Optical head device and disk drive device

An optical head device may include a frame type of laser beam emitting element provided with a heat radiating fin on which a laser chip is mounted, a device frame on which the laser beam emitting element, a light receiving element and an optical system are mounted, and a heat radiation member formed of material having a superior heat conduction property. The upper face of the laser beam emitting element is fixed to the device frame, and an under face of the heat radiating fin which corresponds to a portion where the laser chip is mounted is exposed on an outer side to form an exposed part, and the heat radiation member is disposed to extend over the exposed part and the device frame. The device frame may include a first protective cover covering the optical disk side of the optical elements, and a second protective cover which covers the optical disk side of the objective lens drive mechanism and which is separately formed from the first protective cover and made of material having a superior heat conduction property, and a part of the second protective cover is extended to a laser driver IC, which is disposed to be exposed on the optical disk side, to form a heat radiation part where heat generated in the laser driver IC is radiated.

The present invention claims priority under 35 U.S.C. §119 to Japanese Application No. 2005-373736 filed Dec. 27, 2005 and Japanese Application No. 2005-373827 filed Dec. 27, 2005, both of which are incorporated herein by reference.

FIELD OF THE INVENTION

An embodiment of the present invention may relate to an optical head device which is used for recording or reproducing information into or from an optical disk such as a CD or a DVD. More specifically, an embodiment of the present invention may relate to a heat radiation structure for a frame type of laser beam emitting element provided in the optical head device and may relate to a heat radiation structure for a laser driver which drives a laser beam emitting element provided in the optical head device.

BACKGROUND OF THE INVENTION

A conventional optical head device which is used for reproducing information from an optical disk such as a CD or a DVD includes a laser beam emitting element, an objective lens drive mechanism which is provided with an objective lens for converging a laser beam emitted from the laser beam emitting element on an optical disk and is driven in a focusing direction and in a tracking direction, a light receiving element which receives a return light reflected by the optical disk, and parts for an optical system for guiding the laser beam between the laser beam emitting element and the light receiving element. These optical parts are mounted on a base.

As shown in Japanese Patent Laid-Open No. 2004-192720, a conventional frame type of laser beam emitting element 2 is held with a light emitting element holder 9 which is formed of a first holder member 91 and a second holder member 92 abutting with fins 24a,25afrom both sides to hold the laser beam emitting element 2 and is adhesively fixed to the base 10.

When the light emitting element holder 9 is to be adhesively fixed to the base 10, the position of an emitted light point of the laser beam emitting element 2 is required to be adjusted in a three-dimensional direction. Therefore, the light emitting element holder 9 and the base 10 are adhesively fixed to each other through a gap space in which the position of the emitted light point of the laser beam emitting element 2 can be adjusted in a three-dimensional direction.

With the speeding-up of disk dive device operation in recent years, the amount of heat generated in the laser beam emitting element 2 is also increased. In addition, with the miniaturization and thinning of an optical head device, since the light emitting element holder 9 of the laser beam emitting element 2 is downsized, heat radiation can not be sufficiently performed by only the heat radiating fins 24a,25a. In order to solve the problem, for example, it is conceivable that the light emitting element holder 9 is formed of material, which is excellent in heat conductive property, to radiate heat from the heat radiating fins 24a,25ato the light emitting element holder 9. However, with the miniaturization and thinning of an optical head device, since the light emitting element holder 9 is downsized, heat radiation can not be performed sufficiently even when such the light emitting element holder 9 is used. In the light emitting element holder 9 described in the above-mentioned patent reference, a gap space is provided between the light emitting element holder 9 and the base 10 so as to be capable of adjusting the position of the emitted light point of the laser beam emitting element 2 in a three-dimensional direction. Therefore, since heat radiation can not be sufficiently performed to the base 10 from the light emitting element holder 9, temperature of the laser beam emitting element 2 becomes higher and thus a service life time of the laser beam emitting element 2 maybe shortened.

Further, another conventional optical head device which is used for reproducing information from an optical disk such as a CD or a DVD includes an optical system having a laser beam emitting element as a light source, a laser driver integrated circuit (laser driver IC) for driving the laser beam emitting element, a frame on which the optical system is mounted, a cover fixed to a frame for protecting the optical system and the like.

In this optical head device, the cover for protecting the optical system is commonly formed of a metal plate made of stainless steel and heat generated in the laser driver is radiated through the cover. In other words, in a conventional optical head device, a cover which functions as a heat sink for a laser driver is used. A conventional structure of the optical head device will be described with reference toFIGS. 15 and 16.

As shown inFIG. 15, an optical head device101includes a laser beam emitting element102as a light source, a laser driver IC104mounted on a circuit103for driving the laser beam emitting element102, and a frame105on which an optical system including the laser beam emitting element102is mounted. Further, as shown inFIG. 16, a cover106formed of a stainless-steel plate is fixed to the frame105with a mounting screw108to protect the optical system.

As shown inFIG. 16, the cover106is fixed so as to cover almost the whole portion of a bottom face side of the frame105, and optical elements structuring the optical system is covered by the cover106. The cover106contacts with the laser driver IC104through a heat transmission sheet (not shown) which is provided with heat transmission property and elasticity. Therefore, heat generated in the laser driver IC104is radiated to the frame105through the heat transmission sheet and thus the cover106functions as a heat sink for the laser driver IC104.

A method for positively radiating heat generated in the laser driver IC is disclosed in Japanese Patent Laid-Open No. 2004-192751, in which a laser driver IC is disposed on an optical disk side and air is circulated by rotation of the optical disk to radiate the heat generated in the laser driver IC to the air through a heat radiation member.

When the conventional optical head device101is structured as shown inFIG. 16, since the cover106functions as a heat sink for the laser driver IC104, temperature of the cover106rises with rising of the temperature of the laser driver IC104. The cover106covers almost the whole portion on the bottom face side of the frame105on which the optical system is mounted and thus the temperature of the whole frame105also rises with rising of the temperature of the cover106. Further, with rising of the temperature of the cover106, temperature of the optical elements which are covered by the cover106also rises.

With higher-density recording and speeding-up for an optical disk in recent years, the amount of heat generated in the laser driver IC104which drives the laser beam emitting element is increased. On the other hand, with the miniaturization and thinning of an optical head device, the heat sink is also downsized. Therefore, the temperature of the whole frame105rises and the temperature of the optical elements covered by the cover106becomes higher and thus optical characteristics of the optical head device101are affected. In other words, fixed positions of the optical elements structuring the optical system are displaced by temperature rising of the frame105and thus optical characteristics of the optical head device101are affected.

Further, in the latter patent reference, adverse effects to the optical elements may be avoided by a laser driver IC which is arranged on an optical disk side and heat is radiated through a heat radiation member which is a different member from the cover. However, in this patent reference, the heat radiation member which is provided with both arm portions facing each other in a jitter direction is formed in a U-shape so as to avoid an actuator (objective lens drive mechanism). Therefore, although its outer shape is large, a sufficient heat radiation area is not obtained and thus heat radiation effect is not satisfactory. Further, a dedicated heat radiation member for the laser driver IC is required separately and thus the number of parts is increased. In addition, in a thin-type of optical head device used in a notebook-sized personal computer or the like, the heat radiation member is not exposed from an opening of a tray on which an optical disk is placed and thus cooling effect is not sufficient.

SUMMARY OF THE INVENTION

In view of the problems described above, an embodiment of the present invention may advantageously provide an optical head device in which a sufficient heat radiation effect is obtained in a frame type of laser beam emitting element even when the size of its heat radiating fin is reduced.

In view of the problems described above, another embodiment of the present invention may advantageously provide an optical head device which is capable of preventing positional displacement of an optical element due to heat generated in a laser driver IC to restrain effects to an optical characteristic and, in which a sufficient heat radiation effect is obtained even when the size of its heat radiating fin is reduced, and may advantageously provide a disk drive device on which the optical head device is mounted.

Thus, according to an embodiment of the present invention, there may be provided an optical head device including a frame type of laser beam emitting element which is provided with a heat radiating fin on which a laser chip is mounted, a light receiving element for signal detection, an optical system which structures an optical path from the light beam emitting element to an optical disk and an optical path from the optical disk to the light receiving element, a device frame on which the laser beam emitting element, the light receiving element and the optical system are mounted, and a heat radiation member which is formed of material having a superior heat conduction property. In this optical head device, when a side of the laser beam emitting element on which the laser chip is mounted is set to be an upper face side, the upper face side of the laser beam emitting element is fixed to the device frame, and an under face of the heat radiating fin which corresponds to a portion where the laser chip of the laser beam emitting element is mounted is exposed on an outer side to form an exposed part, and the heat radiation member is disposed to extend over the exposed part of the heat radiating fin and the device frame.

In accordance with an embodiment, in a frame type of laser beam emitting element, when a side of the laser beam emitting element on which the laser chip is mounted is set to be an upper face side, the upper face side of the laser beam emitting element is fixed to the device frame, and the under face of the heat radiating fin which corresponds to a portion where the laser chip of the laser beam emitting element is mounted is exposed on an outer side to form an exposed part, and the heat radiation member which is formed of material having a superior heat conduction property is disposed to extend over the exposed part the heat radiating fin and the device frame. Therefore, heat radiated from the under face of the heat radiation fin corresponding to the portion where the laser chip is mounted, in other words, heat radiated from the vicinity of the laser chip which is a heat generating source, is efficiently transmitted to the device frame through the heat radiation member. Therefore, even when the heat radiating fin is downsized, since a sufficient heat radiation effect is obtained, a service life time of the laser beam emitting element can be extended.

In accordance with an embodiment, the heat radiation member is a metal plate which includes three projecting parts formed in a substantially parallel to each other to be formed in an E-shape in a planar view. Especially, it is preferable that the laser beam emitting element is provided with both end parts of the heat radiating fin which are exposed on an outer side from molded resin in which the laser tip is accommodated, and two projecting parts formed on both sides of a center projecting part of the tree projecting parts of the metal plate are adjacently disposed on an outer side of the both end parts of the heat radiating fin. According to the structure as described above, the projecting parts which are formed on both sides of a central projecting part of the metal plate are disposed so as to extend along the both end parts of the heat radiating fin and thus the projecting parts which are formed on both sides of the center projecting part of the metal plate can be enlarged while taking its space efficiency into consideration. Therefore, heat radiated from the heat radiating fin to the center projecting part can be efficiently transmitted from the projecting parts formed on both sides of the center projecting part to the device frame without causing the optical head device to enlarge.

In accordance with an embodiment, the laser beam emitting element includes both end parts of the heat radiating fin which are exposed on an outer side from molded resin in which the laser chip is accommodated, and the both end parts are directly fixed to the device frame. According to the structure as descried above, heat is efficiently radiated from both the end parts of the heat radiating fin to the device frame.

In accordance with an embodiment, the device frame includes a mainframe which is formed of a frame-shaped member made of resin and in which bearings are formed on both end portions of the mainframe, and a subframe made of metal which is disposed on an inner side of the mainframe and on which the light emitting element is mounted, and a connecting part for connecting with the mainframe is formed at an end part of the subframe and the light emitting element is mounted near the connecting part. According to the structure as described above, the subframe has a high heat transmission property and the mainframe is inexpensive. Therefore, according to this embodiment, cost and weight of the device frame can be reduced and heat generated in the light emitting element is efficiently transmitted and radiated to the mainframe through the subframe.

In accordance with an embodiment, the subframe is provided with an elongated opening in which an optical element structuring the optical system is accommodated ahead in an emitting direction of the laser beam emitting element, the elongated opening is formed with a depth which enables the entire of the optical element to be sufficiently accommodated, and a pair of wall parts which are formed in an separated manner each other in the emitting direction of the laser beam emitting element so as to form the elongated opening, and the optical element is fixed to a forward wall part of a pair of the wall parts in the emitting direction of the light emitting element. According to the structure as described above, for example, a rearward wall part of a pair of the wall parts in the emitting direction of the light emitting element can be separated from the optical element and thus the optical element can be further separated from the light emitting element and thus an adverse effect to the optical element due to heat generated in the laser beam emitting element can be suppressed.

Further, according to an embodiment of the present invention, there may be provided an optical head device including a light emitting element, a light receiving element for signal detection, optical elements which structure an optical path from the light beam emitting element to an optical disk and an optical path from the optical disk to the light receiving element, an objective lens drive mechanism for driving an objective lens as one of the optical elements, a laser driver IC for driving the light emitting element, and a device frame on which the laser driver IC, the light emitting element, the optical elements and the objective lens drive mechanism are mounted. The device frame includes a protective cover for protecting an optical disk side of the optical elements and the objective lens drive mechanism. The protective cover includes a first protective cover which covers the optical disk side of the optical elements, and a second protective cover which covers the optical disk side of the objective lens drive mechanism and which is separately formed from the first protective cover and made of material having a superior heat conduction property. In addition, a part of the second protective cover is extended to the laser driver IC, which is disposed to be exposed on the optical disk side, to form a heat radiation part where heat generated in the laser driver IC can be radiated.

In accordance with an embodiment, the second protective cover which is provided with the heat radiation part where heat generated in the laser driver IC can be radiated is separately formed from the first protective cover which covers the optical disk side of the optical elements. Therefore, heat generated in the laser driver is not transmitted to the first protective cover. Accordingly, positional displacement of the optical elements, which are covered with the first protective cover, due to heat generated in the laser driver is prevented and effect to an optical characteristic can be restrained. Further, the second protective cover is formed of material having a superior heat conduction property and disposed on the optical disk side and thus heat radiation efficiency can be improved by utilizing circulation of air according to rotation of the optical disk. Therefore, a sufficient heat radiation effect can be obtained even when the second protective cover is small.

In accordance with an embodiment, the device frame includes a mainframe which is formed of a frame-shaped member made of resin and in which bearings are formed on both end portions of the mainframe, and a subframe made of metal which is disposed on an inner side of the mainframe and on which at least a part of the light emitting element, the light receiving element for signal detection and the optical elements is mounted. According to the structure as described above, the subframe has a high heat transmission property and the mainframe is inexpensive. Therefore, according to this embodiment, cost and weight of the device frame can be reduced and heat generated in the light emitting element is efficiently transmitted and radiated to the cover members and the like through the subframe.

In accordance with an embodiment, an opposite side of the second protective cover to the objective lens drive mechanism with respect to the laser driver IC is fixed to the device frame and an opposite side of the second protective cover to the laser driver IC with respect to the objective lens drive mechanism is fixed to the device frame. Especially, it is preferable that the second protective cover is provided at the opposite side to the objective lens drive mechanism with respect to the laser driver IC with an extended part which is extended to an under face side of the device frame when the optical disk side of the device frame is set to be an upper face side of the device frame. According to the structure as described above, heat generated from the laser driver IC is capable of being transmitted to the device frame through the second protective cover in a balanced manner and thus heat radiation efficiency from the device frame can be improved.

In accordance with an embodiment, the objective lens drive mechanism and the laser driver IC are closely disposed each other in a radial direction of the optical disk, and the laser driver IC is disposed on an outer side of the objective lens drive mechanism in the radial direction. A rotational speed on an outer side of an optical disk is higher than that on an inner side in a radial direction and thus circulation efficiency of air is also large on its outer side. According to the structure as described above, the laser driver IC is disposed on an outer side in the radial direction of the optical disk and thus heat radiation efficiency can be improved by air cooling.

In accordance with an embodiment, the second protective cover is a metal plate which is made of copper, aluminum or stainless steel.

Further, according to an embodiment of the present invention, there may be provided a disk drive device on which the above-mentioned optical head device is mounted and which is provided with a tray on which the optical disk is placed. The tray is provided with an opening part which is opened along a movable direction of the optical head device for exposing the objective lens so as to face the optical disk and the second protective cover is exposed from the opening part so as to face the optical disk. According to the structure as described above, the second protective cover is exposed through the opening of the tray on which an optical disk is placed and flow of air is not disturbed by the tray and thus heat in the second protective cover is radiated by circulation of air. Therefore, heat radiation effect can be further improved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An optical head device in accordance with an embodiment of the present invention will be described below with reference to the accompanying drawings. In this specification, a side on which an objective lens is viewed is defined as an upper face side and the opposite side is defined as an under face side.

FIG. 1is a plan view showing an optical head device in accordance with an embodiment of the present invention.FIG. 2(a) is a plan view showing an enlarged main body portion of the optical head device shown inFIG. 1in which a flexible circuit board is not shown,FIG. 2(b) is its bottom view,FIG. 2(c) is its left side view,FIG. 2(d) is its right side view, andFIG. 2(e) is an “O-O” cross-sectional view inFIG. 2(b).FIG. 3(a) is a plan view showing a state in which an upper cover, an under cover and an actuator cover are detached from the main body portion of the optical head device shown inFIG. 1andFIG. 3(b) is its bottom view.FIG. 4(a) is a plan view showing a state in which a flexible circuit board and an objective lens drive device are detached from the state shown inFIGS. 3(a) and3(b),FIG. 4(b) is its bottom view,FIG. 4(c) is its left side view,FIG. 4(d) is its right side view, andFIG. 4(e) is an “N-N” cross-sectional view inFIG. 4(a).FIG. 5(a) is a plan view showing a subframe shown inFIG. 4(a),FIG. 5(b) is a bottom view showing the subframe shown inFIG. 4(b),FIG. 5(c) is a “P-P” cross-sectional view inFIG. 5(b) andFIG. 5(d) is a “Q-Q” cross-sectional view inFIG. 5(b).FIG. 6(a) is a plan view showing a state in which a metal member is detached from the subframe shown inFIG. 5(b) andFIG. 6(b) is a “J-J” cross-sectional view inFIG. 6(a).

As shown inFIG. 1andFIGS. 2(a) through2(d), an optical head device1in accordance with an embodiment of the present invention is provided with a first bearing part211and a second bearing part212formed on both ends of a device frame2for engaging with a feed screw shaft and a guide shaft of the disk drive device to drive in a radial direct of an optical disk. A side face on one side of the device frame2is curved in a circular arc shape in order to prevent interference when the device frame2approaches to a spindle motor240(seeFIG. 13)in a disk drive.

An objective lens91is located at a substantially center portion on the upper face side of the device frame2and an upper cover6formed of a thin metal plate is placed on the first bearing part211side to the objective lens91. The upper cover6includes an upper plate part61covering an upper face of the device frame2, a first side plate part62which is bent downward from one of side edge portions of the upper plate part61to engage with a projection formed on a side face of the device frame2, and a second side plate part63which is bent downward from the other of the side edge portions of the upper plate part61to engage with a projection formed on a side face of the device frame2.

An under cover8formed of a thin metal plate is put on a bottom face of the device frame2. The under cover8includes an under plate part81covering the under face of the device frame2, first side plate parts82which are bent upward from one of side edge portions of the under plate part81to engage with a projection formed on a side face of the device frame2, and a second side plate part83which is bent upward from the other of the side edge portions of the under plate part81to fit into a slit of the device frame2so as to apply an elastic force maintaining a state where the under cover8is mounted on the device frame2.

An actuator cover7as a second protective cover, which is formed of a thin metal plate and will be described below with reference toFIG. 11andFIGS. 12(a) through12(d), is placed on a left side portion of the device frame2where the second bearing part212is located with respect to the objective lens91. In this embodiment, a dustproof cover for covering the upper face side, i.e., the optical disk side of the device frame2is with the actuator cover7and the upper cover6.

As shown inFIGS. 3(a) and3(b), a main body portion of the flexible circuit board3shown inFIG. 1is disposed to cover the upper face of the device frame2on a lower side of the actuator cover7and the upper cover6. A laser driver IC30for driving a twin laser light source4which will be described below is mounted on an under face of the flexible circuit board3. Two end parts31,32are extended from the main body portion of the flexible circuit board3toward the first bearing part211side from the upper cover6side. The wiring patterns formed on the end parts31,32are electrically connected to a light receiving element55for signal detection which will be described below. In addition, the flexible circuit board3is provided with end parts33,34and the wiring patterns formed on the end parts33,34are electrically connected to the twin laser light source4and a light receiving element56for front monitor which will be described below.

The device frame2includes a mainframe21which will be described below with reference toFIG. 7andFIGS. 8(a) through8(e) and a metal subframe22made of metal which will be described below with reference toFIGS. 9(a),9(b) andFIGS. 10(a) through10(e). The subframe22is held in the mainframe21in a state that the subframe22is disposed in the inner side of the mainframe21.

As shown inFIGS. 3(a),3(b) throughFIGS. 6(a),6(b), the optical head device1is a two-wavelength optical head device1which is capable of recording and reproducing information into or from a DVD disk and a CD disk by using a first laser beam (red light) with a wavelength of 650 nm band and a second laser beam (infrared light) with a wavelength of 780 nm band. The twin laser light source4, which is integrally provided with an AlGaInp-based laser diode emitting the first laser beam and an AlGaAs-based laser diode emitting the second laser beam, is mounted on the device frame2. In accordance with an embodiment, the first laser beam or the second laser beam is guided to a DVD disk or a CD disk which is an optical disk300through a common optical system comprising of a plurality of optical elements which are disposed on an optical path directing to the optical disk from the twin laser light source4. The optical elements structuring the optical system are also mounted on the device frame2. Further, a return light beam from the optical disk300is guided to the common light receiving element55for signal detection through the common optical system, and optical elements for forming an optical path for the light beam and the light receiving element55for signal detection are also mounted on the device frame2.

In the optical head device1in accordance with this embodiment, the common optical system includes a diffraction element51for diffracting the first and second laser beams emitted from the twin laser light source4into three beams for tracking detection, a half mirror52partly reflecting the laser beams which are divided into three beams through the diffraction element51, a collimating lens53for forming the laser beam from the half mirror52in a parallel light, a directing mirror59for directing the parallel light to the optical disk300, and an objective lens91for converging the laser beam from the directing mirror59on a recording face of the optical disk300as the optical elements. The common optical system also includes a sensor lens54as an optical element for applying astigmatism to the return light beam of the first and the second laser beams passing through the collimating lens53and the half mirror52after reflected by the recording face of the optical disk300. The light receiving element56for front monitor is disposed on an opposite side of the diffraction element51with respect to the half mirror52.

The objective lens91is arranged such that its position in a tracking direction and a focusing direction is servo-controlled by the objective lens drive mechanism9. The objective lens drive mechanism9is also mounted on the device frame2. In accordance with this embodiment, a wire suspension type is used for the objective lens drive mechanism9. A well-known objective lens drive mechanism may be used for the objective lens drive mechanism9and thus its detailed description is omitted. In accordance with this embodiment, the objective lens drive mechanism9includes a lens holder holding the objective lens91, a holder support portion which movably supports the lens holder with a plurality of wires in the tracking direction and the focusing direction, and a yoke which is fixed to the device frame2. Further, the objective lens drive mechanism9is provided with a magnetic drive circuit which is structured of drive coils attached to the lens holder and drive magnets attached to the yoke. The objective lens91which is held on the lens holder is driven in the tracking direction and the focusing direction on to the optical disk by controlling energization to the drive coils. Tilt control for adjusting a tilt of the objective lens91in a jitter direction may be performed in the objective lens mechanism9.

In the optical head device1structured as described above, the first and the second laser beams which are emitted from the twin laser light source4, after having transmitted through the diffraction element51, are partly reflected by a partial reflection face of the half mirror52such that its optical axis is bent at 90 degrees to be directed to the collimating lens53. The optical axis of the laser beam which is formed in a parallel light through the collimating lens53is bent at 90 degrees by the directing mirror59and the laser beam is directed to the objective lens91. On the other hand, another part of the first and the second laser beams emitted from the twin laser light source4transmits through the partial reflection face of the half mirror52to be guided to the light receiving element56for front monitor as a monitor light beam. Monitoring result in the light receiving element56for front monitor is fed back to the twin laser light source4through the laser driver IC to cause an intensity of the laser beam emitted from the twin laser light source4to be controlled.

The return light beam from the optical disk300returns to the objective lens91and the directing mirror59in a reverse direction and is emitted to the sensor lens54through the collimating lens53and the half mirror52. After astigmatism is generated through the sensor lens54, the return light beam is incident on the light receiving element55for signal detection to detect a signal in the light receiving element55. Three beams of the first and the second laser beams diffracted through the diffraction element51are included in the return light beam which is detected with the light receiving element55for signal detection. For example, reproduction of signal is performed by using a main beam comprised of a zero-order light beam among three beams, and a tracking error signal and a focusing error signal for the objective lens91are detected by using detection results of sub-beams comprised of +−1st-order light beams. In this manner, the laser driver IC controls the objective lens drive mechanism9on the basis of detection results of the tracking error signal and the focusing error signal.

In accordance with the embodiment described above, since recording and reproduction are performed by using the first laser beam and the second laser beam through the common objective lens91, a two-wavelength lens on which diffraction grating is formed with concentric circular grooves or steps is used as the objective lens91. Therefore, according to this embodiment, even when the objective lens91is commonly used, both the first laser beam and the second laser beam are applicable to optical disks300which are provided with recording layers whose surface protective layers are set to be different thicknesses.

FIG. 7is a perspective view showing a mainframe used in the optical head device shown inFIG. 1.FIG. 8(a) is a plan view showing the mainframe shown inFIG. 7,FIG. 8(b) is its bottom view,FIG. 8(c) is its left side view,FIG. 8(d) is its right side view, andFIG. 8(e) is a “M-M” cross-sectional view inFIG. 8(a).FIG. 9(a) is a perspective view showing the subframe used in the optical head device shown inFIG. 1that is viewed obliquely from above, andFIG. 9(b) is a perspective view showing the subframe that is viewed obliquely from below.FIG. 10(a) is a plan view showing the subframe shown inFIGS. 9(a) and9(b),FIG. 10(b) is its bottom view,FIG. 10(c) is its front view,FIG. 10(d) is its left side view andFIG. 10(e) is its right side view.

In the optical head device1in accordance with an embodiment, the device frame2includes a mainframe21comprised of a frame-shaped part made of resin which contains heat-conductive fillers as shown inFIG. 7andFIGS. 8(a) through8(e) and a subframe22made of metal as shown inFIGS. 9(a),9(b) andFIGS. 10(a) through10(e). As shown inFIGS. 2(a) through2(e) andFIG. 4(a) through4(e), the subframe22is held to the mainframe21in a state that the subframe22is disposed in a subframe mounting region210on an inner side of the mainframe21. As shown inFIG. 7andFIG. 8(a) through8(e), the first bearing part211, the second bearing part212and the like are formed in the mainframe21. The subframe22shown inFIGS. 9(a),9(b) andFIGS. 10(a) through10(e) is, for example, a die casting product made of zinc alloy. As shown inFIG. 3(a) and3(b), in the state that the subframe22is mounted on the mainframe21, the inside of the device frame2is sectioned into a first optical element setting portion on which the subframe22is disposed and a second optical element setting portion on which the subframe22is not disposed.

In other words, in this embodiment, the twin laser light source4, the diffraction element51, the half mirror52, the collimating lens53, the sensor lens54, the light receiving element55for signal detection and the light receiving element56for monitor are mounted on the subframe22and then the subframe22is mounted on the mainframe21. On the other hand, the directing mirror59is directly mounted on the mainframe21. Further, the objective lens drive mechanism9for driving the objective lens91is mounted on the mainframe21through the yoke which is fixed to the mainframe21.

The structures of the respective parts which are used in the optical head device1will be described below in detail. The mainframe21shown inFIG. 7andFIGS. 8(a) through8(e) is provided with the first bearing part211and the second bearing part212at its both end portions. The subframe mounting region210is formed in the inside of the mainframe21on the first bearing part211side from the center in its longitudinal direction.

Two portions of the mainframe21interposing the subframe mounting region210are formed in a first subframe connecting region213and a second subframe connecting region214which are respectively provided with positioning projections218,219for positioning the subframe22. The first subframe connecting region213is formed as a portion which is bent and extended from an end part of an oblique side part adjacent to an end part region215on the side of the first bearing part211. On the other hand, the second subframe connecting region214is formed in a portion between the end part of the end part region215and a circular arc-shaped curved portion.

In this embodiment, as shown inFIG. 7andFIG. 8(a), the width dimension “W11” of the first subframe connecting region213and the width dimension “W12” of the second subframe connecting region214are set to be larger tan the width dimension “W21” of the end part region215. In other words, the width dimension of the entire first subframe connecting region213is set to be larger than that of the end part region215. Further, a region of the second subframe connecting region214which is close to the end part region215is set to have the width dimension substantially equal to that of the first subframe connecting region213and thus wider than the end part region215.

Further, both thickness dimensions of the first subframe connecting region213and the second subframe connecting region214are set to be thinner than that of the end part region215and they are formed lower than the end part region215. Therefore, in the mainframe21, step portions corresponding to differences of these thicknesses are formed on an upper face of a boundary region216between the first subframe connecting region213and the end part region215and on an upper face of a boundary region217between the second subframe connecting region214and the end part region215. In this embodiment, the upper faces of two boundary regions216,217are formed in an inclined face where thickness dimension is gradually decreased from the end part region215to the first subframe connecting region213and to the second subframe connecting region214.

As shown inFIGS. 9(a),9(b) andFIGS. 10(a) through10(e), the subframe22is formed in a roughly rectangular planar shape. Its upper face is formed in a totally flat face, and ribs and projections/recesses for positioning the respective optical elements are formed on its under surface. In the subframe22, a first connecting part221and a second connecting part222are extended in a thin plate shape to both right and left sides from the upper face. An elongated hole223to which a positioning projection218of the mainframe21is fitted is formed in the first connecting part221as a through hole. A circular hole224to which a positioning projection219of the mainframe21is fitted is formed in the second connecting part222as a through hole.

In order to mount the subframe22onto main frame21, in a state that the subframe22is disposed in the subframe mounting region210of the main frame21, the first connecting part221is put on the first subframe connecting region213of the main frame21and the second connecting part222is put on the second subframe connecting region214of the main frame21. As a result, the positioning projections218,219of the main frame21are respectively fitted into the elongated hole223of the first connecting part221and the circular hole224of the second connecting part222to perform positioning of the subframe22. In this state, an outer end portion of the first subframe connecting region213and an outer end portion of the second subframe connecting region214are protruded outside from an edge portion of the first connecting part221and an edge portion of the second connecting part222. Therefore, stepped parts228,229are formed in the first subframe connecting region213and the second subframe connecting region214by using the edge portion of to first connecting part221and the edge portion of the second connecting part222. Therefore, when an ultraviolet (UV) curing type of adhesive is coated on the stepped parts228,229and then the adhesive is hardened by ultraviolet irradiation, the first connecting part221and the second connecting part222are adhesively fixed to the first subframe connecting region213and the second subframe connecting region214. In this case, the adhesive enters into a gap space between the first subframe connecting region213and the first connecting part221and a gap space between the second subframe connecting region214and the second connecting part222. Therefore, the first subframe connecting region213and the second subframe connecting region214are face-bonded with the first connecting part221and the second connecting part222. In this embodiment, the face bonding portions formed as described above are referred to as connecting parts between the mainframe21and the subframe22.

InFIGS. 3(a) through6(b), the half mirror52is adhesively fixed to a center region of the subframe22and the diffraction element51is mounted at a side position of the half mirror52. The diffraction element51is fixed with a flat spring510.

The twin laser light source4is disposed at a side position of the diffraction on element51in the subframe22. In accordance with an embodiment, the twin laser light source4is not a can type in which a laser chip41is accommodated in a cylindrical case, but is a frame type of laser light source in which a submount43on which a laser chip41is mounted is mounted on an upper face of a heat radiating fin44. Both end portions of the heat radiating fin44are fixed to the subframe22with an adhesive130. The twin laser light source4is structured such that the heat radiating fin44is molded in a rectangular shape with a resin portion45which surrounds the sub-mount43on which the laser chip41is mounted.

The subframe22is formed with stepped parts226to which a part of the heat radiating fin44of the twin laser light source4is fitted and a groove part227which accommodates the resin portion45in a non-contact state. An upper face on which the laser chip41of the twin laser light source4is mounted is directed to an upper face of the optical head device1, and the upper faces of the heat radiating fins44are abutted with and mounted on the stepped parts226of the subframe22and, in this manner, the positioning in a vertical direction of the twin laser light source4is performed. The optical axis of the twin laser light source4is adjusted under a state that the upper faces of the heat radiating fins44are abutted with the stepped parts226of the subframe22, and then the twin laser light source4is adhesively fixed with a UV adhesive130. Further, a stepped length of the stepped part226is formed in the same thickness as that of the heat radiating fin44. Therefore, when the twin laser light source4is mounted on the subframe22as described above, an under face of the heat radiating fin44becomes the same height as the under face228of the subframe22.

As shown inFIG. 5(b), a metal member12which is formed in an E-shape in a plan view is adhesively fixed to the subframe22at a front position of the twin laser light source4by using a UV adhesive141. A center projecting part122of three projecting parts121,122,123of the metal member12is disposed on an under face of the heat radiating fin44at a position corresponding to the rear face side of a portion where the laser chip41and the submount43are mounted. In other words, an exposed part46is formed by exposing the under face of the heat radiating fin44, which corresponds to a portion on which the laser chip41of the twin laser light source4is mounted, to the outside, and the center projecting part122is disposed in the exposed part46.

The both side projecting parts121,123are respectively disposed on an under face228of the subframe22so as to be adjacently provided on outer sides of both end portions of the heat radiating fin44. In order to adhesively fix the metal member12to the subframe22, as shown inFIG. 6(a), a gel comprised of material superior to heat conductive property is coated to three spots140of the subframe22where the metal member12is to be disposed and, after that, the metal member12is mounted on the subframe22and adhesively fixed at two spots shown inFIG. 5(b) with the UV adhesive141. When the metal member12is mounted on the subframe22, the gel is squeezed by the metal member12that is filled between the metal member12and the subframe22without a gap space.

In this embodiment, as described above, the under face of the heat radiating fin44is set to be the same height as the under face228of the subframe22. Therefore, all the opposite faces of the three projecting parts121,122,123of the metal member12facing the heat radiating fin44and the under face228of the subframe22are formed in the same plane and thus the metal member12is formed in a simple E-shape in a plan view.

As shown inFIGS. 5(a) and6(a), an elongated opening225, which is formed to extend on a front side of the projecting parts121,123of the metal member12and in which the diffraction element51is accommodated, is formed at a front position of the twin laser light source4. The elongated opening225are provided with wall parts225aand225b, which are perpendicular to the optical axis of the emitted light beam of the twin laser light source4and face each other, and the elongated opening225is formed in a depth so as to sufficiently accommodate the entire of the diffraction element51. The wall part225aon a rear side in the emitting direction of the twin laser light source4is disposed on the side where the twin laser light source4is mounted. The diffraction element51is fixed to the wall part225bon the front side in the emitting direction of the twin laser light source4, which faces the wall part225a, with a flat spring510and an adhesive (not shown) as shown inFIGS. 5(b) through5(d). Since a little gap space is formed between the wall part225aand the diffraction element51, effect to the diffraction element51due to heat generated in the twin laser light source4is suppressed.

A lead pin42extending backward of the twin laser light source4which is mounted on the subframe22is mounted on a light source mounting board40and three lead wires11are extended from the light source mounting board40. An end portion of a ground wire111is connected to a ground pattern of the light source mounting board40by soldering and the other end portion of the ground wire111is fixed to the subframe22with a screw.

One end portions of three lead wires11are connected to the light source mounting board40by soldering and the other end portions are connected to the end part33of the flexible circuit board3by soldering.

A heat radiation sheet17is stuck on the upper face of the subframe22in a region where the twin laser light source4is mounted.

Protruded parts226in which an opening is formed are formed at an end part of the subframe22on the side where the first bearing part211of the mainframe21is provided. A supporting board57for supporting the light receiving element55for signal detection is adhesively fixed to the protruded parts226. The light receiving element55is supported at a center in a longitudinal direction of the supporting board57. End parts571,572on both right and left sides of the supporting board57are bent so as to interpose the protruded parts226between them and the supporting board57is fixed to the protruded parts226with an adhesive. Since the structure as described above is employed in this embodiment, even when a space for disposing the light receiving element55is small, the size of the supporting board57can be increased. Therefore, since the supporting board57is provided with a high heat radiation property and a large heat capacity, temperature rise of the light receiving element55for signal detection due to heat generated in the twin laser light source4or the like can be prevented. Further, after the supporting board57has been adhesively bonded, even when imbalance is occurred in the contraction or expansion of the adhesives on both the right and left sides when an environmental temperature is changed, a variation of the position and attitude of the light receiving element55is restricted. The sensor lens54whose outside shape is cylindrical is disposed on the inner side of the protruded parts226.

An opening which is formed in a substantially U-shaped groove is formed in the other end part of the subframe22and the collimating lens53is fixed to the opening.

Further, the light receiving element56for monitor to which an end part of the flexible circuit board3is connected is mounted on the subframe22on the rear side of the half mirror52.

As shown inFIG. 11andFIGS. 12(a) through12(d), the actuator cover7is structured of a piece of metal plate which is worked into a specified shape. Also with reference inFIGS. 1 and 2(a), the actuator cover7includes a first upper plate part71as a heat radiation part described below which is formed in a trapezoid shape and covers a region where the laser driver IC30is mounted on the flexible circuit board3, a second upper plate part72as a cooling part described below which is formed in a U-shape and extended toward the objective lens driving mechanism9side from the first upper plate part71to cover right and left wires, a fixing plate part73which is fixed to the device frame2with a metal screw at a tip end part of the second upper plate part72, two pawl parts74,75which are extended to an under face side of the device frame2from an outer peripheral edge portion of the first upper plate part71through an side face of the device frame2, and an extended part comprising a side plate part76, which is extended to an under side of the device frame2from the outer peripheral edge portion of the first upper plate part71so as to pass between two pawl parts74,75, and an under plate part77which is bent at a lower end part of the side plate part76to cover the under face side of the device frame2. A boundary portion between the first upper plate part71and the second upper plate part72is formed as a stepped part by press working, and a boundary portion between the second upper plate part72and the fixing plate part73is formed as a stepped part by press working. The actuator cover7structured as described above is attached to the device frame2such that the first upper plate part71indirectly contacts through the heat radiation sheet18with the rear face of the flexible circuit board3at the region where the laser driver IC30is mounted.

FIG. 13is a schematic perspective view showing a part of a disk drive device on which the optical head device shown inFIG. 1is mounted and which is viewed obliquely from above.FIG. 14is an enlarged perspective view showing a part of the disk drive device shown inFIG. 13.

A disk drive device230in accordance with an embodiment is used in a notebook-sized personal computer or the like and is provided with a tray210on which an optical recording disk300is placed and which is movably held in a housing not shown. The tray210is structured of a resin frame and is provided with an opening part200which is opened along a moving direction of the optical head device1disposed on its rear side for exposing the objective lens91so as to face the optical recording disk300. The disk drive device230is provided with a spindle motor240for rotating the optical recording disk300at a substantially center portion of a placing part210afor the optical recording disk300.

A part of the spindle motor240, a part of the actuator cover7and a part of the upper face cover6are exposed from the opening part200in addition to the objective lens91. Especially, the second upper plate part72of the actuator cover7formed in a U-shape faces the optical recording disk300through a narrow gap space and thus a high degree of cooling efficiency by air is obtained. Accordingly, the second upper plate part72functions as a cooling part by air for efficiently cooling heat which is dissipated in the actuator cover7from the first upper plate part71in a trapezoid shape as a heat radiation part. In other words, airflow occurred by rotation of the optical recording disk300driven by the spindle motor240directly hits the second upper plate part72of the actuator cover7through the opening part200to accelerate air cooling to the second upper plate part72by the airflow and thus heat dissipated to the actuator cover7from the laser driver IC30can be effectively cooled. In accordance with this embodiment, since the first upper plate part71and the second upper plate part72are closely disposed each other, heat radiated to the first upper plate part71can be efficiently cooled by the second upper plate part72.

The objective lens drive mechanism9and the laser driver IC30are closely disposed in a radial direction of the optical recording disk300and the laser driver IC30is disposed on an outer side in the radial direction. An airflow occurred by the rotation of the optical recording disk300driven by the spindle motor240is stronger on an outer peripheral side of the optical recording disk300than on an inner peripheral side. Therefore, in this embodiment, although the laser driver IC30is not exposed from to open part200, a strong airflow flows into a rear side of the tray210through the opening part200to circulate air and thus radiation of heat from the upper face of the first upper plate part71can be efficiently performed.

When an optical head device1structured as described above is to be assembled, at fist, as shown inFIGS. 5(a) through6(b), the twin laser light source4, the diffraction element51, the half mirror52, the sensor lens54and the collimating lens53are mounted on the subframe22. In this step, the light receiving element55for signal detection and the light receiving element56for monitor are not mounted on the subframe22. Further, in this state, the diffraction element51and the sensor lens54are respectively temporarily fixed with the flat springs510,540.

Also in this state, the flexible circuit board3is not connected but, in this embodiment, the lead wires11are connected with the twin laser light source4. Therefore, for example, a first laser chip for DVD of the twin laser light source4is turned on by supplying power from the lead wire11to observe a first laser beam emitted from the collimating lens53. And, a position on an optical axis of the twin laser light source4is adjusted such that a light emitted from the collimating lens53becomes a collimate light. At this time, a position of the twin laser light source4in a direction perpendicular to the optical axis is also adjusted. Next, the second laser chip for CD is turned on and the second laser beam emitted from the collimating lens53is observed to adjust an angular position of the twin laser light source4and a position of the diffraction element51. After that, the twin laser light source4is fixed with an adhesive130.

In addition, under a state that the light receiving element55for signal detection is held by a robot or the like, the first laser beam and the second laser beam are emitted from the twin laser light source4and the light emitted through the collimating lens53is reflected by an inspection mirror instead of the optical recording disk300, and the positions of the light receiving element55for signal detection and the sensor lens54are adjusted such that the reflected light beam forms a spot at a specified position of the light receiving element55for signal detection. After the above-mentioned positional adjustments have been performed, the light receiving element55for signal detection and the sensor lens54are adhesively fixed to the subframe22.

After the adjustment has been performed on the subframe22, the subframe22is mounted on the mainframe21on which the directing mirror59is mounted as shown inFIGS. 4(a) through4(e). In this state, the objective lens drive mechanism9is not mounted on the mainframe21.

When the subframe22is to be mounted on the mainframe21, the first connecting part221and the second connecting part222of the subframe22are put on the first subframe connection part213and the second subframe connection part214of the mainframe21, and positional adjustment is performed such that the positioning projections218,219of the mainframe21are fitted into the elongated hole223and the circular hole224formed in the first connecting part221and the second connecting part222. Further, the first laser chip41of the twin laser light source4is turned on and an emitted light beam from the directing mirror59is observed to adjust inclination or the like of the subframe22.

After the above-mentioned adjustment work has been performed, a UV curing type of adhesive is coated at the stepped parts228,229formed with the edge portion of the first connecting part221and the edge portion of the second connecting part222on the first subframe connecting region213and the second subframe connecting region214. After that, the adhesive is solidified by ultraviolet irradiation to adhesively fix the first connecting part221and the second connecting part222to the first subframe connecting region213and the second subframe connecting region214. In this case, the adhesive enters into a gap space between the first subframe connecting region213and the first connecting part221and a gap space between the second subframe connecting region214and the second connecting part222. Therefore, the first subframe connecting region213and the second subframe connecting region214are face-bonded with the first connecting part221and the second connecting part222.

Next, as shown inFIG. 3(a), the objective lens drive mechanism9is mounted on the mainframe21. Further, the flexible circuit board3on which the laser driver IC30is mounted is mounted on the mainframe21. In addition, the end parts31,32,33,34of the flexible circuit board3are respectively connected to the wiring circuit board550on which the light receiving element55for signal detection is mounted, the light source mounting board40on which the twin laser light source4is mounted, and the light receiving element56for monitor.

Next, the actuator cover7is attached to the device frame2in the state that the heat radiation sheet18is disposed between the flexible circuit board3and the actuator cover7. Further, the upper cover6is attached to the upper face of the device frame2and the under cover8is attached to the bottom face of the device frame2. In this manner, the optical head device1is assembled.

As described above, in the optical head device1in accordance with this embodiment, the upper face of the twin laser light source4on which the laser chip41is mounted is directed to the upper face of the optical head device1, and the upper face of the radiation fin44is mounted to abut with the stepped part226of the subframe22, and the under face of the radiation fin44corresponding to the portion where the laser chip41of the twin laser light source4is mounted is exposed outside to form the exposed part46, and the center projecting part122of the metal member12is disposed on the exposed part46. Therefore, heat radiated from the under face side of the radiation fin44corresponding to the portion where the laser chip41is mounted to the center projecting part122can be efficiently transmitted to the subframe22through the projecting parts121,123of the metal member12which are formed on both sides of the center projecting part122. Further, heat can be also efficiently radiated to the subframe22from both the end parts of the radiation fin44. Therefore, a service life of the twin laser light source4can be extended.

Further, in this embodiment, the projecting parts121,123and both sides of the metal member12formed in the E-shape in a plan view are respectively disposed on the under face228of the subframe22so as to be adjacently provided on the outer side of both the end parts of the radiation fin44. Therefore, when the projecting parts121,123formed on both sides of the center projecting part122of the metal member12are disposed so as to extend along both end parts of the radiation fin44, the size of the projecting parts121,123can be made larger while considering their space efficiency. Accordingly, the heat radiated to the center projecting part122from the radiation fin44can be efficiently transmitted to the subframe22from the projecting parts121,123and the size of the optical head device1is not required to be made larger.

In addition, in the optical head device1in accordance with this embodiment, the device frame2is structured of the mainframe21comprised of a resin frame-like part to which the subframe22comprised of a zinc die-casting product is adhesively fixed. Therefore, the device frame2is provided with a sufficient strength. Further, the subframe22is provided with a high heat transmission property and the mainframe21is inexpensive. Therefore, according to this embodiment, together with cost and weight reduction of the device frame2, heat generated in the twin laser light source4can be radiated to the mainframe21through the subframe22.

Further, as described above, since the optical head device1in accordance with the above-mentioned embodiment also performs recording to the optical recording disk300, a lot of heat is generated in the laser driver IC30. However, the laser driver IC30is put on and brought into contact with the first upper plate part71as a heat radiation part of the actuator cover7which is separately formed from the upper cover6for covering the twin laser light source4and a plurality of optical elements. Therefore, heat generated in the laser driver IC30is not transmitted to the upper cover6and thus the optical elements can be protected from heat generated in the laser driver IC30. In addition, since the second upper plate part72as a cooling part of the actuator cover7faces the optical recording disk300, the actuator cover7is cooled by air flow generated by rotation of the optical recording disk300. Therefore, according to this embodiment, heat generated in the laser driver IC30is radiated effectively.

In addition, in this embodiment, an opposite side of the actuator cover7to the objective lens drive mechanism9with respect to the laser driver IC30is fixed to the mainframe21and an opposite side of the actuator cover7to the laser driver IC30with respect to the objective lens drive mechanism9is fixed to the mainframe21. Especially, the actuator cover7is provided at the opposite side to the objective lens drive mechanism9with respect to the laser driver IC30with the side plate part76and the under plate part77as an extended part which is extended to the under face side of the mainframe21when the optical disk300side of the actuator cover7is set to be the upper face side. Therefore, heat generated in the laser driver IC30is transmitted from the actuator cover7to the mainframe21which contains heat-conductive fillers, and thus heat radiation efficiency from the mainframe21can be improved.