KR100611465B1 - Holographic data storage medium for disk and method for controlling servo using the same - Google Patents

Abstract

The disc-shaped holographic data storage medium according to the present invention has a track structure located on the incident surface of the holographic light, and includes a hologram layer into which an object light containing input data, a reference light for recording (or reproduction), and a servo light are incident; And a reflection layer formed under the hologram layer to reflect the incident object light and the reference light and transmitting servo light, and formed under the reflection layer to have the same track structure as the track structure of the hologram layer and synchronized at predetermined intervals for each track. It is formed in the pattern, characterized in that made of a servo layer that reflects the servo light, but reflects at a different reflectance whenever the servo light is incident on the synchronous pattern.

As described above, the present invention further forms a servo layer including a synchronization pattern for sector division in the holographic data storage medium, so that servo control can be effectively performed during data reproduction and recording.

Description

Disk type holographic data storage medium and servo control method using the same {HOLOGRAPHIC DATA STORAGE MEDIUM FOR DISK AND METHOD FOR CONTROLLING SERVO USING THE SAME}             

1 is a structural diagram showing a disc-shaped holographic data storage medium according to the present invention;

2 is a top view of a disc-shaped holographic data storage medium according to the present invention,

FIG. 3 is a diagram illustrating a superimposition direction of holographic light when recording and reproducing holographic data by shift superposition in the present invention.

FIG. 4 is a diagram for explaining a region in which overlap occurs when data is recorded and reproduced by shift overlap in the present invention.

5 and 6 are exemplary diagrams for explaining a servo control process using a disc type holographic storage medium according to the present invention.

<Description of the code | symbol about the principal part of drawing>

100 hologram layer 102 protective layer

104: reflective layer 106: servo layer

106a: Sync Pattern

The present invention relates to a holographic data storage medium, and more particularly, to a disc-shaped holographic data storage medium having a track structure and a servo control method using the same.

Unlike conventional optical disks, in which data in units of bits is inputted and outputted serially, the holographic data storage and reproducing system is characterized in that data in units of pages is inputted and outputted, and overlaps in the same area. For this reason, the address arrangement and the servo control method cannot be the same as the conventional optical disk driver.

In general, in an ROM type optical disk drive, addressing and data recording are performed using a physical protrusion called a pit, and servo control is performed using the protrusion. Pits have several different lengths. In the CD series, all data is represented by 12 feet of 3T to 11T and 9 feet for the DVD series. In expressing addressing and data using these pits, addressing represents time information starting with a combination of specific pits that do not use general data in the representation. This is called Q code in ROM disks, and a combination of these pits is used to represent an address in a spiral arrangement from the inner circumference of the disk to the outside.

Unlike a ROM type disk drive, a recordable optical disc drive that generates a pit by recording and writes an address and data uses a different address implementation method than the ROM type. In order to record data, there must be some standard information. In the recording type disc, a method slightly changed according to the type of optical disc is adopted. In the case of a CD-R / CD-RW, an address of a disc is represented by using an Absolute Time In Pre-Groove (ATIP) method, which makes a wobbling structure called a wobble on the recording surface and addresses it. This is because the wobble is artificially generated so that the groove has a sinusoidal shape and can separate a signal having two frequency bands from a tracking error when the disc is rotated at a constant linear velocity. At this time, if the frequency variation (low frequency-> high frequency, high frequency-> low frequency) occurs as a reference time, the information is 1, and if there is no frequency variation (high frequency-> high frequency, low frequency-). Low frequency) uses a Bi-Phase technique that records information at zero.

Although some changes are made depending on the type of disc, basically a DVD-recordable disc except DVD_RAM adopts a similar method. DVD + RW records the address using ADIP (Address In Pre-groove) and DVD-RW uses LPP (Land Pre-Pit) method.

The DVD-RAM addressing method adopts a CAPA (Complimentary Allocated Pit Addressing) method to separate recording and playback data into zones, and is distinguished from other media in appearance. In the case of other DVD recorders, the color of the recording surface is the same and flat disk, whereas in DVD-RAM, each zone for sector division is clearly visible. This form can also be found in MO (Magnetic Optical), where the MO adopts sample servo without performing continuous servo. Similarly, HDDs use an addressing method that divides a disk into zones and sectors and uses header information that is the first part of each sector.

As described above, the addressing method of the optical disc differs depending on the recording and reproduction method, the track pitch, and the operation of the optical disc. However, in general, the conventional optical disk has a feature of writing an address in series and using only one-dimensional data. However, in the case of a holographic data storage system, data input and output is performed in parallel, and has an overlapping feature of recording and reproducing data in the same place. Therefore, pages and pages serving as basic input / output units correspond very similarly to the conventional concept of pits or wobbles, which means that there is a limit in encoding all address information in a track in consideration of overlapping characteristics.

For this reason, there is a need for an address arrangement and servo method suitable for the characteristics of the holographic data storage system.

 Accordingly, the present invention has been made to solve the above problems, by forming a servo layer on the holographic data storage medium having a synchronous pattern reflecting the servo light at different reflectances to perform servo control when recording and reproducing data. It is an object of the present invention to provide a disk-type holographic data storage medium and a servo control method using the same.

In order to achieve the above object, the present invention records data on a holographic data storage medium in units of pages using an object light and a holographic light as a reference light for recording, and a reference light for reproduction which is a holographic light on the holographic data storage medium. A holographic data storage and reproducing system for reproducing data in units of pages by injecting the light, wherein the holographic data storage medium has a track structure on an incident surface of the holographic light, and includes the object light including input data, A hologram layer to which recording (or reproduction) reference light and servo light are incident, a reflection layer formed below the hologram layer to reflect the incident object light and reference light, and transmitting the servo light, and formed below the reflection layer To have the same track structure as that of the hologram layer Group is formed with the synchronization pattern at intervals set up in the respective tracks, sikidoe reflects the servo light, the servo light is characterized by being a servo layer for reflecting a different reflection factor each time the incident on the synchronization pattern.

In addition, the present invention comprises a hologram layer having a track structure and a holographic layer into which holographic light is incident to record and reproduce data, and a servo layer having the same structure as the track structure and formed in a synchronous pattern at predetermined intervals to reflect the servo light. 10. A servo control method of a holographic data storage and reproducing system comprising a disk-shaped holographic data storage medium and an n (n≥2 natural number) divided photodiode which receives a servo light reflected from the servo layer and detects light quantity. Receiving light reflected from the servo layer when the light is incident on the hologram layer with the n-divided photodiode, calculating an amount of light of each divided region of the n-divided photodiode, and then calculating an area information signal Determining whether the area information signal is generated as a result of the calculation; As a result of the determination, it is determined that the holographic light is incident on the track when the area information signal is generated at a predetermined period, and when the area information signal is not generated, the holographic light is incident between the track and the track. Determining.

The above and other objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention. 1 is a structural diagram showing a disc-shaped holographic data storage medium according to the present invention, FIG. 2 is a top view of a disc-shaped holographic data storage medium according to the present invention, and FIG. 3 is a diagram illustrating shifting holographic data in the present invention. 4 is a diagram illustrating an overlapping direction of holographic lights when recording and reproducing by overlapping, FIG. 4 is a view for explaining a region where overlapping occurs when recording and reproducing data by shift overlapping in the present invention, and FIGS. 5 and 6 Exemplary diagram for explaining a servo control process using a disk-type holographic storage medium according to the present invention.

As shown in FIG. 1, a disc-shaped holographic data storage medium is an information recording layer on which data is recorded using volume holography, and a hologram layer 100 and a reflective layer 102 on both sides of the hologram layer 100 and a protective layer. The layer 104 is formed, and the servo layer 106 is formed on the lower surface of the reflective layer 102. At this time, the servo layer 106 is formed with a synchronization pattern 106a containing information for performing focus servo and tracking servo and address information.

Servo light for tracking and focus servo control is incident on the holographic data storage medium, and reference light and object light for storing the holographic data on the holographic data storage medium are incident or data recorded on the holographic data storage medium is stored. A reproduction reference light and a servo light are incident to reproduce.

The interference pattern caused by the interference between the recording reference light and the object light is recorded in the hologram layer 100, and data may be recorded by overlapping the same area by changing the incident angle of the recording reference light. At this time, the reproducing or recording reference light and the object light are reflected in the reflective layer 102 of the holographic data storage medium, and the servo light is transmitted through the reflective layer 102 to be incident on the servo layer 106.

The hologram layer 100 has a track structure like a general optical disk, and the servo layer 106 also has the same track structure as the track structure of the hologram layer 100.

As shown in FIG. 2, the servo layer 106 is formed in the sync pattern 106a at predetermined intervals for each track 300, and the sync pattern 106a is optically grooved or landed. It may have a shape that is much higher or lower than the reflectance of the land portion. That is, the sync pattern 106a reflects the servo light with a higher or lower reflectance than other regions of the servo layer 106. Therefore, when the servo light passes through the sync pattern 106a, since the reflectance of the servo light changes in the sync pattern 106a, the servo light may be sensed to distinguish each sector 300a of the track 300. That is, in the synchronization pattern 106a, a sector light is generated which can distinguish the sectors by reflecting the servo light.

Here, the area between the sync patterns 106a in each track 300 may be defined as one sector.

In the case of using shift multiplexing as a superposition method of holographic data, as shown in FIG. 3, a spot of light needs to overlap both the rotational direction and the circumferential direction of the disc.

Assuming that the size of the recording reference light and the object light are shifted overlap in the direction of the center of the holographic data storage medium in the shift overlap, the area where the overlap occurs can be divided into two types, as shown in FIG. 4. In the first case, it is possible to overlap in the area between the tracks, and in the second case, it can be directly over the track. Here, the track pitch is independent of the size of the holographic light because the holographic light, which is the reference light and the object light for recording and reproduction, and the servo light for the servo, operate on different films. Depends. What is important in the present invention is that it is important to distinguish whether the overlapped area is the area A or the area B during recording. That is, tracking servo control is required.

Servo light (E, F) incident on the servo layer 106 of the holographic data storage medium is reflected and is incident on the photodiode A and photodiode B, which are light detection means, as shown in FIG. Is an undivided photodiode, and photodiode B may be a four-divided photodiode or a photodiode divided into more. At this time, the sensitivity of the cell of the photodiode A and the cell of the photodiode B is equally adjusted or corrected through signal processing. The function of the photodiode B cell is used to detect the sector sync signal that distinguishes the sector A or region B and the sectors of the track.

That is, when the holographic data superposition occurs in a normal track, as shown in FIG. 5, the holographic light is incident on the track, and the servo light is a region between the track and the upper track where the holographic light is incident and the holographic light. It will be incident on the area between the incident track and the track below. Servo light E incident on the area between the track where the holographic light is incident and the upper track is reflected by the servo layer 106 and is incident on the photodiode B, and is located in the area between the track where the holographic light is incident and the track below. The incident servo light F is reflected by the servo layer 106 and incident on the photodiode A. The zone information signal and the sector synchronization signal can be known through the amount of light incident on the respective divided regions a, b, c, and d of the photodiode B. That is, the area information signal is a value obtained by subtracting the sum of the amounts of light detected in the partitions a and b and the sum of the amounts of light detected in the partitions c and d. The sum of the amounts of light detected in the regions b and c is obtained.

At this time, when the holographic data superimposition recording is normally performed on the track, that is, when the tracking servo control is properly operated according to the time change, the area information signal is changed at a predetermined period as shown in FIG. 5, and the sector synchronization is performed. The signal will need correction since two signals per sync pattern 106a are detected. Thus, when the sector synchronizing signal and the area information signal are observed as shown in Fig. 5, it can be seen that the light for holographic recording and reproduction is incident on the normal track, i.e., the area A.

In the second case, when the holographic light for recording and reproducing holographic data is incident between the track and the track, as shown in Fig. 6, no area information signal is generated and the sector synchronization signal is generated by the servo layer. It is generated every time it is incident on the synchronization pattern 106a of the 106.

As mentioned above, although this invention was demonstrated concretely based on the Example, this invention is not limited to this Example, Of course, various changes are possible within the range which does not deviate from the summary of the claim described below. .

As described above, the present invention further forms a servo layer including a synchronization pattern for sector division in the holographic data storage medium, thereby effectively performing servo control during data reproduction and recording.

Claims (10)

The data is recorded in the holographic data storage medium by using the object light and the holographic light as the reference light for recording, and the reproduction of the data in the page unit is made by injecting the reproduction reference light which is the holographic light into the holographic data storage medium. Holographic data storage and playback system, The holographic data storage medium, A hologram layer positioned on an incidence plane of the holographic light and having a track structure, to which the object light, the reference light for recording (or reproduction), and the servo light containing the input data are incident; A reflection layer formed under the hologram layer to reflect the object light and the reference light incident thereto, and to transmit the servo light; When formed in the lower portion of the reflective layer and having the same track structure as the track structure of the hologram layer and formed in a synchronous pattern at predetermined intervals on each track, reflecting the servo light, when the servo light is incident on the synchronous pattern Disc-shaped holographic data storage medium, characterized in that consisting of a servo layer that reflects at different reflectances. The method of claim 1, The holographic data storage and playback system, A n (n ≧ 2 natural number) split photodiode, which is a light detection means for receiving the servo light reflected from the servo layer and detecting the amount of light, An area information signal and a sector synchronization signal are detected by calculating the amount of light detected in each partition of the n-divided photodiode, and the incident position of the holographic light is controlled using the area information signal and the sector synchronization signal. Disc-shaped holographic data storage medium. The method of claim 2, And the light detecting means is any one of a four-, six-, and eight-segment photodiode. The method of claim 2, And the holographic data storage and reproducing system determines that the holographic light is incident on the track when the area information signal is generated at predetermined intervals and two sector synchronization signals are generated per synchronization pattern. Holographic data storage medium. The method of claim 2, The holographic data storage and reproducing system is characterized by determining that the holographic light is incident between the track and the track when the sector information signal is not generated for each sync pattern without generating the area information signal. Graphic data storage medium. The method of claim 1, A disk-shaped holographic data storage medium, characterized in that the protective layer is formed on the hologram layer. The method of claim 1, And the address information and the information for tracking and focus servo control are recorded in the synchronization pattern. Disk-type holographic data storage comprising a hologram layer having a track structure and holographic light incident and recording and reproducing data, and a servo layer having the same structure as the track structure and formed in a synchronous pattern at predetermined intervals to reflect servo light. A servo control method of a holographic data storage and reproducing system composed of an n (n≥2 natural number) divided photodiode which receives a medium and servo light reflected from the servo layer and detects light quantity. Receiving light reflected from the servo layer when the holographic light is incident on the hologram layer to the n-divided photodiode; Calculating an area information signal after calculating an amount of light of each divided area of the n divided photodiode; Determining whether the area information signal is generated as a result of the calculation; As a result of the determination, it is determined that the holographic light is incident on the track when the area information signal is generated at a predetermined period, and when the area information signal is not generated, the holographic light is incident between the track and the track. Judgment Step Servo control method using a disk-type holographic data storage medium comprising a. The method of claim 8, In the calculating step, the sector control signal is calculated by calculating the amount of light in each of the divided regions, the servo control method using the disc-shaped holographic data storage medium. The method of claim 9, In the sector sync signal, two signals per sync pattern are detected when the holographic light is incident on the track, and one signal per sync pattern is detected when the holographic light is incident between the track and the track. Servo control method using a disc-shaped holographic data storage medium, characterized in that the detection.

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