JPS63224057A - Optical head device for information recording medium - Google Patents

Abstract

PURPOSE:To simplify constitution, and to improve an overwrite performance by performing the record and the erasure of an information to an information recording medium at one time and besides, independently, by means of using one piece of a single light source to project a straight polarized light continuously. CONSTITUTION:The single light source 22 to project the straight polarized light continuously, is used, and its optical path is divided by a non-polarized light beam splitter 25 as the first light flux dividing means, and one is as a recording optical path and the other as an erasing optical path, and the record and the erasure of the information are performed by one light source 22 at the same time. Accordingly, two fine spots 36, 35 for the record and the erasure can be cast closely to each other in the same information track of the informa tion recording medium. Thus, the overwrite that the record of the new informa tion in an erased part is performed immediately after the information, recorded in the information track, is erased, can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the configuration of an optical system of an optical head device that erases, records, and reproduces information by irradiating an information recording medium with light.

[Conventional technology]

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.
An information track serving as an information recording section is irradiated by focusing on a minute spot near the duck. In the magneto-optical type, the directions of magnetization of the information recording medium in the erased state or recording state flK 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. Erasing or recording information is done by increasing the temperature to nearly one Curie temperature and magnetizing the information recording medium in the direction of the magnetic field.Also, when reproducing information, when linearly polarized light is reflected by a magnetic material, reflected light is generated. Utilizing the Kerr effect, in which the plane of polarization rotates with respect to the plane of polarization of the incident light, when the reflected light is passed through an analyzer, the intensity signal of the light corresponding to the rotation of the plane of polarization, that is, the magnetization of the information recording medium, is detected. . In the phase change type, information is erased or recorded by utilizing a reversible phase change between a crystalline state as an erased state and an amorphous state as a recorded state through heating by light irradiation. When reproducing information, the light intensity signal corresponding to the information is detected by utilizing the difference in light reflectance between the crystalline state and the amorphous state.

FIG. 7 shows a conventional configuration of an optical system in an optical system used for irradiating light for erasing, recording, and reproducing information. The optical system of the optical head 1 includes a semiconductor laser 2
．． Collimating lens 6, Beam Sglyph 249 reflection mirror 5. It consists of an objective lens 6° and a light detection section 9. Of these, the reflecting mirror 5 and the objective lens 6 constitute a beam projection section. Linearly polarized light is projected from the semiconductor laser 2, and is adjusted into a parallel beam 10 by the collimating lens 3.
The beam passes through a beam splitter 4, is reflected by a reflecting mirror 5, and is formed by a focusing objective lens 6 to form a minute spot 8 on an information track (not shown) of an optical disk 7 as an information recording medium. The light reflected by the information track travels backward along the path described above, passes through the objective lens 6 and the reflection mirror 5, and is partially reflected by the beam smitter 4 and enters the photodetector 9, where the recorded information is recorded. Reproduce. In the case of a magneto-optical optical disc, an analyzer (not shown) is provided on the incident side of the photodetector 90. The light passing through this analyzer changes in intensity according to the rotation of the plane of polarization due to the Kerr effect mentioned earlier.
A photodetector detects the intensity signals of this light.

The optical head 1 containing the above-mentioned optical system is driven by a spindle motor 11 to track the information track of the optical disc 7, which rotates in the direction of the arrow, in the radial direction of the optical disc 7 as shown by the arrow in the figure, while tracking it by a servo mechanism (not shown). Move to. Further, the objective lens 6 is provided in an objective lens unit 12, and tracks the information track with higher accuracy by a servo mechanism, which is separate from the optical head 1 and is also not shown.

Figures 8 and 9 are information records! ! ! FIG. 8 is a plan view thereof, and FIG. 9 is a sectional view thereof. The minute spot 8 of light projected inside the groove-shaped information track 15 changes intermittently as the semiconductor laser 2 is controlled based on the information signal, so that the information is formed like pits 16 and 17. It is recorded as pits of various lengths depending on the Hereinafter, the pits 16 and 17 will be referred to as recorded 1°, and the unrecorded area between the pits will be referred to as recorded 0.

[Problem that the invention seeks to solve]

In the above configuration, when performing an override in which the pits 16 and 17 as information recorded on the information track 15 are erased and new information is recorded, the information track 15 is concentrically shaped because there is a single light source. After erasing information, the optical disc must rotate once and wait for the erased area to return to the position of the minute spot before starting recording. Further, in the case of an optical disk in which the information track 15 is formed in a spiral shape, recording cannot be started unless the information track 15 is jumped one rack after the disk rotates once as described above.

In order to perform an override using the conventional optical head using a single light source, the above-mentioned rotational waiting time is required, so new information is recorded while erasing previously recorded information. It is extremely difficult to perform a fast override. In contrast, it is conceivable to use two optical heads, one for erasing and one for recording and reproducing. However, in order to downsize the information recording and reproducing device, in addition to the optical head, the spindle motor 11 for driving the optical disk is installed in the limited space around the optical disk, which has a diameter of about 13 and is supported by a drive stand. A mechanical part such as a tracking mechanism including a motor to make the optical head track an information track, and a power supply part.

Electronic circuit sections such as an information signal amplification section and an optical head control section must be housed therein. Furthermore, in the case of using a magneto-optical optical disk, it is also necessary to house an electromagnet that applies a magnetic field in addition to the above. The size of the optical head is 1g12
．． Around 5 cIR, height around 2.5 csn.

It is extremely difficult to fit two optical heads into an information recording/reproducing device, which has a length of about six and whose width and depth are downsized to nearly the diameter of an optical disk.

The purpose of this invention is to enable high-speed override in which recording of prayer-like information is started immediately after erasing information without increasing the size of the information recording/reproducing device using one optical head using a single light source. There is a particular thing.

[Means for solving problems]

In order to solve the above problems, according to the present invention, in an apparatus for recording and erasing information signals on an information recording medium by irradiating light, a light source unit continuously projects linearly polarized light. A first beam splitting means is provided with a light source, and a first beam splitting means divides the incident linearly polarized light into five transmitted beams and a right-angled reflected beam; a first light beam reflecting means for reflecting in a direction; and changing the polarization plane of either the transmitted light beam or the reflected light beam to a polarization plane having a different inclination from the polarization plane depending on a power feeding method based on the information signal. a polarization plane changing means for emitting a polarized light beam, a second light beam splitting means for splitting a light beam having a specific polarization plane from an optical path of an incident light beam;
a first beam focusing means for converging the beam split by the beam splitting means of C2 and projecting it onto the recording portion of the information recording medium in the form of minute dots; a second luminous flux reflecting means for reflecting the other luminous flux which is not split by the second luminous flux splitting means in a direction substantially parallel to the luminous flux split by the second luminous flux splitting means; and a second light beam focusing means for projecting the light beam focused by the first light beam focusing means onto the same recording track in the form of a minute point in the vicinity of the projection point.

[Effect]

The function of this invention is that the 7Alade cell has a function of rotating the plane of polarization of the incident linearly polarized light at high speed according to the magnetic field generated by feeding the coil with which it is equipped, and the polarizing beam splitter rotates the plane of polarization of the incident linearly polarized light at high speed. Since it has the function of reflecting the light beam with the vertical polarization plane to the side and transmitting the light beam with the plane of polarization parallel to the plane of incidence, it is possible to combine the 7 Alladay cells and the polarizing beam splitter and to feed the power to the coil of the 7 Alladay cells. When modulated or on/off controlled by a binary recording signal, the polarization plane of the output beam of the Faraday cell changes in accordance with the recording signal, and the p1 polarizing beam splitter detects this change in the polarization plane and converts the incident beam. Focusing on the ability to achieve the function of a so-called optical switch synchronized with the recording signal, which splits the transmitted light beam and reflected light beam, the light source does not require modulation by the recording signal, so linearly polarized light is continuously projected onto the light source section. Semiconductor laser 1 as a single light source
splitting the linearly polarized light, which has been arranged into a parallel light beam by a collimating lens, into a transmitted light beam and a reflected light beam by a non-polarizing beam splitter serving as a first light beam splitting means;
The reflected light beam is changed into a reflected light beam parallel to the transmitted light beam by a reflecting mirror serving as a first light beam reflection means, and one of the two mutually parallel optical paths is provided with a polarization plane changing means consisting of the above-mentioned 7 Alade cells and a polarized light beam. A second beam splitting means consisting of a beam splitter is arranged, and the beam reflected laterally by the polarizing beam splitter (corresponding to record 1) is divided into the first
The light is focused by a recording objective lens as a light beam focusing means and projected as a minute spot of light onto the information recording section of an optical disk as an information recording medium, and the other of the two optical paths has a second light beam reflecting means. mirror and second
An erasing objective lens is arranged as a light beam focusing means, and the light beam is focused and projected onto the same information track as the recording light spot in close proximity to the projection position of the recording microspot. To simultaneously and independently project a recording minute spot and an erasing minute spot corresponding to a recording signal onto an information recording medium at positions close to each other using one single light source that continuously projects polarized light. and therefore allows for high-speed optical recording with one optical head device.
Z j can be done.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of the present invention, in which the optical system of the optical head 21 includes a light source section 24. Non-polarizing beam splitter 2
5. Photodetector 26. Faraday cell 28 with coil 27. Polarizing beam splitter 29. Recording objective lens 5
09 reflecting mirrors 31 and 32. Erasing objective lens 33
It is made up of. Semiconductor laser 2 as a single light source
2 continuously projects linearly polarized light, collimating lens 2
3, linearly polarized light 10Fi arranged into a parallel light beam, and a non-polarized beam splitter 25 as a first light beam splitting means.
Linearly polarized light 10 transmitted without changing the optical path
A and the laterally reflected light beam 10B are split. Faraday cell 28. A polarizing beam splitter 29 and a recording objective lens 30 are arranged to project the light beam onto the recording section B of the original disk 7, and the reflected light beam 1
There is a reflection mirror on the 0C side as a second beam reflection means! +
2. A projection section for projecting a light beam onto the erasing section A of the optical disk 7, which is composed of an erasing objective lens 63, is arranged.

The rotation direction of the optical disk 70 as an information recording medium is the direction of the arrow in the figure. Also, the coil 27 of the 7 Alade cell 28
The IC receives recording signals 1 and 0 from the electronic circuit side (not shown).
A current 1 is supplied which is controlled on and off in accordance with the current.

FIGS. 2 and 3 are schematic diagrams showing the operation of the embodiment device. Figure WJ2 shows the state of the luminous flux when erasing and recording information is being performed simultaneously! 1, the semiconductor laser 22 projects linearly polarized light 59 whose polarization plane is perpendicular to the plane of the paper, indicated by the symbol ■. This linearly polarized light 39 is arranged into a parallel light beam 40 by a frimate lens 23, and is split into a transmitted light beam 40A and a right-angled reflected light beam 40B by a non-polarized beam splitter 25. A reflected light beam 40C is parallel to . A Faraday cell 28 is arranged on the optical path of the transmitted light beam 40A. Coil 27 prepared for Faraday cell 28
A current 1, which is controlled on and off (by a signal obtained by inverting the recording signal), is supplied from an electronic circuit (not shown). When the current 1 flows through the coil 27, the polarization plane of the incident light beam 40A is rotated by 90@ in the 7Araday cell 28 due to the action of the magnetic field generated by the current 1, and the polarization plane of the incident light beam 40A is rotated by 90@ in the 7Araday cell 28. The light is emitted from the cell 28 and enters the polarizing beam splitter 29 . The polarizing beam splitter 29 transmits a beam whose polarization plane is parallel to the plane of incidence (marked ↑ in the figure), and reflects a beam whose polarization plane is perpendicular to the plane of incidence (marked O in the figure). In the case shown in the figure, the light beam passes through the polarizing beam splitter and is blocked from entering the recording objective lens 50@. Therefore, the recording portion B position of the information recording medium 7 onto which the light beam focused into a point by the recording objective lens 30 is projected remains in a state where the recording remains erased, that is, the recording is 0.

On the other hand, the reflected light beam 40C reflected by the reflection mirror 31 in a direction parallel to the transmitted light beam 40A is further reflected by the reflection mirror 32 in a perpendicular direction, and is focused by the erasing objective lens 36 to form the recording portion B of the information recording medium 7. A minute optical spot 35 is projected onto position A on the same track as the position, and the recorded information is erased.

FIG. 6 shows the state of the luminous flux when information erasing and recording 1 are being performed simultaneously. The erased state is the same as that already described with respect to FIG. In the case of FIG. 3, the coil 27 provided in the Faraday cell 28! t15! Since i is in an off state in which no light is flowing, no rotation of its polarization plane occurs in the incident light beam 40A.

Therefore, a light beam whose polarization plane is perpendicular to the plane of the paper (marked 0 in the figure) enters the polarizing beam splitter 29. Since this light beam is perpendicular to the incident plane of the polarizing beam splitter 290, it is reflected laterally by the polarizing beam splitter 29 and condensed by the recording objective lens 30, and is placed at the recording portion B position of the information recording medium 7 with a diameter of approximately 1 μ The information signal is recorded 1 by being projected as a minute spot 36 on the pallet.

Information may be reproduced using the recording optical path without power being supplied to the coil 27 of the 7Alade cell 28, or may be performed using the erasing optical path.

As described above, in this invention, a single light source 22 that continuously projects linearly polarized light is used, and its optical path is divided by the non-polarizing beam splitter 25 as a first beam splitting means, and one side is used as a recording optical path. , and the other as optical paths for erasing, it is possible to simultaneously erase and record information with one light source. Therefore, the distance between the two minute spots '56 and 35 for recording and erasing projected onto the same information track of the information recording medium 7 is such that the heating by the minute spots does not interfere with each other and the information recording medium is magneto-optical. In the case of a disk, recording and erasing can be made as close to each other as possible to generate magnetic fields in opposite directions. The two minute spots 35 and 36 can be brought close to each other by making the angle of inclination of the reflecting mirror 32, which serves as the second light beam reflecting means, relative to the light beam 40C adjustable. In addition, if the erasing and recording objective lenses 33 and 30t are configured to be integrated or shared, two minute spots 35 and 36
It is possible to bring them closer together.

In addition, there is a Faraday cell whose polarization plane rotates a minute recording spot in synchronization with the recording signal, and a polarization beam splitter which detects the rotation of the polarization plane and projects a beam corresponding to recording 1 toward the recording objective lens. Since I decided to perform intermittent control (always modulation control), I set up the recording signal room v4.
This can be done independently on the recording optical path side, and high-speed override can be performed to start recording immediately after erasing information.

4 and 5 are schematic diagrams showing different embodiments of the present invention. The configuration of the device is the same as that of the previous embodiment, but the plane of polarization of the linearly polarized light 49 projected from the semiconductor laser 42 is This shows an example in which the plane is parallel to the plane of paper (indicated by ↑ in the figure). In this case, contrary to the above-described embodiment, the current supplied to the coil 27 of the Faraday cell 28 is controlled to be on-off according to the recording signal (not inverted) K, and the recording O is as shown in FIG. As shown in FIG. 5, recording is performed with the current flowing through the coil 27 in the OFF state, and recording 1 is performed with the current 1 being supplied to the coil 27 as shown in FIG.

FIG. 6 is a block diagram showing another embodiment of the present invention, in which a transmitted light beam 40A is split by a non-polarizing beam splitter 25.
A reflecting mirror 32 and an erasing objective lens 33 are arranged on the side as an optical path for erasing, and a reflected light beam 40C@ reflected in a direction parallel to the transmitted light beam 40AK by the reflection mirror 31 is used as a recording optical path. ．． This embodiment differs from the previous embodiment in that a polarizing beam splitter 29° and a recording objective lens 30 are provided. Even when the optical head device 51 is configured in this way, the same functions as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, in this invention, the linearly polarized light from the light source is split into two light beams on the writing optical path side and the erasing optical path side by the first beam splitting means, and the light beam on the erasing optical path side is split into two beams on the recording optical path side and the beam reflecting means and the optical beam splitting means. The light beam on the recording optical path side is projected as a minute spot onto the erasing part of the information recording medium through a focusing means, and the light beam on the recording optical path side has a polarization plane changing means that changes the polarization plane in synchronization with the recording signal, and a light beam having a polarization plane corresponding to recording 1. A second beam splitting means divides the divided beam, and a beam focusing means converges the divided beam to project it as a recording minute spot onto the same information track as the erasing minute spot of the information recording medium. As a result, information can be recorded and erased on the recording medium simultaneously and independently using the divided light beams, and recording of minute spots for recording 1. Since the on/off control corresponding to recording OK is performed on the recording optical path side, there is no need to turn on and off the light source to control the recording minute spot on and off, and linearly polarized light is continuously projected. It is possible to simultaneously and independently record and erase information on an information recording medium using a single light source. Also, since recording and erasing can be done simultaneously and independently, there are two microslots for recording and erasing). I-High-speed override, which allows projections to be made close to each other within the same information track of an information recording medium, thus immediately starting recording new information in the erasing section after erasing the information recorded on the information track. It can be performed.

In this way, high-speed override can be performed using one single light source, so there are problems with the difficulty of high-speed override in the conventional technology, the complexity of the configuration due to the provision of two optical heads, and the need for installation space. It is possible to provide an optical head for information recording media that has almost completely eliminated problems, has a simple configuration, and has excellent high-speed override performance.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an optical system showing an embodiment of the present invention, and FIG.
3 and 3 are schematic diagrams showing the state of the luminous flux in the embodiment device, FIG. 4 and 5 are schematic diagrams showing the state of the luminous flux in different embodiments, and FIG. 6 is a configuration showing another embodiment. 7 is a configuration diagram of an optical system showing a conventional device, and FIG. 8 is a recording state of an information recording medium! 174, and FIG. 9 is a side sectional view of FIG. 8. 1.21.51... Optical head, 2... Semiconductor laser (on/off control), 5, 31.32... Reflection mirror (light beam reflecting means), 7... Optical disker (information recording medium) ), 24... Light source section, 25... Non-polarizing beam splitter (first beam splitting means), 28... 7 Alade cell (polarization plane changing means), 27... Coil, 29...
- Polarizing beam splitter (second beam splitting means), 3,
30.33...Objective lens (light focusing means), 15.
... Information track, 16, 17... Recording section (recording 1)
, 8, 55.16... minute spot. 2nd concavity 3rd figure 5th figure 4th figure 5th figure 8 center

Claims (1)

[Claims] 1) In a device that records and erases information signals on an information recording medium by irradiating light, the light source unit includes a single light source that continuously projects linearly polarized light; a first beam splitter that divides the linearly polarized light incident on the medium-projection unit into a transmitted beam and a right-angle reflected beam; and a first beam that reflects the orthogonally reflected beam in a direction parallel to the transmitted beam. a reflecting means, and a polarization plane changing means for changing the plane of polarization of either the transmitted light beam or the reflected light beam to a plane of polarization having a different inclination from the plane of polarization, depending on the method of power feeding based on the information signal, and outputting the polarized light beam. a second beam splitter that splits a light beam with a specific plane of polarization from the optical path of the incident light beam; and a second beam splitter that focuses the split light beam by the second light beam splitter to form a minute dot on the recording section of the information recording medium. a first light beam converging means for projecting a beam into a shape, and reflecting the other of the transmitted light beam or the reflected light beam, which is not polarized in the plane of polarization, in a direction substantially parallel to the light beam split by the second light beam splitting means. Second
a light beam reflecting means, and a light beam reflected by the second light beam reflecting means is focused on the first light beam on the same recording track as the recording section.
an optical head device for an information recording medium, comprising: a second beam converging means for projecting the beam in the form of a minute point close to a projection point of the beam condensed by the beam converging means; 2) An optical head device for an information recording medium according to claim 1, wherein the light source is a semiconductor laser. 3) An optical head device for an information recording medium according to claim 1, wherein the polarization plane changing means is a Faraday cell. 4) An optical device for an information recording medium according to claim 1, wherein the first beam splitting means is a non-polarizing beam splitter and the second beam splitting means is a polarizing beam splitter. head device. 5) An optical head device for an information recording medium according to claim 1, wherein the second light beam focusing means has an optical path adjusting means for a reflected light beam. 6) An optical head device for an information recording medium according to claim 1 or 5, characterized in that the first light beam focusing means and the second light beam focusing means are integrally formed. .