JPS632121A - Light source for information recording medium - Google Patents

Abstract

PURPOSE:To eliminate the need for position alignment between an erasure recording light source and a writing light source by arranging the light emitting regions of the 1st and 2nd laser elements on the same line in parallel with the array forming direction and arranging the light emitting regions of the 3rd and 4th laser elements at an equal distance from the straight line at the opposite side with respect to the straight line. CONSTITUTION:The lights emitted from 4 semiconductor laser elements 22 - 25 are focused onto an optical disk as four minute spots, the erasure/ recording minute spots and the read spot are projected onto the same information track and each one minute spot for position tracing is projected respectively to edges at both sides of the information track. The 1st semiconductor laser for erasing/recording information is arranged so that the minute spot by the light emitted from the 1st semiconductor laser element 22 is projected this side than the minute spot by the light emitted from the 2nd semiconductor laser element 23 for reading information at the end of the array 21 thereby attaining the reading in successing to a reading. Thus, the alignment of the light sources is not required.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a structure of a light source of an optical head device that erases, records, and reproduces information by irradiating light onto an information recording medium.

[Prior art and its problems]

Magneto-optical and phase-change optical disks are known as information recording media in which information is erased, recorded, and reproduced by irradiation with light.
The information track, which serves as the information recording section, is irradiated by focusing on a nearby minute spot. In the magneto-optical type, the directions of magnetization of the information recording medium in the erased state or recorded state are opposite to each other, so light is irradiated while applying a magnetic field in the direction corresponding to the direction of magnetization in each state to control the temperature of the information recording area. The information recording medium is magnetized in the direction of the magnetic field by raising it to near the Curie temperature to erase or record information.Also, when reproducing information, when linearly polarized light is reflected by a magnetic material, the polarization plane of the reflected light is Utilizing the Kerr effect, in which light rotates with respect to the polarization plane of incident light, reflected light is passed through an analyzer to detect light intensity signals corresponding to the rotation of the polarization plane, that is, the magnetization of the information recording medium. In the phase change type, information is erased or recorded by taking advantage of the fact that there is a reversible phase change between, for example, a crystalline state as an erased state and an amorphous state as a recorded state through heating by light irradiation. In the case of information reproduction, the intensity signals of light corresponding to information are detected by utilizing the difference in light reflectance between the crystalline state and the amorphous state. The 7th node serves as the optical nozzle for projecting light onto the optical disc.
The one shown in the figure is known. Light emitted from a semiconductor laser l as a light source for information reading becomes a parallel beam 13 by a collimating lens 2, passes through a diffraction grating 3, is separated into three beams by the diffraction effect, and is sent to a beam splinter 4.
and 7 are transmitted, reflected by a reflecting mirror 8, focused by an objective lens 9, and later projected onto an optical disk 12 as three minute spots 102, 103, and 104 shown in FIG. These minute spots 102.103.1
The light at 04 is reflected by the optical disk 12, travels backward through the objective lens 99 and reflection mirror 8, is reflected by the beam splinter 7, and enters the photodetector 11. For erasing and recording information, a semiconductor laser 5 is used as a light source for erasing and recording.
The light emitted from the is converted into a parallel beam by a collimating lens 6, reflected by a beam splitter 4, transmitted through a beam splitter 7, further reflected by a reflecting mirror 8, and focused onto an optical disk by an objective lens 9 to form a minute spot 1.
Since the 0 diffraction grating 3 projected as 01 is slightly inclined with respect to the plane perpendicular to the optical axis of the parallel light beam 13, the minute spots 101, 102, 103, and 104 are projected separately. Figure 8 shows a minute spot on the optical disc 12) 101°10
2) This shows the projection status of 103 and 104. minute spot 102°10 that is projected separately into three
3 and 104, the central minute spot 103 is projected onto the information track 15 for information reading, and the remaining minute spots 102 and 104 are respectively projected onto the information track 1.
5 to provide detection signals that accurately track the information track 15. Since the information grid 3 is given a slight inclination, the minute spot 1 for reading
03 is projected behind the micro spot 101 for erasing and recording with respect to the moving direction of the information track 15, and the recording state can be checked by reading immediately after recording. FIG. 9 shows the configuration of the photodetector 11. 6 photodetectors 1
It consists of numbers 11 to 116. The four photodetectors 111, 112, 113, and 114 in the center read g4@ based on the sum of these outputs, and also detect minute spots.
It is also detected that the throat 103 is accurately focused on the information track 15. If the image formation is accurate, a circular light 117 is projected onto the photodetectors as shown in the figure, and the output of each photodetector is equal; if the imaging is not accurate, an elliptical light 118 is projected as shown by a broken line.
Alternatively, 119 is projected and the outputs of each detector become uneven, so each detector is also connected differentially to detect the degree of unevenness. Further, the photodetectors 115 and 116 on both sides detect the reflected lights 108 and 109 from the minute spots 102 and 104, and give equal outputs when the information trunk is accurately tracked. Therefore, the servo system including the above-mentioned photodetector can always give the optical head an optimal position. As mentioned above, the optical head has two light sources: the semiconductor laser 1 as a light source for reading the optical axis, and the semiconductor laser 5 as a light source for erasing and recording information, and the beam splitter 4.
On the other hand, the light beams from the semiconductor lasers 1 and 5 must be projected onto the information trunk 15 with a width of about 1μ on the optical disk 12.
The information track can be tracked as a minute spot 103 with 02 and 104, but the semiconductor laser 5 is used to project the minute spot 101 with the same precision.
The alignment of the beam splitter 4 and semiconductor laser 5
Since there is a certain distance between the two semiconductor lasers, it is not easy to adjust the positions of the two semiconductor lasers when assembling the optical head, and it requires a considerable amount of time and effort.

[Purpose of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a light source that does not require alignment of an erasing/recording light source and a reading light source when assembling an optical head.

[Key points of the invention]

This invention provides a light source for an optical head that includes a first semiconductor laser element as a light source for erasing and recording information, a second semiconductor laser element as a light source for reading information, and a light source for accurately tracking information tracks. The third and fourth semiconductor laser elements are arranged in an array and integrated, and the light emitting areas of the first and second semiconductor laser elements are aligned in the direction of forming the array. The light emitting regions of the third and fourth semiconductor laser elements are arranged on the same parallel straight line, and the light emitting regions of the third and fourth semiconductor laser elements are arranged on opposite sides of the straight line and equidistant from the straight line, and the distance is at least as long as the information track of the optical disk. The ratio of the focal length of the collimating lens, which is a lens system that converts the light from the light source into a parallel beam over a length equivalent to approximately half the width, to the focal length of the objective lens, which is a lens system that focuses the beam onto the optical disk. The light is focused as it is as four minute spots, and the minute spots for erasing and recording and the spot for reading are on the same information track, and on the edges on both sides of the information trunk. Microscopic spots for position tracking are projected one by one. It is arranged at the end of the array so as to be projected in front of the minute spot of the first semiconductor light for erasing and recording information, and enables reading (reading) subsequent to recording.

[Embodiment of the invention] FIG. 1 shows an embodiment of the invention, in which a semiconductor laser array 21 includes four semiconductor laser elements 22) 23.
．． 24 and 25 are integrated by placing kfi[i26 between each element, and the negative electrode 27 of each element is soldered to a metal mount 28. A semiconductor laser element 22 projects erasing and recording light, 24 projects reading light, and 23 and 25 project information track tracking lights, respectively. In this embodiment, the semiconductor laser elements are arranged in a direction parallel to the active layers 221, 231, 241, and 251 to form an array. In addition, the active layers 221 and 2
The heights of 31, 241, and 251 from the negative electrode 27 side are equal for the semiconductor laser elements 22 and 24, and are equal for 23, and the width A'' of the information trunk 15 of the optical disk 12 is approximately half the length. On the other hand, it is approximately equal to the ratio of the focal length of the collimating lens 41 and the focal length of the objective lens 45 in the optical system of the optical head shown later in FIG. 3.The activity of each of the semiconductor laser elements described above is Each light emitting area 2 in 1221.231.241.251
22.232.242.252 The light from the 0 light emitting area 222 is used for erasing and recording, and when erasing, a constant amount of light is given, and when recording, it is modulated according to the type of information. The reading light from one light emitting region 242 and the information track tracking light from the light emitting regions 232.degree. FIG. 2 shows an example in which the semiconductor laser array 21 of FIG. 1 is housed in a sealed container 29 to constitute a light source unit. Semiconductor laser array 2
1 mount 28 is supported by a support body 30. Light to the optical disc is projected through the window 31 in the direction of the arrow. On the opposite side of the semiconductor laser array 21 from the window 31, there is a photodetector 32 composed of four photodetecting elements, which detects the light projected from the semiconductor laser array 21 to the photodetector 32 side as well. , provides a signal for controlling the amount of light emitted from each semiconductor laser element. In particular, the semiconductor laser elements 23 and 25, which project light for tracking the information track, are also controlled so that the amounts of light emitted are equal. FIG. 3 is a configuration diagram of an optical system of an optical head using the semiconductor laser array 21 according to the present invention as a light source. The light emitted from the semiconductor laser array 21 is turned into a parallel beam 42 by the collimating lens 41, passes through the beam splitter 43, is reflected by the reflection mirror 44, and is focused by the objective lens 45 to form four minute spots on the optical disk 12 as shown in FIG. It is projected as 121.122.123.124. These minute spots 121.122°123, 124
The light emitting areas 222, 232, 242, and 252 of the semiconductor laser array 21 shown in FIG.
It is an image formed by The moving direction of the optical disc is the direction of the arrow, so the minute spot 121 is for erasing and recording, the spot 123 is for reading and is on the information track 15 to enable reading after recording, and the spots 122 and 124 are for tracking the information track 15. 15 information tracks each for
on the edges on both sides of. As a result of the above, the arrangement pattern of the light emitting region 222, 232) 242, 252 of the semiconductor laser array 21 and the minute spot 121, 122, 1
The positional relationship between 23 and 124 is similar, and the ratio between the two is equal to the ratio of the focal length of the collimating lens 41 and the focal length of the objective lens. This is the reason why the position is determined by the width of the information track 15 and the above ratio.The minute spot 121.
122, 123, and 124 are formed by the projected light from the integrated semiconductor laser array 21, so when the information track 15 is accurately tracked by the reflected light from the minute spots 122 and 124, the semiconductor laser array 210
Micro-spots 7) 121 for erasing and recording and micro-spots 12 for reading corresponding to the arrangement pattern of the light-emitting area.
3 is necessarily located on the information track 15, so there is no need to align the erasing and recording light source with the reading light source when assembling the optical system, as in the prior art. Spot 122.12
3. The reflected light from 124 travels the optical path backwards and returns to the third
The light passes through the objective lens 459 shown in the figure and the reflection mirror 44, is reflected by the beam subrifter 43, and enters the photodetector 46. The light detection section 46 is configured almost in the same manner as in the prior art, and performs reading of information, accurate detection of imaging state, and detection of accurate tracking state of the information track. As mentioned above, in this invention, the erasing/recording light source and the reading light source are not placed at different positions, so
There is no need to align these two light sources at all, and the trouble of alignment can be saved.In addition, the semiconductor laser 5. shown in FIG. The collimating lens 6 and beam splinter 4 are no longer required, and since the semiconductor laser array 21 is also equipped with a light source for tracking the information trunk 15, the diffraction grating 3 is no longer necessary, and the number of optical components that require a certain size can be reduced. This allows the optical head to be made smaller and lighter. In this embodiment, it is necessary to adjust the active layer of the semiconductor laser element so that it is located at the required location, but this is done at the manufacturing stage of the semiconductor laser array 21.
The adjustment accuracy does not pose a problem to the manufacturing accuracy of semiconductor devices. FIG. 5 shows a different embodiment of the present invention, in which four semiconductor laser elements 51 of the same shape are used instead of using semiconductor laser elements with different active layer positions for each element, and a metal mount is used. The active layer of each element is positioned by metal spacer layers 53 and 54 of different thicknesses on 52;
A negative electrode 55 of each semiconductor laser element is soldered to these to form a semiconductor laser array 56. This embodiment has the advantage that there is no need to manufacture devices with different specifications for each device, and mass-produced devices can be used as they are. It is necessary to adjust the position of the active layer by adjusting the thickness of the spacer layers 53 and 54, but this is an adjustment work at the manufacturing stage of the semiconductor laser array 56, which is easy to modify.
This is extremely easy compared to the labor involved in operating optical systems, where even slight positional or angular shifts can cause large errors. FIG. 6 shows a third embodiment of the invention. In this example, four semiconductor laser elements 61.62°6
3 and 64 are arranged in a direction perpendicular to the direction of the active layer to form a semiconductor laser array 60. Semiconductor laser element 6
1 is for erasing and recording, 63 is for reading. 62 and 64 are for information trunk tracking. The position of the light emitting region 611.621.631.641 of each element is adjusted by electrically insulating spacer layers 65, 66, 67,
The light emitting regions 611 and 631 are arranged on the same straight line parallel to the arrangement direction of the semiconductor laser elements, that is, perpendicular to the direction of the active layer.
are arranged on opposite sides to the straight line and equidistant from the straight line, and the distance is approximately half the width of the information track 15 of the optical disc 12, and the optical disc shown in FIG. It is approximately equal to the ratio of the focal length of the collimating lens 41 and the focal length of the objective lens 45 in the optical system of the head, and the semiconductor laser element 61
Negative i! Pole 612 and negative electrode 62 of semiconductor laser element 62
2, the positive electrode 623 of the semiconductor laser element 62, 63
．． 633 and the negative electrode 632 of the semiconductor laser element 63.64
．． 642, there is a foil-shaped metal lead electrode 68, respectively.
．． The electrodes are soldered to the positive and negative electrodes of each semiconductor element with 69 and 70 in between to form an array. Furthermore, spacer layer 6
A metal film 72 is formed on the side where 7 contacts the metal mount 71, and is fixed to the metal mount 71 by soldering. In this configuration, the mutual positions of the light emitting regions are adjusted by adjusting the thickness tlifJ of the spacer layer at the array manufacturing stage, and the steps are almost the same as in the second embodiment. Like the second embodiment, this embodiment also has the advantage of being able to use mass-produced elements as is, but since the active layer is perpendicular to the direction of the array, the distance between the active layer and the electrodes is An additional advantage is that the light emitting region can be set at a predetermined position even if the elements are unevenly aligned. Effects of the Invention In this invention, the light source of an optical head used in an information recording medium such as an optical disk that erases, records, and reads information by irradiation with light is configured in an array with four semiconductor laser elements. The two elements are arranged as an information reproducing/recording element and an information reading element so that their respective light emitting areas are on the same straight line parallel to the arrangement direction of the array,
Two other elements are disposed as light sources for tracking the information track of the optical disk, and are arranged on opposite sides of the straight line so as to be equidistant from the straight line, and the distance is at least approximately the width of the information track. It is approximately equal to the ratio of the focal length of the collimating lens that converts the light from the light source into a parallel beam for half the length to the focal length of the objective lens that focuses the said beam onto the information trunk of the optical disk. Therefore, on the information track of the optical disk, the pattern of the light emitting area of each semiconductor laser element whose relative position has been determined as described above is imaged as a minute spot, and the pattern is imaged as a minute spot for reproduction and recording of the collision 7) and for information reading. The microspot for tracking the information track is located on the information track, and the two microspots for tracking the information track are located on opposite edges of the information track to accurately track the information track. Since the predetermined light emitting area pattern is imaged on the information track in this way, when assembling the optical head, the erasing and recording light source and the reading light source, which are separately arranged as in the prior art, can be assembled. There is no need to perform alignment. Additionally, collimating lenses in the optical path of the erasing and recording light source and beam splitters that integrate the optical path and the optical path from the reading light source are no longer required, reducing the number of optical components and making the optical head more compact. Can be made lighter. Furthermore, since semiconductor laser arrays can be mass-produced, there is also a cost advantage due to the reduction in the number of optical components.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a sectional view of a light source unit, FIG. 3 is a block diagram of an optical system of an optical head according to an embodiment of the present invention, and FIG. 4 is an information track of an optical disc. 5 and 6 are configuration diagrams of different embodiments of the present invention, and FIG. 7 is a schematic diagram showing the relationship between +DINOn and the projection light according to the prior art. (The schematic diagram shown in FIG. 9 is a configuration diagram of the photodetecting section. 1.5: Semiconductor laser, 2, 6. 41: Collimating lens, 9. 457 Objective lens, 12: Optical disk, 13.
41+ line luminous flux, 15: information track, 21.56°60
Two semiconductor laser arrays, 22t 23.2L 25+
5L61, 62.63.647 semiconductor laser element, 22
1.231°241, 251: Active layer, 222.23
2.242.252.611゜621.631.641
= Luminous area. Figure 1 Figure 2 Beam splitter Figure 3 Figure 4 Figure 5 Vessel Figure 7 Figure 8

Claims (1)

[Claims] 1) In order to perform at least one of erasing and recording information on an information recording medium and reading information recorded on the information recording medium by irradiating light, the light emitted from the light source is parallelized. In an optical head device including an optical system including a lens system that produces a parallel light beam and a lens system that focuses and projects the parallel light beam onto an information recording medium, four semiconductor laser elements are arranged to form an array. The light-emitting regions in the active layer of the first semiconductor laser element that projects light for erasing and recording information and the second semiconductor laser element that projects light for reading information form an array. The information tracks of the information recording medium onto which the light for erasing and recording the information and the light for reading the information are projected are accurately tracked. Light-emitting regions in the active layers of the third and fourth semiconductor laser elements that project light for detecting that the light is being detected are located on opposite sides of the straight line and at equal distances from the straight line, A light source for an information recording medium, further comprising a first semiconductor laser element located at one end of the array. 2) In the device described in claim 1, the light emitting regions in the active layers of the third and fourth semiconductor laser devices and the light emitting regions in the active layers of the first and second semiconductor laser devices are located. The distance from the straight line is at least equivalent to approximately half the width of the information track of the information recording medium, and the focal length of the lens system makes the light a parallel beam, and the lens system converges and projects the parallel beam. A light source for an information recording medium, characterized in that the light source is approximately equal to the focal length multiplied by the ratio of the focal length of the light source. 3) The information recording medium according to claim 1, wherein the semiconductor laser elements forming the array are arranged in a direction parallel to the active layer of the semiconductor laser elements. light source. 4) The information recording medium according to claim 1, wherein the semiconductor laser elements forming the array are arranged in a direction perpendicular to the active layer of the semiconductor laser elements. light source.