HEAD POSITIONING DEVICE FOR OPTICAL DISK DRIVE

Abstract: An optical disk drive device positions a carriage carrying an optical head for directing a light beam towards an optical disk having tracks for information storage and for receiving a reflected beam from said optical disk. The optical disk device includes a retract means (30) comprising a signal instruction circuit (14) for providing the number of tracks to be traversed, an access start instruction and a retract instruction and a reference voltage generating circuit (15) responsive to these instructions to provide the residual track number and a carriage moving signal and operating such that, immediately before the drive device is stopped from operating the carriage mounting the optical head thereon is moved by the access operation from any track to a first predetermined position according to the access start instruction and then moved from the first predetermined position to a second predetermined position according to the retract instruction at a predetermined reference speed.

Description: BACKGROUND OF THE INVENTION The present invention relates to an optical disk driving device for recording or reproducing information on an optical disk by means of an optical system while rotating the optical disk and, particularly, to such device capable of storing the optical disk in a predetermined position reliably immediately before the device is stopped to operate. Fig. 4 is a block circuit diagram of a conventional magnetic disk drive device such as shown in pages 1426 to 1432, Mitsubishi Denki Giho, vol.46, No. 12, December, 1972. In Fig. 4, A reference numeral 40 depicts a linear motor coil for moving a magnetic head ( not shown ) to an aimed track of a magnetic disk ( not shown ) as an information recording medium and 41 is a speed sensor for magnetically detecting a moving speed of a linear motor ( not shown ) driven by the linear motor coil 40. A linear motor control circuit 42 for speed control of the linear motor on the basis of a reference speed preset and an output of the speed sensor 41 provides an output to be applied to the linear motor coil 40. A reference numeral 43 is a switch circuit having a selection terminal A connected to a junction between the linear motor control circuit 42 and the linear motor coil 40, 44 a power source circuit connected to a selection terminal B of the switch circuit 43 and 45 a capacitor connected to a common terminal C of the switch circuit 43. In operation, when the power source circuit 44 is connected in circuit, the common terminal C is connected to the selection terminal B and therefore the capacitor 45 is charged thereby. At this time, a normal access operation is performed by driving the magnetic head facing to the magnetic disk. First, the speed sensor 41 detects a moving speed of the linear motor and inputs the detected speed to the linear motor control circuit 42. The latter supplies a signal indicative of a difference between the preset reference speed and the detected speed to the linear motor coil 40 so that the detected speed is controlled on the basis of the reference speed. Thus, the linear motor coil 40 drives the linear motor at the preset reference speed and positions the magnetic head at the aimed track of the magnetic disk. When the power source circuit is disconnected from the magnetic disk device, a carriage mounting the magnetic head thereon is returned from a track of the magnetic disc to a track "00" thereof and moved to a predetermined position for storage therein. This function is generally called as "retract function". Under an abnormal situation such as power source malfunction or malfunction of commercial power line, the common terminal C in the switch circuit 43 is connected to the selection terminal A to supply energy stored in the capacitor 45 to the linear motor coil 40 so that the linear motor is allowed to achieve the retract function so that any damage due to contact between the magnetic disk and the magnetic head is prevented. A similar retract function is also given to a conventional optical disk drive device. Fig. 5 is a side view of an access mechanism of a conventional optical disk drive device. In Fig. 5, an optical disk 1 as an information recording medium is adapted to rotate around a rotary shaft 1a and has a spiral track or coaxial tracks thereon with a predetermined constant gap therebetween. An optical head 2 is adapted to direct optical beam to a recording surface of the optical disk 1 and receive a reflection for recording and reproducing information with respect to the optical disk 1. A reference numeral 3 depicts a carriage for mounting the optical head 2 and moving it to an aimed address and 4 a linear actuator magnetic circuit for moving the carriage 3 radially of the optical disk 1. The linear actuator may correspond to the linear motor of the magnetic disk drive device. Reference numerals 5 and 6 depict an inner peripheral stopper and an outer peripheral stopper for determing an innermost and an outermost position of a movable range of the carriage 3, respectively, 7 an innermost track position ( first predetermined position ) accessible by the optical head 2 and 8 a retract position ( second predetermined position ) which is inside of the first predetermined position 7 and at which the carriage 3 is to be locked. The positioning of the optical head 2 with respect to the track on the optical disk 1 is performed similarly to the magnetic disk drive device. In this case, however, it is necessary to prevent mechanical shock due to the fact that optical parts such as objective lenses are used on the optical head 2 and to lock the carrige 3 mounting the optical head 2 thereon when the device is stopped. Therefore, the optical head 2 is moved to the second predetermined position 8 and stored therein by means of the retract function of a capacitor 45. The second predetermined position 8 is at an end of the movable range of the linear actuator and it is inside of the first predetermined position 7 as shown in Fig. 5. Therefore, it is impossible to move the carriage 3 to the second predetermined position 8 by the access operation to the tracks on the optical disk 1 because there is no address at the second predetermined position. Therefore, the carriage 3 is firstly moved to the first predetermined position 7 of which an address exist by the usual access operation and then to the second predetermined position 8 forcibly by the charged energy of the capacitor 45. Due to the fact that, in the retract operation, the capacitor 45 is used to move the carriage 3 from the first predetermined position 7 to the second predetermined position 8, the capacitor 45 must be large enough to store energy necessary to achieve such operation which is usually large when an undesired tilting of the whole device is taken into consideration. This fact makes the whole device large in size necessarily. Further, since the carriage 3 is moved to the second predetermined position 8 forcibly, mechanical shock is necessarily given thereto, resulting in a reduction of reliability of a function of the optical head 2. JP-A-60-171 682 describes a retract system for a disk system. At power source disconnection a delay circuit is activated. During the delay period the microprocessor inside the disk device is interrupted and the disk device carries out the retract operation by itself. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk drive device which is compact in size and reliable in operation due to that a carriage mounting an optical head is moved from a first predetermind position to a second predetermined position at a predetermined reference speed. The object of the invention is solved by an optical disk drive device for positioning a carriage carrying an optical head for directing a light beam towards an optical disk having tracks for information storage and for receiving a reflected beam from said optical disk thereon, said optical disk drive device having an actuator for moving said carriage in a traversing direction with respect to said tracks, as well as having retract means including a signal instruction circuit for providing a retract instruction, characterized by a speed detector for detecting a moving speed of said carriage on the basis of said reflected light, a reference speed generating circuit for determining a reference speed corresponding to the number of tracks to be traversed by said carriage a speed error detection circuit for comparing said moving speed and said reference speed to control an operation speed of said actuator, said signal instruction circuit also providing said number of tracks to be traversed by said carriage upon an access start instruction, and a reference voltage generating circuit responsive to said number of tracks to be traversed by said carriage, said access start instruction and said retract instruction to provide a residual number of tracks left untraversed by said carriage and a carriage moving signal, whereby said carriage is moved from any track to a first predetermined position by an access operation according to said access start instruction and then moved from said first predetermined position to a second predetermined position at a constant speed according to said retract instruction. In the present invention, the carriage mounting the optical head is moved from any track to the first predetermined position by the access operation upon the access start instruction and from the first predetermined position to the second predetermined position at a predetermined reference speed upon the retract instruction, immediately before the device is stopped to operate. Further advantageous embodiments of the invention are given in the dependent claims. BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a block circuit diagram showing an embodiment of the present invention; Fig. 2 is a detailed block diagram of a reference voltage generating circuit in Fig. 1; Fig. 3 is a timing chart showing an operation of the present ivention; Fig. 4 is a block diagram of a conventional magnetic disk drive device; and Fig. 5 is a side view of an access mechanism of a conventional optical disk drive device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In Fig. 1 which shows an embodiment of the present invention and includes an access mechanism similar to that shown in Fig. 4 although not shown, a reference numeral 11 depicts two divided photo detectors for sensing tracks of an optical disk 1 to be traversed across and 12 and 13 an adder amplifier and a subtractor amplifier for providing a sum signal M and a difference signal E of output signals of the optical sensor 11, respectively. A retract means 30 is constituted with a signal instruction circuit 14 for providing number S1 of tracks to be transversed, an access start instruction S3, a retract instruction S5 and a moving direction instruction S7 which are necessary to move a carriage 3 and a reference voltage generating circuit 15 responsive to the difference signal E, the number S1 of tracks to be traversed, the access start instruction S3 and the retract instruction S5 to provide number S2 of tracks left untraversed yet and a carriage moving signal S6. A reference numeral 16 depicts a reference speed generating circuit responsive to the number S2 and the moving direction S7 to provide a reference speed F, 17 a direction detector responsive to a phase difference between the sum signal M and the difference signal E to provide an actual moving direction G of the optical head 2, 18 a speed detector responsive to a frequency of the difference signal E to provide an actual moving speed H of the optical head 2, 19 a direction decision circuit responsive to the moving direction G and the moving speed H to provide a relative speed J having extreme value, 20 a speed error detector responsive to a difference between the relative speed J and the reference speed F to provide a speed error K for a linear actuator ( not shown ), 21 a switch circuit connected to an output side of the speed error detector 20 and adapted to be turned on and off selectively by the carriage moving signal S6 and 22 a linear actuator coil to which the speed error K is supplied through the switch circuit 21. A reference numeral 23 depicts a tracking servo circuit responsive to the difference signal E and the track numer S2 to provide a servo signal L for driving a tracking actuator ( not shown ) and 24 is a tracking actuator coil to which the servo signal L is supplied. Fig. 2 is a block diagram showing the reference voltage generating circuit 15 of the retract means 30 in Fig. 1, in detail. The reference voltage generating circuit 15 includes a pulse generator 31 for converting the difference signal E into a pulse signal S0 for track counting, an access mode instruction generator32 responsive to the access start instruction S3 and the residual track number S2 to provide an access mode instruction S4, an OR gate 33 for providing a logical sum of the retract instruction S5 and the access mode instruction S4 to provide a carriage moving signal S6, a NAND gate 34 for providing a logical product of the pulse signal S0 and the access mode instruction S4 and a counter 35 responsive to the total track number S1 and an output S8 of the NAND gate 34 to provide the residual track number S2. An operation of the embodiment shown in Figs. 1 and 2 will be described with reference to a timing chart shown in Fig. 3. When the optical disc 1 is irradiated with laser beam from a laser diode of the optical head 2, a reflection beam from the optical disk 1 is detected by the divided optical detector 11 from which the track transverse signal is obtained. When a power source of the optical disk drive device is connected during a normal operation, the tracking actuator is driven and controlled by the servo signal L from the tracking servo circuit 23 to trace a desired track of the optical disk 1 with light beam. In case where the optical disk drive device is stopped to operate in order to, for example, derive the optical disk from the device, the carriage 3 on which the optical head 2 is mounted is moved to the first predetermined position 7 and then from the latter position to the second predetermined position 8. In case where the operation of the drive device is to be stopped while the optical beam is tracking a track on the optical disk 1, the signal instruction circuit 14 calculates the number S1 of tracks indicative of an amount of movement from an address position to the first predetermined position 7 and supplies a result to a data input terminal D of the counter 35. Simultaneously therewith, the signal instruction circuit 14 supplies the moving direction S7 of the reference speed output to the reference speed generator 16. Since, in this case, the linear actuator is not actuated, the difference signal E can not be supplied to the reference voltage generating circuit 15. Therefore, the initially stored track number S1 is provided at an output terminal Q of the counter 35 as the residual track number S2. Then, when the signal instruction circuit 14 provides the access start instruction S3, the access mode instruction generator 32 provides an access mode instruction S4 which is in high level indicative of a state where an access is being performed. This access mode instruction S4 becomes, through the OR gate 33, a carriage moving signal S6 upon which the switch circuit 21 is turned on. When the switch 21 is closed, the linear actuator coil 22 is energized, upon which the operation mode is switched from the tracking mode in which light beam tracks the optical disk 1 to the speed control mode in which the carriage 3 is moved under the speed control of the linear actuator. Therefore, the reference speed generator 16 provides the reference speed F having polarity determined by the initially inputted moving direction S7 and value determined by the residual track number S2. In the initial stage of operation, the moving speed H of the linear actuator, i.e., the optical head 2 is zero. Therefore, the relative speed J is also zero, so that the speed error K is determined by the reference speed F, which is supplied through the switch circuit 21 to the linear actuator coil 22. Therefore, the linear actuator is actuated to start the carriage 3 to move toward the first predetermined position 7. With the movement of the carriage 3, light beam moves, upon which the two divided photo detectors 11 provide two signals having different phases and indicative of light beam traversing the tracks. These signals are used by the adder amplifier 12 and the subtractor amplifier 13 to provide the sum signal M and the difference signal E. The direction detection circuit 17 responds to a difference in phase between the sum signal M and the difference signal E and provides the moving direction G of the carriage 3 and the speed detection circuit 18 responds to the frequency of the differene signal E and provides the moving speed H of the carriage 3, i.e., the light beam as an absolute value. The moving direction G and the moving speed H are supplied to the direction decision circuit 19. The direction decision circuit 19 determines the polarity of the moving speed H on the basis of the moving direction G and converts the moving speed H into the relative speed J which is supplied to the error detection circuit 20. On the other hand, the pulse generator 31 of the reference voltage generator 15 responds to the difference signal E to provide the pulse signal S0, one pulse per track, which is supplied through the NAND gate 34 to a count input terminal T of the counter 35. The counter 35 counts down the pulse signal S0 corresponding to the tracks traversed sequentially from the previously stored track number S1 and provides the residual track number S2 at each down-count. That is, as shown in Fig. 3, the residual track number S2 is provided as the counter output according to the pulse output of the difference signal E. The reference speed generating circuit 16 determines the reference speed F having a value corresponding to the residual track number S2 and a polarlity based on the moving direction S7, which is supplied to the speed error detection circuit 20. The speed error detection circuit 20 provides the speed error K on the basis of a difference between the relative speed J and the reference speed F, which is supplied through the switch circuit 21 to the linear actuator coil 22. Thus, the moving speed H of the beam is controlled so that it follows the reference speed F corresponding to the residual track number S2. The moving speed H varies as shown in Fig. 3, the closer the distance of the carriage 3 to the first predetermined position 7 being the smaller the value thereof. The residual track number S2 is supplied to the access mode instruction generating circuit 32 which detects a time point at which a seek operation completes when the residual track number S2 becomes zero and, simultaneously, changes the access mode instruction S4 to low level. Therefore, the NAND gate 34 prohibits a passage of the pulse signal S0 therethrough to stop the down-count operation of the counter 35 and to turn the carriage moving signal S6 from the OR gate 33 to low level to thereby open the switch circuit 21. The tracking servo circuit 23 to which the residual track number S2 is supplied provides the servo signal L on the basis of the difference signal E after the completion of the seek operation upon the access and supplies the signal L to the tracking actuator coil 24. And, by making the light beam to follow the optical disk 1 at the first predetermined position 7, the completion of access operation to the first predetermined position 7 is confirmed. In order to move the carriage 3 from the first predetermined position 7 to the second predetermined postion 8 at a constant speed, the signal instruction circuit 14 supplies the moving track number S1 corresponding to a predetermined reference speed H to the counter 35 so that the residual track number S2 becomes constant, and, simultaneously, changes the retract instruction S5 from low level to high level. The predetermined reference speed H , in this case, should be selected such that it does not affect the optical head 2 adversely when the carriage 3 reaches a storage mechanism ( not shown ) provided in the second predetermined position 8. The retract instruction S5 from the signal instruction circuit 14 is passed through the OR gate 33 and provided at the output of the gate as the carriage moving signal S6 by which the switch circuit 21 is closed. Therefore, the linear actuator is actuated again and the operation is switched from the tracking mode to the speed control mode. Since, at this time, there is no pulse signal S0 at the count input terminal T and so there is no count operation, the residual track number S2 is always constant and thus the reference speed F produced by the reference speed generator circuit 16 is constant. Thus, the linear actuator is controlled at a constant speed and the moving speed H of the carriage 3 becomes the predetermined reference speed H , as shown in Fig. 3. The retract signal S5 based on, for example, a disk eject instruction is preset such that it becomes low level at a time point after a predetermined tim t corresponding to a distance from the first predetermined position 7 to the second predetermined position 8. Therefore, when the time t lapses, the switch circuit 21 is turned on to stop the retract operation and the carriage 3 reaches the second predetermined position 8 and is stored in the storage mechanism therein. Thus, the retract operation for the optical head 2 completes. Although, in the described embodiment, the first predetermined position 7 is set on the innermost track of the accessible range with respect to the optical disk 1, it may set in the outermost accessible track. In such case, the second predetermined position in which the carriage 3 is to be stored may be set in the side of the outermost stopper 6. The first predetermined position 7 may be set in not the innermost track but in any place outside the innermost track so long as the latter is accessible. The linear actuator is described for driving the optical head 2. However, it is possible to use any other actuator for the same purpose. As described hereinbefore, according to the present invention, the retract means comprises the signal instruction circuit for providing the number of tracks to be traversed, the access start instruction and the retract instruction and the reference voltage generating circuit responsive to these instructions to provide the residual track number and the carriage moving signal and operates such that, immediately before the drive device is stopped to operate, the carriage mounting the optical head thereon is moved by the access operation from any track to the first predetermined position according to the access start instruction and then moved from the first predetermined position to the second predetermined position according to the retract instruction at a predetermined reference speed. Therefore, a time required to store the optical head is minimized, there is no need of providing a large capacitor, mechanical shock to be given to the optical head is minimized and thus it is possible to make the optical disk drive device compact and reliable.

Claims: An optical disk drive device for positioning a carriage (3) carrying an optical head (2) for directing a light beam towards an optical disk (1) having tracks for information storage and for receiving a reflected beam from said optical disk (1) thereon, said optical disk drive device having an actuator (4) for moving said carriage (3) in a traversing direction with respect to said tracks, as well as having retract means (30) including a signal instruction circuit (14) for providing a retract instruction, characterized by a speed detector (18) for detecting a moving speed of said carriage (3) on the basis of said reflected light; a reference speed generating circuit (16) for determining a reference speed corresponding to the number of tracks to be traversed by said carriage (3); a speed error detection circuit (20) for comparing said moving speed and said reference speed to control an operation speed of said actuator (4); said signal instruction circuit (14) also providing said number of tracks to be traversed by said carriage (3) upon an access start instruction; and a reference voltage generating circuit (15) responsive to said number of tracks to be traversed by said carriage (3), said access start instruction and said retract instruction to provide a residual number of tracks left untraversed by said carriage (3) and a carriage moving signal, whereby said carriage (3) is moved from any track to a first predetermined position (7) by an access operation according to said access start instruction and then moved from said first predetermined position (7) to a second predetermined position (8) at a constant speed according to said retract instruction. The optical disk drive device as claimed in claim 1, wherein said reference voltage generating circuit (15) comprises a pulse generator (31) for generating a pulse signal on the basis of said reflected beam, an access mode instruction generating circuit (32) responsive to said access start instruction and said residual track number to provide an access mode instruction, an OR gate (33) for providing a logical sum of said retract instruction and said access mode instruction to provide said carriage moving signal, a NAND gate (34) for providing a logical product of said pulse signal and said access mode instruction and a counter circuit (35) having a count input terminal supplied with an output of said NAND gate (34) and a data input terminal supplied with said number of tracks to be traversed by said carriage (3) for providing said residual track number. The optical disk drive device as claimed in claim 1 or 2, wherein said signal instruction circuit (14) provides said retract instruction for a predetermined time period. The optical disk drive device as claimed in claims 1, 2 or 3, wherein said first predetermined position (7) is set in the innermost track of accessible tracks on said optical disk (1) and said second predetermined position (8) is a retract position set inside of said first predetermined position. The optical disk drive device as claimed in claims 1, 2 or 3, wherein said first predetermined position (7) is set in an outermost track of accessible tracks of said optical disk (1) and said second predetermined position (8) is a retract position set outside of said first predetermined position (7). The optical disk drive device as claimed in any of claims 1 to 4, wherein said actuator (4) for moving said carriage (3) comprises linear actuator. The optical disk drive device as claimed in any of claims 1 to 5, wherein said retract instruction is based on a disk eject instruction.

Inventors: KAMITSU, KATSUAKI MITSUBISHI DENKI K.K., NAKATSU, KEIJI MITSUBISHI DENKI K.K., OGAWA, MASAHARU MITSUBISHI DENKI K.K.
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1988
Main classification: G11B7
IPC codes: G11B7, G11B21, G11B19, H04N5