JPS61158045A - Light head - Google Patents

Abstract

PURPOSE:To detect tracking without being affected by recording bits at the time of recording by separating a laser beam into three beams, i.e. 0-degree light and + or -1-degree light, using the 0-degree light as a laser beam exclusively used for recording or reading, and using either of + or -1-degree light as a laser beam exclusively used for tracking detection. CONSTITUTION:Half width pits 29a, 29b deformed according to tracking detec tion signals f1, f2 of different frequencies, i.e. modulated by tracking detection signals f1, f2 on side walls 28a, 28b are formed at the boundary between side walls 28a, 28b of a recording track 26. After dividing the laser beam into three beams of 0-degree light and + or -1-degree light, the beams are irradiated alongh the recording track. Recording or reproducing is made by the 0-degree light, and at the same time, the level difference between tracking detection signals f1, f2 included in the output signal of a light receiving section that receives reflected light of either of + or -1-degree light is outputted as a tracking error signal.

Description

[Detailed Description of the Invention] <Field of Industrial Application> The present invention relates to an optical device used for recording information on an optical recording medium or reading recorded information.

In particular, the present invention relates to an optical head that allows reliable tracking and king control to be easily obtained.

<Prior Art> In recent years, with the rapid development of optical recording and its reproducing technology, various optical information recording and reproducing devices such as optical video disc players, compact disc players, and video file devices have been developed7. An information optical recording/reproducing device records information by deforming or discoloring the optical recording layer by irradiating an optical memory disk as an optical recording medium, for example, with a laser beam adjusted in g according to the recorded information, and recording information by deforming or discoloring the optical recording layer. In this method, recorded information is read by detecting changes in reflected and diffracted light in an optical recording layer due to irradiation with a weak laser beam.

Here, the optical head irradiates the recording frame with a laser beam and reads the diffracted and reflected light, and is an important part of the information optical recording/reproducing apparatus. This light is controlled by focus control to focus the laser beam on the optical recording surface of the optical recording medium, radial control to align the laser beam along the recording track, and radial control to align the laser beam along the tangent of the recording track. It is necessary to perform jitter control for movement in the direction.

Here, the commonly used optical head is l:f.
Recording is performed by irradiating the recording trunk with a laser beam modulated according to the recorded information, and during playback, a one-beam method is used in which a laser beam with minute energy is irradiated onto the recording trunk and changes in the reflected and diffracted light are extracted. something is being used. In tracking control in this case, for example, the reflected light is received in parts in the tracking direction, and the difference between the two received light signals is determined to extract a tracking error signal corresponding to the deviation with respect to the recording track groove. The tracking error signal is then supplied to the tracking control circuit to control the objective lens actuator, thereby moving the objective lens and aligning the laser beam with the recording trunk.

<Problems to be Solved by the Invention> However, ``With the second configuration, when using a one-beam system for light, it is affected by the recording bit rate at the time of recording, and also by Since it is strongly influenced by the tilt, there is a problem that sometimes stable tracking servo cannot be obtained.

In order to solve such problems, the present invention deforms both the boundary portions of the recording track and the groove, thereby generating tracking detection signals f, , f2 of mutually curved frequencies. The optical recording medium on which is recorded is divided into three beams: 0-order laser beam and ±1 & light, and then irradiated along the recording track, recording or reproduction is performed with the 0-order light, and +/-1 Tiger and king detection signal Rf included in the output signal of the light receiving section that receives reflected light from either one of the following light beams
1 and f2 is output as a tracking error signal.

In the optical system configured in this way, the laser beam is separated into three beams: the zero-order light and the ±1& beam, and the zero-order light is used as a recording or read-only laser beam. , ±1st-order light is used as a laser beam exclusively for tracking and king detection, tracking detection can be performed without being influenced by recording pitches during recording. Also, by deforming both boundary portions of the recording track groove in advance, the recorded track 7
King detection signals υ-f+, f2 are received and extracted from the reflected light from either of the ±1st-order lights.Tara/Soking error is obtained by finding the level difference between these two King detection signals υ-f+, f2. Since the signal time is determined by the amount of output, it is not affected by the inclination of the disk as an optical recording medium.

<Embodiment> FIG. 1 is a diagram showing the main part of an embodiment of an optical head according to the present invention. In the figure, 1 is a laser diode that emits laser light.

The emitted light output is converted into parallel light by the collimating lens 2. Reference numeral 3 denotes an anamorphic prism made up of two prisms 3a and 3b, which converts the laser beam supplied via the collimating lens 2 into a perfect circle. 4 is a polarizing plate used as a polarizer, and 5 is a diffraction grating that separates the laser beam supplied through the polarizing plate 4 into three beams: 0th order light and ±1st order light, whose energy ratio is ±1st order. For example, the ratio is set to 10:1 so that the light does not affect the optical recording medium. , 6 is a prism beam splitter 7 is a diffraction grating 5, and a laser beam of 0th order light and ±1st order light supplied via the prism beam splitter 6 is provided inside an objective lens actuator 8. a 90′ mirror that supplies the objective lens 8a;
9 is a prism beam spring 1. 10 is a prism beam splitter that divides the output light of the focusing lens 9 into two; 11
is a cylindrical lens that focuses the split output light from the prism beam splitter 10 in only one direction and supplies it to the first light receiving section 12. For example, as shown in FIG. 2, the first light receiving section 12 includes a main light receiving section 13 that receives the reflected light of the 0th order light beam divided into four parts, and a main light receiving section 13 that receives the reflected light of either the ±1st order light beam. It is composed of a sub-light receiving section 14. Reference numeral 15 denotes a polarizing plate as an analyzer that extracts only the component of the target polarization plane from the other divided output light from the prism beam splinter 10 and supplies it to the second light receiving section 16.

FIG. 3 shows a Lutra/King control circuit that controls trunking using the output signal of the sub-light receiving section 14 shown in FIG. In the same figure, 17 is a buffer amplifier that amplifies the output signal of the sub-light receiving section 14. 18. 19 is a signal from the output value 3 of the buffer amplifier 17, a king detection signal f+,
The bandpass filter 20, 2.1 extracts f2, and by detecting f2, the level of tiger and king detection signals f1,
22 is a differential amplifier that outputs a tracking error signal TE corresponding to the amount of tracking deviation by determining the difference between the two tracking detection signals F, , F2; 23 is a differential amplifier that outputs a tracking error signal TE corresponding to the amount of tracking error; After compensation, a tracking control signal is supplied to a tracking coil 24, which is provided in the objective lens actuator 8 shown in FIG. 1 is a sectional view of a main part of an example of an optical memory disk on which information is optically written and read. FIG.

Here, the optical memory disk has a disc-shaped substrate made of a material that is transparent and has excellent heat resistance, and a recording trunk groove 26 is formed on the surface of the disk so as to be coaxial with the central hole. is provided. And this record...
The groove 26 has a depth of 0.05 to 0, tlILm, @0.4 to O, B gm, and a pitch of 1.6 to 2.8 LL.
It is made concentrically or spirally with a length of about m. Further, an optical recording material is deposited in a thin film form on the surface of the substrate 25 on the side where the recording trunk groove 26 is formed, thereby forming an optical recording/reproducing film 27, and on the back side thereof (not shown). A protective layer is laminated. 28a, 28b
is a side wall of the recording trunk 26, and this side wall 28a.

The boundary portion of the side wall 28b is deformed in response to the tracking detection signals f, , f2 having different frequencies, that is, the side wall 28
Half-width pits 29a are modulated by the tiger and king detection signals f, , f2 at a and 28b.

29b is formed. Reference numeral 30 indicates the focus point of the recorded information written along the central portion of the recording track groove 26 6 And the laser beams of the 0th order light and the ±1st order light are directed to this optical memory disk at a beam spot 31.3
As shown by 2a, 32b, the sidewall 28a of the recording track 26.

The size is such that it also includes the portion 28b.

In the optical head that is Sr& in this way, when the laser diode 1 generates a laser beam modulated according to the recorded information, this laser beam is converted into an upward beam by the collimating lens 2, and then converted into a true The light is supplied to a diffraction grating 5 via an anamorphic prism 3 provided for circularization and a polarizing plate 4 for regulating the plane of polarization. The laser light incident on the diffraction grating 5 is separated into 0th-order light and ±1st-order light at a predetermined energy ratio of, for example, 10:1, and is output. Here, the energy ratio of the 0th-order light and the ±1st-order light is set on the condition that the optical recording and reproducing film 27 of the optical memory disk shown in FIG. 4 is not affected by the direct projection of the ±1st-order light. There is. Then, they were separated by this diffraction grating 5. Three laser beams consisting of a 0th-order light beam and a ±1st-order light beam are supplied to a 90° deflection mirror 7 via a prism beam splitter 6, so that their direction is deflected by 90'. The inside of the objective lens actuator 8 is supplied with a branched objective lens 8a. Therefore, the objective lens 8a focuses these three laser beams and directs them as beam spots 31.31a and 31b onto the recording tracks and grooves 26 provided on the optical memory disk shown in FIG. That is, along the bottom of the recording track groove 26 there is a spot 31 caused by the zero-order light beam, and on both sides of the spot 31 along the recording track groove 26 there is a spot 31 along the recording track groove 26.
The sub-light beams 32a and 32b are arranged in parallel. Since the energy of the 0th-order light beam is set to be sufficiently high, optical recording and reproducing 11927
The pits 30 corresponding to the recorded information are recorded optically (including magneto-optically).

On the other hand, since the irradiation spot diameter of the 11th-order light beam is set to be relatively large, half-width pits 29a for tracking detection are provided on both side walls 28a and 28b of the recording track groove 26.

The spot irradiation is applied to a range including the portion 29b. Then, the reflected light from the optical recording/reproducing [26] of the 0th-order light and the 11th-order light beam is returned to the prism beam splinter 6 via the objective lens 8a and the 90° Schiller 7, and thereby separated. The separated return lights are focused by a focusing lens 9 and then separated by a prism beam splitter 10, one of which is supplied to the first light receiving section 12 via a cylindrical lens 11, and the other. The divided light is supplied to the second light receiving section 16 via the polarizing plate 15. Here, since the first light receiving section 12 is constituted by the main light receiving section 13 and the sub light receiving section 4 as shown in FIG. The sub-light receiving section 14 receives one of the returned lights due to reflection of the 11th-order light beam, for example, 1
Receives the returned light of the primary light beam. The main light receiving unit 13 then supplies each output signal obtained by receiving the reflected light of the zero-order light beam into four parts to a focus control circuit and compares the same, thereby determining the focus state from the shape of the light reception pattern and performing focus control. In addition, since the 11th-order light beam is irradiated onto a portion including the entire width of the recording track groove 26, the return light reflected from the portion includes tracking detection signals recorded by the half-width pits 29a and 29b. f, , f2 are included. Therefore,
The output signal of the sub-light receiving section 14 is amplified in a Bachau amplifier 17, and then supplied to band pass filters 18 and 19, where tracking detection signals f+ and f2 are extracted, respectively.

In this case, the tracking detection signal f1. f2 is.

A side wall 28a located in the tracking deviation direction.

The one recorded on the 28b side has a larger amplitude. Therefore, these two tigers, King detection No. 4A f,...
f2 is a DC level tracking detection signal f1 in the detection circuits 20 and 21, respectively.

When converted to f2, both signals are transferred to the recording track/track groove 26.
This represents the relationship between the side walls 28a, 28b and the +1st order light beam. However, these tracking detection signals f, . . . f2 alone cannot be used as a tracking error signal because they are affected by the vibration of the optical memory disk. For this reason, the difference between the two tracking detection signals f, f2 is determined in the differential amplifier 22, so that the influence of the surface runout is removed, and a tracking error corresponding only to the amount of tracking deviation is generated. A signal is extracted. The tracking error signal 57E extracted in this manner is subjected to phase compensation in the 1-phase compensation circuit 23, and then supplied to the tracking detection coil 24 as a tracking detection signal. When a tracking control signal is supplied to the tracking coil 24, the generated magnetic field moves the objective lens 8a in the direction in which the tracking control signal decreases, thereby generating a zero-order optical laser as a main beam for the recording track groove 26. - Beam on-track control will be performed.

Next, when reading recorded information, a zero-order light beam, which is a main beam of laser light generated from the laser diode 1, is directed to the optical recording/reproducing film 27 of the optical memory disk.
reduce its energy to the extent that it does not affect the

For example, if the laser output during recording is 30I1W, it is reduced to about 3IIllI. Now, if we lower the laser power.

Although it seems that there will be a problem with tracking control using the 11th-order light beam as a sub-beam, in reality, since the dynamic range of each light-receiving element is extremely wide +1/), there is no problem at all, and the advantage is that thermal noise is reduced. even occurs. Therefore, tracking control using either of the ±1st-order lights is performed with high precision and in a stable state, as in the case of recording.

On the other hand, the - part of the reflected light of the 0th order light as the main beam is divided in the prism beam splinter 10 and then rotated and polarized in the polarizing plate 15 as an analyzer, which divides the returned laser light into four parts. It is also possible to add and extract the output signals of the main light receiving section 13 depending on the configuration.

In addition, during playback, the tracking detection signal f by ±1st order light,
, f2 becomes difficult to extract. Since the tracking detection signals f, , f2 are included as high-level signals in the output signal of the second light receiving section 16 or the total addition output signal of the main light receiving section 13, 0 as main beam
It is also possible to switch to tracking control using secondary light.

<Effects of the Invention> As explained above, the optical head according to the present invention separates l laser beams into three laser beams consisting of zero-order beams and ±first-order beams and opens them onto an optical recording medium. Recording is performed using the O& light laser beam, and reading is performed using the energy-reduced light, and ±1st-order light is spot irradiated onto a range including the entire recording track area.

Therefore, by detecting the reflected light of either one of the ±1st-order lights as sub-beams, a tracking detection signal f, which is recorded in advance on both side wall portions of the recording track groove, is detected.
This means that f2 can be reliably read without being affected by the main beam and the information recording pit. By extracting the difference signal between the two tracking detection signals f, f2, a tracking detection signal that is completely unaffected by surface runout of the recording medium can be obtained.

Stable tracking control can be performed reliably and easily.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the optical head according to the present invention, FIG. 2 is a front view of the first light receiving section 12 shown in FIG. 1, and FIG.
4 is a circuit diagram showing an example of a tracking control system, and FIG. 4 is a sectional view showing an example of an optical memory disk on which recording and reproduction are performed by an optical head according to the present invention. l... Leniser diode, 2... Collimator lens, 3... Anamorphic prism, 4, 15... Polarizing plate,
5... Diffraction grating, 6.10... Prism beam splitter-17... 90° mirror, 8... Objective lens actuator, 8a... Objective lens, 9... Focusing lens, 11... - Cylindrical lens, 12... First light receiving section, 13... Main light receiving section, 14... Sub light receiving section, 1
5... Second light receiving x l 7... Buffer amplifier, 1
8.19...Bant pass filter, 20.21...
Detection circuit, 22... Differential amplifier, 23... Phase compensation circuit, 24... Tracking coil. Applicant: NEC Home Electronics Figure 1 Figure 2

Claims (1)

[Claims] By deforming both side boundary portions of the recording track groove, tracking detection signals f_1 of mutually different frequencies are generated.
. A tracking error signal is extracted by determining a difference signal between the tracking detection signals included in the output signal of a light receiving section that performs recording and reproduction and receives reflected light from either one of the ±1st-order light beams. and a light head.