JPH03162724A - Optical pickup device - Google Patents

Abstract

PURPOSE:To speed up writing and/or reading-out by disposing an anamorphic prism in an optical path of the light beams from plural laser light sources to a recording medium. CONSTITUTION:The plural light beam 8 generated from the laser light source are expanded in diameter in a prescribed direction by the anamorphic prism 12. The beam shape of the plural light beams 8 can, therefore, be corrected to an approximately circular shape by disposing the anamorphic prism 12 in a prescribed direction. The light beams are thereby well condensed onto the recording medium 5. The recording density of the information signals which allow writing and/or reading-out is additionally improved in this way.

Description

[Detailed Description of the Invention] A. INDUSTRIAL APPLICATION FIELD The present invention relates to an optical pickup device for writing and/or reading information signals to and from a recording medium, and more particularly to an optical pickup device configured to use a plurality of light beams simultaneously. B. Summary of the Invention The present invention has a plurality of laser light sources and simultaneously uses a plurality of light beams to write and/or write information signals on a recording medium.
Alternatively, in an optical pickup device that performs readout, an anamorphic prism is placed in the optical path of the light beams from multiple laser light sources to the recording medium, thereby correcting the beam shape of the light beams emitted from the laser light sources for recording. Writing and/or reading by allowing better focusing of the light beam on the medium and reducing the spacing of the beam spots on the recording medium to increase the number of light beams that can be used simultaneously by a single objective lens The aim is to speed up the process. Further, the present invention provides an optical pickup device as described above, in which an anamorphic prism is disposed between an optical device for guiding reflected light from a recording medium to a light detecting means side and a recording medium. The purpose is to miniaturize the device by allowing light detection to be easily performed without increasing the lateral magnification of the detection means. C. 2. Description of the Related Art Conventionally, disk-shaped recording media such as optical disks and magneto-optical disks have a spiral or concentric recording track on a signal recording surface, or a plurality of recording tracks. It is designed to ensure that information signals are written and/or output continuously. The optical pickup device that writes and/or reads information signals along the recording track onto the disk-shaped recording medium follows eccentricity and so-called surface wobbling of the disk-shaped recording medium that is rotated. Therefore, the optical beam is always focused on the recording track. Therefore, in the disk-shaped recording medium, the beam substrate formed by the condensed light beam moves with respect to the disk-shaped recording medium so as to follow the recording trunk. By the way, in the case where the recording track is formed in a spiral shape, the number of turns of the spiral formed by the recording trunk formed on one disc-shaped recording medium is extremely large. The disc-shaped recording medium is arranged in a circumferential direction, and in the radial direction of the disc-shaped recording medium, a plurality of recording tracks are arranged close to each other in parallel. If there are multiple recording trunks arranged in concentric circles,
These recording trunks are formed in the circumferential direction of the disk-shaped recording medium, and since the number of recording trunks formed on one disk-shaped recording medium is extremely large, the diameter of the disk-shaped recording medium is Multiple recording trunks are arranged close to each other in the direction. Conventionally, for recording tracks arranged close to each other in the radial direction of a disk-shaped recording medium,
A so-called multi-beam type optical pickup device has been proposed, which focuses multiple light beams on multiple locations to speed up the writing and/or reading of information signals. That is, as shown in FIG. 7, this optical pickup device includes a so-called multi-beam laser element l that emits a plurality of light beams, and the plurality of light beams emitted from the multi-beam laser element l are passed through a collimator. The light is condensed onto the disc-shaped recording medium 5 through predetermined optical devices such as a lens 2, a beam splitter 3, and an objective lens 4. As shown in FIG. 8, the multi-beam laser device 1 has a plurality of semiconductor layers 7 formed in parallel on a semiconductor substrate 6 to form a plurality of resonators for laser oscillation. Laser oscillation is performed in each semiconductor layer 7. This multi-beam laser device 1 emits a plurality of laser light beams 8 having intervals corresponding to intervals Pt shown by arrows PL in FIGS. 7 and 8 between the respective semiconductor layers 7. The distance PL between each of the semiconductor layers 7 is, for example, 50μ.
The thickness is approximately 100 μm. The plurality of light beams 8 emitted from the multi-beam laser element 1 are converted into parallel light beams 14 by the collimator lens 2, and then passed through the beam splitter 3 and the objective lens 4 into a 9th parallel light beam 14.
As shown in the figure, a plurality of beam spots 9 are formed by being condensed onto recording tracks TI formed on the disk-shaped recording medium 5, respectively. This optical pickup device is arranged such that a plurality of beam spots 9 are arranged in the radial direction of the disk-shaped recording medium with an interval between adjacent recording tracks TIl as indicated by arrows Pt in FIG. It has been done. Therefore, in this optical pickup device, information signals can be written and/or read simultaneously to a plurality of adjacent recording tracks Tm, and the writing and/or reading speed is increased. In this optical pickup device, as shown in FIG. Difference in incident angle to collimator lens 2 θ1θL=Pt/fc ・・・・・・
...is shown by (the first equation). Then, the objective lens 4
Let f0 be the focal length of the disc-shaped recording medium 5.
Arrow ρ in FIGS. 7 and 9 above. The interval p0 between each of the beam spots 9 shown above is pO=θL fo
...... (2nd equation), and by substituting the above 1st equation into this 2nd equation, Po = PL fo
/ re ...... can be shown as (3rd formula). Here, r. /r. When expressed as the forward optical path magnification θ, it is expressed as PG'''PLβL (4th formula).In this optical pickup device, the reflection from the disk-shaped recording medium 5 is The light beam returns to the beam splitter 3 via the objective lens 4, is reflected by the beam splitter 3, and enters the detection lens 10.The reflected light beam I transmitted through the detection lens 10
6 is a light receiving surface 1 divided into a plurality of parts of the photodetector l1.
The light is focused on 1a. Here, the focal length of the detection lens 10 is f. Then, the interval p9 between the reflected light beams 16 focused on the light receiving surface 11a indicated by the arrow Pl1 in FIG. 7 is expressed as pO'θLrn (5th equation) , by substituting the above first equation into this fifth second, we get P
a = pLrD/fc ......It can be expressed as (6th formula). Here, t o / (c is the return optical path magnification β. When expressed together, it is expressed as PEl=PLβD (Equation 7). D. Problems to be Solved by the Invention By the way, In the optical pickup device as described above, in a state where information signals can be written and/or read,
In order to improve the recording density of this information signal in the track direction of the recording tracks T, it is necessary to shorten the length of the beam spot 9 in the track direction of the recording track TI, which is indicated by arrow l in FIG. It is. However, the cross-sectional shape of the light beam 8 emitted from the multi-beam laser element l used in this optical pickup device is an ellipse whose major axis is in the direction of the meridional plane, as indicated by arrow M in FIG. Then, each of the light beams 8
are arranged in the sagittal plane direction shown by arrow S in FIG. Therefore, as shown in FIG. 9, the beam spot 9 formed on the disk-shaped recording medium 5 is located approximately on the recording track T. It is shaped like an ellipse with the major axis pointing toward the trunk. This is because the beam spot created when the light beam is focused by a lens is so-called diffraction limited.
This is because the larger the diameter of the light beam and the shorter the wavelength of the light beam, the smaller the focus can be. In the multi-beam laser device 1, it is difficult to generate a light beam having a circular cross section, and it is also difficult to shorten the oscillation wavelength. Therefore, in this optical pick amplifier device, it is difficult to shorten the length of the beam spot 9 in the track direction of the recording track T. In addition, in this optical start-up device, further speeding up of writing and/or reading of information signals to and from the disk-shaped recording medium 5 is achieved by increasing the number of light beams 8 that are used at the same time. This can be achieved by increasing the number of beam spots 9. In order to increase the number of beam spots 9 formed on the disc-shaped recording medium 5 through the objective lens 4, it is necessary to widen the field of view of the objective lens 4. However, widening the field of view of this objective lens 4
This makes the design and manufacture of this objective lens 4 difficult. -4. By shortening the interval p0 between the beam spots 9, the number of beam spots 9 formed on the disk-shaped recording medium 5 can be increased without widening the field of view of the objective lens 4. can. According to the fourth equation, the distance p0 between the beam spots 9 can be shortened by lowering the forward optical path magnification β, or by shortening the distance PL between the semiconductor layers 7.
In order to lower the forward optical path magnification β1, it is necessary to lengthen the focal length f of the collimator lens 2 or shorten the focal length #r0 of the objective lens 4. However, if the focal length Mrc of the collimator lens 2 is increased, the utilization efficiency of the light beam 8 will decrease, and there is a possibility that writing and/or reading of information signals may not be performed satisfactorily.
Moreover, if the focal length Mf0 of the objective lens 4 is shortened,
This objective lens 4 becomes difficult to design and manufacture, and
The so-called working distance between the objective lens 4 and the disc-shaped recording medium 5 is reduced, and there is a risk that the objective lens 4 and the disc-shaped recording medium 5 may come into contact with each other and cause damage to each other. Further, reducing the distance p between the semiconductor layers 7 makes it difficult to manufacture the multi-beam laser device 1. Furthermore, when the interval PL between the semiconductors N7 is shortened, the photodetector 1l that detects the reflected light from the disk-shaped recording medium 5 can separate and detect the reflected light from each beam spot 9. becomes difficult. That is, from the seventh equation above, the return optical path magnification β. is constant and the distance pL between the respective semiconductor layers 7 is shortened, the distance p. between the reflected light beams focused on the light receiving surface 11a becomes smaller. In order to separate and detect these reflected light beams, it is necessary to divide the light-receiving surface 11a into smaller parts to miniaturize the photodetector 11. Makes manufacturing difficult. In addition, when the distance p between the respective semiconductor layers 7 is shortened, in order to separate and detect the reflected light from the respective beam subtypes 9 without miniaturizing the photodetector 11, the seventh From the formula, by increasing the focal length f of the detection lens 10,
The above return optical path magnification β. It is necessary to make it larger. When the focal length Mrn of the detection lens 10 is increased, the structure of the optical pickup device becomes larger. Therefore, the present invention is proposed in view of the above-mentioned circumstances, and does not make it difficult to design and manufacture multi-beam laser elements, objective lenses, and photodetectors, and also improves the efficiency of using light beams. It is possible to improve the recording density of information signals that can be written and/or to continuously output them, and to further speed up the writing and/or reading of information signals without decreasing the size of the device or increasing the size of the device configuration. The purpose is to provide an optical pickup device that can perform E. Means for Solving the Problems In order to solve the above problems and achieve the above objects, an optical pink-up device according to the present invention has a plurality of laser light sources and a plurality of light beams emitted from these laser light sources. This is an optical pickup device that focuses light onto a recording medium, and has an anamorphic prism arranged in the optical path of the light beam from the plurality of laser light sources to the recording medium. Further, in the optical pickup device according to the present invention, in the optical pickup device, the anamorphic prism is arranged between the optical device and the recording medium for guiding reflected light from the recording medium to the photodetecting means side. It is something that has been done. F. Function: In the optical big amplifier device according to the present invention, a plurality of light beams emitted from a laser light source are expanded in diameter in a predetermined direction by an anamorphic prism. Moreover, the difference in the incident angles of the plurality of light beams with respect to the recording medium is reduced by the anamorphic prism. Further, in the optical pickup device according to the present invention, when the anamorphic prism is disposed between the optical device and the recording medium for guiding the reflected light from the recording medium to the photodetecting means side, the light is incident on the recording medium. Since the light beam and the reflected light from the recording medium each pass through the anamorphic prism once, the difference in the angle of incidence of the plurality of reflected lights from the recording medium to the light detection means is made small. Never. G. EXAMPLES Hereinafter, specific examples of the present invention will be described with reference to the drawings. The optical start-up device according to the present invention focuses a plurality of light beams at a plurality of locations on a recording track disposed close to each other on a disk-shaped recording medium, for example. This is a so-called multi-beam type optical bin amplifier device that is configured to write and/or output information signals by emitting light. As shown in FIGS. 1 and 2, this optical start-up device includes a so-called multi-beam laser element 1 that serves as a plurality of laser light sources that emit a plurality of light beams. It is configured to condense a plurality of emitted light beams onto a recording medium 5 via a collimator lens 2, a beam splitter 3, an anamorphic ink prism l2, and an objective lens 4. As shown in FIG. 8, the multi-beam laser device 1 has a plurality of semiconductor layers 7 formed in parallel on a semiconductor substrate 16, thereby constructing a plurality of resonators for laser oscillation. It will become something. This multi-beam laser element 1 is configured so that laser oscillation is performed in each of the semiconductors N7. This multi-beam laser element 1 is
A plurality of laser beams 8 are emitted at intervals corresponding to the intervals PL shown by arrows PL in FIGS. 2 and 8 between the semiconductors N7. The spacing PL between the semiconductors N7 is, for example, about 50 μm to loollm. Also,
The cross-sectional shape of each light beam 8 emitted from this multi-beam laser element I is an ellipse whose major axis is in the meridional plane direction shown by arrow M in FIG.
are arranged in the sagittal plane direction shown by arrow S in FIG. A plurality of light beams 8 emitted from the multi-beam laser device 1 are incident on the collimator lens 2 and are converted into parallel light beams 14. At this time, each of the light beams 8
The difference θ, in the angle of incidence with respect to the collimator lens 2 is:
Assuming that the focal length of the collimator lens 2 is f, θt=I)t/fc (8th equation)
Expression). Each of the parallel light beams 14 that has passed through the collimator lens 2 passes through the beam splitter 3 and enters the anamorphic prism l2. As shown in FIG. 3, the anamorphic prism 12 is a columnar prism with a wedge-shaped cross section made of glass or the like having a predetermined refractive index n. 2 faces l2b. That is, these first and second surfaces 12a and 12b face each other at an included angle α shown by arrow α in FIG.
It is said that The first surface 12 of this anamorphic prism 12
A, a parallel light beam 14 whose beam diameter in the plane direction perpendicular to the intersection line of the first surface 12a and the second surface 12b is L as shown by the arrow L in FIG. When incident at T, the diameter of the cross section of the parallel light beam 14 through the first surface 12a in the plane direction perpendicular to the line of intersection between the first surface 12a and the second surface 12b is L/Cosγ. ．． Then, assuming the refractive index of air to be 1, Sin r / Sin α = n
If the incident angle T is appropriately adjusted so that It passes through. At this time, the diameter of the cross section of the light beam 14 taken by the second surface 12b in the plane direction perpendicular to the line of intersection between the first surface 12a and the second surface 12b is LCOSα
/Cosy. That is, the traveling light beam 14 passes through the anamorphic prism l2, so that the diameter in the plane direction perpendicular to the line of intersection of the l-th surface 12a and the second surface 12b becomes (Cosα/ Cosγ) times. The ratio of diameter expansion of the parallel light beam 14 by this anamorphic prism 12 (Cosα/Cosγ)
is the diameter expansion magnification β. It is defined as Further, the first surface 12a
The direction of the intersection between the second surface 12b and the second surface 12b is defined as the diameter expansion direction of the anamorphic prism 12. Note that the beam diameter of the parallel light beam 14 is not changed in the direction of the intersection between the first surface 12a and the second surface 12b. As for the light beam that enters the anamorphic prism l2 at an angle shown by the arrow θ in FIG. 3 with respect to the light beam 14, that is, at an incident angle (γ+θL), The angle of refraction on the first surface 12a is (α+φ), the angle of incidence on the second surface 12b is φ, and the angle of refraction on the second surface 12b is θ.
．． Then, nSin(α+φ) =Sin( r+θ
L), so n SinφCosα+n Sinα# Sinγ+C
os 7θL, and nφ# (Cos 1 / Cos ex ) θL. And (Cosα/COST)=β. and the refraction angle θ. at the second surface 12b. Since θAξnφ, θA! =iθL/β.・・・・・・・・・(9th
formula). Therefore, each of the parallel light beams 14 transmitted through the anamorphic prism 12 has a difference in incident angle with respect to the objective lens 4 as indicated by the arrow θ in FIG. It is incident at an angle θ, as shown in . As shown in FIG. 4, each of the parallel light beams 14 incident on the objective lens 4 is condensed onto a recording track T formed on the disk-shaped recording medium 5 to form a plurality of beams. Observe spot 13.

This optical pickup device has a plurality of beam boxes
3 is the fourth in the radial direction of the disk-shaped recording medium.
Adjacent recording track T indicated by arrow p in the figure. They are arranged so that they are arranged with intervals between them. Therefore, in this optical pink-up device, information signals can be written and/or read simultaneously to a plurality of adjacent portions on the recording track T, and this writing and/or successive reading is accelerated. Further, in this optical pickup device, the anamorphic prism 12 is arranged so that the sagittal plane direction of each of the light beams 8 coincides with the diameter expansion direction of the anamorphic prism 12. The anamorphic prism 12 has a diameter expansion magnification β. is the beam shape of each parallel light beam 14 after passing through this anamorphic prism 12, and the diameter in the meridional surface direction of each parallel light beam 14 before entering this anamorphic prism 12 is defined as the diameter. It is set to be approximately circular. Therefore, each of the parallel light beams 14 is well focused by the objective lens 4, and the length of the beam spot l3 shown by arrow lA in FIG. 4 in the track direction of the recording track Tm is shortened. Therefore, in this optical backup device, it is possible to further improve the recording density of information signals that can be written to and/or read from the recording medium. Here, if the focal length of the objective lens 4 is f0, then
An interval P between each of the beam spots 13 on the disc-shaped recording medium 5, indicated by an arrow pA in FIGS. 2 and 4.
A is p^=θ^fO (Equation 10)
By substituting the above 8th and 9th equations into this 10th equation, Pa""fo θL/β. =foPL/fcβ^... (11th equation), and when ro/rc is expressed as forward optical path magnification β, p^=PtβL/βtodo (12th equation) It can be shown as. By the way, as shown in the fourth equation, the distance p between each beam spot when the anamorphic prism 12 is not used. was PL βL. That is, in this optical pickup device, the distance between each of the beam spots 13 is p. is reduced to 1/β by the above anamorphism 12. Therefore, in this optical start-up device, it is possible to capture a larger amount of beam subwoofer l3 within the predetermined field of view of the objective lens 4. Therefore, in this optical pickup device, it is possible to write and/or output information signals even faster. As described above, the shape of each parallel light beam 14 incident on the objective lens 4 is circular, and the difference in the angle of incidence of these parallel light beams 14 on the objective lens 4 is defined as the angle. θ． In order to achieve this, the anamorphic prism 12 may be placed between the collimator lens 2 and the beam converter 3, as shown in FIG. That is, the anamorphic prism 12 may be placed anywhere in the optical path of the parallel light beam 4 from the multi-beam laser element 1 to the recording medium 5. In the optical pickup device shown in FIGS. 1 and 2, each reflected light beam from the disc-shaped recording medium 5 at each beam spot I3 passes through the objective lens 4 and the anamorphic prism l2. The beam returns to the beam splitter 3 via the beam splitter 3. The difference in the exit angle from the anamorphic prism 12 between these reflected light beams is:
This anamorphic prism I2 is connected to the objective lens 4
By transmitting from the side, the angle θ becomes equal to the difference in the incident angle of each of the parallel light beams 14 to the collimator lens 2. The reflected light beam returned to the beam splitter 3 is
The light beam is reflected by the beam splitter 3 and enters the detection lens lO, which constitutes the light detection means. This detection lens 1
The reflected light beam 16 that has passed through the detection lens 10
At the same time, the light is focused on the light-receiving surface 11a, which is divided into a plurality of parts, of the photodetector 11 that detects the light detecting means. Here, if the focal length of the detection lens 10 is f, then the distance p between the reflected light beams l6 condensed on the light receiving surface 11a is indicated by the arrow PD in FIG. is expressed as pD=θL fD (13th equation), similar to the above 5th equation, and by substituting the above 8th equation into each 13th equation, PD = Pt fe / fc ”・”・(14th
It can be shown by the following formula. Here, f e / f c
is the return optical path magnification β. Similarly to the seventh equation, T3o=pLβD (15th equation). That is, in this optical pickup device, by using the anamorphic prism 12,
The interval pll between the reflected light beams 16 focused on the light receiving surface 11a is not changed. therefore,
In this optical pickup device, the photodetector 1
It is possible to easily separate and detect the plurality of reflected light beams 16 from the recording medium 5 without making the structure of the recording medium 1 finer or increasing the return optical path magnification βD. In addition, in the optical pickup device shown in FIG.
Since each of the reflected light beams 16 does not pass through the anamorphic prism 12, the difference in the light incident on the detection lens 10 between these reflected light beams 16 is at an angle θ. The reflected light beam 16 focused on the light receiving surface 11a is
The interval Pa between the
6). That is, this interval PD is p, =θtfe/β^ =PL fo/fc β. = pLβ, /β^ ......(Equation 17),
IrfI and 1/β of the distance pD between the reflected light beams l6 focused on the light receiving surface 11a in the optical pickup device shown in FIG. It can be doubled. Note that the optical start-up device according to the present invention is not limited to the configuration shown in the above-described embodiment, and instead of the anamorphic prism 12 described above, as shown in FIG. Second anamorphic prism 15a, 15
It is also possible to use a composite prism 15 in which the prisms b are stacked one on top of the other. Each of the anamorphic prisms 15a and 15b constituting the composite prism 15 is arranged so that its diameter expansion direction coincides with the sagittal plane direction of each of the thousand line light beams 14. In this case, the diameter expansion magnification of one of the first and second anamorphic prisms 15a and 15b forming the composite prism 15 is β. If so, the diameter expansion magnification due to passing through this composite prism 15 is β.
′. Therefore, this diameter expansion magnification β1' is the diameter expansion magnification β1 of the anamorphic prism l2 in the above embodiment.
of each anamorphic prism 15a. 15b, an optical pink-up device similar to the optical pink-up device in the embodiment described above can be constructed. Further, the first and second anamorphic prisms 1
As shown in FIG.
When the anamorphic prisms 15a and 15b are arranged so that the intersection line between the first surface and the second surface is on opposite sides of the light beam, the change in the traveling direction of the light beam due to each anamorphic prism 15a, 15b is It is canceled out. Therefore, in this case, the components from the multi-beam laser element 1 to the objective lens 4 can be arranged substantially in a straight line, making it easy to downsize the apparatus. H. Effects of the Invention As described above, in the optical pickup device according to the present invention, the plurality of light beams emitted from the laser light source are
The diameter is expanded in a predetermined direction by an anamorphic prism. Therefore, in this optical pickup device, by arranging the anamorphic prism in a predetermined direction, the beam shape of the plurality of light beams can be corrected to a substantially circular shape, and this light beam is directed onto the recording medium. This allows the light to be well focused. therefore,
In this optical pink-up device, it is possible to further improve the recording density of information signals that can be written to and/or read from the recording medium. Moreover, the difference in the incident angles of the plurality of light beams with respect to the recording medium is reduced by the anamorphic prism. Therefore, in this optical pickup device, when condensing the above-mentioned light beam using the objective lens, it is possible to simultaneously converge the light beam without expanding the field of view of the objective lens or without bringing multiple laser light sources closer together. By increasing the number of usable light beams, it is possible to increase the number of beam spots simultaneously formed on the recording medium. Furthermore, at this time, the utilization efficiency of the light beam is not reduced. Therefore, in this optical big absorber, it is possible to further increase the speed of writing and/or reading information signals. And in the optical pickup device according to the present invention,
When the anamorphic prism is placed between the recording medium and an optical device for guiding the reflected light from the recording medium to the photodetecting means side, the light beam incident on the recording medium and the reflected light from the recording medium are combined. Since each of the reflected lights passes through the anamorphic prism once, the difference in the angle of incidence with respect to the light detection means between the plurality of reflected lights from the recording medium does not become small. Therefore, in this optical pickup device, for example, the structure of the photodetector constituting the photodetection means is not made finer, and the lateral magnification of the photodetector is not increased. Multiple reflected lights from the recording medium can be easily separated and detected. That is, the present invention can be achieved without complicating the design and manufacturing of a plurality of laser light sources including multi-beam laser elements, objective lenses, photodetectors, etc., and without reducing the utilization efficiency of light beams. Furthermore, the optical pickup can improve the recording density of information signals that can be written and/or read without increasing the size of the device structure, and can achieve even faster writing and/or reading of information signals. The equipment can be provided. 4.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the arrangement of optical devices that make up the optical pickup device according to the present invention, and FIG. 2 schematically shows the arrangement of the optical devices that make up the optical pickup device. FIG. Figure 3 is an enlarged side view showing the shape of the anamorphic prism that monitors the above-mentioned optical pickup device. FIG. 4 is an enlarged plan view schematically showing the state of the beam spot formed on the recording medium by the optical pickup device. FIG. 5 is a side view schematically showing another example of the arrangement of the optical devices that monitor the optical pickup device. FIG. 6 is an enlarged side view showing another example of the shape of the above-mentioned anamorphic prism. FIG. 7 is a side view schematically showing the arrangement of optical devices that make up a conventional optical pickup device. Figure 8 is an enlarged perspective view schematically showing the structure of a multi-beam laser device. FIG. 9 is an enlarged plan view schematically showing the state of a beam spot formed on a recording medium by the conventional optical pickup device. 1. ．． ．． ．． ．． ．． ．． ．． ．． ．． Multi-beam laser element 3...
・・・・・・・・・Beams Blizzard 5・・・・・・・・・
...Recording medium 8...Light beam 0...Detection lens 1...Photodetector 2... ...Anamorphic prism 4.
・・・・・・・・・Parallel light beam 5・・・・・・Composite prism

Claims (2)

[Claims] (1) An optical pickup device having a plurality of laser light sources and condensing a plurality of light beams emitted from these laser light sources onto a recording medium, the light reaching the recording medium from the plurality of laser light sources. An optical pickup device with an anamorphic prism placed in the optical path of the beam. (2) The optical pickup device according to claim 1, wherein the anamorphic prism is disposed between the recording medium and an optical device for guiding reflected light from the recording medium to the photodetecting means.