Patent Application
20060104169
This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-322734, filed Nov. 5, 2004, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to a technique of recording/reproducing information on an optical disk, and more particularly to an optical disk drive capable of recording/reproducing information on a surface or a region of an optical disk, where no track information is present, an information processing apparatus, and a control method for the optical disk drive.
2. Description of the Related Art
Jpn. Pat. Appln. KOKAI Publication No. 2002-203321, for instance, discloses a prior-art technique of recording/reproducing information on a surface of an optical disk, where no track information is present, for example, on a label surface of an optical disk. According to this technique, when recording/reproduction is effected on the label surface of the optical disk, where no track information is present, a linear scale that uses a feed screw is employed in order to detect the position of a pickup lens (see, e.g. Jpn. Pat. Appln. KOKAI Publication No. 2002-203321).
In this technique, the linear scale using the feed screw is employed to detect the position of the pickup. Specifically, the position of the pickup is detected on the basis of the amount of driving of the feed motor. In this method, however, if an intended amount of movement of the pickup is not obtained relative to the amount of driving of the feed motor, for example, if the feed screw idly rotates, the exact position of the pickup cannot be detected.
The object of the present invention is to provide an optical disk drive capable of precisely detecting and controlling the position of a pickup when information is recorded/reproduced on a surface or a region of an optical disk, where no track information is present, an information processing apparatus, and a control method for the optical disk drive.
In order to achieve the object, the present invention provides an optical disk drive comprising: a pickup that radiates a laser beam to a surface or a region of an optical disk, where no track information is present, thereby recording and/or reproducing predetermined information on the surface or the region, and that is movable in a radial direction of the optical disk; sensor means for detecting movement and/or a position of the pickup, the sensor means being organically disposed on the pickup and/or a path of movement of the pickup; and control means for controlling the position of the pickup on the basis of information relating to the movement and/or position of the pickup that is detected by the sensor means. The invention also provides an optical disk drive that includes, as sensor means, a light emitting portion that moves following movement of the pickup; an encoder plate that varies and reflects or passes the light, which is emitted from the light emitting portion; and a light receiving portion that receives the light from the encoder plate. The invention also provides an optical disk drive wherein the control means controls first drive means for moving the pickup and/or second drive means for moving an objective lens of the pickup, on the basis of position difference information, which is obtained by comparing position information that is detected by the sensor means with target position information. The invention also provides an information processing apparatus including memory means for storing, as the predetermined information, image information that is to be recorded by the pickup on, for example, a label surface; and instruction means for supplying the image information from the memory means to the optical disk drive, and instructing the optical disk drive to record the image information on the optical disk (e.g. on the label surface). Therefore, the position of the pickup can precisely be detected and controlled even on a surface or a region of an optical disk, where no track information is present.
Using the present invention, the position of the pickup can precisely be detected and controlled when information is to be recorded/reproduced on a surface or a region of an optical disk, where no track information is present.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.
Embodiments of the present invention will now be described with reference to the accompanying drawings.
The optical disk drive 12, as shown in
The drawer unit 16, as shown in
The mechanism unit 18, as shown in
The encoder plate 32 is attached to the back surface of the cover member 20 by means of an adhesive such as an adhesion bond, such that the encoder plate 32 extends along the path of movement of the pickup unit 28 and is opposed to the light emitting portion and light receiving portion of the position sensor 26. Alternatively, the encoder plate 32 may be directly drawn on the back surface of the cover member 20 by means of, e.g. etching. Since the encoder plate 28 is attached to the cover member 20 that is provided so as not to block a laser beam from the pickup unit 28, the emission light from the position sensor 26 does not interfere with the laser beam from the pickup unit 28, and the recording/reproducing operation is not adversely affected.
The encoder plate 32 is continuously formed from a position, which is more radially inward than a position where light from the position sensor 26 is reflected when the pickup unit 28 is moved to the radially innermost side, to a position, which is more radially outward than a position where light from the position sensor 26 is reflected when the pickup unit 28 is moved to the radially outermost side. Thereby, the position detection signal can continuously be output even while the pickup unit 28 is continuously being moved over the entire range of movement.
The encoder plate 32 has a bar-code shape, for example, as shown in
The position sensor 26, as shown in
Flexible cables 40 and 42 are connected to the pickup unit 28 and position sensor 26.
The embodiment of the sensor means, which includes the reflective encoder plate, has been described. In the sensor means, light emitted from the position sensor 26 is varied by the encoder plate 32. A reflected component of the light is received by the position sensor 26, and the position of the pickup unit 28 is detected. Alternatively, a dedicated position sensor for light emission and a dedicated position sensor for light reception may be provided on both sides of a transmissive encoder plate. An embodiment that uses a transmissive encoder plate is described below.
In this embodiment, unlike the above-described embodiment using the reflective encoder plate 32, a transmission-type position sensor 48 is disposed so as to sandwich a transmissive encoder plate 46, on the side where a driving force is applied to the pickup unit 28 provided in the half-height type disk drive unit 52, that is, on the side of the main shaft 23 that is the drive shaft, where the lead screw 27 is provided. The transmission-type position sensor 48 comprises two independent sensors, that is, a dedicated light emission portion and a dedicated light reception portion. For example, light is emitted from the light emitting portion in a direction indicated by the arrow. The light passes through the transmissive encoder plate 46 and is received by the light receiving portion. The transmissive encoder plate 46 comprises two regions, like the reflective encoder plate 32 shown in
As has been described above, in the present embodiment, the position sensor 26, 48 and the encoder plate 32, 46 are used as the sensor means for detecting the movement and/or position of the pickup. These components are organically arranged (specifically, the position sensor 26, 48 is formed integral with the pickup, and the encoder plate 32, 46 is provided along the path of movement of the pickup). Unlike the technique of detecting the movement of the pickup on the basis of the rotation of the feed motor, the movement and position of the pickup unit 28 can directly be detected. Therefore, the precision in detection is enhanced.
Next, the structure of the pickup unit 28 of the optical disk drive is described. In particular, a description is given here of the structure with which the optical disk drive executes recording/reproduction of information, such as drawing of image information, on an area of an optical disk, which is not a normal recording/reproduction area, that is, on a label surface with no track information or an area of an information surface that is located outside a data recording area.
The spindle motor 22 is mounted on a chassis 61 of the optical disk drive. An optical disk 60 is secured to the spindle motor 22. Information write/reproduction on the optical disk 60 is executed by the pickup unit 28. A pickup main body 65 of the pickup unit 28, which is supported on a guide shaft 67, receives a driving force of the motor 66 via a lead screw 68 so that the pickup unit 28 can move in the right-and-left direction in
Light is made incident on the encoder plate 62 and a variation in light, such as reflection or transmission, is detected by the position sensor 63. Thereby, the position of the pickup main body 65 is determined. A position signal relating to the pickup main body 65, which is detected by the position sensor 63, is delivered to a position difference signal generating unit 82. The position difference signal generating unit 82 calculates a position difference signal that is indicative of a difference of position or position error relative to a target control position, on the basis of the received position signal and a target position signal (N) that is received from a controller 80 and is indicative of target position information of the pickup main body 65. The position difference signal that is calculated by the position difference signal generating unit 82 is delivered to a control unit 81. Based on the position difference signal, the control unit 81 drives, where necessary, the feed motor 66 via a motor driver 83 and controls the position of the pickup main body 65. Further, the control unit 81, drives, where necessary, the lens actuator 71 via a tracking/focus driver 84, and control the radial position of the objective lens 72. Thereby, the laser spot 73 is controlled and brought to a target point on the optical disk 60.
As mentioned above, either or both of the control of the laser spot 73 using the feed motor 66 and the control of the laser spot 73 using the lens actuator 71 are executed, depending on necessary. For example, when there is a distance, namely position difference y, between a target position x of the laser spot 73 and the center of the pickup main body 65 (approximately at the center of the radial movable range of the objective lens), as shown in
In the embodiment shown in
In the above-described embodiment, a feedback control is executed to control the pickup main body 65. Specifically, the controller 80 drives and controls the feed motor 66 and lens actuator 71 via the control unit 81. Alternatively, a structure as shown in
The controller 80 directly controls the motor driver 83 without intervention of the control unit 81 and drives the feed motor 66. On the other hand, the lens actuator 71 is driven by the control unit 81 via the tracking/focus driver 84. The controller 80 sends, as a target value, a target position signal to the feed motor 66 via the motor driver 83, and does not execute a feedback control. In this case, if a stepping motor is adopted as the feed motor 66, the feed motor 66 is moved to the vicinity of the target position only if the controller 80 sends, as a target position signal, a number of pulses that corresponds to a target amount of movement. Thereafter, like the above-described embodiment, the control unit 81 calculates a position difference, relative to the target position, and drives and controls the lens actuator 71.
In an embodiment shown in
In the case of adopting a stepping motor for the feed motor 66, the precision in position of the pickup main body 65 is maximized when a two-phase drive control is executed. In the case where the pickup main body 65 is controlled by two-phase driving, the lens actuator 71 is used if the laser spot 73 is to be moved by an amount that is smaller than the movement amount of the pickup main body 65. With use of both the feed motor 66 and lens actuator 71, the laser spot 73 can exactly be moved to the target position.
In the above-described embodiment, if the gain is adjusted so that the position difference of the pickup main body 65 may coincide completely with the movement amount of the objective lens 72 by the lens actuator 71, the laser spot 73, theoretically, remains at the target position. In fact, however, a delay occurs in the responsivity of the lens actuator 71 relative to the instruction voltage. In addition, if the position control of the pickup main body 65 is always functioning, vibration may occur due to the movement of the pickup main body 65. It is desirable, therefore, to stop and hold the position control of the pickup main body 65 when the position difference has decreased to a predetermined value or less.
If the position difference is large, there may be a case where an excessive current flows in the lens actuator 71. It is thus necessary to set an upper limit to the current that flows in the lens actuator 71.
Next, a description is given of a method of detecting the position of the pickup main body 65 by means of the position sensor 63 and calculating the position difference. In the method of calculating the position difference according to this embodiment, the precision is improved up to a 1/256 resolution with respect to a white-and-black pair on the encoder plate 62.
The output signals from the gain adjusters 4A and 4B are input to detectors 6A and 6B. In addition, a reference value is input from the controller 80 to the detectors 6A and 6B. The reference value can be changed by a program. The detectors 6A and 6B compare the input signals from the gain adjusters 4A and 4B and the reference value, and output absolute values of the differences between the input signals and the reference value. The detected signal has a waveform 180. Results of comparison in magnitude with the reference value are delivered to a decoder 75.
Subsequently, a magnitude comparator 88 compares the magnitudes of signals from the detectors 6A and 6B. A comparison result is sent to the decoder 75 and a divider 90. The divider 90 receives outputs from the detectors 6A and 6B and executes a division arithmetic operation of “small value÷large value”. Thus, the result of the arithmetic operation is always less than 1.
The decoder 75 divides a pair of white-and-black portions of the encoder plate 62 by 8, on the basis of the three input information (the signals from the detectors 6A and 6B and the comparison result data from the magnitude comparator 88). An output from the decoder 75 is delivered to a counter 150. When the sensor position shifts to a different pair of white-and-black portions, the count value is incremented or decremented. The decoder 75 outputs the result to a subtracter 120. The arithmetic division result from the divider 90 is linearly corrected by a lookup table 100 and the corrected value is output to the subtracter 120.
The controller 80 sends an instruction, which provides target position information, to a register 110 that stores target position information. Upon receiving the instruction, the register 110 outputs the target position information to the subtracter 120.
The subtracter 120 receives the output from the lookup table 100, which linearly corrects the division result of the divider 90, the count value from the counter 150, and the target position information from the register 110, and executes a subtraction process for calculating a difference between the current position and the target position. The subtraction result is output to a limiter 130. When the output from the subtracter 120 exceeds a predetermined value, the limiter 130 outputs a predetermined value in place of the output of the subtracter 120. The output from the limiter 130 is input to a converter 140, and converted to a PWM wave signal. The PWM wave signal is output as position difference information. This position difference information has a voltage vs. position difference characteristic with a waveform 190.
Next, the position detection by the position sensor 63 and encoder plate 62, which are used in the present embodiment, is described in greater detail.
Next, a method of detecting the sensor position with higher precision on the basis of a single pair of white-and-black portions is described in detail. Normally, the sensor position is detectable only with a precision corresponding to the white-and-black parts of the encoder plate 62. However, if the two outputs obtained from the position sensor 63 are compared with a reference voltage and a truth table, as shown in
For the purpose of description, symbols Ph0 to Ph3 are assigned to the respective phase states on the truth table. When the state Ph3 transits to the state Ph0, the count value in a pair of up/down counters is incremented. When the state Ph0 transits to the state Ph3, the count value is decremented. Thereby, it becomes possible to detect the number of white-and-black pairs, that is, a distance, over which the position sensor has moved in the (+) direction or in the (−) direction.
Next, a method of further enhancing the precision of detection of the sensor position is described.
The voltages of the signal A-ch and signal B-ch are detected with respect to a reference voltage that is sent from the controller 80, and the comparative relationship in magnitude between the signal A-ch, B-ch and the reference voltage is detected. The comparison results are added to the truth table. Hence, as shown in
In this embodiment, the sensor position can be detected with still higher precision. That is, the sensor position can be detected with a precision of 1/256 of the single white-and-black pair.
The outputs from the position sensor 63 are digitized by the A/D converters 3A and 3B each having 9-bit precision. The truth tables shown in
Referring to the truth table shown in
On the other hand, a calculation, |Bch output|÷|Ach output|, is executed in the range in which |Ach output|>|Bch output| is true.
This calculation is equivalent to Y=X÷(−X+1), where 0<=X<=0.5, in the case of a triangular wave input. The calculation is equivalent to Y=COS X÷SIN X=TAN X, where COS X<=SIN X, in the case of SIN and COS wave inputs, and curves with values 0 and 1 are obtained. The precision is 8 bits. The calculation results are shown in
The division operation result of the divider 90 is linearly corrected by the lookup table 100. In an example shown in
In ranges with mark ◯ in the truth table of
The division result has 5-bit precision and the truth tables of FIGS. 29 to 33 have 3-bit precision (precision of ⅛ of the single white-and-black pair). With 8-bit precision in total (precision of 1/56 of the single white-and-black pair), the position of the position sensor 63 can be detected.
If a “target position” is set for the above-described result of “current position detection”, finer “position difference information” can be generated. In this embodiment, the difference between the current position and the target position is output by PWM.
A terminal A is supplied with a signal that is indicative of a ± sign of a position difference. A terminal B is supplied with an absolute value of the position difference.
Specifically, when the absolute value of the position difference is 0, a waveform with a time ratio of L:H=0:256 is supplied.
When the absolute value of the position difference is 1, a waveform with a time ratio of L:H=1:255 is supplied.
When the absolute value of the position difference is 2, a waveform with a time ratio of L:H=2:254 is supplied.
When the absolute value of the position difference is 254, a waveform with a time ratio of L:H=254:2 is supplied.
When the absolute value of the position difference is 255, a waveform with a time ratio of L:H=255:1 is supplied.
A terminal C is supplied with a reference voltage.
A output waveform from a terminal D is as shown in
As has been described above, according to the embodiment of the present invention, the position of the pickup can be precisely detected and controlled when information is recorded/reproduced on a surface or a region of an optical disk, where no tracks are present. In addition, the position control of the pickup can be executed on the basis of the output of the position sensor, no matter which of the position control of the pickup main body by means of the feed motor and the position control of the objective lens by means of the lens actuator is executed. Thus, high-precision position control can be realized.
In the embodiment shown in
The following advantageous effects can thus be obtained. In the case of the preceding embodiment where the pickup unit 28 is driven using the main shaft 23 as the guide, a play (rattling) occurs between the main shaft 23 and a bearing metal of the pickup unit 28. The play increases as the pickup unit 28 is repeatedly moved. The effect of the play of the shaft appears on the sub-shaft 25 side where the degree of swing becomes large, with the main shaft functioning as the supporting point. On the other hand, the function of the position sensor is to detect the position where a laser beam is made incident on the optical disk through the objective lens. Thus, a detection error tends to easily occur as the distance between the position sensor and the objective lens increases. For example, in the case where the diameter of the main shaft is 2.992 mm (actual measurement value), the diameter of the bearing metal of the pickup unit is 3.010 mm, the length of the bearing metal is 19.4 mm and the distance between the center of the objective lens and the position sensor on the sub-shaft side is 20.17 mm, an error in output of the position sensor in relation to the position of the objective lens is (3.010−2.992)/19.4·20.17=18.7 μm. It is likely that an output error of 18.7 μm at maximum may occur. By disposing the position sensor near the objective lens and making the position sensor move substantially along the path of movement of the objective lens, the effect of play (rattling) of the shaft can be reduced.
The present invention is not limited to the above-described embodiments. At the stage of practicing the invention, various modifications and alterations may be made without departing from the spirit of the invention. For example, not only the optical sensor but also a magnetic sensor or any other type of sensor is usable as the sensor means. Structural elements disclosed in the embodiments may properly be combined, and various inventions can be made. For example, some structural elements may be omitted from the embodiments. Moreover, structural elements in different embodiments may properly be combined.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-322734 | Nov 2004 | JP | national |
