KR19990079123A - Optical pickup device and method for detecting playback signal and / or prepit header signal of optical disc - Google Patents

Abstract

Disclosed are a reproducing signal and / or a prepit header signal detecting method and an optical pickup apparatus of an optical disc capable of detecting a reproducing signal and / or a prepit header signal having reduced diffraction noise.

The method for detecting a reproduction signal and / or a prepit header signal of the disclosed optical disc uses an optical pickup device having a photodetector having at least two partition plates each independently photoelectrically converting the light disks. Receiving the light and photoelectrically converting the received light to output an electric signal; And comparing the electrical signals output from each of the dividers to select an electrical signal having a relatively high light intensity, wherein the selected electrical signal itself is used as a reproduction signal and / or a pre-fit header signal.

In addition, the optical pickup device, the light source; Optical path converting means for converting the advancing path of the incident light; An objective lens for focusing incident light to form an optical spot on the optical disk; A photodetector having at least two partition plates for receiving the light reflected from the optical disk and converting the light into independent electrical signals; A hologram element disposed between the optical path converting means and the photodetector and diffracting at least a portion of the light directed to the photodetector to separate from the main light; each independently, differentially or separately diffracting transmitted light received at each partition plate of the photodetector The summation can be used to detect the prepit header signal.

Description

Optical pickup device and method for detecting playback signal and / or prepit header signal of optical disc

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup apparatus, and more particularly, to an optical pickup apparatus having a structure capable of reducing diffraction noise of a header signal of a recording optical recording medium.

In general, an optical pickup apparatus records / reproduces information such as an image, sound, or data on an optical recording medium such as an optical disc, a card, or a tape with high density.

In particular, various types of optical discs are widely used as the optical recording medium. In order to increase the recording density within the limited recording area, a recording optical disc having a structure in which information can be recorded in each of lands and grooves has been proposed.

Referring to FIG. 1, the optical disk has a plurality of tracks 1 formed from an inner circumference to an outer circumference and interconnected in a spiral structure, each track 1 having a plurality of grooves G inserted into a predetermined depth and a disk. A plurality of lands L having a surface height of is formed. Here, the prepit header 2 is located between the land L and the groove G, between the land L and the land L, and between the groove G and the groove G. FIG. In addition, in the optical disc, a mirror area M is formed at the beginning of each track 1 to guide the movement of the track of the light spot 3 formed on the recording surface.

The prepit header 2 is positioned to be shifted by 1/2 track pitch (1/2 P) in the radial direction (R direction) of the disc with respect to the center of each track and is shared by two adjacent tracks. The pre-fit header 2 records header signals such as a variable frequency oscillator (VFO) signal, an address signal (AM) and a physical identification (PID) signal, and is synchronized with a phase locked loop (PLL). It has a reference signal to accurately generate a synchronization signal. In addition, information on the sector is stored.

The PID signal is a data signal including both information on the size of the minimum and maximum marks used in the user area such as land / groove, and is affected by diffraction noise when reproduced by a general optical pickup device. The causes of the diffraction noise include interference (crosstalk) effects from pits located in adjacent tracks and interference effects due to push-pull detection methods.

Here, as shown in FIG. 1, since the adjacent track Th of the header area is wider than the adjacent track Tu of the user area, crosstalk due to interference effects from pits located in adjacent tracks is relatively small. However, in the case of detecting the header signal by the push-pull method using a conventional optical pickup device, since it is obtained from the differential values of the signals E and F detected in the photodetector having at least a half-divided divider, Affected by the interference signal between the signals E and F, the diffraction noise due to the push-pull detection method is so large that it cannot be ignored.

Therefore, in the conventional optical pickup apparatus including a light source for irradiating light of 650 nm wavelength and an objective lens having a numerical aperture of 0.6 so as to be suitable for an optical disk having a high recording density, the above-mentioned diffraction in detecting the header signal recorded on the optical disk There is a problem that noise is largely generated, resulting in signal instability in the header area and inhibiting accurate signal detection.

Accordingly, the present invention has been made in view of the above-described point, and a first object is to reproduce and / or header a signal of an optical disc that can be less affected by diffraction noise when detecting a reproduction signal and a pre-fit header signal. It is to provide a detection method.

In addition, a second object of the present invention is to provide an optical pickup apparatus having an improved structure thereof so as to be less affected by diffraction noise when detecting a prepit header signal.

1 is a schematic view showing an optical disc for recording.

2 is a view showing an optical arrangement of a general optical pickup having two dividers.

3 is a flowchart illustrating a method of detecting a reproduction signal and / or a pre-fit header signal of an optical disc according to an embodiment of the present invention.

Figure 4 is a graph showing the pre-fit header signal A, B detected by the photodetector of the optical pickup apparatus according to the present invention.

FIG. 5 is a graph showing the sum or differential of the prefit header signals A and B of FIG.

6 is a view showing an optical arrangement of the optical pickup apparatus according to an embodiment of the present invention.

FIG. 7 is a schematic plan view of the hologram device shown in FIG. 5; FIG.

8 is a schematic plan view showing the photodetector shown in FIG.

9 is a view showing an optical arrangement of the optical pickup apparatus according to another embodiment of the present invention.

10 is a schematic view showing the photodetector shown in FIG.

11 is a graph showing a signal detected by one photodetector of the optical pickup apparatus according to the present invention.

<Explanation of symbols for the main parts of the drawings>

1 ... optical disc 11 ... light source

13 ... collimating lens 15 ... optical path changing means

16 ... 1/4 wavelength plate 17 ... Objective lens

19 ... Focus lens 20 ... Hologram element

21 ... first hologram area 22 ... first hologram pattern

23 ... 2nd hologram area 24 ... 2nd hologram pattern

30,40 ... photodetector

The present invention, in order to achieve the first object described above; Optical path converting means disposed between the light source and the optical disk and converting a traveling path of incident light; An objective lens disposed between the optical path converting means and the optical disk and focusing incident light to form an optical spot on the optical disk; And an optical detector having at least two split plates that are reflected by the optical disk and receive light incident through the objective lens and the optical path converting means and independently convert the received light into electric signals. A method for detecting a reproduction signal and / or a pre-fit header signal of an optical disc using a device, the method comprising: receiving light incident on each of the partition plates and photoelectrically converting the received light to output an electrical signal; And comparing the electrical signals output from each of the dividers to select an electrical signal having a relatively high light intensity. .

The present invention for achieving the above-described second object is a plurality of lands in which an information signal is recorded, a plurality of grooves each formed with a predetermined depth and recorded therein, between lands and grooves, between lands and lands, And / or having a pre-fit header formed between the grooves and the grooves for providing sector information, so that recording / reproducing of information can be performed on an optical disc including a plurality of tracks interconnected and each having a track pitch of a predetermined width. An optical pickup apparatus, comprising: a light source; An optical path converting means disposed between the light source and the optical disc and converting a traveling path of the incident light; An objective lens disposed between the optical path converting means and the optical disk and focusing incident light to form an optical spot on the optical disk; A photodetector having at least two split plates which are reflected by the optical disk and receive light incident through the objective lens and the optical path converting means and independently convert the received light into electric signals; A diffraction transmitted light received at each partition plate of the photodetector, including a hologram element disposed between the light path converting means and the photodetector and diffracting at least a portion of the light directed to the photodetector to separate from the main light The prepit header signal can be detected. In addition, the prepit header signal may be detected using only a part of the light incident on the photodetector without using the hologram element.

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

A method of detecting a reproduction signal and / or a pre-fit header signal of an optical disc according to an embodiment of the present invention is a crosstalk and / or pre-reproduction of a reproduction signal recorded on an optical disc as shown in FIG. 1 using a conventional optical pickup apparatus. Its characteristic is that the signal detection method is improved to reduce diffraction noise in the fit header signal.

A conventional optical pickup apparatus, as shown in FIG. 2, collects the light source 4, the optical path converting means 5 for converting the traveling path of the incident light, and the incident light so as to form an optical spot on the optical disk 1. The light reflected by the objective lens 6 and the optical disk 1 and received through the objective lens 6 and the optical path converting means 5 receives light and independently converts the received light into an electric signal. And a photodetector 7 having at least two partition plates. In FIG. 2, an example in which the photodetector has first and second split plates 7a and 7b is illustrated.

The signal detection method according to the present embodiment uses a portion of a signal output from the photodetector as a reproduction signal and a pre-fit header signal, which will be described with reference to FIG. 3. Here, the reference distinguished between the reproduction signal and the prepit header signal is determined according to the position of the light focused by the objective lens 6, and the detection signal when the optical spot is formed in the user area is the reproduction signal. The detection signal when the light spot is formed is a prepit header signal.

FIG. 3 shows a case in which the photodetector 7 capable of receiving all the light reflected from the optical disc 1 is composed of a first partition plate 7a of FIG. 2 and a second partition plate 7b of FIG. 2. It is shown as an example. Here, the signal received on the first split plate 7a and photoelectrically converted and output is defined as signal A, and the signal received on the second splitter 7b and photoelectrically converted and output is defined as signal B.

First, the light is reflected by the optical disc 1, and divided into the first and second split plates 7a and 7b to receive the light via the optical path converting means 5. The light received on each of the first and second split plates 7a and 7b is independently photoelectrically converted and then detected as a signal A and a signal B (S1). Thereafter, the light intensities of the signals A and the light intensities of the signals B output from each of the dividers are compared with each other (S2). Then, when the intensity of light of signal A is equal to or greater than the intensity of light of signal B, the signal A itself is used as a reproduction signal and / or a prepit header signal, and the intensity of light of signal A is the intensity of light of signal B. If smaller, the signal B itself is used as the reproduction signal and / or prepit header signal (S3). Here, in addition to comparing the light intensities between the signals A and B, it is also possible to select any one of the two signals A and B by comparing them with a jitter value for evaluating the characteristics of the optical disc 1.

The detection signal by this method is compared with the signal detected by the conventional method as follows. 4 is a graph showing signal characteristics when signals A and B are used by the method according to the present invention, and FIG. 5 shows signal characteristics when signals A and B are summed or differential as in the conventional method. The graph shown. In the drawing, the X axis represents the track position, and the Y axis represents the light intensity, that is, the light quantity ratio received by the photodetector with respect to the light quantity emitted from the light source.

As shown in Fig. 4, the waveforms of the signals A and B include diffraction noise. However, since the respective diffraction noises are about 5.7% with respect to the light intensity, they do not substantially affect the reproduction signal and the prepit header signal. On the other hand, as shown in FIG. 5, when the signals A and B are summed or differentially used, they occur when the diffraction noise is reinforced by the interference between the detection signals A and B, so that the diffraction noise is greatly increased. There is this. Therefore, when the reproduction signal and / or the prepit header signal are detected by the above method, the effect on the diffraction noise can be greatly reduced.

Hereinafter, an optical pickup apparatus according to a preferred embodiment of the present invention will be described in detail. As shown in FIG. 1, an optical pickup apparatus according to an exemplary embodiment of the present invention includes a plurality of lands in which an information signal is recorded, a plurality of grooves each formed at a predetermined depth, and grooves in which an information signal is recorded, and sector information. Provided with a pre-fit header, so as to perform recording / reproducing of information on an optical disc including a plurality of tracks interconnected and each having a track pitch of a predetermined width, and to reduce diffraction noise in the pre-fit header. The characteristic is that the structure is improved.

6 is a schematic diagram illustrating an optical arrangement of an optical pickup apparatus according to an embodiment of the present invention.

As shown, the light source 11, the optical path converting means 15 for converting the traveling path of the incident light, the objective lens 17 for focusing the incident light so as to form an optical spot on the optical disk 1, and the optical disk. A photodetector 30 for receiving the light reflected from (1) and converting it into an electrical signal, and a hologram element 20 for diffracting at least a portion of the light directed to the photodetector 30 to separate it from the main light; It is composed.

The light source 11 is composed of a semiconductor laser or the like for generating and irradiating a laser light having a predetermined wavelength, for example, 650 nm, which meets the standard of the optical disc 1.

The optical path converting means 15 is disposed on the optical path between the light source 11 and the optical disk 1, and changes the traveling path of the incident light. To this end, the optical path converting means 15 employs a polarization beam splitter and a quarter wave plate 16 to selectively transmit or reflect incident light according to its polarization component, as shown in FIG. A beam splitter that partially reflects, a hologram element having a pattern that allows light incident in one direction to pass through and diffracted light incident in the other direction may be employed. As described above, since a method of converting a traveling path of light using a beam splitter, a polarizing beam splitter, and a conventional hologram element is widely known, a detailed description thereof will be omitted.

The objective lens 17 is disposed on an optical path between the optical path converting means 15 and the optical disc 1, and is mounted on a normal actuator (not shown) in a direction for correcting a track error and a focus error. While driving, the light incident from the light source 11 is focused on the recording surface of the optical disc 1.

The photodetector 30 receives the light reflected from the optical disk 1 and entered through the objective lens 17 and the optical path converting means 15, and independently receives the received light as an electric signal. At least two partitioning plates are provided to detect a reproduction signal and / or a pre-fit header signal from each partitioning plate.

The hologram element 20 is disposed between the optical path converting means 15 and the photodetector 30, and functions to diffract some of the incident light and separate it from the main light. That is, as shown in FIG. 7, the hologram element 20 includes a first hologram region in which a first hologram pattern 22 is formed so that a portion of transmitted light is diffracted to one partition plate of the photodetector 30. 21 and a second hologram region 23 disposed adjacent to the first hologram region 21 and having a second hologram pattern 24 for diffracting a portion of the transmitted light to another partition plate. Circles 17 ′ shown by dotted lines in the figure represent cross-sections of light incident on the hologram element 20. Light passing through portions where the first and second hologram patterns 22 and 24 are not formed is The light transmitted as the main light and transmitted through the first and second hologram patterns 22 and 24 is diffracted. Here, the main light includes zero ordered light that is not diffracted and ± 1st order diffracted light diffracted by a pit signal, a prepit header signal, or the like of the optical disk 1.

As shown in FIG. 8, the photodetector 30 is preferably composed of six split plates. The primary light is received by the first and third split plates 31 and 32 disposed at the center, and independently outputs the signals A and B which are photoelectrically converted. Light diffracted by the first hologram pattern 22 is received by the third and fourth split plates 33a and 33b disposed on both sides of the first and second split plates 31 and 32, respectively. The light diffracted by the second hologram pattern 24 is formed in the fifth and sixth partition plates 34a and 34b disposed above and below the first and second partition plates 31 and 32, respectively. It is received.

Here, the light received by the third and fourth split plates 33a and 33b and the fifth and sixth split plates 34a and 34b independently outputs photoelectrically converted signals E and F. The signals are differentially offset according to the push-pull method and used for detecting the pre-fit header signal. In addition, the signals E and F may be summed, or the signals E and F may be used as prefit header signals.

In addition, the present invention preferably further includes a collimating lens 13 and a converging lens 19 in consideration of the optical arrangement of the optical members.

The collimating lens 13 is disposed between the light source 11 and the light path converting means 15, and converges diverged light emitted from the light source 11 to be parallel light. The converging lens 19 is disposed on the optical path between the hologram element 20 and the photodetector 30 to focus the incident parallel light.

9 is a schematic diagram illustrating an optical arrangement of an optical pickup apparatus according to another embodiment of the present invention.

As shown, the light source 11, the optical path converting means 15 for converting the traveling path of the incident light, the objective lens 17 for focusing the incident light so as to form an optical spot on the optical disk 1, and the optical disk. It comprises a photo detector 40 for receiving the light reflected from (1) and converting it into an electrical signal, the photo detector 40 can take the role of the hologram element 20 shown in FIG. It has its features.

Here, elements having the same reference numerals as the components described in the embodiment are substantially the same or similar functions, the detailed description thereof will be omitted.

Referring to FIG. 10, the photodetector 40 includes first and second partition plates 41 and 43 arranged symmetrically about a boundary line 40a on a straight line, and within the first partition plate 41. A third split plate 45 arranged to receive light diffracted on the optical disc 1 and to independently photoelectrically convert it, and other light arranged in the second split plate 43 and diffracted on the optical disc 1. And a fourth partitioning plate 47 which receives the light and independently photoelectrically converts it. Here, the prepit header signal is detected by a push-pull method that differentials the signals E and F detected by the third and fourth split plates 45 and 47 of the photodetector 40. In addition, the signals E and F may be used, or the signals E and F may be summed and used as a prepit header signal. In the figure, a circle 17 "represented by a dotted line represents a cross section of incident light.

As described above, by placing the hologram element to separate the diffracted light or by changing the structure of the photodetector, the characteristics of the reproduced signal are reduced by the effect of the noise from the diffraction of the E and F signals when detecting the prepit header signal. Can be improved.

11 is a graph illustrating a header signal detected by the optical pickup apparatus according to an embodiment of the present invention.

11 is a signal (signal A) detected by a partial partition of the photodetector detected by the method according to the present invention and some prepit header signals detected by the photodetector of the optical pickup apparatus according to an embodiment of the present invention. It is a graph comparing (signal E).

Comparing the portions 51 and 55 shown in a circle, the diffraction noise of the prefit header signal detected according to the method of the present invention is about 5.7%, and when the hologram element is employed, the diffraction noise is about 4.2%. It can be seen that it has. As a result, it can be seen that when the hologram element is further provided, the diffraction noise is further reduced by about 26% or more.

On the other hand, since the F signal exhibits a symmetrical signal characteristic with the above E signal, the diffraction noise is reduced like the above E signal.

In this case, even when the pre-fit header signal is detected by a push-pull or summation method that differentials the E signal and the F signal, it can be seen that a stable signal with reduced diffraction noise can be detected.

Therefore, the optical pickup apparatus configured as described above can reduce diffraction noise when an optical disc having a high density recording capacity is employed as the recording medium, so that a stable and good jitter value prepit header signal can be obtained.

Claims (6)

A light source; Optical path converting means disposed between the light source and the optical disk and converting a traveling path of incident light; An objective lens disposed between the optical path converting means and the optical disk and focusing incident light to form an optical spot on the optical disk; And an optical detector having at least two split plates that are reflected by the optical disk and receive light incident through the objective lens and the optical path converting means and independently convert the received light into electric signals. In the method for detecting the reproduction signal and / or pre-fit header signal of the optical disk using the device, Receiving light incident on each of the partition plates and photoelectrically converting each of the received lights to output an electric signal; Comparing the electrical signals output from each of the dividers to select an electrical signal having a relatively high light intensity; and using the selected electrical signal itself as a reproduction signal and / or a prepit header signal. A reproduction signal and / or pre-fit header signal detection method of an optical disc. A plurality of lands in which the information signal is recorded, each of which is formed at a predetermined depth, and formed in a plurality of grooves in which the information signal is recorded, between the lands and the grooves, between the lands and the lands, and / or between the grooves and the grooves, and provide sector information An optical pickup apparatus having a pre-fit header for enabling recording / reproducing of information on an optical disc including a plurality of tracks interconnected and each having a track pitch of a predetermined width. A light source; An optical path converting means disposed between the light source and the optical disc and converting a traveling path of the incident light; An objective lens disposed between the optical path converting means and the optical disk and focusing incident light to form an optical spot on the optical disk; A photodetector having at least two split plates which are reflected by the optical disk and receive light incident through the objective lens and the optical path converting means and independently convert the received light into electric signals; A diffraction transmitted light received at each partition plate of the photodetector, including a hologram element disposed between the light path converting means and the photodetector and diffracting at least a portion of the light directed to the photodetector to separate from the main light And the pre-fit header signal can be detected. 3. The hologram device of claim 2, wherein the hologram device comprises: a first hologram region in which a first hologram pattern is formed so that a portion of the transmitted light is diffracted to one partition plate; And a second hologram region in which a second hologram pattern is formed to diffract the plate. The collimating lens according to claim 2 or 3, further comprising: a collimating lens disposed between the light source and the light path converting means and focusing the incident light to be parallel light; And a converging lens disposed on an optical path between the hologram element and the photodetector to focus incident light. A plurality of lands in which the information signal is recorded, each of which is formed at a predetermined depth, and formed in a plurality of grooves in which the information signal is recorded, between the lands and the grooves, between the lands and the lands, and / or between the grooves and the grooves, and provide sector information. And a pre-fit header for recording / reproducing information on an optical disc including a plurality of tracks interconnected and each having a track pitch of a predetermined width. A light source; An optical path converting means disposed between the light source and the optical disc and converting a traveling path of the incident light; An objective lens disposed between the optical path converting means and the optical disk and focusing incident light to form an optical spot on the optical disk; An optical pickup apparatus comprising a photodetector reflected from the optical disk and receiving light incident through the objective lens and the optical path converting means and converting the received light into an electrical signal independently. The photodetector comprises: first and second split plates disposed symmetrically about a boundary line on a straight line; A third split plate disposed in the first split plate to receive light diffracted by the optical disk and to independently photoelectrically convert the light; A fourth partitioning plate disposed in the second partitioning plate and receiving another light diffracted by the optical disk and independently photoelectrically converting the light into the second partitioning plate, using the signals detected by the third and fourth partitioning plates; And / or the pre-fit header signal can be detected. The collimating lens of claim 5, further comprising: a collimating lens disposed between the light source and the light path converting means, the collimating lens focusing incident light to be parallel light; And a converging lens disposed on an optical path between the optical path converting means and the photodetector to focus incident light.