JPH01237940A - Optical recorder - Google Patents

Abstract

PURPOSE:To improve tracking accuracy by providing plural diffraction grating groups for diffracting a laser beam to have an optical recording medium irradiated and plural optical detectors corresponding to plural diffracted beams. CONSTITUTION:The laser beam emitted from a laser diode 1 is incident upon a phase type diffraction grating 5 via a collimator lens 2. The incident light is emitted to be diffracted beams by the grating groups 5a and 5b in their individual normal directions B and C at a prescribed angle of diffraction with these two directions respectively. Zero-th order and 1st order diffracted beams of the diffracted light of these two directions are formed in five beam spots (a)-(e) on an optical memory card 15 via a half-mirror 7 and a convergent lens 6. The spot (a) among them is formed from the zero order diffracted light, so as to perform the write and read of data. The spots (b)-(e) are formed by the 1st diffracted light. Reflected light from the card 15 is reversed and reflected by the half-mirror 7, and then incident upon the photo detector 10 via a convergent lens 8 and a cylindrical lens 9, and finally received independent ly by five light receiving parts, so as to carry out a tracking.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording device that performs data readout while reading data by irradiating a laser beam onto an optical storage medium such as an optical memory card.

[Prior Art] Generally, in an optical storage medium such as an optical memory card, information units lined up are scanned and read using a beam spot of several 4 meters emitted from an optical recording device. At this time, tracking servo is essential in order to scan along the middle information row.

For this reason, in conventional optical recording devices, the laser beam is converted into diffracted light through a diffraction grating 25 as shown in FIG. The so-called three-beam method is used, in which the main beam is used for performing this and the first-order diffracted light is used as the side beam. Then, as shown in FIG. 16, these two side beams are irradiated onto a line several pm wide lined up on both sides of an information unit column called a track guide 26 on the optical storage medium, so that the amount of reflected light from both side beams is equal. Tracking is performed by applying a servo.

Also, as an encoding method for recording information, -M
Self-clocking such as EFM and MFM is used for this purpose. This self-clocking encoding method has the advantage that clock information is included in the information unit string of the optical memory card, so no other clock information is required as long as the jitter of the reading mechanism is within the tolerance range. There is.

[Problem to be solved by the invention] The conventional optical recording device described above uses self-clocking as an encoding method, but as the storage capacity per medium area is increased, the jitter tolerance becomes smaller. There was a problem that accurate encoding could not be performed. Also, one of the two side beams is used for tracking.

It is also possible to use the other side beam to read clock information and perform NRZ encoding with separate clock information, but tracking using only one side beam will result in poor tracking precision If! The disadvantage was that i was low.

[L stage for solving the problems] An optical recording device of the present invention that solves the above-mentioned conventional problems is an optical recording device that loads and reads data by irradiating the optical storage medium-H with a laser beam. a diffraction grating that diffracts the laser beam and irradiates it onto the optical storage medium t; and a photodetector that receives the laser beam reflected by the storage medium to obtain information such as tracking and clocking; The diffraction grating is provided with a plurality of grating groups that generate a plurality of diffracted lights, and a plurality of photodetectors are provided corresponding to the plurality of diffracted lights.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 to 8 show an embodiment in which the present invention is applied to an optical recording device that loads and reads data from and to an optical memory card as an optical storage medium.

As shown in FIG. 1, the optical recording device according to this embodiment includes a laser diode (LD) 1 as a laser light source, a collimator lens 2, an electromagnetic wave plate 3, a diffraction grating 5, and a converging lens (objective lens). ) 6, a half mirror 7, a converging lens 8, a cylindrical lens 9, and a photodetector 10. Here, the collimator lens 2 is
It is provided to convert the laser light from the laser diode 1 into parallel light. Further, the y4 wavelength plate 3 converts the laser light from the laser diode 1 into circularly polarized light.

The laser light emitted from the laser diode 1 is converged by the collimator lens 2, diffracted by the diffraction grating 5, passes through the half mirror 7 and the electromagnetic wave plate 3, and is converged by the converging lens 6 to be sent to the optical memory card 151. The laser light that is focused on and reflected by the optical memory card 15 is reflected by the half mirror 7 and then passes through the converging lens 8 and the cylindrical lens 9 and enters the photodetector 10.

The diffraction grating 5 of this embodiment uses a so-called phase-type diffraction grating in which a concave-convex grating Y- is formed on a transparent plate. Unlike a diffraction grating, as shown in FIGS. 2 and 3, two grating groups 5a and 5 intersect at an angle close to 90° and extend in two directions.
It forms b. Of these two grating groups 5a and 5b, grating group 5a extends in the direction of arrow A indicating the scan direction at the same angle as the intersection angle of both grating groups 5a and 5b, and grating group 5b extends in the scanning direction. It extends in a direction parallel to a.

By using the diffraction grating 5 as described above, the laser light incident on the diffraction grating 5 is transmitted to the grating group 5a.

5b, the diffracted light with predetermined diffraction angles in two normal directions B and C travels through the converging lens 6. As a result, five beams are formed and five beam spots a are formed on the optical memory card 15F as shown in FIG. 4.6.

b, c, d, and e are connected.

Of these, beam spot a is located in grating group 5a.

5b by the zeroth order diffracted light. Beam spots b and c are connected by the first-order diffracted light by the grating group 5a, and beam spots d and e are connected by the first-order diffracted light by the grating group 5b. are connected by the diffracted light. Also, Beamsbok) b, a
, c coincide with the normal direction B of the grating group 5a, and the directions of the beam spots d, a, and e coincide with the normal direction C of the grating group 5b.

The optical memory card 15, which reads and reads data using an optical recording device, has an optical recording area 16 provided on a plastic substrate about the size of a business card. As shown in FIG. 6, track guides 17 and clock guides 18 are provided alternately.

The track guide 17 is formed into a belt shape with a certain radius (agm), and extends continuously in the longitudinal direction of the optical recording area 16 . This track guide 17 is for tracking using the above-mentioned beam spot, and is formed into a belt shape with a constant radius (several JLm). Further, the track guide 17 is formed to have a reflectance different from that of the optical recording area 16 by a method such as photolithography, printing, or vapor deposition.

The clock guide 18 serves as clock information for encoding, and has a rectangular mark as shown in the figure.
It is formed by consecutively forming old bits 20 in a straight line at minimum intervals l, in which binary coded information is interpreted as a light and dark pattern.

Further, this clock guide 18 is similar to the track guide 17.
It is formed by changing the reflectance using the same method as .

In addition, the track guide 1 of the optical recording area 16
The area between the clock guide 7 and the clock guide 18 becomes a track 16a for reading data information.

In the optical recording device of this embodiment, five beam spots (a) to (e) formed by a diffraction grating 5 and a convergent lens 6 are placed at a position t as shown in FIG. It forms an image.

That is, the beam spot a is arranged to correspond to the track 16a, the beam spots b and e to the track guide 17, and the beam spots d and c to the clock guide 18, respectively. Furthermore, beam spots b, e and beam spots d, c are located half way over the track guide 17 and clock guide 18, respectively, and beam spot a is located at the center of the track 16a. Then, each beam slot (a) to (e) is scanned in the direction of arrow A to write and read data on the memory card 15.

The photodetector 10 receives the images of the five beams a to e reflected from the optical memory card 15, and receives images from five light receiving sections 10a to 10e made of elements such as PIN photodetectors. It is configured.

Further, the light receiving sections 10a to 10e are arranged corresponding to the five beam spots a to e as shown in FIG. 8, and receive the reflected light from each beam spot a to e independently. It is configured so that it can be used. In addition, the light receiving section 10
For a, use an optical sensor divided into four parts as shown in the figure (
For example, a quarter-IA photodiode) has been used.

Next, an explanation will be given of the operation in data writing and reading of this embodiment configured as shown below.

To write and read data from the optical memory card 15-, position the five beam spots a-e formed by the diffracted light by the diffraction grating 5 with respect to the optical recording area 16 as shown in FIG. This is done by scanning in the A direction.

Data reading is performed by encoding the light reception signal from the beam spot a received by the photodetector $10. That is, the light reception signal changes corresponding to the write bit 20, and this change is encoded as 2 (/j) and read out as data.The write bit 20 is written to the track 16a by increasing the power of the laser beam. This is done by locally melting the surface of the track 16a using a beam blast a to change the reflectance.

The trackers and kings for scanning are the beam spots (b, e) located on the left and right track kites 17 in the case of FIG.
Detects the reflected light from the light receiving unit fob of rA10, 10e
For example, in Fig. 6, the beam spot a
-e shifts to the left in the figure, beam spot b deviates from the right track guide 17, and beam spot e covers more of the left track guide 17, resulting in a difference in the amount of received light (b -e) is detected. Tracking is performed by servo control according to this detection signal.

Furthermore, when the beam spot a moves to the adjacent track 16a as shown in FIG. 7, the two beam spots d,
c is located corresponding to the track guide 17. For this reason, tracking is performed by receiving the reflected light from the beams (c and d) at the light receiving section 10c.

This is done by detecting at 10d and calculating the difference (d−c) in the amount of received light.

In addition, in the case of Fig. 6, beam spot C or d (7th
In the case of the figure, the data writing number is determined by counting the clock information from the clock guide 18 obtained by detecting the reflected light of the beam spot b or e) with the light receiving section 10c or 10d (light receiving section 10b or 10e). Encode for reading.

Note that for focusing, an astigmatism method is used in which the focal shape of the cylindrical lens 9 is detected by the light receiving section 10a of the photodetector IO.

In this embodiment, as described above, the diffraction grating 5 is provided with two grating groups 5a and 5b that intersect with each other, thereby forming five beam spots a-e, and beam spots b-e.
By using this for tracking and counting clock information, the disadvantage associated with the reduction in the jitter tolerance range of the read signal, which has been a problem with the conventional encoding method using self-clocking, is eliminated and reliability is improved.

Next, a second embodiment of the present invention is shown in FIGS. 9 and 10. In this embodiment, one diffraction grating 5 has two
Two grating groups 5a and 5b are provided. The grating group 5a is perpendicular to the scanning direction (arrow A direction), and the grating group 5b intersects with the grating group 5a at a certain angle. Using such a diffraction grating 5, five beam spots a to e are formed in the optical recording area 16 in which only the track guides 17 are provided at regular intervals in the arrangement shown in the figure.

Here, beam spot l-a is used for writing and reading data, and beam spot b or c is used to check the written bit 20 immediately after writing bit 20 by beam spot a. Also,
beam spot d.

e is used for tracking. With such a configuration, since the write bit 20 can be confirmed while being written, there is no need to read only for confirmation.

Also, No. 11. The third embodiment of the present invention shown in Figure i2 is
Three grating groups 5a, 5 are formed on the diffraction grating 5 in the direction shown in the figure.
b and 5c are provided, thereby forming seven beam spots a to g as shown in FIG. 12.

Of these, beam spot a is used to write and read 1B of data, beam spots b and c are used to confirm writing, and two of beam spots d to g are placed on the two track guides 17 for tracking. The other two clock guides are arranged on two clock guides 18 and used for reading clock information. This allows tracking and clock information to be counted, and also eliminates the need for confirmation-only reading.

Furthermore, a fourth embodiment of the present invention is shown in FIGS. 13 and 14. In this embodiment, the diffraction grating 5 is formed by arranging a plurality of four concentric grating groups 5d. Each of the grating groups 5d functions as a so-called Fresnel zone plate, and converges the laser light from the laser diode 1 as shown in the figure to form four beam spots aNd. In this embodiment, these four beam spots a- d is the track 1 between the track guides 17 as shown in FIG.
If the grating group 5d is in the shape of a Fresnel zone plate as in this embodiment, the converging lens 6 shown in the first embodiment is not required. be able to.

Note that the configuration of the diffraction grating is not limited to that shown in each embodiment described in L. For example, by varying the orientation and number of grating groups, a beam spot different from that of the above embodiments can be created. pattern can be obtained.

In addition, it goes without saying that the diffraction grating may be of an amplitude type or a reflection type in addition to the phase type shown in the example.Furthermore, although an optical memory card has been described as an optical storage medium, the same applies to an optical disk. It is also possible to apply

[Effect of the invention] Below-L explanation 1. As described above, the optical recording device of the present invention includes a diffraction grating that diffracts Rede light and irradiates it onto an optical storage medium;
a photodetector for receiving the laser beam reflected by the storage medium to obtain tracking and clocking information; By providing a photodetector corresponding to the plurality of diffracted lights, a plurality of beams can be used for reading write numbers, tracking, reading clock information, and checking written data according to the configuration of the optical recording area of the optical storage medium. Spots can be generated and placed, improving the reliability of data recording.

[Brief explanation of the drawing]

Fig. f51 is a schematic configuration diagram of an embodiment of the present invention, Fig. 2 is a plan view of a diffraction grating used in one embodiment, Fig. 3 is a partial cross-sectional view of the diffraction grating, and Fig. 4 is a beam spot due to the diffraction grating. 5 is a perspective view of the optical memory card, FIGS. 6 and 7 are views showing the arrangement of the beam spot with respect to the optical recording area, and FIG. 8 is a plan view of the photodetector.
FIG. 9 is a plan view of a diffraction grating used in a second embodiment of the present invention. Fig. 10 is a diagram showing the arrangement of beam spots by the diffraction grating, Fig. 11 is a plan view of the diffraction grating used in the third embodiment of the present invention, and Fig. 12 is the arrangement of the beam spots by the diffraction grating. FIG. 13 is a diagram showing the fourth embodiment of the present invention.
FIG. 14 is a perspective view showing the diffraction grating of the embodiment, FIG. 14 is a diagram showing the arrangement of beam spots by the diffraction grating, FIG. 15 is a plan view of a conventional diffraction grating, and FIG. 16 is a diagram showing the beam spot arrangement by the diffraction grating. It is a figure showing an arrangement state. l: Laser diode 5: Diffraction grating 6: Convergence 1/lens 5a to 5d: Grating group lO: Photodetector 10a to 10e: Light receiving section 15: Optical memory card 17: Track guide 18: Clock guide aNg: Beam Spot Applicant Stock Company Shiniskei Figure 1 0 0100100 ＼＼＼＼＼ E Thief ・ ・ O ・ ・

Claims (1)

[Claims] Writes data by irradiating laser light onto optical storage media.
An optical recording device that performs reading includes a diffraction grating that diffracts the laser beam and irradiates it onto the optical storage medium, and a photodetector that receives the laser beam reflected by the storage medium to obtain information such as tracking and clocking. What is claimed is: 1. An optical recording device comprising: a plurality of grating groups for generating a plurality of diffracted lights on the diffraction grating; and a plurality of photodetectors corresponding to the plurality of diffracted lights.