KR0144193B1 - Optical recording medium and reproducing apparatus using grating lens - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and a recording / reproducing apparatus, and more particularly, to an optical recording medium using a diffraction grating and a reproduction apparatus thereof, wherein a diffraction grating is formed on a disc to extract information from the distribution of diffracted light diffracted by the diffraction grating. will be.

Such an optical recording medium using the diffraction grating of the present invention alternately forms the permeable membrane and the barrier membrane in the form of the diffraction grating on the track at right angles to the direction of travel of the track, and the barrier membrane and the permeable membrane having the same number as the unit block are formed as a unit block. The data is recorded by varying the length of the permeable membrane and the blocking membrane of each unit block so as to correspond to the respective data, and the reproducing apparatus of the optical recording medium using the diffraction grating of the present invention is different for each block unit using the diffraction grating. An optical recording medium recorded so that light diffracted at an angle is output, light irradiation means for irradiating light on a track of the optical recording medium in units of blocks, and diffraction at different angles as light from the light irradiation means is irradiated Light detection means for detecting the diffracted light, block determination means for determining the type of the block by receiving the output of the light detection means, and A block table for outputting a digital signal corresponding to an output value of the block determining means, and a block signal for synchronizing a bit clock and a peak value by receiving a digital signal output from the block determining means and the look table; It includes a bit clock and a synchronization detection means for outputting.

Description

Optical recording medium and diffraction grating using the diffraction grating

FIG. 1A is a diagram showing an EFM signal of a general disk.

FIG. 1B shows an NRZI signal which is a recording signal of a general disc.

FIG. 1C is a partial cross-sectional view of a general disk. FIG.

Fig. 1 (d) shows an analog signal of harmonics (RF) reproduced from a general disc.

2 is a view showing a state in which a beam is irradiated to the pit and the mirror surface of the disk.

3 is a schematic signal processing block diagram of a general optical disk.

4 is a diagram illustrating an example of a frequency and a structure of a diffraction grating according to the present invention.

5 is a view showing a part of a transmissive optical disk according to the first embodiment of the present invention.

6 is a reference diagram for explaining a technical theory of the transmissive optical disk of the present invention.

Fig. 7 is a diagram showing a part of the reflective optical disc of the second embodiment of the present invention.

8 is a signal diagram of FIG.

Fig. 9 is a block diagram showing the construction of an optical recording medium reproducing apparatus using the diffraction grating of the first embodiment of the present invention.

FIG. 10 shows an example of an output waveform of the light detecting means of FIG.

* Explanation of symbols for main parts of the drawings

A: Blocking membrane B: Permeable membrane

81: light detection unit 82: block determination unit

83: lookup table 84: bit clock and synchronization detection unit

85: Digital Signal Processor (DSP)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and a recording / reproducing apparatus, and more particularly, to an optical recording medium using a diffraction grating and a reproduction apparatus thereof, wherein a diffraction grating is formed on a disc to extract information from the distribution of diffracted light diffracted by the diffraction grating. will be.

Generally, an inter-mark recording or a mark length recording is known as an optical recording method. An example thereof will be described below.

(A) of FIG. 1 shows an example of an EFM signal, and (b) is a non-return-to-zero-inverted (NRZI) format for writing to a disc.

The NRZI signal is recorded on the disc in the form of a Pit, and the form thereof is as shown in (c).

The signal recorded in the form of the pit is read by the laser beam of the pick and the pattern of the signal is the eye pattern of the waveform (d) which is an analog signal of harmonics RF.

The shape of the waveform (eye pattenr) is that the intensity of the laser beam reflected from the disk varies depending on the presence and length of the pit to reproduce the pit signal of the disk.

FIG. 2 (a) shows a state in which the laser beam is reflected and reflected on the mirror surface of the track. FIG. 2 (b) shows the state in which the laser beam is reflected and diffracted by the pit of the track. In the part with, since the light is diffracted by the pit, the amount of reflected light is reduced by the pit.

3 is a schematic signal processing block diagram of a general disk, in which a laser beam is changed from collimated lenses 1 to parallel light and irradiated to the disk 4 through the beam splitter 2 and the objective lens 3. The first diffracted light of the beam diffracted and reflected at the pit surface passes through the connection lens 5 and is incident on the photodiode 6.

The reflected beam incident on the photodiode 6 is used as a control signal of a focus servo and a tracking servo, and at the same time, is converted into an electrical signal (EFM) to be amplified by the preamplifier 7 and the waveform of the data slice circuit 8. It is shaped and input to the data strobe circuit 9 to strobe the width between the edges of the EFM signal (the width of 3T to 11T) with the clock extracted from the sliced signal and output as a digital signal.

The output of the data strobe circuit 9 is input to a digital signal processing circuit.

Conventionally, as described above, an EFM signal is mark-recorded to convert the intensity of light diffracted and reflected from the mark into an electrical signal in a photodiode, thereby reproducing the signal. Accurate reproduction of the signal is performed by each foot of the EFM signal (3T). 11T) should be accurately found from the analog signal of harmonic (RF) which is a reproduction signal.

However, high-density discs have a disadvantage in that they are difficult to reproduce because the RF signal is degraded due to the frequency characteristics of the optical pickup when the length of the minimum pit T, which is a form of mark-length recorded signal, is shortened.

Accordingly, the present invention converts a data stream into a diffraction grating recording form, but combines the signal bits (3 bits) into unit blocks, records them with a diffraction grating having a predetermined period, and when the laser light is reproduced, As the light is irradiated onto the block, the light is diffracted to detect the designated diffracted light for each block having a predetermined diffraction angle, and then converts the light into a digital signal, which is the original signal, and then outputs the optical recording medium using a diffraction grating. And a recording / reproducing apparatus thereof.

The optical recording medium using the diffraction grating of the present invention for achieving the above object is the optical recording medium using the diffraction grating of the present invention alternately transmissive film and the blocking film in the form of the diffraction grating perpendicular to the traveling direction of the track on the track. And the data is recorded by varying the length of the permeable membrane and the barrier membrane of each unit block to correspond to each data, and recording the data using the diffraction grating of the present invention. The apparatus for reproducing a medium includes: an optical recording medium on which a diffraction grating is output so that light diffracted at different angles in units of blocks, light irradiation means for irradiating light on a track of the optical recording medium in units of blocks; Light detecting means for detecting diffracted light diffracted at different angles as the light of the light irradiating means is irradiated; Block judging means for judging the type of the block by receiving an output, a lookup table for outputting a digital signal corresponding to an output value of the block judging means, and a digital signal output from the block judging means and the lookup table. It is characterized in that it comprises a bit clock and a synchronous detection means for outputting a synchronization signal for bit clock and peak value detection to the block determination means and the look table.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

4 is an explanatory view of a configuration example of a diffraction grating frequency and a diffraction grating according to the present invention, and FIG. 5 is a view showing a part of a transmissive optical disc of the first embodiment of the present invention.

According to the present invention, data bits are bundled in fixed block units and recorded on a disk as a diffraction grating having a period d.

That is, the frequency of the diffraction grating is different according to each data as shown in FIG. 4 (a), and the period of the lowest frequency f ₀ as shown in FIG. 4 (b) is d ₀ . this d _0/2, transparent layer (B) is, and such that d _0/2 frequency with such a configuration, _{f 0 f 1 f 2 f 3} f 4 f 5 f 6 f 7 thereto cycle according to if the d ₀ d ₁ d ₂ d ₃ d ₄ d ₅ d ₆ d _{7 The} diffraction grating is configured to be equal.

Therefore, by adjusting the period d to have the frequency of the diffraction grating corresponding to the data along the track of the disc, FIG. 5 shows a part of one track of the transmissive disc to be described in the present invention. ) And a plurality of (2 or more) permeable membranes (B) as a unit block, and divided into eight types according to the specifications of the width of the barrier membrane (A) and the permeable membrane (B). In other words, the lengths of the slit in (permeable membrane) and the barrier membrane formed in one block are the same, but the length of the permeable membrane and the barrier membrane is relatively short depending on the type of the block. The number of the permeable membranes B may be different. The number of bits of the data stream forming the unit block is set to 3 bits in the present invention, but may vary depending on the method of signal processing.

The technical theory described above with reference to FIGS. 5 and 6 is as follows.

When the number of the blocking films A and the transmissive membrane B of the same standard is arranged in one direction and irradiated with light having a predetermined period λ in the perpendicular direction thereof, the diffracted light may have the same specifications as the The diffraction grating 10 is distributed in a form having n peak values at a distance of Z _i .

If Z = Z _i , the light distribution is represented by luminous intensity I (θ),

[I (θ)] is I (θ) = E (θ) ² = I _o [SIN (πN / 2) / SIN (Φ / 2)] ² ,

Where Φ = kDSINθ equation ①

(Where k; propagation constant, k = 2π / λ, Φ; phase)

In the above formula (1), the luminous intensity (I _MAX ) of the maximum peak value occurs at Φ = 2πn. (N = ± 1, ± 2, ± 3,…;

Therefore kDSINθ = 2nπ, DSINθ = 2nπ / k = nλ equation ②

As can be seen from Equation (2) above, when λ (incident light cycle) is constant, the diffraction light of the order specified by the slit spacing D regardless of the number N of the transmission film B and the blocking film A is determined. It can be seen that the diffraction angle θ with respect to the maximum peak value I _MAX changes.

Further, the diffraction angle θ of the maximum peak value of the first-order diffracted light (when n is 1) becomes θ = SIN ⁻¹ (λ / D) in equation (2).

The diffraction angle θ of the maximum peak value of the secondary diffracted light (when n is 2) becomes θ = SIN ⁻¹ (2λ / D) in equation (2).

On the other hand, θ at which the minimum value of the n-th order diffracted light occurs is θ = SIN ⁻¹ [n + (λ / 2)].

Therefore, it can be seen that the diffraction angle β varies depending on the period D of the transmission diffraction grating (length of the slit + length of the blocking film).

As described above, the permeable membrane (B) and the barrier membrane (A) formed in one block have the same length, but are divided into eight types of blocks, and the permeable membrane and the barrier membrane of the same length formed in each kind of block have eight different kinds. Filled with length and number.

FIG. 7 shows a part of the reflective optical disk of the second embodiment of the present invention, in which a sawtooth reflective film is formed such that one side has an inclined 11 of a predetermined length d on a track, where nλ = d (sinα ± sinβ). If α = 0, nλ = dsinβ, and n = 1 (first-order diffraction light), β = sin ⁻¹ (λ / d).

Therefore, even in the reflective optical disk using the diffraction grating, if the length d of the inclined plane is adjusted to have the diffraction grating frequency as described in FIG. 4, the diffraction angle β varies according to the period d of the diffraction grating. Able to know.

Therefore, the reflective disk and the transmissive disk can use the same signal processing device.

FIG. 8 is a signal diagram of FIG. 5, FIG. 9 is a block diagram of a recording / reproducing apparatus of an optical recording medium using a diffraction grating of the first embodiment of the present invention, and FIG. 10 is an output waveform of the light detecting means of FIG. Figure 1 shows an example.

As shown in Fig. 8, each block of a track of a disc having a data stream of 3 bits as a unit block is filled with alternating permeable membranes and blocking membranes in the direction perpendicular to the track traveling direction.

Therefore, in the optical recording medium reproducing apparatus using the diffraction grating of the first embodiment of the present invention, the optical recording medium 4 which records data using the diffraction grating as shown in FIG. A first objective lens 1 for irradiating unit blocks, a second objective lens 3 for focusing and diffracted light irradiated onto the optical recording medium by the first objective lens 1, and a beam splitter ( 2) Diffraction angles θ different from the diffraction light focused by the connection lens 5 and the second objective lens 3, the beam splitter 2, and the connection lens 5 depending on the type of unit block. A light detector 81 composed of eight light receiving elements at a position capable of receiving first diffracted light having a? And a block determination unit 82 for determining the type of a block by receiving the output of the light detector 81; ) And a digital signal for outputting a digital signal corresponding to the output value of the block determination unit 82. The block determination unit 82 and the lookup table 83 receive a digital signal output from the table 83 and the block determination unit 82 and the lookup table 83 to obtain a synchronization signal for detecting a bit clock and a peak value. And a digital signal processor 84 for processing and outputting the digital signal output from the lookup table 83.

The operation of the reproducing apparatus of the optical recording medium using the diffraction grating of the first embodiment of the present invention is as follows.

The laser beam LD passes through the objective lens 1 and is irradiated to the optical disk using the diffraction grating. At this time, the laser beam is irradiated to the unit block consisting of a plurality of transmission membrane and the blocking membrane. Therefore, the diffracted light is connected to the light detector 81 through the connection lens 5 via the objective lens 3 and the beam splitter 2.

In this case, since the light detector 81 arranges eight light-receiving elements at positions capable of receiving first-order diffracted light having different diffraction angles θ according to the type of unit block among the diffracted light, Type of unit block read by first diffracted light of an arbitrary block input to an arbitrary light receiving element of the light detector 81 is converted into an electrical signal and input to the block determining unit 82 as shown in FIG. Will be determined.

The signal output from the block determination unit 82 is input to the lookup table 83 to reproduce the original digital signal (3bit) for the block, and the bit clock and synchronization detection unit 84 performs the block determination unit 82. ) and rukeop the table 83 receives a digital signal input from the detection timing (f _s) for the peak detection bit clock (3f _s) rukeop table 83 and block judgment because synchronizing unit 82 rukeop table At 83, the digital signals are sequentially output to the digital signal processing unit 85.

In Fig. 9, the optical recording medium using the diffraction grating is a reproducing apparatus in the case of Fig. 5, and in the case of the reflective type of Fig. 7, the reflected light may be connected.

In this case, as described above, the beam irradiated onto the disk may be preferably irradiated to each block in one unit.

As described above, the optical recording medium and the reproducing apparatus using the diffraction grating of the present invention form a transmission film and a blocking film in the form of the diffraction grating on the track of the magneto-optical disk at right angles to the traveling direction of the track. Record and record the number of blocks and permeation membranes of the same standard and alternately formed in unit blocks, and record all signals with 8 types of blocks marked with different lengths of the slit and the membrane. As the laser beam is irradiated on a unit basis, the diffracted light having the maximum diffraction light having a specified diffraction angle is detected among the light diffracted differently in the slit according to the width of the blocking film and the slit, and a digital signal (3 bit) corresponding to 8 detected signals is selectively selected. It is possible to record the signal at high density even if there is no cross talk between codes by enabling serial output and playback. Does not deteriorate, and only the diffraction angle depends on the modulation transfer function because the slit and the barrier are formed with the same size and length in one block. There are very low features.

Claims (5)

The permeable membrane and the barrier membrane are alternately formed on the track in the form of a diffraction grating perpendicular to the direction of movement of the track, and the permeable membrane and the permeable membrane of the same number as the standard blocks are used as the unit blocks. An optical recording medium using a diffraction grating, characterized in that data is recorded differently to correspond to each data. The optical recording medium using a diffraction grating according to claim 1, wherein the data is recorded so as to have an inclined length equal to a period of the permeable membrane and the barrier membrane instead of alternately forming the permeable membrane and the barrier membrane. The optical recording medium using a diffraction grating according to claim 1 or 2, wherein three bits of the recording bit stream are recorded as one block with eight specific periods for each block. An optical recording medium recorded so as to output diffracted light at different angles in units of blocks using a diffraction grating, light irradiation means for irradiating light on a track of the optical recording medium in units of blocks, and the light irradiation means Light detecting means for detecting diffracted light diffracted at different angles as the light is irradiated, a block determining means for determining the type of the block by receiving the output of the light detecting means, and an output value of the block determining means. A bit table for outputting a digital signal corresponding to the bit signal, and a bit for outputting a digital signal output from the block determining means and the look table to the block determining means and the look table. An apparatus for reproducing an optical recording medium using a diffraction grating, comprising a clock and a synchronous detecting means. 5. An apparatus according to claim 4, wherein the light detecting means comprises a number of light receiving sensors corresponding to a specific period of the optical recording medium.