JP2609721B2 - Optical recording information reader - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information reading apparatus, which controls an intersection of an optical axis of a light beam emitted from the apparatus and a recording medium (hereinafter referred to as tilt servo or skew servo).
And a focus servo that causes a light beam to be focused on a recording medium.

[Prior Art] Japanese Patent Laid-Open Publication No.
As disclosed in JP-A-59-152530 and JP-A-59-223943, in addition to focus servo, tracking servo, etc., tilt (or unify tilt below skew)
Servo is required. Various examples of the specific structure of the tilt servo have been proposed in addition to the above-mentioned known example. However, the mainstream at present is the deviation of the orthogonal relationship between the optical axis of the recording information reading light beam and the recording surface of the recording disk. As a detecting device for detecting an optical pickup, a system as shown in Japanese Utility Model Application Laid-Open No. Sho 59-168835 is used, and as a device for tilting an optical pickup in accordance with the detection output, a system as shown in Japanese Utility Model Application Laid-Open No. It is a system. This is a system as shown in Japanese Utility Model Application Laid-Open No. 60-155017. In the case of the method shown in Japanese Utility Model Publication No. 60-155017, since the pivot point for changing the tilt angle of the optical pickup is centered on one point of the guide rail, the distance between the entire optical pickup and the recording disk changes. However, there is an advantage that it is not greatly influenced by the warpage of the recording disk. In other words, by applying the tilt servo, the orthogonal relationship between the optical axis of the recording information reading light beam and the recording surface of the recording disk is maintained, and the distance between the entire optical pickup and the recording disk becomes constant to some extent. . Therefore, a DC drive of a focus actuator (hereinafter sometimes simply referred to as an actuator), which is a device for driving an objective lens that focuses a recording information reading light beam on a recording disk surface so as to have a sufficient spot diameter, is possible. The range is small. A typical block diagram of the tilt servo is shown in FIG.

[Problems to be Solved by the Invention] The above prior art does not consider runaway of the tilt servo system and the like, and there is a problem that the recording disk is damaged due to the contact between the optical pickup and the recording disk which occurs at this time. This will be described below.

Depending on the position on the guide rail of the optical pickup, the tilt rotation fulcrum for tilting the optical pickup may be far away from the optical axis of the recording information reading light beam. In this case, the vertical movement range of the entire optical pickup Can be very large. Although this has the advantage as shown in the prior art, the tilt servo system malfunctions due to some cause, and the tilt mechanism moves to the full tilt rotation fulcrum possible range, so that the entire optical pickup and the entire optical pickup are recorded. There is a case where the disk approaches abnormally. The runaway of the tilt servo system occurs when dust or the like is attached to the light receiving element of the tilt detector. The problem in such a case will be described with reference to FIGS. 2, 3, 4, and 5. No.
2, 3, 4, and 5 show the case where the recording disk is not warped, and FIG. 2 shows the case where the tilt servo is operating normally and the optical pickup is near the tilt rotation fulcrum. Fig. 4 shows a side view of a part of the optical reading device when the tilt servo is out of control and the optical pickup is near the tilt rotation fulcrum. It is shown.

In FIGS. 2, 3, 4, and 5, 1 is a disk, 2 is a spindle motor for rotating the disk, 7 is an objective lens, 8 is a light beam, 10 is an optical pickup, and 15 is an optical pickup in the radial direction of the disk. The guide rails 18 for movement are pivot points for rotating the guide rails to change the tilt of the optical pickup.

The focus focal length a for sufficiently reducing the spot diameter of the light beam 8 on the surface of the disk 1 is uniquely determined by the wavelength of the light beam and the objective lens 7. Therefore, FIG.
In FIG. 3, the distance between the surface of the disk 1 and the optical pickup 15 is almost the same and is C. Therefore, the DC operation center position of the actuator (not shown) for driving the objective lens 7 is also constant. Now, let the center of operation of the actuator as shown in FIGS. 2 and 3 be the center of the movable range of the actuator.

The distance C 'between the optical pickup 10 and the surface of the disk 1 in the portion where the light beam 7 passes in FIG. 4 is almost equal to that in FIGS. 2 and 3, and C' ≒ C. Accordingly, the DC operation center of the actuator is also substantially the center of the movable range of the actuator. (A slight change in the angle of incidence θ of the light beam 8 on the surface of the disk 1
Although different from the case of FIGS. 2 and 3, the change in θ is actually very small and is ignored here. The same applies hereinafter. In Fig. 5, the guide rail is driven by tilt servo runaway.
15 rotates around the tilt fulcrum, and the position of the optical pickup is away from the tilt fulcrum, so that the distance d between the optical pickup 10 and the disk 1 surface in the portion where the light beam 8 passes is d <C. It has become. In this case, since the DC operation center of the actuator has a focus focal length between the objective lens 7 and the surface of the disk 1, it is necessary to move Cd downward in this case to perform focus servo. Let e be the distance between the limit of the lower movable range of the actuator and the movable center. When Cd <e, the focus servo follows. However, when Cd> e, the focus focal length a cannot be secured between the objective lens 7 and the disk 1 surface unless the objective lens 7 is lowered below the movable range of the actuator. Accordingly, at this time, even if the focus actuator is lowered to the full movable distance, the focus focal length cannot be obtained, and the focus servo becomes impossible, so that the focus servo is unlocked and the focus servo is turned off. If the focus servo remains off during reading of the recorded information, it becomes impossible to continue reading the information. Therefore, it is necessary to operate the focus servo loop again while the disk 1 is rotating. The focus servo re-pulling operation is usually as follows. After the focus servo loop is turned off, the objective lens 7 is once pulled down to the lower limit of the actuator movable range, and the objective lens 7 is raised toward the disk 1, so that the distance between the objective lens 7 and the disk 1 surface is close to the focus focal length a. The arrival of the focus is detected by some method, the focus servo loop is turned on, the focus servo is operated, and the focus pull-in operation is completed. In this operation, the second, third and fourth
As shown in the drawing, there is no problem when the distance between the objective lens 7 and the disk 1 surface at the time when the focus actuator is at the lowermost movable position is longer than the focal focal length a. However, in the case as shown in FIG. When the focus servo loop is turned off by dividing the focus focal length by the distance between the objective lens 7 and the surface of the disk 1, if the above-described retraction operation of the focus servo is performed, the position of the objective lens 7 is initially set to the surface of the disk 1. , The objective lens 7 continues to move upward without focusing, and the objective lens 7 and the disk 1 come into contact with each other if the disk 1 exists before exceeding the movable range above the actuator, Since the disk 1 is rotating at a high speed, the surface of the disk 1 is concentrically scratched. Further, in a severe case, there is a problem that the objective lens 7 is also damaged. Such a scratch on the surface of the disk 1 has a problem that normal reproduction cannot be performed even when the disk 1 is reproduced by a normal recording information reading apparatus.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a recording information reading apparatus which prevents an objective lens from coming into contact with a disk and damaging the disk even if the tilt servo goes out of control as described above. At the same time, it is to prevent damage to the objective lens.

[Means for Solving the Problems] To achieve the above object, when the focus servo is released, the entire optical pickup is moved by a predetermined amount or more in the direction opposite to the disk, and then the objective lens is moved closer to the disk surface. In this manner, the focus actuator is driven to perform the re-pull-in operation of the focus servo.

[Operation] The optical pickup operates such that the focus servo is displaced and at the same time, the optical pickup is separated from the disk surface by a predetermined amount or more.
After this operation is completed, the focus actuator operates so that the objective lens approaches the disk surface. As a result, even if the disc and the optical pickup abnormally approach each other due to tilt servo runaway and the focus is lost, move the objective lens closer to the disc and try to re-focus the focus servo. Since the distance is secured, a point where the focus comes into focus occurs while the objective lens is approaching, focus servo is applied, the operation of the objective lens approaching the disk surface ends, and thereafter the focus between the objective lens and the disk surface again An interval corresponding to the distance is maintained, so that contact between the objective lens and the disk and damage to the disk are prevented.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the block diagram of FIG.
The operation will be described with reference to the operation waveform diagrams of respective parts in the figure and the operation principle diagram in FIG.

In FIG. 1, 7,101 to 106 and 111,112 denote focus servo systems, 121 to 126 and 131,132 denote tilt servo systems. FIG.
G correspond to the reference numerals in FIG.

In FIG. 1, a focus light receiving element 101 receives reflected light of a recording information reading light beam (not shown) projected on a disk (not shown) through an objective lens, converts the light into an electric signal, and outputs the electric signal. This output is input to the focus error signal creation circuit 102 and the focus lock detection circuit 111. The focus error signal generation circuit 102 is connected to the objective lens 7
And outputs a signal corresponding to the error amount. This output is sent to the phase compensation amplifier 103 and the focus lock detection circuit 111. The phase compensation amplifier 103 amplifies the focus error signal, performs phase compensation to prevent oscillation of the focus servo system, and inputs the output to one end of the switch circuit 104. The focus lock detection circuit 111 receives the outputs of the focus light receiving element 101 and the focus error signal generation circuit 102 and mainly detects the amount of reflected light from the disk surface (actually, it is more complicated, but since there is no direct relationship here, When the distance between the objective lens 7 and the disk surface is close to the focal length (not described in detail), a low level is output A as a focus lock state, and a high level is output as a focus unlock state otherwise. The output A is sent to the objective lens vertical signal generating circuit 112 and the focus-on signal generating circuit 113. The focus-on signal generation circuit 113 initially outputs a high level B as the focus-off state, and outputs a low level B as the focus-on state when the recording information reading apparatus starts up, and the focus servo cannot be performed for some reason. When the focus is lost and the focus servo is released, that is, when the focus lock signal generation circuit 111 outputs the focus unlock state (time t _{1 in} FIG. 6), a high level is output as a focus-off command, and after that, it takes a while. (Time t _{2 in} FIG. 6), a low level is output as a focus-on command. The objective lens up / down signal generation circuit 112 receives the output A of the focus lock signal generation circuit 111 and the output B of the focus-on signal generation circuit 113 as input, and changes the output A of the focus lock signal generation circuit 111 from the focus lock to the focus unlock state. From the moment of the change to the next arrival of the focus-on signal B ON command (see FIG.
actuator between t _{1 and} t ₂ ) to drive the objective lens 7
A signal for moving the objective lens 7 away from the disk surface up to the full movable range of 106 is generated and output. During even for some time after arriving on command of the focus-on signal B, the output of the objective lens up and down signal generating circuit 112 holds the state as to approach gradually from Figure 6 the time t ₃ the objective lens 7 to the disk surface Signal is output.

The output of the switch circuit 104 is switched by the focus lock detection circuit 111 as two inputs of the output of the phase compensation amplifier 103 and the output of the objective lens vertical signal generation circuit 112. When the focus lock state is output from the focus lock detection circuit 111, the output of the switch circuit 104 is selected from the output side of the phase compensation amplifier 103, and when the focus unlock state is output, the objective lens vertical signal generation circuit 112 is output. Output is selected. Therefore, when the focus lock detection circuit 111 outputs the focus lock state, the output of the focus error signal generation circuit 102 is output to the drive circuit 105 via the phase compensation amplifier 103 and the switch circuit 104.
To drive the actuator 106 attached to the objective lens 7 in response to this.
Is moved to a precise focus servo state (the focus servo loop is on).
When the focus lock signal detection circuit 111 outputs the focus unlock state, the objective lens vertical signal generation circuit 112
Is applied to the actuator 106 via the switch circuit 104 and the drive circuit 105. At this time, the objective lens 7 is once separated from the disk surface according to the above-described sequence, and then the actuator 106 is driven so that the objective lens 7 gradually approaches the disk surface, and the distance between the objective lens 7 and the disk surface is focused. When the distance reaches the vicinity, the focus lock detection circuit 111 outputs a focus lock state, the switch 104 is switched to the position compensation circuit 103, and the focus servo is turned on (the focus servo pull-in operation is completed). That is, the focus lock signal A also serves as a focus servo loop on signal. The time t ₀ shows the operation at system startup of the recorded information reading device.

On the other hand, in the tilt servo system, the tilt error detector
121 detects and outputs an error from the orthogonal state of the optical axis of the recording information reading light beam and the disk surface, and this output is input to a phase compensation amplifier 122 where amplification and phase compensation for preventing tilt servo loop oscillation are performed. The signal is input to one of the circuits 123. When the output of the phase compensation amplifier 122 is selected by the switch circuit 123 and applied to the drive circuit 124 to amplify the power and drive the tilt motor 125, the tilt mechanism 126 (as shown in a known example of Japanese Utility Model No. 60-155017) is used. Mechanism)
Operates to change the tilt of the entire optical pickup (not shown) in the radial direction of the disk so as to cancel an error from the orthogonal state of the optical axis of the recorded information reading light beam and the disk surface. And a tilt servo state where the perpendicular state of the disk surface is maintained. The switching of the tilt servo loop on / off is controlled by the output E of the tilt servo loop on signal generation circuit 132. This is because the tilt servo loop on signal circuit 132 outputs the tilt on command D and the output A of the previous focus lock detection circuit 111. Is two inputs. Normally, the tilt-on command D outputs a low level as a tilt-on command during the information reading operation of the recording information reading apparatus system. (When Chirutoofu instructions and high level.) This was Chirutoon signal generation timing startup Figure 6 time t ₀ system. The tilt servo loop on signal generation circuit 132 receives the two signals, outputs the tilt on command, outputs the tilt on command, and outputs the focus lock state when the focus lock detection circuit 111 outputs the focus lock state. (Low level). Next, when the focus servo becomes impossible for some reason and the focus unlock state is output from the focus lock detection circuit 111, a high level is output as the tilt servo off state from the tilt servo loop on signal creation circuit 132 and the switch circuit is output. The output of 123 is switched from the output of the position compensation circuit 122 to the output G of the tilt movement pulse generation circuit 131. As inputs the output A of the focus lock detecting circuit 111 to the tilt movement pulse forming circuit 131, a predetermined time in synchronization with when the output A changes from the focus lock state to the focus unlocked state (Figure 6 time t ₁₎ The pulse output G is output.
Here was the end of the pulse time and t _2. The pulse output G is supplied to the pulse generation period switch circuit 123 and the drive circuit 12
The tilt motor 125 is driven via 4 to move the tilt mechanism 126 in a direction in which the optical pickup moves away from the disk surface.

Further, the output A of the focus lock detection circuit 111 is
The optical pickup is also sent to the optical pickup feed servo system for moving the optical pickup in the radial direction of the disk, and once the output A of the focus lock detection circuit 111 is in the focus unlocked state, the movement of the optical pickup is temporarily stopped.

The reason why disk damage due to tilt servo runaway or the like can be prevented by the configuration shown in FIG. 1 will be described with reference to the operation principle diagram of FIG.

The optical pickup 10 and the guide rails 15 indicated by broken lines in FIG. 7 (1) operate too close to the optical pickup 10 due to tilt servo runaway on the disk 1 surface, and the movable side of the focus actuator is fully opposite to the disk 1 surface. Then, the light beam is focused on one surface of the disk. This shows a state where focus servo is being performed. That is, the sixth
Think that just before the state shown in FIG time t _1. FIG. 6 the next moment time t ₁
In this case, even if the optical pickup moves on the guide rail 15 toward the outer periphery of the disk, and the optical pickup 10 further approaches the disk 1 surface and finally swings to the full movable range of the actuator, the objective lens 7 and the disk 1 surface have a focal length. a cannot be taken (the distance between the two at this time is a '). Focus servo becomes impossible, and the focus lock signal A outputs a focus unlocked state. The tilt servo loop is turned off in synchronism with the state change of the focus lock signal A, and at the same time, a tilt movement pulse G is generated, the tilt mechanism operates, and the guide rail 15 rotates about the tilt rotation fulcrum, and the optical pickup The whole moves in a direction away from the disk 1 surface, and moves d 'by the end of the tilt movement pulse G. At the same time that the focus lock signal A outputs the focus unlock state,
The focus servo loop is turned off, and the focus actuator is operated by the vertical signal of the objective lens so that the objective lens moves to the full movable range on the side opposite to the disk 1 surface. Next, after the ON command of the focus-on signal B arrives,
Actuator to Figure 6 the time t ₃ holds this state (see FIG. 7 (2)). In the state where the focus lock signal outputs the focus unlock state A, the movement of the optical pickup on the guide rail is also temporarily inhibited, so that the distance between the objective lens 7 and the disk 1 surface is a '+ d' where a ' Is a value as close as possible to the focal length a.

d 'is the moving distance of the optical pickup by the tilt movement pulse G.

It should be.

Then, d '>a-a' is satisfied and the optical pickup
10 Tilt motor 12 in the direction away from disc 1
If 5 sets the tilt movement pulse G as operating distance always objective lens 7 and the disk 1 surface while the objective lens 7 approaches the first surface disc from Figure 6 the time t ₃ is the focal length a A certain point appears and the focus servo loop can be turned on. When the focus servo loop is turned on, the operation of bringing the objective lens 7 closer to the disk ends, and a distance close to the focal length a is always maintained between the surface of the disk 1 and the objective lens 7 by the focus servo operation.

In this manner, the configuration shown in FIG. 1 prevents contact between the objective lens and the disk surface due to tilt servo runaway, etc.
This has the effect of preventing the objective lens from damaging the disk surface.

Note that the tilt movement pulse G is at time t _{3 in} FIG. 6 after the focus is unlocked and before the operation of bringing the objective lens 7 close to the disk during the focus servo re-pulling operation starts.
Before the above, the pulse peak value, the pulse width, etc. may be determined so that the movement of the optical pickup is completed so as to satisfy the condition d '. Here, only the DC operation center of the actuator has been described for simplicity of description, but it goes without saying that the amount of d 'is set in consideration of the operation of the AC component of the actuator for following the disk surface deflection component.
Although the tilt servo is turned off at the time of the focus servo pull-in operation at the time of starting the system of the recording information reading apparatus, the tilt servo may be turned on at this time if necessary. At this time, as a sequence at the time of system startup, the spindle motor 2
You will need to have the disk spin-up due to.

Here, the method of tilting the optical pickup with one point on the guide rail for moving the optical pickup in the radial direction of the disc as shown in FIG. Needless to say, the present invention is also effective in a system in which only the optical pickup is tilted, and in a system in which the rotation fulcrum for adjusting the light beam position and the tilt angle of the optical pickup is displaced in the disk radial direction.

[Effects of the Invention] According to the present invention, even if the optical pickup abnormally approaches the disk due to tilt servo runaway or the like, contact between the objective lens and the disk at the time of refocusing of the focus servo after defocusing can be prevented. There is an effect that disc scratching can be prevented.

In addition, since the contact between the objective lens and the disk can be prevented, there is an effect that damage to the objective lens due to the disk contact of the objective lens can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIGS.
The figure is a side view showing the positional relationship between the disk and the recorded information reading device during normal operation of the tilt servo, and the portions related to the present invention.
4 and 5 are side views showing the positional relationship between the disk and the portion related to the present invention of the recorded information reading device during the tilt servo runaway,
FIG. 6 is an operation waveform diagram corresponding to each part in FIG. 1, and FIG. 7 is an explanatory diagram of an operation principle by the configuration of FIG. DESCRIPTION OF SYMBOLS 1 ... Disc, 2 ... Spindle motor, 7 ... Objective lens, 8 ... Light beam, 10 ... Optical pickup, 15 ... Guide rail, 18 ... Rotating fulcrum, 111 ... Focus Lock detection circuit, 112: Objective lens vertical signal generation circuit, 113: Focus-on signal generation circuit, 131: Tilt movement pulse generation circuit

Claims (1)

(57) [Claims] An optical recording information reading apparatus for reproducing information by irradiating a recording medium surface with a light beam through an objective lens, wherein a deviation amount of the light beam from a direction perpendicular to a recording surface of the recording medium is detected. A tilt control unit that forms an output signal corresponding to the tilt control unit, and a tilt mechanism that has a rotation fulcrum and moves the pickup in a direction that eliminates the displacement of the light beam according to the output signal of the tilt control unit. A tilt servo unit configured to detect a focus shift of the light beam and drive the objective lens to a substantially focus position by a focus actuator based on a focus control signal; and at least the pickup includes the tilt servo unit and the recording medium. In the direction in which the objective lens does not have a focal length with respect to the recording medium. Means for generating a tilt movement signal when the focus servo is disengaged, driving the tilt mechanism based on the movement signal, and retracting the entire pickup by a predetermined distance beyond the focus position in a direction away from the recording medium; An optical recording information reading device, characterized in that the objective lens is driven to a substantially focus position by the focus servo means at the retracted movement position.