JPH0460932A - Optical pickup head device - Google Patents

Abstract

PURPOSE:To enable stable focus and tracking control by arranging a photodetector at a certain position which is apart from a hologram element rather than a first face perpendicular to the optical axis of a light source including the first light emitting point of the light source, and is opposed to the light source while holding a block therebetween. CONSTITUTION:Photodetectors 510-517 and the light source are arranged at certain positions opposed to each other while holding a block 33 therebetween for radiating heat, which is generated from the light source, thereby, an optical storing medium 34 is irradiated with a beam from the light source. Accordingly, the block 33 is separated so that the photodetectors 510-517 for receiving the diffracted light from a hologram element 36 does not receive the beam to be emitted from a second light emitting point 14 of the light source counter to a first light emitting point 13 of the light source while holding the light source therebetween. Thus, an FE signal, TE signal, RF signal and laser output control signal generating no offset can be detected by the photodetectors 510-517 formed on one substrate, and a stable operation can be executed while simplifying the configuration of an optical system.

Description

[Detailed description of the invention] Industrial application field The present invention L! , Recording and recording of optical information stored on optical media or magneto-optical media such as optical disks or optical cards.
The present invention relates to an optical pickup head device that can be reproduced or erased.

Conventional technology Optical memory technology that uses optical disks with pit-like patterns as high-density, large-capacity storage media (such as digital audio disks, video disks, document file disks, and even data files) has been put into practical use while expanding its uses. The mechanism by which the recording and reproducing of information on an optical disk through a light beam focused on the micron order is successfully carried out with high reliability depends solely on the optical system. The basic functions of the optical pickup head device, which is the main part of the system
,) Light focusing ability to form a diffraction-limited minute spot, (positive)
There are three main types of control: focus control of the optical system, pit signal detection, and pit signal tracking control. These (dai
Depending on the application, this is achieved by combining various optical systems and photoelectric conversion detection methods, especially in order to simplify and downsize the optical system. A technique is disclosed in which wavefronts are recorded and each wavefront reproduced by a reading beam of an optical pickup head device is guided to a photodetector. 11~2' 1) US Patent 4,358.20011/
1982 “0ptical Focusing-e”
Detection Method'2)
B5Patent 4,665,310 5/1
987 “Apparatus foroptic
ally scanning an information
ion plane where a diffr
action grating 5plitsthe
beam 1nto two-beams 3) US Patent 4,731.772 5/1
988"0ptical Heading Hole
ogram Lens for both Beam
Splitting and Focus Error
Detection Function The above-mentioned technologies have made it possible to house a light source and a photodetector in the same package to make the optical pickup head device more compact. We have proposed an optical pickup head device that accommodates both in the same package and is highly suitable for mass production (Japanese Patent Application No. 175364).

For example, FIG. 7(a) shows the configuration of the optical pickup head device shown in Japanese Patent Application No. 1-75364.
FIG. 1B shows a top view of a hybrid device consisting of a light source, a photodetector unit, and a package that constitute the optical pickup head device shown in FIG. The same figure (a
), 2 is a semiconductor laser that emits a coherent beam (for example, wavelength λ = 780 nm), 12 is a photodetector unit, 3 is a block that dissipates the heat generated from the light source 1, and 2 is a block that houses the light source 1 and the photodetector unit 12. The light source 1, the block 3, the photodetector unit 12, and the package 2 constitute a hybrid device. 101
is a connection terminal that allows the light source 1 and photodetector unit 12 housed in the package 2 to be connected to an external circuit;
8 is a finite focus focusing lens; 91 is an actuator lens for focus control; 92 is an actuator lens for tracking control; 4 is an optical storage medium (optical disk); The light is focused onto the optical disk 4. In this case, 6 is a hologram element capable of reproducing two wave fronts having different focal points, and a different diffraction grating is formed in a part of this hologram element 6, which is interposed between the light source I and the lens 8, and is The 0th order diffracted light 800 will be focused on the optical disk 4. In the optical disc 4, 2o is a substrate on which grooves or pits are formed, and 21 is a protective film.

The diffracted beam reflected on the optical disk 4 passes through the lens 8 again on the return path, and then enters the hologram element 6, where it is diffracted in the optical axis direction. Two diffracted light wavefronts 81 and 82 with different focal points and tracking error (hereinafter abbreviated as FE) signals are obtained by the
As shown in the figure (b), the diffracted light 81 is transmitted to the photodetectors 502 to 504, the diffracted light 82 is transmitted to the photodetectors 505 to 507, and the diffracted light 83 is transmitted to the photodetectors 505 to 507. Photodetector 5
The 01° C. diffracted light 84 is received by a photodetector 508, respectively. 23 is a connection terminal 1 that allows connecting the light source 1 and photodetector unit 5 to an external circuit.
This is the bonding wire connected to 01. Also
to monitor and control the output of light source 1.
The light emitted from the light emitting point 11 is received by the photodetector 509, and the FE multiplied signal, TE multiplied signal, high frequency information (hereinafter referred to as RF
The configuration of the optical system is simplified by making it possible to detect the signal (abbreviated as ``1'') and the laser output control signal using a photodetector formed on one substrate.

Problems to be Solved by the Invention However, in an optical pickup head device using this hybrid device, the beam emitted from the second light emitting point 11 of the light source 1 is transmitted to the photodetector 50.
1 from the hologram element 6.
Photodetector 501 that receives the next diffracted lights 81 to 84
There is a problem in that the focus and tracking control may become unstable due to the FE multiplied signal and TE multiplied signal offset caused by the FE multiplied signal and TE multiplied signal offset. The problem is that unnecessary light other than the first-order diffracted lights 81-84 from the hologram element 6 must be prevented from entering the photodetectors 501-5°8 that receive the first-order diffracted lights 81-84 from the hologram element 6. Was there an invention? It is an object of the present invention to provide an optical pickup head that detects an iFE signal, a TE multiplied signal, an RF multiplied signal, or a laser output control signal with a photodetector formed on one substrate, and performs stable focusing and tracking control.

Means for Solving the Problems In order to solve the problems described above, the present invention includes a semiconductor laser light source that emits a coherent beam or a quasi-monochromatic beam, and an optical storage medium that receives the beam emitted from a first light emitting point of the light source. A condensing optical system that converges upward into a minute spot, a hologram element that receives the beam reflected by the optical storage medium and generates diffracted light,
In an optical pickup head device comprising a photodetector unit that receives diffracted light from the hologram element and outputs a photocurrent, the light source and the photodetector unit are housed in the same package, and the light source absorbs heat generated from the light source. The photodetector unit is mounted on a block for dissipation, and the photodetector unit is composed of a plurality of photodetectors formed on the same semiconductor substrate. The optical axis of the light source including a point is located at a position that is farther from the hologram element than the first surface perpendicular to it and faces the light source with the block in between.

Function: In the optical pickup head device of the present invention, a photodetector and a light source are arranged at opposite positions with a block for dissipating heat generated from the light source interposed therebetween, so that the light source emits a beam from the light source to the optical storage medium. The first light emitting point is the second light emitting point of the light source that faces the light source with the light source in between.
The block isolates the beam emitted from the light emitting point of the hologram element so that the photodetector that receives the diffracted light from the hologram element does not receive the beam, so that no offset occurs.
The E-fold signal, the TE-fold signal, the RF-fold signal, and the laser output control signal can be detected by a photodetector formed on one substrate, resulting in an optical pickup head device that simplifies the configuration of the optical system and operates stably.

Embodiment FIG. 1 shows a schematic configuration of an optical pickup head device according to an embodiment of the present invention. In the figure, 31 is a semiconductor laser that emits a coherent beam (for example, wavelength λ=7
80nm), 35 is a photodetector unit, 3
3 is a block 32 that dissipates heat generated from the light source 31
is a package that houses the light source 31 and the photodetector unit 35, and the light source 31 and the heat dissipation block 33
The photodetector unit 35 and package 32 constitute a hybrid device. 102 is a connection terminal that enables connection of the light source 31 and photodetector unit 35 housed in the package 32 with an external circuit;
38 is a finite focus focusing lens; 93 is an actuator for focus control; 94 is an actuator for tracking control; 34 is an optical storage medium (optical disk); the beam emitted from the light source 31 is transferred to the optical disk 34 by the lens 38; The light is focused on the top. At this time, 36 is a hologram element capable of reproducing two wavefronts having different focal points, and a different diffraction grating is formed in a part of this hologram element 36, which is interposed between the light source 31 and the lens 38 and is The 0th order diffracted light 700 will be focused on the optical disk 34. In the optical disc 34, 40 is a substrate in which grooves or pits are formed, and 41 is a protective film. The beam 700 reflected and diffracted on the optical disk 34 passes through the lens 38 again on the return path, and then passes through the hologram element 36.
In addition to the 0th-order diffracted light 700 that is incident on the optical axis and diffracted in the optical axis direction, there are two diffracted light wavefronts 71 and 72 with different focal points outside the axis to obtain the FE multiplied signal, and a wavefront 73 to obtain the TE multiplied signal. Generates .74.

A method of designing the hologram element 36 will be described later. The diffracted lights 71 to 74 are received by a photodetector unit 35 whose light receiving surface is located closer to the bottom of the package 32 than the light emitting point 13 of the light source 31. By arranging the photodetector unit 35 at the bottom of the package 32, it is possible to arrange the photodetector unit 35 and the upper part of the connection terminal 102 on the same plane while keeping the height of the connection terminal 102 in the package 32 low. It is possible to keep the wire short and stable.

Furthermore, by arranging the photodetector units 35 at positions facing each other across the block 33 for dissipating the heat generated from the light source 31, the light source 31 can be dissipated from the optical storage medium 3.
4 First light emitting point 1 of the light source that emits the heavy beam 700
3 means that the beam emitted from the second light emitting point 14 of the light source 31 facing each other with the light source 31 in between is transmitted to the hologram element 36.
Since the block 33 serves to isolate the photodetector unit 35 that receives the diffracted lights 71 to 74 from the FE multiplied signal and the TE multiplied signal light source 31, no offset occurs due to the reception of unnecessary light from the FE multiplied signal TE multiplied signal light source 31. .

FIG. 2 explains the embodiment of the present invention in more detail, and shows a hybrid device composed of a light source 31, a heat dissipation block 33, a photodetector unit 35, and a package 32. Figure (a)
A cross-sectional view of the hybrid device, shown in the same figure (b
) shows the package 32 viewed from above. 24 is a bonding wire connected to the connection terminal 102 that allows the light source 31 and photodetector unit 35 to be connected to an external circuit. Here, the hologram element 36 is attached to the package 32. Distance dζ from the surface 113 including the light emitting point 13 of the light source 31 to the surface 110 including the light receiving surface of the photodetector unit 35
This is allowed by providing the hologram element 36 with a light condensing function corresponding to d, that is, a substantially concave lens function. At this time, since the magnification of the optical system is increased by giving the hologram element 36 a concave lens effect, there is an advantage that it is possible to detect a good FE multiplied signal with high sensitivity.
Two diffracted lights 71 with different focal points to obtain double signal
72 and wavefronts 73 and 74 for obtaining the TE multiplied signal. The hologram element 36 is designed as follows. When the beam 700 emitted from the light source 31 is in focus with respect to the optical disk 34, the diffracted lights 71 and 72 from the hologram element 36 used for detecting the FE multiplied signal are transmitted to the photodetector 511 in the photodetector unit 35.
δ1 and δ from the photodetector lid unit surface 110, respectively, so that the beam sizes on ~516 are equal.
A focal point P1 is determined on the surface 111 and a focal point P2 is determined on the surface 112, which are located at a distance of 2. On the other hand, the focus of the diffracted lights 73 and 74 from the hologram element 36 used for detecting the TE multiplied signal is determined so as to have a beam size that does not extend beyond the photodetectors 510 and 517 that constitute the photodetector unit 35, for example. Focus P3 on unit 35. All you have to do is set PJ. The lattice pattern on the hologram element 36 is interference fringes generated when the beams emitted from these light sources overlap at the position of the hologram element 36, using the light emitting point 13 of the light source 31 and the optical focal points P1 to P4 of the reference light as the light source of the object light. can be obtained by recording in a desired area of the hologram element 36. As a means of recording the hologram element 36, two-light east interferometry and computer generate are used.
d Hologram (CGH), and since these technologies are well known from the past, detailed explanations will be omitted.

FIG. 3 (Table) is an example of a pattern recorded on the hologram element 36, and the figure ('!, schematically shows the functional area division of the hologram element 36. Hologram element 36L
l. An area 641 where two wavefronts with different focal points can be reproduced for FE signal detection, and an area 642 where grid patterns are recorded in different directions for TE signal detection.
, 643 and a non-hologram area 644. By making the far field patterns 411 and 412 of the beam 700 reflected and diffracted by the optical disk 34 incident on the hologram element 36 as shown in the figure, a good TE multiplied signal can be detected. The wavefront reproduced from the hologram element 36 is the diffracted light 71 as shown in FIG. 2(b).
and 72 from the functional area 641 of the hologram element 36,
The diffracted lights 73 and 74 are reflected in the functional area 6 of the hologram element 36.
42 and 643, respectively. By forming the non-hologram region 644 in the hologram element 36, even if the lens 38 moves with tracking control and the beam aperture is restricted, the TE multiplied signal is less likely to be offset, allowing stable tracking control. becomes. Furthermore, no matter what position the hologram element 36 is inserted into the beam 700 reflected and diffracted by the optical disk 34, the TE signal component will be mixed in with the FE multiplied signal, making it possible to stably detect the FE multiplied signal. It is. It is also possible to form a diffraction grating that serves as a dummy in the non-hologram region 644 to keep the beam intensity distribution uniform, or to form a hologram element for detecting an FE or TE multiplied signal.

Next, the signal detection method in the embodiment will be explained in detail. FIG. 4 LL schematically and generally represents the relationship between the diffracted lights 71 to 74 detected in each of the photodetector regions 510 to 517 of the photodetector unit 35 in the hybrid device shown in FIG. 2(b). FIG. 4(b) shows a case where the beam 700 emitted from the light source 31 is focused on the optical disk 34, and FIGS. 4(a) and (c) each show a defocused state with opposite phases. .

The FE multiplied signal can be obtained, for example, by taking the differential outputs of photodetectors 512 and 515. This FE multiplied signal detection method is called spot size detection and is a well-known fact. Also, for example, by adding the outputs of 514° and 516 to the output of photodetector 512, and the outputs of 511 and 513 to the output of photodetector 515, the differential output is increased. On the other hand, it can be obtained by taking the differential outputs of the TE multiplied signal photodetectors 510 and 517. Ma? , RF signals are obtained by summing the outputs of photodetectors 510-517.

FIG. 5 is a conceptual diagram showing another embodiment of the present invention. The same figure (a) schematically shows the functional area division of the hologram element 61.
Diffraction grating area 63 that can divide the wavefront for E signal detection
1 and 632.

The far-field patterns 411 and 412 of the beam 700 that has been diffracted by the optical disk 34 are shown in the same figure (
As shown in a), by making the light incident on the hologram element 61, FE and TE multiplied signals can be detected. This FE multiplied signal detection method is a well-known fact called the double knife method. Figure 2 (b) LL, for example Figure 2 (b)
) In the case where a photodetector unit 37 is used instead of the photodetector unit 35 in a hybrid device as shown in FIG. Hologram element 6 on the resulting photodetector unit 37
Diffracted light 75 and 76 are reproduced from functional areas 631 and 632 of hologram element 61.
You can get each one separately. Photodetector unit 37
is composed of a plurality of photodetectors 518 to 521, and due to the difference between the output sum of the FE multiplied signal photodetectors 518 and 521 and the output sum of the photodetectors 519 and 520, the output sum of the TE multiplied signal photodetectors 518 and 519 and the output sum of the photodetector 520 and 521, the RF multiplied signal detection method can be obtained by summing the outputs of photodetectors 518 to 521. When the beam 700 emitted from the light source 31 is focused on the optical disk 34, the first-order diffracted light beams 75 and 76 from the hologram element 61 are each focused on the photodeverter unit 3. The spot size detection method and double knife detection method, which are the FE multiplied signal detection methods shown above, are just examples, and of course there are other FE signal detection methods, such as non- A point aberration method, a single knife method, etc. can also be applied to the present invention.

FIG. 6 is a conceptual diagram of a hybrid device showing still another embodiment of the present invention. The hybrid device shown here is realized by replacing the photodetector unit 35 constituting the hybrid device shown in FIG. Ru. Photodetector unit 394 Diffracted light 71~ from hologram element 36
In addition to the photodetectors 510 to 517 that receive the light 74, the light source 3 is used to monitor and control the output of the light source 31.
A photodetector 522 is formed to receive light emitted from the second light emitting point 14. Since the method of keeping the output of the light source constant is a well-known technique, the explanation thereof will be omitted here. The FE multiplied signal, the TE multiplied signal, the RF multiplied signal, or even the laser output control signal can be detected by a photodetector formed on one substrate.
It is possible to reduce the number of parts.

Effects of the Invention As is clear from the detailed explanation given above, the optical pickup head device according to the invention uses a semiconductor laser light source that emits a coherent beam or a quasi-monochromatic beam, and a beam emitted from a first light emitting point of the light source. A condensing optical system converges the received light into a minute spot onto a storage medium, a hologram element that receives the beam reflected and diffracted by the optical storage medium and generates diffracted light, and a hologram element that receives the diffracted light from the hologram element and generates a photocurrent. In an optical pickup head device, the light source and the photodetector unit are housed in the same package, the light source is attached to a block for dissipating heat generated from the light source, and the photodetector unit is housed in the same package. The photodetector is composed of a plurality of photodetectors formed on a semiconductor substrate and receives diffracted light from a hologram element formed in the photodetector unit. A first light emitting point of the light source that emits a beam from the light source onto the optical storage medium by disposing it at a position that is farther from the hologram element than the surface and facing the light source across the block. Since the block isolates the beam emitted from the second light emitting point of the light source facing each other with the light source in between, the photodetector that receives the diffracted light from the hologram element does not receive the beam, so that no offset occurs in the FE and TE. This has the effect that the double signal, the RF double signal, and the laser output control signal can be detected by a photodetector formed on one substrate.

[Brief explanation of drawings]

FIG. 1 shows a schematic configuration of an optical pickup head device according to an embodiment of the present invention. FIG. 2(a) shows a side view of a hybrid device constituting the optical pickup head device shown in FIG. b,) is a top view of the hybrid device that constitutes the optical pickup head device shown in FIG. 1. Figure 3 is a schematic diagram of the hologram element that constitutes the optical pickup head device shown in
), (b), and (c) show the principle of a single membrane in which a signal is detected. FIG. 6 is a top view of a hybrid device explaining another embodiment of the present invention. FIG. 7(a) is a conventional optical 1. Configuration of an example of a pickup head device FIG. 2B is a top view of a hybrid device that constitutes the optical pickup head device shown in FIG. 1A. 13...First light emitting point, 14...Second light emitting point A
31... Semiconductor laser or equivalent coherent tip 32... Package, 33... Block
34... Optical storage medium (optical disk), 35... Photodetector unit, 36... Hologram element, 38... Lens, 40... Substrate, 41...
Protective air 71 to 74... 1st order diffracted light 93... Actuator for focus control 94... Actuator for tracking control 102... Connection terminal, 70
... Name of agent for 0th order diffracted light Patent attorney Shigetaka Awano and 1 other person - Kyu - 1st row g navigation 1st ``Go'' to o-1゛ to lh ,,,, too. , 6 trillion spirits, river g @ sea 11 ha 7 arrogance - mackerel 411 ri zero 〇■ ) 1ε Koikuhe, 311'+ , 1 hagu) l hello O + 6 r + tatami desire mo ku

Claims (3)

[Claims] (1) A semiconductor laser light source that emits a coherent beam or a quasi-monochromatic beam, a condensing optical system that receives the beam emitted from the first light emitting point of the light source, and converges it onto a minute spot onto an optical storage medium; An optical pickup head device comprising a hologram element that receives a reflected and diffracted beam and generates diffracted light, and a photodetector unit that receives the diffracted light from the hologram element and outputs a photocurrent, the light source and the photodetector unit are housed in the same package, the light source is mounted on a block for dissipating heat generated from the light source,
The package has an input/output terminal that allows the light source and the photodetector unit housed inside to be connected to an external circuit, and the photodetector unit is composed of a plurality of photodetectors formed on the same semiconductor substrate, and the hologram A photodetector formed in the photodetector unit that receives diffracted light from the element is located further away from the hologram element than a first surface that includes a light emitting point of the light source and is perpendicular to the optical axis of the light source, and which receives light from the light source. a first of said light sources that emits a beam to a storage medium;
The light emitting point is located at a position opposite to the light source across the block so as not to substantially receive the beam emitted from the second light emitting point of the light source facing across the light source. An optical pickup head device characterized by: (2) The first light-emitting point of the light source that emits a beam from the light source to the optical storage medium is a photodetector that receives the beam that is emitted from the second light-emitting point of the light source that faces across the light source. The optical pickup head device according to claim 1, wherein the optical pickup head device is formed in a photodetector unit. (3) The light source is attached to a block for dissipating heat generated from the light source, and the block is arranged on a photodetector unit. Optical pickup head device.