JPH07129962A - Optical recording/reproducing device - Google Patents

Abstract

PURPOSE:To eliminate cross talk and to reduce the increase in jitters even when a pitch of an information track is narrowed. CONSTITUTION:This device is provided with ultra resolution spot irradiation means 21, 23, a photodetector 34 provided with a main light receiving part receiving a reflected beam from one information track and two sublight receiving parts respectively receiving the reflected beam from two parts adjacent to the one information track and an operation processing means operation processing the output signal of the main light receiving part and the output signals of two sublight receiving parts so as to eliminate the influence of the reflected beam from the adjacent information track contained in the reflected beam from the one information track.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for recording / reproducing information on / from an information track of an optical recording medium.

2. Description of the Related Art In an optical recording / reproducing apparatus, an optical recording medium capable of recording, reproducing or erasing information on an information track should reproduce information on one information track from a light source through an objective lens. Information is reproduced based on the reflected light by irradiating a minute light spot. In recent years, an optical recording / reproducing apparatus for optically recording and reproducing information such as digitized code data, video, music, etc. on an optical recording medium has been increased in capacity. As a method of increasing the capacity of the optical recording / reproducing apparatus, there is a method of narrowing the pitch of information tracks on the optical recording medium in order to increase the recording density. In addition, in Japanese Patent Laid-Open No. 5-36083, in an optical recording / reproducing apparatus,
The reflected light from the optical recording medium composed of the optical disc is received by the three-division light receiving element parallel to the information track, and the output signal of each divided portion of the three division light receiving element is calculated to obtain a reproduction signal with a small crosstalk. It is described in the above. Further, in the optical recording / reproducing apparatus described in Japanese Patent Application Laid-Open No. 5-36083, it is proposed that the tilt amount of the optical disc is detected and the gain at the time of calculation for removing crosstalk is changed according to the tilt amount detected by the optical disc. ing.

In the method of increasing the capacity of the information reproducing apparatus by narrowing the pitch of the information tracks on the optical recording medium, the size a of the optical spot on the optical recording medium is the wavelength λ of the light source. A = k depending on the numerical aperture NA of the objective lens
It is determined by λ / NA (k: constant), and there is a limit to the size a of the optical spot. FIG. 7 shows a case where the diameter a of the optical spot 11 and the pitch δ of the information track 12 are substantially equal. In this case, the light spot 11 is irradiated onto one information track on which information is to be reproduced, and the peripheral portion of the light spot 11 does not overlap the information track adjacent to the one information track, and It is possible to reproduce the information accurately. FIG. 8 shows a case where the pitch of the information tracks 12 is set to 1 / 2δ in order to improve the recording density. In this case, the peripheral portion of the light spot 11 covers two information tracks adjacent to both sides of one information track for reproducing information, and not only one information track for reproducing information but also two adjacent information tracks for both sides thereof. Information is read simultaneously from one information track. As a result, crosstalk increases and jitter increases, which makes it impossible to accurately detect information from one information track. The present invention solves the above-mentioned drawbacks, and even when the pitch of information tracks on an optical recording medium is narrowed, crosstalk can be removed and an increase in jitter can be reduced, enabling accurate information detection. An object is to provide a reproducing device.

In order to achieve the above object, the invention according to claim 1 is one piece of information to be reproduced on an optical recording medium capable of recording and reproducing information on an information track. In an optical recording / reproducing apparatus that irradiates a minute light spot on a track and reproduces information based on the reflected light, a super-resolution spot is used as the light spot in a direction intersecting the information track with respect to the optical recording medium. From a super-resolution spot irradiating means for irradiating, a main light receiving portion for receiving the reflected light from the one information track, and two portions adjacent to each other in the direction crossing the one information track in the optical recording medium. A photodetector having two sub-light-receiving parts for receiving the respective reflected lights, and the one information track included in the reflected light from the one information track in the photodetector. And an arithmetic processing means for arithmetically processing the output signals of the main light receiving portion and the two sub light receiving portions so as to remove the influence of reflected light from two information tracks adjacent to the track. is there. Claim 2
In the optical recording / reproducing apparatus according to claim 1, when the output signal of the main light receiving portion is i and the output signals of the two sub light receiving portions are j and k, the arithmetic processing means is an information signal. = {Αi− (β ₁ j + β ₂ k)} α, β ₁ , β ₂ : constant β ₁ = β _{2 The} information signal is detected by the arithmetic processing. According to a third aspect of the present invention, in the optical recording / reproducing apparatus according to the first or second aspect, when the optical recording medium is tilted in the radial direction, the arithmetic processing means outputs an information signal = {αi- (β ₁ j + β ₂ k )} Α, β ₁ , β ₂ : The information signal is detected by the arithmetic processing with the constant β ₁ ≠ β ₂ . According to a fourth aspect of the present invention, in the optical recording / reproducing apparatus according to the first aspect, a tracking signal detecting means for obtaining a tracking signal by calculating a difference between output signals of the two sub light receiving portions is provided. According to a fifth aspect of the present invention, in the optical recording / reproducing apparatus according to the first aspect, tilt signal detecting means for obtaining the tilt signal in the radial direction of the optical recording medium by taking the difference between the output signals of the two sub-light-receiving units. Be prepared.

According to the present invention, the super-resolution spot irradiating means irradiates the super-resolution spot as a light spot on the optical recording medium in a direction intersecting the information track, and the main light receiving section reproduces information. The reflected light from one information track to be received is received, and the two sub-light-receiving portions respectively receive reflected light from two parts adjacent to each other in the direction intersecting with the one information track in the optical recording medium. And
The arithmetic processing means outputs the output signal of the main light receiving unit so as to remove the influence of the reflected light from the two information tracks adjacent to the one information track included in the reflected light from the one information track in the photodetector. The output signals of the two sub light-receiving units are arithmetically processed. According to a second aspect of the invention, in the optical recording / reproducing apparatus according to the first aspect, the arithmetic processing means is: information signal = {αi- (β ₁ j + β ₂ k)} α, β ₁ , β ₂ : constant β ₁ = β _The information signal is detected by the arithmetic processing of ₂ . In the invention of claim 3, wherein, in the optical recording and reproducing apparatus according to claim 1 or 2, wherein the arithmetic processing means the information signal when the optical recording medium is tilted in the radial direction _{= {αi- (β 1 j +} β 2 k)} α, β ₁ , β ₂ : The information signal is detected by the arithmetic processing in which the constant β ₁ ≠ β ₂ . According to a fourth aspect of the invention, in the optical recording / reproducing apparatus according to the first aspect,
The tracking signal detection means obtains the tracking signal by taking the difference between the output signals of the two sub light receiving portions. According to the invention of claim 5, in the optical recording / reproducing apparatus of claim 1,
The tilt signal detection means obtains the tilt signal in the radial direction of the optical recording medium by taking the difference between the output signals of the two sub light receiving parts.

FIG. 1 shows an embodiment of the present invention. In this embodiment, an optical recording medium capable of recording, reproducing or erasing information on an information track is irradiated with a minute light spot on one information track on which information is to be reproduced, and the information is reflected based on the reflected light. It is an example of an optical recording / reproducing apparatus for reproducing the. The light emitted from the semiconductor laser 21 is collimated by the collimator lens 22, and the light in the central portion thereof is blocked by the light shielding band 23, transmitted through the beam splitter 24, and the optical path is bent by the deflection prism 25. This deflection prism 2
The light from 5 is condensed by the objective lens 26 and irradiated as a minute light spot on the recording surface of the optical recording medium 27 composed of an optical disk. The optical disc 27 has information tracks 27a formed concentrically or spirally, and is rotationally driven by a spindle motor. Here, the light incident on the objective lens 26 is shielded at its central portion by the light shielding band 23, and the light spot formed on the optical disk 27 is a so-called super-resolution spot. The super-resolution spot is composed of a main lobe of light from the objective lens 26, a main spot formed by two side lobes, and two side spots. The main spot and the two side spots are orthogonal to the information track on the optical disc 27. Direction (track direction). This super-resolution spot is formed as a minute light spot by making the main spot smaller than in the case where there is no light shielding by the light shielding band 23, and side lobes are emphasized. FIG. 2 shows the relationship between the information track 27a on the optical disc 27 and a normal light spot 28 which is not shielded by the shield band 23.
FIG. 3 shows the relationship between the information track 27a on the optical disc 27 and the super-resolution spot 29. 2 and 3, the wavelength of light from the semiconductor laser and the numerical aperture NA of the objective lens are the same. In the super-resolution spot 29, the diameter of the main spot 29a in the track direction becomes smaller than the diameter of the normal optical spot in the track direction, and the information track 27a
It is possible to increase the recording density by narrowing the pitch of. Further, in the super-resolution spot 29, the main spot 29a is irradiated to one information track from which information is to be reproduced, and the side spots 29b and 29c are applied to two information tracks adjacent to the one information track.
The information on one information track can be read by the reflected light of the side lobes. As shown in FIG. 1, the light reflected by the optical disc 27 is reflected by the beam splitter 24 after passing through the objective lens 26 and the deflection prism 25,
The light is condensed by the condenser lens 30 and enters the beam splitter 31. The light reflected by the beam splitter 31 is given astigmatism by the cylindrical lens 32, and is received by the photodetector 33 including a four-division light receiving element. The four-division light-receiving element 33 is a servo signal detecting element, and the focusing signal is obtained by calculating the output signal of each divided portion of the four-division light-receiving element 33 by the arithmetic circuit by the astigmatic method. Further, the tracking signal is obtained by calculating the output signal of each divided portion of the 4-division light receiving element 33 by the push-pull method by the arithmetic circuit. The light transmitted through the beam splitter 31 is a photodetector 3 including a three-division light receiving element for information signal detection, which is arranged near the condensing point.
The light is received by the four, and as shown in FIG.
4 is three light receiving parts 34a divided into three in the track direction,
It has 34b and 34c. These light receiving parts 34a, 34
The central light receiving portion 34a of b and 34c serves as a main light receiving portion that receives the main lobe of the light from the beam splitter 31, and the light receiving portions 34b and 34c on both sides thereof receive the side lobe of the light from the beam splitter 31. It becomes a sub light receiving part. The output current signal i of the main light receiving portion 34a is converted into a voltage signal αi by the current / voltage converter 35, and the output currents j and k of the sub light receiving portions 34b and 34c are converted into the voltage signal β by the current / voltage converters 36 and 37, respectively. ₁ j, β ₂ k
Is converted to. Here, α, β ₁ , β ₂ are constants determined by the current / voltage converters 35, 36, 37, and are determined so that the jitter becomes the smallest. When the heights (strengths) of the side lobes are equal, β ₁ = β ₂ . The output signals β ₁ j and β ₂ k of the current converters 36 and 37 are added by the adder 38 to become (β ₁ j + β ₂ k), and the subtractor 39 outputs the output signal αi of the current converter 35 to the adder 38. The output signal (β ₁ j + β ₂ k) is subtracted and {αi− (β ₁ j + β ₂
k)} is obtained. As shown in FIG. 6, during reproduction in which the super-resolution spot 29 is irradiated on the information track 27a in which the information pits 27b on the optical disc 27 are recorded, the light receiving portions 34a, 34 of the three-divided light receiving element 34 are reproduced.
The output signals i, j, k of b, 34c are as shown in FIG. 6, and the output signal i of the main light receiving section 34a includes two information tracks adjacent to both sides of one information track for reproducing information. Although the crosstalk component is included, the information signal {αi− (β ₁ j + β ₂ k)} from the subtractor 39 has the crosstalk component removed. When the optical disk 27 is tilted (tilted) in the radial direction, the heights of two side lobes of the reflected light from the optical disk 27 are different as shown in FIG.
The tilt of the optical disk 27 is detected by calculating the difference between the output signals β ₁ j and β ₂ k of 6, 37 and the height difference between the two side lobes. When the subtracter detects that the optical disk 27 is tilted in the radial direction, a circuit (not shown) operates and the current converters 36 and 3 are operated.
The current converters 36 and 37 are controlled so that β ₁ j ≈β ₂ k when reproducing the unrecorded portion on the optical disc 27 (when the light spot is irradiated to the unrecorded portion) by controlling the gain of _{No. 7.}
The constants β ₁ and β ₂ are determined to reduce the jitter (crosstalk). In this case, β ₁ ≠ β ₂ . In this embodiment, each of the light receiving portions 34a, 3a of the three-divided light receiving element 34 is
Since the information signals {αi- (β ₁ j + β ₂ k)} are obtained by processing the output signals i, j, k of 4b and 34c, it is possible to suppress the increase in jitter due to the narrow pitch of the information track 27a. It is possible and the light spot is a super-resolution spot 2
As a result, the pitch of the information tracks 27a can be further narrowed. Moreover, the side lobe enables the information to be reproduced from the two information tracks adjacent to both sides of the one information track from which the information should be reproduced, and crosstalk can be removed more easily. Further, when it is detected that the optical disc 27 is tilted in the radial direction, the current converters 36 and 3 are detected.
Since the constants β ₁ and β ₂ of 7 are variable, crosstalk can be satisfactorily removed. Furthermore, the current converters 36, 3
Of the output signals β ₁ j and β ₂ k of the optical disc 27
Since the tilt of the optical disc 27 is detected, the tilt of the optical disc 27 can be easily detected. In this embodiment, crosstalk removal can be most efficiently performed because the pitch of the information track 27a is larger than the diameter of the main spot by the main lobe and the side lobe peaks are on both sides of one information track from which information should be reproduced. This is the case in the vicinity of the center of two adjacent information tracks. In the above embodiment, since the main lobe 29a and the two side lobes 29b and 29c irradiate one information track from which information is to be reproduced and two information tracks adjacent to both sides of the information track, three optical beams are applied to the optical disk. In the three-beam method of irradiating a laser beam to reproduce and record information, the output signals β ₁ j and β ₂ of the current converters 36 and 37 are substantially the same as when the tracking signals are detected from the three reflected lights from the optical disk.
The difference of k may be taken by a subtractor to detect the tracking signal. With this configuration, the light receiving element for detecting the focusing signal and the light receiving element for receiving the tracking signal can be separated, and the interference between the two servo signals (focusing signal and tracking signal) is eliminated.

As described above, according to the first aspect of the present invention, a minute information track is to be reproduced on an optical recording medium capable of recording and reproducing information on the information track. In an optical recording / reproducing apparatus that irradiates a light spot and reproduces information based on the reflected light, a super-resolution spot that irradiates the optical recording medium with a super-resolution spot in a direction intersecting an information track Spot irradiation means, a main light receiving portion for receiving reflected light from the one information track, and reflected light from two portions adjacent to each other on the optical recording medium in a direction intersecting with the one information track, respectively. A photodetector having two sub-light-receiving parts for receiving light, and two photodetectors adjacent to the one information track included in the reflected light from the one information track in the photodetector. Since the output signal of the main light receiving portion and the output signal of the two sub light receiving portions are arithmetically processed so as to remove the influence of the reflected light from the information track, the information track on the optical recording medium is provided. Even if the pitch is narrowed, crosstalk can be removed and the increase in jitter can be reduced, and accurate information detection can be performed, and the pitch of the information track can be further narrowed by using the light spot as a super-resolution spot. . Moreover, the side lobe enables the information to be reproduced from the two information tracks adjacent to both sides of the one information track from which the information should be reproduced, and crosstalk can be removed more easily. According to a second aspect of the present invention, in the optical recording / reproducing apparatus according to the first aspect, when the output signal of the main light receiving unit is i and the output signals of the two sub light receiving units are j and k, the calculation is performed. The processing means detects the information signal by an arithmetic process such that information signal = {αi− (β ₁ j + β ₂ k)} α, β ₁ , β ₂ : constant β ₁ = β _2.
Similar to the described optical recording / reproducing apparatus, even if the pitch of the information tracks on the optical recording medium becomes narrow, crosstalk can be removed and the increase in jitter can be suppressed, and accurate information detection can be performed. According to a third aspect of the invention, in the optical recording / reproducing apparatus of the first or second aspect, when the optical recording medium is tilted in the radial direction, the arithmetic processing means outputs an information signal = {αi- (β ₁ j + β ₂ k)} α, β ₁ , β ₂ : Since the information signal is detected by the arithmetic processing of constant β ₁ ≠ β ₂ , crosstalk can be satisfactorily removed. According to the invention of claim 4, in the optical recording / reproducing apparatus of claim 1,
Since the tracking signal detecting means for obtaining the tracking signal by obtaining the difference between the output signals of the two sub light receiving portions is provided, a light receiving element for detecting the focusing signal,
The light receiving element for receiving the tracking signal can be separated, and the interference between the two servo signals is eliminated. According to a fifth aspect of the present invention, in the optical recording / reproducing apparatus according to the first aspect, tilt signal detection for obtaining a tilt signal in a radial direction of the optical recording medium by taking a difference between output signals of the two sub light-receiving units. Since the means is provided, it is possible to easily detect the tilt in the radial direction of the optical recording medium.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an information track on an optical disc and a normal light spot.

FIG. 3 is a diagram showing a relationship between an information track on an optical disc and a super-resolution spot in the above embodiment.

FIG. 4 is a block diagram showing a part of the above embodiment.

FIG. 5 is a diagram showing the relationship between information tracks and super-resolution spots when the optical disc is tilted in the radial direction in the above embodiment.

FIG. 6 is a diagram for explaining the operation of the above embodiment.

FIG. 7 is a plan view showing a case where a diameter a of an optical spot and a pitch δ of an information track of a conventional device are substantially equal to each other.

FIG. 8 is a plan view showing a case where the pitch of information tracks is ½δ in the conventional device.

[Explanation of symbols]

 21 Optical Disc 22 Collimating Lens 23 Light-Shielding Band 24, 31 Beam Splitter 25 Deflection Prism 26 Objective Lens 27 Optical Disc 30 Condensing Lens 32 Cylindrical Lens 33 4-Division Photoreceptor 34 3-Division Photodetector 35, 36, 37 Current / Voltage Converter 38 Addition 39 Subtractor

Claims (5)

[Claims] 1. An optical recording medium capable of recording and reproducing information on an information track is irradiated with a minute light spot on one information track on which information should be reproduced, and information is recorded based on the reflected light. In an optical recording / reproducing apparatus for reproducing, a super-resolution spot irradiating means for irradiating the optical recording medium with a super-resolution spot as a light spot in a direction intersecting an information track, and reflected light from the one information track. The main light receiving portion for receiving the light and the optical recording medium
A photodetector having two sub-light-receiving portions that respectively receive reflected light from two portions adjacent to each other in the direction intersecting with one information track;
An output signal of the main light receiving unit and an output signal of the two sub light receiving units so as to remove the influence of the reflected light from two information tracks adjacent to the one information track included in the reflected light from one information track. An optical recording / reproducing apparatus, comprising: 2. The optical recording / reproducing apparatus according to claim 1,
When the output signal of the main light receiving portion is i and the output signals of the two sub light receiving portions are j and k, the arithmetic processing means obtains information signal = {αi− (β ₁ j + β ₂ k)} α, β ₁ , Β ₂ : An optical recording / reproducing apparatus characterized in that an information signal is detected by an arithmetic process in which a constant β ₁ = β ₂ . 3. The optical recording / reproducing apparatus according to claim 1 or 2, wherein when the optical recording medium is tilted in the radial direction, the arithmetic processing means outputs an information signal = {αi- (β ₁ j + β ₂ k)} α , β _1, β _2: an optical recording reproducing apparatus and detecting an information signal by constants β ₁ ≠ β ₂ becomes the arithmetic processing. 4. The optical recording / reproducing apparatus according to claim 1,
An optical recording / reproducing apparatus comprising: a tracking signal detecting means for obtaining a tracking signal by taking a difference between output signals of the two sub light receiving portions. 5. The optical recording / reproducing apparatus according to claim 1,
An optical recording / reproducing apparatus comprising a tilt signal detecting means for obtaining a tilt signal in a radial direction of the optical recording medium by taking a difference between output signals of the two sub light receiving portions.