JPS6344325A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To perform a correct optical axis control regardless of whether recording is already executed or the recording is not yet executed by dividing a tracking detector into at least four and using respectively the output of two detectors at the central side and two detectors at the outside. CONSTITUTION:For the output of two detectors at the outside of a tracking detector 23, the difference of the distribution strength of a reflecting primary diffracted light is detected by a differential amplifier 24 and the position control of a tracking element 24 is performed through a phase compensating circuit 24, a loop switch 26 and a driving circuit 27. On the other hand, for two central outputs of the detector 23, the difference of the distribution strength of a reflecting zeroth-order diffracted light is detected and the control of an optical axis control motor 8 is executed through a phase compensating circuit 30, a loop switch 31 and a driving circuit 7. Thus, the fine inclination of respective recording tracks can be detected one by one and the correct optical axis control can be executed regardless of whether reading is already executed or the reading is not yet executed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical information recording and reproducing device that records and reproduces information using a light source such as a laser, such as a video disc, CD, or optical card, and particularly This invention relates to the optical axis control device.

(Prior Art) Devices that record and reproduce information using lasers are (1) non-contact and have a long lifespan.

(2) High density.

(3) High-speed random access is possible.

Recently, many disk devices and card-type devices that can record and reproduce document files, image files, data files, etc. have been proposed for consumer use such as video disks and CDs.

In such a device, the recording surface has approximately 1. A focus control means for accurately focusing a spot with an OPM of 8 degrees and preventing the recording/reproducing spot from being affected by surface wobbling, etc., and a focus control means for accurately focusing a signal track with a pitch of 1.5 to several μm. Tracking control means for tracking the spot is always included.

Furthermore, in recent years, a control device for making the angle between the recording surface and the incident light beam constant and reducing the aberration of the focused spot on the recording surface has been disclosed in Japanese Patent Application Laid-open No. 177434/1982 and Japanese Utility Model Application No. 60-1999. This is proposed in Publication No. 9018 and the like.

The operation will be briefly explained below using the drawings.

11 [g is a block diagram of a conventional example, l is a recording medium such as a disk, 2 is a head, and includes a light source, the aforementioned focus control means, a detection element and a drive element for the tracking control means, etc. However, it will not be detailed here. 3 is a head support fitting, which is located near the center of the objective lens that emits the laser, as shown in the figure.

The head 2 is supported in a rotatable state in the left-right direction (arrow direction). 4 is a light source such as an LED, and the light source 4 is a light source such as an LED.
It emits parallel or divergent light.

The light reflected from the disk surface is guided to the detectors 5a and 5b, and the difference in the amount of light is detected by the differential amplifier 6 to measure the perpendicularity between the disk and the head, and then transmitted through the motor drive circuit 7. , optical axis control motor 8. A mechanism such as a 99-split screw nut 10 for vertical driving is driven to maintain the verticality at any radial position of the disk. In the figure, reference numeral 11 is a transfer table that supports the entire head, and a feeding motor 14. The radial movement of the head is controlled by a feed mechanism such as a feed screw 139 and a split nut 12. A signal from the tracking control means described above is inputted to the feed motor 14 via a low-pass filter, and the tracking control element is controlled to always operate at the center of the dynamic range.

In this way, by maintaining the perpendicularity between the disk and the head, crosstalk with adjacent tracks due to aberration of the spot on the recording surface and deterioration of the frequency characteristics of the detection signal are reduced. Furthermore, the reflected optical path changes depending on the inclination of the disk surface and moves on the tracking detection detector, thereby reducing the occurrence of tracking offset.

(Problem to be Solved by the Invention) However, in the above configuration, in order to maintain the angle between the disk and the head, the LED provided on the top of the head is
4 and detectors 5a and 5b, 1) In a device that performs recording and reproduction by changing the reflectance such as by changing the phase of the recording material or by drilling holes, the amount of reflected light changes near the boundary between the recorded area and the unrecorded area. 2) Since LEDs and detectors are exposed to the outside air, they are susceptible to dust and temperature changes. 3) They are susceptible to scratches and other disk surface conditions. 4) LEDs and detectors Because of this, there were problems such as an increase in the number of parts and an increase in cost.

(Means for Solving the Problems) In order to solve the second problem, the optical information recording/reproducing apparatus of the present invention divides the detector for detecting the tracking signal into at least four parts in the same direction, and divides the detector into four parts in the same direction. The tracking control means is operated by the output of the detector, and the optical axis control means is operated by detecting the distribution intensity difference of the reflected O-order diffracted light by the two middle detectors.

(Function) With the above-described configuration, the present invention directly measures the intensity distribution of the light reflected from the disk recording surface, and controls the distribution of the 0th order diffracted light so that it becomes uniform across the dividing line of the detector. In order to correct the tilt of the optical axis, the control target is not the surface of the disk, but the subtle tilt of each recording track can be detected, allowing extremely accurate optical axis control regardless of recorded or unrecorded data. becomes possible. Furthermore, the detector for detection is built into the head, making it less susceptible to the effects of dust and the like, and the protective film makes it less susceptible to the effects of scratches and dust on the disk surface. Furthermore, since the configuration of the detector is simply a change in the division of a conventional tracking detector, no extra parts or space are required.

(Example) An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the first embodiment, and the same components as those described in the conventional example are indicated by the same numbers and will not be described in detail here.

Reference numeral 21 denotes a tracking element, which causes the light beam emitted from the objective lens 22 to follow a desired track, and is a driving element for a tracking servo. Reference numeral 23 denotes a four-part detector for tracking servo, and the reflected light from the disk is guided onto the detector via optical parts such as a beam splitter and a lens, which will not be described in detail here. Reference numeral 24 denotes a differential amplifier, which takes the difference between the outputs of the two outer elements on the detector 23, into which most of the first-order diffracted light of the reflected light enters. The positional relationship between the light beam and the signal track is detected by the far field method, and the phase compensation circuit 25. Loop switch 26. The position of the tracking element 21 described above is controlled via the drive circuit 27, and these elements form a tracking servo loop.

The principle of signal detection described above will not be discussed here as it will be explained later.

The two detectors at the center of the detector 23 mainly receive reflected 0th-order diffracted light, and the divided intensity indicates the inclination of the disk. , a phase compensation circuit 30 such as lead compensation to ensure stability. loop switch 3
1. Through the drive circuit 7, the optical axis control motor 8 described above controls the relative angle between the head and the disk to be kept constant. In FIG. 1, (a) and (b) are control 0N10FF commands for each loop, and (a) is not shown here, but after confirming that the focus servo system has pulled in,
A command signal to close the tracking loop is input from a command device such as a microcomputer, and in (b), after confirming that the aforementioned focus and tracking loop are stable, a signal to close the optical axis control system is input from a command device such as a microcomputer.

Next, a signal detection method for optical axis control according to the present invention will be explained with reference to the drawings.

FIG. 2 is a schematic diagram of a reflective optical system in the head,
The light flux shown by a solid line shows the case where the light flux and the reflecting surface are perpendicular, and the light flux shown by the broken line shows the case where the above relationship is slightly tilted by θ°. Also, on the right side, changes in the distribution intensity on the detector are shown.

In Figure 2, A: In the diagram shown by the optical path, 34 is λ
/4 plate, and the polarization plane of the light beam changes by passing through the λ/4 plate twice in the round trip, and the reflected light changes its optical path to the detector 23' side by the polarizing beam splitter (PBS) 35, and then passes through the condenser lens. 36 onto the detector 23'. The reflecting surface in Fig. 2 is shown assuming that it is a flat surface, and by tilting the reflecting surface by θ, the center of the light intensity distribution on the detector is shifted by ΔX as shown in Fig. B, and in this example It no longer coincides with the center line of the two-part detector 23'. This is due to the inclination θ of the reflecting surface 33.
This indicates that an offset occurs in the detection signal.

Next, the principle of detecting a tracking signal in the apparatus of the present invention will be explained using FIG. This method is called the far-field or push-pull method, and is widely used in recording/playback optical disc devices because it has high light utilization efficiency in the optical head and is simple in configuration. Since the tracking signal is detected based on the difference in the distribution strength of the field, it has the disadvantage of being susceptible to the above-mentioned slope. In Fig. 3, the center diagram indicated by If , the signal becomes 0. On the other hand, T1. As shown in T, when the center of the optical spot deviates to the left or right with respect to the center of the signal track, a difference occurs in the distribution intensity of the detector d□lct, and a tracking signal corresponding to the track deviation can be detected. The tracking signal described above is due to the first-order diffracted light of the reflected light, and appears at a point slightly shifted from the center of the detector. What is that distance?

Proportional to light source wavelength/track pitch. Furthermore, the amplitude and distribution shape are affected by the reflectance of the 5 reflecting surfaces, the track shape, etc., but in any case, in the case of the positional relationship shown in T□, it is symmetrical at d t + d2, so a stable tracking signal can be detected. can do.

FIG. 4 is a schematic diagram showing the distribution intensity when the reflecting surface C' is tilted by θ in the positional relationship shown at T2 in FIG. Since the reflected optical path shown by the broken line is shifted from the incident light shown by the solid line, the center of the distribution intensity is shifted by ΔX from the center of the detector as in Figure 2, and the actual tracking signal is However, the control loop operation results in the spot tracking a point that is slightly offset from the center of the track, resulting in a decrease in the information signal amplitude and worsening of Talostalk due to signals from adjacent tracks. .

Figure 4 shows the distribution intensity near the center of the detector when the reflecting surface is tilted, and the balance near the center of d, d4 is shown on a detector divided into four parts. It can be seen that the two central detectors can obtain signals related to the zero inclination of the reflective surface without being significantly influenced by the tracking signal represented by d+dz because the angle is distorted as shown by the diagonal lines.

FIG. 5 schematically shows the far field pattern on the detector indicated by the arrow in FIG. 4. Here, a state in which the perpendicularity between the reflecting surface and the light beam is maintained will be explained. G
shows the pattern on the surface of the detector, C1 is the O-order diffracted light, and c2 is the left and right first-order diffracted lights, which are projected onto the detector in a substantially semicircular shape limited by the objective lens.

As shown in FIG. 5, by dividing the detector so as not to be affected by the first-order diffracted light c2, a signal proportional to θ of the reflected light is transmitted to d3. Good detection can be achieved by taking a differential of d4.

An example of the division of the aforementioned detector is shown in FIG.

As shown in J, ~: I4, the number of divisions does not necessarily have to be four, nor does it need to be divided along a straight line. Fifth
As shown in the figure, care should be taken to reduce the influence of the first-order diffracted light c2, which becomes the tracking signal, as much as possible.

Next, a second embodiment will be described using FIG. 7.

In contrast to the one shown in Fig. 1 which controls the inclination of the head, the disc motor 37 is controlled by an optical axis motor 8' fixed to the chassis 38, a screw 9' and a split nut 10'. Since the support fitting 3' and the optical axis motor 8' are fixed to the chassis 38, the configuration of movable parts such as the head and the transfer table can be made very simple.

The detection method in the second embodiment is exactly the same as that in FIG. 1, so it will not be described in detail here.

If necessary, it is also possible to add a limit switch to limit the amount of movement of the optical axis motor 8', an initial switch to detect the initial approximate position, etc. to ensure stability when starting the device. It is.

Further, depending on the mechanism configuration, the optical axis control operation does not need to be operated all the time, and there is a method in which the optical axis control operation is fixed at an average value between the inner circumference and the outer circumference. Furthermore, in the case of this average value method, the influence of the first-order diffracted light can be further reduced by using mirror surfaces such as the outermost periphery where no tracks exist, or by omitting tracks at necessary locations on the disk and track positions where some mirror surfaces are provided. It is also possible to improve accuracy by

Next, a third embodiment will be described using FIG. 8.

39 and 40 are adder circuits that add the outputs of the two outer detectors and the two central detectors of the detector 23. 41 is a comparator for comparing the outputs of the adder circuits 39 and 40;
2 is a polarity determination circuit that determines the polarity of the comparator, and 43 is a level determination circuit that determines the output level of the comparator. 44
is a polarity switching circuit, which selectively uses a 1-inverting amplifier or a non-inverting amplifier according to the output of the polarity determining circuit. 45 is a gain switching circuit, which is realized by an attenuator circuit using a VCA (voltage control amplifier), an analog 8W, or the like.

The necessity of gain switching will be briefly explained using FIG. 9 and subsequent figures.

FIG. 9 shows the far field distribution on the detector with respect to the track shape. The track shape is w
1nid rack width approximately 0.7μff1. W, the NiDrack width is approximately 1.0 μm, the pitch is 1.6 μm, the spot diameter is 1.1 μm, and the track depth is approximately λ/8. As can be seen here, when the track width changes, the distribution of the far field pattern changes, resulting in a difference in the signal levels detected from the detectors d, d4. Figure 10 schematically shows the relationship between the far field pattern and the detector when the disk is actually tilted by 0. If we pay attention to the differential outputs of d and d4, which detect the amount of tilt, W
It can be seen that a larger signal can be obtained with the wzh rack than with the yo truck. This indicates that the sensitivity for detecting tilt changes depending on the track width. However, by comparing the intensities of the 0th-order diffracted light and the 1st-order diffracted light using the output of the comparator 40 described above, a change in the far field pattern can be detected, and the gain switching circuit 45 can be controlled using the output of the comparator 40. This makes it possible to always automatically set the optical axis control gain to the optimum value in response to changes in sensitivity due to changes in track width.

Furthermore, although the case where the track depth is λ/8 has been described in FIGS. 9 and 10, the depth is not limited to λ/8. In the case of a disk with a depth close to λ/4, the 0th-order diffracted light of the far-field pattern is smaller than the 1st-order diffracted light, and the polarity of the differential output of d3 and d4 corresponding to the slope in Fig. 10 becomes λ/8. Although the case may be reversed, the polarity can be switched by the polarity determination circuit 43. In this way, the present system always enables optimum optical axis control regardless of the track width or depth of the disk. Also, in FIG. 8, the comparator 41. Although the explanation has been made using the polarity judgment circuit 42, level judgment circuit 43, etc., even more stable and highly accurate judgment and light can be achieved by A/D converting the output of the adder circuit 39, 40 and calculating using a microcomputer etc. It is also possible to realize axis control characteristics.

(Effects of the Invention) As described above, in the present invention, the detector for detecting the tracking signal is divided into at least four parts, and the outer two detectors obtain the tracking signal, while the inner two detectors obtain the tracking signal.
Recording is performed using an extremely simple method that uses two detectors to obtain control signals regarding the inclination of the recording surface and head to control the optical axis.

The optical axis of a recording/reproducing device using a material whose reflectance changes depending on whether it is unrecorded or not can be controlled very accurately.

Furthermore, unlike the conventional method, there is no need for an extra detection element, it is resistant to dust and scratches on the surface of the recording medium, the structure is simple, and it exhibits a large effect in terms of loss.

In addition, by comparing the sum of the outputs of the two outer and center detectors, it is possible to achieve optimal optical axis control even if the track shape changes. It is also possible to provide a compatible and flexible recording/reproducing device.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the first embodiment of the present invention, Fig. 2 is a schematic diagram of the optical system, Fig. 3 is a diagram of the principle of tracking detection, Fig. 4 is a schematic diagram of the influence of tilt, and Fig. 5 is a schematic diagram of the optical system. A schematic diagram of a pattern on a divided detector, FIG. 6 is an example of a detector shape, FIG. 7 is a diagram showing a second embodiment of the present invention, FIG. 8 is a diagram showing an embodiment (3) of the present invention, and FIG. 10 is a diagram showing the relationship between the track shape and optical axis detection polarity, and FIG. 11 is a diagram showing a conventional recording/reproducing device. DESCRIPTION OF SYMBOLS 1... Disk, 2... Head, 3... Support metal fittings, 4... LED, 5a, 5b... Detector, 6... Differential amplifier, 7... Drive circuit, 8
...Optical axis control motor, 9...Screw, 10.
... Split nut, 21... Tracking element, 22.
...Objective lens, 23...Detector, 24...
・Differential amplifier, 25... Phase compensation circuit, 26...
・Loop switch, 27... Drive circuit, 30...
・Phase compensation circuit, 31... loop switch, 37.
...Disk motor, 38...Chassis, 39, 4
0...Addition circuit, 41...Comparator, 42...-Polarity judgment circuit, 43...Level judgment circuit. 44...Polarity switching circuit, 45...Gain switching circuit. Patent Applicant: Matsushita Electric Industrial Co., Ltd. Figure 2 ML Schematic Diagram A: Destination W Route -0)
1. ＼ δ 8゛-・. Figure 5: Spit criminal? Patterns d1 to d4 on the 1-item taketer Fig. 6 Rikota 4th and 5th person, J width sex e

Claims (6)

[Claims] (1) a focus control means for focusing a light beam onto a signal recording surface; a tracking control means for causing the focused light spot to follow a desired signal track; and a focus control means for controlling reflected light or transmitted light from the signal recording surface; The tracking detector comprises a focus detector for detecting a control signal of the tracking control means, a head means including an optical system leading to the tracking detector, and an optical axis control means for controlling a relative angle between the head means and a signal recording surface. is divided into at least four parts by dividing lines in substantially the same direction, and the two outer detectors obtain a tracking signal for operating the tracking control means, while the inner two detectors operate the optical axis control means. An optical information recording/reproducing device characterized in that it obtains a signal for recording. (2) A patent characterized in that the focus control means includes focus pull-in detection means for confirming that the focus control means is operating normally, and the operation of the optical axis control means is started by the output of the focus pull-in detection means. An optical information recording/reproducing device according to claim (1). (3) comprising tracking pull-in detection means for confirming that the tracking control means is operating normally;
The optical information recording and reproducing apparatus according to claim 1 or 2, wherein the optical axis control means starts operation based on the output of the tracking pull-in detection means. (4) Claim (1) characterized in that the optical axis control means is operated in a specific area on the recording surface where no track exists or is interrupted.
The optical information recording/reproducing device according to item (2) or item (2). (5) After the focus pull-in detection means confirms that the focus has been pulled in, the optical axis control means is operated at a specific position between the start and end edges of the recording surface, and then the optical axis control means is fixed at the operating point at the specific position. Claims (1), (2), (3), and (4) are characterized in that:
The optical information recording/reproducing device according to any one of the above items. (6) First and second adding means that calculate the sum of the center two detector outputs and the outer two detector outputs of the tracking detector, and a comparison of the outputs of the first and second adding means. Claims (1) and (2) further comprising a means for switching at least one of the polarity and the gain of a signal for operating the optical axis control means as necessary based on the output of the comparison means. ), (3)
, (4), and (5).