JPH10162421A - Optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical head capable of coping with various type optical disks and moreover realizing an optical disk device capable of miniaturization. SOLUTION: In the optical head, 1st and 2nd semiconductor lasers 11a and 11b are selectively energized to generate one of the 1st and 2nd laser beams having different wavelengths respectively, and the generated laser beam is guided to a common optical path by a polarizing beam splitter 200. The guided laser beam is focused on an optical disk by an objective lens, and the reflected light beam from the optical disk is detected by a detector. The 2nd laser beam is regulated in its beam diameter by a beam conversion optical element and is incident upon the polarizing beam splitter 200.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical head, and more particularly, to an optical head applicable to different types of optical recording media.

[0002]

2. Description of the Related Art There are various types of optical recording media such as optical disks, and various types of optical disk devices for optically reading information or data from such optical recording media have already appeared. I have. For example, as a recording medium, a CD (compact disk) or a CD-
It has been more than 10 years since optical recording media such as ROMs were developed, and optical disk devices corresponding to the media were developed. During this time, various types of optical recording media and optical disk devices have been proposed, and some of them have already been widely used for business use or consumer use. At the stage before the commercialization of optical recording media and optical disk devices, standards are examined in various fields in the industry in advance, standards are determined based on the examination, and product design and manufacturing are performed based on these standards. Has been made.

[0003]

In recent years, there has been a demand for an increase in the recording capacity of an optical recording medium and an extension of its function, for example, a demand for recording and erasing not only for reproduction but also for recording. Emerged from today,
A new standard represented by DVD has emerged, and various proposals have been made for this standard. In such a background, various types of optical recording media, that is, various types of optical disks have appeared, and optical disk devices corresponding to such various types have been developed and proposed. Providing various optical disk devices corresponding to various types of optical disks in this way is physically and economically problematic, and the emergence of a single optical disk device that can support various types of optical disks has been developed. Is desired.

The present invention has been made in view of the above-described problems, and has as its object to provide an optical head capable of coping with various types of optical disks and realizing an optical disk device that can be reduced in size. To be.

[0005]

According to the present invention, there is provided:
A first generating means for generating a second light beam, a second generating means for generating a second light beam, and a first and a second generating means for selectively energizing the first and the second generating means. Biasing means for generating one of the light beams; light path defining means for defining first and second optical paths through which the first and second light beams pass and a common optical path through which the first and second light beams pass, respectively; , The first
Optical means for directing the first and second light beams passing through the common light path to the common light path, and convergence for converging the first and second light beams passing through the common light path toward the optical recording medium An optical head comprising: means for detecting one of a first light beam and a second light beam reflected from an optical recording medium to generate a detection signal.

Further, according to the present invention, a first generating means for generating a first light beam having a first wavelength;
Second generating means for generating a second light beam having a second wavelength different from the first wavelength, and first and second light beams by selectively energizing the first and second generating means. Biasing means for generating one of the following; optical path defining means for defining a first and second optical path through which the first and second light beams pass, and a common optical path through which the first and second light beams pass, respectively, An optical unit for directing the first and second light beams passing through the first and second optical paths to a common optical path, respectively, and a first and a second optical beam that regulate the diameter of the second light beam in the second optical path. Regulating means for varying the diameter of the light beam, first and second light beams passing through the common optical path;
Converging means for converging the light beam toward the optical recording medium; detecting means for detecting one of the first and second light beams reflected from the optical recording medium to generate a detection signal;
An optical head characterized by comprising:

Further, according to the present invention, a first semiconductor laser for generating a first laser beam having a first wavelength and a second laser beam having a second wavelength different from the first wavelength are used. A second semiconductor laser to be generated; an energizing means for selectively energizing the first and second semiconductor lasers to generate one of the first and second laser beams;
And first and second optical paths through which the second laser beam passes and optical path defining means for defining a common optical path through which the first and second light beams pass, and are disposed in the first and second optical paths, respectively. First and second collimator lenses for collimating the first and second laser beams generated from the first and second semiconductor lasers, and transmitting one of the collimated first and second laser beams; A polarizing beam splitter that reflects the other beam and directs the beam to a common optical path, and a beam diameter of the second laser beam collimated in the second optical path so that the beam diameters of the first and second laser beams are different. Regulating means; an objective lens for converging the first and second laser beams passing through the common optical path toward an optical recording medium; and an objective lens for reflecting the first and second laser beams from the optical recording medium. The optical head is characterized by comprising a detecting means for generating a detection signal by detecting a is provided.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an optical disk drive equipped with an embodiment of the optical head according to the present invention. FIG. 1 shows an outline of a system of an optical disk device incorporating an optical head according to an embodiment of the present invention. FIG. 2 shows an outline of a mechanism for driving the optical head shown in FIG. 3 shows the structure of the optical head shown in FIGS.

[0009] As shown in FIG.
The optical head 3 is arranged below an optical disk 50 as a recording medium driven by a spindle motor 33, and the optical disk 50 rotated by a light beam from the optical head 3 is searched for, and a detection signal from the optical head 3 is processed by signal processing. The signal is output to the system 31, converted into a reproduction signal by a decoder (not shown) in the signal processing system 31, and output to the external device 160.

[0010] From the external device 160, command signals for reproduction and recording, for example, the type of recording medium, recording, or
A reproduction processing command, an access signal, and the like are input to the signal processing system 31, and a control signal is supplied to the control system 32 and the optical head 3 based on the command signal. For example, the optical head 3 is supplied with a semiconductor laser drive signal, an objective lens pull-in signal at the start of a search, and the like from the signal processing system 31 to the optical head 3, and the optical head 3 sends a light beam detection signal to the signal processing system 31 The signal is supplied, processed by the signal processing system, and the processing result is supplied to the control system 32. The control system 32 generates a focus error signal and a tracking error signal based on the signal from the signal processing system, and controls the objective lens 43 in the optical head 3 in response to these signals. The track on 50 is tracked by the focused light beam. Further, the spindle motor 33 is controlled by a control signal from the control system 32, and the rotation of the optical disk 50 is controlled.

As shown in FIG. 2, the optical head 3 includes a fixed optical system 2 fixed on a base 4 and a moving optical system 5 mounted on a carriage. It is configured to be able to move in the radial direction of the optical disk 50 above. A light beam R emitted from the fixed optical system 2, which will be described in detail later with reference to FIG.
Is guided into the moving optical system 5, is reflected by the rising mirror 41 in the moving optical system 5, and its optical path is substantially 90 °.
It is bent once and directed to the objective lens 43. An aperture 44 for limiting the aperture is provided on the light source side of the objective lens 43, that is, on the mirror side. The objective lens 43 moves the objective lens 43 along its optical axis, and Is suspended by the objective lens drive coil 46 so that the direction in which the image is directed can be changed.
In this embodiment, the objective lens 43 has a substrate thickness of 0.1 mm.
It has lens characteristics corresponding to a 6 mm DVD optical disk.

The light beam R directed to the objective lens 43
Before the light beam R enters the objective lens 43, its aperture is limited by an aperture, and the light beam R whose aperture is limited is
The light passes through the objective lens 43 and is focused on the optical disk 50 by the objective lens 43. Optical disk 50
The light beam R reflected by the objective lens 43
And is returned to the mirror 41, reflected by the mirror 41 and guided to the fixed optical system 2.

In the reproducing mode for reproducing information with the light beam R, the fixed optical system 2 generates a light beam R having a substantially constant light intensity.
The intensity-modulated light beam is returned to the fixed optical system 2 via the moving optical system 5. In a recording mode for recording information with the light beam R, the fixed optical system 2 generates a light beam R whose intensity is modulated according to data to be recorded.
This light beam is directed to a light reflecting surface as a recording surface of the optical disk 50, and a physical change, that is, a change in reflectance is caused on this surface, and data is recorded on the optical disk 50.
The light beam reflected by the light reflecting surface is similarly returned to the fixed optical system 2 via the moving optical system 5.

In the fixed optical system 2, as shown in FIG. 3, first and second light emitting system optical paths 9A, 9B,
A common optical path 9C and a detection optical system optical path 9D are formed,
The first and second semiconductors 11 are provided in the openings of the optical base 8 defining the optical paths 9A and 9B of the second light emission system, respectively.
a and 11b are fixed. First and second semiconductors 1 each energized by a drive current from signal processing system 31
Reference numerals 1a and 11b denote first and second laser beams having different wavelengths, for example, a wavelength of 650 nm and a wavelength of 78, respectively.
Generate first and second laser beams having 0 nm. The first and second light emitting system optical paths 9A and 9B have the first
First and second collimator lenses 12a and 12b for collimating the first and second laser beams, respectively, and the first laser beam from the first collimator lens 12a is used as a polarizing beam splitter disposed on the common optical path 9C. 2
00, and the second laser beam from the second collimator lens 12b is reflected by the reflecting prism 20 arranged on the second light emission system optical path 9B and is incident on the light beam conversion optical element 300.

As shown in FIG. 4, the light beam conversion element 300 has an aperture 3 formed in a thin plate of about 1 mm made of aluminum.
01, for example, an opening 301 having a diameter of about 2.6 mm is formed. Accordingly, the light beam incident on the light beam conversion element 300 is incident on the polarization beam splitter 200 whose diameter is limited and arranged on the common optical path 9C. The polarization beam splitter 200 has a polarization beam splitter surface 201 therein, on which a beam splitter film having wavelength dependence, for example, a dielectric multilayer film is provided. When the incident light beam has the property of P-polarization as shown in FIG. 5, the beam splitter film having the wavelength dependence reflects the incident light beam having a wavelength in the range of approximately 750 nm to 850 nm, and approximately 630 nm. From 6
It has the property of transmitting an incident light beam having a wavelength in the range of 90 nm. Therefore, if the first laser beam having a wavelength of 650 nm traveling in the first light emission system optical path has the property of P-polarized light, it passes through the polarization beam splitter surface 201 of the polarization beam splitter 200 and passes through the common optical path 9C.
Turned to If the second laser beam having a wavelength of 780 nm traveling in the optical path of the second light emission system has the property of P-polarized light, the second laser beam is applied to the polarization beam splitter surface 201 of the polarization beam splitter 200. And is directed to the common optical path 9C.

The first and second laser beams emerging from the polarization beam splitter 200 pass through a beam splitter 13 having a semi-permeable film as shown in FIG. 5 or a P-polarized light beam and reflect S-polarized light. Then, the light passes through the polarizing beam splitter 13, passes through the 波長 wavelength plate 13, and is directed to the moving optical system 5. The first and second light beams reflected by the optical disk 50 and returned from the moving optical system 5 to the fixed optical system 2 pass through the quarter-wave plate 13 again and return to the beam splitter 13. Since the returned first and second light beams pass through the quarter-wave plate 13 twice, their polarization characteristics are converted from P-polarized light to S-polarized light. If the polarization beam splitter 13 transmits the P-polarized light beam and reflects the S-polarized light, the first and second light beams are reflected by the polarization beam splitter 13 and transmitted to the photodetector 18. Pointed. Further, even if the polarization beam splitter 13 is a beam splitter 13 having a semi-permeable film, the first and second light beams are similarly reflected by the beam splitter 13 and directed to the photodetector 18.

In the optical path 9D of the detection optical system between the beam splitter 13 and the photodetector 18, a converging lens 15, a concave lens 16 and a cylindrical lens 17, which constitute a lens system for focus detection, are arranged. The shape of the beam spot on the photodetector 18 formed by the light beam is changed according to the position of the light beam, and a detection signal for generating a focus error signal and a tracking error signal is generated from the photodetector 18. The photodetector 18 is fixed to an opening of the optical base 8 that defines a detection optical system optical path 9D, similarly to the semiconductor lasers 11a and 11b.

As an example of the above-mentioned optical disk device, a CD
The case where the system optical disk 50 and the DVD system optical disk 50 are loaded will be described. CD optical disk 5
0 indicates that the substrate thickness of the DVD-based optical disk 50 is 0.6 mm.
, The substrate thickness is as thick as 1.2 mm.
The numerical aperture (N) of the light beam applied to the D-type disc 50
A) can be reproduced if the numerical aperture (NA) of the light beam applied to the DVD-based disc 50 is set to 0.39, which is smaller than 0.60. When a CD optical disk 50 is loaded in the optical disk device, the second semiconductor laser 1 is transmitted from the signal processing system 31 to the optical head 3 in response to a CD reproduction or recording command from the external device 160.
A drive signal that makes 1b valid is provided. As a result, the second semiconductor laser 11b operates to generate a second laser beam from the second semiconductor laser 11b. This second laser beam is collimated by the collimator lens 12b in the second light emission system optical path 9B as shown in FIG. 3, is reflected by the reflection prism 20, and enters the light beam conversion element 300. The diameter of the light beam is converted by the light beam conversion element 300 and the light beam enters the polarization beam splitter 200 disposed on the common optical path 9C. That is, the light beam conversion element 300
Is converted into a laser beam having a numerical aperture of 0.39 by the light beam converting element 300. The second laser beam is reflected by the polarization beam splitter 200, directed to the moving optical system 5 via the common optical path 9C, and irradiated onto the CD optical disk 50 by the objective lens 43. At this time, since the second laser beam is a laser beam corresponding to a numerical aperture of 0.39 corresponding to the CD-type optical disk 50, the reproduction and reproduction of information from the CD-type optical disk 50 by the second laser beam are performed. Recording on the CD-type optical disk 50 becomes possible. The second light reflected from the CD-type optical disc 50
Is returned to the fixed optical system 2 via the moving optical system, passes through the common optical path 9C, and passes through the beam splitter 13
Is guided to the detection optical path 9 </ b> D, and is detected by the detector 18.

In contrast to the above-described example, the optical disc device is
When the D-type optical disk 50 is loaded, the first semiconductor laser 1 is transmitted from the signal processing system 31 to the optical head 3 in response to a DVD-based reproduction or recording command from the external device 160.
A drive signal that makes 1a valid is provided. As a result, the first semiconductor laser 11a operates to generate a first laser beam from the first semiconductor laser 11a. This first laser beam is collimated by the collimator lens 12a in the first light emission system optical path 9A and directed to the polarization beam splitter 200 as shown in FIG. The first laser beam that has passed through the polarization beam splitter 200 is directed to the moving optical system 5 via the common optical path 9C, and is irradiated on the DVD optical disk 50 by the objective lens 43. At this time, since the first laser beam is a laser beam corresponding to a numerical aperture of 0.60 corresponding to the DVD-type optical disk 50, the first laser beam reproduces information from the DVD-type optical disk 50, Recording on the DVD-type optical disk 50 becomes possible. DV
The first laser beam reflected from the D-system optical disk 50 is similarly returned to the fixed optical system 2 via the moving optical system, passes through the common optical path 9C, and is guided to the detection optical path 9D by the beam splitter 13; Detected by detector 18.

In the above-described embodiment, the light beam conversion element 300 has the opening 301 formed in the thin plate. Instead of such a thin plate, the polarization on the optical path side of the second light emitting system is changed as shown in FIG. Mask part 2 is provided on the surface of beam splitter 200
03, and a transmission window 204 corresponding to the opening 301 may be provided. In such a light beam conversion element 300, the light beam incident on the mask 203 is transmitted through the transmission window 20.
The beam is limited to a diameter corresponding to No. 4 and is incident on a polarization beam splitter 200 arranged on the common optical path 9C. In the above-described embodiment, an example in which the beam splitter film having the wavelength dependency shown in FIG. 5 is provided on the polarizing beam splitter surface 201 of the polarizing beam splitter 200, but the wavelength dependency shown in FIG. A beam splitter film may be provided. The beam splitter film having the wavelength dependence shown in FIG. 8 has a wavelength of approximately 750 nm to 850 nm when the incident light beam has S-polarization characteristics.
And reflects an incident light beam having a wavelength in the range
It has the property of transmitting an incident light beam having a wavelength in the range of nm to 690 nm. Therefore, if the first laser beam having a wavelength of 650 nm traveling in the first light emission system optical path has the property of S-polarized light, it passes through the polarization beam splitter surface 201 of the polarization beam splitter 200 and enters the common optical path 9C. Pointed. A second laser beam having a wavelength of 780 nm traveling in the optical path of the second light emission system is S
If the second laser beam has polarization characteristics, the second laser beam is reflected by the polarization beam splitter surface 201 of the polarization beam splitter 200 and directed to the common optical path 9C.

As described above, in the optical head of the present invention, unlike the conventional optical head, it is not necessary to provide an optical head for each type of disc, and most optical systems can be shared. Therefore, the cost of parts and the cost of assembly can be reduced, and the size of the optical head can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of a system of an optical disk device in which an optical head according to an embodiment of the present invention is incorporated.

FIG. 2 schematically shows a mechanism for driving the optical head shown in FIG.

FIG. 3 is a cross-sectional view schematically showing a structure of the optical head shown in FIGS. 1 and 2, showing a case where a second semiconductor laser is effective.

FIG. 4 is a perspective view showing a light beam conversion element shown in FIG. 3;

5 is a graph showing the transmittance of a P-polarized component of a wavelength-dependent beam splitter film provided in the polarization beam splitter of the polarization beam splitter shown in FIG.

FIG. 6 is a cross-sectional view schematically showing the structure of the optical head shown in FIGS. 1 and 2, similarly to FIG. 3, showing a case where the first semiconductor laser is effective.

FIG. 7 is a perspective view showing a light beam conversion element that can be used in place of the light beam conversion element shown in FIG. 3;

8 is a graph showing the transmittance of an S-polarized component of a wavelength-dependent beam splitter film provided in a polarization beam splitter according to another example of the polarization beam splitter shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 2 ... Fixed optical system 3 ... Optical head 5 ... Moving optical system 11a, 11b ... Semiconductor laser 18 ... Photodetector 43 ... Objective lens 50 ... Optical disk 200 ... Polarization beam splitter 300 ... Light beam conversion element

Claims (3)

[Claims] A first generating means for generating a first light beam; a second generating means for generating a second light beam; and selectively energizing the first and second generating means. Biasing means for generating one of the first and second light beams, and a first and second optical path through which the first and second light beams pass, and a common means through which the first and second light beams pass, respectively. Optical path defining means for defining an optical path; optical means for directing first and second light beams passing through the first and second optical paths to a common optical path, respectively, and first and second light beams passing through the common optical path Converging means toward the optical recording medium, and detecting means for detecting one of the first and second light beams reflected from the optical recording medium to generate a detection signal. Characteristic optical head. 2. A first generating means for generating a first light beam having a first wavelength, and a second generating means for generating a second light beam having a second wavelength different from the first wavelength. Generating means, energizing means for selectively energizing the first and second generating means to generate one of the first and second light beams, and passing the first and second light beams respectively An optical path defining means for defining a common optical path through which the first and second optical paths and the first and second optical beams pass; and a first and a second optical beam passing through the first and second optical paths as common optical paths, respectively. Optical means for directing; regulating means for regulating the diameter of the second light beam in the second optical path so that the diameters of the first and second light beams are different; and first and second optical means which have passed through the common optical path. Converging means for converging the light beam toward the optical recording medium; and a first beam reflected from the optical recording medium. And a detecting means for detecting one of the second light beams to generate a detection signal. 3. A first semiconductor laser for generating a first laser beam having a first wavelength, and a second semiconductor for generating a second laser beam having a second wavelength different from the first wavelength. A laser; an energizing means for selectively energizing the first and second semiconductor lasers to generate one of the first and second laser beams; and an energizing means for transmitting one of the first and second laser beams, respectively. Optical path defining means for defining a common optical path through which the first and second optical paths and the first and second light beams pass; and first and second optical paths respectively disposed in the first and second optical paths.
A first and a second collimator lens for collimating the first and second laser beams generated from the semiconductor laser, and transmitting one of the collimated first and second laser beams and reflecting the other. A polarizing beam splitter for directing the beam to a common optical path, regulating means for regulating the beam diameter of the second laser beam collimated in the second optical path so that the beam diameters of the first and second laser beams are different, An objective lens for converging the first and second laser beams passing through the common optical path toward the optical recording medium, and detecting and detecting one of the first and second laser beams reflected from the optical recording medium An optical head, comprising: detection means for generating a signal.