JPH0316039A - Optical pickup head device - Google Patents

Abstract

PURPOSE:To improve the work efficiency of a bonding work for bringing a photodetector unit and a connecting terminal to wiring and to miniaturize the optical pickup head device by placing the surface of the photodetector unit and the upper part of the connecting terminal in a package roughly on the same plane. CONSTITUTION:This device is provided with a semiconductor laser 1 for emitting a coherent beam, a photodetector unit 5, a block 3 for radiating heat generated from the light source 1, and a package 2 containing the light source 1 and the photodetector unit 5, and a hybrid device is constituted of the light source 1, the photodetector unit 5 and the package 2. In such a case, by placing the photodetector unit 5 in the bottom part of the package 2, the photodetector unit 5 and the upper part of a connecting terminal 101 can be placed on the same plane in a state that height of the connecting terminal 101 in the package 2 is held low, and a bonding wire can be held shortly and stably. In such a way, the device can be miniaturized.

Description

[Detailed Description of the Invention] Industrial Field of Application 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. Amo Conventional technology Optical memory technology that uses optical disks with bit-like patterns as high-density, large-capacity storage media (friends, digital audio disks, video disks, document file disks, and further expands the use of data files and applications). The mechanism by which the recording and reproducing of information on an optical disk is successfully carried out with high reliability through a light beam focused on the micron order (this is entirely due to its optical system) Basic functions of the optical pickup head device, which is the main part of the optical system (Friend (5)
They can be roughly divided into three types: (6) focus control of the optical system and bit signal detection, and (7) tracking control to form a diffraction-limited minute spot.
Depending on the application, this is achieved by combining various optical systems and photoelectric conversion detection methods. Wavefronts are recorded and each wavefront reproduced by a reading beam of an optical pickup head device is guided to a photodetector.
1/1982 “Optical Focusing
-error Detect. ion Method”
'2) US Patent 4.665.310
5/1987 “Apparatus for opti
Cally scanning an information
ation plane where in a diff
ration grating splits t
he beat int. o two-beam
s″3) US Patent 4,731.772
5/X988 ”Optical Head u
sing Hologram Lens for bo
th Beam Splitting and Foc
us Error Detection Function
on' The technology shown above will eventually make it possible to house the L light source and the photodetector in the same package, making it possible to downsize the optical pickup head device.

For example, in Figure 8 USP4, 73 1, 4 7
The structure of the optical pickup head device shown in Fig. 2 (Fig. 4 in USP 4, 731,
772). 68 is a hybrid device that houses a semiconductor laser light source and a photodetector in the same package, and the coherent beam 7 emitted from the light source
After entering the hologram element 74, the 0th-order diffracted light, which is transmitted light, is focused onto the optical disc 78 by the lens 76. Optical disc 7
The diffracted beam (friend) passes through the I-nons 76 again and enters the hologram element 74.The hologram element 74 generates 1st-order diffracted light in addition to the 0th-order diffracted light, which is the transmitted light. After passing through the lens 72, the first-order diffracted light is focused onto a photodetector in the hybrid device 68, and the photodetector outputs a photocurrent.Focus error (FE) signal tracking error (
TE) signal Even if a radio frequency information (RF) signal is detected, the beam 70 is focused on the optical disk 78.
A hybrid device that houses a light source and a photodetector in one package with a focus and tracking actuator that controls the position of a lens 76 so that the information recorded on the optical disc can be read by following the bits or grooves on the optical disc. Top view of 68 (Fig. 3
(in USP 4, 757, 197) is shown in FIG. 38, 42, 46, 50,
52, 54. 56. Reference numeral 58 indicates a connection terminal that allows connection of the light source 32 and photodetector 44, 48 housed in the package with an external circuit; 36, 40 indicates a bonding wire that connects the light source 32 and photodetector 44 to the connection terminal; and 34 indicates a connection terminal that is generated from the light source 32. 44 is a photodetector for monitoring the output of the light source 32; 48 is a photodetector for receiving the first-order diffracted light from the hologram element 74;
Optical pickup head device shown in SP4,731,772 (Friend USP4,75
By using the hybrid device 68 shown in No. 7, 197, the size of the optical pickup head device is realized.
197, the side view of the hybrid device 68 is not shown.
g. 2 in USP4, 7 5 9 7
．． 1 9 7) and Fig showing the appearance from above.
．． 3 in USP 4,757,197, it is possible to consider the configuration shown in Figure 10.Light source 3
2 and the photodetector 48 are mounted on the top and side of the same block 34, respectively, for integration.Even if a compact structure is realized, the problem that the invention attempts to solve is that the hybrid device 68 is manufactured on a single board. In the process of connecting, the connection terminals 38, 42, 46
, 50, 52, 54, 56. 58
Since there is a step between the photodetector 48 and the photodetector 48, the photodetector 48 and the connection terminals 38, 42, 46,
50, 52, 54, 56. The length of the bonding wire that connects to Not necessarily,
Therefore, the distance between each connection terminal must be set wide.l. If the distance between each connecting terminal is set wide in order to avoid short-circuiting of the bonding wires, the hybrid device 68 will become large, and its optical pickup head device will also become large.

In addition, in the configuration shown in FIG. 10, the photodetector 48
and connection terminals 38, 42, 46, 50,
52, 54. 56. Since there is a step in 58, bonding work requires three-dimensional movement, which is inefficient and unsuitable for mass production. As described above, the hybrid device shown in FIG. 10 has problems in making the optical pickup head device smaller and mass-producing it.An object of the present invention is to provide an optical pickup head that is small in size and excellent in mass production. Means for Solving the Problems In order to solve the above problems, the present invention provides a hybrid device (a hybrid device in which a photodetector unit consisting of an upper laser light source and a plurality of photodetectors is housed in the same package; An optical pickup head device is constructed using a condensing lens that receives light and focuses it onto an optical disk, which is an optical storage medium, and a hologram element that receives a beam of light reflected and diffracted and returned from the optical disk and generates diffracted light in the direction of a photodetector unit. Furthermore, in the optical pickup head device of the present invention (the photodetector unit in the companion package is arranged closer to the bottom of the package than the light emitting point of the light source, the surface of the photodetector unit and the upper part of the connection terminal in the package are The arrangement of the photodetector unit (which is arranged approximately on the same plane) allows the photodetector unit to function even if it is allowed by using a hologram element having a substantially concave lens function in the hologram area that generates the diffracted light used to detect the focus error signal. In the optical pickup head device of the present invention, the photodetector unit in the package is arranged closer to the bottom of the package than the light emitting point of the light source, so that the surface of the photodetector unit and the top of the connection terminal in the package are approximately on the same plane. This arrangement improves the work efficiency of bonding work for wiring the photodetector unit and the connection terminals, thereby reducing the size and reliability of the optical pickup head device. The schematic structure of the OPU device is shown. In the figure, 1 is a semiconductor laser that emits a coherent beam (for example, wavelength λ2α 780 nm).
, 5 is a photodetector unit, 3 is a package for dissipating heat generated from the light source 1, and 2 is a package that houses the light source 1 and the photodetector unit 5. The light source 1, the photodetector unit 5, and the package 2 form a hybrid device. I am wary of this. Is 101 the light housed in package 2? ! 8 is a finite focus focusing lens X; 91 is an actuator for focus control; 92 is an actuator for tracking control; 4 is an optical storage medium (optical disk); Yes, light source 1
The beam 800 emitted from the hologram element 6 is focused onto the disk 4 by the lens 8. At this time, 6 is a hologram element capable of reproducing two wavefronts with different focal points, and different diffraction gratings are formed in a part of this hologram element 6. interposed between the light source 1 and the lens 8, and the O-th order diffracted light 8
00 will be focused on the disk 4. In the disk 4, 20 is a substrate in which grooves or bits are formed, and 21 is a protective film.The beam reflected and diffracted on the disk 4 passes through the lens 8 again on the return path, and then enters the hologram element 6. In addition to the 0th-order diffracted light 800 that is diffracted in the optical axis direction, two diffracted light wavefronts 81 and 82 having different focal points for obtaining an FE signal and wavefronts 83 and 84 for obtaining a TE signal are generated off the optical axis. The design method of the hologram element will be described later.The diffracted lights 81 to 84 are received by the photodetector unit 5 whose light receiving surface is located closer to the bottom of the package than the light emitting point lO of the light source 1. By arranging the photodetector unit 5 at the bottom, it is possible to arrange the photodetector unit 5 and the upper part of the connection terminal 101 on the same plane while keeping the height of the connection terminal 10l in the package 2 low. It is possible to keep the wire short and stable, and the bonding work can be done with flat one-dimensional or two-dimensional movement.
When performing bonding work while monitoring the surface of the photodetector unit l-5 and the surface of the connection terminal 101 in the hybrid device with an iTV camera,
The focus of the camera does not need to be adjusted at all during the bonding process, resulting in a significant reduction in the time required to fabricate the hybrid device. Furthermore, the bonding wire can be wired short and stably, and its bonding
Since it is possible to set the spacing between the connection terminals narrower, the optical pickup head device can be made smaller. Although the hybrid device constructed from unit 5 and package 2 is shown, Figure (a) shows the hybrid device viewed from the cross section, and Figure (b) shows the view from the top of package 2. A wire 23 is a bonding wire connected to a connecting terminal 10l that allows the light source 1 and the photodetector unit 5 to be connected to an external circuit.The hologram element 6 is attached to the package 2 here. The distance d i from the surface 113 including the light emitting point 10 of the light Bl to the surface 11O including the light receiving surface of the photodetector unit 5 is allowed by providing the hologram element 6 with a condensing action corresponding to d, that is, a substantially concave lens action. Ru.

At this time, since the magnification of the optical system is increased by providing the hologram element 6 with a concave lens effect, a new advantage is obtained that a good FE signal with high sensitivity can be detected. Here, the hologram element 6 produces two diffracted beams 81 and 82 with different focal points to obtain the FE signal and wavefronts 83 and 84 to obtain the TE signal.The design of the hologram element 6 is as follows. Light source 1
When the beam emitted from the optical disc 4 is in focus with respect to the optical disk 4, the diffracted lights 8l and 82 from the hologram element 6 used to detect the FE4 word are separated so that their beam sizes on the photodetector unit 5 are equal. A focal point P. is placed on a surface 111 located at a distance of δ and δ2 from the photodetector unit surface 110. On the other hand, the diffracted lights 83 and 84 from the hologram element '6 used for detecting the TE signal have a beam size that does not protrude from the photodetector that constitutes the photodetector unit 5. Decide on the focus as
For example, the focal point Ps, P=
Set the lattice pattern on the hologram element 6 to the light emitting point lO of light #I1 and the light point Pi of the reference light.
Means for recording the hologram element 6 can be obtained by using P4 as a light source of the object light and recording interference fringes produced by the beams emitted from these light sources overlapping at the position of the hologram element 6 in a desired area of the hologram element 6. Examples include three-beam interferometry and computer Ge
There is a nerated hologram (CGH), and as these technologies are well known, a detailed explanation will be omitted, but an example of the pattern recorded on the hologram element 6 is shown in Figure 3 (a). l Dai Even if the functional area division of hologram element 6 is schematically shown, hologram element 6? i
An area 641 in which two wavefronts with different focal points can be reproduced for FE signal detection, and areas 642 and 6 in which grid patterns are recorded in different directions for TE signal detection, respectively.
43 and a non-hologram area 644. By making the far field patterns 411 and 412 of the beam reflected and diffracted by the optical disk 4 incident on the hologram element 6 as shown in FIG.
Even if a signal can be detected, the wavefront reproduced from the hologram element 6 is as shown in FIG. Areas 642 and 643
can be obtained from respectively. By forming the non-hologram region 644 in the hologram element 6, even if the lens 8 moves and the beam aperture is restricted, offset is less likely to occur in the TE signal, making stable tracking control possible. Furthermore, no matter what position this hologram element is inserted in with respect to the reflected beam from the optical disk 4, a certain amount of the TE signal will be mixed into the FE signal, making it impossible to detect a stable FE signal. be.

It is also possible to form a diffraction grating that serves as a dummy in the non-hologram region 644 in order to keep the beam intensity distribution uniform - it is also possible to form a hologram element for detecting P, FE or TE signals. Same figure (b)
ζ An example of the pattern of the hologram element 6 produced by CGH is shown here. I will explain the detection method in detail.
FIG. 4 (See FIG. 4) Diffracted lights 8l to 8 detected in each photodetector area 501 to 508 of the photodetector unit 5 in the hybrid device shown in FIG. 2(b)
Figure 4 (
b) is a case where the beam 800 emitted from the light source 1 is focused on the optical disk 4, and FIGS. 4(a) and (C)
) indicate the defocus state at opposite phases, t. The FE signal is obtained, for example, by taking the differential outputs of photodetectors 502 and 505. This FE signal detection method is called spot size detection and is a well-known fact. Also, here, for example, the output of photodetector 502 is the output of 504, 506, and the output of 505 is 501.
, 503. On the other hand, the TE signal is increased by adding the outputs of the photodetectors 507 and 503.
It can also be obtained by taking the differential outputs of and 508.
The F4 word can be obtained by summing the outputs of photodetectors 501 to 508. Photodetectors 501 to 508
Diffracted light 8
If the angle between 1.82 and the light emitting point 10 of the light source 1 is designed to be relatively small, the diffracted lights 81 and 82 will move almost along the dividing line of the photodetector.Even if wavelength fluctuation occurs in the light source 1, a stable signal will be obtained. As long as the above-mentioned angle is approximately 30' or less, there is no problem in practice. It is possible to tolerate a large positional error when mounted in the package 2, for example, by setting the distance between the diffracted lights 81 and 82 on the photodetector unit 5 to 24.
Diffracted light on photodetector unit 5 to 0μ 8 1
．． If the angle between 82 and the light emitting point 10 of the light source is 17.1, it is possible to rotate the hologram element 6 even if there is a positional error of 200 μm when the light source 1 and photodetector unit 5 are mounted in the package 2. By,
The photodetector 5 is placed in a direction perpendicular to the dividing line of the photodetector unit, which is a problem in detecting the FE signal.
The residual position error from the center of 02 and 505 to the diffracted light 81.82 can be suppressed to a maximum of 4 μm.
Figure (a) i; L is a conceptual diagram showing another embodiment of the present invention; FIG.
Diffraction grating area 63 that can divide the wavefront for E signal detection
FE and TE signals can be detected by making the far-field patterns 411 and 412 of the beams reflected and diffracted by the disk from 1 and 632 incident on the hologram element 6l, as shown in FIG. This method of detecting the FE signal is a well-known fact called the double knife edge method.For example, in the hybrid device shown in FIG. 2(b), the photodetector unit 1l is used instead of the photodetector unit 5. , the hologram element 6 on the photodetector unit ll obtained when the hologram element 61 is used instead of the hologram element 6 in the optical pickup head device as shown in FIG. 1(a).
The diffracted lights 85 and 86 are reproduced from the functional areas 631 and 632 of the hologram element 6l.
can be obtained from respectively. Photodetector unit 1l
is composed of a plurality of photodetectors 509 to 512, and the FE signal is the difference between the output sum of photodetectors 509 and 512 and the output sum of photodetectors 510 and 511, and the TE signal is generated by the difference between the output sum of photodetectors 509 and 512.
Due to the differential between the output sum of and the output sum of photodetectors 511 and 512. The RF signal can be detected by summing the outputs of the photodetectors 509 to 512, but the pattern of the hologram element 61 is as follows.
The design may be such that the first-order diffracted light beams 85 and 86 from the photodetector unit l1 are each focused on the photodetector unit l1. The above-mentioned FE signal detection methods such as the spot size detection method and the double knife edge method (Table 1) are merely examples; of course, other FE signal detection methods such as the astigmatism method and the single knife edge method are also applicable to the present invention. Fig. 6(a) ft is a conceptual diagram of a hybrid device showing still another embodiment of the present invention. This is realized by replacing a certain photodetector unit 5 with a photodetector unit 12. Features of the photodetector unit l2 (i.e., in addition to a photodetector that receives the diffracted lights 81 to 84 from the hologram element 6, it also monitors the output of the light source) A photodetector 513 that receives light emitted from a surface facing the target light emitting point 10 of the light source 1 is formed on the same semiconductor substrate.

Photodetector 513 that receives light emitted from light source 1
The output of the light source is applied to a control circuit that keeps the output of the light source constant.Since the method of keeping the output of the light source constant is a well-known technique, the explanation is omitted here.
L RF signal or further laser output control signal
Since the detection can be performed using a photodetector formed on one substrate, the construction of the optical system is easy, and the number of parts and costs can be reduced. Figure 7 shows an optical pickup head showing yet another embodiment of the present invention. FIG. 2 is a conceptual diagram of the device. In the embodiment of the optical pickup head device shown in FIG. 1(a), a transmission type hologram element 6 is used, whereas in this embodiment, a reflection type hologram element 62 is used to bend the optical axis. Since the structure of this embodiment allows the thickness of the optical pickup head device to be reduced, the optical information device using the optical pickup head device according to the present invention can also be made thinner. In the optical pickup head device according to the present invention, the photodetector unit in the package housing the light source and the photodetector unit is placed closer to the bottom of the package than the light emitting point of the light source, so that the surface of the photodetector unit and the package are By arranging the upper part of the connection terminal on approximately the same plane and changing the arrangement of the photodetector unit by using a hologram element having a substantially concave lens function in the hologram region that generates the diffracted light used for detecting the focus error signal. (1) By arranging the photodetector unit 5 at the bottom of the package 2, the connection terminal 101 in the package 2 can be connected to the photodetector unit 5 while keeping the height of the connection terminal 101 low. It is possible to arrange the upper part of the terminal 101 on the same plane, and it is possible to keep the bonding wire short and stable.Also, since the bonding work can be performed by flat one-dimensional or two-dimensional movement, it is possible to If: When performing the bonding work while monitoring the surface of the photodetector unit 5 and the surface of the connection terminal 101 in the hybrid device with a TV camera, there is no need to adjust the focus of the TV camera at all during the bonding work, and as a result,
Not only does it significantly shorten the time required to fabricate a hybrid device, but it also allows for shorter and more stable bonding wires, which in turn makes it possible to narrow the spacing between the connecting terminals, making the optical pickup head device more compact. (2) By giving the hologram element 6 a concave lens effect, the magnification of the optical system increases, making it possible to detect good FE signals with high sensitivity. (3) FE signal and TE signal. Since the RF signal or even the laser output control signal can be detected with a photodetector formed on a single substrate, the optical system can be easily configured, reducing the number of parts and lowering the cost.

[Brief explanation of the drawing]

FIG. 1 shows a schematic structure of an optical pickup head device showing an embodiment of the present invention. FIG. Figure (b) shows the top surface of an hybrid device configuring the optical pickup head device shown in Figure 1.
FIG. 3(a) is a schematic diagram of the hologram element that constitutes the optical pickup head device shown in FIG. Figure 4 (a). (b). (c) The general principle explaining the signal detection method is shown in Figure 5(a).
is the structure of the hologram element explaining another embodiment or the same figure (
b) shows the relationship between the diffracted light and the photodetector in the optical pickup head device using the hologram element shown in FIG. Structure of an optical pickup head device explaining another embodiment of the present invention Part 8
The figure shows an example of a conventional optical pickup head device, and FIG. 9 shows the structure of a hybrid device constituting the optical pickup head device shown in FIG.
FIG. 2 is a side view of a hybrid device that uses the optical pickup head device shown in the figure. l... Semiconductor laser or equivalent coherent optical system 2-... Package, 3... Block 4...
Optical storage medium (optical disk), 5... Photodetector unit, 6... Hologram element, 8... Lens, 10... Light emitting element 20... Substrate, 21...
・Protection wL 12・ ・Photodetector unit,
61... Hologram element, 62... Hologram element, 81-84... 1st order diffracted light 411, 41
2...Far field pattern, 501-508
... Photo Detection Hisashi 641 ... Hologram Territory @
642-643... Diffraction grating, 644... Non-hologram region @ 800... Laser beam (0th order diffracted light).

Claims (5)

[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 from the light source and converges it into a minute spot on an optical storage medium;
An optical pickup head device comprising: a hologram element that receives a beam reflected by an optical storage medium and generates diffracted light; and a photodetector unit that receives the diffracted light from the hologram element and outputs a photocurrent. The photodetector units are housed in the same package, the package has an input/output terminal that allows the light source housed inside and the photodetector unit to be connected to an external circuit, and the photodetector units are formed on the same semiconductor substrate. The photodetector unit is composed of a plurality of photodetectors, and the photodetector unit is arranged at a position farther from the hologram element than a first surface including a light emitting point of the light source and perpendicular to the optical axis of the light source, and the hologram element 1. An optical pickup head device having a substantially concave lens function to enable detection of a focus error signal using a light receiving surface of the optical pickup head device. (2) The photodetector unit includes a photodetector unit that receives a beam emitted from a second emitting surface of the light source that is opposite to the first emitting surface of the light source that emits the beam from the light source onto the optical storage medium. An optical pickup head device according to claim 1, characterized in that the optical pickup head device comprises: (3) The optical pickup head device according to claim 1, wherein the hologram element is attached to a package. (4) The hologram element reproduces two diffracted lights having different focuses, and the focus of the diffracted lights is such that the size of the diffracted lights on the photodetector unit is substantially the same when the beam emitted from the light source is focused on the optical storage medium. The optical pickup head device according to claim 1, wherein the optical pickup head device is located in front and behind the surface of the photodetector unit so as to be equal to the surface of the photodetector unit. (5) Claim 1, characterized in that different diffraction grating holograms or non-hologram regions are formed spatially independently or in multiples in a part of the hologram element.
The optical pickup head device described in .