JP2522973B2 - Target signal search device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention performs rough search by moving the entire optical pickup device at high speed in the tracking direction of a signal recording medium, and tracks movable optical parts of the optical pickup device. The present invention relates to a target signal search device that searches for a target signal track by performing a fine search by displacing it in the direction, and particularly to a target signal search device that suppresses vibration when searching for the signal track of the movable optical component.

(B) Conventional Technology An optical reproducing device for optically reproducing a signal recorded on a signal recording medium using an optical pickup device, such as a CD player or a laser vision player, is known. As is well known, the optical reproducing apparatus records a sub data signal of position index information indicating the position of the disc in addition to a main data signal such as music information and video information. Specifically, in the case of a CD, index information called TOC (in the case of a music CD, the start position of each song, total number of songs, total playing time, etc.) is recorded in the lead-in area, and 1 / A sub-data signal called a sub-coding signal, which completes one block in a cycle of 75 seconds, is recorded, and the sub-coding signal is composed of 8 channels P to W,
In a music CD, position index information indicating the beginning of the song on the P channel, position index information indicating the absolute elapsed time from the start of the signal track, the elapsed time of each song, the song number, and the index on the Q channel. Is recorded. For that reason,
The optical reproducing device is usually equipped with a target signal searching device so that a data signal such as a head of a target music piece designated by a manual operation can be searched by using the position index information. In the case of a CD-ROM, since the position index information is included in the main data signal, the position index information can also be used in the search in the CD-ROM drive device to make the search more accurate.

By the way, the target signal search device of the optical reproducing device is provided with a moving distance detecting means for detecting the moving distance of the optical pickup device, and the current position of the optical pickup device is determined based on the distance signal obtained by the moving distance detecting means. The target data corresponding to the position of the target signal track to be searched is created based on the position index information recorded on the CD, and the difference between the position data and the target data is calculated. There is a method in which a distance is obtained from the difference, and the optical pickup device is moved according to the distance to make a rough search by relying on the distance signal from the moving distance detecting means. Here, as is well known, the optical reproducing device controls the light beam generated from the optical pickup device in the optical axis direction, that is, the so-called focusing direction in order to accurately focus the light beam on the signal surface on the disc. In order to follow the signal track on the signal surface, tracking control is performed to control the light beam in the radial direction of the disc, the so-called tracking direction. Focusing control and tracking control are usually performed by displacing the objective lens. Therefore, the objective lens is displaceably supported. Therefore, the target signal search device performs a fine search by displacing the objective lens after the reproduction position of the optical pickup device approaches the target signal track by rough search, and moves the reproduction position onto the target signal track. I am letting you.

As described above, the target signal retrieving apparatus equipped with the moving distance detecting means sets the irradiation point (reproduction position) of the light beam generated from the optical pickup apparatus to the target signal track by high-speed feeding of the optical pickup apparatus once. Since they can be brought close to each other, it is advantageous to speed up the search operation. here,
The moving distance detecting means of the target signal searching device includes a method of detecting the moving distance by counting a track cross signal generated when a light beam from the optical pickup device crosses a signal track, and a moving distance of the optical pickup device. There is a method that uses an encoder or potentiometer that generates an output in accordance with the above, and uses the output from the encoder or potentiometer to detect the travel distance.The former method uses a detection circuit if the frequency of the track cross signal becomes too high. Therefore, the moving speed of the optical pickup device cannot be increased so much because the counting cannot be performed. Therefore, in order to reduce the search time,
The latter method is preferred.

By the way, the target signal search device performs a search operation,
When the optical pickup device is displaced in the tracking direction, the movable optical component for tracking control vibrates due to its acceleration or inertia when the optical pickup device is stopped. Causes a time required for pulling in the tracking control performed thereafter, and causes inaccuracy in the search position of the target track. In particular, since the number of optical pickup devices that use a linear motor to displace the optical pickup device at a high speed in order to shorten the search time is increasing, the vibration of the movable optical component becomes more problematic.

(C) Problems to be Solved by the Invention In order to solve the above problems, for example, Japanese Patent Laid-Open No. 59-1652.
As disclosed in Japanese Patent No. 78, attention is paid to the fact that the drive current supplied to the linear motor for driving the optical pickup device is substantially proportional to the acceleration of the optical pickup device, and it is proportional to the drive current supplied to the linear motor. 2. Description of the Related Art There is a known target signal search device configured to supply a signal to a movable optical component (objective lens) for tracking control.

However, in reality, the drive current of the linear motor is not necessarily proportional to the acceleration of the optical pickup device due to factors such as friction of the drive mechanism of the optical pickup device or external force such as inclination of the drive mechanism. Therefore, in the end,
The vibration of the movable optical component for tracking control could not be suppressed sufficiently.

(D) Means for Solving the Problems The present invention has been made in view of the above points, and supplies a linear motor for driving the optical pickup device in the tracking direction, and a drive current to the linear motor. A linear motor drive circuit, a tracking coil drive circuit for supplying a drive current to a tracking coil for driving a movable optical component of the optical pickup device in a tracking direction, and a linear motor signal corresponding to the drive current for driving the linear motor are provided. A first signal generating circuit for generating the moving distance, moving distance detecting means for detecting a moving distance of the optical pickup device,
A second signal generating circuit for converting a distance signal obtained by the moving distance detecting means into an acceleration signal according to the moving acceleration of the optical pickup device, a linear motor signal from the first signal generating circuit, and the second signal. And a switch circuit which selectively supplies the acceleration signal from the signal generating circuit of 1 to the tracking coil drive circuit,
A linear motor signal is supplied to the tracking coil drive circuit for a predetermined period when the optical pickup device starts moving, and then the switch circuit is switched so as to supply an acceleration signal.

(E) Operation The present invention is an optical pickup at the time of search due to structural problems such as rattling of a drive mechanism for driving the optical pickup device or resolution of the moving distance detecting means in the low speed range of movement of the optical pickup device. The linear motor signal generated from the first signal generation circuit is generated for a predetermined period at the start of movement of the apparatus, and the acceleration signal generated from the second signal generation circuit is generated after the movement of the optical pickup apparatus is stabilized. Paying attention to the fact that it approximates the actual acceleration of the optical pickup device, the linear motor signal is supplied to the tracking coil drive circuit for a predetermined period at the start of movement of the optical pickup device at the time of search, and then the acceleration signal It is designed to be supplied.

(F) Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention. (1) is a semiconductor laser (2) as a light source and a half for splitting an optical path and generating astigmatism. Mirror (3)
And an objective lens (5) supported so as to be displaceable in the tracking direction and the focusing direction of the signal recording medium (4).
And a photodetector (6) having a detection element for detecting the tracking deviation of the light beam to the signal track, and an optical pickup device (7) supported so as to be displaceable in the tracking direction of the signal recording medium (4). ) Is a tracking error detection circuit which indicates a tracking error of the light beam of the optical pickup device (1) to the signal track by using the output signal from the photodetector (6), and (8) is the tracking error detection circuit (7). A phase compensation circuit for compensating the output signal from the optical pickup device (1) in accordance with the driving system of the objective lens (5) in the tracking direction, and (9) for driving the objective lens (5) in the tracking direction. Tracking coil (10)
A tracking coil drive circuit that supplies a drive current to
(11) is a linear motor for driving the optical pickup device (1) in the tracking direction, ( 12 ) is fixed to the optical pickup device (1), and is displaced according to the movement of the optical pickup device (1). the main and scale (13), the main scale (13) detecting section (14) from the composed linear encoder movement detecting the to, (15) the linear encoder (1
2 ) The encoded output signal from 2 ) is decoded and converted into a pulse signal whose waveform has been shaped and multiplied, and the output signal supplied from the linear encoder ( 12 ) causes the optical pickup device (1) to travel in the traveling direction. Decoders that output pulse signals from the positive output terminals (16a) and (17a) or the negative output terminals (16b) and (17b) according to the recording, and (18) is recorded on the signal recording medium (4) currently being reproduced. A position data generating circuit which supplies the position index information being supplied from the input terminal (19) and creates position data according to the current position of the optical pickup device (1) based on the position index information,
Reference numeral (20) is target data for setting index information according to a search target specified by the input means (22) from the RAM (21) storing index information reproduced when the signal recording medium (4) is attached. A setting circuit (23) detects a difference between the position data created by the position data creation circuit (18) and the target data set by the target data setting circuit (20), and the optical pickup is based on the difference. A target position calculation circuit for calculating the distance from the current position of the device (1) to the target position which is the position of the target signal track, and (24) counts according to the numerical value calculated by the target position calculation circuit (23). The value is set, and the counter is counted down according to the pulse signal output from the positive output end (16a) of the decoder (15), and the negative output end (16b) of the decoder (15).
A counter (25) which counts up in response to a pulse signal output from the counter, (25) generates a speed reference signal serving as a reference for the speed at which the optical pickup device (1) is moved according to the count value of the counter (24). A speed reference signal generating circuit (26) is composed of an FV converter for converting a frequency signal into a voltage signal, and is supplied from the positive and negative output terminals (17a) and (17b) of the decoder (15) per unit time. Optical pickup device (1) based on the number of pulse signals output to
A speed signal generating circuit for generating a speed signal whose voltage value changes according to the moving speed of the
A differentiation circuit that differentiates the speed signal from 6) into an acceleration signal corresponding to the acceleration of the optical pickup device (1), and (28) is a speed reference signal output from the speed reference signal generation circuit (25). A subtraction circuit for subtracting the speed signal output from the speed signal generation circuit (26), and (29) phase compensation of the output signal from the subtraction circuit (28) according to the drive system of the optical pickup device (1). Phase compensation circuit,
(30) is a linear motor drive circuit that supplies a drive current to the linear motor (11) according to the output signal from the phase compensation circuit (29), and (31) is a drive current that is supplied to the linear motor (11). Resistor for generating voltage according to (32)
Is a linear motor signal generation circuit that generates a linear motor signal according to the drive current supplied to the linear motor (11) from the potential difference across the resistor (31), and (33) is the linear motor signal generation circuit (32 ), A linear motor signal from the differential circuit (27) and an acceleration signal from the differentiation circuit (27) are selectively supplied to the next stage, and (34) is a signal from the first switch circuit (33) and phase compensation. A second switch circuit for selectively supplying a signal from the circuit (8) to the tracking coil drive circuit (9), and (35) controlling switching of the first and second switch circuits (33) and (34). Switch switching circuit. Here, the position data creation circuit (1
8), the target data setting circuit (20), the RAM (21), the target position calculating circuit (23), the speed reference signal generating circuit (25) and the switch switching circuit (35) are constituted by a microcomputer, and the switch switching circuit (35) is a first predetermined value determined by the counter (24) from the time when it is detected that the optical pickup device (1) needs to be moved according to the distance to the target position calculated by the target position calculation circuit (23). The first switch circuit (33) is switched to the side a until a few counts (for example, two counts) are performed, and then to the side b, and the counter (24 The second switching circuit (34) is switched to the b side until the count value of (1) becomes "0", and at other times, a switching signal for switching to the a side is generated.

Further, the linear encoder ( 12 ) and the decoder (15) serve as moving distance detecting means for detecting the moving distance of the optical pickup device (1), and an optical type is used as the linear encoder ( 12 ), As shown in FIG. 2, the main scale (13) is formed with a plurality of slits (36) arranged at equal intervals, and the detection section (14) is arranged so as to face the main scale (13). A light emitting element (37) and light receiving elements (38) and (39) are provided. In front of the light receiving elements (38) and (39), the auxiliary scale (40) has the same pitch as the slits (36) of the main scale (13) and the positions of the slits are different from each other by 1/4 pitch. And (41) are provided. Therefore, the optical pickup device (1) is moved and the main scale (13) is moved.
Is displaced, the amount of light detected by the light receiving elements (38) and (39) changes, and output signals having different phases of 90 ° can be taken out from the light receiving elements (38) and (39).

In the apparatus configured as described above, when searching for a predetermined data signal, the inputting means (22) performs a search operation according to the target data signal. Then, in the target data setting circuit (20), the signal recording medium (4) previously stored in the RAM (21) in accordance with the operation of the input means (22).
The target data of the index information corresponding to the search target is set from the index information of. Meanwhile, position data creation circuit (18)
The position data corresponding to the current position of the optical pickup device (1) is created on the basis of the position index information currently being reproduced, which is supplied from the input terminal (19). Therefore, the target position calculation circuit (23) calculates the distance from the current position of the optical pickup device (1) to the target position, and the count value of the counter (24) is set according to the calculated numerical value. Therefore, the speed reference signal generating circuit (25) generates a speed reference signal according to the count value. Since the speed reference signal generated from the speed reference signal generation circuit (25) is supplied to the linear motor drive circuit (30) via the subtraction circuit (28) and the phase compensation circuit (29), the linear motor drive circuit is driven. A drive current corresponding to the speed reference signal is generated from the circuit (30). Therefore, the linear motor (11) is driven according to the speed reference signal, and the optical pickup device (1) is moved accordingly. The counter (24)
A positive or negative numerical value is set for the count value set in the direction of the target position with respect to the current position, and the speed reference signal generation circuit (25) is set according to the positive or negative of the count value.
Generates speed reference signals of different polarities.

When the optical pickup device (1) moves, the main scale of the linear encoder (12) (13) moves, the output signal is generated from the detection unit of the linear encoder (12) (14) in accordance with the movement. The output signal generated from the detection section (14) is decoded by the decoder (15). Here, from the detection section (14), two light receiving elements (38)
And (39) output signals are output, and the output signals generated by the light receiving elements (38) and (39) have different phases by 90 °, so that the decoder (15) leads the phase. By detecting the output signal, the moving direction of the optical pickup device (1) is determined, and when the reproducing position by the optical pickup device (1) is moving in the advancing direction,
When pulse signals are generated from the positive output terminals (16a) and (17a) and the reproduction position by the optical pickup device (1) is moving in the returning direction, negative output terminals (16b) and (1)
A pulse signal is generated from 7b). The positive and negative output terminals (16a) and (16b) connected to the counter (24) generate one pulse per pitch of the main scale (13). ) Connected to the positive and negative output terminals (17a) and (17b), by combining the output signals generated from the two light receiving elements (38) and (39), one pitch of the main scale (13). The resolution is increased so that 4 pulses are generated per hit.

Depending on the movement of the optical pickup device (1), the positive or negative output terminal (16a) or (16b) of the decoder (15)
When the pulse signal is output from the counter, the count value of the counter (24) is counted down or counted up by one count and approaches "0". The speed reference signal generated from the speed reference signal generating circuit (25) sequentially changes according to the count value, and the moving speed of the optical pickup device (1) slows as the count value approaches "0" from a predetermined value. To change. Then, when the optical pickup device (1) eventually reaches the target position, the count value becomes "0", and the generation of the speed reference signal from the speed reference signal generation circuit (25) is stopped. Therefore, the movement of the optical pickup device (1) is stopped. At this time, since the reproduction position of the optical pickup device (1) is displaced within a range in which the reproduction position can be moved to the target signal track by the track jump by the objective lens (5), the objective lens (5) is driven thereafter. Thus, the target signal track is searched.

On the other hand, depending on the movement of the optical pickup device (1), the positive or negative output terminal (17a) or (1
When a pulse signal is output from 7b), the speed signal generation circuit (2
A speed signal corresponding to the moving speed of the optical pickup device (1) is generated from 6). Since this speed signal is input to the inverting input terminal of the subtraction circuit (28) in phase with the speed reference signal generated from the speed reference signal generation circuit (25), the moving speed of the optical pickup device (1) is negative. It functions as a feedback signal and is used to control the optical pickup device (1) so as to move accurately at a speed according to the speed reference signal.

By the way, the optical pickup device at the time of searching (1)
When is moved by the linear motor (11), the second switch circuit (34) is switched to the b side by the switching signal from the switch switching circuit (35), and the output signal from the first switch circuit (33) is tracked. It is configured to be supplied to the coil drive circuit (9). The first switch circuit (3
3) is switched to the a side by the switch switching circuit (35) until the first predetermined number is counted by the counter (24), and after the number is counted by the counter (24), it is b side. Therefore, the tracking coil drive circuit (9) receives the linear motor signal generated from the linear motor signal generation circuit (32) for a predetermined period when the movement of the optical pickup device (1) is started at the time of search. Is supplied, and after the lapse of the predetermined period, the differentiation circuit (2
The acceleration signal generated from 7) is supplied. here,
When the moving period of the optical pickup device (1) is shown as shown in FIG. 3 (a) and the actual moving speed of the optical pickup device (1) is shown in FIG. 3 (b), the optical pickup device (1) is shown. The actual acceleration of is as shown in FIG. On the other hand, the linear motor signal generation circuit (32) outputs a linear motor signal according to the drive current supplied to the linear motor (11) from the potential difference across the resistor (31). It becomes as shown in Fig. 3 (d).
On the other hand, since the speed signal generating circuit (26) generates a speed signal as shown in FIG. 3 (e), the differentiating circuit (27) for differentiating this speed signal gives the acceleration as shown in FIG. 3 (f). A signal is generated. Here, the speed signal generating circuit (2
The velocity signal generated from 6) is caused by a structure such as rattling due to a difference between a fulcrum of the driving mechanism (not shown) of the optical pickup device (1) and a working point, or a slit () of the main scale (13). Due to the poor resolution in the low speed range due to the influence of the pitch interval (36) (leakage of minute displacement due to resolution) in the low speed region, an error between the optical pickup device (1) and the actual speed becomes noticeable. Therefore, as a matter of course, the optical pickup device (1)
A large error occurs between the acceleration signal generated from the differentiating circuit (27) and the actual acceleration at the start of the movement.

However, when the moving speed of the optical pickup device (1) is increased, the influence on the structure of the drive mechanism of the optical pickup device (1) or the pitch interval of the slits (36) of the main scale (13) becomes larger. The influence can now be ignored, and the decoder (15) to the linear encoder ( 12 )
Since a signal corresponding to the actual moving speed of the optical pickup device (1) obtained from the above is generated, the speed signal generated from the speed signal generating circuit (26) is substantially equal to the actual speed. Further, when the movement of the optical pickup device (1) is stopped, the structure of the drive mechanism of the optical pickup device (1) is affected by the pitch interval of the slits (36) of the main scale (13), but the movement is started. Since it is not easily affected by the above, the error between the acceleration signal generated from the differentiating circuit (27) and the actual acceleration is not as large as at the start of movement.

As a result, comparing the linear motor signal from the linear motor signal generating circuit (32) and the acceleration signal from the differentiating circuit (27) with the actual acceleration, the optical pickup device (1)
When the movement of the optical pickup device (1) is stable, the acceleration signal becomes substantially equal to the actual acceleration at the start of the movement.

Therefore, the first switch circuit (33) should be set in FIG.
As shown in FIG. 5, the tracking coil driving circuit (9) is set to the actual acceleration of the optical pickup device (1) by switching to the a side for a predetermined period at the start of movement of the optical pickup device (1) and then to the b side. Equal signals will be provided. Therefore, when the optical pickup device (1) is moved, the objective lens (5) is controlled by a signal substantially equal to the actual acceleration of the optical pickup device (1) as shown in FIG. Is suppressed. The horizontal axis in FIGS. 3 (a) to 3 (h) represents time (t), and FIG. 3 (b), (c), (d),
In (e), (f) and (h), the vertical axis represents the voltage.

When the movement of the optical pickup device (1) is completed, the second switch circuit (34) is immediately switched to the side a by the switch switching circuit (35). Therefore, this time, a tracking error signal corresponding to the tracking error from the tracking error detection circuit (7) via the phase compensation circuit (8) is supplied to the tracking coil drive circuit (9), so that the tracking control is immediately performed. The retraction operation is performed,
After that, a track jump for displacing the objective lens (5) is performed by a control means (not shown), and a search for a target signal track is achieved.

In the embodiment described above, the acceleration signal from the differentiating circuit (27) greatly changes the actual acceleration from the actual acceleration, and the first switch circuit (33) is set to the a side for a predetermined period at the start of movement of the optical pickup device (1). Although the switching is performed, the degree is better than when the movement of the optical pickup device (1) is started,
The first switch circuit also has a predetermined period until the movement of the optical pickup device (1) is stopped, although the acceleration signal from the differentiating circuit (27) is less affected by the vibration of the objective lens (5) and is different from the actual acceleration. Further effects can be expected if (33) is switched to the side a.

In the embodiment, the target data setting circuit (20)
The index information is stored in advance in the RAM (21) in order to set the target data according to the index target by the CD-ROM.
When the index information has a large capacity as described above, the index information cannot be stored in the RAM provided in the microcomputer. Therefore, the index information should be stored in the host computer connected to the CD-ROM drive. Alternatively, the index information of the CD-ROM may be read and the target data may be set by the target data setting circuit (20) each time the search is performed.

(G) Effect of the Invention As described above, the target signal search device according to the present invention is
A linear motor signal generated from the first signal generating circuit is supplied to the tracking coil drive circuit for a predetermined period when the movement of the optical pickup device is started during search, and thereafter,
Since the acceleration signal generated from the second signal generating circuit is supplied, the vibration of the movable optical component can be suppressed from the start of movement of the optical pickup device to the end of movement thereof.
In particular, the movable optical components are not accurately controlled due to structural problems such as rattling at the start of movement of the optical pickup device, or the problem of resolution of the moving distance detecting means in the low speed range of movement of the optical pickup device. Since it is prevented, the vibration of the movable optical component can be surely suppressed, and the search can be speeded up.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention, and FIG.
The figure is a model diagram showing a linear encoder, and Fig. 3 (a).
(B), (c), (d), (e), (f), (g), and (h) are waveform charts for explaining the present invention. Description of main drawing numbers (1) …… Optical pickup device, (10) …… Tracking coil, (7) …… Tracking coil drive circuit,
(11) …… Linear motor, ( 12 ) …… Linear encoder, (15) …… Decoder, (18) …… Position data creation circuit, (20) …… Target data setting circuit, (23) …… Target position Calculation circuit, (24) ... counter, (25) ... speed reference signal generation circuit, (26) ... speed signal generation circuit, (27) ...
… Differentiation circuit, (28) …… Subtraction circuit, (30) …… Linear motor drive circuit, (32) …… Linear motor signal generation circuit,
(33) …… First switch circuit, (34) …… Second switch circuit, (35) …… Switch switching circuit.

Claims (1)

(57) [Claims] 1. An optical pickup device comprising a movable optical component that is displaceably supported so as to optically reproduce a signal recorded on a signal recording medium and to follow a signal track of the signal recording medium. The target signal search device performs a rough search by moving the optical pickup device at a high speed in the tracking direction of the signal recording medium and a fine search by displacing the movable optical component in the tracking direction at the time of searching for the signal track. A linear motor for driving the optical pickup device in the tracking direction, a linear motor drive circuit for supplying a drive current to the linear motor, and a drive current for a tracking coil for driving the movable optical component in the tracking direction. And a tracking coil drive circuit for supplying the A first signal generating circuit for generating a linear motor signal according to a current, a moving distance detecting means for detecting a moving distance of the optical pickup device, and a distance signal obtained by the moving distance detecting means for the optical pickup device. A second signal generating circuit for converting into an acceleration signal according to the moving acceleration, a linear motor signal from the first signal generating circuit, and an acceleration signal from the second signal generating circuit selectively to the tracking coil. A switch circuit that supplies the drive circuit, and supplies a linear motor signal to the tracking coil drive circuit for a predetermined period at the start of movement of the optical pickup device at the time of search, and thereafter,
A target signal retrieving apparatus, wherein the switch circuit is switched so as to supply an acceleration signal.