JPS58146038A - Recording and reproducing optical head - Google Patents

Abstract

PURPOSE:To execute reproducing simultaneously with recording, by using 2 semiconductor lasers for recording and reproducing which are placed so that the planes of polarization become orthogonal. CONSTITUTION:Laser light of a semiconductor laser 31 for recording passes through a coupling lens 32, a polarized beam splitter 33 and an objective lens 34, and is irradiated to a recording medium 35. Laser light of a semiconductor laser 39 for reproducing has some angle with the optical axis of the objective lens 34 so as to be condensed to a position which is a little away from a condensed point of the semiconductor laser 31. Therefore, reflected light from the recording medium is obstructed by a shielding plate 36 and is not returned to the semiconductor laser 39. By a photodetector fitted to the shielding plate 36, a signal is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information recording device that performs recording and reproduction on a medium using a light beam, and uses a semiconductor laser to reproduce and monitor recorded information at the same time as recording on the medium. The present invention relates to a positioning and reproducing moonlight head used in an optical information recording device.

In recent years, there has been active development of optical information recording devices that utilize the coherency of laser light to converge it to a diameter of about 1 micron, causing minute changes on a recording medium, thereby realizing a high-density arrangement. However, one piece of information is written on the recording medium)
Because of the extremely high density of approximately 1 micron square, which corresponds to K, there are many problems with recording and reproducing information.

In other words, there are problems with the automatic focus control system to converge and maintain the light beam to a diameter of approximately 1 micron, problems with the track following control system to maintain the light beam on a predetermined track on the medium, and other problems with the bits on the recording medium. Although there are problems caused by the small area, what is currently required to be solved is how to reduce the number of defects in the recording medium or how to detect and deal with defects early.

Efforts are being made to minimize defects in the urn media during the media manufacturing process, but it is nearly impossible to eliminate defects of 1 micron am. In the end, the demand for defect-free recording media
As a result, it is considered realistic to assume a certain amount of defects and to take measures to detect and deal with them early.

A method that can be immediately thought of as a solution to defects in recording media, and which is actually used in magnetic disk drives and the like, is to detect defective portions in advance and not use the defective portions. However, this method requires that all data areas on the recording medium be inspected in advance, and cannot be applied to recording media that are subject to a crushing device, which is currently planned to be adopted in optical information recording devices. Furthermore, [19. Other methods adopted by Genya have redundant errors when recording on recording media]
There is a method of recording data using a correction code, detecting and correcting data errors during playback. However, it is not considered to be a good idea to rely entirely on error correction codes, as this will result in a decrease in information recording density and, in turn, a decrease in information recording density. As a solution to this problem, the method adopted in the present invention is to reproduce the data recorded on the medium at the same time as recording.
(This is a method of constantly monitoring the accuracy of records), and if more mistakes are found during placement than specified, re-recording in a different location, etc.
This is a method of maintaining recorded data on a medium above a certain level of quality. If K is set like this, there will be dependence on the error correction code1
Code 1-, which can reduce the degree of redundancy and has less redundancy, can be used.

The present invention was invented in view of the above situation, and its purpose is to provide a recording/reproducing moonlight head that can monitor and reproduce information recorded on a recording medium almost simultaneously. Aya, this makes it possible to simultaneously irradiate a recording medium with a recording light beam and a reproduction light beam using a semiconductor laser and a small number of optical components. See the drawings below. An overview of the configuration of conventional optical heads,
Embodiments of the optical head of the present invention, as well as its principles, functions, and effects will be explained.

FIG. 1 is a diagram showing an embodiment of a conventionally well-known placement and reproduction moonlight head. The optical head 10 includes a semiconductor laser 11
1 coupling lens 12, polarizing beam splitter 13, and wavelength plate 14. Consisting of an objective lens 15, a semi-transparent mirror 17, a track position error detector 18, a convex lens 19, a cylindrical lens 20, a focus error and signal detector 21, etc., output light from the semiconductor laser 11, a coupling lens 12, and a polarized beam.・
The light reflected from the surface of the recording medium 16 reaches the recording medium IS2 via the wavelength plate 14 and the objective lens 15 to the splitter 13, and the reflected light from the surface of the recording medium 16 passes through the objective lens 15. % wavelength plate 14, polarizing beam splitter 13t- and reflected light 23 to semi-transparent mirror 17)-5
Part is track position error detector 1gIC, other part is convex lens 1
9. Focus error and signal detector 21 via cylindrical lens 20
It is configured to reach 1C. Wave plate 14#i converts the optical output 22 of the linearly polarized semiconductor laser 11 into circularly polarized light, and converts the reflected light from the recording medium 16 surface from the circularly polarized wave.
The optical output 22 is converted into a linearly polarized wave with orthogonal polarization planes and is input to the polarization beam splitter 13), and the polarization beam splitter 13d changes the direction of the transmitted light by the polarization plane. In this case, it is separated as reflected light 23.

The track position error detector 18 detects the track position error by detecting the diffracted light at @ provided on the return medium 14, as will be explained later in the embodiments of the present invention. Lens 20. The focus error and signal detector 21 detects focus errors and signals using a known astigmatism method. The conventional placement and playback moonlight head configured in this manner increases the output of the semiconductor laser 11 in accordance with the signal during recording, and causes changes such as creating minute holes on the recording medium 16 or changing the reflectance. During reproduction, the semiconductor laser 11 generates an extremely weak pre-power output of a constant level, and reproduces by detecting changes in the reflected light from the recording medium 16. The track position error and focus error of the output light of the laser 11 on the recording medium 16 are detected by the track position error detector 18 and the focus error and signal detector 21. 15 or the position of the entire destination head.

FIG. 2 is a diagram showing an embodiment of the present invention. In the figure, the first semiconductor laser 3 for the reproduction moonlight head stirrup is shown.
1% first coupling lens 32, polarizing beam splitter 3
3, objective lens 34, rattan 2 semiconductor laser 39 for reproduction
, second coupling lens 38, shielding plate 36, detector 37
etc., the 11th and 2nd semiconductor lasers 31.39
lj are arranged so that their polarization planes are orthogonal to each other, and are optically coupled to the polarizing beam splitter 33 via the first and second coupling lenses 32 and 38, and each optical output 40
．． 41 q is added, the objective lens 3tK is added, and the light is condensed onto the recording medium 35.The optical output 41 of the second semiconductor laser 39 is the recording medium 35.
The light convergence point on the upper side is located at a position slightly away from the convergence point of the first semiconductor laser 31, for example, by about 10 microns, with respect to the moving direction of the relatively moving recording medium 35.
The first output 41 is assumed to have a slight angle with the optical axis of the objective lens 340, and since the optical output 41 of the second semiconductor laser 39 is reflected back from the recording medium 35, the reflected light -
2 is arranged between the second coupling lens 38 and the polarizing beam splitter 33 so that the light is not incident on the second semiconductor laser 39. In the figure, the optical output is 41 is inclined with respect to the optical axis of the objective lens 34, so if the angle of inclination is used and the position of the inner plate 36 is set in consideration of the aperture of the objective lens 34, the reflection of the optical output 41 from the recording medium 35 will be reduced. In the embodiment of the present invention, the reflected light 42 from the recording medium 35 of the optical output 41 of the second semiconductor 390 for reproduction is transmitted to the second semiconductor laser 39 so that the light 42 does not enter the second semiconductor laser 39. The reflected light from the recording medium 35 of the optical output 40 of the first semiconductor laser 31 for recording returns to the first semiconductor laser 31tC, although it does not enter the C-za 39. Generally, it is known that when the reflected light returns to the original semiconductor laser, it casts a shadow IIF on the semiconductor laser, causing fluctuations in optical output and causing undesirable results such as lowering the signal-to-noise ratio during playback. 1st! ! Even in the example of the conventional optical head shown in IIK, a wavelength plate is used in the polarizing beam splitter to separate the reflected light so that it does not return to the original semiconductor laser. However, when performing recording, it is sufficient that the output intensity of the high-energy light applied in pulses to l, aK, and pulses on the recording medium 35 is maintained at a certain level or higher. laser 3
Even if the 11C return light output is changed, it is not a very big problem. On the other hand, the optical output 42 of the second semiconductor laser 39 for reproduction, which needs to avoid fluctuations in output, is configured so that it does not return to the original second semiconductor laser 311 as described above, so the signal remains unchanged even during reproduction. without compromising the noise-to-noise ratio.

There is no problem even if the wavelength plate and the polarizing beam splitter are not used together to separate the reflected light.
- Next, the method of detecting the track position error, focus error, and signal will be explained with reference to FIGS. 3, 4, and 5. Second
In the figure, a detector 37 is disposed on a disc plate 361C, and receives reflected light 42 to detect a track position error, a focus error, and a signal. Detector 37 as shown in enlarged Fig. 4
It is assumed that the detector 37 is composed of a divided photosensitive element such as a photodiode, and FIG. 5 is a turtle-shaped diagram showing a plan view of the detector 37 seen from the polarizing beam splitter 33 side in FIG.

FIG. 3 is a diagram for detecting the focus error of the objective lens 34. In the figure, the optical output 41 of the second semiconductor laser 39 is focused onto the recording medium 35 by the objective lens 34, and the reflected light 42 is objective. Therefore, the second semiconductor laser 311Ka in FIG. 2 does not return. reflected light 42
The case where the focus of the objective lens is correctly placed on the upper surface of the recording medium 35 is shown, but the recording medium 35 is focused on the objective lens 35.
If it moves further away and downward, it is indicated by a dotted line. The reflected light 52 of the recording medium 51i is combined with the reflected light 42 and the objective lens 34.
After passing through, it is parallel and the aim is outside the optical axis of the objective lens 34.
is moving to. When the recording medium 35 moves in the opposite direction, the reflected light 42 also moves in parallel in the opposite direction. Considering FIG. 2, the reflected light 42 moves up and down on the detector 37 due to the distance change between the recording medium 35 and the objective lens 34. Therefore, if the detector 37 is placed at an appropriate position and the area over which the reflected light 42 irradiates the detector 37 changes as the reflected light 42 moves up and down, the focal point of the objective lens 34 and the recording medium The focus error signal can be detected in proportion to the distance between the 35 pages. In this embodiment, the detector 37 is divided into four parts as shown in FIG. By taking the difference from the sum of .74, a more accurate focus error signal can be obtained.

FIG. 4 (FIG. 4) is a diagram for explaining the operation related to detection of a track position error), and shows a cross section that is perpendicular to the plane of the paper in the moving direction of the medium and the track direction line, and therefore perpendicular to FIG. 2. As a method of obtaining track position error in an optical information recording device, an #IC tile is placed on a substrate in advance and a thin recording medium is adhered thereon. According to Japanese Unexamined Patent Application Publication No. 1!155-55448, etc. It is proposed that FIG. 4 also detects the track position error in accordance with the proposal, and the output 41 of the second semiconductor 390 shown in FIG.
The light is focused on the IsL body 3 along with the normal reflected light 42.
Diffracted light 6 due to both side surfaces of the groove 61 provided in the groove 5
2.63 simultaneously passes through the objective lens 34f and enters the detector 37 shown in FIG. Diffracted light 62.6
Since the objective lens 340 of No. 3 is limited by the aperture of the objective lens 34 that appears in the direction away from the optical axis, if the focal point of the light output 41 shifts to the left or right (#1161), it will be detected by the objective lens 31C. @37#C Causes a difference in the amount of diffracted light 62.63 that is collected, therefore diffracted light 6
If 2.63 and the reflected light 42 are detected differentially with respect to the moving direction of the recording medium 35, it is possible to obtain an optical output proportional to the track position error. The 37 detectors shown in Figure 5 are divided into left and right parts for this purpose.
By taking the difference between the sum of the detection elements 71 and 74 and the sum of the detection elements 72 and 73, it is possible to obtain an output corresponding to the track position error of 1cf.

In this way, it is possible to obtain a large signal by the detector 37 shown in Figures 2g and 11S) relative to the focus error and rack position error, but the signal recorded on the recording medium 35 is as shown in Figure 5. Nine detection elements shown in 71°72.73. You can get the sum of -74 by working.

Even when compared with the conventional configuration example described above and shown in the 9-position reproduction head company 1mK, the number of elements does not increase at all,
It has independent light beams for placement and reproduction, and can monitor recorded data immediately after the device is installed. Furthermore, the arrangement and reproduction moonlight head according to the present invention has features such as the fact that the type of oscillation wavelength of the semiconductor laser used in the multiplexed book is independent of the type of oscillation wavelength of the semiconductor laser used due to the difference in the polarization plane of the two semiconductor lasers, and the object of the present invention is more than achieved. To 3! ! It is something that can be achieved.

The principle and operation of the present invention have been explained above with respect to the embodiments of the present invention.
or deflection of the light beam after detection of track position error;
The mechanism for moving the optical head, etc. is omitted as it is based on a known method. In addition, although only an example is shown in this embodiment regarding detection of focus error and track position error, it is fully possible to apply other known methods.

The key point of the present invention is that the optical outputs of two semiconductor lasers whose output light planes of polarization are orthogonal are combined by a side beam splitter and added to the objective lens. In order to make effective use of the aperture of the objective lens, the reproducing optical system, which emphasizes the signal-to-noise ratio, allows the reflected light to return to the semiconductor laser. This is a turtle designed to prevent reflected light from returning to the semiconductor laser. Various modifications and additions may be made without departing from the spirit of the present invention, such as adding a new element for shaping the light beam, adding a reflecting mirror to change the optical path, etc. Of course, the above description of the embodiments is not intended to limit the scope of the invention in any way.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of a conventional arrangement reproducing moonlight head, Fig. 2 is a block diagram showing an embodiment of a recording reproducing moonlight head according to the present invention, and Fig. 3 shows a focus error used in the embodiment. Figure 4 is a diagram for explaining the principle of detection, Figure 4 is a diagram for explaining the principle of track position error detection used in the example, and Figure 5 is a plan view of the detector used in the example. , 10 is an optical head, 11 is a semiconductor laser,
12#i coupling lens, 13 is a polarizing beam splitter, 14 is a % wave plate, 15 is an objective lens, 16 is a recording medium, 17d is a semi-transparent mirror, 18 is a track position error detector, 19 is a convex lens, 20 is a cylindrical lens , 21
31 is a focus error and signal detector, 31 is a first semiconductor laser for placement, 32 is a first coupling lens, 33 is a polarizing beam splitter, 34 is an objective lens, 35 is a placement medium, 36 is a shielding plate, 37d Detector, 3
Reference numeral 8 indicates a second coupling lens, and reference numeral 39 indicates a second semiconductor laser. Fig. 1 Fig. 2 ■ Fig. 3 f Fig. 4 Chest 5 Fig.

Claims (1)

[Claims] 1. A first semiconductor laser that emits a recording light beam and a second semiconductor laser that emits a reproduction light beam, which are arranged so that the polarization planes of their output lights are orthogonal to each other. The light outputs are applied to the polarizing beam splitter through corresponding first and second coupling lenses, optically summed, and respectively focused on different points on the recording medium by the 1s30 objective lens. 1. Adding the output light of the first semiconductor laser that emits the laser beam to the polarizing beam splitter via the first coupling lens, and adding the output light of the first semiconductor laser to the polarizing beam splitter. A second beam emits a regenerating beam whose polarization plane is orthogonal to the
The output light of the semiconductor laser is passed through a second coupling lens, and a part of the output light is sent to the polarization beam splitter 11a by a coupling means, or the output light is output from the second semiconductor laser. The output light is a light beam having a diameter sufficiently smaller than the aperture of the second objective lens;
The output light of the second semiconductor laser is added to the polarizing beam splitter through a third objective lens and is optically added to the polarizing beam splitter, and the output light of the second semiconductor laser is transmitted to different points on the placement medium through a third objective lens. The configuration is such that the reflected light from the recording medium is converged at a point where it does not return to the light emitting point of the second semiconductor laser, and the reflected light is used to detect information on the recording medium, focus error, and track position. An optical head for recording and reproducing, characterized in that it includes means for detecting errors. λ The light output of the second semiconductor laser is configured to be focused slightly backward on the relatively moving arrangement medium KTh (from the point where the light output of the first semiconductor laser is focused), and the 1s10 semiconductor laser is The information recorded by the laser is
3. A position-reproducing moonlight head according to claim 1 or 2, wherein the reflected light of the output light of the semiconductor laser is monitored almost simultaneously.