JPH06131671A - Optical disk device - Google Patents

Abstract

PURPOSE:To obtain an optical disk device capable of detecting the position of an optical pickup without being affected by disturbance. CONSTITUTION:An LED 24 is arranged in a fixed part opposing to a carriage 28, and the diffused light is converted into parallel light beams by a collimate lens 25, and the light beam is refracted on the moving axis A of the carriage 28 by a prism 26 so that light quantity incident on an optical sensor 27 is changed continuously according to the movement of the carriage 28. The output from the optical sensor 27 is outputted as a sensor output signal 30 through an amplifier 29. Thus, the position of the carriage 28 is detected continuously without being affected by the disturbance, etc., and a speed signal is obtained by differentiating an obtained position signal. Thus, the moving speed of the pickup at the time of access operation is detected precisely, and the stable and high speed access operation is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device which is connected to a computer or the like to record / reproduce data.

[0002]

2. Description of the Related Art Optical disks can record a large amount of information,
Further, it is a recording medium that can be repeatedly erased and reproduced. The optical disk device uses a laser beam to record and reproduce a signal on a track provided at a pitch of about 1 μm on the surface of the optical disk, and is highly accurate for accurately causing a laser spot to follow a target track on the surface of the optical disk. It requires a servo mechanism and a highly accurate access mechanism to move between tracks at high speed and stably.
Since an optical pickup generally has an order of magnitude larger mass than a magnetic head of a hard disk, it is difficult to shorten the track access time for moving the optical pickup to move an optical spot from one track to another track. However, in recent years, along with the downsizing of optical pickups and the development of control technology, the track access time, which has been a drawback of optical disk devices, is remarkably shortened.

In an optical disk device, a tracking servo operation for moving a light spot onto a target track and following the target track so as not to cause off-track and reproducing / recording a signal is rough for a rough movement. A two-stage servo system is generally used in which a linear motor or the like is used as an actuator and a coil actuator or the like is used as a fine actuator for minute movements. In this case, an optical pickup equipped with a light emitting element, a light receiving element, a beam splitter, and an objective lens is moved by a coarse actuator such as a linear motor, and only the objective lens is displaced within the optical unit by a fine actuator such as a coil actuator. Is common. A sensor in the optical pickup detects a signal proportional to the amount of deviation of the optical spot from the track center on the recording surface of the optical disc, that is, a tracking error signal, and controls the coarse / fine actuator so that the signal becomes zero. is doing.

Further, during data recording / reproduction, it becomes necessary to perform an access operation for moving the optical pickup from one track to another at high speed. If the number of tracks to move to the target track is large, set the target speed according to the number of tracks to the target track by a command, and give it as the target speed of the speed servo mechanism that moves the optical pickup unit in the radial direction of the optical disc. The moving speed of the optical pickup is controlled, the moving speed is reduced as the target track approaches, and when the number of remaining tracks becomes zero, the mode is switched to the tracking servo mode to complete the access operation to the target track.

The movable part of the optical pickup used in the conventional optical disk device as described above has a structure as shown in FIG. In FIG. 14, 1 is an objective lens, 2 is an objective lens actuator, 3 is a carriage, 4 is an objective lens position sensor, 5 is a linear motor, 6 is a shaft, and 7
Is an optical disk, and 8 is a flexible printed circuit board.

The operation of the movable part of the conventional optical pickup configured as described above will be described with reference to FIG. In the tracking servo mode, the objective lens actuator 2 and the linear motor 5 cause the light beam emitted from the objective lens 1 to follow the track on the optical disc 7. At this time, the linear motor 5 receives the signal from the objective lens position sensor 4 and is controlled so that the objective lens 1 is always in the neutral position.

When accelerating during the access operation, a current is passed through the objective lens actuator 2 to displace the objective lens 1 in the moving direction. Then, the linear motor 5 receives the signal from the objective lens position sensor 4, generates a driving force in the moving direction, and is accelerated. When decelerating, a current is applied to the objective lens actuator 2 in the direction opposite to that during acceleration, and the objective lens 1 is displaced in the direction opposite to the moving direction. Then,
The linear motor 5 receives the signal from the objective lens position sensor 4, generates a driving force in a direction opposite to the moving direction, and is decelerated.

FIG. 15 is a block diagram of an optical pickup access control device used in a conventional optical disk device. In FIG. 15, 9 is a controller and 10
Is an access control circuit, 11 is an actuator driver,
Reference numeral 12 is an objective lens actuator, 13 is an objective lens position sensor, 14 is a linear motor driver, 15 is a linear motor, 16 is a track crossing cycle detection circuit, 17 is a cycle-speed conversion circuit, 18 is a tracking error signal, and 19 is a tracking error signal.
Is a speed target value signal, and 20 is a speed detection signal.

The access operation of the conventional optical pickup configured as described above will be described with reference to FIG. First, during the access operation, the tracking servo is in the off state, and the tracking error signal 18 changes in a sine wave shape every time the track is crossed. The controller 9 counts the number of tracks traversed by the tracking error signal 18, and outputs a speed target value signal 19 stored in advance in a ROM or the like according to the number of remaining moving tracks up to the target track. The track crossing cycle detection circuit 16 binarizes the changing tracking error signal 18 to detect the cycle, and for example, by the cycle-speed conversion circuit 17 composed of a ROM or the like in which a value proportional to the reciprocal of the address is stored. Generates a speed detection signal. This is the same as using an encoder with a 1.6 μm pitch, which is the track pitch of the optical disk 7. The access control circuit 10 performs a differential operation on the speed target value signal 19 and the speed detection signal 20 and outputs it to the actuator driver 11 through a filter or the like. Then, the objective lens actuator 12 moves from the neutral position, and the linear motor 15 receives the output of the objective lens position sensor 13 resulting from the movement.

However, the above conventional configuration has the following problems. At the time of access operation, it is necessary to reduce the speed immediately before the optical pickup arrives at the target track, but in the method of measuring the cycle of the tracking error signal 18 as shown in FIG. 15 to detect the speed, two sampling points are used. Since the speed between is output after the end of sampling, the detection speed output with respect to the actual moving speed has a detection delay of about half a cycle, and therefore the error from the actual speed is slow if the moving speed is slow. The bigger it gets.
Therefore, the control tends to become unstable as the moving speed of the optical pickup becomes slower. In order to solve this problem, an encoder with a finer pitch may be provided, but it is not realistic to provide an encoder with a pitch of 1.6 μm or less.

Therefore, FIG. 16 shows a block diagram of an access control device in which the current of the linear motor is detected to improve the accuracy of speed detection as compared with the conventional example. In FIG. 16, 21 is a speed correction circuit, 22 is a linear motor current, 23 is a speed correction value signal, and other than that is common to FIG.

The access operation of the optical pickup configured as described above will be described with reference to FIG. Figure 1
In addition to the operation of the operation block diagram shown in FIG. 5, a speed correction circuit 21 for monitoring the linear motor current 22 and correcting the speed detection value from the cycle-speed conversion circuit 17 is added.
The speed correction circuit 21 is composed of an integrator, a sample hold circuit, an operational amplifier and the like. The moving speed is detected by integrating the linear motor current 22, and by the speed detection signal 20 from the cycle-speed conversion circuit 17,
Sequentially correct the moving speed. However, since the speed detection signal 20 has a detection delay, it is possible to correct only the speed of a half cycle before.

[0013]

That is, the above-mentioned conventional configuration has the following problems. In order to perform the access operation at high speed and stably, it is necessary to detect the moving speed of the optical pickup with high accuracy. Further, the movable portion of the optical pickup is provided with a flexible printed circuit board 8 as shown in FIG. 14 for connecting the signal line, and particularly when the linear motor 5 is elastically loaded, the access speed can be shortened. If the moving parts are made smaller and lighter,
It is a load that cannot be ignored. Further, disturbances such as vibration and inclination of the device directly cause an error, and even if the linear motor current 22 is simply integrated, an error with an actual moving speed becomes large, and various problems that an accurate speed cannot be detected. Had.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an optical disk device capable of stably and accurately detecting the speed when moving to a target track during access.

[0015]

In order to achieve this object, an optical disk device according to the present invention has a light source and a light source on a moving axis where a movable part of the optical pickup moves and a fixed part of the optical pickup is provided. An optical sensor that receives the light beam from the optical sensor and outputs a signal proportional to the amount of received light is arranged in the movable portion and the fixed portion so as to face each other.

[0016]

With the above arrangement, the present invention can continuously detect the position of the movable portion without being affected by disturbance.

[0017]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a position detecting device which is a part of an optical disk device according to the first embodiment of the present invention.
In FIG. 1, 24 is a light emitting diode (hereinafter abbreviated as LED), 25 is a collimator lens, 26 is a prism,
27 is an optical sensor, 28 is a carriage, 29 is an amplifier, 3
0 is a sensor output signal.

Next, the operation will be described with reference to FIG. The LED 24 is a fixed part, and the carriage 2 is a movable part.
8 are arranged to face each other. Since diffused light is emitted from the LED 24, it is converted into a parallel light beam by the collimator lens 25. Then, the light beam is refracted by the prism 26 so as to have an angle with respect to the movement axis A, so that when the carriage 28 moves in the direction of the arrow on the linear movement axis A, an optical sensor is used depending on the distance the carriage 28 moves. The amount of light incident on 27 is continuously changed. The output from the optical sensor 27 is amplified by the amplifier 29 and output as the sensor output signal 30. With such a configuration, a position signal proportional to the position of the carriage 28 as shown in FIG. 2 can be obtained. Although FIG. 1 shows an example in which the LED 24, which is a light source, is arranged in the fixed part and the optical sensor 27 is arranged in the movable part, the same position detector can be obtained even if the optical sensor 27 is arranged in the fixed part and the LED 24 is arranged in the movable part. Can be configured.

Although the parallel beam is used as the light beam in the above-mentioned first embodiment, a similar position detector can be realized by using a diffused beam.

(Embodiment 2) FIG. 3 is a block diagram showing a case where a diffused beam is used as a light beam of a position detecting device which is a part of an optical disk device according to a second embodiment of the present invention. Figure 3
31 is an analog / digital converter (hereinafter referred to as A / D
It is abbreviated as a converter. ), 32 are ROMs, 33 is a position signal (digital value), and other than that is common to FIG.

Next, the operation will be described with reference to FIG. Since diffused light is emitted from the LED 24, the amount of light incident on the optical sensor 27 is not proportional to the movement distance of the carriage 28, and the sensor output signal 30 cannot be used as it is as the position signal 33. Therefore, A / D converter 31 and ROM
32, the sensor output signal 30 is sent to the carriage 2 in advance.
The position signal 33 proportional to the moving distance can be obtained by performing conversion so that the position signal 33 is proportional to the moving distance. FIG. 4 is a diagram showing the relationship between the movement distance of the carriage 28 and the sensor output signal 30 of the optical disk device according to the second embodiment of the present invention, and FIG. 5 is the A / D converter of the optical disk device according to the second embodiment of the present invention. 31 is a diagram showing the relationship between the movement distance of the carriage 28 and the position signal 33, which is obtained by conversion using the ROM 31 and ROM 32. In general, the intensity of light at a location away from the light source is inversely proportional to the square of the distance, so that a hyperbolic sensor output signal 30 as shown in FIG. 4 is obtained. Then, by converting the sensor output signal 30 by the A / D converter 31 and the ROM 32, a position signal 33 proportional to the movement distance of the carriage 28 as shown in FIG. 5 can be obtained. Thus, the A / D of FIG.
By using the converter 31 and the signal conversion means such as the ROM 32, the position signal 33 can be easily obtained even with respect to the nonlinear sensor output signal 30 of the optical sensor 27 that occurs when a light source that emits diffused light is used. Can be generated.

(Third Embodiment) FIG. 6 is a block diagram of a position detecting device which is a part of an optical disk device according to a third embodiment of the present invention. In FIG. 6, 24a is the first LED, 24
b is a second LED, 27a is a first photosensor, 27b is a second photosensor, 28 is a carriage, 29a is a first amplifier, 29b is a second amplifier, 34 is a differential amplifier, 35
Is a position signal, and 36a and 36b are sensor output signals.

Next, the operation will be described with reference to FIG. An optical system including the first LED 24a, the second LED 24b, the first optical sensor 27a, and the second optical sensor 27b is symmetrically arranged before and after the moving direction of the carriage 28 that is the movable portion, and the respective sensor outputs are provided. Signals 36a, 36b
The differential signal is generated by the differential amplifier 34, and is output as the position signal 35. The relationship between the movement distance of the carriage 28 and the sensor output signals 36a and 36b is shown in FIG. 7, and the relationship between the movement distance of the carriage 28 and the position signal 35 is shown in FIG. Since diffused light is emitted from the first LED 24a and the second LED 24b, the sensor output signals 36a and 36b are approximately the same as those of the first optical sensor 27a or the second optical sensor 27.
It changes as shown in FIG. 7 in inverse proportion to the square of the distance between b and the first LED 24a or the second LED 24b.
That is, as it is, the movement distance of the carriage 28 and the sensor output signals 36a and 36b are not proportional and cannot be used as position signals. Therefore, the sensor output signals 36a and 36b
FIG. 8 shows the result obtained by taking the difference. As shown in FIG. 8, although the linearity is not good, the first optical sensor 27
It can be seen that the output position signal 35 changes substantially linearly with respect to the moving distance of the carriage 28, as compared with the output signals of the a and second optical sensors 27b respectively.

(Embodiment 4) Next, a method for improving the non-linearity of the output of the position signal 35 shown in FIG. 8 will be described. FIG. 9 is a block diagram of a position detecting device which is a part of the optical disk device according to the fourth embodiment of the present invention. In FIG. 9, 24 is an LED, 27 is an optical sensor, and 37 is a lens. As shown in FIG. 9, the lens 37 is set to the LED 2 so that the light spot diameter on the optical sensor 27 changes according to the moving distance of the movable portion.
4 and the optical sensor 27. FIG. 10 shows the relationship between the light receiving surface of the optical sensor 27 of the position detecting device which is a part of the optical disc device and the light spot. 27c is the light receiving surface of the optical sensor 27, 38 is the minimum diameter of the light spot, and 39 is the maximum diameter of the light spot. As shown in FIG. 10, the light receiving surface 27c has a rectangular shape, and its short side has a minimum diameter of the light spot of 3 mm.
The size is 8 or less, and the long side thereof has a size of the maximum diameter of the light spot of 39 or more. Originally, the light intensity of the diffused light is inversely proportional to the square of the distance from the light source, but with such a configuration, the light spot diameter and the incident area of the light on the optical sensor 27 are substantially proportional to each other. The sensor output signal is a signal that is inversely proportional to the distance from the light source. When such an optical system is applied to the configuration shown in FIG. 6, two sensor output signals as shown in FIG. 11 are obtained. Each sensor output signal is carriage 2
Since it is inversely proportional to the moving distance of 8, the sensor output signals 36a and 36b that are inversely proportional to the square of the distance as shown in FIG. FIG. 12 shows the result of taking the difference between the two sensor output signals shown in FIG.
It can be seen that the linearity is considerably improved as compared with the position signal 35 shown in FIG.

FIG. 13 is a block diagram when the position detecting device, which is a part of the optical disk device in the embodiment of the present invention described so far, is applied to the access control device of the optical pickup. In FIG. 13, 9 is a controller,
Reference numeral 10 is an access control circuit, 11 is an actuator driver, 12 is an objective lens actuator, 13 is an objective lens position sensor, 14 is a linear motor driver, 15 is a linear motor, 16 is a track crossing cycle detection circuit, and 17 is a cycle-speed conversion circuit. , 18 are tracking error signals,
19 is a speed target value signal, 20 is a speed detection signal, 23 is a speed correction value signal, 40 is a position detector, 41 is a differentiation circuit, 4
Reference numeral 2 is a speed correction circuit, and 43 is a speed signal.

Next, the operation will be described. First, during the access operation, the tracking servo is in the off state, and the tracking error signal 18 changes in a sine wave shape every time the track is crossed. The controller 9 counts the tracks traversed by the tracking error signal 18, and the ROM is preliminarily read according to the number of remaining moving tracks up to the target track.
And outputs the target speed value signal 19 stored in, for example. The track crossing cycle detection circuit 16 binarizes the changing tracking error signal 18 to detect the cycle, and for example, by the cycle-speed conversion circuit 17 composed of a ROM or the like in which a value proportional to the reciprocal of the address is stored. The speed detection signal 20 is generated. On the other hand, the position detector 40 continuously detects the position of the carriage 28. This position signal is optically detected and is not affected by external force, vibration or the like. The speed signal 43 of the carriage 28 can be detected by differentiating the output of the position detector 40 by the differentiating circuit 41. The speed correction circuit 42 corrects the speed signal 43 from the differentiating circuit 41 with the speed detection value 20 from the cycle-speed conversion circuit 17 to generate the speed correction value signal 23. The speed correction circuit 42 is composed of a sample hold circuit, an operational amplifier, etc., detects the speed signal 43 from the differentiating circuit 41, and sequentially corrects the speed signal 43 by the speed detection signal 20 from the cycle-speed conversion circuit 17. To do. However, since the speed detection signal 20 has a detection delay, it is possible to correct only the speed of a half cycle before. Thereafter, the same operation as in the conventional example is performed.

[0028]

As described above, according to the present invention, the light source and the light beam from the light source are received on the moving axis where the movable portion of the optical pickup moves and the fixed portion of the optical pickup is provided, and the received light amount is changed. By configuring the optical sensor that outputs a proportional signal and the movable portion and the fixed portion so as to face each other, the position of the movable portion can be continuously detected without being affected by disturbance. , It is possible to realize a speed detection device for a movable part that is not affected by elastic load due to a flexible printed circuit board connected to the movable part or by disturbance such as vibration or tilt of the device. It is possible to accurately detect the speed at which the unit moves to the target track, and as a result, it is possible to provide an excellent optical disk device capable of stable and high-speed access operation.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a position detection device which is a part of an optical disc device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the position of the carriage and the position signal of the optical disk device according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram when a diffused beam is used as a light beam of a position detection device which is a part of an optical disc device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a moving distance of a carriage and a sensor output signal of an optical disk device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the movement distance of the carriage and the position signal of the optical disk device in the second embodiment of the present invention.

FIG. 6 is a configuration diagram of a position detection device which is a part of an optical disc device according to a third embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a movement distance of a carriage and a sensor output signal of an optical disk device according to a third embodiment of the present invention.

FIG. 8 is a diagram showing the relationship between the movement distance of the carriage and the position signal of the optical disk device in the third embodiment of the present invention.

FIG. 9 is a configuration diagram of a position detection device which is a part of an optical disc device according to a fourth embodiment of the present invention.

FIG. 10 is a diagram showing the relationship between the light receiving surface of the optical sensor and the light spot of the position detecting device which is a part of the optical disc device according to the fourth embodiment of the present invention.

FIG. 11 is a diagram showing the relationship between the movement distance of the carriage and the sensor output signal of the optical disk device in the fourth embodiment of the present invention.

FIG. 12 is a diagram showing a relationship between a carriage movement distance and a position signal of an optical disk device according to a fourth embodiment of the present invention.

FIG. 13 is a block diagram when the position detection device, which is a part of the optical disk device according to the embodiment of the present invention, is applied to an access control device of an optical pickup.

FIG. 14 is a configuration diagram of a movable portion of an optical pickup used in a conventional optical disc device.

FIG. 15 is a block diagram of an access control device for an optical pickup used in a conventional optical disc device.

FIG. 16 is a block diagram of an access control device that improves the speed detection accuracy by detecting the current of a linear motor of a conventional optical disk device.

[Explanation of symbols]

 24 LED 25 Collimator Lens 26 Prism 27 Optical Sensor 28 Carriage 29 Amplifier 34 Differential Amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shingo Sakata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A light source and a light beam from the light source are received and received by a movable portion of the optical pickup which moves on a linear movement axis and a fixed portion of the optical pickup which is provided on the movement axis. An optical disk device, wherein an optical sensor that outputs a signal proportional to a light amount is arranged on the movable portion and the fixed portion so as to face each other on the moving axis. 2. A conversion means for converting the diffused light emitted from the light source into a parallel light beam, and a refraction means for refracting the light beam at an angle with respect to the moving axis. The optical disk device according to claim 1. 3. The optical disk device according to claim 1, wherein the light source emits diffused light, and the light source further comprises conversion means for converting an output signal of the optical sensor into a position signal. 4. A means for arranging a pair of the light source and the optical sensor symmetrically in the front-rear direction with respect to a moving direction of the movable portion, and performing a differential calculation of outputs of the respective optical sensors. The optical disk device according to claim 1, which has. 5. The light source emits diffused light, and the optical sensor has a shape in which a long side is longer than a maximum value of a light spot diameter and a short side is shorter than a minimum value of the light spot diameter. The optical disk device according to claim 4.