JPS6254845A - Optical pickup device - Google Patents

Abstract

PURPOSE:To produce a small-sized optical pickup device with excellent function by providing an array-type semiconductor laser having plural light-emitting points and a circuit which sequentially drives the light-emitting points with a prescribed period and smaple-holds the output from an error detector with the same period. CONSTITUTION:The laser beam is the array-type semiconductor laser 1. And also the titled device comprises a drive circuit 12, a timing circuit 13, and a sample holding circuit 14. The signal by the spot of the point A and that by the spot of the point B are sampled in synchronization with the period of the driving periods of the respective points A and B. AS to the track error, because the detection is executed with a far filled wherein the beam diameter is several milimeters or more, it hardly causes problems. As to the focus error, now that it is detected a beam-converging position, converging-light spots 15 are made to be lined up along the parting line (a) of the focus error detector 11, and therefore the error signals from respective spots become completely identical to each other. The period of the driving of laser is to be set sufficiently higher that of a recording signal, for instance, it is enough by >=10MHz for a signal of 2MHz.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an original pickup device, and in particular to an optical pickup suitable for an optical information recording device that records and reproduces information by irradiating light onto an optical recording medium such as an optical disk. Regarding equipment.

[Conventional technology]

Optical recording is a high-density recording method, and recording and reproduction are performed by condensing light emitted from a laser light source to near the diffraction limit. FIG. 4 shows a first conventional example of an optical pickup device. #It's free.

The light emitted from the semiconductor laser 16 is passed through a collimating lens 2.
The light is focused onto a recording medium 6 via a polarizing beam splitter 3, a quarter wavelength plate 4, and a condensing lens 5. Recording medium 6
The reflected light from the polarizing beam splitter 3. The light on the recording medium 6 is separated through a converging lens 7 and a beam splitter 8, and then passed through a track error detector 9 using a far-field method and a knife detector 10, and a track error detector 11 using a friend knife method. A spot position error signal is detected. Further, the information signal is simultaneously detected by the track error detector 9.

In the above-mentioned conventional optical pickup device, only one light spot is formed on the recording medium.

A method has been proposed in which an array type semiconductor laser having multiple light emitting points is used as a light source to form multiple light spots on a recording medium to improve the functionality of an optical pickup device.
By forming multiple optical spots, you can, for example, record and play back adjacent tracks simultaneously to increase the data transfer rate.
It is possible to perform error checking by playing back immediately after recording. FIG. 5 is a block diagram showing a second conventional example of an optical pickup device, in which an array type semiconductor laser 1 having two light emitting points is used. This shows an example of the configuration of an optical pickup device according to the invention.The reflected light from the recording medium 6 is imaged by the converging lens 7, and the light from each light emitting point is separated by the knife mirror 17. [Problems to be Solved] Conventional optical pickup devices using the array-type semiconductor laser described above can exhibit functions never seen before, but they require a complicated optical system to separate the reflected beam from the recording medium. The object of the present invention is to make it possible to incorporate an array type semiconductor laser having multiple light emitting points using the same optical system as the conventional type with 1 beam. The object of the present invention is to provide an optical pickup device.

[Means for solving problems]

The optical pickup device of the present invention is an optical pickup device that focuses emitted light from a laser light source on a recording medium as a minute spot, and guides reflected light from the minute spot to a photodetector for information detection and spot position error detection. a laser drive circuit comprising an array type semiconductor laser having a plurality of light emitting points each of which can be driven independently by the laser light source, and causing each of the plurality of light emitting points to emit light one by one at a predetermined period; ,
and a sample and hold circuit that samples and holds the output of the photodetector in synchronization with the light emission period of the laser drive circuit.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a timing chart showing the operation of this embodiment, and FIG. 3 is an explanatory diagram showing the position of a light spot in the focus error detector of this embodiment. The optical system configuration of this embodiment is substantially the same as that of the conventional example shown in FIG. 4, except that only the laser light source is an array type semiconductor laser 1. Furthermore, this embodiment has a laser drive circuit 12, a timing circuit 13, and a sample hold circuit 14.

In the array type semiconductor laser 1 having a plurality of light emitting points, each light emitting point is sequentially driven one by one by a laser drive circuit 12 at a predetermined period defined by a timing circuit 13 . The light emitted from the array type semiconductor laser 1 is condensed onto the recording medium 6 via the collimating lens 2, the polarizing beam splitter 3, the 1/4 wavelength plate 4, and the condensing lens 5, and the reflected light is transmitted to the polarizing beam splitter 3. , enters a track error detector 9 and a focus error detector 11 via a converging lens 7 and a beam splitter 8. The outputs of the track error detector 9 and the focus error detector 11 are sampled by a sample hold circuit 14 defined by a timing circuit 13 in accordance with the drive cycle of the array type semiconductor laser 1, and are synchronized with the drive cycle of each light emitting point. 0 obtained as a specific output Figure 2 shows a timing chart when there are 82 light emitting points A in this embodiment. Luminous points A and B
A signal from the light emitting point A and a signal from the light emitting point B are sampled in accordance with the driving cycle of the light emitting point A and the light emitting point B. Note that even when there are three or more light emitting points, information from the spots formed by the respective light emitting points can be reproduced by sequentially driving and sampling in the same manner.

Since the distance between the light emitting points of the array semiconductor laser is several tens of μm or more, the optical axis of each beam is slightly shifted in the signal detection system, and the beam position on the error detector also differs depending on the light emitting point.

However, this problem can also be easily solved as follows.

First of all, tracking errors are hardly a problem because they are detected in the far field, where the beam diameter is several φ or more, and the slight offset that occurs can be sufficiently corrected with an electric circuit. The position differs depending on the light emitting point, but with the Naifetsu method, the convergent light spot 15 is arranged along the dividing line a of the focus error detector 11, as shown in FIG. For example, the error signals from each spot will be exactly the same.

The period of laser driving should be set sufficiently higher than the period of the recording signal, for example, 10MHz for a 2MHz signal.
The above number is sufficient, and if the laser is driven at a frequency that is an integral multiple of 7' (integer multiple) in synchronization with the signal cycle, even more stable operation of the optical pickup becomes possible.

〔Effect of the invention〕

As explained above, the present invention includes an array type semiconductor laser having a plurality of light emitting points, and a circuit that sequentially drives the plurality of light emitting points at a predetermined period and samples and holds the output of an error detector at the same period. This has the effect of realizing a compact and highly functional original pickup device that has the same configuration as a conventional optical system.

[Brief explanation of drawings]

The first white line is a configuration diagram of an embodiment of the present invention, FIG. 2 is a timing chart diagram showing the operation of this embodiment, and FIG. 3 is an explanatory diagram showing the position of a light spot in the focus error detector of this embodiment. FIGS. 4 and 5 are configuration diagrams showing first and second conventional examples of optical pickup devices. 1... Array type semiconductor laser, 2...
Collimating lens, 3...Polarizing beam splitter, 4...1/4 wavelength plate% 5...Condensing lens, 6...Recording medium, 7. ...Convergent lens, 8...Beam splitter. 9...Track error detector, 10...
- Naifetsuji, 11...Focus error detector, 12...Laser drive circuit, 13...
...Timing circuit, 14...Sample hold circuit, 15...Convergent light spot, 16...
...Semiconductor laser, 17...Knife No. 1
Diagram 2 Diagram signal ε-Kuzopuri) 2 “1-1 Questions and Answers 5 Diagram

Claims (1)

[Claims] An optical pickup device having an optical system that focuses emitted light from a laser light source on a recording medium as a minute spot and guides reflected light from the minute spot to a photodetector for information detection and spot position error detection, The laser light source comprises an array type semiconductor laser having a plurality of light emitting points that can each be driven independently, and a laser drive circuit that sequentially causes the plurality of light emitting points to emit light one by one at a predetermined period; and a light emission period of the laser drive circuit. an optical pickup device comprising: a sample and hold circuit that samples and holds the output of the photodetector in synchronization with the photodetector.