JPH06318330A - Optical pick-up device - Google Patents

Abstract

PURPOSE:To realize an optical pick-up device using the astigmatism method at a low cost and in a small-sized and to improve the accuracy of detecting focussing error and tracking error. CONSTITUTION:A luminous flux passed through a detection line 7 is divided into two luminous fluxes La, Lb by a beam splitter 8, the luminous flux La, one of them, is extracted only at a center part by an aperture members 20. The center part luminous flux Laa passed through the aperture members 20 is made incident on a quadripartite photo-detector 10 in a state where the astigmatism is given to the Laa via a cylindrical lens 9. And, another luminous flux Lb is made incident on a bisected photodetector 11. Consequently, the patterns of the 1st-order diffracted light of focussing components are not made incident on the quadripartite photodetector 10 since the luminous flux Laa passed through the aperture members 20 includes only the patterns of the center part. Thus, a focussing servo control is excutede stably since track traversing noise is not superimposed on a focussing error signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device using an astigmatism method as a focusing error detecting method.

[0002]

2. Description of the Related Art In an optical recording / reproducing apparatus such as a magneto-optical disk device, a write-once optical disk device, a CD-ROM device, and an audio CD device, an optical disk used for recording / reproducing data on / from an optical recording medium. In the pickup device, various focusing error detection methods are used to detect a focus error of a laser beam used for recording / reproduction with respect to a recording medium.

Astigmatism is one of the focusing error detection methods. FIGS. 20A, 20B, and 20C show the main part of an example of an optical system of an optical pickup device that detects a focusing error using the astigmatism method.

In FIG. 1, the light beam output from the semiconductor laser device 1 is converted into a parallel light beam by the collimator lens 2, then passes through the split surface 3 a of the beam splitter 3, and the deflection prism 4 causes the light beam of the objective lens 5 to pass. It is deflected in the direction and is focused on the recording surface of the optical disc 6 by the objective lens 5.

On the other hand, the reflected light from the recording surface of the optical disk 6 is deflected to the light source side by the deflecting prism 5, is reflected by the split surface 3a of the beam splitter 3, and is detected by the detection lens 7.
And becomes focused light.

A light beam that has passed through the detection lens 7 (hereinafter referred to as a detected light beam) is split by a beam splitter 8 into two light beams La and Lb.
a is a four-division light receiving element 1 through the cylinder lens 9.
It is incident on 0. Further, the other light beam Lb split by the beam splitter 8 enters the two-split light receiving element 11.

Here, the pattern of the detected light flux is shown in FIG.
As shown in FIG. 3, the 0th-order diffracted light pattern PA0 and the 1st-order diffracted light patterns PA10 and PA11 due to the recording track grooves on the recording surface of the optical disk 6 appear, and the light receiving surface of the two-division light receiving element 11 has ), The division line 11a is formed so that the first-order diffracted light patterns PA10 and PA11 are received by the respective division surfaces.

The deflection prism 4 and the objective lens 5
Is mounted on a carriage (not shown) provided with a seek mechanism that reciprocates in the radial direction of the optical disc 7,
Further, the objective lens 5 is provided with an objective lens moving mechanism (not shown) for moving the objective lens 5 at least in the focusing direction and the tracking direction.

Then, a tracking error signal is detected based on the difference (Ma-Mb) between the light receiving signals from the two light receiving surfaces Ma and Mb of the two-divided light receiving element 11, and the two light receiving surfaces Ma of the two-divided light receiving element 11 are detected. , Mb sum of received light signals (M
The reproduced signal is detected based on a + Mb). Further, the four light receiving surfaces Mc, Md, Me, Mf of the four-division light receiving element 10
Predetermined calculation of received light signal from ((Mc + Me)-(Md
+ Mf)) to detect the focusing error signal.

Further, FIGS. 22A and 22B show the main part of another example of the optical system of the optical pickup device for detecting the focusing error by using the astigmatism method. In the drawings, the same parts as those in FIGS. 21A, 21B, and 21C and the corresponding parts are denoted by the same reference numerals.

In the figure, in this case, a cylinder lens 9 for imparting astigmatism to the detected light flux that has passed through the detection lens 7 is arranged so as to rotate by 45 ° on a plane orthogonal to the optical axis. .

Therefore, the pattern of the detected light flux which has passed through the cylinder lens 9 is as shown in FIGS.
As shown in (c) and (d), the four-division light receiving element 10 'is arranged at a position where the detected light beam can be received while the pattern is rotated by 90 ° and gradually rotated.

Therefore, in this case, the focusing error signal is detected based on the calculation ((Mc + Me)-(Md + Mf)) of the light receiving signals from the light receiving surfaces Mc, Md, Me, Mf of the four-division light receiving element 10 '. , Operation ((Mc + M
The tracking error signal is detected based on f)-(Md + Me)), and the reproduction signal is detected based on the operation (Mc + Md + Me + Mf).

[0014]

However, these conventional devices have the following disadvantages.

That is, in the former device and the latter device, since astigmatism is given to all parts of the detected light flux, the four-division light receiving element 10 also has the first-order diffracted light pattern PA10 which is a component of the tracking error signal. , PA11 is incident. Therefore, when the spot on the recording surface of the optical disc 6 deviates from the center of the recording track and the intensities of the primary diffracted light pattern PA10 and the primary diffracted light pattern PA11 differ, noise (track crossing noise) is likely to appear in the focusing error signal. It causes the inconvenience. Thus, if noise appears in the focusing error signal, it becomes difficult to stably perform the focusing servo control.

Further, in the former device, since the two-divided light receiving element 11 for forming the tracking error signal is provided, the number of parts is increased, the cost of the optical pickup device is increased, and the miniaturization is hindered. Becomes

On the other hand, in the latter device, since the focusing error signal, the tracking error signal and the reproduction signal are detected by using the four-division light receiving element 10, the number of optical parts constituting the optical pickup device is reduced. Therefore, the size of the optical pickup device can be reduced, and the cost of the optical system can be reduced.

However, in the latter device, at least five high-speed amplifiers are required in the circuit elements for signal calculation in order to properly form a reproduction signal with a high-speed signal change. In addition, there is a disadvantage that the cost of the signal processing system becomes high. Also, the objective lens 5
In the defocused state where the focal point is deviated, the pattern of the detection light beam incident on the four-division light receiving element 10 ′ deviates from an appropriate state, which may cause an inconvenience that an offset component is likely to appear in the tracking error signal.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical pickup device capable of detecting a focusing error signal with less noise and downsizing the device.

[0020]

According to the present invention, there is provided a light source, an objective lens for condensing a light beam from the light source onto an optical recording medium, and a beam splitter for separating reflected light from the optical recording medium from the light beam from the light source. In an optical pickup device provided with a detection optical system that guides the reflected light separated by the beam splitter as detection light to form various signals, the detection optical system is a central light flux at the center of the detection light. A light beam separating means for separating the other peripheral light beams, an astigmatism optical element for giving astigmatism to the central light beam, and a four-division light receiving for receiving the central light beam transmitted through the astigmatic optical element. An element is provided, and at least the focusing error signal of the objective lens is formed based on the light reception signal of the four-division light receiving element. Further, the astigmatism optical element may use a cylinder lens or a parallel plate.

Further, the light source, the objective lens for condensing the light beam from the light source on the optical recording medium, the beam splitter for separating the reflected light from the optical recording medium from the light beam of the light source, and the above-mentioned separated by the beam splitter. In an optical pickup device including a detection optical system that guides reflected light as detection light to form various signals, the detection optical system includes a detection lens that focuses the detection light and detection after passing through the detection lens. A beam splitter for splitting the light flux into two and one of the detected light fluxes split by this beam splitter are received, and the light-receiving surface thereof is split into two in the arrangement direction of the recording tracks formed on the optical recording medium. The two-divided light receiving element and the central luminous flux of the central portion of the other detected luminous flux split by the beam splitter are allowed to pass through and the other peripheral luminous fluxes are blocked. A light-blocking member, an astigmatism optical element that imparts astigmatism to the central light flux that has passed through the light-shielding member, and a four-division light-receiving element that receives the central light flux that has passed through the astigmatism optical element. At least a tracking error signal of the objective lens is formed based on the light receiving signal of the two-division light receiving element, and at least a focusing error signal of the objective lens is formed based on the light receiving signal of the four-division light receiving element. It is the one.

Further, the light source, the objective lens for condensing the light beam from the light source on the optical recording medium, the beam splitter for separating the reflected light from the optical recording medium from the light beam of the light source, and the above-mentioned separated by the beam splitter. In an optical pickup device including a detection optical system that guides reflected light as detection light to form various signals, the detection optical system includes a detection lens that focuses the detection light and detection after passing through the detection lens. The peripheral light flux excluding the central light flux of the central portion of the light flux is 2 in the direction of arrangement of the recording tracks formed on the optical recording medium.
A split light beam deflecting unit that splits and splits a split peripheral light beam obtained by dividing the light beam into two, and a first split peripheral light beam that is deflected by the split light beam deflecting unit.
Light receiving element, the second light receiving element for receiving the other divided peripheral light beam deflected by the divided light beam deflecting means, and the astigmatism that imparts astigmatism to the central light beam passing through the divided light beam deflecting means. An optical element and a four-division light receiving element that receives the central light flux transmitted through the astigmatism optical element are provided, and based on the light receiving signal of the first light receiving element and the light receiving signal of the second light receiving element, At least the tracking error signal of the objective lens is formed, and at least the focusing error signal of the objective lens is formed based on the light receiving signal of the four-division light receiving element.

Further, the light source, the objective lens for condensing the light beam from the light source on the optical recording medium, the beam splitter for separating the reflected light from the optical recording medium from the light beam of the light source, and the above-mentioned separated by the beam splitter. In an optical pickup device including a detection optical system that guides reflected light as detection light to form various signals, the detection optical system separates a central light beam of the detection light and a peripheral light beam other than the central light beam. In addition, at least the above-mentioned optical element for providing the central light flux with astigmatism and a four-division light receiving element for receiving the central light flux transmitted through the optical element are provided based on the light reception signal of the four-division light receiving element. The focusing error signal of the objective lens is formed. Further, the optical element may be a compound lens including a plane not perpendicular to the optical axis and a cylinder lens surface that passes the central light flux. Further, in the compound lens, a plane that is not perpendicular to the optical axis and the cylinder lens surface may be formed on the same surface.

Further, the light source, the objective lens for condensing the light beam from the light source on the optical recording medium, the beam splitter for separating the reflected light from the optical recording medium from the light beam of the light source, and the above-mentioned separated by the beam splitter. In an optical pickup device including a detection optical system that guides reflected light as detection light to form various signals, the detection optical system includes a cylinder lens surface on which a central light flux of the detection light is incident, and an optical axis. A compound lens having two planes which are not perpendicular to each other and separating peripheral light fluxes other than the central light flux by these two planes; a four-division light receiving element for receiving the central light flux transmitted through the compound lens; A first light receiving element for receiving one of the two peripheral light beams separated by the lens, and a second light receiving element for receiving the other of the two peripheral light beams separated by the compound lens. A focusing error signal of at least the objective lens is formed on the basis of the light receiving signal of the four-division light receiving element, and based on the light receiving signal of the first light receiving element and the light receiving signal of the second light receiving element, At least the tracking error signal of the objective lens can be formed. Further, in the compound lens, two planes that are not perpendicular to the optical axis and the cylinder lens surface may be formed on the same surface.

Further, the light source, the objective lens for condensing the light beam from the light source on the optical recording medium, the beam splitter for separating the reflected light from the optical recording medium from the light beam for the light source, and the above-mentioned separated by the beam splitter. In an optical pickup device equipped with a detection optical system that guides reflected light as detection light to form various signals, the detection optical system includes a cylinder lens surface on which a central light flux of the detection light is incident, and the cylinder lens. Has two planes which are formed on the same plane as the surface and which are not perpendicular to the optical axis, and a focusing lens surface which is formed on the surface opposite to the cylinder lens surface and the two planes. A compound lens that separates peripheral light beams other than partial light beams, a four-division light receiving element that receives the central light beam that has passed through this compound lens, and a composite lens that separates the peripheral light beams A first light receiving element for receiving one of the two peripheral light fluxes and a second light receiving element for receiving the other of the two peripheral light fluxes separated by the compound lens are provided, and based on the light reception signal of the four-division light receiving element. At least the focusing error signal of the objective lens is formed, and at least the tracking error signal of the objective lens is formed based on the received light signal of the first light receiving element and the light receiving signal of the second light receiving element. It is the one.

Further, the light source, the objective lens for condensing the light beam from the light source on the optical recording medium, the beam splitter for separating the reflected light from the optical recording medium from the light beam of the light source, and the above-mentioned separated by the beam splitter. In an optical pickup device equipped with a detection optical system that guides reflected light as detection light to form various signals, the detection optical system includes a cylinder lens surface on which a central light flux of the detection light is incident, and the cylinder lens. Has two planes which are formed on the same plane as the surface and which are not perpendicular to the optical axis, and a focusing lens surface which is formed on the surface opposite to the cylinder lens surface and the two planes. A compound lens that separates peripheral light beams other than partial light beams, a partial light blocking unit that blocks a part of the peripheral light beams of the detection light beam that enters the compound lens, and a light that passes through the compound lens And a first light receiving element for receiving one of the two peripheral light beams separated by the compound lens, and the other of the two peripheral light beams separated by the compound lens. A second light receiving element for receiving light, and at least a focusing error signal of the objective lens is formed on the basis of the light receiving signal of the four-division light receiving element, and the light receiving signal of the first light receiving element and the second light receiving element of the second light receiving element are received. Based on the received light signal of the light receiving element,
At least the tracking error signal of the objective lens is formed.

Further, the light source, the objective lens for condensing the light beam from the light source on the optical recording medium, the beam splitter for separating the reflected light from the optical recording medium from the light beam for the light source, and the above-mentioned separated by the beam splitter. In an optical pickup device equipped with a detection optical system that guides reflected light as detection light to form various signals, the detection optical system includes a cylinder lens surface on which a central light flux of the detection light is incident, and the cylinder lens. Two planes that are formed on the same plane as the surface and are not perpendicular to the optical axis, and a focusing lens surface that is formed on the cylinder lens surface and a surface opposite to the two planes.
The light-shielding surface that passes through a part of the peripheral light flux other than the central portion and has an inclination different from the two planes,
The peripheral light flux other than the central light flux is separated by two planes, and a part of the peripheral light flux is separated by the light shielding surface.
A composite lens that is deflected in a direction that does not intersect the peripheral light flux separated by two planes, a four-division light receiving element that receives the central light flux that has passed through the composite lens, and two peripheral light fluxes that are separated by the composite lens. A first light receiving element for receiving one of the light and a second light receiving element for receiving the other of the two peripheral light beams separated by the compound lens,
At least the focusing error signal of the objective lens is formed based on the light receiving signal of the divided light receiving element, and at least the objective lens is based on the light receiving signal of the first light receiving element and the light receiving signal of the second light receiving element. The tracking error signal of is formed.

[0028]

Therefore, basically, since astigmatism is applied only to the central light flux containing almost no tracking component, the tracking error does not appear in the focusing error signal and an appropriate focusing error signal is obtained. Can be formed. Further, since the light flux for tracking error detection and the light flux for focusing error detection are focused in substantially the same direction, a plurality of light receiving elements that receive these light fluxes can be arranged on the same surface. Since these light receiving elements can be incorporated into one device, the number of parts of the optical system can be reduced, the device cost can be reduced, and the device can be downsized.

[0029]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 shows a main part of an optical system of an optical pickup device according to an embodiment of the present invention. In the figure, the same parts as those in FIGS. 20A, 20B, and 20C and the corresponding parts are denoted by the same reference numerals.

In the figure, the reflected light from the recording surface of the optical disk 6 is deflected to the light source side by the deflecting prism 5, reflected by the dividing surface 3a of the beam splitter 3, enters the detecting lens 7, and is focused light. become.

The detection light beam that has passed through the detection lens 7 is split into two light beams La and Lb by the beam splitter 8, and one of the split light beams La is extracted by the aperture member 20 only in the central portion thereof. . The central light flux Laa that has passed through the aperture member 20 is incident on the four-division light receiving element 10 in a state where astigmatism is given through the cylinder lens 9. In addition, the beam splitter 8
The other light beam Lb split by is incident on the two-divided light receiving element 11.

Therefore, as shown in FIG. 2, the light beam Laa that has passed through the aperture member 20 has a central portion PA.
Since only the pattern of c is included, the four-division light receiving element 10 has the first-order diffracted light pattern PA10,
PA11 does not enter. As a result, in this embodiment, since the track crossing noise is not superimposed on the focusing error signal, the focusing servo control can be stably executed.

FIG. 3 shows a main part of an optical system of an optical pickup device according to another embodiment of the present invention. In the figure, the same parts as those in FIGS. 20A, 20B, and 20C and the corresponding parts are denoted by the same reference numerals.

In the figure, the reflected light from the recording surface of the optical disk 6 is deflected to the light source side by the deflecting prism 5, reflected by the dividing surface 3a of the beam splitter 3, enters the detecting lens 7, and is focused light. become.

Of the detected light flux that has passed through the detection lens 7,
The outer light flux including the first-order diffraction patterns PA10 and PA11 is separated and deflected by the triangular prisms 21 and 22, respectively, and separated by the triangular prisms 21 and 22.
ba and Lbb are incident on the light receiving elements 23 and 24, respectively. Further, the light flux Lac that has passed between the apex angles of the triangular prisms 21 and 22 is incident on the four-division light receiving element 10 in a state where astigmatism is given through the cylinder lens 9.

Therefore, as shown in FIG. 4, since the light flux passing between the vertical angles of the triangular prisms 21 and 22 includes only the pattern of the central portion PAd, the four-division light receiving element 10 has a tracking component. First-order diffracted light pattern PA
10, PA11 does not enter. As a result, in this embodiment, since the track crossing noise is not superimposed on the focusing error signal, the focusing servo control can be stably executed.

Further, in this case, the tracking error signal can be formed based on the difference between the light receiving signal of the light receiving element 23 and the light receiving signal of the light receiving element 24. Further, the reproduction signal can be obtained based on the sum of the light receiving signal of the light receiving signal 23 and the light receiving signal of the light receiving element 24.

FIG. 5 shows a main part of an optical system of an optical pickup device according to another embodiment of the present invention. In the figure, the same parts as those in FIGS. 20A, 20B, and 20C and the corresponding parts are denoted by the same reference numerals.

In the figure, the reflected light from the recording surface of the optical disk 6 is deflected to the light source side by the deflecting prism 5, reflected by the split surface 3a of the beam splitter 3, enters the detection lens 7, and is focused light. become.

The detection light flux that has passed through the detection lens 7 is incident on the compound lens 26. The compound lens 26 is shown in FIG.
As shown in (a) and (b), the central portion is formed on the cylinder lens portion 26a, the incident side is formed on the surface 26b orthogonal to the optical axis, and the emitting side is formed on the surface 26c not orthogonal to the optical axis. ing.

Therefore, of the detected light beams incident on the compound lens 26, the first-order diffraction patterns PA10 and PA11 are included.
The central light flux that does not include the
Light receiving element 27 in a state where the light passes through the
Is incident on the four-divided light receiving surface 27a.

The other detection light beams incident on the compound lens 26 are refracted at the emission surface 26c, and the detection lens 7
Receiving the focusing action by the
It is incident on 7b.

Therefore, in this embodiment, the compound lens 2 is used.
Since the detected light flux to which the astigmatism is given by 6 includes only the pattern PAc in the central portion (see FIG. 2), the first-order diffracted light patterns PA10 and PA11 of the tracking component do not enter the four-division light receiving element 27a. As a result, in this embodiment, since the track crossing noise is not superimposed on the focusing error signal, the focusing servo control can be stably executed.

Further, when the detection light beam is split into a light beam for detecting a focusing error and a light beam for detecting a tracking error by the compound lens 26, since these light beams travel in the same direction, one light receiving element is provided. 27
In addition, the four-division light-receiving surface 27 for detecting a focusing error
a and a two-divided light receiving surface 27 for tracking error detection
b can be formed, so that a focusing error and a tracking error can be formed by one light receiving element 27, and the number of components of the optical pickup device can be reduced. As a result, the cost of the optical pickup device can be reduced and the device can be downsized.

FIG. 7 shows a main part of an optical system of an optical pickup device according to still another embodiment of the present invention. It should be noted that, in FIG. 20, (a), (b),
The same reference numerals are given to the same portions as (c) and the corresponding portions.

In the figure, the reflected light from the recording surface of the optical disk 6 is deflected to the light source side by the deflecting prism 5, reflected by the split surface 3a of the beam splitter 3, enters the detection lens 7, and is focused light. become.

The detection light flux that has passed through the detection lens 7 is incident on the compound lens 28. The compound lens 28 is shown in FIG.
As shown in (a) and (b), the central portion is formed in the cylinder lens portion 28a, and the incident surface intersects two surfaces 28b and 28c which are not orthogonal to the optical axis and the intersection line thereof is the optical line. It is formed so as to match the axis, and its emission surface 28d is formed in a surface orthogonal to the optical axis.

Therefore, of the detected light beams incident on the compound lens 28, the first-order diffraction patterns PA10 and PA11 are detected.
The central light flux that does not include the
Light receiving element 29 with the astigmatism applied.
Is incident on the four-divided light receiving surface 29a.

Further, of the detected light flux entering the compound lens 28, the portion including the first-order diffraction pattern PA10 is refracted by the surface 28b and is incident on the light receiving surface 29b of the light receiving element 29. Further, in the detected light flux incident on the compound lens 28, the portion including the first-order diffraction pattern PA11 is the surface 2
The light is refracted by 8c and is incident on the light receiving surface 29c of the light receiving element 29.

Therefore, in this embodiment, the compound lens 2 is used.
The detected light flux to which the astigmatism is given by 8 includes only the pattern PAc in the central portion (see FIG. 2), so that the first-order diffracted light patterns PA10 and PA11 of the tracking component do not enter the four-division light receiving element 29a. As a result, in this embodiment, since the track crossing noise is not superimposed on the focusing error signal, the focusing servo control can be stably executed.

Further, when the detection light beam is split by the compound lens 28 into a light beam for detecting a focusing error and a light beam for detecting a tracking error, since these light beams travel in the same direction, one light receiving element is provided. 29
In addition, a four-division light receiving surface 29 for detecting a focusing error
a and the light receiving surfaces 29b and 2 for detecting the tracking error
9c can be formed, so that a focusing error and a tracking error can be formed by one light receiving element 29, and the number of components of the optical pickup device can be reduced. As a result, the cost of the optical pickup device can be reduced and the device can be downsized.

In this case, the tracking error signal can be formed based on the difference between the light receiving signal of the light receiving surface 29b and the light receiving signal of the light receiving surface 29c. Further, the reproduction signal can be obtained based on the sum of the light receiving signal of the light receiving surface 29b and the light receiving signal of the light receiving surface 29c.

FIG. 9 shows a main part of an optical system of an optical pickup device according to still another embodiment of the present invention. It should be noted that, in FIG. 20, (a), (b),
The same reference numerals are given to the same portions as (c) and the corresponding portions.

In the figure, the reflected light from the recording surface of the optical disk 6 is deflected to the light source side by the deflecting prism 5, reflected by the split surface 3a of the beam splitter 3, enters the detection lens 7, and is focused light. become.

The detection light flux that has passed through the detection lens 7 is incident on the compound lens 30. The compound lens 30 is shown in FIG.
As shown in (a) and (b), the center portion is formed into a belt-shaped cylinder lens portion 30a (convex toward the emitting surface side), and the incident surface 30b is formed into a plane orthogonal to the optical axis, Two surfaces 30c, 30 whose emission surfaces are not orthogonal to the optical axis
It is formed in a shape in which d is arranged so as to be continuous with the surface of the cylinder lens portion 30a.

Therefore, of the detected light beams incident on the compound lens 30, the first-order diffraction patterns PA10 and PA11 are included.
The light flux in the central portion that does not include
After passing through the optical axis and being given astigmatism, the light receiving element 31
Is incident on the four-divided light receiving surface 31a.

Further, of the detected light flux entering the compound lens 30, the portion including the first-order diffraction pattern PA10 is refracted by the surface 30c and is incident on the light receiving surface 31b of the light receiving element 31. Further, of the detected light flux incident on the compound lens 30, the portion including the first-order diffraction pattern PA11 is the surface 3
The light is refracted at 0d and is incident on the light receiving surface 31c of the light receiving element 31.

Therefore, in this embodiment, the compound lens 3 is used.
The detected light flux to which the astigmatism is given by 2 includes only the pattern PAd (see FIG. 4) in the central portion, so that the first-order diffracted light patterns PA10 and PA11 of the tracking component do not enter the four-division light receiving element 31a. As a result, in this embodiment, since the track crossing noise is not superimposed on the focusing error signal, the focusing servo control can be stably executed.

Further, when the detected light flux is split by the compound lens 30 into a light flux for detecting a focusing error and a light flux for detecting a tracking error, since these light fluxes are directed in the same direction, one light receiving element is provided. 31
In addition, the four-division light receiving surface 31 for detecting a focusing error
a and the light receiving surfaces 31b and 3 for detecting the tracking error
1c can be formed, so that a focusing error and a tracking error can be formed by one light receiving element 31, and the number of components of the optical pickup device can be reduced. As a result, the cost of the optical pickup device can be reduced and the device can be downsized.

Further, in this case, the tracking error signal can be formed based on the difference between the light receiving signal of the light receiving surface 31b and the light receiving signal of the light receiving surface 31c. Further, the reproduction signal can be obtained based on the sum of the light receiving signal of the light receiving surface 31b and the light receiving signal of the light receiving surface 31c.

FIG. 11 shows a main part of an optical system of an optical pickup device according to still another embodiment of the present invention. It should be noted that, in FIG. 20, (a), (b),
The same reference numerals are given to the same portions as (c) and the corresponding portions.

In the same figure, the reflected light from the recording surface of the optical disk 6 is deflected to the light source side by the deflecting prism 5, reflected by the split surface 3a of the beam splitter 3 and made incident on the detection lens 7 to converge the focused light. become.

The detection light flux that has passed through the detection lens 7 enters the compound lens 32. The compound lens 32 is shown in FIG.
As shown in (a) and (b), the central portion is formed into a belt-shaped cylinder lens portion 32a (concave to the emitting surface side), and the incident surface 32b is formed into a plane orthogonal to the optical axis, Two surfaces 32c, 32 whose emission surfaces are not orthogonal to the optical axis
It is formed in a shape in which d is arranged so as to be continuous with the surface of the cylinder lens portion 32a.

Therefore, of the detected light beams incident on the compound lens 32, the first-order diffraction patterns PA10 and PA11 are included.
The light flux in the central portion that does not include
After passing through the light receiving element 33 and being given astigmatism,
Is incident on the four-divided light receiving surface 33a.

Further, of the detected light flux incident on the compound lens 32, the portion including the primary diffraction pattern PA10 is refracted by the surface 32c and is incident on the light receiving surface 33b of the light receiving element 33. Further, of the detected light flux incident on the compound lens 32, the portion including the first-order diffraction pattern PA11 is the surface 3
The light is refracted at 2d and is incident on the light receiving surface 33c of the light receiving element 33.

Therefore, in this embodiment, the compound lens 3
The detected light flux to which the astigmatism is given by 2 includes only the pattern PAd (see FIG. 4) in the central portion, so that the first-order diffracted light patterns PA10 and PA11 of the tracking component do not enter the four-division light receiving element 33a. As a result, in this embodiment, since the track crossing noise is not superimposed on the focusing error signal, the focusing servo control can be stably executed.

Further, when the detection light beam is split by the compound lens 32 into a light beam for detecting a focusing error and a light beam for detecting a tracking error, since these light beams travel in the same direction, one light receiving element is provided. 33
In addition, the four-division light-receiving surface 33 for detecting focusing error
a and the light receiving surfaces 33b and 3 for detecting the tracking error
3c can be formed, so that the focusing error and the tracking error can be formed by one light receiving element 33, and the constituent elements of the optical pickup device can be reduced. As a result, the cost of the optical pickup device can be reduced and the device can be downsized.

In this case, the tracking error signal can be formed based on the difference between the light receiving signal of the light receiving surface 33b and the light receiving signal of the light receiving surface 33c. Further, the reproduction signal can be obtained based on the sum of the light receiving signal of the light receiving surface 33b and the light receiving signal of the light receiving surface 33c.

Now, as shown in FIG. 13A, a compound lens 34 having a shape in which the detection lens 7 and the compound lens 30 are integrated, and as shown in FIG. When the compound lens 35 having the shape in which the lenses 32 are integrated is formed, the number of constituent parts of the detection optical system can be reduced, and thus the optical pickup device can be further downsized.

Further, as shown in FIG. 7C, an optical element 37 having a shape in which the detection lens 7, the beam splitter 36 and the compound lens 32 are integrated can be constructed. In this case, the reproduction signal can be formed by the light beams separated by the beam splitter 36.

FIG. 14 shows a main part of an optical system of an optical pickup device according to another embodiment of the present invention. In addition,
In the figure, the same parts as those in FIGS. 20A, 20B, and 20C and the corresponding parts are designated by the same reference numerals.

In the figure, the reflected light from the recording surface of the optical disk 6 is deflected to the light source side by the deflection prism 5, reflected by the split surface 3 a of the beam splitter 3, and enters the compound lens 40.

The compound lens 40, as shown in FIG.
The incident surface 40a has a focusing effect (for example, a spherical surface).
In addition, the central portion of the emission surface (portion from point A to point B) is formed into a strip-shaped cylinder lens portion 40b (concave to the emission surface side), and the upper portion 40c of the emission surface (from point A to The point C portion) and the lower portion 40d (point B to point D) are formed so as not to be orthogonal to the optical axis and continuous to the surface of the cylinder lens portion 40a.

Therefore, the detection light beam incident on the compound lens 40 is focused on the incident surface 40a, and the first-order diffraction pattern PA10,
The central light flux not including the PA 11 passes through the cylinder lens portion 40b and is incident on the four-divided light receiving surface 41a of the light receiving element 41 with astigmatism applied.

Further, of the detected light flux entering the compound lens 40, the portion including the first-order diffraction pattern PA10 is refracted by the surface 40c and is incident on the light receiving surface 41b of the light receiving element 41. Further, of the detected light flux incident on the compound lens 40, the portion including the first-order diffraction pattern PA11 is the surface 4
The light is refracted at 0d and is incident on the light receiving surface 41c of the light receiving element 41.

Therefore, in this embodiment, the compound lens 4 is used.
Since the detected light flux to which astigmatism is given by 0 includes only the pattern PAd (see FIG. 4) in the central portion, the first-order diffracted light patterns PA10 and PA11 of the tracking component do not enter the four-division light receiving element 41a. As a result, in this embodiment, since the track crossing noise is not superimposed on the focusing error signal, the focusing servo control can be stably executed.

Further, when the detection light beam is split by the compound lens 40 into a light beam for detecting a focusing error and a light beam for detecting a tracking error, since these light beams travel in the same direction, one light receiving element is provided. 41
In addition, a four-division light receiving surface 41 for detecting a focusing error
a and light receiving surfaces 41b, 4 for detecting tracking error
1c can be formed, so that a focusing error and a tracking error can be formed by one light receiving element 41, and the number of components of the optical pickup device can be reduced. As a result, the cost of the optical pickup device can be reduced and the device can be downsized.

Further, in the present embodiment, since the compound lens 40 also has the function of the detection lens, the effect of reducing the cost of the optical pickup device and the effect of downsizing the device are more significant.

In this case, the tracking error signal can be formed based on the difference between the light receiving signal of the light receiving surface 41b and the light receiving signal of the light receiving surface 41c. Further, the reproduction signal can be obtained based on the sum of the light receiving signal of the light receiving surface 41b and the light receiving signal of the light receiving surface 41c. Alternatively,
It is also possible to form the reproduction signal based on the total sum of the light receiving signals of the four-division light receiving surface 41a.

FIG. 16 shows a main part of an optical system of an optical pickup device according to still another embodiment of the present invention.
20A, 20B, 20C,
The same parts as those in FIGS. 14 and 15 and the corresponding parts are designated by the same reference numerals.

In the figure, the compound lens 40 is provided with a lens holder 42. This lens holder 42
As shown in FIG. 17, is formed of a lens barrel portion 42a for holding the compound lens 40 and a ring-shaped light shielding portion 42b for shielding the outermost part of the detection light beam incident on the compound lens 40.

Therefore, the portion of the detected light flux incident on the compound lens 40 that includes the first-order diffraction patterns PA10 and PA11 forming the tracking component is limited, so that a so-called partial light receiving action of the tracking component is obtained, and as a result, It is possible to obtain a tracking error signal in which the influence of the optical axis shift is suppressed.

FIG. 18 shows a main part of an optical system of an optical pickup device according to still another embodiment of the present invention. It should be noted that, in FIG. 20, (a), (b),
The same reference numerals are given to the same portions as (c) and the corresponding portions.

In the figure, the reflected light from the recording surface of the optical disk 6 is deflected to the light source side by the deflection prism 5, reflected by the split surface 3 a of the beam splitter 3, and enters the compound lens 44.

The compound lens 44, as shown in FIG.
A central portion of the incident surface is formed as a surface 44a (for example, a spherical surface) having a focusing effect, and the other portion of the incident surface is formed as a surface 44b substantially orthogonal to the optical axis. Further, the central portion of the exit surface of the compound lens 44 (the portion from the point A to the point B) is formed into a strip-shaped cylinder lens portion 44c (concave to the exit surface side), and the upper portion 44d of the exit surface (the point from the point A to the point). C portion) and the lower portion 44e (portion from point B to point D) are not respectively orthogonal to the optical axis, and the cylinder lens portion 44c
Is formed so as to be continuous with the surface.

Therefore, of the detected light beams incident on the compound lens 44, the light beam passing through the surface 44a is the surface 4
Of the detected light fluxes focused by 4a, the central light flux not including the first-order diffraction patterns PA10 and PA11 passes through the cylinder lens portion 44c and is given astigmatism. The light is incident on the four-division light receiving surface 45a.

Of the detected light flux that has passed through the surface 44a of the compound lens 44 and is focused, the first-order diffraction pattern PA1
The portion including 0 is refracted at the surface 44d, and the light receiving element 45
Is incident on the light receiving surface 45b. Further, of the detected light flux that passes through the surface 44a of the compound lens 44 and is focused, the portion including the first-order diffraction pattern PA11 is refracted by the surface 44e and is incident on the light receiving surface 45c of the light receiving element 45.

On the other hand, of the detected light beams incident on the compound lens 44, the light beam passing through the surface 44b is refracted by the surface 44b and then by the surfaces 44d and 44e, and therefore, the light receiving surface of the light receiving element 45. It does not enter 44b and 44c.

Thus, in this embodiment, the surface 44b is
Since the detected light flux that has passed through is not used for tracking error detection, a so-called tracking component partial light receiving action is obtained, and as a result, a tracking error signal in which the influence of optical axis deviation is suppressed can be obtained. Also, FIG.
In the embodiments shown in FIGS. 6 and 17, depending on the mounting state of the lens holder 42, the light shielding mode of the detected light beam may not be preferable, but in the present embodiment, the surface 44b realizes the light shielding function. Such inconvenience does not occur.

By the way, although the present invention is applied to the optical pickup device of the optical disk device in the above-mentioned embodiments, the present invention can be applied to other optical pickup devices using the astigmatism method in the same manner. it can. Further, in the above-described embodiment, the reproduction signal is formed based on the change in the light amount of the reflected light from the optical disk. However, the optical pickup device of the magneto-optical disk device which detects the magneto-optical signal and forms the reproduction signal. Can be similarly applied.

[0092]

As described above, according to the present invention,
Basically, since the astigmatism is given only to the central light flux which does not include the tracking component, the tracking component does not appear in the focusing error signal, and an appropriate focusing error signal can be formed. Further, since the light flux for tracking error detection and the light flux for focusing error detection are focused in substantially the same direction, a plurality of light receiving elements that receive these light fluxes can be arranged on the same surface. Since these light receiving elements can be incorporated in one device, the number of parts of the optical system can be reduced, the device cost can be reduced, and the device can be downsized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main part of an optical system of an optical pickup device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a pattern of a detected light beam.

FIG. 3 is a schematic diagram showing a main part of an optical system of an optical pickup device according to another embodiment of the present invention.

FIG. 4 is a schematic diagram for explaining another example of a pattern of detected light flux.

FIG. 5 is a schematic diagram showing a main part of an optical system of an optical pickup device according to still another embodiment of the present invention.

6 is a schematic view showing details of the compound lens of FIG.

FIG. 7 is a schematic diagram showing a main part of an optical system of an optical pickup device according to still another embodiment of the present invention.

FIG. 8 is a schematic view showing details of the compound lens of FIG.

FIG. 9 is a schematic diagram showing a main part of an optical system of an optical pickup device according to still another embodiment of the present invention.

FIG. 10 is a schematic view showing details of the compound lens of FIG.

FIG. 11 is a schematic diagram showing a main part of an optical system of an optical pickup device according to still another embodiment of the present invention.

12 is a schematic view showing details of the compound lens of FIG.

FIG. 13 is a schematic view showing a composite component in which a plurality of optical components are integrated.

FIG. 14 is a schematic diagram showing a main part of an optical system of an optical pickup device according to another embodiment of the present invention.

15 is a schematic view showing details of the compound lens of FIG.

FIG. 16 is a schematic diagram showing a main part of an optical system of an optical pickup device according to still another embodiment of the present invention.

FIG. 17 is a schematic view showing details of the compound lens of FIG.

FIG. 18 is a schematic diagram showing a main part of an optical system of an optical pickup device according to still another embodiment of the present invention.

FIG. 19 is a schematic view showing details of the compound lens of FIG.

FIG. 20 is a schematic diagram showing a main part of a conventional example of an optical system of an optical pickup device that detects a focusing error using an astigmatism method.

FIG. 21 is a schematic diagram for explaining a pattern of a detected light beam.

FIG. 22 is a schematic diagram showing a main part of another example of a conventional optical system of an optical pickup device that detects a focusing error using an astigmatism method.

FIG. 23 is an explanatory diagram of the optical system of FIG. 22.

[Explanation of symbols]

 20 Aperture member 21,22 Triangular prism 26,28,30,32,40,44 Complex lens 42 Lens holder

Claims (13)

[Claims] 1. A light source, an objective lens for condensing a light beam from the light source onto an optical recording medium, a beam splitter for separating reflected light from the optical recording medium from the light beam for the light source, and the above-mentioned beam splitter separated by the beam splitter. In an optical pickup device equipped with a detection optical system that guides reflected light as detection light to form various signals, the detection optical system separates the central light flux at the central portion of the detection light and the peripheral light flux other than that. And a four-division light receiving element for receiving the central light flux transmitted through the astigmatism optical element. An optical pickup device, wherein at least a focusing error signal of the objective lens is formed based on a light receiving signal of an element. 2. The optical pickup device according to claim 1, wherein the astigmatism optical element is a cylinder lens. 3. The optical pickup device according to claim 1, wherein the astigmatism optical element is a parallel plate. 4. A light source, an objective lens for condensing a light beam from the light source onto an optical recording medium, a beam splitter for separating reflected light from the optical recording medium from the light beam for the light source, and the above-mentioned beam splitter separated by the beam splitter. In an optical pickup device equipped with a detection optical system that guides reflected light as detection light to form various signals, the detection optical system includes a detection lens that focuses the detection light and a detection after passing through the detection lens. A beam splitter that splits the light flux into two and one of the detected light fluxes split by this beam splitter are received, and the light-receiving surface is split into two in the arrangement direction of the recording tracks formed on the optical recording medium. A two-divided light receiving element and a central luminous flux of the central portion of the other detected luminous flux split by the beam splitter are allowed to pass through, and other peripheral luminous fluxes are blocked. A light-shielding member, an astigmatism optical element that applies astigmatism to the central light flux that has passed through the light-shielding member, and a four-division light-receiving element that receives the central light flux that has passed through the astigmatism optical element. At least a tracking error signal of the objective lens is formed based on the light receiving signal of the two-division light receiving element, and at least a focusing error signal of the objective lens is formed based on the light receiving signal of the four-division light receiving element. An optical pickup device characterized in that 5. A light source, an objective lens for condensing a light beam from the light source onto an optical recording medium, a beam splitter for separating reflected light from the optical recording medium from the light beam for the light source, and the above-mentioned beam splitter separated by the beam splitter. In an optical pickup device equipped with a detection optical system that introduces reflected light as detection light to form various signals, the detection optical system includes a detection lens that focuses the detection light and a detection after passing through the detection lens. Divided light beam deflecting means for dividing the peripheral light beam excluding the central light beam in the central part of the light beam into two in the arrangement direction of the recording tracks formed on the optical recording medium, and deflecting the divided peripheral light beam obtained by dividing the two. A first light receiving element for receiving one of the divided peripheral light beams deflected by the divided light beam deflecting means, and the other divided peripheral light beam deflected by the divided light beam deflecting means. A second light receiving element that receives light, an astigmatism optical element that applies astigmatism to the central light flux that has passed through the split light flux deflecting means, and the central light flux that has passed through the astigmatism optical element. A four-division light-receiving element is provided, and at least a tracking error signal of the objective lens is formed based on the light-reception signal of the first light-receiving element and the light-reception signal of the second light-receiving element, and the light-reception of the four-division light-receiving element An optical pickup device, wherein at least a focusing error signal of the objective lens is formed based on a signal. 6. A light source, an objective lens for condensing a light beam from the light source on an optical recording medium, a beam splitter for separating reflected light from the optical recording medium from a light beam for the light source, and the beam splitter for separating the light beam. In an optical pickup device equipped with a detection optical system that guides reflected light as detection light to form various signals, the detection optical system separates the central light flux at the central portion of the detection light and the peripheral light flux other than that. In addition, an optical element that gives astigmatism to the central light flux and a four-division light receiving element that receives the central light flux that has passed through the optical element are provided, and at least based on the light reception signal of the four-division light receiving element, An optical pickup device, characterized in that a focusing error signal of the objective lens is formed. 7. The optical pickup device according to claim 6, wherein the optical element comprises a compound lens having a plane not perpendicular to the optical axis and a cylinder lens surface that passes the central light flux. 8. The optical pickup device according to claim 7, wherein the compound lens is formed such that a plane that is not perpendicular to the optical axis and the cylinder lens surface are formed on the same surface. 9. A light source, an objective lens for condensing a light beam from the light source onto an optical recording medium, a beam splitter for separating reflected light from the optical recording medium from the light beam for the light source, and the above-mentioned beam splitter separated by the beam splitter. In an optical pickup device equipped with a detection optical system that introduces reflected light as detection light to form various signals, the detection optical system includes a cylinder lens surface on which a central light flux of the detection light is incident and an optical axis. A compound lens having two planes which are not perpendicular to each other and separates peripheral light fluxes other than the central light flux by these two planes, and receives the central light flux transmitted through the compound lens 4
A split light receiving element, a first light receiving element for receiving one of the two peripheral light beams separated by the compound lens, and a second light receiving element for receiving the other of the two peripheral light beams separated by the compound lens. A focusing error signal of at least the objective lens is formed based on a light receiving signal of the four-division light receiving element, and based on a light receiving signal of the first light receiving element and a light receiving signal of the second light receiving element, An optical pickup device characterized in that at least a tracking error signal of the objective lens is formed. 10. The optical pickup device according to claim 8, wherein in the compound lens, two planes that are not perpendicular to the optical axis and the cylinder lens surface are formed on the same surface. 11. A light source, an objective lens for condensing a light beam from the light source onto an optical recording medium, a beam splitter for separating reflected light from the optical recording medium from a light beam for the light source, and the above-mentioned beam splitter separated by the beam splitter. In an optical pickup device including a detection optical system that guides reflected light as detection light to form various signals, the detection optical system includes a cylinder lens surface on which a central light flux of the detection light is incident, and the cylinder lens. Has two planes which are formed on the same plane as the surface and which are not perpendicular to the optical axis, and a focusing lens surface which is formed on the surface opposite to the cylinder lens surface and the two planes. A compound lens that separates peripheral light beams other than partial light beams, and receives the central light beam that has passed through this compound lens 4
A split light receiving element, a first light receiving element for receiving one of the two peripheral light beams separated by the compound lens, and a second light receiving element for receiving the other of the two peripheral light beams separated by the compound lens. A focusing error signal of at least the objective lens is formed based on a light receiving signal of the four-division light receiving element, and based on a light receiving signal of the first light receiving element and a light receiving signal of the second light receiving element, An optical pickup device characterized in that at least a tracking error signal of the objective lens is formed. 12. A light source, an objective lens for condensing a light beam from the light source onto an optical recording medium, a beam splitter for separating reflected light from the optical recording medium from a light beam for the light source, and the above-mentioned beam splitter separated by the beam splitter. In an optical pickup device including a detection optical system that guides reflected light as detection light to form various signals, the detection optical system includes a cylinder lens surface on which a central light flux of the detection light is incident, and the cylinder lens. Has two planes which are formed on the same plane as the surface and which are not perpendicular to the optical axis, and a focusing lens surface which is formed on the surface opposite to the cylinder lens surface and the two planes. A compound lens that separates peripheral light beams other than the partial light beam, a partial light blocking unit that blocks a part of the peripheral light beam of the detection light beam that enters the compound lens, and a light beam that passes through the compound lens. 4 for receiving the center beam has
A split light receiving element, a first light receiving element for receiving one of the two peripheral light beams separated by the compound lens, and a second light receiving element for receiving the other of the two peripheral light beams separated by the compound lens. A focusing error signal of at least the objective lens is formed based on a light receiving signal of the four-division light receiving element, and based on a light receiving signal of the first light receiving element and a light receiving signal of the second light receiving element, An optical pickup device characterized in that at least a tracking error signal of the objective lens is formed. 13. A light source, an objective lens for condensing a light beam from the light source onto an optical recording medium, a beam splitter for separating the reflected light from the optical recording medium from the light beam for the light source, and the above-mentioned beam splitter separated by the beam splitter. In an optical pickup device including a detection optical system that guides reflected light as detection light to form various signals, the detection optical system includes a cylinder lens surface on which a central light flux of the detection light is incident, and the cylinder lens. Two planes that are not on the same plane as the optical axis and are not perpendicular to the optical axis, a focusing lens surface that is formed on the surface opposite to the cylinder lens surface and the two planes, and one of the peripheral light fluxes other than the central portion. Has a light-shielding surface that passes through a portion and has an inclination different from those of the two planes, separates peripheral light fluxes other than the central light flux from the two planes, and 4 for receiving more a part of the peripheral light and a compound lens for deflecting in a direction which does not intersect the peripheral light fluxes separated by the two planes, the central light beam passing through the composite lens
A split light receiving element, a first light receiving element for receiving one of the two peripheral light beams separated by the compound lens, and a second light receiving element for receiving the other of the two peripheral light beams separated by the compound lens. A focusing error signal of at least the objective lens is formed based on the light receiving signal of the four-division light receiving element, and based on the light receiving signal of the first light receiving element and the light receiving signal of the second light receiving element, An optical pickup device characterized in that at least a tracking error signal of the objective lens is formed.