JPH076404A - Device for reading optical disk - Google Patents

Abstract

PURPOSE:To easily detect positions of plural spots of a return light beam made incident on a light receiving part. CONSTITUTION:The level signals of the spots L1, L2, L3, L4, L5 formed by image- formation of the return light beam of a light beam irradiating an optical disk made incident on the light receiving part 11 arranged in a matrix shape are supplied to a main spot position detection circuit 21, and a position of a main spot L5 is detected to be sent to an arithmetic circuit 20. The level signals of the spots L1, L2, L3, L4, L5 are supplied to the arithmetic circuit 20 also, and the positions of the spots L1, L2, L3, L4 are discriminated by switching and inputting the level signals from the light receiving part 11 based on the position of the main spot L5, and an optical detection signal is detected by using the level signals of respective spots.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reading apparatus for injecting a light beam on an optical disk and detecting information recorded on the optical disk from a return light beam from the optical disk.

[0002]

2. Description of the Related Art In recent years, so-called writable optical discs, which are capable of writing, erasing and reading information by using a light beam, have been generalized as optical discs as information recording media.

Among the writable optical discs, there is a so-called magneto-optical disc that can repeatedly write and erase information. This magneto-optical disk has a structure in which a perpendicular magnetic film forming a recording layer is provided on the surface of a substrate, and the perpendicular magnetic film is covered with a protective layer, and is formed in a disk shape as a whole. is there.

A pre-groove (guide groove) for reading a tracking error signal used for controlling a tracking servo is previously formed along the recording track on the magneto-optical disk.

For the above-described magneto-optical disk,
When a predetermined external magnetic field is applied to a large number of concentric recording tracks surrounding the center of the magneto-optical disk,
By scanning with a light beam modulated according to the recorded information, a magnetization direction reversal region of a predetermined pattern is formed and information is written.

When reading the information recorded on the magneto-optical disk, a so-called optical pickup, which is an optical disk reading apparatus of an optical system including a laser diode, an objective lens, a photodetecting section and the like, is used. With this optical pickup, first, the recording track is scanned with a light beam having a power lower than that at the time of writing information emitted from the laser diode. The return light beam from the recording track is split while being incident on the photodetector, and then is incident on the photodetector. The photodetector detects and compares the orthogonal polarization components, that is, the P-polarization component and the S-polarization component, so as to respond to the rotation of the polarization plane corresponding to the magnetization direction reversal pattern corresponding to the written information. The read signal is formed on the basis of the output of the change.

A change in the return light beam from the pregroove is detected to form a tracking error signal. For example, the position of the return light beam on the photodetector or the shape of the spot is detected to generate a focusing error signal. It is formed.

The spot when the return light beam incident on the photodetector is imaged is as shown in FIG.
At the center of the photodetection section, there is a four-division detector 31 which is formed by arranging four light-reception areas A, B, C and D having a small light-reception area in a square shape.
1. A light receiving section 3 having a light receiving area I on the left and right sides of 1.
2 and a light receiving portion 33 having a light receiving area J are arranged, and a light receiving portion 34 having a light receiving area E and a light receiving portion 35 having a light receiving area F are arranged at upper and lower positions.

Of the above return light beams, the center return light beam
The beam is received by the four-division detector 31 and forms an image.
By this, spot L₁₅You can Also, the P polarization component
The return light beam composed of is received by the light receiving section 32 and is combined.
Spot L by image ₁₁From the S-polarized component
The resulting return light beam is received by the light receiving section 33 and forms an image.
Spot L by₁₂You can In addition, the central return
The side beam of the reflected light beam is received by the light receiving units 34 and 35.
By being illuminated and focused, the spot L₁₃, L₁₄In
Wear.

The photodetector outputs a photodetection signal corresponding to the amount of light of the spot incident on each light receiver, and a read signal (RF) corresponding to the information recorded on the magneto-optical disk.
Signal), a tracking servo signal used for controlling the tracking servo, and a focusing servo signal used for controlling the focus servo.

[0011]

By the way, when constructing the above-mentioned optical disc reading apparatus, it is very difficult to assemble the return light beam so that it is accurately incident on the light receiving portion of the light detecting portion.

In order to quickly read the information recorded on the optical disk, for example, when a plurality of recording beams on the optical disk are simultaneously scanned with a large number of light beams to read the recorded information, the conventional optical disk is used. It is difficult to detect the absolute position and the relative position of the plurality of return light beams from the recording track corresponding to the plurality of light beams by using the above reading device, and it is very difficult to realize this.

Therefore, in view of the above situation, the present invention provides an optical disk reading apparatus capable of easily detecting the positions of a plurality of spots by the return light beam from the optical disk when reading information from the optical disk. Is.

[0014]

An optical disk reader according to the present invention comprises a light source, a beam splitter for separating a light beam emitted from the light source and a return light beam of the light beam from the optical disk, and a plurality of beam splitters. Light receiving portions are arranged in a matrix, and the light receiving means receives the return light beam through the beam splitter and outputs a light detection signal. One side of the light receiving element has a length above the light receiving portion. In the case where the plurality of spots of the return light beam imaged on are not in focus, and the radius of each spot is wide, it is shorter than the distance between the outer rings of each spot. Solve.

Further, it is characterized in that it has a detecting means for specifying the areas of a plurality of spots of the return light beam based on the output from the above-mentioned light detecting means.

[0016]

In the present invention, the positions of the plurality of spots of the returning light beam are detected by making the returning light beam incident on the plurality of light receiving portions and inputting the outputs from the light receiving portions to the detecting means.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an optical disk reading apparatus according to the present invention.

As shown in FIG. 1, the optical disk reading apparatus according to this embodiment includes a laser diode 1 which is a light source of a light beam, an objective lens 5 for focusing the light beam on a magneto-optical disk 6, and a magneto-optical disk. 6. A return light beam reflected on 6 is detected and converted into an electric signal (detection signal) of a current level or a voltage level according to the amount of light, and the optical detection section 10 and other optical components are included to form one unit. Then, it is moved along the radial direction on the magneto-optical disk 6 by a known moving means such as a linear motor.

The light beam emitted from the laser diode 1 of FIG. 1 is diffracted by the grating 2 and divided into at least three beams, and further collimated by the collimator lens 3. The light beam that has become parallel light is incident on the beam splitter 4, and then converged and irradiated on the magneto-optical disk 6 via the objective lens 5.

Of the three divided light beams, the central one irradiates the center of the recording track on the magneto-optical disk 6, and the remaining two light beams irradiate the pre-groove. The plane of polarization of the light beam emitted to the center of the recording track is rotated according to the magnetization pattern on the recording track. Further, the light beam with which the pregroove is irradiated undergoes modulation corresponding to the edge of the pregroove.

The three return light beams reflected by the magneto-optical disk 6 are incident on the beam splitter 4 via the objective lens 5, are reflected on the boundary surface, and then are incident on the Wollaston prism 7.

The Wollaston prism 7 further divides the incident return light beam into, for example, three light beam components. The split return light beam is converged by the collimator lens 8, and further, the multi-lens 9 including a cylindrical lens or the like for adjusting the focal length of the return light beam and generating astigmatism is passed through the inside of the light detection unit 10. The light is incident on the light receiving unit 11. The photodetection unit 10 detects the light amount of the incident return light beam and converts it into a photodetection signal.

As shown in FIG. 2, the light receiving section 11 is formed by arranging a plurality of photodiodes and the like in, for example, n rows vertically and n columns horizontally and arranged in an n × n matrix. There is. A plurality of spots are formed on the light receiving unit 11 by forming an image of the incident return light beam. In addition, the length of one side of the light-receiving element is longer than the distance between the outer rings of the respective spots when the imaged spot is out of focus and the radius of the spot is longer than when it is in focus. Is also getting shorter. As a result, when two spots are detected by one light receiving unit, there is no possibility that the position of each spot cannot be detected.

The light receiving portion 11 on which the return light beam is incident.
A main spot L ₅ due to the central return light beam is located at the center of the center of the center of, and spots L ₁ and L _{2 of} the return light beam separated by the Wollaston prism 7 are located on the left and right sides of the main spot L _5. The spots L ₃ and L _{4 of} the return light beam separated by the grating 2 are located above and below the central return light beam.

A focus error signal can be obtained by detecting the light quantity of the central return light beam forming the main spot L _5, and by detecting the light quantity of the return light beam forming the spots L ₁ and L _2. An information read signal, that is, an RF signal can be obtained, and the spot L
_A tracking error signal can be obtained by detecting the light intensity of the return light beam forming ₃ and L ₄ .

From the vertical and horizontal sides of the light receiving section 11,
The return light beam detected by the light receiving unit 11 is output as a level signal. This level signal is simultaneously supplied to the arithmetic circuit 20 and the main spot position detection circuit 21 in the parallel processing processor.

In the main spot position detection circuit 21, the position of the main spot L ₅ , which is the image of the central return light beam, on the light receiving portion 11 is calculated by using the supplied level signal. The obtained position of the main spot L ₅ is sent to the arithmetic circuit 20.

In the arithmetic circuit 20, the mains sent are sent.
Pot L_FiveSupply from the light receiving unit 11 based on the position of
The level signal to be output and switch the return light beam spots.
To L ₁, L₂, L₃, L_FourLevel signal corresponding to the position of
By taking out each spot of the returning light beam
L₁, L₂, L₃, L_FourFind the exact position.

Further, by detecting the light quantity of the return light beam forming each of the spots L ₁ , L ₂ , L ₃ , L ₄ and L ₅ whose positions are obtained as described above, by using the level signal, As with conventional optical disk readers, RF
A signal, a tracking error signal, and a focusing error signal are formed.

The tracking error signal is a tracking servo circuit 22 for controlling movement of the optical disk reading apparatus of this embodiment in the radial direction of the magneto-optical disk 6.
Further, the focusing error signal is supplied to the focusing servo circuit 23 for controlling the movement of the optical system in the optical disc reading apparatus of this embodiment in the focusing direction.

The above embodiment is an example of the present invention.
It goes without saying that various other configurations can be adopted without departing from the scope of the present invention.

[0032]

As is apparent from the above description, the optical disk reading apparatus according to the present invention separates the light source, the light beam emitted from the light source, and the return light beam of the light beam from the optical disk. A beam splitter and a plurality of light receiving portions are arranged in a matrix, and a light detection unit that receives the return light beam that has passed through the beam splitter and outputs a light detection signal is provided, and based on the output from the light detection unit. By including the detection means for specifying the areas of the plurality of spots of the return light beam, it is possible to easily detect the positions of the plurality of spots when the return light beam is imaged by the light receiving unit. When assembling the optical disk reading device, it is not necessary to set the returning light beam to be incident on the correct position on the light receiving section. It is possible to simplify the assembly of the device.

Further, even when the plurality of light beams emitted from the light source are scanned and the recording tracks are scanned, the positions of the spots of the returning light beams from the plurality of recording tracks can be detected at the same time. It is possible to read information from the recording tracks of the.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an optical disk reading apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing a processing operation when detecting the position of a return light beam.

FIG. 3 is a schematic configuration diagram showing a spot of a return light beam incident on a conventional light receiving unit.

[Explanation of symbols]

 Laser diode 2 Grating 3, 8 ... Collimator lens 4 ...・ ・ ・ Beam splitter 5 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Objective lens 6 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Optical disk 7 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Wollaston prism 9 ・ ・ ・・ ・ ・ ・ ・ ・ ・ Multi-lens 10 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Light detector 11 ・ ・ ・ ・ ・ ・ ・ ・ Light receiver 31 ・ ・ ・ ・ ・ ・ ・ ・ 4 Split photodetectors 32, 33, 34, 35, light receiving elements

Claims (2)

[Claims] 1. A light source, a beam splitter for separating a light beam emitted from the light source and a return light beam of the light beam from an optical disc, and a plurality of light receiving portions are arranged in a matrix, and the beam splitter is And a photodetector that outputs a photodetection signal by receiving the returned light beam through the photodetector. The optical disc reading device is characterized in that when the radius of each spot is wide, the distance between the outer rings of each spot is shorter than the distance between the outer rings. 2. Based on the output from the light detecting means,
2. The optical disk reading device according to claim 1, further comprising a detection unit that specifies a plurality of spot regions of the return light beam.