 2, 1 and 3, 1 and 4, 2 and 3, 2 and 4, 3 and 4) In fact, in addition to the diffracted light by each diffraction grating, unnecessary diffraction due to the interaction of both diffraction gratings Light is generated in a direction different from the original diffraction direction, causing a reading error, and cannot be put to practical use.

In order to solve such a problem, instead of recording two diffraction gratings in a single recording medium in a multiplex manner, as shown in FIG. Japanese Patent Application Laid-Open No. 3-21096 proposes that the diffraction grating is divided into sub-divisions and different diffraction gratings are recorded between adjacent sections 4 and 5. Further, instead of subdividing the recording area into a grid pattern, the recording area may be subdivided into a honeycomb shape and recorded in the same manner.

[0007]

However, in these cases, as shown in FIG. 8, one recording area is divided by two groups of parallel straight lines 6 and 7 which intersect with each other. Is read by a reading device as shown in FIG. 7, as shown in FIG.
As a result, scattered light 8 is generated in a direction perpendicular to the direction, and if a diffraction grating diffracting in this direction is recorded, erroneous reading detected by the photodetectors D1 to D8 occurs.

The present invention has been made in view of such circumstances, and has as its object to separate two types of diffraction gratings or holograms having different directions of gratings or interference fringes into sections obtained by subdividing a recording area. The object of the present invention is to prevent the occurrence of erroneous reading due to scattering of light in a specific direction from the boundary of the arranged grating or interference fringe in the optical recording medium arranged in the above manner.

[0009]

An optical recording medium according to the present invention for achieving the above object is an optical recording medium which irradiates a light beam and reads information recorded according to the direction of diffracted light. In an optical recording medium in which a plurality of diffraction gratings or holograms with different directions or intervals of interference fringes are separately arranged in subdivided recording areas, the recording area is divided into a circle inside and outside by a large number of minute circles And one inside the circle
One or more diffraction gratings or holograms are arranged, and a different diffraction grating or hologram is arranged outside the circle, and the inner and outer diffraction gratings or holograms are adjacent to each other with the circle as a boundary. It is characterized by having.

[0010]

Another optical recording medium of the present invention is an optical recording medium for reading recorded information by irradiating a light beam with the direction of diffracted light, wherein the directions or intervals of gratings or interference fringes are different. In an optical recording medium in which a plurality of diffraction gratings or holograms are separately arranged in subdivided recording areas, the recording area is subdivided by a plurality of wavy lines, and adjacent diffraction gratings or holograms different from each other are arranged. And the diffraction gratings or holograms on both sides of the wavy line are adjacent to each other.

[0012]

In the present invention, the recording area is divided into a circle inside and outside by a number of minute circles, and one or a plurality of diffraction gratings or holograms are arranged inside the circle, and a different one is placed outside the circle. A diffraction grating or hologram is arranged, and its inner and outer diffraction gratings or holograms are adjacent to each other with the circle as a boundary, or the recording area is subdivided by a plurality of wavy lines and Since different diffraction gratings or holograms are arranged in different sections, and the wavy line is used as a boundary so that the diffraction gratings or holograms on both sides are adjacent to each other, a circle or a boundary line between the diffraction gratings is used. The incident light is uniformly scattered from the wavy line in each direction, so that the scattered light is not directed only in any specific diffracted light detection direction. Since relatively small relative to the intensity of the diffracted light from the grating, the probability of misreading occurs greatly reduced.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the optical recording medium of the present invention will be described below with reference to the drawings. In the following, description will be given assuming that information is recorded on a recording medium by a diffraction grating, but a hologram composed of substantially parallel interference fringes may be used instead of the diffraction grating.

FIG. 1 shows a plan view of the basic form of the optical recording medium of the present invention. The recording medium 1 has two areas 4 and 5 formed by minute circles 9 regularly spaced apart from each other. The diffraction gratings having mutually different grating directions are provided on the inner 5 and the outer 4 of the circle 9 (in the case of the figure, the diffraction grating oriented horizontally in the inside 5 and the diffraction grating oriented vertically in the outside 4). Is assigned. The recording medium 1 on which the two diffraction gratings are arranged as described above is set in, for example, a reading device as shown in FIG. Diffracted light is generated from the diffraction grating in the region 4 in the irradiation region in a direction perpendicular to the grating. In the case of the drawing, the diffracted light is detected by the photodetector D1, and it is interpreted that the code 1 (FIG. 6) is recorded. Is done. Further, diffracted light is also generated from the diffraction grating in the region 5 in the light irradiation region in a direction perpendicular to the grating, and is detected by the photodetector D3 in the case of FIG.
It is read that the code 3 is also recorded at the same time. Therefore, in the case of FIG. 1, it is read that the combination of the codes 1 and 3 is recorded. As described above, by combining the orientations of the diffraction gratings, any one of the ten pieces of information can be recorded on the recording medium 1 with the combination of the two diffraction gratings. By arranging a plurality of such recording media 1 in parallel,
Information can be recorded in decimal notation.

In the case shown in FIG. 1, since the recording area is divided by a circle 9, the incident light is uniformly scattered in each direction from the circle 9 which is the boundary between the diffraction gratings. Since the scattered light no longer enters only one of the specific photodetectors and the intensity of the scattered light is relatively smaller than the intensity of the diffracted light from the recorded diffraction grating, FIG. The probability of occurrence of erroneous reading is greatly reduced as compared with the conventional embodiment.

The area ratio between the two regions 4 and 5 is as follows:
In order to equalize the intensity of the diffracted light from each diffraction grating, in the case of a combination of two diffraction gratings, it is preferable to use 50: 5
It is desirable to arrange them so as to be 0, but when the diffraction gratings have different diffraction intensities, it is desirable to change the area ratio so as to compensate for them. Further, the circles 9 may be in a bale-stacked shape in which the arrangement lines are shifted by a half cycle as shown in FIG. 1, or may be arranged vertically and horizontally as shown in FIG. Further, the circles 9 may be arranged irregularly. Also,
Circles of different diameters may be mixed. In addition, as a modification of FIG. 1, it is conceivable to arrange two types of diffraction gratings only in the region 5 surrounded by the circle 9 and make the region outside the circle 9 reflective or absorptive. One example of this case is shown in FIG. As shown, two types of diffraction gratings having mutually different grating directions are arranged in adjacent circles 5. In the above description, it is desirable that the diameter of the circle 9 or the pitch of the arrangement thereof be about half or less of the beam diameter of the reading light. Further, a code 1 for recording the same diffraction grating in the two regions 4 and 5
In the case of (1), (2), (2), (3), (3), and (4) and (4), it is preferable that one of the regions (4) and (5) is blanked and the diffraction intensity is the same as the other cases.

In addition to the above-described embodiment in which the recording area is divided into two by the circle, the recording area may be subdivided by a straight line or a curve whose line direction changes randomly. FIG. 4 shows a plan view of one example. In this case, the recording area is subdivided by a plurality of parallel wavy lines 11, and the adjacent areas 4,
Two types of diffraction gratings having mutually different grating directions are arranged between the five diffraction gratings. In this case as well, since the incident light is scattered uniformly from each direction from the wavy line 11, which is the boundary line, the scattered light does not enter only one specific photodetector. Is relatively small with respect to the intensity of the diffracted light from the recorded diffraction grating, so that the probability of occurrence of erroneous reading is significantly reduced as compared with the conventional embodiment of FIG. Note that the region may be divided by intersecting the dashed lines 11.

The above is an example in which two different diffraction gratings are recorded in a recording area divided by a circle or a wavy line. However, this is extended to three or more, and two or more different diffraction gratings are placed in a circle. Recording may be performed, or three or more different diffraction gratings different from each other may be recorded in adjacent regions divided by a wavy line. Circle 9 in FIG.
An example is shown in which three different diffraction gratings are recorded in recording areas divided by. In this case, it is desirable that the area ratio between the inside and outside of the circle 9 be 2: 1.

Although the optical recording medium of the present invention has been described based on the embodiments, the present invention is not limited to these embodiments, and various modifications are possible. For example, the present invention can also be applied to a case where different information is recorded according to the difference in the interval instead of the direction of the diffraction grating. Also, the diffraction grating and the hologram can be applied to any known types such as an amplitude type, a phase type, a relief type, a volume type, a reflection type, a transmission type, a semi-transmission type and a partial reflection type.

[0020]

As described above, according to the optical recording medium of the present invention, the recording area is divided into the inside and outside of the circle by a large number of minute circles, and one or a plurality of diffraction gratings are provided inside the circle. Or arrange a hologram and arrange a different diffraction grating or hologram outside the circle, and make the inside and outside diffraction gratings or holograms adjacent to each other with the circle as a boundary, or Alternatively, the recording area is subdivided by a plurality of wavy lines, and adjacent diffraction gratings or holograms different from each other are arranged, and the diffraction grating or hologram on both sides of the wavy line is adjacent to each other. Therefore, the incident light is scattered evenly in each direction from the circle or the wavy line, which is the boundary line between the diffraction gratings, and the scattered light will not be directed only to any specific diffraction light detection direction. Since the intensity of the scattered light is relatively small with respect to the intensity of the diffracted light from the diffraction grating recorded, the probability of misreading occurs greatly reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of a basic form of an optical recording medium of the present invention.

FIG. 2 is a plan view of a modification of FIG. 1;

FIG. 3 is a plan view of another modification of FIG. 1;

FIG. 4 is a plan view of another embodiment of the present invention.

FIG. 5 is a plan view of still another embodiment.

FIG. 6 is a diagram for explaining the principle of recording information on a recording medium composed of a hologram composed of a diffraction grating or parallel interference fringes.

FIG. 7 is a perspective view illustrating a schematic configuration of a reading device.

FIG. 8 is a plan view of a conventional optical recording medium.

FIG. 9 is a diagram illustrating a state in which erroneous reading occurs by the optical recording medium of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical recording medium 2 ... Light source 3 ... Lens 4, 5 ... Divided division 9 ... Circle 11 ... Wavy line D1-D4 ... Photodetector

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G06K 19/06 G03H 1/02 G06K 7/12 G11B 7/00

Claims (2)

(57) [Claims] An optical recording medium for reading information recorded in the direction of diffracted light by irradiating a light beam, wherein a plurality of diffraction gratings or holograms having different directions or intervals of gratings or interference fringes is formed in a recording area. In an optical recording medium that is separately arranged in subdivided sections, the recording area is divided into a circle inside and outside by a number of minute circles, and one or a plurality of diffraction gratings or holograms are arranged inside the circle. , Ri Na arranged one diffraction grating or hologram different outside of yen, the
Diffraction gratings or holographs inside and outside a circle
Optical recording medium which beam is characterized that you have next to each other. 2. An optical recording medium for reading information recorded in the direction of diffracted light by irradiating a light beam, wherein a plurality of diffraction gratings or holograms having different directions or intervals of gratings or interference fringes are formed in a recording area. in the optical recording medium formed by arranging separately comminuted segment, the recording area by <br/> Ri is subdivided into a plurality of wavy line Ri name by placing the different diffraction gratings or hologram segment each other to adjacent the With the wavy line as the boundary,
Optical recording medium in which the diffraction grating or hologram, characterized that you have next to each other.