WO2006035345A1

WO2006035345A1 - Optical pickup unit with an optical base

Info

Publication number: WO2006035345A1
Application number: PCT/IB2005/053067
Authority: WO
Inventors: Fook W. Ho
Original assignee: Arima Devices Corporation
Priority date: 2004-09-28
Filing date: 2005-09-19
Publication date: 2006-04-06
Also published as: TW200627418A

Abstract

The invention relates to an optical pickup unit (2) comprising an optical base (10), an optical source (4) for generating an optical signal and one or more optical components (5) arranged on said optical base in optical communication with said optical source. The optical base (10) is made of steel and supports the optical source and the optical components. Steel is a low cost commodity material and accordingly, making the entire optical base of such a material provides for a cost advantage. Further, a steel optical base can be easily manufactured by stamping and bending steel plates. Finally, the steel optical base has an appropriate thermal conductivity to cope with the heat dissipation of the optical source when generating the optical signal. The invention further relates to an optical base (2), an optical device comprising such an optical base (2) and a method for manufacturing such an optical base.

Description

Optical pickup unit with an optical base

FIELD OF THE INVENTION

The invention relates to an optical pickup unit comprising an optical base, an optical source for generating an optical signal and one or more optical components arranged on said optical base in optical communication, i.e. relation, with said optical source.

BACKGROUND OF THE INVENTION

Optical disc drives are often installed in electronic devices such as personal computers. As recording media usable with the optical disk drives, compact discs and digital versatile discs are generally known. The optical disc drives have become commodity consumer goods in recent years. Conventionally, the material of the base or housing of an optical pickup unit of such an optical disc drive is made of plastic, such as polyphcnylenc sulphide (PPS) or liquid crystal polymer (LCP) resin. These materials provide adequate dimensional stability at the operating temperature of the optical pickup unit.

Moreover, optical pickup units with optical bases of different materials, such as zinc or magnesium, have been studied, as described in US-A2004/0008607. These materials were found to have various disadvantageous characteristics. Accordingly, US- A2004/0008607 proposes an optical pickup having an optical base made of different kinds of materials to combine the advantageous properties of the materials. Such an optical base is shown in Figs. 4 and 5. The optical pickup unit 100 has an iron optical base 101 for a laser diode and a photodiode mounted to said iron optical base 101 with fixing portions 102 respectively 103 bended from the optical base 101. The iron optical base 101 further comprises an opening to receive a component resin molded mounting portion 104 and resin sliding portions 105. The component resin molded mounting portion 104 has structures 106 to mount a diffraction grating, a beam splitter, a collimator lens etc. of the optical pickup. The prior art optical base for the optical pickup unit is disadvantageous in that it is complex to manufacture. Moreover, the required resins are relatively expensive due to the high demand for these materials. SUMMARY OF THE INVENTION

It is an object of the invention to provide an optical pickup unit with an optical base that is made of a low cost material and preferably decreases the complexity of the manufacturing process of the optical pickup unit. This object is achieved by providing an optical pickup unit with an optical base made of steel that supports said optical source and said optical components. Steel is a low cost commodity material and accordingly, designing the entire optical base of such a material provides for a cost advantage. Further, a steel optical base can be easily manufactured by stamping and bending steel plates. The tools employed in this manufacturing method are less expensive than the precision molds required for plastic optical bases. Finally, the steel optical base has an appropriate thermal conductivity to cope with the heat dissipation of the optical source when generating the optical signal.

The embodiment of the pickup unit according to the invention as defined in claim 2 has the advantage that the sliding elements can be integrally formed with the optical base. The sliding elements are preferably formed in the stamping process.

The embodiment of the pickup unit according to the invention as defined in claim 3 has the advantage that, by forming the mounting structures integrally from the base, e.g. by bending, no further mounting structures need to be applied and mounted to the substrate before providing the optical components. Moreover, the thus formed mounting structures provides for a very low failure rate of optical bases. Optical bases of plastic or comprising a resin portion according to the prior art are typically manufactured in batches. Accordingly, complete batches can fail to meet the accurate positioning requirements for the optical components. In contrast, the optical bases according to the invention have individually determined mounting structures for arranging the optical components. Preferably, the optical components are mounted according to the embodiment of claim 4. Providing glue on the mounting structure and/or the optical components enables accurate fixation of the optical source and the optical components on the optical base by a three-dimensional pick-and-place machine in the production line. Fixation of the optical source and the optical components by gluing further eliminates the need for a plasma cleaning process step that is conventionally applied to fixate these components to the optical base.

The embodiment as defined in claim 5 has the advantage that treating the optical base by e.g. galvanization extends the life time of the optical base. Such treatment may be any type of treatment including providing a coating or plating. Further, cold rolled steel is a steel type which is produced by a cold rolling process to yield an adequate surface quality, is thinner and also has good mechanical properties and excellent formability.

The embodiment as defined in claim 6 has the advantage that further integration for an optical device is obtained. It is noted that the above embodiments, or aspects thereof, may be combined.

The invention also relates to an optical base for use in an optical pickup unit as described above, wherein the optical base is a base of steel and wherein the optical base is adapted to support an optical source and one or more optical components. Accordingly, a low cost optical base is obtained. The invention also relates to an optical device for recording and retrieving information on respectively from a record medium comprising an optical pickup unit or an optical base as described above and an actuator device for moving the optical base. Such an optical device can be manufactured more easily and is cheaper. Preferably, one or more components of said actuator device arc arranged on one or more mounting structures and at least one of said mounting structures is an integral part of said optical base. As the optical base is moved along a spindle for recording and retrieving information from the record medium, it is advantageous to integrate the mounting structures for one or more components of the actuator device with the optical base.

The invention also relates to a method for manufacturing an optical pickup unit comprising the steps of:

- providing an optical base of steel;

- mounting an optical source for generating an optical signal on said steel optical base, and

- arranging one or more optical components on said optical base in optical communication with said optical source. As mentioned above, such an optical pickup unit is cheap, because of the steel material of the optical base, and can be easily shaped to mount the optical components and optical source for generating the optical signal.

Preferably, the optical components are arranged on said optical base by the embodiment of the method according to the invention as defined in claim 11. This method provides for accurate positioning of the components.

The embodiment as defined in claim 12 has the advantage that a simple method of manufacturing an optical base is obtained.

The invention will be further illustrated with reference to the attached drawings, which schematically show a preferred embodiment according to the invention. It will be understood that the invention is not in any way restricted to this specific and preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

Fig. 1 shows a schematic outline of the optical components of optical pickup unit;

Figs. 2 and 3 show a schematic illustration of an embodiment of an optical pickup unit with an optical base according to the invention, respectively in sectional view and in top view, and

Figs. 4 and 5 show perspective views of an optical base according to the prior art.

DETAILED DESCRIPTION OF THE DRAWINGS Fig. 1 depicts a schematic outline of an optical device 1 comprising an optical pickup unit (OPU) 2 and a disc drive (not shown) for a record medium 3. The record medium 3 is e.g. a compact disc (CD) or a digital versatile disc (DVD) from which data can be retrieved or whereon data can be recorded by employing the optical device 1.

The OPU 2 comprises an optical source 4, such as a laser diode, from which an optical signal S is generated. The optical signal S is directed by a folding mirror 5 and an objective lens 6 towards the record medium 3, i.e. the optical source 4 and the optical components 5 and 6 are arranged in optical communication with each other. A return signal from the record medium 3 follows the inverse route and is received at a photodiode 7 integrated in the optical source 4. Accordingly information can be recorded on or retrieved from the record medium 3 as generally known in the art.

Figs. 2 and 3 show a schematic illustration of an optical pickup unit 2 with an optical base 10 according to an embodiment of the invention. Fig. 2 is a sectional view of the optical base 10 with the optical components of Fig. 1. Fig. 3 is a top view of the optical base 10 with the optical components of Fig. 1. For reasons of clarity, details, such wire connections, generally known in the art are omitted.

The steel optical base 10 supports the laser diode 4 and the folding mirror 5. The optical base 10 has integral mounting structures 11 for carrying the folding mirror 5 and the objective lens 6. The mounting structures 11 are typically designed as L-bends 1 IA or form a different angle with the steel optical base 10, such as the mounting structure 1 IB for the folding mirror 5. The objective lens 6 is mounted by employing a lens holder element 12 attached to the mounting structure 1 IA via a connecting block 13. The optical base 10 has sliding elements or flanges 14, and a sliding element or z-bend 15 for sliding the optical base 10 along spindles 16 for moving the optical base 10 during operation of the optical recording device 1. The sliding elements 14, 15 are made of steel as well. Friction with the spindles 16 is reduced by providing smooth contact surfaces and eventually adding grease. Further mounting structures 11 C are present to integrate components, such as magnetic elements 17. The lens holder element 12 further supports magnetic coils 18 for the actuator to move the steel optical base 10 along the spindles 16.

The optical base 10 is steel plate shaped and structured by stamping and bending. The type of steel is e.g. G3141 -1977 according to the Japanese Industrial Standard (JIS).

Preferably the optical base 10 is corrosion resistant, e.g. by galvanizing the steel plate or e.g. coating the steel optical base 10 with zinc. Further chemical treatments arc contemplated, such as a chromate treatment for a zinc coated optical base 10 to prevent white rust from occurring at the steel optical base 10. The steel material of the optical base 10 has a considerably higher thermal conductivity, typically by a factor 50-250, than the conventional plastics used for the OPU housing. Accordingly, heat generated from the laser diode 4 is more easily removed from the OPU 2.

The mounting structures 11 are formed from the steel plate for the optical base 10 by stamping and bending of portions of such a plate. Stamping or press forming reduces the production cost compared to plastic injection process. Moreover, plastic formed housings need to go through a process of stress relief in the oven for a long time. For press formed optical bases 10, there is virtually no stress relief.

The laser diode 4 and the folding mirror 5 can be accurately positioned on the steel optical base 10 and/or the steel mounting structures 11 by a pick-and-place machine in the assembly line.

The pick-and-place machine positions the folding mirror 5 before gluing it on the mounting structures 11. Such pick-and-place machines are generally known in the art and have a high throughput. The laser diode 4 and the folding mirror 5 are glued either directly on the steel base 10 or the integral mounting structures 11, as indicated by reference numeral 19, such that the folding mirror 5 is in optical communication with the laser diode 4. The glue portions 19 can be dried with an ultraviolet curing method. It should be appreciated that the dimensions of the glue portions 19 have been exaggerated for clarity purposes. Similarly, the magnetic elements 17 can be positioned in this way. As all components can be accurately positioned on the steel optical base 10, only a small percentage of OPU bases will fail to meet the requirements for implementation in the optical device 1.

It should be acknowledged that the present invention is not limited to the above-described embodiment, since the OPU 2 may e.g. have further components, such as a beam splitter and a separate photodiode, attached to the steel optical base 10.

Claims

CLAIMS:

1. An optical pickup unit (2) comprising an optical base (10), an optical source (4) for generating an optical signal and one or more optical components (5) arranged on said optical base in optical relationship with said optical source, wherein said optical base (10) is made of steel and supports said optical source and at least one of said optical components.

2. The optical pickup unit (2) according to claim 1, wherein said optical base comprises one or more sliding elements (14,15) for moving said optical base along a spindle (16) and at least one of said sliding elements are made of steel.

3. The optical pickup unit (2) according to claim 1, wherein said optical base comprises one or more mounting structures (1 IA, 1 IB, 11C) for arranging at least one of said optical components on said optical base and at least one of said mounting structures is an integral part of said optical base.

4. The optical pickup unit (2) according to claim 3, wherein at least one of said optical components (5) is glue-mounted (19) on one of said mounting structures.

5. The optical pickup unit (2) according to claim 1, wherein said optical base is made of galvanized steel, such as cold rolled galvanized steel.

6. The optical pickup unit (2) according to claim 1, wherein said optical base comprises at least one actuator component (17,18).

7. An optical base (10) for use in an optical pickup unit according to claim 1, which optical base is adapted to support said optical source (4) and at least one of said optical components (5), wherein said optical base is made of steel.

8. An optical device (1) for recording and retrieving information on respectively from a record medium (3), comprising the optical base (10) according to claim 7 and the optical pickup unit according to any one of the claims 1 to 6 and further comprising an actuator device for moving the optical base.

9. The optical device (1) according to claim 8, wherein one or more components (17,18) of said actuator device are arranged on one or more mounting structures (HC) and wherein at least one of said mounting structures is an integral part of said optical base.

10. A method for manufacturing an optical pickup unit (2) comprising the steps of: - providing an optical base (10) of steel

- mounting an optical source (4) for generating an optical signal on said steel optical base, and

- arranging one or more optical components (5) on said optical base in optical relationship with said optical source.

1 1. The method of claim 10, wherein said optical components (5) are arranged on said optical base by positioning said components by a pick-and-place machine and gluing said optical components to said optical base.

12. The method of claim 10, wherein mounting structures (HA, 1 IB, 1 1C) are formed by stamping and bending said steel optical base (2).