JP2001126298A - Optical head device and disk drive assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device which has a reproduction function of a DVD and CD and recording and reproducing functions to and from CD system recording media, such as a CD-R and CD-RW in combination. SOLUTION: An objective lens 44 irradiates the disk with incident light by condensing the light thereto and passes the reflected light from the disk to a direction reverse from the direction of the incident light. First and second semiconductor lasers 32 and 36 emit first and second light rays. A dichroic prism 40 introduces the first and second rays as the incident light on the objective lens 44 and, on the other hand, separates the first and second reflected light rays corresponding to the first and second light rays. First and second photodetectors 33 and 37 detect the first and second reflected light rays. A converging optical system to convert the spread angle of a divergent luminous flux to a smaller spread angle and introduce the luminous flux to the dichroic prism 40 is disposed between a second light source 36 and the dichroic prism 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device and a disk drive device used in an optical disk device for performing recording, reproduction, erasure, and the like on an information recording medium using a light beam, and more particularly to two types of information having different specifications. This relates to a case where a recording medium is handled by one optical head device.

[0002]

2. Description of the Related Art In recent years, digital video discs (DV
D) Related products have been developed and the demand for optical disc devices has been increasing. In the case of a DVD device, it is a standard specification that not only a DVD but also a CD disk such as a CD, a CD-R, and a CD-RW can be reproduced. Has become.

[0003] In reproducing a DVD-based disc and a CD-based disc with a single device, a problem as an optical head device is mainly that two types of light having different wavelengths are required, and There is a need for a technique for reproducing two types of discs having different specifications.

Various types of such DVD / CD reproducing optical head devices have been conventionally developed, and a representative one of them is shown in FIG.

[0005] In FIG. 8, reference numeral 1 denotes a first hologram laser unit, 2, 3 and 4 denote first semiconductor lasers, first photodetectors, and first components which are components of the first hologram laser unit 1. A hologram element, 5 is a second hologram laser unit, 6, 7, and 8 are second semiconductor lasers, second photodetectors, and second hologram elements which are components of the second hologram laser unit 2, Reference numeral 9 denotes a dichroic prism, 10 denotes a wavelength selection surface of the dichroic prism 9, 11 denotes a collimator, 12 denotes a dichroic filter, 13 denotes an objective lens, 14 denotes a light disk (DVD), and 15 denotes an optical disk (CD). The wavelength selection surface 10 of the dichroic prism 9 has a wavelength of 650
The light having a wavelength of about 780 nm is almost transmitted, and the light having a wavelength of about 780 nm is almost reflected. The dichroic filter 12 has wavelength selectivity outside the central circular opening, so that the DVD light of 650 nm
CD light having a wavelength of 780 nm has a property of transmitting only inside the circular opening.

In the drawings, optical disks 14 (DVD) and 1
5 (CD) is shown, but one disk is actually mounted and used.

An optical system for reproducing a DVD includes a first hologram laser unit 1, a dichroic prism 9 (transmitting through the wavelength selection film 10), a collimator 11, a dichroic filter 12, an objective lens 13, and a light disk (DVD) 14. It consists of. On the other hand, an optical system for reproducing a CD includes a second hologram laser unit 5,
Dichroic prism 9 (reflects wavelength selection film 10),
It comprises a collimator 11, a dichroic filter 12, an objective lens 13, and a light disk (CD) 15.

The optical path is common to each of the disks 14 and 15 and the wavelength selection film 10 of the dichroic prism 9, the wavelength selection film 10 branches into a DVD optical path and a CD optical path, and a dedicated hologram laser unit is used. It is configured to be.

The dichroic filter 12 does not limit the aperture of DVD light having a wavelength of 650 nm, and the CD light having a wavelength of 780 nm becomes an aperture (NA: .about.0.45) at the time of reproducing a CD due to the above-described wavelength selection function. The aperture is limited as described above.

The operation of the reproduction signal system using the hologram laser units 1 and 5 is common to DVDs and CDs in principle, and the reflected light from the optical disk 14 or 15 is first-order diffracted by the hologram element 4 or 8. 4
The light is received by the photodetector 3 or 7 having a divided or six-divided photodiode, and a reproduction signal, a focus error signal, a tracking error signal, and the like are obtained.

The DVD optical system is designed in an infinite system or a shape close to the infinite system in order to obtain good reproduction characteristics in the DVD system, and the optical magnification is usually set to about 8 times. Since the CD optical system shares the objective lens 13 which is almost optimally designed for the DVD, it is necessary to optimize the light source position and restrict the aperture in order to cope with the fact that the disk thickness is different from that of the DVD. For this reason, the optimization of the light source position is performed by setting the light source (hologram unit 5) at a position where the aberration is minimized by adjusting the focal position near the recording surface of the CD. At this time, since the thicknesses of both DVD / CD discs are determined in advance, the optimal position of the light source for CD is automatically determined when the DVD optical system is determined. This automatically determines the optical magnification. For example, when the DVD system is 8 times, the CD system is automatically determined to be about 5.5 times, and it cannot be realized with other optical magnifications. Regarding the aperture restriction, the function of the dichroic filter 12 restricts the aperture to NA = 0.45 only in the case of the CD optical system, thereby cutting the outer beam having a large spherical aberration and obtaining a good wavefront aberration. .

With the above configuration and operation, DVD / CD
An optical head device having good reproduction characteristics for both disks has been obtained.

[0013] By the way, recording on a CD-R (using a recording method using a change in hue) and a CD-RW (using a recording method using a change in phase) has conventionally used a dedicated optical disk device. As the optical head device, a dedicated one having only the CD optical system is used. The major differences between the recording / reproducing optical head device and the read-only optical head device are the numerical aperture and the optical magnification. Normally, NA =
Although the recording is performed at 0.45, the standard specifies that recording is performed at NA = 0.5 for CD-R and CD-RW in order to narrow the spot diameter during recording.

The optical magnification is desirably made as small as possible without affecting the spot quality in order to increase the output power of the objective lens at the time of recording, and is usually set to about 4 to 4.5 times. Often.

[0015]

SUMMARY OF THE INVENTION Recent CD-Rs and CDs
-With the spread of RW, CD-R,
It is required to add a recording function of CD-RW. However, as described above, in the case of an optical head configured to cover both the DVD and CD optical systems with one objective lens 13, the optical magnification of the CD is automatically determined by the magnification of the DVD, and as a result, the CD-R , CD-R
The light emission power required to realize the recording of W cannot be obtained. For this reason, conventionally, there is no DVD-ROM device that realizes recording of CD-R and CD-RW.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical head device capable of combining the function of reproducing DVDs and CDs with the function of recording and reproducing data on CD recording media such as CD-R and CD-RW. I do.

[0017]

In order to achieve the above object, the present invention focuses and irradiates incident light on an information recording medium, and transmits reflected light from the information recording medium in a direction opposite to the incident light. An objective lens for passing light through the first
A first light source that emits light of a second wavelength, a second light source that emits second light of a second wavelength, and combines the first light and the second light to enter the objective lens. While guiding as light,
An optical path combining / separating element for separating the first and second reflected lights from the objective lens corresponding to the first and second lights, and the first and second reflected lights from the optical path combining / separating element Are provided between the second light source and the optical path combining / separating element, respectively, to reduce the spread angle of the divergent light flux from the second light source to a smaller spread angle. A focusing optical system for converting the light into the optical path combining / separating element.

By the above-mentioned means, in particular, since the focusing optical system is provided, the light use efficiency is improved, and the CD-R, CD
-It is possible to obtain a sufficient output power to realize RW recording. Even with such a configuration, the optical magnification of the DVD for reproduction is not affected.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows another embodiment. The description starts with the embodiment shown in FIG. Reference numeral 31 denotes a hologram laser unit prepared for DVD reproduction, and includes a first semiconductor laser 32 (first light source), a first photodetector 33, and a first hologram element. Light emitted from the semiconductor laser 32 is transmitted to a first hologram element 34.
Go straight ahead. The reflected light described later is diffracted by the first hologram element 34 and received by the photodetector 33.

Reference numeral 35 denotes a hologram laser unit prepared for reproducing a CD, which comprises a second semiconductor laser 36 (second light source), a second photodetector 37, and a first hologram element 38. ing. Light emitted from the second semiconductor laser 36 passes straight through the second hologram element 38. The reflected light described later is diffracted by the second hologram element 38 and received by the photodetector 37.

Reference numeral 40 denotes a cubic dichroic prism (optical path combining / separating element) having a wavelength selection film 41. This wavelength selection film 41 is a DVD light (first light) having a wavelength of about 650 nm from the first hologram laser unit 31.
), And almost reflects the CD light (second light) having a wavelength of about 780 nm from the second hologram laser unit 35.

Here, between the second semiconductor laser 36 and the dichroic prism 40, the divergent angle of the divergent light beam of the second light from the second semiconductor laser is converted into a smaller divergent angle, and the dichroic prism 40 (A focusing optical system) is provided. The function of the coupling lens 39 will be further described later.

The light (first light, second light) emitted from the dichroic prism 40 passes through a collimator 42 that converts incident light into parallel light, enters a dichroic filter 43, and further passes through the dichroic filter 43. Then, the light enters the objective lens 44. The light passing through the objective lens 44 is applied to the signal recording surface of the optical disk (45 or 46).

Here, the previous dichroic filter 4
3 has a wavelength selectivity outside the central circular opening, whereby the DVD light having a wavelength of 650 nm is entirely transmitted,
CD light having a wavelength of 780 nm has a property of transmitting only inside the circular opening. Therefore, the aperture becomes larger for DVD light and smaller for CD light.

The optical system for reproducing the DVD includes a first hologram unit 31, a dichroic prism 40 (the first light and the first reflected light are transmitted by the wavelength selection film 41),
It comprises a collimator 42, a dichroic filter 43, an objective lens 44, and an optical disk (DVD) 45. On the other hand, the optical system for reproducing the CD includes a second hologram unit 35, a coupling lens 39, and a dichroic prism 40.
(The second light and the second reflected light are reflected by the wavelength selection film 41), the collimator 42, the dichroic filter 4
3, an objective lens 44 and an optical disk (CD) 46.

As the optical path, each disk 45, 46
To the wavelength selection film 41 of the dichroic prism 40. The wavelength selection film 41 branches into a DVD optical path and a CD optical path, and dedicated hologram laser units are used.

Only the CD optical system has a coupling lens 39 between the hologram unit and the dichroic prism. As described above, the dichroic filter 43 does not limit the aperture of DVD light having a wavelength of 650 nm by the wavelength selection function, and converts the CD light having a wavelength of 780 nm into N at the time of CD reproduction.
A (up to 0.45).

The operation of the reproduction signal system using the hologram laser units 31 and 35 is common to DVDs and CDs in principle, and the reflected light from the optical disk 45 or 46 is first-order diffracted by the hologram element 34 or 38 and is reflected therefrom. The light is received by a photodetector 33 or 37 having a four-division or six-division photodiode, and a reproduction signal, a focus error signal, a tracking error signal, and the like are obtained.

As for the DVD optical system, in order to obtain good reproduction characteristics in the DVD system, the optical magnification is set to about 8 times in an infinite or almost infinite system, and then the objective lens 44 and the collimator 42 are set. Is designed.

Next, as for the CD optical system, the numerical aperture was set to NA = 0.5 in the CD-R and CD-RW standards. In order to increase the output power of the objective lens, in addition to the objective lens 44 and the collimator 42 described above, a coupling lens 39, which is a feature of the present invention, is disposed only in the CD optical system. I have.

In the present embodiment, a plano-convex lens is disposed as the coupling lens 39, and spherical aberration is canceled by optimizing the lens curvature, thickness, position and the position of the light source, and a favorable wavefront aberration of about 0.02λrms is obtained. Spot quality could be obtained.

FIG. 3A shows the relationship between the optical magnification and the light use efficiency. As shown in the example of FIG. 3, the smaller the optical magnification, the better the light use efficiency and the output power of the objective lens increases. However, if the optical magnification is too small, the beam filling rate decreases and the astigmatic difference / optical path The spot quality on the disc is degraded due to an increase in the influence of the aberration. Regarding the component transmittance, in the case of the DVD / CD shared system, the number of optical components arranged in the optical path is larger than that of the CD-dedicated optical system, so that the transmittance of light in the optical path is reduced. In consideration of these factors, in the present embodiment, the optical magnification of the CD system is set to 4 times.

The relationship between the optical magnification and the light use efficiency in FIG. 3A is such that the beam intensity distribution is as shown in FIG. 2 as shown in FIG. Derived from something. A portion where the beam radius is small has high strength, that is, the utilization efficiency is good.

The direction of the plano-convex lens (coupling lens) 39 is such that the convex surface is on the objective lens side. FIG. 4 shows a change in spot wavefront aberration when the objective lens is shifted depending on the direction of the convex surface. As shown in FIG. 4, it can be seen that turning the convex surface toward the objective lens side can reduce coma aberration at the time of shifting the objective lens.

Further, so-called stray light, which is generated when a part of light emitted from the second light source 36 and reflected on the surface of the plano-convex lens (coupling lens) 39 enters (returns) the photodetector 37, is reduced. Therefore, a plano-convex lens (coupling lens) 39
Are arranged at an angle. In other words, the stray light reflected on the surface of the plano-convex lens (coupling lens) 39 is incident on the photodetector 37 without diffracted by the hologram (zero-order diffracted), and is diffracted by first-order to the photodetector 37. Some stray light can be reduced by tilting the plano-convex lens (coupling lens) 39 as shown in FIG. However, if the tilt angle is too large, astigmatism is generated, and spot quality is reduced. In this embodiment, 3
When the angle exceeds 0 °, the entire wavefront aberration deteriorates due to the increase of astigmatism. Therefore, the tilt angle was set to 2 °.

FIGS. 5 (B) and 5 (C) show the inclination 4
The example of the route of the 0th-order stray light and the 1st-order stray light in the case of ° is shown. FIGS. 5D and 5E show the routes of the 0th-order stray light and the 1st-order stray light when the inclination is 0 °. The hologram laser unit, together with the coupling lens 39,
The outer case 80 forms an integral part.

As described above, in this embodiment, a DVD is formed at an optical magnification of 8 times and a CD is formed at an optical magnification of 4 times, while using one objective lens 44 and covering both optical systems of a CD. ing. As a result, DVD and CD can be reproduced, and the CD-R and CD-RW have good characteristics for recording and reproduction, have little characteristic deterioration when the objective lens is shifted, and have little stray light. A head device is provided.

The present invention is not limited to the above embodiment.

FIG. 2 shows another embodiment of the present invention.
This embodiment is an example in which a single semiconductor laser and a photodetector are used without using a hologram laser unit. In FIG. 2, reference numeral 47 denotes a DVD semiconductor laser that emits first light having a wavelength of 650 nm. The first light emitted from the semiconductor laser 47 is reflected by the flat plate beam splitter 51 and enters the prism beam splitter 52. This prism beam splitter 52 has a wavelength selection film 53.

On the other hand, reference numeral 48 denotes a semiconductor laser for CD, which emits second light having a wavelength of 780 nm. The second light enters the prism beam splitter 52 via the coupling lens 50, is reflected by the wavelength selection film 53, and travels toward the collimator 54.

Here, the wavelength selection film 53 of the prism beam splitter 52 transmits almost 100% for the first light having a wavelength of 650 nm, but almost 50% for the second light having a wavelength of 780 nm. It has the property of transmitting and reflecting almost 50%. On the other hand, the flat plate beam splitter 51
Has a half-reflection surface, and has a characteristic of 50% transmission and 50% reflection with respect to the first light having a wavelength of 650 nm,
The second light having a wavelength of 780 nm has a characteristic of transmitting almost 100%.

The first light or the second light emitted from the collimator 54 is aperture-controlled by the dichroic filter 55 and enters the objective lens 56. Objective lens 56
Converts incident light into an optical disk (information recording medium) 57 (DV
The information recording surface of D) or 58 (CD) is focused and irradiated, and the reflected light from the information recording medium is passed in the opposite direction to the incident light.

The dichroic filter 55 has a wavelength selectivity outside the central circular aperture, and thereby has a wavelength of 6
The 50 nm DVD light is transmitted through the entire surface and has a wavelength of 780 nm.
CD light has the property of transmitting only inside the circular aperture. Therefore, the aperture becomes larger for DVD light and smaller for CD light.

At the time of reproducing a DVD, the first semiconductor laser 4
The first light from 7 is a flat plate beam splitter 51 (reflection), a prism beam splitter 52 (transmission), a collimator 54, a dichroic filter 55, and an objective lens 5.
The light is condensed on the recording surface of the optical disk (DVD) 57 in the order of 6. The light reflected on the recording surface is reflected by the objective lens 56, the dichroic filter 55, the collimator 5
4. The light is received by the photodetector 49 via the prism beam splitter 52 (transmission) and the flat plate beam splitter 51 (50% transmission).

On the other hand, at the time of CD reproduction, the second light from the second semiconductor laser 48 passes through the coupling lens 50, the prism beam splitter 52 (reflection), the collimator 54, the dichroic filter 55, and the objective lens 56 in this order. The light is focused on the recording surface of the disk (CD) 58. The light reflected by the recording surface is reflected by an objective lens 56, a dichroic filter 55, a collimator 54, a prism beam splitter 52 (50% transmission), and a flat plate beam splitter 5.
The light is received by the photodetector 49 via 1 (100% transmission).

Signal detection starts with obtaining a focus error signal using astigmatism generated when the signal passes through the flat plate beam splitter 51, a tracking error signal by a push-pull method, a reproduction signal, and the like. A signal necessary for the optical system is obtained by a photodetector 49.

In the above-described discrete optical system shown in FIG.
The role and arrangement of the convex lens are the same as those described in the embodiment of FIG. 8x with DVD optics,
In a CD optical system, the magnification is four times. With this, DVD,
Good characteristics can be obtained not only for reproducing CDs but also for recording and reproducing CD-Rs and CD-RWs. Further, the optical head device is characterized in that the characteristic is less deteriorated when the objective lens is shifted and the stray light is small.

The present invention is not limited to the above embodiment. There are various embodiments of the configuration of the coupling lens. For example, it may be constituted by a refractive index partial lens having a layer having a different refractive index in the thickness direction or the radial direction, or a diffraction lens utilizing diffraction. In addition, the lens forming the condensing optical system is arranged to be inclined with respect to the optical axis of the light emitted from the second light source, but this can be applied to any of the embodiments. The light source on which the condensing optical system is arranged is the light source on the side in charge of recording.

FIG. 6A shows the structure of the recording surface of a CD.
FIG. 6B shows the structure of the recording surface of the DVD-ROM.
FIG. 6C shows the structure of the recording surface of the DVD-RAM.
As described above, as optical discs, there are discs having a large track pitch and shortest pit length.
There is a need for a light source for obtaining light beams having different wavelengths as described above.

FIG. 7 shows an example of an electric signal system for processing a signal read by the optical head device.
Photodetectors 116 include photodiodes 6A, 6B, 6
C, 6D, 6E, and 6F are provided. The output of each photodiode 6A, 6B, 6C, 6D, 6E, 6F is
Buffer amplifiers 23a, 23b, 23c, 23
d, 23e and 23f. Each of the A to F signals output from the buffer amplifiers 23a, 23b, 23c, 23d, 23e, and 23f is calculated as follows.

The adder 231 generates an (A + B) signal,
The adder 232 generates a (C + D) signal. The adder 233 uses the (A + C) signal from the adder 231 and the (C + D) signal from the adder 232 to generate (A + B) −
(C + D). This (A + B)-(C +
D) signal is used as a focus error signal.

The adder 234 generates a (A + C) signal, and the adder 235 generates a (B + D) signal. The (A + C) signal and the (B + D) signal are input to the phase difference detector 131. The output of the phase difference detector 131 is D
Used as a tracking error signal for VD. On the other hand, (E-
F) The signal is ignored because the switch 322 is turned off.

The (A + C) signal and the (B + D) signal are also input to the adder 236. The adder 236 calculates (A + B
+ C + D) signal (referred to as HF signal). This signal is derived via equalizer 124.

The E signal and the F signal are input to the adder 237. The (EF) signal is obtained from the adder 237. The (EF) signal is used as a tracking error signal for CD. That is, when the apparatus is in the CD playback mode, the switch 322 is turned on.

The above configuration is an example in which the first and second photodetectors for CD and DVD are also used. However, each of the photodetectors shown in FIG. Of course, a processing circuit may be added. Alternatively, the signal processing circuit having the configuration shown in FIG. 7 may be directly connected to each photodetector. In this case, the switch is always kept in a constant state according to the reproduction disk.

[0057]

As described above, according to the present invention, 1
DVD-CD playback CD-R, CD-RW
It is possible to provide an optical head device having good characteristics for all recording and reproduction of the optical head device, less characteristic deterioration at the time of shifting the objective lens, and less stray light.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between optical magnification, light use efficiency, and output power of an objective lens.

FIG. 4 is a diagram showing the relationship between the direction of the convex lens with respect to light and the wavefront aberration when the objective lens is shifted.

FIG. 5 is an explanatory diagram showing the relationship between the inclination of a convex lens and reflected stray light.

FIG. 6 is an explanatory view showing an information recording surface of various disks.

FIG. 7 is a diagram showing an electrical signal processing system of the optical head according to the present invention.

FIG. 8 is a diagram showing a configuration of a conventional optical head device.

[Explanation of symbols]

31 first hologram laser unit, 35 second hologram laser unit, 39 coupling lens (plano-convex lens), 40 dichroic prism, 42 collimator, 43 dichroic filter, 44 objective lens, 45 optical disc ( DVD), 46 ... optical disk (CD).

Claims (8)

[Claims] An objective lens configured to irradiate incident light on the information recording medium in a focused manner and pass reflected light from the information recording medium in a direction opposite to the incident light; A first light source that emits light, a second light source that emits second light of a second wavelength, and the first light and the second light are combined and guided to the objective lens as the incident light. On the other hand, an optical path combining / separating element that separates the first and second reflected lights from the objective lens corresponding to the first and second lights, and the first and second optical paths from the optical path combining / separating element. First and second photodetectors for detecting reflected light, respectively, provided between the second light source and the optical path combining / separating element, and having a smaller spread angle of a divergent light beam from the second light source. A focusing optical system for converting the angle into an angle and guiding the angle to the optical path combining / separating element. Optical head device for. 2. The first light source and the first photodetector, wherein:
Mounted on two substrates to form a first integrated light receiving and emitting element,
The second light source and the second photodetector are mounted on another substrate different from the first integrated light receiving and emitting element to form a second integrated light receiving and emitting element. The optical head device according to claim 1, wherein 3. An objective lens for converging and irradiating an incident light on an information recording medium and passing reflected light from the information recording medium in a direction opposite to the incident light, and an objective lens for transmitting a first light of a first wavelength. A first light source that emits light, a second light source that emits second light of a second wavelength, and the first light and the second light are combined and guided to the objective lens as the incident light. On the other hand, a beam splitter for separating the first and second reflected lights from the objective lens corresponding to the first and second lights, and detecting the first and second reflected lights from the beam splitter A light detector that is provided between the second light source and the optical path combining / separating element, and converts the divergent angle of the divergent light beam from the second light source into a smaller divergence angle to the optical path combining / separating element. An optical head device comprising a focusing optical system for guiding. 4. The focusing optical system comprises a convex lens, and the convex lens has a flat radius of curvature on a surface on the side of the second light source or a radius of curvature on a surface on a side opposite to the side of the second light source. 4. The optical head device according to claim 1, wherein the optical head device has a larger shape. 5. The optical head device according to claim 1, wherein the condensing optical system is constituted by a refractive index distribution type lens or a plane diffraction type lens. 6. The lens according to claim 1, wherein the lens forming the condensing optical system is arranged to be inclined with respect to the optical axis of the light emitted from the second light source. An optical head device according to item 1. 7. The information processing apparatus according to claim 2, wherein the second light performs recording and reproduction of information on the information recording medium.
4. The optical head device according to any one of 1 to 3. 8. An objective lens for converging and irradiating incident light on an information recording medium and passing reflected light from the information recording medium in a direction opposite to the incident light, and an objective lens for transmitting a first light of a first wavelength. A first light source that emits light, a second light source that emits second light of a second wavelength, and the first light and the second light are combined and guided to the objective lens as the incident light. On the other hand, an optical path combining / separating element that separates the first and second reflected lights from the objective lens corresponding to the first and second lights, and the first and second optical paths from the optical path combining / separating element. First and second photodetectors for detecting reflected light, respectively, provided between the second light source and the optical path combining / separating element, and having a smaller spread angle of a divergent light beam from the second light source. A focusing optical system that converts the light into an angle and guides the light to the optical path combining / separating element; and the first and second lights. Disk drive apparatus characterized by comprising a tracking error signal, respectively, and a circuit for obtaining a focus error signal and a reproduction signal, via the use of an output of the output device.