WO2005091298A1

WO2005091298A1 - Optical recording device

Info

Publication number: WO2005091298A1
Application number: PCT/IB2005/050774
Authority: WO
Inventors: Herman P. Van Der Kall; Gerardus J. C. Van Miert
Original assignee: Koninklijke Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 2004-03-12
Filing date: 2005-03-02
Publication date: 2005-09-29
Anticipated expiration: 2006-09-12

Abstract

The invention relates to an optical recording device (1) for recording and retrieving information on respectively from a record medium (3) comprising a substantially closed housing (10) having an insertion opening for insertion and removal of said record medium (3). The device further comprises an optical pickup unit (4) inside said housing (10) for recording and retrieving said information on respectively from said record medium (3) and an substrate (7) outside said housing (10). The substrate (7) comprises control means (6) for controlling the device (1). Accordingly a simple and inexpensive construction is obtained that reduces heat transfer from the substrate (7) to the optical pickup unit (4).

Description

Optical recording device

The invention relates to an optical recording device for recording and retrieving information on respectively from a record medium.

An optical recording device generally comprises an optical pickup unit and a printed circuit board carrying electronic components. The temperature of such an optical recording device, in particular the optical pickup unit, may rise considerably during operation, especially if the recording device has a closed housing. This heating problem arises from power dissipation of components of the optical recording device, such as the optical pickup unit, in particular the laser and the laser driver, and the printed circuit board. Heating is especially disadvantageous for the laser of the optical recording device. JP-A 2000-182367 describes a device comprising a first mechanism for driving an optical head back and forth in a first direction and a second mechanism for moving a card-like record medium back and forth in a second direction, perpendicular to said first direction. The first and second mechanisms are contained in a base that, together with an electrical substrate is contained in a chassis. The walls of the base separate the first and second mechanisms from the electric substrate to reduce thermal or noise effects originating from the electrical substrate on the optical head. A problem of this recording device is the constructional complexity as a consequence of which manufacturing costs are relatively high.

Accordingly, it is an object of the invention to provide a less complex optical recording device adapted to reduce the heating problem. This object is achieved by providing the optical recording device as defined in

Claim 1. This device comprises: a substantially closed housing having an insertion opening for insertion and removal of said record medium; an optical pickup unit inside said housing for recording and retrieving said information on respectively from said record medium; a substrate outside said housing, said substrate comprising control means for controlling said device. The placement of the substrate, hereinafter also referred to as electrical substrate or printed circuit board (PCB), outside the housing of the optical recording device, allows reducing or even eliminating the thermal effect of the PCB on the interior of housing, or, more specifically, on the optical pickup unit, without the presence of separation walls inside the housing for this purpose. Instead, the walls of the housing itself separate the PCB and the optical pickup unit. It was found that the separation by the walls of the housing itself considerably reduced the temperature inside the housing. Surprisingly the placement of the PCB outside the housing was further found to have hardly any effect on the measured EMC (electromagnetic compatibility) performance of the recording device, i.e. the electromagnetic environment had hardly any effect on the performance of the recording device. Thus, the invention provides a simple and cost effective reduction of the heating problem. It is noted that the housing, although substantially closed, may have openings or holes for mounting and other recesses or slits, the latter e.g. arising from the fact that such housings are typically manufactured in mass production with low tolerance requirements. In a preferred embodiment of the invention the substantially closed housing is determined by a plurality of walls and said substrate is mounted to an outside of one of said walls. By mounting the PCB to the walls of the housing, the PCB can be positioned with the housing in e.g. a computer arrangement. The PCB may e.g. be mounted on a wall by screws applying spacers to hold said PCB on a predetermined distance of the housing. In a preferred embodiment of the invention the substantially closed housing is determined by a plurality of walls, at least one of said walls comprising one or more openings for electrical connection of said control means and said optical pickup unit. In this way the PCB outside the housing can still be used to control the components, such as the optical pickup unit, inside the housing. In a preferred embodiment of the invention, the insertion opening is adapted to comprise a tray for receiving a rotatable disc and/or a cartridge comprising such a disc as said record medium. This disc may e.g. be a digital versatile disc (DVD) and/or a blue ray disc (BRD). These types of disc require considerable signal processing on the PCB amounting to increased power dissipation. Accordingly a simple solution for the heating problem is especially advantageous for these types of optical recording devices. 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.

In the drawings: Fig. 1 shows the basic components of an optical recording device; Fig. 2 shows a schematical illustration of a rear view of an optical recording device according to an embodiment of the invention; Fig. 3 shows a schematical illustration of a front view of the optical device according to an embodiment of the invention, and Fig. 4 shows a schematical illustration of a bottom view of the optical device without a substrate.

Fig. 1 schematically illustrates an optical device 1 comprising an electric motor 2 for rotating a record medium 3 around an axis of rotation 2a and further comprising an optical pickup unit (OPU) 4. The OPU 4 typically comprises a laser, a detector and several lenses for appropriate guidance of the laser beam. The laser beam 5 is generated from the OPU 4 for recording information on and retrieving information from the record medium 3. The record medium 3 is provided with an information layer 3 a and may e.g. be a digital versatile disc (DVD) or a blue ray disc (BRD). The recording device 1 further comprises a control unit 6 controlling on the one hand the operation of the OPU 4, and controlling on the other hand the operation of the electric motor 2. The control unit 6 and other electrical components are typically provided on an electrical substrate 7, hereinafter also referred to as printed circuit board (PCB). During operation, the electric motor 2 is controlled to drive the optical disc 3 with a certain predetermined rotational speed. Conventionally said components are arranged within a housing 10. During operation, the temperature of the OPU 4 in the interior of the housing 10 rises. This temperature rise is e.g. caused by the power dissipation of the components on the PCB 7 as a result of signal processing. This temperature rise is especially disadvantageous for the laser of the OPU 4. The power dissipation may e.g. amount to 5 Watts giving rise to some 10 °C increase of the temperature of the OPU 4. As the housing 10 is generally substantially closed, heat cannot easily escape, which may eventually result in failure of the optical recording device 1. Figs. 2-4 show a schematical illustration of an optical recording device 1 according to an embodiment of the invention. The housing 10 is substantially closed and has an insertion opening 11 (see Fig. 3), displayed with a tray 12, for insertion and removal of the disc 3. Alternatively the insertion opening 11 is used for insertion of a cartridge containing an optical disc 3. The OPU 4 is provided inside the housing 10 for recording information on the disc 3. The PCB 7 comprises control means, such as the control unit 6, for controlling the optical recording device 1, e.g. the OPU 4 and the tray 12. The PCB 7 is provided outside the housing 10 and mounted to a wall 13 of the housing 10, in this embodiment the bottom wall 13. Spacers 14 are applied to maintain the PCB 7 at a predetermined distance from the housing 10. It is noted that the optical recording device may have an additional electrical substrate (not shown) within the housing 10 for e.g. control of the tray 12, external connectors for e.g. a headphone, volume control etc. However, such an additional electrical substrate does not contribute significantly to the heating of the device. Accordingly this low power dissipation electrical substrate may be positioned within the housing 10. Fig. 4 shows a bottom view of the optical recording device 1 without the PCB 7. A wall 13 of the housing 10 comprises openings or apertures 15 for electrical connection of the control unit 6 and the OPU 4. Accordingly signals can be transmitted between the PCB 7 when attached and the OPU 4, while they are physically separated by the bottom wall 13 of the housing 10. The below table provides information on the effect of the invention, wherein a comparison is made between the situation with a PCB 7 within the housing 10 and a situation with a PCB mounted on a wall 13 outside of the housing 10.

As the rotation of the disc 3 itself results in a cooling flow of air, measurements were performed for two constant rotational speeds of the disc 3. The same effect, i.e. the air flow resulting from the rotation of the disc 3, accounts for the fact that the temperature near the centre of the disc is higher than near the outer diameter R. It is noted that when a cartridge is used, the air cooling effect by rotation of the disc 3 is substantially eliminated. The temperature benefit by mounting the PCB 7 on the outside of the housing 10 is 5-9 °C. Accordingly the placement of the PCB 7 outside of the housing 10 has a considerable effect.

Claims

CLAIMS:

1. An optical recording device (1) for recording and retrieving information on respectively from a record medium (3) comprising: a substantially closed housing (10) having an insertion opening (11) for insertion and removal of said record medium (3); - an optical pickup unit (4) located inside said housing (10) for scanning an information layer (3a) of said record medium (3); a substrate (7) located outside said housing (10), which substrate (7) comprises a control means (6) for controlling said device (1).

2. The device (1) according to claim 1, wherein said housing (10) is determined by a plurality of walls (13) and said substrate (7) is mounted to one of said walls (13).

3. The device (1) according to claim 1, wherein said housing (10) is determined by a plurality of walls (13), at least one of said walls (13) comprising one or more apertures (15) for electrical connection of said control means (6) and said optical pickup unit (4).

4. The device (1) according to claim 1, wherein said insertion opening (11) is adapted to comprise a tray (12) for receiving a rotatable disc (3) and/or a cartridge comprising such a disc as said record medium (3).

5. The device (1) according to claim 1, which is suitable for recording information on a digital versatile disc (3) and/or a blue ray disc (3).