JPS61131252A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To facilitate discrimination of a track and to improve the discrimina tion accuracy by constituting a unit information area recorded on a track of a grid, and differentiating the shape or condition of the grid from the adjacent grid. CONSTITUTION:Recording pits 11, 12, 13, etc. on tracks 21, 22, etc. recorded with information are constituted respectively of a grid 12. In this case, the angle between the arrangements of the grids in the recording pits 11 and 12 is regulated to 90 deg.. The arrangement is alternately changed in the tracks 21, 22, 23, etc. Namely, the condition of the grid of the recording pit is different from the adjacent track. The direction of the light diffracted by the grid is determined by the direction of the arrangement of the iron. Accordingly, the track can be discriminated by detecting the distribution of the light reflected from the recording pit. By such a structure, the track can be discriminated with high accuracy, and high-density recording is made possible.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to an optical information recording medium applicable to optical discs, optical cards, optical tapes, etc. [Prior Art] Conventionally, information has been recorded using light, Various forms of read media are known, such as optical disks, optical cards, and optical tapes. The principles of recording or reading information in these media vary depending on the type of media material used, the optical system used for recording or reading, and the type of system, and several methods have been put into practical use. A typical example is a method of detecting a signal by using light, such as in a magneto-optical recording medium, to change the red = rotation angle change that occurs in the medium into light intensity;
Alternatively, there is a method of recording and reproducing by changing the light transmittance 9 reflectance and absorption spectrum of the medium only in the portion corresponding to information, or by changing the refractive index and shape of the information recording part of the medium and irradiating the recording part. There is a method of detecting a change in light intensity corresponding to a signal using phenomena such as diffraction and interference of reproduced light.

For example, with a relatively simple configuration, it is possible to obtain good S/S/
As a method for obtaining the N ratio, there is known a method in which unit recording areas are recorded in the form of pits. In addition, if the application form for such pit recording is further expanded, the cost of the medium/device can be reduced by omitting the autofocus (A, F) and autotracking (AT) mechanisms. The applicant has already proposed an optical information recording medium in which a unit information area on which information is to be recorded is configured in a lattice.

By the way, many optical information recording media are formed with a plurality of tracks on which information is recorded lined up. FIG. 9 is a plan view showing the recording surface of a conventional optical card in which information is recorded in this manner. Here, each track 521, 522, 52
1,524. . . . are formed as a one-dimensional array of pits 51 in a continuous direction, and such tracks are arranged adjacently to form a secondary/marshal recording surface. In addition, when reading information, for example, while transporting an optical card in a direction perpendicular to the track, a finely narrowed beam spot is scanned along the scanning line S, and this reflected light is sent to a light receiving element such as a photodiode. Detection methods were used.

Furthermore, since the tracks of such an optical information recording medium are arranged at a very high density, there is a possibility that pits of a track different from a desired track may be read out. For this reason, in the past, in order to identify adjacent tracks, a start pit 55 and a stop pit 56 were provided at the beginning and end of each track, respectively, as shown in FIG.

The start pit and stop pit on the same track have opposite polarities, and the polarity between start pits and stop pits is also reversed for each track. Therefore, the previous track and the current track were distinguished from each other by reversing the polarity of both the start pit and stop pit. Such track identification is extremely important, especially when error correction is performed using an error correction code, since reproducing information for each track is a prerequisite for correction.

However, as mentioned above, optical information recording media provided with a start pit and a stop pit may be used if the beam spot scans across adjacent tracks, or if the start pit becomes a stop pit due to dust, scratches, etc. There is a drawback that if the track cannot be read, correct track identification cannot be performed.

(Summary of the Invention) An object of the present invention is to eliminate the drawbacks of the prior art and provide an optical information recording medium that can easily and accurately identify tracks.

The above object of the present invention is achieved by configuring the unit information area recorded on a track as a grid, and making the shape or shape of the grid different between adjacent tracks.

(Example) First, the basic structure of the lattice in the optical information recording medium of the present invention will be explained with reference to FIG. In FIG. 1(A), 11 is an optical information recording medium, 12 is a unit information area (hereinafter referred to as a recording pit) which is the smallest unit for recording information, 13 is a transparent protective layer, 14 is a light reflective film, and 15 is a transparent protective layer. Hail the board. Here, the recording pits 12 are not simply uneven steps as in the conventional example, but have a periodic lattice structure within the pits 12. Such a lattice structure can be formed not only by embossing but also by various means described below. Information reproduction light 1
It is assumed that 7 is light from a wide light source such as an LED, and the reproduced light illuminates the pit 12 and its surrounding area almost uniformly through the lens 16. Due to the diffraction effect of the grating within the pit, the light that illuminates the pit is intensified and reflected in a specific direction determined by the pitch of the grating and the wavelength of the illumination light. Therefore, for example, if the pitch of the grating is set to at least 1 for the first-order diffracted light,
If the pits 8 are selected so that they do not enter the lens 16, all the diffracted light will be diverted to the outside of the lens, and there will be a clear difference in the amount of light compared to when the specularly reflected light from the part where the pits 12 are not present returns through the lens 16. Therefore, a reproduced signal with a good S/N ratio can be obtained. FIG. 1(FB) is a diagram showing the optical output corresponding to the recording pits shown in FIG. 1(A). As is clear from FIG. 1(B), the amount of light that returns to the lens 16 from the portion where the pit 12 exists is extremely small compared to the amount of light that returns to the lens 16 from the portion where no pit exists. The difference in light amount in the boundary area where the image is not displayed is also noticeable. Therefore, as mentioned above, if there is no grating inside the pit, the amount of light reflected from inside the pit will increase and the S/N ratio will decrease, or in the case of a modulation method that records signals depending on the length of the recording pit. However, in the optical information recording medium of the present invention, the light intensity of the reproduction light varies depending on the length of the pit, or the light intensity changes only at the edges of the pit, making signal reproduction difficult. If the pitch of the pits is constant, the angle of diffraction of light is always constant regardless of the length and size of the pits, making stable signal reproduction possible.

Next, a case in which the present invention is applied to an optical card will be explained in more detail using an example.

FIG. 2 is a plan view schematically showing the state of information in the optical information recording medium of the present invention. In the figure, 2+, 2t, 2
j+ 24... are tracks on which information is recorded, and these recording pits 11, 12, 13...
・Each is composed of a lattice as shown in Figure 1. Here, the recording pits 11 and 12 have lattice arrangement directions that are at an angle of 90°. The arrangement direction of such a grid is the tracks 27, 22, 29, 24.
It is formed so that it can be switched alternately. That is, in this embodiment, the lattice states (arrangement direction) of recording pits are different between adjacent tracks. The direction of the diffracted light by the grating is determined by the direction in which the grating is arranged.

Therefore, in the optical information recording medium of this embodiment, tracks can be identified by detecting the distribution of light reflected from the recording pits.

FIG. 3 is a side view showing an embodiment of an optical card reader device using the optical information recording medium of the present invention. In the figure, 10 is an optical card which is an optical information recording medium of the present invention, and information is recorded on the surface over a plurality of tracks as shown in FIG. Light emitted from a light source 12 composed of a semiconductor laser, an LED, etc. is focused by an illumination lens 13, and is focused on an optical card 10.
Illuminate the upper recording pit 1. The reflected light from the optical card 10 is collimated by the collimator lens 14, and is collimated by the aperture 15 arranged on the Fourier plane of the collimator lens 14.
guided by.

A light sensor 16 is provided on the aperture 15,
Diffracted light from recording pit 1 is detected.

Further, the specularly reflected light from the portion where the grating is not formed and the O-th order diffracted light due to the grating pass through the opening 17 of the aperture 15, are condensed by the condenser lens 18, and detected by the optical sensor 19. Further, the optical card is conveyed in the direction indicated by the arrow by a card conveyance means (not shown), and information is read out along the scanning line S' in FIG.

FIG. 4 is a plan view of the light receiving portion of the aperture 15 in the apparatus shown in FIG. 16. and 162 and 163 and 16
A pair of optical sensors 4 detect diffracted light generated in mutually orthogonal directions from two types of gratings arranged in different directions as described above.

FIG. 5 shows the intensity distribution of the reflected light in the AA' cross section due to the recording pits having gratings parallel to the paper surface when the aperture 15 is arranged so that its center line 21° is perpendicular to the paper surface in FIG. It is. 61.62.62', 6
3.63' are 0th order light (non-diffracted light) +1st order light, -1st order light, and +2nd order light, respectively.

-It is secondary light. Optical sensor 16. +1'62 detects only the diffracted light (±1st order light, ±2nd order light, . . . ) by the grating in the direction parallel to the plane of the paper in FIG.

On the other hand, in Fig. 3, the intensity distribution of the diffracted light due to the pits having the grating perpendicular to the plane of the paper is the center line 212 (C-C'
) direction shows characteristics similar to those shown in FIG.

That is, in the same figure, the sensors 16s + 16t are each 1
Equivalent to replacing 63.164. sensor 16s
+164 is the diffracted light (±
Only primary light, ±secondary light, etc.) are detected.

In addition, the diameter d of the aperture opening 17 is selected to allow only the zero-order light to pass through, and the passing light is detected by the sensor 19, but the light generated by the grating in either direction has approximately the same intensity distribution, and the light transmitted by the grating in any direction has approximately the same intensity distribution. It is sufficiently high compared to the amount of specularly reflected light from the pits. Therefore, depending on the presence or absence of the grating, information
or 1) by the sensor 19, and the orientation of the grating is detected by the optical sensor pair 16. and 16. and 1G, and 164. Here, since the orientation of the grid is alternately formed for each track, the sensor pair 161
Tracks can be identified by the outputs of , 162 , 163 , and 164 . Furthermore, since it does not detect specific pits like conventional methods, it has an extremely strong ability to discriminate against dust, scratches, etc. Furthermore, since there is no need for a start pit, stop pit, etc. as in the conventional example, it is advantageous from the point of view of redundancy.

FIG. 6 is a plan view schematically showing the state of information in an optical information recording medium according to another embodiment of the present invention. In the figure, 32
．． ．． 32□, 323, 324... are tracks on which information is recorded, and these recording pits 311, 312...
... are each composed of a grid as shown in Figure 1.

Here, the recording pits 311 and 312 have different grating pitches. And the pitch of such a grid is track 32+, 322.32g, 324...
It is formed so that it changes alternately. That is, in this embodiment, the pitch of the grid of recording pits is different between adjacent tracks, and the tracks can be identified in the same way as in the example of FIG. 2 when reading out information along the scanning line S''.

The reading optical system in this embodiment may be basically the same as that shown in FIG. 3, but the arrangement of the sensor for detecting the diffracted light may be configured as shown in FIG. 7, for example. In FIG. 7, an aperture opening 37 having a diameter d is provided above the aperture 35 as in FIG. Also center line 33
a pair of optical sensors 36. ．． 36. are juxtaposed.

FIG. 8 shows the aperture 35 along its center line 33 (A-A').
is the intensity distribution of diffracted light due to pits having gratings parallel to the plane of the paper as shown in FIG. 6 when the pits are arranged perpendicular to the plane of the paper in FIG. 41 is the intensity distribution of the diffracted light on AA' due to pits with large pitch gratings, and 42 is the intensity distribution of diffracted light on AA' due to pits with small pitch gratings.
This is the intensity distribution of the diffracted light on A'. The latter has the same envelope (and therefore the same peak value) as the former, but the spectrum width is narrower and the pitch of higher-order components is larger. Therefore, the output of the sensor pair 161, 162 that detects the diffracted light changes depending on the pitch of the grating. In addition,
The diameter d of the aperture opening 37 is selected to allow only the O-th order diffracted light from the grating with the smaller pitch to pass through. Further, the presence or absence of a grating can be easily detected by an optical sensor placed after the aperture opening 37, as in the example shown in FIG.

Furthermore, since the pitch of the grating is alternately formed for each track, the sensor pairs 36. Tracks can be identified by the outputs of and 36, and the same effect as in the example of FIG. 1 can be obtained.

The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the direction in which the grid is arranged.

Instead of the pitch, the shape of the grating, such as the groove shape of the grating (for example, rectangular or triangular) or the depth of the groove, may be varied for each track, or a combination of these may be used. Further, although the embodiment shows a case where the shape or state of the grating changes alternately for each track, three or more types of gratings may be formed for each track. Furthermore, the method of reading such an optical information recording medium is not limited to the method using beam spot scanning as described above. For example, one track is illuminated by slit exposure of a light source with a rectangular light emitting part (such as a surface emitting laser) or a light source with a light source spread (such as an LED), and the modulated light is detected by a line sensor such as a COD. , information may be read out once for each track.

Further, in the above example, a relief structure in which grooves are formed on the medium as a grating was explained, but the grating in the present invention can also be formed by changing the refractive index 9 of the medium. can. The grating can be manufactured using various techniques that are well known in the art, such as embossing, photolithography using mask exposure, and interference fringe exposure. In particular, the emboss molding technique is suitable for producing optical cards, optical disks, etc., since it is possible to make large quantities of copies from a master disk on which information is recorded.

Further, although the above example has been explained using a light-reflecting medium, it goes without saying that the present invention has exactly the same effect on a medium in which the pit portions transmit light.

(Effects of the Invention) As explained above, the present invention comprises a conventional optical information recording medium in which the unit information area recorded on a track is composed of a lattice, and the shape or state of this lattice is different between adjacent tracks. 1) Enables high-precision track identification that is less affected by dirt, scratches, etc. 2) Reduces information redundancy and enables high-density recording 3) Expands application forms and reduces manufacturing costs This has the effect of reducing

[Brief explanation of the drawing]

FIGS. 1A and 1B are diagrams each explaining the basic structure of a lattice in an optical information recording medium of the present invention, and FIG. 2 schematically shows how information is recorded in an embodiment of the present invention. figure,
FIG. 3 is a schematic diagram showing the configuration of an embodiment of an optical card reader device for reproducing information on an optical information recording medium of the present invention;
．． Fig. 4 is a plan view of the aperture in the apparatus shown in Fig. 3, Fig. 5 is a diagram showing the light distribution on the aperture of Fig. 4, and Fig. 6 shows a recording ball in another embodiment of the present invention. 7 is a plan view showing a modified example of the aperture for reading the optical information recording medium shown in FIG. 6, FIG. 8 is a diagram showing the light distribution on the aperture shown in FIG. 7, and FIG. FIG. 3 is a diagram showing how information is recorded on an optical information recording medium. II, 12, 1.5912, 3], 1,312... Recording pit, 2+, 22, 2s, 24.321, 3
22, 323, 324... Track, 11... Optical information recording medium, 13... Protective layer, 14...
...Light reflection 1 model, 15...Iita, 16...Lens,
17... Information reproducing light, 18... 1st-order diffracted light. appearance

Claims (1)

[Claims] (1) In an optical information recording medium in which a plurality of tracks on which information is recorded are formed side by side, the unit information area recorded on the track is composed of a lattice, and the shape or state of the lattice is different in adjacent tracks. An optical information recording medium characterized by: