JPS6120234A - Optical recording and reproducing head - Google Patents

Abstract

PURPOSE:To realize a multi-functional and practical optical recording and reproducing head, by closely arranging at least two almost circular light spots and at least one oval light spot along the same information track of an optical disk. CONSTITUTION:A semiconductor laser 30 for forming a circular light spot on an optical recording disk generates a light beam 30a and its oscillating wavelength is lambda2 which is the same as that of the 2nd semiconductor laser 20. It is desirable to use a different wavelength from that of the 1st semiconductor laser as the oscillating wavelength of the semiconductor laser 30. The condenser lens 31 of the laser 30 condenses the lights radiated from the laser 30 to an almost parallel optical beam. An optical beam synthesizer 32 using a polarization beam splitter combines the optical beam 10a outputted from a semiconductor laser 10 and the optical beam 30a outputted from the laser 30 from a different direction and radiates the combined beams in the same direction. The combined optical beams 10a and 30a are converted into an optical beam whose cross section is almost circular by means of an expanding prism 12 and introduced to a stopping lens 4 and information track 27 by a polarization beam splitter.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a recording/reproducing optical head used in an optical disk memory.

Conventional structure and problems In recent years, a semiconductor laser has been used as a light source, and the semiconductor laser light is narrowed down to a minute spot of φ1 μm or less, and is irradiated onto a disk-shaped information medium on which a photosensitive material is deposited to generate video signals and digital signals. Some optical disk devices have been proposed that record and reproduce information concentrically or spirally.

As an application example of this device, it has two laser light sources,
A conceivable device is one that focuses both laser beams simultaneously and irradiates the disk with the laser beams brought close to each other.

As an example of such a device, one light beam is converged into a long oval shape in the track direction, information is erased with this narrowed minute spot light beam, and the other light beam is condensed into a substantially circular shape on the disk. A device that records and reproduces information using a minute spot of light, a device that applies a thermal bias with one beam and records and reproduces information with the other beam, or a device that records and reproduces information using a microspot of light; Aperture, record with one light,
A conceivable device is one that can simultaneously read out the recorded signal using the other light beam, instantly reproduce the recorded signal, and check whether or not recording has been performed correctly.

FIG. 1 shows an example of a conventional optical recording/reproducing device having dual sources. That is, a laser beam 1a from a first light source 1 is shaped by a lens system 2, bent by a mirror 3, and focused onto a disk 6 by an aperture lens 4. On the other hand, the second light source 6
The light beam 6a emitted from the lens passes through a Fi lens 7, a half mirror 8, is bent by a mirror 3, and is focused on a disk 5 by an aperture lens 4.
It is squeezed upwards. Reflected light 6b from the disk 5 is taken out from a half mirror 8 and guided to a photodetector 9 for obtaining known focus and tracking control signals and a reproduction signal for reading information recorded on the disk 5. .

In this method of combining both laser beams by spatially separating them so as not to interfere with each other's optical path, one laser beam (for example, 6a) is incident on the aperture lens 4 at a considerable angle to its optical axis. I have to use aperture lens 4.
The aperture cannot be used effectively, causing a lot of light to blur, aberrations to occur, and aperture performance to deteriorate.

Semiconductor lasers generally have anisotropic divergence angles with different divergence angles in the vertical and horizontal directions, and the optical system for converging the laser beam into a circle on the disk becomes complex. Therefore, when semiconductor lasers are used as both light sources, the optical system becomes large and complicated, and the diameter of the light beam is large, making it difficult to spatially separate the two beams and combine them.

On the other hand, when the reflected light from the disk is configured as shown in FIG. 1, it is difficult to separate the reflected light from the disk 6 of both light sources. The reflected light of 1) adversely affects the return control performance and reproduction signal. A patent application filed in 1983 for an example of realizing a compact optical head that eliminates the above drawbacks.
-169564. This method involves placing two light spots with different wavelengths close to each other on the same information track on an optical recording disk using the same aperture lens, and making one light spot approximately circular and placing the other light spot on the same information track. An example is shown in which the light spot is shaped like an ellipse along the information track.

OBJECTS OF THE INVENTION The present invention forms at least two substantially circular light spots, each having a different wavelength, on the same information track on an optical recording disk using the same aperture lens, and It is an object of the present invention to provide a novel recording/reproducing optical head having means for forming an oval optical spot along an information track on the same information trunk and close to the two optical spots. do.

Structure of the Invention The present invention provides a means for combining laser beams having different wavelengths emitted from at least two first and second semiconductor lasers in the same direction, and a means for changing the cross-sectional shape of the combined laser beam by the same beam cross-sectional shape. A first light beam generating means outputs two light beams having substantially circular cross-sections with different wavelengths in the same direction, and a second light beam whose cross-sectional shape is oval from a third semiconductor laser. It has a generating means, a means for combining the first light beam and the second light beam and emitting the same in the same direction, and an aperture lens for narrowing down the emitted light, and on the same information track on the optical recording disk. This is a recording/reproducing light-emitting head that produces at least two substantially circular redundant spots and one oblong light spot.

DESCRIPTION OF THE EMBODIMENTS Before explaining the method of forming at least two substantially circular light spots and an oblong light spot on the same information track according to the present invention, the method shown in Japanese Patent Application No. 169564/1988 will be described. , a method of forming one optical spot and an oval optical spot on the same information track will be briefly explained with reference to FIG.

FIG. 2a is a plan view seen from the optical recording disk 5 side,
The figure shows a front view, and numeral 6 shows an optical recording disk, and 27 shows an enlarged view of a concentric or spiral information trunk or known optical guide groove on the optical recording disk. 4 indicates an aperture lens.

In FIG. 2, 10 is a semiconductor laser which is a first light source and outputs a first light beam 10a having a wavelength of λ1. 1st
For example, the light source 1o is focused into a substantially circular shape on the disk,
Record, playback and focus.

Used for servo signal detection for tracking control, etc. In general, semiconductor lasers that can oscillate at high output have different divergence angles of the light beam in the direction perpendicular to and parallel to the junction surface, and have an anisotropic far-field pattern, so optical loss is suppressed. Therefore, an optical system is required to convert the diameter of the light beam to create a circular, isotropic minute spot light on the disk.

Reference numeral 12 denotes an enlarging prism, which is used as a first cross-sectional shape shaping device for converting the diameter of the light beam. That is, when the light beam 10a that has been converted into parallel light by the condenser lens 11 is refracted by the magnifying surface A of the prism 12, the light beam 10a
Multiply the incident luminous flux width 11 by m to obtain the luminous flux width .

m at this time is given by the following formula.

m=I2/11=cos 02/cOSo1. ,,,
,,,, (1) where 01 is the angle of incidence on the prism 12, and 02 is the angle of refraction at the enlarged surface A. Therefore, by passing through this prism 12, the diameter of the light beam in the direction parallel to the junction surface of the semiconductor laser can be multiplied by m to approximately the same size as the diameter in the perpendicular direction. A minute spot of light can be obtained. There is almost no loss of light during cutting.

The light beam 10a multiplied by m on the magnifying surface A is totally reflected on the reflecting surface B of the prism 12, and the light beam 10a is reflected almost at right angles to the incident light on the prism 12, that is, the optical axis Y1-Y2 of the first light source 10. Can be bent. In addition, in order for light to efficiently enter the prism at the magnifying surface A of the prism 12, the magnifying surface A
It is desirable to arrange the light source 1o so that the light beam 10a can be incident as P-polarized light.

Here, the first beam 10a that has been totally reflected by the reflecting surface B is incident on the polarizing beam splitter B as S-polarized light.
Since the light source 1o is arranged, this light beam 10a is reflected by the polarizing beam splitter 13, transmitted through the first % wavelength plate 14, passes through the aperture lens 4, and is reflected on the disk 5 as a recording medium. This results in a substantially circular minute spot light 26 (see FIG. 2C). A signal is recorded or reproduced on, for example, the disk 6 by the minute spot light 25 focused into a substantially circular shape.

On the other hand, the reflected light from the disk 5 is transmitted through the aperture lens 4 and the first
The polarization direction is rotated by 90 degrees and transmitted through the polarization beam splitter 13, and the 20%
After passing through the wave plate 16 and the first optical filter 16,
The light passes through a reflection detection optical system 17 and is guided to a photodetector 19. The first filter 16 transmits almost 100% of the light beam with wavelength λ1, but transmits almost 100% of the light beam with wavelength λ2.
It is an optical filter that reflects 00%.

Next, the optical path of the second light beam 20a from the second light source 2o will be described. Light beam 2 from this second light source 30
0a is narrowed into an elongated oval shape in the track direction on the disk 5, for example, and is used for erasing signals by applying heating and slow cooling conditions to the recording thin film.

A light beam 2 from a second light source 3o consisting of a semiconductor laser
0a is a second lens which is focused by the condenser lens 21 and has a lens effect only in the direction parallel to the cemented surface of the semiconductor laser.
Lindrical lens 22 as a cross-sectional shape shaping device
, the beam diameter is reduced in this parallel direction. 23 allows almost 100% of the light beam of wavelength λ2 to pass through, and the light beam of wavelength λ1
The light beam stirrup is a 100% reflective optical second filter, and this second filter 23 removes the light energy of the wavelength λ1 component contained in the light beam 20a. After passing through the filter 23, the right angle prism 24
The light beam 20a whose optical path has been changed at
% wavelength plate 15 to the first filter 16. As described above, the first filter 16 reflects 100% of the light beam of wavelength λ2.
The light beam 20a reflected at The light is focused into a minute spot light 26 with an oval shape elongated in 27 directions.

In this way, since the approximately circular minute spot light 25 and the oval minute spot light 26 are formed with #1 of one aperture lens 4 along the optical axis, there is little optical loss and aberration. It becomes possible to arrange them close to the same track 27 on the disk 5.

Next, the present invention will be explained using FIGS. 3, 4, and 6.

FIG. 3 shows some examples of the arrangement of light spots on the same information track of an optical disc, which is realized by the present invention. FIG. 4 is a plan view of the optical system according to the present invention (FIG. 2 alc
FIG. 6 is a diagram (corresponding to FIG. 2) showing a method of combining a plurality of light beams, and the same parts as those used in FIG. 2 are all labeled with the same numbers.

FIG. 3 shows an example of the arrangement of at least approximately circular light spots arranged on the same information track 27 and light spots having an oval shape along the information track. The circular light spot is used for recording, reproducing, or recording/reproducing signals on the optical disk, and the oval light spot provides heating and slow cooling conditions to the optical recording medium used in the optical recording disk.
The 0 arrow A used to erase pre-recorded signals indicates the relative movement direction of each light spot and the information track 27.

In FIG. 3, an arbitrary point X on the information track is first scanned by the first light spot L1 (for example, a signal on the information trunk is detected and reproduced by the light spot L1), and then an oval light spot L3 is scanned. (for example, the light spot L1
), and then
Scanned by circular light spot L2 (for example, light spot L
Record the signal in the area erased in step 3) 0 As described above, all the signals on the information track can be partially rewritten - Figure 3 Now, any point X on the information trunk is First, the oval light spot L3 is scanned (the signal is erased), then the light spot L2 is scanned (a new signal is recorded), and then the light spot L1 is scanned (the signal is recorded by the light spot L2). (play back the signal and check its quality).

As described above, while erasing, the conventionally known DRAW (Direct Read after w) is applied to that part.
rite).

As mentioned above, at least two approximately circular light spots,
By arranging one oval light spot close to each other on the same information track, it is possible to realize a recording/reproducing optical head having various functions.

The present invention provides a specific optical means for forming the above-mentioned light spot arrangement on an optical recording disk.

Specific examples are shown in FIGS. 4 and 6.

In Figures 4 and 6, the same numbers as in Figure 2 are given.
marked with a symbol. In order to avoid duplication of explanation, only newly added points will be explained.
A light beam 30a is generated. This oscillation wavelength will be explained as being the same λ2 as the second semiconductor laser 2o.The oscillation wavelength of the semiconductor laser 3o is desirably at least a different wavelength from that of the first semiconductor laser.31 is the semiconductor laser 30 The condenser lens condenses the diverging light from the semiconductor laser 3o into a substantially parallel light beam.

Reference numeral 32 denotes a light beam combiner using a polarizing beam splitter, which combines the output light beam 10a of the semiconductor laser 1o and the output light beam 30a of the semiconductor laser 3o entering from a different direction, and emits the combined light beam in the same direction.

The combined light beams 10a and 30a pass through the magnifying prism 12
The beam is converted into a light beam with a substantially circular cross section by the polarizing beam splinter 13 and the aperture lens 4. It is guided in the direction of the information truck 27.

FIG. 6 shows how the light beams 10a, 20a, and 30a incident from each direction are directed toward the optical disk at the polarizing beam splitter 13.

A substantially circular light beam 30a incident from the same direction as the light beam 10a is reflected by the polarization plane and passes through the λ/4 plate 14 at the aperture lens 4 to form a substantially circular light spot on the disk 6. The reflected light of the light beam 30a on the optical disk passes through the polarizing beam splitter 13° plate 15, and then passes through the optical filter 1.
6, but it is reflected by this optical filter and does not reach the reflected signal detection optical system 17. The figure shows an example in which only the reflected beam 10a of wavelength λ1 enters the reflected signal detection optical system to control signal reproduction, focus, and tracking.

As described above, by introducing light beams of different wavelengths into the expanding prism that makes the cross-sectional shape of the light beam of the semiconductor laser substantially circular, substantially circular light spots of different wavelengths can be created on the optical disk. By combining these shunted light beams with the light beam incident from the other end of the polarizing beam splitter 13, one more oval light spot is created on the same information trunk in addition to the two circular light spots mentioned above. can be formed.

Although the wavelength of the light spot is not particularly mentioned in Fig. 3, at least the approximately circular light spot used for detecting the conventionally known focus and tracking control signals has a wavelength different from that of the other two light spots. It is preferable to have. The elliptical light spot L3 can be formed into an ellipse by using, for example, one semiconductor chino as a collection of a plurality of microscopic spots.

Effects of the Invention According to the present invention, by arranging at least two substantially circular light spots and at least one oval light spot close to each other along the same information track on an optical disk, multi-functionality can be realized. This makes it possible to realize a practical recording/reproducing optical head.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a conventional recording/reproducing optical head, and Figures 2(a) and 2(b) show an example of the configuration of a recording/reproducing optical head that forms two optical spots. Figures 3a and 3b are diagrams for explaining the functions between the information track and at least three optical spots, and Figures 4 and 6 show an embodiment of the recording/reproducing optical head of the present invention. FIG. 4... Aperture lens, 5... Disk (recording medium), 1o... First light source (semiconductor laser),
10a...first light beam, 12...
Enlarging prism (first cross-sectional shape shaping device), 13...
・Polarizing beam sinter, 14...First % wave plate, 15...Second % wavelength plate, 16...First filter, 17...Dividing prism, 20... ...
- Second light source, 20a - Second light beam, 22...
... Cylindrical lens (second cross-sectional shape shaping device), 23 ... Second filter, 27 ...
Information track, 30...Third semiconductor laser, 30
a: Optical output beam of the third semiconductor laser. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 (a) Figure 3

Claims (2)

[Claims] (1) Means for combining laser beams with different wavelengths emitted from at least two first and second semiconductor lasers in the same direction; The first light beams are output in the same direction as light beams each having a substantially circular cross-sectional shape.
a second light beam generating means in which the cross-sectional shape of the light beam of the third semiconductor laser is oval, and the first light beam and the second light beam are combined and directed in the same direction. Recording and reproducing light that has an emitting means and an aperture lens for narrowing down the emitted light, and creates at least two approximately circular light spots and one oval light spot on the same information track on an optical recording disk. head. (2) Among the three light spots formed on the same guide track on the optical recording disk, the emission wavelength of the light source of one of the approximately circular light spots is different from that of the other two light spots. The recording/reproducing optical head according to claim 1, which is configured to have a wavelength different from that of the emitted light.