JPH0135296Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an optical recorded information reading device, and in particular, an optical recorded information reading device having a servo system that maintains an orthogonal relationship between the optical axis of a recorded information reading light beam and the recording surface of a recording medium. Regarding equipment.

If the angle between the optical axis of the recorded information reading light beam and the recording disk, which is a recording medium, deviates from a right angle, information from adjacent recording tracks will leak, resulting in a so-called crosstalk phenomenon. There are various causes for the angle between the two to deviate from the orthogonal relationship; for example, the recording disk may become umbrella-shaped due to changes over time, or the disk rotation axis may become tilted due to changes in the shape of the deck of the playback device. The occurrence of crosstalk is inevitable since it is a problem that occurs after the product is shipped.

Therefore, a servo system is provided that electrically detects the crosstalk and always accurately maintains the orthogonal relationship between the optical axis of the light beam and the recording disk to reduce the crosstalk. This technique is disclosed in detail in Japanese Patent Application Laid-Open No. 186237/1983. This example is applied to a playback device for a recording disc recorded using the CLV (Constant Linear Velocity) method, and in a recording disc using the CAV (Constant Angular Velocity) method, the synchronization signal recording section extends over the entire recording track. Crosstalk is detected by utilizing the fact that in the CLV method, they are not aligned on the same radius line, whereas in the CLV method, they are arranged on the same radius line. That is,
In the CLV method, the amount of crosstalk is detected by detecting leakage components of the same basic signal information of adjacent tracks.
The optical axis of the reading light beam is tilted so that this amount is eliminated.

Such a method has disadvantages such as that the electric circuit for detecting crosstalk is complicated and expensive, and is limited to the CLV method and cannot be applied to the CAV method.

Another method is the technique disclosed in Japanese Unexamined Patent Publication No. 179954/1983. The system is schematically shown in FIG. 1, and is provided with an objective lens 3 having an optical axis 1 and converging a recorded information reading light beam onto a recording surface 2 of a recording disk. On the other hand, a detection auxiliary beam light source 4 is provided to detect a deviation in the orthogonal relationship between the optical axis 1 and the recording surface 2, and this auxiliary beam is irradiated onto the recording surface 2 through the objective lens 3. The reflected light is configured to enter the pair of light receiving elements 5 and 6 via the objective lens 3 again. Here, if the recording surface 2 is perpendicular to the optical axis 1, the auxiliary beam is reflected in a direction symmetrical with respect to the optical axis and returned to a position symmetrical with respect to the light source 4 and the optical axis 1, as shown by a solid line. On the other hand, if the recording surface is inclined as shown by the dashed-dotted line or the broken line, the auxiliary beams are reflected as shown by the dashed-dotted line or the broken line, respectively.

Therefore, light receiving elements 5 and 6 are provided for these reflected beams as shown in the figure, and the light receiving outputs are supplied to a differential amplifier 7 to derive a detection output.
This detection output is subtracted from the reference signal 9 in the subtracter 8, and the optical axis tilting mechanism 10 is
The orthogonal relationship between the optical axis and the recording surface is maintained by driving the optical axis.

This technique has the following drawbacks because the auxiliary beam, which is parallel light, is irradiated onto the recording surface through the objective lens.

First, unless the focus servo system is tracking stably, the servo system (hereinafter referred to as tilt servo) that makes the optical axis 1 of the recorded information reading light beam perpendicular to the recording surface cannot be operated, so the focus servo cannot be locked in. If this is not done, the tilt servo cannot be lowered, and in extreme cases, not only the tilt servo but also the focus servo may not be able to be retracted. That is, in order for the auxiliary beam irradiated parallel to the optical axis 1 to be reflected at the correct position on the light receiving elements 5 and 6, the disk surface must be located at the focal point of the lens, and the disk surface must be located at the focal point of the lens. Even if the auxiliary beam approaches the photodetector, the irradiation position of the reflected light of the auxiliary beam on the photodetector will be lower (shifted to the left and right in the figure). Therefore, an erroneous output is generated from the differential amplifier 7, and the optical axis 1 is unnecessarily tilted.

Therefore, if the optical axis is extremely tilted, the position of the reflected light of the information detection beam to the detector (not shown) that supplies the control signal to the focus servo or tracking servo will change, causing the servo This is because an unnecessary DC component is superimposed on the error signal used for lock-in.

Furthermore, as pickups become smaller, it is difficult to arrange an optical system used for tilt servo inside the pickup. This is because by irradiating the auxiliary beam onto the objective lens of the optical beam for reading recorded information, the viewing angle of the lens used for the optical beam for reading recorded information is narrowed, which becomes a constraint in the design of the optical system. There are drawbacks.

The purpose of this invention is to provide an optical recording information reading system with an extremely simple configuration that can always detect the orthogonal relationship between the recording surface and the optical axis of the optical beam for reading recorded information, regardless of the operation of the focus servo system. The purpose is to provide equipment.

The optical recorded information reading device according to the present invention detects a deviation in the orthogonal relationship between the optical axis of the recorded information reading light beam and the recording surface, and controls the tilting means that tilts the optical axis according to this deviation. A device having a tilt servo system configured to maintain an orthogonal relationship,
Its features include a base member that tilts in the radial direction of the recording disk in conjunction with the tilting means;
a light emitting means for irradiating emitted light toward a recording surface; an adjustment holding mechanism for holding the light emitting means with respect to a base member by making the light emitting axis angle of the light emitting means adjustable;
The light receiving means is provided on the base member and receives the light reflected by the recording surface of the light emitted from the light emitting means, and the detecting means detects a deviation in the orthogonal relationship based on the output of the light receiving means.

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention, in which the recording disk 11 is shown as being tilted with respect to the horizontal line due to deformation. An optical head unit 12 is provided for optically reading the recorded information on the recording disk, and this head unit 12 is connected to the supporting member 1.
3 so as to be rotatable about a rotation shaft 14. This support member 13 is a slider 15
The slider 15 is used to move the head unit 12 in the radial direction of the disk 11. For example, a pinion gear 17 is designed to mesh with a rack portion 16 formed in a part of the slider 15, and the slider 15 is controlled to move in the disk radial direction by driving the pinion gear 17 by a slider motor 18. be. A normal feed signal generation section 20 is provided which detects a DC component included in an error signal from a tracking error signal generator (not shown) and generates a normal feed signal for the slider. A high-speed feed signal generating section 21 is provided that generates a high-speed feed signal for the slider during a scan operation or the like. The outputs of these two signal generators are sent to a driver 19 via an adder 22.
is supplied to rotate the slider motor 18.

A light emitting element 23 to detect the inclination of the disk 11
The light receiving elements 24a and 24b are mounted on the head unit 12 as a base member, and the light receiving outputs a and b of the light receiving elements 24a and 24b are input to a differential amplifier 25, and this difference output c is sent to a driver 26.
The tilt motor 27 is driven via. A male threaded portion 28 connected to the rotating shaft of the tilt motor 27
and a female screw portion provided in a part of the optical head unit 12 are screwed together, and the motor 27
As the optical head unit 12 rotates, the optical head unit 12 is tilted at an arbitrary angle of inclination. The rotation axis forming the center of inclination at this time is the axis 1 of the support member 13.
It becomes 4. The spring S wound around the male threaded portion 28 and interposed between the optical head unit 12 and the slider 15 is for preventing backlash.

FIG. 3 is a perspective view of the optical head unit 12, and 29 is an objective lens. A recorded information reading light beam emitted from a laser light source inside the unit 12 is focused onto the recording surface of the recording disk 11 by the objective lens 29. The center of this objective lens 29 is located at the point where the optical axis 31 of the light beam and the rotation axis 14 intersect. A so-called focus actuator 30 is used to control the movement of the objective lens 29 in a direction parallel to the optical axis 31 so that the light beam is always converged on the recording surface.
is provided, which consists of magnetic circuits, coils, etc.

A straight line passing through the center of the objective lens 29 and the center of the light emitting element 23 is approximately parallel to the tangential direction of the recording track being reproduced, and preferably is closer to the convergence point of the light beam, that is, the information detection point when reading recorded information. The light emitting element 23 is attached at a position where it illuminates the preceding recording surface, and neither the emitted light from this light emitting element nor its reflected light passes through the objective lens 29.

Further, the optical axis 31 of the recorded information reading light beam and the emission optical axis from the light emitting element 23 are parallel to each other, and there is no problem even if they are treated as the same.

Figure 4 shows a light emitting element 23 that detects the disk inclination.
5 is a plan view showing the mounting structure of the light-receiving elements 24a and 24b, and FIG. 5 is a cross-sectional view taken along the line A-A in FIG.
FIG. 6 shows a sectional view taken along the line B--B in FIG. 4, respectively. In FIGS. 4 to 6, the light emitting element 23 is mounted on a substrate 32 and fixed to the center of a substantially T-shaped substrate holder 33. As shown in FIGS. Adjustment screws 35, 36, and 37 are provided at three ends of the substrate holder 33, passing through flat washers 34 and screwed into the optical head unit 12, and further around these adjustment screws and connecting the substrate holder 33 and the optical head unit. Adjustment screws 38, 39,
40 are interposed, and these constitute an adjustment mechanism that adjusts the height and angle of the light emitting element 23 in three-dimensional directions.

On the other hand, the light receiving elements 24a and 24b are connected to the substrate 40a,
40b, and is mounted symmetrically with respect to the light emitting element 23 on a substantially H-shaped substrate holder 42 fixed on the optical head unit 12 with screws 41a and 41b.

Here, when the axes of the light emitting element 23, the light source, and the lens are completely aligned, the optical axis of the emitted light from the light emitting element 23 is relative to the recording surface 2 of the disk, as shown in FIG. 7a. However, due to the manufacturing process of the product, misalignment between the axes of the light source and the lens is unavoidable, and as a result, the optical axis is aligned with the disc as shown in Figure 7b. An angular error Δθ will occur with respect to the recording surface 2. However, since the device of the present invention is equipped with the adjustment mechanism, the adjustment screws 36, 36, 37 can be appropriately adjusted to adjust the light emitting element 2.
By changing the angle 3, the angular error Δθ caused by the misalignment of the axes between the light source and the lens can be corrected.

The operation of the present invention with the above configuration will be explained using FIGS. 8 to 10. 8a to 8c are diagrams showing the reflection state of the luminous flux emitted from the light emitting element 23 according to the inclination of the disk, and FIGS. 9a to 9c are diagrams showing the reflection state as viewed from the disk side, respectively. be. In addition, FIG. 10 shows each light receiving element 24a, 24b.
FIG.
Figures a and b show the respective outputs of the light receiving elements 24a and 24b, and figure c shows the output of the differential amplifier 25. Points A, B, and C in FIG. 10 correspond to the states a, b, and c in FIGS. is vertical.

When such a vertical relationship exists, the light emitted from the light emitting element 23 is reflected by the recording surface of the disk 11 while being diverged, and is evenly irradiated onto the light receiving elements 24a and 24b. Therefore, the output levels of both elements are equal, and the output level of the differential amplifier 25 is zero.

On the other hand, when the disk 11 is deformed into an umbrella shape as shown in FIGS. 8a and 8c, the orthogonal relationship between the disk and the optical axis 31 is shifted. For example, in the case of FIG. 8a, the reflected light is incident only on the light-receiving element 24a, and its output level is maximum, and the output level of the light-receiving element 24b is approximately zero. Therefore, the output level of the differential amplifier 25 is maximum at positive polarity. On the other hand, Fig. 8c
In this case, since the reflected light is incident only on the light receiving element 24b, the output of the differential amplifier 25 becomes the maximum level of negative polarity.

Therefore, the output c of the differential amplifier 25 is a signal whose level and polarity change depending on the amount and direction of deviation from the orthogonal relationship between the disk and the optical axis 31. If closed-loop tilt servo is performed so that the differential output c becomes zero, the optical axis 31 of the light beam can always be made perpendicular to the disk 11, making it possible to eliminate crosstalk.
Note that if the light emitted from the light emitting element 23 has an intensity distribution such as a Gaussian distribution, the slope of the output characteristic of the differential amplifier becomes large and the detection sensitivity increases.
It becomes easy to select the size and arrangement of 4a and 24b.

The differential output of the differential amplifier 25 drives the tilt motor 27 and the optical head unit 12
is rotated around the rotation axis 14, so that tilt servo is performed.

In the above embodiment, the adjustment mechanism for holding the light emitting element 23 and adjusting the angle of the light emitting element 23 was constructed using three adjustment screws and three adjustment springs, but as shown in FIG. A configuration in which a spherical protrusion 43 is protruded from one longitudinal end of the substrate holder 33 and the protrusion 43 is supported by a spherical receiver 44 can also produce the same effects as in the above embodiment.
Further, as shown in FIG. 12, the light emitting element 23 and the light receiving elements 24a and 24b are configured to be mounted on the same substrate, and when the light emitting element 23 is mounted on the substrate, the reflected light from the disk is transmitted to the light receiving element 24a. ，
By performing soldering while monitoring the amount of light incident on the light emitting element 23b, it is possible to correct the angular error Δθ of the optical axis of the emitted light due to the misalignment between the axes of the light source of the light emitting element 23 and the lens. .

As mentioned above, according to the present invention, accurate tilt servo is possible with an extremely simple configuration.
In addition to being able to eliminate crosstalk, both the CAV and CLV systems have the following various advantages. Since the tilt servo error signal, that is, the light beam for generating the tilt detection signal, does not pass through the objective lens, tilt servo is possible even before focus servo lock-in, and tilt servo can be activated immediately after the disk is attached, thereby reducing the inclination of the disk surface. Each servo can operate stably even if the servo is large. In addition, the tilt servo is not adversely affected by the movement of the objective lens due to tracking, and furthermore, the light emitting and light receiving elements for tilt detection can be attached to the outer peripheral wall of the optical head unit, so that the tilt servo can be mounted inside the unit as in the conventional example shown in Fig. 1. Since it is not necessary to provide the optical head unit, the optical head unit can be made smaller.

In addition, it is equipped with an adjustment mechanism that adjusts the angle of the light emitting element, making it possible to correct the deviation of the optical axis of the emitted light due to the misalignment of the axis between the light source of the light emitting element and the lens, so the tilt of the disk can be accurately adjusted. can be detected.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the outline of a conventional tilt detection device, FIG. 2 is a schematic diagram of an embodiment of the present invention, and FIG.
The figure is a perspective view of the optical head unit shown in Figure 2, and a perspective view of the optical head unit shown in Figure 4.
The figure is a plan view showing the adjustment mechanism in the present invention.
The figures are a sectional view taken along the line A-A in Fig. 1, Fig. 6 is a sectional view taken along the line B-B in Fig. 4, Fig. 7 is a view showing the misalignment of the optical axis of the emitted light, and Figs. 8 to 10. The figure is a diagram for explaining the detection operation of the tilt detection section of the apparatus shown in FIG. 2, and FIGS. 11 and 12 are cross-sectional views showing a part of other embodiments of the present invention. Explanation of symbols of main parts, 11... Disk, 2
3... Light emitting element, 24a, 24b... Light receiving element,
25...Differential amplifier, 27...Tilt motor, 2
9...Objective lens.

Claims (1)

[Claims for Utility Model Registration] (1) A tilting means that detects a deviation in the orthogonal relationship between the optical axis of the optical beam for reading recorded information and the recording surface of the recording disk, and changes the inclination of the optical axis in accordance with this deviation. The optical recorded information reading device has a servo system configured to control the orthogonal relationship to maintain the orthogonal relationship, the base member tilting in the radial direction of the recording disk in conjunction with the tilting means, and the base member tilting in the radial direction of the recording disk in conjunction with the tilting means; a light emitting means for emitting light toward a recording surface; an adjusting and holding mechanism for holding the light emitting means with respect to the base member by making the light emitting axis angle of the light emitting means adjustable; An optical recording information reading device comprising: a light receiving means for receiving light reflected by the recording surface; and a detecting means for detecting a deviation in the orthogonal relationship based on the output of the light receiving means. (2) Registration of a utility model characterized in that the light receiving means includes two light receiving elements arranged symmetrically with respect to the light emitting means on the base member, and the detecting means outputs a difference between outputs of the light receiving elements. An optical recording information reading device according to claim 1.