JPH05205292A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To eliminate unstable operation of tracking control loop so as to obtain an optical head which generates no offset of tracking operation point due to the movement of tracking drive element by shifting the reflected light by the amount proportional to the shifting amount of objective lens in an optical recording and reproducing device. CONSTITUTION:Detectors d3a and d4a are located parallel to a tracking detector (d1a, d2a) 91 to detect the reflected light from a disc. The direct light from a light source is reflected on a reflector which is fixed on the bottom of an objective lens 5 or an objective lens holder 23, is detected by d3a and d4a of the detector 91, and synthesized into a tracking control signal through a differential amplifier 17 to form a tracking control loop. Thus, the tracking control loop with excellent tracking follow-up accuracy and stability can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for optically reading information recorded on a recording information medium such as a video disc, or for optically recording information on a recording information medium. An apparatus for reproducing and erasing, particularly optical recording information reproduction characterized by an optical system for obtaining servo signals and reproduction signals for applying various servos using reflected light from a recording information medium It relates to the device.

[0002]

2. Description of the Related Art An apparatus for recording / reproducing information on / from a disk-shaped recording medium (hereinafter referred to as a disk) or a card using a light source such as a laser is a non-contact type, has a long medium life, high recording density, and high-speed access. In recent years, many devices such as optical disc files and the like capable of recording and reproducing images, documents, data files, etc. have been proposed from those for reproduction only such as video discs and compact discs. There is. In such an apparatus, a focus control means for accurately focusing a spot of about 1.0 μm and an eccentricity of about several tens of μm by following a recording surface vibrating by several hundred μm due to surface deviation or the like. With a pitch of 1.2 to 1.2 provided in advance on a medium such as a disk having
A tracking control means for accurately following a track of 2 μm is always incorporated. As a signal detection method for operating the tracking control means, many proposals such as a three-beam method, a phase difference method, a far field method (or a push-pull method), a phase difference method, and a wobbling method have been conventionally proposed.

In the recording / reproducing apparatus in the above detection method, the information pit cannot be treated as a tracking detection signal because there are unrecorded tracks, or if the beam is split, the semiconductor laser power during recording cannot be sufficiently obtained. For these reasons, the far field method is generally used. The principle of the far field method is shown in FIG.
A brief description will be given with reference to FIG.

FIG. 6 is a block diagram of a conventional example, in which 1 is a light source, and a semiconductor laser, a He--Ne laser or the like is used. Reference numeral 2 denotes a collimating lens, which collimates a light beam from a light source, which is a divergent light, into a parallel light beam,
The light is incident on the disk 7 through the λ / 4 plate 4 and the objective lens 5 so that the disk 7 is focused. Since the focus control means for performing focus control is simple, description and illustration thereof are omitted here. 6 is a tracking drive element,
This is an electromagnetic coil that can move the objective lens in parallel in the direction that follows the fluctuation of the track. The reflected light from the disc is λ
By passing through the / 4 plate 4 twice, the optical path is changed by the PBS 3, and the light enters the tracking light detection element (hereinafter referred to as tracking detector) 9 through the condenser lens 8. The size of the incident light beam on the detector is 100 to several hundreds μm, and 1.
A spot around 0 μm is called a near-field pattern, whereas it is called a far-field pattern (far-field image) and is also used as a type name of a detection method. The tracking detector 9 is divided into two regions, d1 and d2, and the output thereof is a differential amplifier 10, a phase compensation circuit 11,
It is supplied to the above-mentioned tracking drive element 6 via the loop switch 12 and the drive circuit 13, and constitutes a tracking control loop. The detection principle of the tracking control signal described above is shown in FIG. FIG. 7 shows the detector d1, due to the positional relationship between the signal track C and the incident light beam D (T1 to T3).
It is shown that the distribution intensity on d2 changes.
The unbalance amount of the distribution intensity is detected by the differential amplifier 10 and is controlled so that the track and the light flux are always positioned as in T2.

However, as shown in FIG. 6, since the parallel light incident on the objective lens has a distribution intensity,
When the lens movement amount ΔX becomes large, the reflected light spot with the tracking detector also moves in a large amount in proportion to ΔX. Therefore, as shown in FIG. 7, even when the track is correctly tracked, the center of the distribution on the detector is increased. Shifts from the detector division line by an amount proportional to ΔX, so that the above-described control operation causes the distribution intensities to be balanced, and as a result, the tracking operates at a point having an offset.

FIG. 8 is a schematic diagram in which this state is three-dimensionally written. As the objective lens 5 moves from the position indicated by the solid line to the position indicated by the wavy line by following the fluctuation of the track, the spot on the disk moves by ΔX. As a result, it can be seen that the reflected optical axis also fluctuates as shown by the wavy line and shifts on the detector 9 by an amount proportional to ΔX. The amount of fluctuation on this detector becomes the above-mentioned offset component.

Focusing on such a problem, a proposal has been made to reduce the effect, and the above-mentioned offset is greatly affected by the 0th-order diffracted light appearing near the dividing line in the center of the detector during the far-field distribution intensity. Therefore, the light only near the first-order diffracted light is used as the tracking control signal.

[0008]

However, as another problem of the far field method, the tracking control loop is the above-mentioned track following loop, and the objective lens moves in the direction parallel to the disk as shown in FIG. By moving the reflected light on the detector by an amount proportional to the above amount, a position control loop of the light flux on the detector is also constructed. In the above-mentioned FIG. 7, in the case of a mirror surface where no track exists on the disk, d1 , D2
The tracking control loop operates so that the light beam is incident on the center of. Therefore, the polarities of the tracking control loop and the position control loop of the luminous flux are reversed depending on which of the polarities of the signal track (the convex portion or the concave portion of the track) is selected, and as described above, the luminous flux is centered on d1 and d2. Is not stable, the position control loop becomes oscillating polarity, and when operating at the end of the detection dynamic range due to transient response of the tracking control loop or due to large eccentricity, the ratio of the position control loop increases and the tracking control loop There was a problem that the operation became extremely unstable.

[0009]

In order to solve the above problems, the present invention mounts a reflector on a part of the objective lens or on the bottom surface of the holder of the objective lens, and sets the tracking control signal detecting detector in the same direction. The tracking control means is operated based on the outputs of the detectors which are divided into at least four and whose ends are adjacent to each other. At the same time, the intensity distribution of the reflected light from the reflector attached to the above-mentioned objective lens is detected by the other two adjacent detectors. It is configured as follows.

[0010]

According to the present invention, with the above-mentioned configuration, a signal for reducing the influence of the above-described light beam position control loop by the output that detects the position variation on the detector that detects the intensity distribution of the reflected light from the reflector, or An extremely good tracking performance is realized by a configuration in which a signal for reducing the offset due to the modulation of the tracking signal due to the movement of the tracking drive element is obtained and is combined with the tracking control loop.

As a result, it is possible to sufficiently suppress the instability caused by the light beam position control loop and to prevent the offset of the tracking operating point due to the movement of the tracking drive element regardless of the signal track polarity of the disk. It is possible to realize a tracking control loop with extremely good tracking accuracy and stability.

Further, since the instability due to the difference in track shape and the difference between the two effects on the offset can be automatically set to the optimum state, it is possible to flexibly cope with the change of the track shape due to the improvement of the disk performance in the future. It is possible to provide a device that can. The present invention has the above-mentioned configuration.
The track following accuracy can be improved because the instability due to the light beam position control loop can be sufficiently suppressed and the offset of the tracking operating point due to the movement of the tracking drive element does not occur in any signal track polarity of the disk. It is possible to realize a tracking control loop having very good stability and stability.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A tracking control device according to a position embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a tracking control device according to the first embodiment of the present invention. The same components are assigned the same numbers as in the block diagram of the conventional example of FIG. 6, and description thereof will be omitted.

Reference numeral 14 is a head 14 in which optical components such as the above-mentioned semiconductor laser and lens are incorporated, and is driven and controlled by a feed motor 15 in the radial direction of the disk 7.
The feed motor 15 controls the low frequency of the tracking control loop described above, but the relationship is not shown.

The detector 91 is divided into four parts d1a to d4a in the direction in which the tracking signal is detected. The detectors d1a and d2a having two ends receive the reflected light including the first-order diffracted light from the disk 7, and A tracking control loop is constructed as in the example. The second two detectors d3a and d4a are set so as to receive the light flux reflected by a reflector 24 attached to a part of the outer circumference of the objective lens 5 or the bottom surface of the holder 21 holding the objective lens. .. At this time, the reflector 24 is attached to the bottom surface of the objective lens 5 or the holder so as to be directed toward the inner circumference side or the outer circumference side of the disk 7. The outputs of the detectors d3a and d4a are used by the differential amplifier 17 to detect only the difference in the distribution intensity of the reflected light from the reflector on the detector to cut low components due to the tilt of the disk and to reduce high frequency noise. Phase compensation circuit 18
A detection system of a correction loop is constituted by and is combined with a normal tracking control signal by the adder circuit 20 in the above-mentioned tracking control loop through the correction loop switch 19.
It constitutes a tracking control loop which is extremely little affected by the movement of the beam on the detector and the above-mentioned light beam position control loop.

Further, since the correction loop having the above-mentioned structure can accurately detect the movement of the lens itself, it can also be used as a position control system for the objective lens and conventionally used as a means for returning the center position of the objective lens such as rubber and spring. It is possible to omit the mechanical or magnetic center position returning means.
In the case of use as a center position returning means as described above,
Is the addition point 20 provided after the loop switch 12 or
It is necessary to branch the output of the differential amplifier 17 and add a phase compensation circuit having different characteristics and another switch to add the output to the subsequent stage of the loop switch 12.

Next, the correction operation of this embodiment will be described with reference to FIG. In FIG. 2, S1, S2, and S3 show a case where the center of the signal track is deviated from the optical axis center to the left and right. Since the amount proportional to the offset ΔX in the conventional example of FIG. 6 can be detected by the portions indicated by the detectors d3a and d4a, the tracking offset can be obtained by separating this signal and feeding it back to the tracking control loop with an appropriate gain. It is possible to stably follow the center of the track without causing the noise.

FIG. 3 shows the pattern on the detector in this embodiment, where C1 is the 0th-order diffracted light by the signal track, C2 is the 1st-order diffracted light, and C3 is the reflected light of the reflector, which follows the track center. When doing, it appears symmetrically as shown in FIG. Of these, in the present invention, d3
The a and d4a detectors detect the intensity change of only the reflected light. In this embodiment, d1a and d2
Although the detector in which a, d3a, and d4a are integrated has been described as an example, it is also possible to use a detector in which d1a, d2a and d3a, d4a are separated and independent.

Next, a second embodiment will be described with reference to FIG. In FIG. 1, the four dividing lines of the detector 91 for detecting the amount of movement of the objective lens 5 are arranged side by side, whereas the reflector 24a is provided around the objective lens 5 or the objective lens holder 21 as a whole or. Since the detector 92 is attached symmetrically with respect to the central axis orthogonal to the track direction of the objective lens, the dividing line of the detector 92 can be provided in a circular shape, and the detector adjustment can be performed regardless of the accuracy of the attachment angle of the reflector or the adjustment accuracy. It is designed to be able to do. In this case (d1b-
A signal for tracking control is given by (d3b)
The signal for the correction loop can be obtained by b-d4b).

If the signal recording power and the signal detection characteristics on the disc are acceptable, a small reflector as proposed by the super-resolution system or the like is provided at the center of the objective lens, and the central portion of the detector 92 is provided. It is also possible to make d1b and d2b small. In this case, (d3b-d4
In step (b), the signal for tracking control is (d1b-
The signal for the correction loop can be obtained by d2b).

Next, a third embodiment will be described with reference to FIG. This is because the reflector 24b is tilted with respect to the incident light and another detector 22 is used by using another detector 22 while the detectors of FIGS. 1 and 4 are shared or arranged at almost the same position as the detection detector of the servo system. The feature is that the amount of movement is detected independently without being affected by the first-order diffracted light at all. The configuration of the correction loop in FIGS. 4 and 5 is exactly the same except for the detection stage.

As described above, in the tracking control device of the present invention, the reflector is attached to a part of the objective lens or the bottom surface of the holder of the objective lens, and the reflector is attached to the objective lens in addition to the tracking control signal detecting detector. A detector for the correction loop that detects the intensity distribution of the reflected light is provided, and the detector arrangement, the spectroscopic means, and the detector shape are configured to accurately detect the position fluctuation of the reflected light on the detector due to the movement of the objective lens. is there.
The position fluctuation of the detector is suppressed by adding a correction loop that detects the position fluctuation of the beam on the detector independently and feeds back to the tracking loop with a polarity that suppresses the influence of the position fluctuation of the detector. It is possible to realize a good tracking state in which the beam center is always aligned with the track center.

Since the position fluctuation feedback loop as the correction loop becomes a component in the direction of decreasing the loop gain with respect to the tracking loop, the frequency characteristic of this loop has a fundamental frequency of the tracking loop (rotation frequency of the disk): Care must be taken to lower the gain to some extent or to devise the gain distribution so as to suppress only the beam fluctuation component on the detector. As an example of the optimum gain distribution adjustment method, the tracking signal is observed when the objective lens is forcibly oscillated by several tens of μm in the direction orthogonal to the track while the tracking loop is not operated and only the focus loop is operated. However, there is a method of adjusting the gain of the position fluctuation feedback loop so that the influence of the forced vibration of the objective lens is minimized. By this method, the optimum gain distribution can be realized relatively easily and accurately. As a result, the optical recording / reproducing apparatus of the present invention basically cancels the influence of the position fluctuation of each optical element, the drift of the tracking center due to the sensitivity fluctuation, and the influence of the beam movement on the detector in the fundamental wave, and the disturbance. In particular, it is possible to realize good tracking control in which the tracking polarity is always stable both on and between the grooves.

In the description of the embodiment, the optical disk device is used for explanation, but it is obvious that the present invention can be applied to the same device for optically recording and reproducing such as an optical card, a tape and a drum.

[0026]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, the reflected light from the reflector attached to a part of the objective lens or the bottom surface of the holder of the objective lens and attached to the objective lens other than the tracking control signal detecting detector. Compensation with a detector for the correction loop that detects the intensity distribution of the sensor, detects the position fluctuation of the reflected light on the detector independently, and feeds it back to the normal tracking loop with the polarity that suppresses the effect of the position fluctuation on the detector. With the extremely simple method of adding a loop, the effects of the movement of the objective lens and the effects of the light beam position control loop on the detector can be sufficiently reduced, so that a stable and highly accurate tracking control loop can be realized. , Its practical effect is very large.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an intensity distribution on a detector in an example.

FIG. 3 is a schematic diagram showing an intensity distribution on a detector in an example.

FIG. 4 is a block diagram of a detection system showing a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a detection system showing a third embodiment of the present invention.

FIG. 6 is a detection principle diagram of the far field method.

FIG. 7 is a schematic diagram of tracking offset

FIG. 8 is a diagram showing a positional variation of reflected light on a tracking detector when an objective lens moves parallel to a disc.

[Explanation of symbols]

 1 Semiconductor Laser 2 Collimator Lens 3 PBS 4 λ / 4 Plate 5 Objective Lens 6 Tracking Drive Element 7 Disk 8 Condensing Lens 9 Detector 10, 17 Differential Amplifier 12, 19 Loop Switch 14 Head 15 Feed Motor 16 Disk Motor 20 Adder Circuit 21 Objective Lens Holder 22 Detector 24, 24a, 24b Reflector 91, 92 Detector

Claims (4)

[Claims] 1. An objective lens for narrowing a light beam emitted from a light emitting element onto a recording medium, and a holder for supporting the objective lens, a reflector for reflecting a part of the light beam, and a light focused by the objective lens. In order to detect a tracking control signal that causes the spot to follow a desired signal track, a detection element that is divided into four in the same direction to separate and receive the reflected light from the recording medium and the reflected light from the reflector is provided. The detection element obtains the tracking control signal by a difference signal between two adjacent detection portions, and at the same time, a tracking guide groove for reflected light from the reflector by a difference signal between two other adjacent detection portions. Optical recording / reproducing, characterized in that the amount of movement in the orthogonal direction is detected and combined with the tracking control signal to perform tracking control of the objective lens. Location. 2. Around a holder for supporting an objective lens,
2. A shape in which a reflector for reflecting a part of the light flux emitted from the light emitting element is attached, and the reflected light from the reflector is separated and detected from the reflected light from the recording medium. Optical information recording / reproducing device. 3. A holder for supporting the objective lens in which the reflector is obliquely attached to at least one position in the tracking guide groove direction of the recording medium, and a detection element for detecting a tracking control signal from reflected light from the recording medium. A second detection element for detecting the reflected light from the reflector is provided at a position different from that, and the amount of movement of the reflected light from the reflector in the direction orthogonal to the tracking guide groove is detected and combined with the tracking control signal. The optical recording / reproducing apparatus is characterized by performing tracking control of the objective lens. 4. The optical recording / reproducing apparatus according to claim 1, wherein a reflector for reflecting a part of the light flux is attached to the objective lens.