JPS60113336A - Optical head - Google Patents

Abstract

PURPOSE:To enable the titled head to detect information of at least one separated laser beams by constituting the head to project at least one laser beam out of laser beams not extracted by a light extracting member at focussed time, and to project other laser beams to a light insensitive part. CONSTITUTION:A light sensitive area (light sensitive part) 54 is provided in a part that shields preceding laser beam 18 of a light extracting member 53, and a light insensitive area (light insensitive part) 55 is provided in a part that shields laser beam for recording. When focussed, a preceding beam spot 24' is formed in the light sensitive area 54, and photoelectric signals obtained from the light sensitive area 54 are used for detecting amount of reflected light of preceding laser beam. Here, it is desirable that the area of the light sensitive area 54 is sufficiently large to facilitate assembling and adjustment of the optical system. On the other hand, the light insensitive area 55 is insensitive electrically to the laser beam 14 for recording.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is applicable to image files, still image files, COM
It is used to create holes in the recording layer of multi-information storage media using focused light, or to locally change the state by changing optical properties such as refractive index and reflectance. The present invention relates to an optical head capable of recording information by causing a change and reproducing information therefrom.

[Technical background of the invention and its problems]

Conventionally, optical heads of the above type are known that are capable of recording information at high speed and have a function of simultaneously reading the recording and confirming the recorded contents.

In this optical head, as shown in Fig. 1, a hole is made in the recording layer 2 of the information storage medium, and the optical characteristics such as refractive index and reflectance are changed locally. Flashable recording radar to record information.
The beam 3 is focused on the recording layer 2 of the information storage medium 1 to form a recording focused beam spot 4. The recording beam spot 4 has a groove-shaped tracking that moves along the id 5. Then, when the recording laser beam 3 is turned on, a local state change occurs on the recording layer 4 of the information storage medium J, and newly recorded information signal pits 6 are formed. Immediately after recording, a reading laser beam 7 for confirming the recorded content is condensed to form a reading condensed beam spot 8. Recording radar
Since the beam 3 and the reading laser beam 7 are condensed,
Although they pass through the same objective lens 9, the optical axis W of the recording laser beam 3 and the optical axis r of the reading laser beam 7 are slightly tilted in the collimated state before passing through the objective lens 9. On the recording layer 2 of the storage medium 1, a recording focused beam spot 4 and an additional reading focused beam spot 8 are located at separate positions.

However, with this optical head, when recording continuously, it is often necessary to reconfirm the recording contents and check in advance (before recording) whether or not there will be any problems with recording there, since the area to be recorded is the actual target area. No confirmation has been made. That is, the reading focused beam spot 8 whose recording state is to be inspected is always located beyond the recording focused beam spot 4 with respect to the traveling direction. Therefore, even if an abnormality is detected during continuous recording of information, it means that the edge has already been recorded incorrectly), especially when the following situations occur: become.

(1) If a track goes off the track during continuous recording and moves to an already recorded part, part of the already recorded part will be destroyed before the abnormality is detected. Furthermore, if a track is lost during continuous recording and the track moves to an unrecorded area, a wide area before and after the erroneously recorded area will be destroyed.

(1) If you start recording at a place where it should not have been recorded due to some mistake, by the time the error in the recording start position is detected, recording has already started and the state of the part you are trying to record is changing. When a problem is detected (for example, there is a scratch or an incorrectly recorded part), recording is stopped once, the range of the problem is confirmed using the reading beam spot 8, and the area is removed only after it is memorized. It takes time to deal with problems such as having to start recording from a certain point.

Therefore, recently, in order to solve the above-mentioned problem, as shown in FIG.
eam 5pot) An optical head that forms a JO has been proposed. In this optical head, at least three beam spots are arranged substantially on the same line along the tracking guide 5 on the recording layer 2 of the information storage medium 1, that is, at least three beam spots are arranged in order from the front in the traveling direction. Beamsbotno that can be done. , by arranging at least the beam spot 4 used for recording information and the beam spot 8 capable of reading information, and using the foremost preceding beam spot 1o, i) no information has already been recorded in that part; Check the and.

11) Make sure that the area is not a place where the error rate is high due to dirt, scratches, etc.

iii) The position on the multi-information storage medium 1 is determined by reading the information of the uneven bit 6 partially formed along the tracking guide 5, which already exists when the information storage medium 1 is created (formed when the master is created). (track number, sector position) to know early.

1) Before recording, investigate from where on the surface of the recording layer 2 of the information storage medium 1 is an inappropriate recording area due to scratches, old erroneous recordings, etc.

etc.

However, in these optical heads, there is a problem that a part of the recording laser beam enters the detection part of the reading laser beam, so conventionally, the wavelengths of the reading laser beam and the recording laser beam are Alternatively, a method of separation using a dichroic mirror has been adopted, but the following phenomena may cause the recording laser beam to be mixed in.

■ Because the recording laser beam oscillates in multiple modes, light with a certain wavelength passes through the dichroic mirror.

■ There are variations in recording laser elements, and the oscillation wavelength differs depending on the element.

■ Even a dichroic mirror cannot block 100% of the recording laser beam.

■ Stray light from the recording laser light occurs.

Therefore, a light extraction member is provided at or near the convergence point of the multiple laser beams on the ridge that are reflected by the information storage medium and passed through the objective lens at the time of focusing, and this extracts one laser beam and sends it to the photodetector. An optical head that emits light has been proposed.

However, this optical head can only detect information from one laser beam, and in order to detect information from other laser beams, it is necessary to divide the multiple laser beams using a half prism in advance.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and its purpose is to be able to separate multiple laser beams and to detect information on at least two or more separated laser beams. The purpose of the present invention is to provide an optical head with improved performance.

[Summary of the invention]

In order to achieve the above object, the present invention uses focused light to record or reproduce at least information on an information storage medium, and at the same time, at the time of focusing, at least two focused beams are directed onto the recording layer of the information storage medium. In an optical head that can emit light, there is an objective lens that focuses multiple laser beams that are irradiated toward an information storage medium, and an objective lens that collects multiple laser beams that are reflected by the information storage medium and passes through the objective lens again. a projection lens for projecting the multiplexed laser beams focused by the projection lens, a light extraction member disposed at or near the convergence surface of the multiplexed laser beams focused by the projection lens, and a light extraction member disposed at or near the convergence surface of the multiplexed laser beams focused by the projection lens; comprising a photodetector for receiving light, a light sensitive part and a light non-sensing part provided on the light extracting member, and at least one of the laser beams that is not extracted by the light extracting member when in focus; The invention is characterized in that the laser beam is projected onto the light-sensitive part, and the other laser light is projected onto the light-insensitive part.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In Figures 3 and 4, the recording laser light source is used.
It disappears when information is being read. When recording new information, a signal containing the information to be recorded is transmitted from the recording information signal generator 12 to the recording laser drive circuit 3, and the recording laser light source 1 is activated accordingly. A recording laser beam 14 is formed by blinking. The light emitted from the back side of the recording laser light source 1 is received by the recording laser light amount monitor part 5,
The output of the recording laser light amount monitor part I5 is negatively fed back to the recording laser drive circuit 13 so that the recording laser light amount when turned on is always constant. Further, reference numeral 16 is a multiple laser light source for reading, and the amount of light emitted from it is always kept constant regardless of whether information is being recorded or read υ. A reading laser beam Noah and a leading laser beam 18 are formed from this multiple laser light source 16 for reading υ. In the case of a multiple laser light source for reading, a part of the light emitted from this is detected by the reading laser light amount monitor part JJ7, and is negatively fed back to the reading laser drive circuit 118 to reduce the output light amount. will be stabilized. And the reading laser beam 1
2. The preceding laser beam and the recording V-server beam J4 are integrated in the multiple laser beam processing section 19, and the condensing section (
The recording layer 22 of the information storage medium 2 through the objective lens) 20
The light is focused in a line along the tracking guide 23 above. Then, the tracking guide 23...in order from above, the leading beam spot 24, the recording beam spot 2
5 and reading) beam spot 26 is formed.

In addition, the light reflected on the information storage medium 21 is returned to the condensing section (
After passing through the objective lens) 20, the multiple laser beam processing unit 1
9 to a preceding laser beam reflected light amount detection section 27, an information signal reading section 28, a track deviation detection section 29, and an out-of-focus detection section 3θ. However, the information signal reading section 28 and the track deviation detection section 29 are often shared by the same photodetector. In addition, the track deviation detection section 2
9 and the output of the out-of-focus detection unit 30 are track deviations, which are corrected by moving the condensing unit (objective lens) 20 in two axes via the out-of-focus correction circuit 3, and out-of-focus correction drive circuit. 32. here,
Track deviation detection and out-of-focus detection are performed using only one beam spot, that is, the reading beam spot 26.

Note that 33 in FIG. 4 is an information signal bit.

Further, as shown in FIG. 5, the reading multiple laser light source noro includes one reading laser light source 34,
The multiplex laser beam generator 35 separates the laser beam into a large number of laser beams, that is, a reading laser beam 17 and a preceding laser beam 18. Further, the multiplex radar light processing section 19 includes a laser light combining section 36 and an isolation section 3.
7. It is divided into laser beam separation section 38. The multiple reading laser beam (the reading laser beam 17 and the preceding laser beam 18) generated by the multiplex laser beam generating section 35 and the recording laser beam J4 are combined by the laser beam combining section 36, and a similar laser beam is generated. A light path passes through.

Multiple laser beam A that has passed through the laser beam combining section 36
li 4fA optical beam splitter and λ/4 plate A-
The light passes through the isolation section 37 and reaches the information storage medium 2 via the condensing section (objective lens) 20. The multiple laser beam reflected on the information storage medium 2 and passed through the condensing unit (objective lens) 20 again is sent to the isowarf 1 f unit 37.
The laser beam is directed in the direction of the laser beam separation section 38 by the action of The multiplexed laser beams are separated by a laser beam separation section 381fC and sent to the preceding laser beam reflected light amount detection section 27, out-of-focus detection section 30, track deviation detection section 29, and information signal reading section 28, respectively.

Further, as shown in FIG. 6, a constant voltage source 39, a dart circuit 40° current control circuit 41 are connected in series to the recording laser light source 11.

When information is being read, the dart circuit 40 is closed and no current flows. When recording information, the dart circuit 4° is opened only when forming a bit in accordance with the output of the recording information signal generator 2. A current is then supplied from the constant voltage source 39 to the recording laser light source 11 via the dart circuit 40 and the current control circuit 4. By controlling this supplied current value with the current control circuit 4, the amount of intermittent light emitted from the recording laser light source 1 is controlled. Immediately after starting recording of information, the switching unit 42 operates and the output voltage from the recording laser light intensity setting reference voltage generating unit 43 is directly supplied to the current control circuit 4, and current control is performed based on the voltage value. It will be done. A laser beam intermittently generated from the back side of the recording laser light source I is received by a recording laser beam monitor part 5. Further, in synchronization with the signal from the recording information signal generator 12, the output of the recording radar light amount monitor part 5 is sampled and held in the sample and hold circuit 44. This sampled and held value is compared with another reference voltage generated by the recording laser light intensity setting reference voltage generator 43 in a difference circuit (subtraction circuit) 45, and negative feedback ( feedback).

Immediately after the start of recording, the reference voltage generation section 43 for setting the recording laser light amount and the current control circuit 4 are connected, but immediately after the start of recording, the difference circuit (subtraction circuit) 45 and the current control circuit 41 are connected by the switching section 42. are switched so that they are connected directly.

In place of the sample and hold circuit 44, as shown in FIG. 7, a peak detection circuit 46 is used to sample and hold the output of the recording laser light amount monitor part 5, and the recording laser light 'ji!''The reference voltage of the setting reference voltage generation section 43 may be compared. Further, in FIGS. 6 and 7, electrical signals are shown by solid arrows, and optical paths are shown by broken arrows, contrary to FIG. 2.

Next, the laser beam separation section 38 will be explained. The laser beam separation section 38 separates the light that is reflected by the information storage medium 2 and returns. That is, in the parallel light state, the light reflected by the information storage medium 2, separated by the isolating section 37, and proceeding to the detection system is overlapped by the reading laser beam 17, the recording laser beam 14, and the leading laser beam 18. However, since the optical axis r of the reading laser beam 17, the optical axis w of the recording laser beam 14, and the optical axis p of the preceding laser beam 18 are slightly inclined to each other, the light The reading laser beam 17, the recording laser beam 14, and the preceding laser beam 18 are geometrically separated at or near the focal point of the projection lens 52 placed on the road. A light extracting member 53 such as a knife is disposed in this separated portion (at or near the condensing point), and only the reading radar beam 17 is extracted by this light extracting member 53. It is projected onto a photodetector 51.

Therefore, the recording laser beam 14 and the preceding laser beam J8 are blocked by the light extracting member 53, but the preceding laser beam 1 of the light extracting member 53
A photosensitive area (photosensitive detail) 54 is located in the portion that blocks light from the photosensitive area 8.
Light-year sensing regions (light-year sensing portions) 55 are provided in portions that block the recording laser beam 14, respectively. At the time of focusing, a leading beam spot 24' is formed in the photo-sensing area 54, and a photoelectric signal obtained from this photo-sensing area 54 is used to detect the amount of reflected light of the leading laser beam. Here, it is desirable that the area of the photo-sensing region 54 is sufficiently large so that the assembly and adjustment of the optical system can be easily performed. On the other hand, the light-year sensing area 55 is electrically insensitive to the recording laser beam 14. Note that 25' is a recording beam spot formed in the light-year sensing area 55.

Next, the photodetector 51 is activated by the reading laser beam 17.
It receives light to read information signals, detect track deviation, and detect out-of-focus. That is, as shown in FIG. 9, the light extraction member 53 has its extraction end face 5.
3a is arranged so as to be substantially on the optical axis r of the reading laser beam 17. The photodetector 5 divided into four diagonally perpendicularly behind it is arranged, and the center of the photodetector 5 (51a is located at the center of the photodetector divided into four)
, 51b, 5)C.

51d) is the optical axis r of the reading-intensive laser beam 17.
At the same time, one of the dividing lines is parallel to the direction in which the multiple focused beam spots are lined up on the focusing surface.
The other one is now at a right angle. Therefore, the photodetector cells 51h, 5Jb, 5noa, 51 of the photodetector 54
Among the detection signals obtained from d, ((A+B)-(C+D)) is electrically calculated to perform out-of-focus detection. Further, the shift of the track is detected by ((A+D)-(B+C)). Furthermore, the sum of the four detection signals (A+B+C
+D) the information signal is read.

According to the above configuration, the reading laser beam J7 is extracted by the light extracting member 53 and irradiated onto the photodetector 5, and the preceding laser beam 18 is emitted to the photodetecting area 54.
Since the recording laser beam 14 is irradiated to each light-year sensing area 55, the recording laser beam 14
The information of the read-intensive laser beam 17 and the information of the preceding laser beam 18 can be detected without being affected by this. Furthermore, out-of-focus detection, track deviation detection, information signal reading υ, and preceding beam reflected light amount detection can be performed simultaneously in one small portion.

Further, since the size of the photo-sensing region 54 is sufficiently large, the preceding laser beam J8 is irradiated onto the sensing region even if it is slightly shifted. Therefore, it is easy to assemble and adjust the optical system.

Note that FIG. 10 shows an embodiment using a photodetector 56 divided into two parts, in which two light beams are arranged along a direction perpendicular to the direction in which the tracking guide 23 is projected. Track deviation is detected using the difference between the detection signals from the detection cells 56m and 56b, and the information signal is read using the sum of the detection signals. Even in this case, information on the preceding laser beam 18 can be detected in addition to information on the reading laser beam 17. In this case, the out-of-focus detection is performed by dividing multiple laser beams in advance with a prism and using one of the divided multiple laser beams for reading.

〔Effect of the invention〕

As explained above, according to the present invention, at least information is recorded or reproduced on an information storage medium using focused light, and at least two focused beam spots are irradiated onto the recording layer of the information storage medium at the time of focusing. In an optical head capable of A projection lens, a light extracting member disposed at or near the converging surface of the multiple laser beams focused by the projection lens, and a light receiving the laser beam extracted by the light extracting member. It comprises a detector, a light sensitive part and a light non-sensing part provided on the light extracting member, and at least one laser beam among the laser lights that is not extracted by the light extracting member when the focus is focused. is projected onto the light-sensitive part and the other laser light is projected onto the light-insensitive part, so that it is possible to separate multiple laser beams and to separate at least two or more separated laser beams. It has excellent effects such as being able to detect information.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a conventional example, Fig. 2 is an explanatory diagram showing another conventional example, Fig. 3 is a block diagram showing an embodiment of the present invention, and Fig. 4 is an information storage medium in the same embodiment. FIG. 5 is a perspective view showing the state of the laser beam directed upward, and FIG. 5 is a partially detailed view of the optical head shown in FIG. 2. FIG. FIG. 7 is a block diagram showing another embodiment of the drive system for the recording laser light source. FIG. 8 is a block diagram showing the laser beam separation section shown in FIG. 5. FIG. 9 is a block diagram showing the drive system of the recording laser light source. 10 is a perspective view of the same, and FIG. 10 is a perspective view showing an embodiment using another photodetector. 14... Laser beam for recording, Noah... Laser beam for reading, No. 8... Leading laser beam, 20
...Objective lens, 2...Information storage medium, 24...
・Advanced beam spot, 25...4 beams for recording, 26...2 beams for reading, 5...photodetector, 52...projection lens, 53...light extraction member , 54... Light-sensitive part (light-sensitive area), 55... Light-insensitive part (light-year sensitive area). Applicant's representative Patent attorney Takehiko Suzue Figure 6 11 Figure 7 Figure 9 55 :1":l":) IC

Claims (3)

[Claims] (1) In a device capable of at least recording or reproducing information on an information storage medium using focused light and irradiating at least two focused beam spots onto the recording layer of the information storage medium when focused, an objective lens that condenses multiple laser beams irradiated toward an information storage medium; a projection lens that condenses multiple laser beams that are reflected by the information storage medium and passes through the objective lens again; A light extracting member disposed at or near the converging surface of the multiplexed laser beams; a photodetector that receives the laser beams extracted by the extracting member; A light sensing part and a light non-sensing part are provided in a part system, and at least one laser beam among the laser beams that are not extracted by the light extraction member at the time of focusing is projected onto the light sensing part. and another laser beam is projected onto the light non-sensing portion. (2) The optical head according to claim 1, characterized in that a multi-divided photodetector is used as the photodetector. (3) The optical head 0 according to claim 1 or 2, characterized in that a photodetector divided into at least four diagonal lines is used as the photodetector.