JP2000011433A - Optical pickup and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup and an optical disk device using it which is made up compactly and at a low cost and also enabled to properly control an optical output of a light source. SOLUTION: This optical disk device comprises a light source 21, a light focusing means 23, a light separating means 31 located between the light source and the light separating means, and a photo-detector 24 having a light receiving part for receiving a light beam returning from a signal recording surface of an optical disk 11 separated by the light separating means 31, and the light separating means 31 has a such configuration that it is composed of a parallel flat plate with a 1st diffraction grating 32 arranged vertically to the optical axis on the surface 31a facing the optical disk, and that the 1st diffraction grating not only transmits the light from the light source but also diffracts the light returning from the optical disk toward the light receiving part, and further, the light separating means has a prism part 35 guiding other unnecessary diffracted light than the light diffracted by the 1st diffraction grating and going toward the light receiving part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mini disc (M
D) an optical pickup for recording and / or reproducing signals from an optical disk (hereinafter, referred to as an "optical disk") such as a magneto-optical disk (MO), a compact disk (CD), a CD minus ROM, and a phase change disk And an optical disc device provided with the optical pickup.

[0002]

2. Description of the Related Art Conventionally, an optical pickup for an optical disk is constructed, for example, as shown in FIG. In FIG. 7, the optical pickup 1 includes a light emitting unit 2, a hologram element 3, an objective lens 4, and a photodetector 5.

[0003] The light emitting section 2 has a semiconductor laser element 2c mounted on a second semiconductor substrate 2b provided on a first semiconductor substrate 2a, and a light beam inclined at, for example, 45 degrees from the surface of the semiconductor substrate 2a. Prism mirror 2d formed
It is composed of Here, the semiconductor laser element 2c
Is a light-emitting element utilizing recombination of semiconductors, which functions as a light source and emits a light beam in the x direction. The light beam emitted from the semiconductor laser element 2c in this way is reflected by the prism mirror 2d and travels in the z direction. Further, on the first semiconductor substrate 2a, behind the semiconductor laser element 2c,
A light detector 2e for monitoring the light output of the semiconductor laser element 2c is provided.

The hologram element 3 has two surfaces perpendicular to the optical axis of the light beam from the light emitting unit 2, and a first surface (a lower surface in FIG. 3) on the light emitting unit 2 side emits light. A diffraction grating 3a is formed on the optical axis of the light beam from the unit 2.
Further, the hologram element 3 has a hologram 3b formed on the optical disk D side on the second surface (the upper surface in FIG. 3) on the optical axis of the light beam from the light emitting section 2.

The hologram 3b transmits the light beam from the light emitting section 2 as it is, diffracts the return light from the optical disk D, and guides it to the photodetector 5. Here, as shown in FIG. 8, the hologram 3b includes two hologram portions 3b minus 1 and 3b minus 2 divided in a direction parallel to the track direction of the optical disc D, and these hologram portions 3b minus 1 , 3b minus 2 have different spatial frequencies from each other. Thereby, the return light from the optical disc 11 is diffracted by the hologram 3b in the x direction by a predetermined diffraction angle.

The objective lens 4 is a convex lens,
The light from the light emitting section 3 is focused on a desired recording track on the signal recording surface of the disk D. Furthermore, the objective lens 4
Is movably supported by a biaxial actuator 4a in a biaxial direction, that is, a focus direction and a tracking direction.

As shown in FIG. 9, the photodetector 5 is provided at a central light receiving portion 5a into which return light of the main beam split by the diffraction grating 3a is incident, and on both sides of the light receiving portion 5a. The light receiving unit 5a includes four light receiving units A, B, C, and D divided into four parts in the vertical and horizontal directions.

Then, each of the light receiving sections A, B, C, D,
The detection signals from E and F are amplified by a head amplifier in a processing circuit (not shown), and then become output signals Sa, Sb, Sc, Sd, Se, and Sf, which are further appropriately calculated by a calculation circuit. Thereby, a reproduction signal, a focus error signal, and a tracking error signal are calculated. The two-axis actuator 4a is driven and controlled based on the focus error signal and the tracking error signal, so that the focusing servo and the tracking servo of the objective lens 4 are performed.

In the optical pickup 1 having such a configuration, the light beam from the light emitting section 2 is
After being split into a main beam and two side beams by the diffraction grating 3a, the light passes through the hologram 3b and is irradiated on the signal recording surface of the optical disk D by the objective lens 4.
The return light beam reflected by the signal recording surface again enters the hologram 3b via the objective lens 4. Here, the return light is transmitted to each hologram section 3 of the hologram 3b.
The return light of the main beam is diffracted by b minus 1 and 3b minus 2, and enters the light receiving portion 5a of the photodetector 5, and the return light of the side beam enters the light receiving portions E and F of the photodetector 5. I do. Thereby, based on the detection signals from the light receiving sections A, B, C, D, E, and F of the photodetector 5, the reproduction signal RF is detected, and the focus error signal and the tracking error signal are detected. Focus servo and tracking servo of the optical pickup 20 are performed based on these signals. The light output of the semiconductor laser element 2c of the light emitting section 2 is controlled by a drive circuit (not shown) so that an appropriate light output is obtained based on the detection signal of the light detector 2e.

[0010]

However, the optical pickup 1 having such a configuration has the following problems. Generally, a diffraction grating can change the light amount ratio of the 0th-order diffracted light and the plus / minus 1st-order diffracted light in various ways depending on its cross-sectional shape. However, a diffraction grating easily mass-produced has a substantially rectangular cross-sectional shape. So,
The light quantity ratio between the plus first-order diffracted light and the minus first-order diffracted light is approximately 1: 1.

On the other hand, in a conventional optical pickup using a hologram element as a light separating means,
There is a type in which both the plus and minus first order diffracted lights are detected by the photodetector, and a type in which only one of the diffracted lights, for example, only the plus first order diffracted light, is detected by the photodetector.
In the latter type of optical pickup, the other diffracted light, for example, the minus first-order diffracted light does not contribute to signal detection and is unnecessary light, and its light amount is almost the same as the plus first-order diffracted light for signal detection. Therefore, the other diffracted light (hereinafter, referred to as
The optical pickup needs to be configured so that the unnecessary diffracted light does not affect the light source and the photodetector of the optical pickup. That is, in the optical path of the unnecessary diffracted light,
It is necessary to configure so as not to dispose an optical component, for example, a light source monitoring photodetector for monitoring the light output of the light source and controlling the light output to an appropriate light output. There is a problem that it is difficult to configure a composite device including a detector.

For example, the optical pickup 1 shown in FIG.
, The plus first-order diffracted light by the diffraction grating 3b is
The light enters the photodetector 5 and is detected by the photodetector 5. The minus first-order diffracted light exits from the lower surface of the hologram element 3 and then enters the light output monitoring photodetector 2 e of the light emitting unit 2. Resulting in. For this reason, the light detector 2e
Since the optical output of the semiconductor laser element 2c cannot be accurately detected, there is a problem that it is difficult to appropriately control the optical output of the semiconductor laser element 2c.

SUMMARY OF THE INVENTION In view of the above, the present invention provides an optical pickup and an optical disk apparatus using the same, which are small in size and low in cost and capable of appropriately controlling the light output of a light source. It is intended to provide.

[0014]

According to the present invention, there is provided a light source, a light converging means for converging a light beam emitted from the light source on a signal recording surface of a rotationally driven optical disk, Light separating means disposed between the light source and the light focusing means, and a photodetector having a light receiving portion for receiving a return light beam from the signal recording surface of the optical disc separated by the light separating means. The light separating means is composed of a parallel plate having a diffraction grating disposed perpendicularly to the optical axis on a surface on the optical disk side, and the diffraction grating separates light from a light source. While transmitting the light, the return light from the optical disc is diffracted toward the light receiving portion. Further, the light separating means is unnecessary for diffraction light diffracted by the diffraction grating other than the diffracted light toward the light receiving portion. Guide diffracted light to the outside Comprising a prism portion, the optical pickup is achieved.

According to the first aspect of the present invention, the light beam emitted from the light source is incident on the light separating means such as a hologram element and transmitted through the first diffraction grating such as a hologram, and then the light focusing means. Irradiates the signal recording surface of the optical disk via the. The return light beam from the signal recording surface of the optical disk again enters the first diffraction grating of the light separating means via the light focusing means. Then, the return light beam is diffracted by the first diffraction grating and enters the photodetector. Thus, a reproduction signal is generated based on the detection signal from the light receiving unit, and a focus error signal and a tracking error signal are detected.

In this case, of the return light diffracted by the first diffraction grating, for example, the plus first-order diffracted light is incident on the photodetector as described above, but other unnecessary diffracted light is incident on the optical path. Is incident on the prism portion provided on the surface, and is reflected on the inner surface or refracted on the emission surface, and is guided to the outside, for example, guided in a direction in which the light source and the photodetector are not provided. . As a result, the unnecessary diffracted light does not enter the photodetector for signal detection, so that accurate signal detection is performed and accurate servo in the biaxial directions of the objective lens is performed. Further, since the unnecessary diffracted light does not enter the light detector for monitoring the light output of the light source, the light output is accurately controlled. Further, since the light separating means is one optical element and includes the diffraction grating and the prism portion, the configuration of the optical system can be simplified and reduced in size.

In the case where the first diffraction grating is divided into a plurality of regions having different diffraction angles, the return light in each region has a different diffraction angle. The light is separated into diffracted light and enters the corresponding light receiving portions of the photodetectors.

When the prism portion is formed on the light source side surface of the light separating means, it is not necessary to provide a separate prism portion, and the number of parts is reduced. Therefore, the entire structure is reduced in size, and the assembling is facilitated.

According to a seventh aspect of the present invention, the light separating means has an optical path branching portion comprising a second diffraction grating and a plurality of surfaces having different normal vectors on the light source side surface. Preferably, a Foucault prism is provided, and the first diffraction grating formed on the surface on the optical disk side has a continuous area, and the second diffraction grating receives light from a light source. While splitting into a main beam and a side beam, the first diffraction grating transmits light from a light source, and diffracts return light from an optical disk toward the optical path branching portion.
Further, when the optical path branching section is configured to split the return light from the optical disk and guide the split light to the respective light receiving sections of the photodetector, the light beam emitted from the light source is transmitted to the light separating means. The beam is separated into three beams, that is, a main beam and a side beam, by the second diffraction grating. After being transmitted through the first diffraction grating, the beam is irradiated on the signal recording surface of the optical disk via the light focusing means.

The return light beam from the signal recording surface of the optical disk is diffracted by the first diffraction grating of the light separating means, and the return light of the main beam is incident on an optical path branching portion such as a Foucault prism. As a result, the return light of the main beam is branched by each surface of the optical path branching part, and enters the corresponding light receiving part of the photodetector. Thus, the focus error signal is detected by the so-called Foucault method based on the detection signal from the light receiving unit. Therefore, the spot diameter of the return light beam formed on the photodetector can be small, and the interval between the main beam and the side beam can be reduced.
Thereby, the allowable width of the angle formed by the line connecting the signal sequence recorded on the optical disk and the spots of the main beam and the side beams can be increased.

In this case, since the return light is branched by the optical path branching portion, the first diffraction grating only has to combine the entire return light and diffract it in the same direction. Therefore, the first diffraction grating does not need to be divided into regions, and is configured as one continuous region. Thus, the entire light separating means has a simple configuration.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
Since the embodiments described below are preferred specific examples of the present invention, various technically preferred limitations are added.
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows the configuration of an optical disk device incorporating the first embodiment of the optical pickup according to the present invention. In FIG. 1, an optical disk device 10 includes a spindle motor 12 as a driving means for rotatingly driving an optical disk 11, and a signal recording surface of the rotating optical disk 11 which is irradiated with a light beam to record a signal. An optical pickup 20 for reproducing a recording signal by a return light beam from the optical pickup 20 and a control unit 13 for controlling the optical pickup 20 are provided. Here, the control unit 13 includes an optical disk controller 14, a signal demodulator 15, an error correction circuit 16, an interface 17, a head access control unit 18, and a servo circuit 19.

The optical disk controller 14 controls the drive of the spindle motor 12 at a predetermined rotation speed. The signal demodulator 15 demodulates the recording signal from the optical pickup 20, corrects the error, and sends the signal to an external computer or the like via the interface 17. Thus, an external computer or the like can receive a signal recorded on the optical disk 11 as a reproduction signal.

The head access control section 18 moves the optical pickup 20 to a predetermined recording track on the optical disk 11, for example, by a track jump or the like. The servo circuit 19 moves the objective lens held by the biaxial actuator of the optical pickup 20 in the focusing direction and the tracking direction at the moved predetermined position.

FIG. 2 shows an optical pickup incorporated in the optical disk device 10. In FIG.
The optical pickup 20 includes a light emitting unit 21, a hologram element 22 as a light separating unit, an objective lens 23 as a light focusing unit, and a photodetector 24 for signal detection.

The light emitting section 21 is provided with a semiconductor laser element 21c mounted on a second semiconductor substrate 21b provided on a first semiconductor substrate 21a, and is inclined at an angle of, for example, 45 degrees from the surface of the semiconductor substrate 21a. And a light output monitoring photodetector 21e formed behind the semiconductor laser element 21c on the second semiconductor substrate 21b. Here, the semiconductor laser element 21c is a light emitting element utilizing recombination of a semiconductor, and functions as a light source to emit a light beam in the x direction. The light beam emitted from the semiconductor laser element 21c in this manner is
It will be reflected by 1d and travel in the z-direction.

The hologram element 22 has two surfaces perpendicular to the optical axis of the light beam from the light emitting section 21.
A hologram 25 as a first diffraction grating is formed on the optical disk 11 side surface 22a (the upper surface in FIG. 2) on the optical axis of the light beam from the light emitting unit 21. The hologram 25 transmits the light beam from the light emitting unit 21 as it is and diffracts the return light from the optical disk 11 to separate it into plus and minus first-order diffracted lights L1 and L2. Photodetector 2
4 Here, the hologram 25
Are two hologram sections 2 divided in a direction parallel to the track direction of the optical disc 11 as shown in FIG.
5a and 25b.
a and 25b have different spatial frequencies from each other. . Thereby, the return light from the optical disk 11 is diffracted by the hologram 25 in the x direction by a predetermined diffraction angle. Here, the predetermined diffraction angle is equal to the hologram 25.
The return light beam diffracted by the second diffraction grating 2
6 so as not to pass through.

In the hologram element 22, a second diffraction grating 26 is formed on a surface 22b (a lower surface in FIG. 2) of the hologram element 21 on the optical axis of the light beam from the light emission section 21. ing. The second diffraction grating 26 has, for example, a parallel groove extending in the x-axis direction, and converts the light beam from the light emitting unit 21 into a main beam composed of zero-order diffracted light and a side beam composed of plus / minus first-order diffracted light. Divided into

The objective lens 23 is a convex lens and focuses the light from the light emitting section 21 on a desired recording track on the signal recording surface of the disk D. Further, the objective lens 23 is supported by a biaxial actuator 23a so as to be movable in a biaxial direction, that is, a focus direction and a tracking direction.

The photodetector 24, as shown in FIG.
A central light receiving portion 24a into which return light of the main beam split by the second diffraction grating 26 is to be incident;
4a, light receiving portions E and F to which the return light of the side beam is to be incident provided on both sides of the light receiving portion 4a.
It has four light receiving units A, B, C, and D divided into four in the vertical and horizontal directions.

The light receiving sections A, B, C, D,
The detection signals from E and F are amplified by a head amplifier in a processing circuit (not shown), respectively, and then become output signals Sa, Sb, Sc, Sd, Se, and Sf.

(Equation 1) And the focus error signal FE is obtained by the so-called Foucault method,

(Equation 2) Or

(Equation 3) Or

(Equation 4) As a result, the tracking error signal TE becomes
By the beam method,

(Equation 5) Is calculated.

Further, the hologram element 22 has a prism portion 27 on the light path of the minus first-order diffracted light L2 by the hologram 25 on the surface 22b on the light emitting portion 21 side. In the case of FIG. 2, the prism portion 27 has a slope formed by cutting off the glass material of the main body of the hologram element 22 at an inclination such that the left side in FIG. 2 rises. In this case, the prism section 27 refracts the minus first-order diffracted light L2 and guides it to the outside, so that the hologram 25 is returned with respect to the return light of the main beam and the two side beams split by the second diffraction grating 26. Each of the minus first-order diffracted lights diffracted by the respective regions 25a and 25b of the light emitting unit 21 is, as indicated by a dot in FIG. 5, a light detector 21e for monitoring the light output of the light emitting unit 21 or a light detector for detecting the signal. 24.

The optical disk device 10 incorporating the optical pickup 20 according to the present embodiment is configured as described above, and operates as follows. First, the optical disk 11 is rotationally driven by the rotation of the spindle motor 12 of the optical disk device 10. Then, the optical pickup 20 moves the optical disc 1 along a guide (not shown).
1 in the radial direction, the objective lens 23
Is moved to the desired track position of the optical disk 11 to perform access.

In this state, in the optical pickup 20, the light beam from the light emitting section 21 is
After being split into three light beams by the second diffraction grating 26, the light beams are transmitted through the hologram 25 and focused on the signal recording surface of the optical disk 11 via the objective lens 23. The return light from the optical disk 11 again enters the hologram 25 of the hologram element 22 via the objective lens 23.
Here, the return light is diffracted by each of the hologram portions 25a and 25b of the hologram 25 and separated into plus and minus first-order diffracted lights. Then, the plus first-order diffracted light of the return light of the main beam is transmitted to the light receiving unit 2 of the photodetector 24.
4a, the plus first-order diffracted light of the return light of the side beam is incident on the light receiving units E and F of the photodetector 24.

Thus, each light receiving section A,
Detection signals Sa, Sb, Sc, from B, C, D, E, F
Based on Sd, Se, and Sf, the recording signal of the optical disk 11 is reproduced, and as described above, the tracking error signal TE is detected by the three-beam method, and the focus error signal is detected by the Foucault method. Based on the signal, the servo circuit 19 performs focus servo and tracking servo of the optical pickup 20 via the optical disk drive controller 14. The light output of the semiconductor laser element 21c of the light emitting section 21 is controlled by a drive circuit (not shown) so that an appropriate light output is obtained based on the detection signal of the light detector 21e.

Here, the minus first-order diffracted light L2 not diffracted by the hologram 25 and contributing to the signal detection passes through the hologram element 22 and enters the prism portion 27 formed on the lower surface 22b of the hologram element 22. Then, the minus first-order diffracted light L2 is refracted by the prism portion 27, and proceeds toward the vicinity of the semiconductor laser element 21c of the light emitting portion 21, as shown in FIG. As a result, the minus first-order diffracted light L2 is
Is not incident on the photodetector 21e or 24. Therefore, the light detector 21e for monitoring the light output can accurately detect the light output of the semiconductor laser element 21c, and the light output of the semiconductor laser element 21c is properly controlled. Further, the photodetector 24 for signal detection can accurately detect the return light from the optical disc 11, and the accurate reproduction signal R of the optical disc 11 can be obtained.
By obtaining F and accurately detecting the focus error signal FE and the tracking error signal TE, the servo of the objective lens 23 in the two axial directions is accurately performed.

In this case, since the prism section 27 is formed on the surface of the hologram element 22 on the light emitting section 21 side,
The number of parts is reduced, and the cost of parts and the cost of assembly are reduced. The hologram element 22 is arranged so that its diffraction grating 26 is orthogonal to the optical axis. The hologram element 22 can diffract incident light into a plus primary light and a minus primary light with substantially the same light quantity, respectively. In order to properly control the light output to obtain the light quantity, the optical design is easy and the manufacture is easy. Further, since the hologram element 22 as the light separating means is formed of an element different from the objective lens 23, even if the objective lens 23 is moved by servo, there is no change in the optical path or the like of the separated light. Light can always be correctly guided in a predetermined direction.

FIG. 6 shows a second embodiment of the optical pickup according to the present invention. 6, the optical pickup 30 has substantially the same configuration as the optical pickup 20 shown in FIG. 2, and is different only in the following points. That is, the optical pickup 30 includes the hologram element 2
A hologram element 31 is provided instead of 2.

The hologram element 31 has two surfaces perpendicular to the optical axis of the light beam from the light emitting section 21.
A hologram 32 as a first diffraction grating is formed on the optical disk 11 side surface 31a (the upper surface in FIG. 6) on the optical axis of the light beam from the light emitting unit 21. The hologram 32 transmits the light beam from the light emitting unit 21 as it is and diffracts the return light from the optical disc 11 to separate it into plus and minus first-order diffracted lights L1 and L2. Photodetector 2
4 Further, the hologram 32
Is composed of grooves substantially parallel to the y-axis as a single diffraction region, so that its spatial frequency is continuous. As a result, the return light from the optical disk 11 is diffracted by the hologram 32 in the x direction by the predetermined diffraction angle θ. Here, the diffraction angle θ is appropriately selected so that the return light beam diffracted by the hologram 32 does not pass through the second diffraction grating 33.

Further, the hologram element 31 is
On the side surface 31b (the lower surface in FIG. 6), a second diffraction grating 33 is formed on the optical axis of the light beam from the light emitting unit 21, and the light is branched to a region away from the optical axis. The Foucault prism 34 as a part is formed, and the hologram 3
A prism section 35 is formed in the optical path of the minus first-order diffracted light L2 due to the second section 2. In this case, the prism section 35
Reflects the minus first-order diffracted light L2 on the inner surface and guides the minus-first-order diffracted light L2 to the outside, so that the minus light diffracted by the hologram 32 with respect to the return light of the main beam and the two side beams split by the second diffraction grating 33. The first-order diffracted light does not enter the light detector 21e for monitoring the light output of the light emitting unit 21 or the light detector 24 for signal detection.

Here, the second diffraction grating 33 has a parallel groove extending in the x-axis direction, and converts the light beam from the light emitting section 21 into a main beam composed of the zero-order diffracted light and a plus or minus first-order light beam. It is split into side beams composed of folded light.

The Foucault prism 34 has two planes 34a and 34 having different normal vectors.
b, the boundary between these planes 34a, 34b extends parallel to the x-axis and the hologram 3
2 is disposed so as to pass through the center of the return light beam that is the plus first-order diffracted light diffracted by the second light. Note that the normal vector of one plane 34a is substantially the same angle as the diffraction angle θ by the hologram 32 with respect to the normal vector of the other plane 34b. Further, the normal vector of the other plane 34b is the hologram element 31
Has the same component as the normal vector of the surface 31b on the side of the light emitting section 21.

In the case of the photodetector 24, in the case shown in the figure, the central light receiving portion 24a into which the main beam split by the diffraction grating 25 is to enter, and side beams provided on both sides of the light receiving portion 24a are to enter. It consists of light receiving units E and F,
Further, the light receiving unit 24a has four light receiving units A, B, C, and D divided into four parts vertically and horizontally.

Each of the light receiving sections A, B, C, D,
The detection signals from E and F are amplified by a head amplifier in a processing circuit (not shown), respectively, and then become output signals Sa, Sb, Sc, Sd, Se, and Sf.

(Equation 6) And the focus error signal FE is obtained by the so-called Foucault method,

(Equation 7) Or

(Equation 8) Or

(Equation 9) As a result, the tracking error signal TE becomes
By the beam method,

(Equation 10) Is calculated.

According to the optical pickup 30 having such a configuration, the light beam from the light emitting section 21 is split into three light beams by the second diffraction grating 33 of the hologram element 31, and then transmitted through the hologram 32. Then, the light is focused on the signal recording surface of the optical disk 11 via the objective lens 23. The return light from the optical disk 11 again enters the hologram 32 of the hologram element 31 via the objective lens 23. The return light is diffracted by the hologram 32, and the return light of the main beam is
4 is incident. Thereby, the return light of the main beam is
The light is divided into semicircles by the surfaces 34a and 34b of the Foucault prism 34, and is incident on the respective light receiving portions of the photodetector 24. That is, the return light passing through the surface 34a is
And B, and the light passing through the surface 34b enters the light receiving units C and D. Further, the return light of the side beam is divided into substantially semicircular shapes by the respective surfaces 34a and 34b of the Foucault prism 34, and the respective light receiving portions E and E of the photodetector 24 are separated.
F will be incident. Thus, the recording signal of the optical disk 11 is reproduced from the detection signal of each light receiving portion of the photodetector 24, the tracking error signal TE is detected by the three-beam method, and the focus error signal is detected by the Foucault method, as described above. FE is detected, and focus servo and tracking servo of the optical pickup 30 are performed based on these signals.

Here, the minus first-order diffracted light L2, which does not contribute to the signal detection diffracted by the hologram 32, passes through the hologram element 31 and enters the prism portion 35 formed on the lower surface 31b of the hologram element 31. Then, the minus first-order diffracted light L2 travels outward as shown in FIG. 6 by being internally reflected by the prism portion 35. Thus, the minus first-order diffracted light L2 does not enter the light detector 21e or 24 of the light emitting unit 21. Therefore, the light detector 21e for monitoring the light output can accurately detect the light output of the semiconductor laser element 21c, and
The control of the light output of c is performed appropriately. Also,
The photodetector 24 for signal detection can accurately detect the return light from the optical disc 11, and
As one accurate reproduction signal RF is obtained, and the focus error signal FE and the tracking error signal TE are accurately detected, the two-axis servo of the objective lens 23 is accurately performed.

The hologram 32, which is the first diffraction grating on the optical disk side, is formed as a single continuous area, so that it can be easily formed by injection molding or glass press molding of plastic, and the like.
Since the molding die is easily manufactured, it can be manufactured at low cost.

In the above embodiment, the photodetector 2
4 is formed integrally with the light emitting unit 21 by being formed on the semiconductor substrate 21a of the light emitting unit 21 as shown in FIG. 2 or FIG. 7, but is not limited thereto. It may be configured on the body.

In the above embodiment, the hologram elements 22 and 31 each having the hologram 27 or 32 are used. However, the present invention is not limited to this, and the diffraction grating for separating the returning light on the surface of the optical disk 11 is used. Obviously, it is only necessary to provide a light separating means having the following.

Further, in the above embodiment, the hologram elements 22 and 31 are composed of the light emitting section 21 and the photodetector 2.
4, but may be configured to be integrally supported by the semiconductor substrate 21a of the light emitting unit 21. In this case, the light emitting section 21, the photodetector 24, and the hologram elements 22, 31 (or light separating means) are integrally configured as one unit.

In the above embodiment, the prism section 2
7, 35 are holograms 25, 3 which are first diffraction gratings.
The negative first-order diffracted light due to 2 is guided to the outside by refraction or reflection. However, the present invention is not limited to this, and unnecessary diffracted light that does not contribute to other signal detection may be guided to the outside by refraction or reflection. Is clear.

In the optical disk device 10 and the optical pickups 20 and 30 according to the above-described embodiment, a configuration of a non-polarized optical pickup for reproducing an optical disk such as a compact disk (CD) or a CD minus ROM is shown. Without being limited to this, the magneto-optical disk (M
Obviously, the present invention can be applied to a polarization optical pickup and an optical disk device for O) and the like.

[0054]

As described above, according to the present invention, there is provided an optical pickup which is small in size and low in cost and capable of appropriately controlling the light output of a light source, and an optical disk apparatus using the same. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of an optical disk device incorporating an optical pickup according to the present invention.

FIG. 2 is a schematic side view showing a configuration of a first embodiment of an optical pickup in the optical disk device of FIG. 1;

FIG. 3 is a partially cutaway plan view showing a surface of a hologram element in the optical pickup of FIG. 2;

FIG. 4 is a schematic plan view illustrating a configuration example of a photodetector in the optical pickup in FIG. 2;

FIG. 5 is a schematic plan view showing a spot of the light emitting unit in the optical pickup of FIG. 2 due to unnecessary diffracted light.

FIG. 6 is a schematic side view showing the configuration of an optical pickup according to a second embodiment of the present invention.

FIG. 7 is a schematic side view showing a configuration of an example of a conventional optical pickup.

FIG. 8 is a partially broken plan view showing a surface of a hologram element in the optical pickup of FIG. 7;

FIG. 9 is a schematic plan view illustrating a configuration example of a photodetector in the optical pickup in FIG. 7;

[Brief description of reference numerals]

10 optical disk device, 11 optical disk, 1
2 ... Spindle motor, 13 ... Control unit, 14.
..Optical disk drive controller, 15 ... signal demodulator, 16 ... error correction circuit, 17 ... interface, 18 ... head access control unit, 20 ...
・ Optical pickup, 21 ・ ・ ・ Light emitting unit (light source), 2
2, 31 ... hologram element (light separating means), 23
..Objective lenses (light focusing means), 24 ... photodetectors,
25, 32... Hologram (first diffraction grating), 2
6, 33... Diffraction grating (second diffraction grating), 27.
-Prism part, 34 ... Foucault prism (optical path branching part), 34a, 34b ... Surface, 27 ... Hologram (second diffraction grating).

Claims (9)

[Claims] 1. A light source, a light converging means for converging a light beam emitted from the light source on a signal recording surface of a rotationally driven optical disk, and a light disposed between the light source and the light converging means. Separating means, and a photodetector having a light receiving portion for receiving a return light beam from the signal recording surface of the optical disc separated by the light separating means, wherein the light separating means is provided on a surface on the optical disc side. A parallel plate having a diffraction grating disposed perpendicular to the optical axis. The diffraction grating transmits light from the light source and directs return light from the optical disk to the light receiving unit. Further, the light separating means further includes a prism unit for guiding unnecessary diffracted light other than the diffracted light toward the light receiving unit to the outside among the diffracted light diffracted by the diffraction grating. Optical Backup. 2. The optical pickup according to claim 1, wherein said light separating means is a hologram element. 3. The diffraction grating according to claim 2, wherein the diffraction grating is divided into a plurality of regions having different diffraction angles.
An optical pickup according to item 1. 4. The optical pickup according to claim 1, wherein the prism portion is formed on a light source side surface of the light separating means. 5. The optical pickup according to claim 1, wherein the prism portion reflects the unnecessary diffracted light. 6. The optical pickup according to claim 1, wherein the prism portion refracts the unnecessary diffracted light. 7. The device according to claim 1, wherein the light separating means has a light source side surface.
A second diffraction grating provided separately from the first diffraction grating,
An optical path branching portion composed of a plurality of surfaces having different normal vectors, and a first diffraction grating formed on the optical disk side surface has a continuous one area, The second diffraction grating divides the light from the light source into a main beam and a side beam, and the first diffraction grating transmits the light from the light source and returns the light from the optical disk to the optical path branching unit. The optical path branching portion is further configured to split the return light from the optical disc and to guide the split light to each light receiving portion of the photodetector. Item 3. The optical pickup according to item 2. 8. The optical pickup according to claim 7, wherein the optical path branching unit is a Foucault prism. 9. A driving means for driving the optical disc to rotate, and a light irradiating the rotating optical disc via a light focusing means, and detecting a return light from the signal recording surface from the optical disc through the light focusing means. An optical pickup, a biaxial actuator that supports the light focusing means so as to be movable in two axial directions, a signal processing circuit that generates a reproduction signal based on a detection signal from the optical pickup, and a detection signal from the optical pickup. A servo circuit for moving the light focusing means in two axial directions, wherein the optical pickup focuses a light source and a light beam emitted from the light source on a signal recording surface of a rotationally driven optical disk. A light focusing means; a light separating means provided between the light source and the light focusing means; and a signal recording surface of the optical disc separated by the light separating means. And a photodetector having a light receiving section for receiving the return light beam of the optical disc. The light separating means includes a first diffraction grating disposed perpendicularly to the optical axis on a surface on the optical disk side. The first diffraction grating transmits light from a light source and diffracts return light from an optical disk toward the light receiving unit. An optical disc apparatus, wherein the means includes a prism unit for guiding unnecessary diffracted light other than the diffracted light toward the light receiving unit out of the diffracted light diffracted by the first diffraction grating.