JPH04318337A - Optical pickup head device - Google Patents

Abstract

PURPOSE:To stably detect the signal by constituting the device so that a reflection type hologram element receives a beam which is reflected and diffracted by an optical recording medium, and thereafter, transmits through an objective lens and becomes parallel beams and generates a diffracted light led to a photodetector. CONSTITUTION:In a hologram element 61, a beam which is reflected and diffracted by an optical storage medium 4, and thereafter, transmits through am objective lens 12 and becomes parallel beam is made incident and diffracted light 81a, 81b led to a photodetector 71 is generated. Therefore, the diffraction efficiency of the reflection type hologram element 61 is kept constant in any area, and an offset is not generated in a focus error signal and a tracking error signal. In such a way, a stable servo-operation of the optical pickup head device can be realized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup head device capable of recording, reproducing, or erasing optical information stored on an optical medium or magneto-optical medium such as an optical disk or an optical card.

0002

[Prior Art] Optical memory technology that uses optical disks with pit-like patterns as high-density, large-capacity storage media includes digital audio disks, video disks,
It has been put into practical use with expanded uses, including document file disks and even data files. The mechanism by which information is successfully recorded and reproduced on an optical disk through a light beam focused on the micron order with high reliability is entirely dependent on the optical system.

FIG. 8 shows a conventional example of an optical pickup head device disclosed in Japanese Unexamined Patent Publication No. 191328/1983. In FIG. 8, a diverging beam 8 emitted from a laser light source 7 is reflected by a diffraction element 3, and then collimated by a collimator lens 17, and then passed through an infinity imaging objective lens 16 to an optical storage medium 1. The light is focused on the recording surface 2 of. Next, the beam 8 reflected by the recording surface 2 passes through the objective lens 16 and then the collimator lens 17 again, and enters the diffraction element 3 while being condensed. This diffraction element 3 has two diffraction grating regions 3a each having a grating direction set in a different direction.
. Photodetectors 13a, 1 corresponding to 8a, 8b
The light is received at 3b. The photodetectors 13a, 13b each have photodetectors 13e, 13f and 13g, 13h, and the focus error signal (hereinafter referred to as FE signal) is generated by, for example, the output from the photodetector 13e and the output from the photodetector 13f, or the light By differential calculation of the output from the detection section 13g and the output from the detection section 13h, on the other hand, the tracking error signal (hereinafter referred to as TE signal) is calculated by the sum of the output from the photodetection sections 13e and 13f and the sum of the output from the photodetection sections 13g and 13h. It is obtained by performing differential calculation of the sum of outputs.

0004

[Problems to be Solved by the Invention] However, in general, the diffraction efficiency of a diffraction element changes depending on the angle of incidence of the beam incident on the diffraction element. When it is incident,
The intensity of the beam diffracted by the diffraction element becomes partially different depending on the angle of incidence of the beam incident on the diffraction element. Therefore, the beam incident on the photodetector is also a beam with partially different intensities, and when the diffraction element is arranged as shown in this conventional example, the first-order diffracted light 8b diffracted by the diffraction grating region 3b is more diffracted. It is stronger than the first-order diffracted light 8a diffracted by the grating region 3a, and as a result, the photodetector 13a
There is a problem in that when performing differential calculations on the outputs from the FE and TE signals to obtain a focus error signal and a tracking error signal, an offset is generated in the FE signal and the TE signal, making it impossible to realize stable servo operation in the optical pickup head device. Ta.

FIG. 7 shows an example of the relationship between the incident angle θ of a beam incident on a blazed reflection type diffraction element and the diffraction efficiency η. Here, η0 is the diffraction efficiency of the 0th order diffracted light, and η+1 is +
The diffraction efficiency of the first-order diffracted light, η+2 represents the diffraction efficiency of the +second-order diffracted light, and η-1 represents the diffraction efficiency of the −1st-order diffracted light. Generally, the numerical aperture (hereinafter referred to as NA) of a lens that receives a beam from a light source is about 0.07 to 0.15. For example, if NA = 0.1125, the incident angle θ
The change in is ±6.5 degrees. A sectional view of the conventional optical pickup head device shown in FIG. 8 is shown in FIG. If the optical axis of the beam emitted from the light source is incident on the reflective diffraction element at 45 degrees, the incident angle θ is 3 as shown in FIG.
It is distributed from 8.5 to 51.5 degrees, and η0 at this time is about 3
From 0 to 48%, η+1 similarly varies from about 45 to 29% depending on the angle of incidence of the beam. In the conventional example shown in FIG.
The incident angle of the beam 8L incident on the diffraction grating region 3
Since the angle of incidence of the beam 8U incident on a is smaller than that of the beam 8U, the diffraction efficiency of the 0th-order diffracted light in the diffraction grating region 3a is higher than that of the 0th-order diffracted light in the diffraction grating region 3b. The diffraction efficiency of the first-order diffracted light in the diffraction grating region 3a is lower than the diffraction efficiency of the first-order diffracted light in the diffraction grating region 3b. Therefore, on the outgoing path in which the beam 8 emitted from the light source 7 enters the diffraction element 3, the 0th-order diffracted light reflected by the diffraction grating region 3a becomes stronger than the 0th-order diffracted light reflected by the diffraction grating region 3b. The beam 8 is given an intensity distribution that depends on the angle of incidence of the beam incident on the beam 3. The beam 8 reflected by the diffraction element 3 is focused on the optical storage medium 1 by lenses 17 and 16, and then reflected by the optical storage medium 1 and enters the diffraction element 3 again. In the return path where the beam 8 reflected by the optical storage medium 1 is incident on the diffraction element 3, the beam 8 is reflected by the diffraction grating area 3 in the outgoing path.
The beam reflected at b is incident on the diffraction grating area 3a, and the beam reflected on the diffraction grating area 3a on the outward path is inverted and incident on the diffraction grating area 3b, so that the beam incident on the diffraction grating area 3b on the return path is is stronger than the beam incident on the diffraction grating region 3a. At this time, since the diffraction efficiency of the first-order diffracted light in the diffraction grating region 3b is higher than the diffraction efficiency of the first-order diffracted light in the diffraction grating region 3a, the first-order diffracted light 8a is guided to the photodetectors 13a and 13b.
. It can be seen that this becomes considerably stronger than the next diffracted light 8a. For example, if the lens NA is 0.1125,
Photodetectors 13a, 1 are detected from both ends of the diffraction grating regions 3a, 3b.
Comparing the intensities of the respective first-order diffracted lights guided to the diffraction grating region 3b, the intensity of the first-order diffracted light from the diffraction grating region 3a is η0(
θ=38.5 degrees)×η+1(θ=51.5 degrees)=30%
×29%=8.7%, the intensity of the first-order diffracted light from the diffraction grating region 3b is η0 (θ=51.5 degrees)×η+1 (θ=38
．． 5 degrees) = 48% x 45% = 21.6%, which is actually about 2.5
The difference is twice that.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a semiconductor laser light source that emits a coherent beam or a quasi-monochromatic beam, and a collimating lens that converts the diverging beam from the light source into a parallel beam. and,
a reflective hologram element that reflects and diffracts the parallel beam to bend the optical path; an objective lens that receives the parallel beam reflected by the hologram element and converges it onto a minute spot on an optical storage medium; , an optical pickup head device is configured using a photodetector having a plurality of photodetectors that receive the diffracted beam and output a photocurrent, and further, the reflection type hologram element reflects the beam on the optical storage medium,
After being diffracted, the beam passes through the objective lens and becomes a parallel beam, thereby generating diffracted light that is guided to the photodetector.

[0007]

[Operation] By using the above means, since the beam incident on the reflection hologram element (diffraction element) is a parallel beam, the incident angle is equal to the angle between the reflection hologram element and the optical axis in any area of the beam. Therefore, the diffraction efficiency of the reflective hologram element is constant in any region of the hologram element, and as a result, the focus error signal obtained by calculating the output from the photodetector that receives the diffracted light from the hologram element. Also, no offset occurs in the tracking error signal.

[0008]

[Example] Specific examples will be described in detail below. FIG. 1 shows a schematic configuration of an optical pickup head device according to an embodiment of the present invention. The diverging beam 81 emitted from the light source 6 is converted into parallel light by the collimating lens 11 and enters the reflective hologram element 61, and is then reflected and diffracted by the hologram element 61, resulting in 0th order diffracted light 810 from the hologram element 61. is focused onto the optical storage medium 4 by the objective lens 12. In the optical storage medium 4, 41 is a substrate, 42
is a protective film. The 0th order diffracted light 810 focused on the optical storage medium 4 by the objective lens 12 is reflected and diffracted by the optical storage medium 4, passes through the objective lens 12 again, and then becomes parallel light and enters the hologram element 61. A pattern for generating first-order diffracted lights 81a and 81b to be received by the photodetector 71 is recorded on the hologram element 61. Details of the hologram element 61 will be described later. The first-order diffracted lights 81a and 81b generated from the hologram element 61 pass through the collimating lens 11 and then enter the photodetector 71, where they are converted into electrical signals according to the amount of light. The photodetector 71 and the light source 6 are mounted on the same block 100 in order to downsize the optical pickup head device, and the block 100, the collimating lens 11, and the hologram element 61 are fixedly arranged on the housing 101. . The objective lens is provided with a focus following actuator consisting of a coil 91 and a magnet 92, and a track following actuator consisting of a coil 93 and a magnet 94. , it is possible to always follow the zero-order diffracted light 810 so that it is focused on the pit of the optical storage medium 4. In the present invention, the reflective hologram element 61 is connected to the optical path between the collimating lens 11 and the objective lens 12, that is, the beam 81 emitted from the light source 6 and the 0th-order diffracted light 810 reflected and diffracted by the optical storage medium 4 are parallel beams. By placing the beam in the optical path where The diffraction efficiency of the element 61 is constant in any region of the hologram element, and the FE
No offset occurs in the signal and the TE signal, making it possible to realize stable servo operation of the optical pickup head device.

FIG. 2(a) shows the configuration of the reflective hologram element 61 constituting the optical pickup head device shown in FIG.
FIG. 2B shows the first-order diffracted lights 81a and 81b generated from the hologram element 61 on the photodetector 71, respectively. The hologram element 61 has two regions 61a and 61b with grating directions set in different directions.
At this time, the area dividing line of the hologram element 61 is formed on a plane including the optical axis 81c of the beam 81 emitted from the light source 6 and incident on the hologram element 61, and the optical axis 81d of the beam reflected by the hologram element 61. 61c is included. Furthermore, the dividing line 6 of the hologram element 61
1c and the mapping of the groove or pit row formed in the optical storage medium 4 on the hologram element 61 are arranged so as to be parallel to each other. That is, the Y direction of the hologram element 61 is the direction of the groove or pit row of the optical storage medium 4, and the X direction of the hologram element 61 is the radial direction of the optical storage medium 4. The hologram element region 61a of the hologram element 61 generates a first-order diffracted light 81a, and the hologram element region 61b generates a first-order diffracted light 81b.
The second-order diffracted lights 81a and 81b are received by the photodetector 71. The photodetector 71 includes photodetection sections 711, 712, 713, 7
It consists of 14. The patterns of the hologram element regions 61a and 61b of the hologram element 61 are formed when the beam 81 emitted from the light source 6 is focused on the optical storage medium 4.
The first-order diffracted lights 81a and 81b from the hologram element 61 are also designed to be focused on the photodetector 71, respectively. For example, the beam 81 emitted from the light source 6 and the photodetector 7
This can be achieved by calculating and recording the interference fringes generated on the hologram element 61 using the convergence points of the first-order diffracted lights 81a and 81b on the hologram element 61 as light sources of the divergent lights. this is,
Since this is a well-known technique called the CGH method, further detailed explanation will be omitted. Of course, a two-beam interferometry method in which interference fringes are recorded by actually configuring an optical system is also applicable. The hologram element 61 is manufactured by forming a pattern on a glass substrate by etching, and then applying Au or Al to the surface of the hologram element.
It is also possible to form a reflective film such as, to form a pattern on a semiconductor or metal substrate, and all other general methods for manufacturing hologram elements can be applied. A detailed explanation will be omitted. Hologram element 6
Patterns 411 and 412 on 1 are far-field patterns, which show the state of the first-order diffracted light of the beam 810 that is diffracted by the grooves or pit rows recorded on the optical storage medium 4. Since the grooves or pit rows No. 4 are parallel to the Y direction, the pattern arrangement is as shown in FIG. 2(a). Note that in order to improve the light utilization efficiency and suppress noise caused by unnecessary diffracted light, the shape of the pattern recorded in the hologram element regions 61a and 61b of the hologram element 61 may be blazed.

Next, the signal detection method in this embodiment will be explained. FIG. 3 shows photodetecting sections 711, 712, 7 of the photodetector 71 in the optical pickup head device shown in FIG.
13 and 714, the state of the first-order diffracted lights 81a and 81b generated by the hologram element 61 is schematically and generally shown. 3(b) shows a case where the beam 81 emitted from the light source 6 is in a focused state on the optical storage medium 4, and FIGS. 3(a) and (c) show a state in which the beam 81 emitted from the light source 6 is defocused in opposite directions. Indicate the case. The FE signal is detected by the photodetector 712
By performing a differential operation on the sum of the outputs from the photodetectors 711 and 713 and the sum of the outputs from the photodetectors 711 and 714, the TE signal is obtained by calculating the sum of the outputs from the photodetectors 711 and 712 and the sum of the outputs from the photodetectors 713 and 714. By differentially calculating the sum of outputs, RF
The signals are obtained by summing the outputs from the photodetectors 711, 712, 713, and 714, respectively. The FE signal detection method is a double knife edge method, and the TE signal detection method is a push-pull method, both of which are well-known calculation methods. Further, the FE signal is transmitted to the photodetector 711
It can also be obtained by differentially calculating the outputs from and 712 or 713 and 714. This detection method is the so-called Foucault method, and this detection method is also well known. First-order diffracted light 81a, 8 from the hologram element 61
The mapping of the pit row in 1b is approximately parallel to the boundary line 71a that divides the photodetectors 711 and 712 of the photodetector 71 and the boundary line 71b that divides the photodetectors 713 and 714 on the photodetector 71, respectively. Since the photodetector 71 is arranged so that the far field patterns 413 and 414 of the first-order diffracted lights 81a and 81b have the pattern arrangement shown in FIGS. 3(a) and 3(c).

Another embodiment of the invention is shown in FIG. Figure 4 (
FIG. 4(b) shows the configuration of the reflective hologram element 62.
represents first-order diffracted lights 82a, 82b, 82c, and 82d generated from the hologram element 62 on the photodetector 72. Another optical pickup head device of the present invention is constructed by using a hologram element 62 in place of the hologram element 61 and a photodetector 72 in place of the photodetector 71, which constitute the optical pickup head device shown in FIG. be able to. In the hologram element region 62a of the hologram element 62, a pattern that generates two first-order diffracted lights 82a and 82b having different focal points is recorded in a superimposed manner, and the beam 81 emitted from the light source 6 is directed to the optical storage medium 4.
When focusing on the top, one first-order diffracted light 82a is in front of the photodetector 72, and the other first-order diffracted light 82b is in front of the photodetector 72.
The hologram element area 62 of the hologram element 62 is focused so that the two first-order diffracted lights 82a and 82b on the photodetector 72 have the same size.
I am designing a pattern for a. In addition, different patterns are recorded in some areas 62c and 62d of the hologram element area 62a, and the hologram element area 62a
First-order diffracted lights 82c and 82d are generated from the first-order diffracted lights 82c and 82d, respectively. For example, when the beam 81 emitted from the light source 6 is focused on the optical storage medium 4, the patterns of the hologram element regions 62c and 62d are formed by the first-order diffracted lights 82c and 62d.
82d may also be designed to be focused on the photodetector 71. The photodetector 72 includes eight photodetectors 721, 722,
723, 724, 725, 726, 727, 728, the first-order diffracted light 82a from the hologram element 62 is detected by the photodetector 722, 723, 724, and the first-order diffracted light 82b
are the photodetectors 725, 726, 727, and the first-order diffracted light 82
c is the photodetector 721, and the first-order diffracted light 82d is the photodetector 7
Each light is received at 28 and converted into an electrical signal. Patterns 421 and 422 on the hologram element 62 are far-field patterns, which are beams 81 diffracted by grooves or pit rows recorded on the optical storage medium 4.
This shows the state of the first-order diffracted light of 0. Here, the grooves or pit rows of the optical storage medium 4 are arranged so as to be approximately parallel to the Y direction, so the pattern arrangement is as shown in FIG. 4(a). Become. 423 and 424 in the first-order diffracted light 82a and 425 and 426 in the first-order diffracted light 82b are also far-field patterns representing the pattern of the beam diffracted by the optical storage medium 4. Alternatively, the mapping of the pit rows is formed by boundary lines 72a, 72b, which divide the area of the photodetector 72, respectively.
By arranging them so as to be substantially perpendicular to 72c and 72d, it is possible to suppress the TE signal from being mixed into the FE signal, thereby making it possible to detect the FE signal with less noise. In this embodiment, a configuration is shown in which a pattern is superimposed and recorded on the hologram element area 62a, but for example, as disclosed in Japanese Patent Application Laid-open No. 2-58728, the hologram element area is divided into two. It is also possible to realize the hologram element 62 by partially recording any of the patterns that generate diffracted light having two different foci.

FIG. 5 shows the hologram element 62 shown in FIG.
and the first-order diffracted light 82a generated by the hologram element 62 detected by the photodetectors 721 to 728 of the photodetector 72 in the optical pickup head device using the photodetector 72,
82b, 82c, and 82d are schematically and generally shown. FIG. 5(b) shows a beam 81 emitted from the light source 6.
is in a focused state on the optical storage medium 4, and FIGS. 5(a) and 5(c) show cases in which the image is defocused in opposite directions. The FE signal is e.g.
By differentially calculating the outputs from and 726, the TE signal can be generated by differentially calculating the outputs from the photodetectors 721 and 728, and the RF signal can be generated by calculating the sum of the outputs from the photodetectors 721 to 728. are obtained respectively. The detection method of FE signal is spot size detection method, TE
The signal is detected by a method called a push-pull method, which is a well-known calculation method. The FE signal is obtained by adding the outputs from the photodetectors 725 and 727 to the output from the photodetector 723, and adds the output from the photodetector 726 to the output from the photodetector 726.
It can also be obtained by adding the outputs from 22 and 724 and performing differential calculation. Also in the present invention, the reflection type hologram element 61 is connected to the optical path between the collimating lens 11 and the objective lens 12, that is, the beam 81 emitted from the light source 6 and the 0th-order diffracted light 810 reflected and diffracted by the optical storage medium 4 are parallel beams. By placing the beam in the optical path where The diffraction efficiency of the element 61 is constant in any region of the hologram element, and no offset occurs in the FE error signal and TE signal, making it possible to realize stable servo operation of the optical pickup head device.

FIG. 6 shows yet another embodiment of an optical pickup head device of the present invention. In this embodiment, in order to realize miniaturization and simplification of the optical pickup head device, the lens hologram integrated element that plays the roles of the collimating lens 11, the reflective hologram element 61, and the objective lens 12 shown in the first embodiment is used. 10 is used to configure an optical pickup head device. The lens hologram integrated element 10 is manufactured through a process similar to that of first manufacturing a mold that forms the functional areas of the collimating lens 11, the reflective hologram element 61, and the objective lens 12, and then manufacturing a press lens using the mold. It is manufactured by. A block 100 equipped with a light source 6 and a photodetector 71 and a lens hologram integrated element 1
0 is fixedly arranged in the housing 102. The magnet 96 and the coil 95 and the magnet 98 and the coil 97 constitute actuators for focusing and tracking, respectively, and the FE signal and TE signal obtained by calculating the electric signal obtained from the photodetector 71 are By applying voltage to the coils 95 and 97, it is possible to realize focus and tracking servo operations that follow the displacement of the optical storage medium. In the optical pickup head device shown in this example, all the optical systems that make up the optical pickup head device are integrally driven to perform servo operation, so the positional shift of the optical system is unlikely to occur and signal detection can be performed extremely stably. It becomes an optical pickup head device. Here, we have shown an example in which the hologram element, objective lens, and collimating lens are integrally molded to form one part, but if necessary, the objective lens and hologram element or the collimating lens and the hologram element can be integrally molded to form one part. Of course, it is also possible to construct an optical pickup head device by forming two parts. Furthermore, the FE signal detection method in the optical pickup head device of the present invention is as follows:
Not only the double knife edge method and the spot size detection method shown in the embodiment, but also other methods such as the astigmatism method and the phase difference method can be applied without any problem. Furthermore, various signal detection methods can be similarly applied to the TE signal.

[0014]

Effects of the Invention The present invention includes a semiconductor laser light source that emits a coherent beam or a quasi-monochromatic beam, a collimating lens that converts a diverging beam from the light source into a parallel beam, and a collimating lens that reflects and diffracts the parallel beam to change the optical path. a reflective hologram element that bends; an objective lens that receives the parallel beam reflected by the hologram element and converges it onto a minute spot on an optical storage medium; and an objective lens that receives the beam reflected and diffracted by the optical storage medium and outputs a photocurrent. An optical pickup head device is configured using a photodetector having a plurality of photodetecting sections, and the reflective hologram element collects a beam that is reflected and diffracted by the optical storage medium and then passes through an objective lens to become a parallel beam. By generating diffracted light that is guided to the photodetector, the beam that enters the reflective hologram element is a parallel beam, so the incident angle in any area of the beam is the same as the angle between the reflective hologram element and the optical axis. Since the incident angle is equal to , the diffraction efficiency of the reflective hologram element is constant in any area of the hologram element.As a result, by calculating the output from the photodetector that receives the first-order diffracted light from the hologram element, No offset occurs in the obtained focus error signal and tracking error signal, making it possible to realize stable servo operation of the optical pickup head device.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an optical pickup head device showing an embodiment of the present invention.

FIG. 2(a) is a configuration diagram of a hologram element constituting an optical pickup head device showing an embodiment of the present invention. (b) is a relationship diagram between the diffracted light generated from the hologram element shown in (a) of the same figure and a photodetector.

FIG. 3 is a diagram showing the relationship between diffracted light and a photodetector, showing the signal detection method of the optical pickup head device of the present invention.

FIG. 4(a) is a configuration diagram of a hologram element constituting an optical pickup head device showing another embodiment of the present invention. (b) is a relationship diagram between the diffracted light generated from the hologram element shown in (a) of the same figure and a photodetector.

FIG. 5 is a diagram showing the relationship between diffracted light and a photodetector, showing a signal detection method of an optical pickup head device according to another embodiment of the present invention.

FIG. 6 is a configuration diagram of an optical pickup head device showing still another embodiment of the present invention.

FIG. 7 is an example diagram showing the relationship between the angle of incidence on a diffraction element and diffraction efficiency.

FIG. 8 is a configuration diagram showing a conventional optical pickup head device.

FIG. 9 is a cross-sectional view showing a beam in a conventional optical pickup head device.

[Explanation of symbols]

1 Optical storage medium 2 Recording surface 3 Diffraction element 3a Diffraction grating area 3b Diffraction grating area 4 Optical storage medium 6. Light source 7. Light source 8 Beam 8a 1st order diffracted light 8b 1st order diffracted light 8L beam 8U beam 10 Lens hologram integrated element 11 Collimating lens 12 Objective lens 13a Photodetector 13b Photodetector 13e Photodetection section 13f Photo detection section 13g Photo detection section 13h Photo detection section 16 Objective lens 17 Collimating lens 41　Substrate 42 Protective film 61 Reflective hologram element 61a Hologram element area 61b Hologram element area 61c Parting line 62 Reflective hologram element 62a Hologram element area 62c Hologram element area 62d Hologram element area 71 Photodetector 71a Boundary line 71b Boundary line 72 Photodetector 72a Boundary line 72b Boundary line 72c Boundary line 72d Boundary line 81 Beam 81a 1st order diffracted light 81b 1st order diffracted light 81c Optical axis 81d Optical axis 82a 1st order diffracted light 82b 1st order diffracted light 82c 1st order diffracted light 82d 1st order diffracted light 91 Coil 92 Magnet 93 Coil 94 Magnet 95 coil 96 magnet 97 Coil 98 magnet 100 blocks 101 Housing 102 Housing 411 Far field pattern 412 Far field pattern 413 Far field pattern 414 Far field pattern 421 Far field pattern 422 Far field pattern 423 Far field pattern 424 Far field pattern 425 far field pattern 426 far field pattern 711 Photo detection section 712 Photo detection section 713 Photo detection section 714 Photo detection section 721 Photo detection section 722 Photo detection section 723 Photo detection section 724 Photo detection section 725 Photo detection section 726 Photo detection section 727 Photo detection section 728 Photo detection section 810 0th order diffracted light

Claims (6)

[Claims] 1. A semiconductor laser light source that emits a coherent beam or a quasi-monochromatic beam; a collimating lens that converts a diverging beam from the light source into a parallel beam;
a reflective hologram element that reflects and diffracts the parallel beam to bend the optical path; an objective lens that receives the parallel beam reflected by the hologram element and converges it onto a minute spot on an optical storage medium; , a photodetector having a plurality of photodetecting sections that receive the diffracted beam and output a photocurrent, and the reflective hologram element transmits the objective lens after being reflected and diffracted by the optical storage medium to produce a parallel beam. An optical pickup head device that receives the beam and generates diffracted light that is guided to the photodetector. 2. The optical pickup head device according to claim 1, wherein the hologram element is blazed. [Claim 3] Claim 1, characterized in that the collimating lens and the reflective hologram element are integrally formed.
The optical pickup head device described. 4. The optical pickup head device according to claim 1, wherein the collimating lens, the reflective hologram element, and the objective lens are integrally formed. 5. The optical pickup head device according to claim 1, further comprising a focus and tracking actuator that performs focus and tracking servo operations by driving an objective lens constituting the optical pickup head device. 6. The optical pickup head device according to claim 1, further comprising a focus and tracking actuator that drives all optical systems constituting the optical pickup head device to perform focus and tracking servo operations.