WO2006054540A1 - Objective lens control device and objective lens control method - Google Patents

Abstract

There is provided an objective lens control device (10) having an objective lens (21), applying light from a light source via the objective lens (21) to a disc (31), and receiving the return light. By controlling the position of the objective lens (21), the focus of the light applied is controlled. The objective lens control device (10) includes: an error focus position detection unit (12) or an RF focus position detection unit (13) for detecting the position of the objective lens (21) through which the light irradiated from the light source is focused on the disc (31) by detecting a predetermined signal from the return light received; and a focus drive control unit (17) for controlling the objective lens (21) so that the movement direction of the objective lens (21) in the focus direction is reversed when the error focus position detection unit (12) or the RF focus position detection unit (13) has detected a focus position.

Description

 Specification

 Objective lens control device and objective lens control method

 Technical field

 The present invention relates to an objective lens control device and an objective lens control method.

 Background art

 [0002] CD (Compact Disk) Player Z Recorder and DVD (Digital Video (Versatile) Disk) Player Recording and playback devices such as Z Recorder are equipped with a pickup of the recording and playback device. The information recorded on the optical disk is read by irradiating the light beam and detecting the reflected light from the information recording surface of the optical disk.

 [0003] Further, the pickup includes an actuator for driving and controlling the objective lens. The object lens focuses the emitted light beam on the information recording surface of the optical disc, and the focus of the light beam irradiated on the information recording surface changes depending on the distance between the objective lens and the information recording surface. To do.

 [0004] For this reason, a CD player or the like needs to control the actuator by the focus servo, and drive and control the position of the objective lens so that the information recording surface is irradiated with the optimally focused light beam.

 [0005] The objective lens of the optical pickup device described in Patent Document 1 is mounted on an actuator and moved in the focus direction of the disc so as to form a light spot on the disc. That is, the actuator enables the objective lens to be accurately moved to a desired position by the current applied to the moving coil and the electromagnetic force formed by the permanent magnet.

[0006] The pickup actuator described in Non-Patent Document 1 moves the pickup within a predetermined range (± 0.7 mm).

FIG. 9 is a diagram for explaining the movement of a conventional objective lens. In the conventional objective lens, the objective lens is moved within a predetermined range in the focus direction of the disc, and signal measurement and focus pull-in are performed near the in-focus position. [0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-152472

 Non-Patent Document 1: Hikaru Nishihara, 6 others, "Thin DVD—Pickup for ROM", [online], 19 December 1998, Sharp Technical Report, [searched August 12, 2004], Internet URLwww. s harp.co.jp/ corporate / rd / journa 卜 72 / pdf / 72— 20. pdf>

 Disclosure of the invention

 Problems to be solved by the invention

However, in the former and the latter prior arts described above, if the disc and the objective lens collide due to a variation in the mechanical dimensions of the disc recording device equipped with the actuator and the disc reproducing device equipped with the actuator, etc. When there was a problem. In addition, there was a problem when the disc collided with the objective lens when the disc surface shake was large.

 [0010] The problem to be solved by the present invention includes, for example, the problem of collision between the disc and the objective lens caused by the movement of the objective lens in Patent Document 1 and Non-Patent Document 1 described above.

 Means for solving the problem

 In order to solve the above-described problems and achieve the object, the invention according to claim 1 of the present invention includes an objective lens, and irradiates the optical recording medium with light from the light source via the objective lens. In the objective lens control device that controls the focus of the irradiated light by controlling the position of the objective lens, a predetermined signal is detected from the received return light. When the focus position detection unit detects the focus position, the focus position detection unit detects the position of the objective lens where the light emitted from the light source is focused on the optical recording medium as the focus position. And an objective lens control unit that controls the objective lens so as to reverse the moving direction of the objective lens in the focus direction.

The invention according to claim 4 is an apparatus that includes an objective lens, irradiates the optical recording medium with light from a light source via the objective lens, and receives the return light. The objective lens In the objective lens control device that controls the focus of the emitted light by controlling the position of the light, the light emitted from the light source is detected by detecting a predetermined signal from the received return light. The position of the objective lens that focuses on the medium is the in-focus position. A focus position detection unit that detects the position of the objective lens, and a timing for reversing the moving direction of the objective lens in the focus direction according to the focus position detected by the focus position detection unit, and generates timing information representing the timing And an objective lens control unit that reverses the moving direction of the objective lens in the focus direction at a timing based on the timing information.

 [0013] The invention according to claim 6 is an apparatus that includes an objective lens, irradiates light onto the optical recording medium from a light source via the objective lens, and receives the return light. The objective lens In the objective lens control device that controls the focus of the emitted light by controlling the position of the light, the light emitted from the light source is detected by detecting a predetermined signal from the received return light. A focus position detecting step for detecting a position of the objective lens focused on the medium as a focus position; and a reversing step for reversing the moving direction in the focus direction of the objective lens.

 The invention according to claim 7 is an apparatus that includes an objective lens, irradiates the optical recording medium with light from a light source via the objective lens, and receives the return light. The objective lens In the objective lens control device that controls the focus of the emitted light by controlling the position of the light, the light emitted from the light source is detected by detecting a predetermined signal from the received return light. A focus position detection step for detecting the position of the objective lens that focuses on the medium as a focus position, and the movement direction of the objective lens in the focus direction is reversed according to the focus position detected by the focus position detection unit. A timing information generation step of determining timing to generate and generating timing information representing the timing, and at a timing based on the timing information, the objective lens Characterized in that it comprises a step of reversing the Contact Keru moving direction in the focusing direction, a.

The invention according to claim 8 is an apparatus that includes an objective lens, irradiates light onto the optical recording medium from a light source via the objective lens, and receives the return light. The objective lens In a program for causing a computer to execute the objective lens control method for controlling the focus of the irradiated light by controlling the position of the light source, by detecting a predetermined signal from the received return light, An in-focus position detecting step for detecting, as an in-focus position, the position of an objective lens at which the irradiated light is in focus on the optical recording medium; And a reversing step of reversing the moving direction of the object lens in the focus direction, and causing the computer to execute the reversing step.

 [0016] The invention according to claim 9 is an apparatus that includes an objective lens, irradiates the optical recording medium with light from a light source via the objective lens, and receives the return light. The objective lens In a program for causing a computer to execute the objective lens control method for controlling the focus of the irradiated light by controlling the position of the light source, by detecting a predetermined signal from the received return light, A focus position detecting step for detecting, as a focus position, the position of the objective lens at which the irradiated light is focused on the optical recording medium, and the focus of the objective lens according to the focus position detected by the focus position detecting unit. A timing information generation step for determining timing for reversing the moving direction in the direction, and generating timing information representing the timing; and the timing information In group Dzu was timing, characterized in that to perform a reversing step of reversing the direction of movement in the focus direction of the objective lens, to a computer.

 Brief Description of Drawings

 FIG. 1 is a block diagram illustrating a configuration of an objective lens control device according to a first embodiment.

 FIG. 2 is a flowchart showing an operation procedure of the objective lens control apparatus according to the first embodiment.

 [FIG. 3-1] FIG. 3-1 is a diagram (1) for explaining the operation of the objective lens during signal level detection according to the first embodiment.

 FIG. 3-2 is a diagram (2) for explaining the operation of the objective lens at the time of signal level detection according to the first embodiment.

 [Fig. 4-1] Fig. 41 is a diagram (1) for explaining the operation of the objective lens in the conventional signal level detection.

 [Fig. 4-2] Fig. 42 is a diagram (2) for explaining the operation of the objective lens in the conventional signal level detection.

 FIG. 5 is a block diagram illustrating a configuration of an objective lens control device according to the second embodiment.

FIG. 6 is a flowchart illustrating an operation procedure of the objective lens control device according to the second embodiment. [FIG. 7-1] FIG. 7-1 is a diagram (1) for explaining the operation of the objective lens at the time of signal level detection according to the second embodiment.

 FIG. 7-2 is a diagram (2) for explaining the operation of the objective lens at the time of signal level detection according to the second embodiment.

 [FIG. 8-1] FIG. 8-1 is a diagram (1) for explaining the operation of the objective lens at the time of conventional focus pull-in.

 [FIG. 8-2] FIG. 8-2 is a diagram (2) for explaining the operation of the objective lens during the conventional focus pull-in.

 FIG. 9 is a diagram for explaining the movement of a conventional objective lens.

 Explanation of symbols

 Objective lens controller

 12 Focuser position detector

 13 RF focus position detector

 14 Inversion timing calculator

 15 Error signal generator

 16 RF signal generator

 17 Focus drive controller

 19 Pickup

 20 Dyrino

 21 Objective lens

 31 discs

 32 disc motor

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the objective lens control device and the objective lens control method according to the present invention will be described. The present invention is not limited to the embodiments. In the following, the outline and features of the objective lens control apparatus and objective lens control method of the present invention will be described as embodiments, and then examples relating to the objective lens control apparatus and objective lens control method will be described. [0020] [Embodiment]

 In the present embodiment, the objective lens control device controls the focus of the irradiation beam when reading or recording recording medium force information such as CD (Compact Disk) and DVD (Digital Video Disk). In other words, the objective lens control device controls the position of the objective lens of a pick-up (optical pickup) that irradiates the information recording surface of the disc when reading information from a disc such as a CD. This controls the focus of the irradiation beam on the disc.

 [0021] For example, the signal detection of the reflected beam with respect to the beam irradiated on the disk and the focus closing when reading the information recorded on the disk are performed by reciprocating the objective lens in a direction perpendicular to the surface of the disk. . The reflected beam signal detection and focus closing are performed by a focus error signal near the focus position of the irradiation beam irradiated from the pickup.

 [0022] For this reason, when the reflected beam signal is detected or the focus is closed, the objective lens is moved within a predetermined range in a direction perpendicular to the surface of the disc, and the focus search is performed. There may be a collision between the objective lens and the disk.

 Therefore, in the present embodiment, the operation of the objective lens is controlled without setting a range in which the objective lens can move in a direction perpendicular to the in-plane direction of the disc. In other words, when the objective lens is brought close to the disk in order to detect the reflected beam signal or to close the focus, if the objective lens passes the in-focus position, immediately or after a predetermined time has passed (or the objective lens is in focus). After the position elapses, the objective lens movement is reversed (moved away from the disc surface) after the objective lens movement distance calculated based on the timing results has reached a predetermined distance.

 [0024] At the in-focus position through which the objective lens moves in the direction approaching the disc surface, the disc type is discriminated, such as whether the disc is a power DVD or a DVD, and the objective lens is far from the disc surface force. At the in-focus position that passes when moving in the direction of force, the reflected beam signal is detected and the focus is closed.

For this reason, in the present embodiment, the in-focus position when the objective lens moves is detected, and the operation of the objective lens is controlled based on the detection of the in-focus position. In-focus position detection For example, detection is based on the focus error signal, tracking error signal, RF signal, etc. extracted from the reflected beam force from the disk.

As described above, according to the embodiment, when the objective lens approaches the disc in order to detect the signal of the disc force or perform the focus close, immediately after the objective lens passes the in-focus position or a predetermined value. Since the direction of movement of the objective lens is reversed after a lapse of time, it is possible to avoid collision between the objective lens and the disk. This makes it possible to detect signals from the disk stably.

 Example 1

 FIG. 1 is a block diagram showing a configuration of an objective lens control device that works according to the present invention. The objective lens control device 10 is a device that controls the focus of the light beam applied to the disk 31, and includes an error signal generation unit 15, an RF (Radio Frequency) signal generation unit 16, an error focus position detection unit 12, and an RF focus. It consists of a position detection unit 13, a focus drive control unit 17, a pickup 19, and a driver 20. Here, the error focus position detection unit 12 and the RF focus position detection unit 13 correspond to the focus position detection unit described in the claims, and the focus drive control unit 17 and the driver 20 serve as the objective lens control unit. Correspond.

 The pickup 19 is configured to include an objective lens 21. The pickup 19 is equipped with an actuator (not shown), and the actuator controls the focus of the light beam applied to the disk 31 by driving the objective lens 21. The object lens 21 of the pickup 19 moves in a direction parallel to the plane of the disc 31 and a direction perpendicular to the plane of the disc 31 to irradiate the disc 31 with the irradiation beam from the actuator, The reflected beam reflected from is sent to the actuator. The pickup 19 transmits the reflected beam from the objective lens 21 to the error signal generator 15 and the RF signal generator 16.

 The error signal generation unit 15 also generates a focus error signal, a tracking error signal, and the like for the reflected beam force sent from the pickup 19. The RF signal generator 16 generates an RF signal or the like from the reflected beam sent from the pickup 19.

The error focus position detection unit 12 detects the focus error signal and tracking error signal generated by the error signal generation unit 15. The RF focus position detector 13 is an RF signal generator 1 6 detects the RF signal generated and sends the detection signal to the focus drive controller 17

[0031] After receiving the detection signal, the focus drive control unit 17 controls the driver 20 to start operation after a predetermined time stored in a memory (not shown). The focus drive control unit 17 generates pickup drive information (drive voltage or the like) for controlling the operation of the pickup 19 and transmits it to the driver 20.

 The driver 20 drives the disk motor 32 and the pickup 19 based on the pickup drive information from the focus drive control unit 17. The driver 20 supplies a current (drive current) to a focus coil (not shown) provided in the pickup 19 and moves the objective lens of the pickup 19 in the light beam irradiation direction (perpendicular to the surface of the disk 31). Let

 The disk motor 32 is connected to the driver 20 and drives (rotates) the disk 31 with current supplied from the driver 20. The disk 31 is a recording medium that is recorded and reproduced by a CD (Compact Disk) player Z recorder and a DVD (Digital Video Disk) player Z recorder, and is a disk such as a CD or a DVD.

 Next, the operation of the objective lens control device will be described. FIG. 2 is a flowchart illustrating the operation procedure of the object lens control apparatus according to the first embodiment. The objective lens 21 of the pickup 19 is moved in the direction perpendicular to the surface of the disk 31 by the drive current from the dryno. In the first embodiment, the objective lens 21 moves in a direction perpendicular to the surface of the disk 31 in order to perform a disc type determination process described later and to detect the signal level of the reflected beam reflected from the disc 31. .

 Here, first, the objective lens 21 moves in a direction approaching the disk 31 (step S100). The pickup irradiates the disk 31 with the irradiation beam through the objective lens 21 when the objective lens 21 is moving. . While the objective lens 21 is moving, the reflected beam reflected from the disk 31 is sent from the pickup 19 to the error signal generator 15 and the RF signal generator 16.

The error signal generator 15 generates a focus error signal and a tracking error signal as information for determining whether or not the objective lens 21 has crossed the in-focus position from the reflected beam from the pickup 19. The RF signal generator 16 The RF signal is generated as information for determining whether or not the objective lens 21 has crossed the in-focus position.

 The error signal generation unit 15 transmits the generated focus error signal and tracking error signal to the error focus position detection unit 12. The RF signal generation unit 16 transmits the generated RF signal to the RF focus position detection unit 13.

 The error focus position detector 12 detects the focus error signal and tracking error signal generated by the error signal generator 15. The RF focus position detector 13 detects the RF signal generated by the RF signal generator 16. In the first embodiment, a case where a focus error signal is used as information for determining whether or not the objective lens 21 has crossed the in-focus position will be described.

 While the objective lens 21 is at a position far from the disk 31, the error focus position detection unit 12 detects the focus error signal as almost zero. When the objective lens 21 approaches the vicinity of the disk 31 (for example, about 10 m), the level of the focus error signal gradually increases, and this focus error signal is detected by the error focus position detection unit 12. As the objective lens 21 gets closer to the disk 31, the level of the focus error signal increases in accordance with the distance between the objective lens 21 and the disk 31 (as it gets closer). The error focusing position detection unit 12 detects the peak (maximum point) of the focus error signal. As the objective lens 21 gets closer to the disk 31, the level of the focus error signal decreases according to the distance between the objective lens 21 and the disk 31, and becomes 0 at the in-focus position.

 In the first embodiment, the disc type such as whether the disc 31 is a CD or a DVD is discriminated when the first in-focus position is detected, and the signal is detected when the in-focus position is detected for the second time. Measure the signal level (the amount of reflected beam received from the disk 31) and reflectivity.

 [0041] Here, since it is the detection of the first in-focus position, while the error in-focus position detector 12 detects the force error signal, the disc type is discriminated by disc discriminating means or the like, not shown. Etc.

The error focus position detection unit 12 detects whether or not the objective lens 21 has passed the focus position by detecting a focus error signal while the objective lens 21 is moving so as to approach the disk 31. Judgment is made (step S110). [0043] When the error focus position detection unit 12 determines that the objective lens 21 has passed (crossed) the focus position (Yes in step S110), the error focus position detection unit 12 detects that the objective lens 21 is in focus. A signal indicating that the focus position has been passed (hereinafter referred to as a focus position passing signal) is transmitted to the focus drive control unit 17.

 The focus drive control unit 17 receives the in-focus position passing signal from the error in-focus position detection unit 12 so that the driver 20 starts operating after a predetermined time stored in a memory (not shown). To control. Here, the driver 20 is controlled so that the pickup 19 is moved away from the disk 31 in X milliseconds.

 The driver 20 controls the drive current of the pickup 19 so that the objective lens 21 moves away from the disk 31 X milliseconds after the objective lens 21 passes the in-focus position. The pickup 19 controls the movement of the objective lens 21 so that the objective lens 21 moves away from the disk 31 based on the drive current from the driver 20. The objective lens 21 is driven (reversed) to move away from the disk 31 in a direction perpendicular to the plane of the disk 31 (step S 120).

) o

 When the objective lens 21 is driven away from the disc 31 in a direction perpendicular to the in-plane direction of the disc 31, the objective lens 21 approaches the in-focus position again. When the objective lens 21 approaches the in-focus position by a predetermined distance (away from the disc 31), the focus error signal level decreases according to the distance between the objective lens 21 and the disc 31, and the focus error signal is output at the in-focus position. 0.

 [0047] The error focus position detection unit 12 detects the focus error signal while the objective lens 21 is moving away from the disc 31 to detect the force that the objective lens 21 has passed through the focus position. Judgment is made or not (step S130).

 [0048] When the error focus position detection unit 12 determines that the objective lens 21 has passed the focus position

 (Step S130, Yes), because this is the second detection of the focus position, the error focus position detector 12 detects the focus error signal while the error focus position detector 12 detects the focus error signal. The level is measured (step S140).

The objective lens 21 is driven in a direction in which the objective lens 21 moves away from the disk 31 even after passing through the in-focus position. The focus drive control unit 17 stores a predetermined time (for example, y milliseconds) stored in a memory (not shown). After the elapse of (after), the driver 20 is controlled so that the objective lens 21 moves in a direction approaching the disk 31. Here, the driver 20 is controlled so as to move the pickup 19 in the direction approaching the disk 31, for example, y milliseconds after the objective lens 21 passes the in-focus position.

The driver 20 controls the drive current of the pickup 19 so that the objective lens 21 moves in the direction approaching the disk 31 after y milliseconds. The pickup 19 controls the movement of the objective lens 21 based on the drive current from the driver so that the objective lens 21 approaches the disk 31.

The objective lens 21 is driven so as to approach the disk 31 in a direction perpendicular to the surface of the disk 31. Thereafter, the objective lens control device 10 performs focus closing and the like as necessary.

 Here, with reference to FIG. 3A and FIG. 3B, a supplementary explanation of FIG. 2, which is a flowchart for explaining the operation of the object lens when the signal level is detected according to the first embodiment, will be given. . In each figure, the vertical axis indicates the position of the objective lens (objective lens 21) in the focus direction, and the horizontal axis indicates time. FIG. 3A shows a case where the disc 31 has a small run-out, and FIG. 3-2 shows a case where the disc 31 has a large run-out.

 As shown in FIG. 3-1, the objective lens 21 is driven so as to approach the disk 31, and after the objective lens 21 passes the in-focus position (focus point), the objective lens 21 is immediately removed from the disk 31. The drive direction is reversed in the direction to move away. Thus, the objective lens 21 does not collide with the disk 31.

 [0054] As shown in FIG. 3-2, when the disc 31 has a large runout, the in-focus position also changes with the runout of the disc 31. Even if the surface of the disc 31 is large, after the objective lens 21 has passed through the in-focus position, the objective lens 21 is immediately reversed by moving the objective lens 21 away from the disc 31. No longer collides with disk 31

In order to clarify the effect of the present embodiment, FIGS. 41 and 42 are diagrams for explaining the operation of the objective lens at the time of conventional signal level detection. Fig. 4-1 shows the case where the disc 31 has a small run-out, and Fig. 4-2 shows the case where the disc 31 has a great run-out. As shown in FIG. 4A, the objective lens 21 moves by a predetermined distance (eg, ± 0.7 mm) regardless of the focus position, and performs a focus search. For this reason, when the distance between the objective lens 21 and the disk 31 is short at the in-focus position, the collision between the objective lens 21 and the disk 31 occurs.

 As shown in FIG. 42, when the disc 31 has a large runout, the in-focus position also changes with the runout of the disc 31. When the surface of the disk 31 is large and the objective lens 21 moves by a predetermined distance regardless of the in-focus position and performs a focus search, a collision between the objective lens 21 and the disk 31 occurs.

 In the first embodiment, the objective lens 21 moves in the direction of approaching from the disk 31 after a predetermined time has passed after the objective lens 21 has passed the in-focus position. The objective lens 21 may be moved in a direction approaching the disk 31 after a predetermined distance has passed after the 21 has passed the in-focus position. In this case, for example, a timing unit is newly provided, and the error focus position detection unit 12 detects the focus position and starts measuring the force, and measures the time until the objective lens spends moving a predetermined distance. After that, move the objective lens 21 in the direction approaching the disc 31.

 The focus drive control unit 17 controls the driver 20 by receiving the focus position passing signal from the error focus position detection unit 12. The driver 20 controls the drive current of the pickup 19 so that the objective lens 21 moves away from the disk 31 based on the instruction information of the focus drive controller 17 force. The pickup 19 controls the movement of the objective lens 21 so that the objective lens 21 is moved away from the disk 31 based on the drive current from the driver 20. Then, the objective lens 21 is driven (reversed) so as to move away from the disk 31 in a direction perpendicular to the in-plane direction of the disk 31.

In the first embodiment, the error focus position detection unit 12 controls the operation of the objective lens 21 by detecting the focus error signal. However, the error focus position detection unit 12 The operation of the objective lens 21 may be controlled by detecting the tracking error signal. When the error focus position detection unit 12 detects a tracking error signal, the error focus position detection unit 12 determines whether or not the objective lens 21 has passed through the focus position based on the tracking error signal. The tracking error signal is Before the focus is reached, it appears as a large amplitude at the moment when the objective lens reaches the in-focus position. Therefore, if this is detected, it can be determined whether or not the objective lens has passed the in-focus position. I'll do it.

 In addition, the operation of the objective lens 21 may be controlled by the RF focus position detector 13 detecting the RF signal. When the RF focus position detection unit 13 detects an RF signal, the RF focus position detection unit 13 determines whether or not the objective lens 21 has passed through the focus position based on the RF signal. The error focus position detection unit 12 determines that the objective lens 21 has passed the focus position when the signal level of the RF signal shows the maximum, for example.

 [0062] If it is possible to determine whether or not the objective lens 21 has passed through the in-focus position, the objective lens 21 is not limited to the focus error signal, the tracking error signal, and the RF signal. The operation of the objective lens 21 may be controlled by determining whether or not the force has passed. In the first embodiment, the objective lens control device 10 is configured to include both the error focus position detection unit 12 and the RF focus position detection unit 13, but the objective lens control device 10 is configured to detect the error focus position. The unit 12 and the RF focus position detection unit 13 may be configured to include either one of them. That is, the objective lens control device 10 only needs to include at least one means for determining whether or not the objective lens 21 has passed the in-focus position.

 [0063] Further, based on two or more signals out of the focus error signal, tracking error signal, RF signal, etc., the RF focus position detection unit 13 has passed the objective lens 21 through the focus position. It may be determined whether or not it is correct.

 In this way, since the focus error signal is detected when the objective lens 21 approaches the disc 31 in order to detect the signal from the disc 31, the objective lens 21 determines the in-focus position. It becomes possible to control based on information on whether or not the force has passed.

As described above, according to the first embodiment, when the objective lens 21 approaches the disk 31 in order to detect a signal from the disk 31, after the objective lens 21 has passed the in-focus position, a predetermined time has passed. Since the moving direction of the objective lens 21 is reversed after moving a predetermined distance or immediately, the collision between the objective lens 21 and the disk 31 can be avoided. Therefore, as is apparent from a comparison of FIGS. 4 and 4 which are the prior art and FIGS. 3A and 3B of the present embodiment, there is a case where the variation in mechanical dimensions of the pickup 19 is large. Disc 31 The objective lens must be closer to the low-density disc than the low-density disc, even if there is a large amount of surface blur, or the minimum pit length is very short. It becomes possible to avoid the collision between 21 and the disk 31. As a result, signal detection from the disk 31 can be performed stably.

 Example 2

 Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the operation of the objective lens 21 when detecting the in-focus position is controlled based on a focus error signal or the like. Also in the second embodiment, the operation of the objective lens 21 is controlled by the objective lens control device 10 having the same configuration as that of the first embodiment to control the focus.

 FIG. 5 is a block diagram illustrating a configuration of the objective lens control device according to the second embodiment. FIG. 5 is a block diagram showing a configuration of the objective lens control apparatus according to the first embodiment, and a reversal timing calculation unit (timing information generation unit) 14 is newly provided.

 The inversion timing calculation unit 14 calculates the timing for controlling the moving direction of the pickup 19 (objective lens 21) based on the in-focus position detected by the error in-focus position detection unit 12, and the inversion timing calculation unit The timing calculated by 14 is sent as control information to the focus drive controller 17.

 FIG. 6 is a flowchart illustrating an operation procedure of the objective lens control device according to the second embodiment. The objective lens 21 of the pickup 19 is moved in a direction perpendicular to the surface of the disk 31 by the drive current from the driver. In the second embodiment, the objective lens 21 moves in a direction perpendicular to the surface of the disk 31 in order to perform the disc type determination process and the focus close.

 Here, first, the objective lens 21 moves in a direction approaching the disk 31 (step S200). The pickup irradiates the disk 31 with the irradiation beam through the objective lens 21 when the objective lens 21 is moving. .

Thereafter, whether or not the objective lens 21 has passed through the in-focus position is determined by the same processing as in the first embodiment. The steps S110 to S130 in FIG. 2 described in the first embodiment correspond to the steps S210 to S230 in FIG. 6 in the second embodiment. That is, while the objective lens 21 is moving, the reflected beam reflected from the disk 31 generates an error signal from the pickup 19. Unit 15 and RF signal generation unit 16 are transmitted.

The error signal generator 15 generates a focus error signal and a tracking error signal as information for determining whether or not the objective lens 21 has crossed the in-focus position from the reflected beam from the pickup 19. The RF signal generation unit 16 generates an RF signal as information for determining whether or not the reflected beam force objective lens 21 from the pickup 19 has crossed the in-focus position.

 The error signal generation unit 15 transmits the generated focus error signal and tracking error signal to the error focus position detection unit 12. The RF signal generation unit 16 transmits the generated RF signal to the RF focus position detection unit 13.

 The error focus position detector 12 detects the focus error signal and tracking error signal generated by the error signal generator 15. The RF focus position detector 13 detects the RF signal generated by the RF signal generator 16. Here, a case where a focus error signal is used as information for determining whether or not the objective lens 21 has crossed the in-focus position will be described.

 While the objective lens 21 is at a position far from the disk 31, the error focus position detection unit 12 detects the focus error signal as almost zero. When the objective lens 21 approaches the vicinity of the disk 31, the level of the focus error signal gradually increases, and this focus error signal is detected by the error focus position detection unit 12. As the objective lens 21 gets closer to the disk 31, the level of the focus error signal increases in accordance with the distance between the objective lens 21 and the disk 31. Then, the error focus position detector 12 detects the peak of the focus error signal. As the objective lens 21 comes closer to the disc 31, the level of the focus error signal decreases according to the distance between the objective lens 21 and the disc 31, and becomes 0 at the in-focus position.

 In the second embodiment, the disc type is determined when the first in-focus position is detected, and the focus is pulled in when the second in-focus position is detected. Here, since it is the detection of the first in-focus position, the disc type is discriminated.

[0077] The error focus position detection unit 12 detects the focus error signal while the objective lens 21 moves so as to approach the disk 31, so that the objective lens 21 passes the focus position. It is determined whether or not the power has been reduced (step S210).

When the error focus position detection unit 12 determines that the objective lens 21 has passed the focus position (Yes in step S210), the error focus position detection unit 12 detects the focus position passage information (for example, the focus position). Information indicating the distance between the optical recording medium and the optical recording medium) is transmitted to the inversion timing calculation unit 14.

 [0079] Upon receiving the in-focus position passage information, the inversion timing calculation unit 14 determines a predetermined time (after X milliseconds) based on the in-focus position passage information, and performs control indicating the determined predetermined time. Create information. This control information is transmitted from the inversion timing calculation unit 14 to the focus drive control unit 17. If it is desired to move the objective lens 21 away from the disk 31 immediately after the objective lens 21 passes the in-focus position, x = 0 is set.

 The focus drive control unit 17 receives the control information from the inversion timing calculation unit 14 and controls the driver 20 based on the control information. Here, the driver 20 is controlled to move the pick-up 19 away from the disk 31 in X milliseconds.

 The driver 20 controls the drive current of the pickup 19 so that the objective lens 21 moves away from the disk 31 after X milliseconds. The pickup 19 controls the movement of the objective lens 21 so that the objective lens 21 is moved away from the disk 31 based on the drive current from the driver 20. The objective lens 21 is driven to move away from the disk 31 in a direction perpendicular to the in-plane direction of the disk 31 (step S220).

 By driving the objective lens 21 away from the disc 31 in a direction perpendicular to the in-plane direction of the disc 31, the objective lens 21 approaches the in-focus position again. When the objective lens 21 approaches the in-focus position by a predetermined distance (away from the disc 31), the focus error signal level decreases according to the distance between the objective lens 21 and the disc 31, and the focus error signal is output at the in-focus position. 0.

 The error focus position detector 12 detects the focus error signal while the objective lens 21 is moving away from the disk 31 to detect the force that the objective lens 21 has passed through the focus position. Determine whether or not (step S230).

 [0084] When the error focus position detection unit 12 determines that the objective lens 21 has passed the focus position

(Step S230, Yes). Here, the focus position is detected because it is the second focus position detection. Rose (Step S240). In this focus close, the driver 20 controls the pickup 19 so that the objective lens 21 is drawn into the focal depth with respect to the disk 31.

 The error focus position detection unit 12 detects a focus error signal during the focus close process, and determines whether the focus close is successful based on the focus error signal (step S250).

 The error focus position detection unit 12 transmits a determination result (hereinafter, referred to as “close determination result information”) as to whether or not the force has failed to close the focus to the inversion timing calculation unit 14. The inversion timing calculation unit 14 creates control information related to the movement of the objective lens 21 based on the close determination result information from the error focus position detection unit 12.

 [0087] When the error focus position detection unit 12 determines that the focus close has failed (step S250, No), the inversion timing calculation unit 14 performs predetermined processing after the objective lens 21 has passed the focus position. Control information is created so that the objective lens 21 moves in the direction approaching the disk 31 after the elapse of time (after y milliseconds). This control information is transmitted from the inversion timing calculation unit 14 to the focus drive control unit 17.

 The focus drive control unit 17 receives the control information from the inversion timing calculation unit 14 and controls the driver 20 based on the control information. Here, after the objective lens 21 passes through the in-focus position, the driver 20 is controlled so as to move the pickup 19 in a direction approaching the disk 31 after y milliseconds, for example.

 The driver 20 controls the drive current of the pickup 19 so that the objective lens 21 moves in the direction approaching the disk 31 after y milliseconds. The pickup 19 controls the movement of the objective lens 21 based on the drive current from the driver so that the objective lens 21 approaches the disk 31.

Thus, after the objective lens 21 passes the in-focus position, or after the focus drive control unit 17 receives the control information, the objective lens 21 moves away from the disk 31 for y milliseconds, and thereafter The objective lens 21 moves so as to approach the disk 31 (step S2 60). Then, the same processing as steps S210 to S250 is repeated again. Here, the processing power of steps S270 to S300 corresponds to the processing of S steps S210 to S250.

[0091] In the second embodiment, focus close fails in step S250. After that, the focus close process is performed once again by the processes in steps S260 to S300. However, if the focus close process fails, the focus close process may be repeated a plurality of times. In this case, the processes in steps S260 to S300 are repeated several times until the focus close is successful.

 Here, with reference to FIG. 7-1 and FIG. 7-2, supplementary explanation of FIG. 6, which is a flowchart for explaining the operation of the object lens at the time of signal level detection according to the second embodiment, will be given. . In each figure, the vertical axis indicates the position of the objective lens (objective lens 21) in the focus direction, and the horizontal axis indicates time. FIG. 7-1 shows the case where the disc 31 has a small runout, and FIG. 7-2 shows the case where the disc 31 has a great runout.

 As shown in FIG. 7-1, the objective lens 21 is driven so as to approach the disk 31. After the objective lens 21 passes the in-focus position (in-focus position), the objective lens 21 immediately moves to the disk 31. The drive direction is reversed in a direction away from the drive. Thus, the objective lens 21 does not collide with the disk 31.

 As shown in FIG. 7-2, when the disc 31 has a large surface shake, the in-focus position also changes as the disc 31 shakes. Even if the surface of the disc 31 is large, after the objective lens 21 has passed through the in-focus position, the objective lens 21 is immediately reversed by moving the objective lens 21 away from the disc 31. No longer collides with disk 31

In order to clarify the effect of the present embodiment, FIGS. 8A and 8B are diagrams for explaining the operation of the objective lens when the conventional force is pulled. Fig. 8-1 shows the case where the disc 31 has a small runout, and Fig. 8-2 shows the case where the disc 31 has a large runout.

 As shown in FIG. 8-1, the objective lens 21 moves by a predetermined distance (eg, ± 0.7 mm) regardless of the focus position, and performs a focus search. For this reason, when the distance between the objective lens 21 and the disk 31 is short at the in-focus position, the collision between the objective lens 21 and the disk 31 occurs.

As shown in FIG. 8-2, when the disc 31 has a large runout, the in-focus position also changes with the runout of the disc 31. The objective lens 21 is When a focus search is performed by moving a predetermined distance regardless of the in-focus position, a collision between the objective lens 21 and the disk 31 occurs.

 Note that, as in the first embodiment, whether or not the objective lens 21 has passed through the in-focus position may be determined based on a tracking error signal or an RF signal. Similarly to the first embodiment, the movement in the direction of moving away from the disk 31 after passing through the focusing position of the objective lens 21 is performed after the objective lens 21 has moved a predetermined distance or after focusing. Immediately after passing through the position, it will move away from the disk 31 in the direction of force.

 Furthermore, similarly to the first embodiment, the objective lens control device 10 only needs to include at least one means for determining whether or not the objective lens 21 has passed the in-focus position.

 [0100] As described above, since the focus error signal is detected when the objective lens 21 approaches the disk 31 to perform the focus pull-in process, the objective lens 21 has passed the in-focus position in the operation of the objective lens 21. It becomes possible to control based on the information of force.

 [0101] Thus, according to Example 2, when the objective lens 21 approaches the disk 31 in order to close the focus, the objective lens 21 passes the in-focus position, and after a predetermined time has passed, the objective lens Since 21 reverses the direction of movement of the objective lens 21 after a predetermined time or immediately, it is possible to avoid collision between the objective lens 21 and the disk 31. Therefore, as can be seen from the comparison between Fig. 8-1 and Fig. 8-2, which are conventional technologies, and Fig. 7-1 and Fig. 7-2, which are the present embodiment, there is variation in the mechanical dimensions of the pickup 19. If the disk is large or the surface of the disk 31 is large, or if the minimum pit length is very short, the objective lens must be closer to the low-density disk. Even if it exists, it becomes possible to avoid the collision between the objective lens 21 and the disk 31. As a result, signal detection from the disk 31 can be performed stably.

Claims

The scope of the claims

 [1] An apparatus that includes an objective lens, irradiates light onto the optical recording medium through the objective lens in addition to a light source, and receives the return light. By controlling the position of the objective lens, In an objective lens control device that controls the focus of irradiated light,

 An in-focus position detecting unit that detects a position of an objective lens at which the light emitted from the light source is in focus on the optical recording medium by detecting a predetermined signal from the received return light;

 An objective lens control device comprising: an objective lens control unit that controls the objective lens so as to reverse a moving direction of the objective lens in a focus direction when the in-focus position detecting unit detects the in-focus position. .

 [2] The objective according to claim 1, wherein when the in-focus position detection unit detects the in-focus position, the objective lens control unit immediately reverses the moving direction of the objective lens in the focus direction. Lens control device.

[3] The objective lens control unit reverses the movement direction of the objective lens in the focus direction after a predetermined time has elapsed after the focus position detection unit has detected the focus position. The objective lens control device according to 1.

[4] An apparatus that includes an objective lens, irradiates light onto the optical recording medium via the objective lens in addition to the light source, and receives the return light. By controlling the position of the objective lens, In an objective lens control device that controls the focus of irradiated light,

 An in-focus position detecting unit that detects a position of an objective lens at which the light emitted from the light source is in focus on the optical recording medium by detecting a predetermined signal from the received return light;

 A timing information generation unit that determines a timing for reversing the moving direction of the objective lens in the focus direction according to the focus position detected by the focus position detection unit, and generates timing information indicating the timing. ,

The objective lens control unit reverses the moving direction in the focus direction of the objective lens at a timing based on the timing information. Control device.

 [5] The timing information generation unit determines a predetermined time according to the in-focus position, generates timing information representing the predetermined time,

 5. The objective lens control device according to claim 4, wherein the objective lens control unit reverses a movement direction of the objective lens in a focus direction after the predetermined time after receiving the timing information.

[6] An apparatus that includes an objective lens, irradiates light onto the optical recording medium through the objective lens in addition to a light source, and receives the return light. By controlling the position of the objective lens, In an objective lens control device that controls the focus of irradiated light,

 An in-focus position detecting step of detecting a position of an objective lens at which the light emitted from the light source is in focus on the optical recording medium by detecting a predetermined signal from the received return light;

 And a reversing step of reversing the moving direction of the objective lens in the focus direction.

[7] An apparatus that includes an objective lens, irradiates light onto the optical recording medium through the objective lens in addition to the light source, and receives the return light. By controlling the position of the objective lens, In an objective lens control device that controls the focus of irradiated light,

 An in-focus position detecting step of detecting a position of an objective lens at which the light emitted from the light source is in focus on the optical recording medium by detecting a predetermined signal from the received return light;

 A timing information generating step for determining a timing for reversing the moving direction in the focus direction of the objective lens according to the focus position detected by the focus position detection unit, and generating timing information representing the timing;

 An inversion step of inverting the moving direction of the objective lens in the focus direction at a timing based on the timing information;

 An objective lens control method comprising:

[8] An apparatus that includes an objective lens, irradiates light onto the optical recording medium through the objective lens in addition to the light source, and receives the return light. By controlling the position of the objective lens, Irradiation In a program that causes a computer to execute an objective lens control method for controlling the focus of light to be emitted,

 An in-focus position detecting step of detecting a position of an objective lens at which the light emitted from the light source is in focus on the optical recording medium by detecting a predetermined signal from the received return light;

 A reversing step of reversing the moving direction of the objective lens in the focus direction, and causing the computer to execute the program.

 An apparatus that includes an objective lens, irradiates light onto the optical recording medium via the objective lens in addition to the light source, and receives the return light. The irradiation is performed by controlling the position of the objective lens. In a program that causes a computer to execute an objective lens control method for controlling the focus of light,

 An in-focus position detecting step of detecting a position of an objective lens at which the light emitted from the light source is in focus on the optical recording medium by detecting a predetermined signal from the received return light;

 A timing information generating step for determining a timing for reversing the moving direction in the focus direction of the objective lens according to the focus position detected by the focus position detection unit, and generating timing information representing the timing;

 An inversion step of inverting the moving direction of the objective lens in the focus direction at a timing based on the timing information;

 A program that causes a computer to execute.