JPH0739054Y2 - Optical disk drive - Google Patents

Description

[Detailed description of the device] [Industrial applications]

The present invention relates to an optical disk drive device that drives a light spot of an optical head in a radial direction of an optical disk.

[Prior art]

An optical disk is generally provided with a large number of spiral tracks, and information is recorded on these tracks.
Therefore, in order to write and read information, it is necessary to move the light spot of the optical head in the radial direction of the optical disk and position it on the target track. FIG. 4 shows a conventional optical disk drive device. In FIG. 4, 1 is an optical disk, 2 is a spindle motor, 3 is an objective lens, 4 is a light spot, 5 is a lens support, 6 is a wheel, 7 is a wheel guide, 8 is a reflection mirror, 9 is a semiconductor laser, and 10 is a semiconductor laser. Is a collimator lens, 11 is a beam splitter, 12 is a converging lens, 13 is an optical sensor, 13-1 and 13-2 are optical sensor elements, 14 is an optical signal detection circuit, 15 is a tracking control circuit,
16 is a track crossing pulse generation circuit, 17 is a remaining track number counting circuit, 18 is a target relative speed setting means, 19 is a speed error detection circuit, 20 is a compensation circuit, 21 is a track crossing time measurement circuit, and 22 is a relative speed calculation circuit. , 23 is a speed comparator, 24 is an acceleration command means, 25 is an information processing circuit, 26 is a control loop switching circuit, 27 is an amplifying means, 28 is a positioning means, 29 is an external circuit,
30 is a clock terminal. The optical disc 1 is rotated at high speed by a spindle motor 2. The lens support 5 is adapted to move on the wheel guide 7 by the wheels 6, and the movement is performed by the driving force of the positioning means 28. As the positioning means 28, for example, a voice coil motor is used. The signal for driving the positioning means 28 is supplied via the control loop switching circuit 26 and the amplifying means 27. There are the following three types of signals input to the control loop switching circuit 26, and a command for switching them is issued from the information processing circuit 25. A signal supplied from the acceleration command means 24. This is a signal to move the optical disc 1 in the radial direction at full speed (acceleration mode signal). A signal supplied via the system from the track crossing pulse generation circuit 16 to the phase compensation circuit 20. This is not overshooting the target track,
This is a signal for controlling the speed moving in the radial direction while decelerating so as to reach in a short time (deceleration mode signal). A signal supplied from the tracking control circuit 15. This is a signal for controlling the light spot 4 so as not to deviate from the target track after reaching the target track (tracking mode signal). Light is emitted from the semiconductor laser 9. The emitted light passes through a collimator lens 10, a beam splitter 11, a reflection mirror 8 and an objective lens 3, and forms a light spot 4 on the optical disc 1. The light reflected by the optical disk 1 passes through the objective lens 3, the reflection mirror 8, the beam splitter 11 and the converging lens 12, and forms a reflected light spot on the optical sensor 13. The optical sensors 13 are arranged close to each other across the slit.
It is composed of two optical sensor elements 13-1 and 13-2. The optical signal detection circuit 14 detects the difference signal A and the sum signal B of the reflected light amounts entering the optical sensor elements 13-1 and 13-2. The difference signal A represents a track shift signal, and the sum signal B represents an information signal. FIG. 5 is a diagram showing the irradiation state of the optical spot on the optical disc. Reference numeral 1-1 on the surface of the optical disc 1 is a guide groove for guiding the light spot 4 so as not to go out of the track, and 1-2 is a mirror surface between the guide grooves 1-1. P is a track pitch. A thick white arrow indicates the irradiation direction of the light spot 4. FIG. 5 (a) shows the irradiation state when the shape of the portion irradiated with the light spot 4 is symmetrical (left and right).
In the figure (a), the case where the guide groove 1-1 is illuminated and the mirror image is symmetrical is shown, but there is also a case where the mirror surface 1-2 is illuminated and the mirror image is symmetrical. FIG. 5B shows the irradiation state when the left and right are asymmetric. FIG. 6 is a diagram showing a state of irradiation of the optical sensor 13 with reflected light. The optical sensor 13 is composed of optical sensor elements 13-1 and 13-2 arranged across a slit 13-3. The direction of the slit 13-3 is the direction corresponding to the longitudinal direction of the track. Reference numeral 40 denotes a reflected light spot, and this reflected light spot 40 is projected across the optical sensor elements 13-1 and 13-2 so as to be exactly divided in half at the slit 13-3. 40-1 is a reflected light spot projected on the optical sensor element 13-1, and 40-2 is an optical sensor element 13-2.
It is the reflected light spot projected on top. In FIG. 6 (a), the density of the points in the regions of the reflected light spots 40-1 and 40-2 is drawn to be equal, but this shows that the amounts of light projected onto both are the same. This occurs when the shape of the portion irradiated by the light spot 4 is bilaterally symmetrical, as shown in FIG. In FIG. 6B, the density of points in the area of the reflected light spot 40-1 is drawn higher than the density of points in the area of the reflected light spot 40-2. This shows a case where there is a difference in the projected light amount such that the projected light amount of the reflected light spot 40-1 is larger than the projected light amount of the reflected light spot 40-2. This is caused by the light spot 4 as shown in FIG.
This is the case where the shape of the part irradiated by is asymmetric. The amount of reflected light from the mirror surface 1-2 is large, and the amount of projected light of the reflected light spot 40-1 to which it is transmitted is large. However, the amount of reflected light from the guide groove 1-1 is smaller than the amount of reflected light from the mirror surface 1-2 due to diffraction of reflected light by the groove. Therefore, the projected light amount of the reflected light spot 40-2 to which it is transmitted is small. When the difference signal A of the projected light amounts of the reflected light spots 40-1 and 40-2 is obtained by the optical signal detection circuit 14, it becomes zero in the case of FIG. 6 (a) and becomes 0 in the case of FIG. 6 (b). Is non-zero. In the tracking control (tracking control) of the light spot 4 along the track, the irradiation position of the light spot 4 is the guide groove 1-1.
The difference signal A is not deviated when the difference signal A is zero, and is deviated when the difference signal A is not zero. Therefore, the difference signal A is a signal (track deviation signal) indicating the degree of deviation of the light spot 4 from the track. In addition, the optical signal detection circuit 14, the reflected light spot 40-1,40-
Also create a sum signal B of 2. Since the sum signal B represents the total amount of reflected light from the optical disc 1, it reflects the information recorded on the optical disc 1. Therefore, it is an information signal. When the light spot 4 moves in the radial direction of the optical disc 1,
The difference signal A fluctuates positively and negatively at a cycle of the track pitch P while passing a value of zero. The value of the sum signal B never becomes zero, but it also fluctuates in the same cycle. The track crossing pulse generation circuit 16 generates a pulse indicating that the light spot 4 has crossed the track. To generate the difference signal A or the sum signal B, the track pitch P
The property that changes periodically with the period of is used. The difference signal A and the sum signal B are used to distinguish whether the optical disc 1 is traversed from the inside to the outside or from the outside to the inside.
This is done by investigating the phase difference between. For example, in FIG. 5, it can be understood by considering the case where the light spot 4 moves from left to right and the case where the light spot 4 moves from left to right, with the left side being the outside of the optical disc 1 and the right side being the inside. In addition, the interval (phase shift) between the time point when the difference signal A becomes the maximum and the time point when the sum signal B becomes the maximum is the case when traversing from the inner side (right) to the outer side (left) and the outer side (left) → It differs from the case of crossing inward (to the right). This can be used to distinguish the transverse direction. A command to move the light spot 4 to another track is issued from the external circuit 29 to the information processing circuit 25. The information processing circuit 25 issues a command to the control loop switching circuit 26 to cause the acceleration command means 24 to select the acceleration signal G.
The acceleration signal G is transmitted to the positioning means 28 via the amplifying means 27 and moves the light spot 4 toward the target track at full speed. On the other hand, the information processing circuit 25 sets the number of tracks from the track where the light spot 4 was located to the target track in the remaining track number counting circuit 17. Each time a track crossing pulse is input from the track crossing pulse generation circuit 16 to the remaining track number counting circuit 17, the number of tracks set in the remaining track number counting circuit 17 is counted down. The target relative speed setting means 18 is means for setting a target value of the relative speed between the moving speed of the light spot 4 and the moving speed of the track in the radial direction. The moving speed of the track in the radial direction is as follows. Generally, in an optical disk drive, the track rotation locus is not a perfect circle due to factors such as an error in the mounting position of the optical disk 1, an eccentricity of the spindle motor 2 axis, and distortion of the optical disk 1. Therefore, light spot 4
When you fix the position of and look at the track passing directly under it, the track moves inward (toward the center of rotation) or outward and undulates like a sine wave. The speed of moving inward and outward is the above-mentioned "moving speed of the track in the radial direction". The target relative speed is the relative speed that should be the target,
By moving at this speed, it is possible to quickly reach the instructed track without overshooting. FIG. 9 is a diagram showing the relationship between the number of remaining tracks and the relative speed. The horizontal axis represents the number of remaining tracks. In this figure,
At the origin, the number of remaining tracks is N, which decreases as it goes along the horizontal axis, and eventually becomes zero. The vertical axis represents the relative speed between the light spot and the track. Curve C represents the target relative speed. The relative speed should be high while the number of remaining tracks is large, but when the number of remaining tracks is small, the relative speed should gradually decrease to prevent overshoot. Therefore, the curve C
Is a downward-sloping curve (curve E represents the actual relative speed, which will be described later). Target relative speed setting means 18, according to the number of remaining tracks,
The value of the curve C, that is, the target relative speed C is output. Therefore, for example, when the remaining track number is used as an address for access, the memory is configured so that the corresponding target relative speed C can be read. The track crossing time measuring circuit 21 counts the number of clock pulses from the clock terminal 30 that passes from the time when one track crossing pulse is output until the time when the next track crossing pulse is output so that the light spot 4 crosses one track. The track crossing time T required to do so is measured. The relative speed calculation circuit 22 is a circuit that calculates the actual relative speed E. How to obtain it will be described with reference to FIGS. 7 and 8. FIG. 7 is a diagram for explaining a conventional method of calculating relative speed, and FIG. 8 is a partially enlarged view thereof. The horizontal axis of FIG. 7 shows the time, and the vertical axis shows the position from the rotation center of the optical disc 1. The straight line M ₁ indicates the position of the light spot 4. Light spot 4 because it is rising to the right linearly with the passage of time
It can be seen that indicates the case where the object is moved at a constant speed from the inside to the outside. The tracks K and K + 1 are drawn in a wavy shape because, as described above, the track trajectory is not a perfect circle centered on the center of rotation. P is a track pitch. Now, at the time t ₁ , the light spot 4 is at the point Q ₁ . The point Q ₁ is on the inner boundary of the track K + 1 and the distance from the center of rotation is d ₁ . At time t ₂ thereafter, the light spot 4 reaches the point R ₁ on the outer boundary of the track K + 1. Now, the light spot 4 has crossed the track K + 1. Therefore, t ₂ -t ₁ is a track crossing time T ₁ of the at this time. Meanwhile, the inner boundary of the track K + 1 is slightly closer to the rotation center direction at the point S ₁ (the distance from the rotation center is d ₂ ).
Have moved to. FIG. 8 shows an enlarged view of the triangle formed by the points Q ₁ , R ₁ and S ₁ . Note that d = d ₁ −d ₂ . The light spot 4 moves to the point Q ₁ → R ₁ during the time T ₁ , but this movement is a movement outward in the radial direction by P−d. Therefore, the moving speed of the light spot 4 is (P−d) / T ₁
Is. Similarly, the moving speed of the track is d / T ₁ inward in the radial direction. Therefore, the relative velocity E between the two is calculated as follows, considering that the directions of the movements are opposite. If the time t ₃ time between ~t ₄ and T _2, in the same manner, relative rate of P / T _2. When the track crossing time is generally represented by T, the relative speed E is calculated as P / T. When the light spot 4 is moved by the acceleration signal G from the acceleration command means 24, the relative speed E increases. The fact that the curve E in FIG. 9 increases linearly to the right indicates that situation. The speed comparator 23 compares the target relative speed C with the relative speed E and monitors whether E ≧ C. This is the ninth
In the figure, it is to monitor whether the curve E has intersected with the curve C. U represents the intersection. When E ≧ C, the speed comparator 23 informs the signal H
To the information processing circuit 25. Then, the information processing circuit 25
The control loop switching circuit 26 is switched to select the signal from the compensation circuit 20. The signal from the compensation circuit 20 is the following signal. First, the speed error detection circuit 19 detects an error signal F which is an error between the target relative speed C and the relative speed E. The compensation circuit 20 is a circuit generally used to stabilize the operation of the automatic control system, and is, for example, a phase compensation circuit or the like. Therefore, the signal from the compensation circuit 20 is a signal obtained by compensating the error signal F. When the positioning means 28 is driven by the signal from the compensating circuit 20, the light spot 4 is moved by feedback control so that the relative speed E coincides with the target relative speed C. That is, as shown in FIG. 9, the relative speed E is controlled so as to decrease from the intersection point U along the curve C of the target relative speed.
This means approaching the target track while decelerating as prescribed. When the output of the remaining track number counting circuit 17 becomes zero (that is, when the light spot 4 reaches the target track), a signal notifying it is sent to the information processing circuit 25, and the control loop switching circuit 26 causes the tracking control circuit 15 to follow. Is switched to select the signal from. After this time, the control (tracking control) is started to follow so as not to deviate from the target track. The tracking control circuit 15 receives the difference signal A, which is a signal indicating the degree of deviation of the light spot 4 from the track, and outputs a signal for controlling the positioning means 28. The positioning means 28 is controlled so that the difference signal A becomes zero. Note that, as a conventional document relating to the optical disk drive, for example, there is JP-A-62-165734.

(Problem) The above-described conventional optical disk drive device has a problem that speed control cannot be accurately performed and access time becomes long. (Explanation of Problems) In the conventional optical disk drive, the target relative speed C and the relative speed E are updated only when a track crossing pulse is output, and remain the same value during track crossing. When the light spot 4 decelerates toward the target track, it takes a long time to cross the track. During that long time, the control signal obtained based on the value at the time of the previous track crossing pulse is generated. There is no choice but to control the speed as it is. However, the control signal does not reflect the actual situation over time. Therefore, speed control may not be performed accurately, and a track other than the target track may be mistakenly accessed.
In such a case, it is necessary to know the number of error tracks from the address of the track read by the light spot 4 and jump to the target track. If such an operation is performed, it takes a long time to access the target track, and high-speed access cannot be realized. The present invention aims to solve the above problems.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present invention updates the values of the target relative velocity C and the relative velocity E even when the track crossing pulse is not generated, and provides more accurate values to accurately control the velocity of the light spot. The following measures have been taken in order to achieve this. That is, according to the present invention, in an optical disk driving apparatus that searches for a target track by moving the optical spot of the optical head in the radial direction of the rotating optical disk, the optical spot of the optical head and the track of the optical disk are relatively moved when a track crossing pulse is generated. Relative speed calculation circuit for calculating the speed, target relative speed setting means for setting the target relative speed according to the number of remaining tracks when a track crossing pulse is generated, the latest set value of the target relative speed and the preceding value The target relative velocity is corrected by extrapolation based on the calculated at least one or more values, and based on the latest calculated value of the relative velocity and at least one or more values calculated before that. And an error signal between the corrected target relative speed and the corrected relative speed. It was decided to control the movement of the more light spots.

[Action]

The correction means corrects the target relative velocity and the value of the relative velocity obtained each time a track crossing pulse is generated, by an extrapolation method. The corrected value is more suitable for the actual situation. Therefore, when the movement of the light spot is controlled by the error signals of both, the track of the optical disk is accurately accessed, and the access time can be shortened.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an optical disk drive device according to an embodiment of the present invention. The reference numerals correspond to those in FIG. 18-1 is a target relative speed correction circuit, 22-1 is a relative speed correction circuit, and 31 is a speed error detection unit. The difference from the conventional example is that a target relative speed correction circuit 18-1 is inserted after the target relative speed setting means 18,
The point is that the relative speed correction circuit 22-1 is inserted after 22. The target relative speed correction circuit 18-1 is a target relative speed setting means.
This circuit outputs the target relative speed corrected by extrapolation from the target relative speed set most recently in 18 and the target relative speed set before that. FIG. 2 is a diagram for explaining a correction method in the target relative speed correction circuit 18-1. The vertical axis represents the target relative speed C, and the horizontal axis represents the time. t _n-2 , t _n-1 , t _n , and t _{n + 1} indicate the times when the track crossing pulse is generated. C _n-2 , C _n-1 ,
C _n and C _{n + 1} represent the target relative speed C set by the target relative speed setting means 18 at each time. In the conventional example, the target relative speed C calculated at time t _n-2 is
It is used until the next time t _n-1 when the track crossing pulse is generated. When this is shown in FIG. 2, it becomes like the one-dot chain line 50-1. Similarly, the time t _n-1 from the time t _n to the dashed line 50-2, from time t _n to the time point t _{n + 1} becomes as dashed line 50-3. In the present invention, for example, at time t _n , a dotted line connecting the latest target relative speed C _n and the previous target relative speed C _n-1
52-2 is extended as it is to obtain a solid correction straight line 51-3. Then, for example, the value of the correction straight line 51-3 is read in synchronization with the clock pulse that appears at an extremely short cycle compared to the interval of the track crossing pulses (that is, the track crossing time), and the corrected target relative speed is obtained. To do. This value is a value that is in the middle of changing toward the next predicted value of the target relative speed, and therefore, when viewed as a target value to be given, it is a more appropriate value than in the past. Further, since the data is updated at a very short interval of clock pulses regardless of the track crossing time, a new value is given according to the passage of time even if the light spot 4 is decelerated. Now, if the period of the clock pulse is Δt and the number of clock pulses coming from time t _{n -1} to time t _n is N, then
The target relative velocity C _{k at} time t _{k when k} clock pulses come in from t _n is given by the following equation. This is provided to the speed error detection circuit 19. Straight 51-1 and 51-2, between times t _n-2 ~t _n-1, respectively, a correction line determined for between times t _n-1 ~t _n. On the other hand, the relative speed correction circuit 22-1 includes the relative speed calculation circuit 22-1.
Is a circuit for outputting the relative speed corrected by extrapolation from the latest calculated relative speed and the relative speed calculated before. FIG. 3 is a diagram for explaining a correction method in the relative speed correction circuit 22-1. The vertical axis represents the relative speed E. The horizontal axis represents time and corresponds to the horizontal axis in FIG. E _n-2 ,
E _n-1 , E _n , and E _{n + 1} represent the relative speed E calculated by the relative speed calculation circuit 22 at each time. The method of correction is the same as in the case of FIG. 2, so a detailed description is omitted, but the relative speed E _{k at} time t _k is obtained by the following equation. This is provided to the speed error detection circuit 19. The clock pulse can also be used as the clock pulse used for measuring the track crossing time. The target relative velocity C _k and relative velocity E obtained as described above
_{Since k} is a value more suited to the actual situation than before,
When the positioning means 28 is driven and controlled based on these error signals, the target track can be accurately accessed. FIG. 10 shows another example of the speed error detector. The speed error detection unit 31 can be composed of a digital signal processor 32 and a D / A converter 33. The target relative speed C, the relative speed E, and the clock pulse are input to the digital signal processor 32, and correction calculation is performed at high speed. Further, it is possible to perform a calculation corresponding to the phase compensation algorithm performed by the compensation circuit 20 of FIG. 1, but by doing so, the compensation circuit 20 can be omitted. In the embodiment described above, the extrapolation by the straight line is performed in consideration of the most recently set (or calculated) value and the previously set (or calculated) value. It is also possible to perform extrapolation by a curve in consideration of the most recently set (or calculated) value and the two or more values previously set (or calculated). .

[Effect of device]

As described above, according to the present invention, the target relative velocity and the relative velocity are calculated based on the value at the time of the latest track crossing pulse generation and the value at the previous at least one or more track crossing pulse generations. The value corrected by the insertion method is used. Therefore, the speed error signal for controlling the movement of the light spot becomes more accurate than before, and the light spot is not moved to the wrong track. As a result, the number of machines that require a jumping operation is reduced, and the access time can be shortened.

[Brief description of drawings]

FIG. 1 ... Optical disk drive apparatus according to an embodiment of the present invention FIG. 2 ... Diagram for explaining correction method in a target relative speed correction circuit FIG. 3 ... Diagram for explaining correction method in relative speed correction circuit FIG. Conventional optical disk drive device FIG. 5 ... Illumination state of light spot on optical disc FIG. 6 ... Illumination state of reflected light on optical sensor FIG. 7 ... Conventional method for calculating relative velocity Fig. 8 Fig. 8 Partially enlarged view of Fig. 9 Fig. 9 Fig. 10 showing the relationship between the number of remaining tracks and relative speed Fig. 10 Fig. 10 showing another example of the speed error detector Optical disk 1-1, guide groove 1-2
Is a mirror surface, 2 is a spindle motor, 3 is an objective lens, 4 is a light spot, 5 is a lens support, 6 is a wheel, 7 is a wheel guide, 8 is a reflection mirror, 9 is a semiconductor laser, 10 is a collimator lens, 11 is 11 Beam splitter, 12 is a converging lens, 13 is an optical sensor, 13-1 and 13-2 are optical sensor elements, 13-
3 is a slit, 14 is an optical signal detection circuit, 15 is a follow-up control circuit, 16 is a track crossing pulse generation circuit, 17 is a remaining track number counting circuit, 18 is a target relative speed setting means, 18-1 is a target relative speed correction circuit. , 19 is a speed error detection circuit, 20 is a compensation circuit, 21 is a track crossing time measurement circuit, 22 is a relative speed calculation circuit, 22-1 is a relative speed correction circuit, 23 is a speed comparator,
24 is an acceleration command means, 25 is an information processing circuit, 26 is a control loop switching circuit, 27 is an amplifying means, 28 is a positioning means, 29 is an external circuit, 30 is a clock terminal, 31 is a speed error detecting section, and 40 is reflected light. Spots 40-1 and 40-2 are reflected light spots.

Claims (1)

[Scope of utility model registration request] 1. An optical disk drive for moving a light spot of an optical head in a radial direction of a rotating optical disk to search for a target track, and a relative speed between the light spot of the optical head and a track of the optical disk when a track crossing pulse is generated. A relative speed calculation circuit for calculating the relative speed, target relative speed setting means for setting the target relative speed in accordance with the number of remaining tracks when a track crossing pulse is generated, the latest set value of the target relative speed and the value set before it. The target relative speed is corrected by extrapolation based on at least one or more values and based on the latest calculated value of the relative speed and at least one or more values calculated before that. At least a correction means for correcting the relative speed by the extrapolation method is provided, and the error signal between the corrected target relative speed and the corrected relative speed is used. Optical disk drive, characterized by movement control spots.