JP2863165B2 - Tracking device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control device in a recording / reproducing apparatus for a disk-shaped record carrier (hereinafter, referred to as a disk), and more particularly, to a speed of searching information from a disk by an optical head. Is to speed up. 2. Description of the Related Art In general, a kind of address signal called an address signal is recorded on a disc to search a desired portion at high speed, and is used for a search operation. Conventionally, a search was performed by rapidly moving an optical head for reading an address signal from a disk by a linear motor. (JP-A-58-182171). First, FIG. 5 shows a configuration diagram showing a conventional search method. Reference numeral 1 denotes a disk, B denotes an optical head, and the optical head includes a laser, a photodetector, and a tracking driving device. This optical head B
Is controlled in the radial direction of the disk by a linear motor A controlled by a linear motor control device D. 4 is a core, 5 is a magnet, and the drive unit 6 moves the optical head B. C is a tracking servo device, and E is a control device. Problems to be Solved by the Invention In such a conventional apparatus, as described above, the search is performed by moving the optical head at a high speed by the linear motor. On the other hand, the optical head has an objective lens, a laser, a tracking drive, etc., and weighs about 50 to 100 grams. To move at high speed, the thrust of the linear motor must be set large. Did not. As a result, the weight and size of the entire apparatus are increased, and the apparatus is expensive. Means for Solving the Problems According to the present invention, an optical signal is used to record and reproduce information signals on a recording track having a recording track, and the recording track can be tracked over the entire recording carrier. When the tracking servo system of the optical scanning device is pulled into the recording track, the polarity and the DC level of the tracking error signal are detected by the tracking error signal of the recording track, and the tracking servo system is controlled within the specified range of the polarity and the DC level. The operation is started. With this configuration, in the present invention, the tracking servo system is controlled by a tracking error signal obtained by a track on the disk. However, when the tracking servo system cannot operate normally due to disturbance, the position of the movable optical system is changed. It operates according to the position detection signal shown. Thus, a stable operation of the tracking servo system can be guaranteed even when a movable optical system that can follow from the inner circumference to the outer circumference of the disk is used. Further, even when the tracking servo system is turned on, a range in which the tracking servo system can be stably pulled in can be detected from the tracking error signal, and a period during which a quick pull-in operation is performed can be set. This makes it possible to commercialize a separation optical system capable of performing a high-speed search. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this apparatus, the optical head is separated into a movable optical system and a fixed optical system which are optical scanning devices, and the role of a conventional linear motor servo system is combined with the tracking servo system. For this reason, conventionally, the tracking servo system was first operated, and then the linear motor servo was operated.However, in the present device, the tracking servo system has the function of the linear motor servo system. It is necessary to extract the timing for operating the tracking servo system from the tracking error signal. Next, FIG. 1 shows a principle diagram of the present apparatus. In FIG. 1, reference numeral 50 denotes a disk; 51, a motor for rotating the disk; 52, a movable optical system as an optical scanning device; a mirror 55; an objective lens 54; and the objective lens 54, which follows the surface deflection direction of the disk 50. And a tracking drive 56 so that the disk 50 can be moved in the radial direction. Reference numeral 60 denotes a fixed optical system, in which a light beam emitted from a laser 57 is converted into parallel light by a lens 58, and is converged on a recording surface of the disk 50 by an objective lens 54 via a beam splitter 59 and a mirror 55. The reflected light passes through an objective lens 54, a mirror 55, and a beam splitter 59, passes through a lens 61, and is separated and supplied to photodetectors 63 and 64 by a beam splitter 62. The photodetector 63 detects a focus error signal, and the photodetector 64 detects a tracking error signal. Here, the description of the focus system will be omitted. The tracking error signal detected by the photodetector 64 is guided to a differential amplifier 65, and passes through an equalizer 66 and a switch 68 to form a tracking servo system that drives and controls the tracking drive device 56 with the output of the drive amplifier 67. FIG. 2 shows the relationship between the light spot 71 focused on the disk 750 by the objective lens 54 and the track 70 formed on the recording surface of the disk 50, and the tracking error signal 73 (differential amplification) detected at that time. Output of the container 65). Due to the eccentricity of the disc 50, the light spot 71 and the track 70
, And as a result, a tracking error signal 73 is obtained. Since the tracking error signal 73 has a positive slope in the section A and a negative slope in the section B, when a negative feedback is formed in the section A with respect to the tracking servo system, the feedback becomes positive in the section B. The tracking servo system oscillates. When the tracking servo system also serves as a linear motor servo system as in the present apparatus, the timing for operating the tracking servo system is particularly important, such as the section B of the tracking error signal 73 and the zero point of the DC signal. When the tracking servo system is operated at the time when the displacement is greatly deviated from 7, the movable optical element 52 in FIG. 1 runs out of control and does not operate normally. Therefore, in this apparatus, the timing for operating the tracking servo system is determined by the polarity of the tracking signal 73 and the DC
The voltage is detected and determined, and the switch 68 shown in FIG. 1 is opened and closed. That is, during the period T in FIG.
Close 68. Thereby, the tracking servo system always operates normally. Further, in the present apparatus, the position of the movable optical system 52 is always detected to prevent the movable optical system from running away even if there is an abnormality in the tracking servo system. FIG. 3 shows a specific configuration of one embodiment of the present invention. In FIG. 3, reference numeral 100 denotes a disk 101, a movable optical system, and 102, a solid optical system, and the configuration is the same as that in FIG. Reference numeral 117 denotes a position detector for detecting the position of the movable optical system 101. For example, an optical position detector can be used. A tracking error detector 103 is converted into an electric signal by a differential amplifier 104. Reference numeral 105 denotes a switch, which is normally connected to the side of the 105-1.
It is switched by the input of 05-3. 106 is an equalizer that optimizes the response of the tracking servo system. Reference numeral 107 denotes a switch, which opens and closes in response to the input of a switching signal 107-1, and activates the tracking servo system at the closed position. 108
Is a drive amplifier, which moves the movable optical system 101 in the radial direction of the disk 100. The structure of the movable optical system may be an ordinary one. Reference numeral 109 denotes a window comparator, which detects a pulse signal when the output of the differential amplifier 104 exceeds a specified range, and
Enter 110. When a predetermined number of pulses are input, the output state of the counter 110 changes to a high level. With this function, it can be determined whether the tracking servo system is operating normally. That is, when the output of the counter 110 becomes high level, it is determined that the tracking servo is not normal. The output of the counter 110 is held by the latch circuit 111,
The signal is input to the delay circuit 112. Reference numerals 113 and 114 denote comparator circuits which change the levels indicated by + a and -b in FIG.
The pulse is generated from -1 (R1, R2, R3) and a pulse is output when the tracking error signal passes the level of + a, -b. Reference numeral 115 denotes an order discriminator, which discriminates the order of the output pulses of the comparators 113 and 114, thereby detecting the section indicated by T in FIG. The output of the order discriminator 115 is a tracking servo operation command signal (116-
When 1) is input, it is held. The output of the position detector 117 is input to the position detector 118,
The DC voltage is converted into a DC voltage proportional to the distance from the innermost periphery of the disk 100 of the movable optical system 101. The output of the position detection 118 is input to the offset removing device 124 and is converted from the differential amplifier 119 into a voltage change centered on the DC zero potential. That is, the position detection position 1 input to the differential amplifier 119
The output voltage of 18 is input to the comparator 120 and
2 and outputs a pulse to the counter 121 via the flip-flop 123 until the difference becomes 0,
Make this work. The output of counter 121 is a D / A converter
The voltage is input to 122, converted to a DC voltage indicating the count number of the counter 121, and input to the differential amplifier 119. Differential amplifier 1
As the output of 19, a voltage obtained by removing the offset DC voltage from the output of the position detection device 118 is output. The counter 121 and the flip-flop (FF) 123 supply a clock signal (C
K) 125 is supplied. Next, the operation will be described. First, a tracking error signal due to diffraction from a track on the disk 100 appears at the output of the differential amplifier 104 when the switch 107 is open. At this time, it is assumed that the objective lens of the movable optical system is focused on the recording surface of the disk 100 by a focus servo (not shown). The pulse voltages shown in FIG. 4 are obtained at the outputs of the comparators 113 and 114. By inputting these two pulse signals to the order detection circuit 115, a pulse voltage 115 indicating the end of the period T shown in FIG. 2 is obtained. After the tracking servo operation command signal is input, this voltage is held by the latch circuit 116, the switch 107 is closed, and the tracking servo system operates. In this case, the optimum pull-in point of the tracking servo system can be selected by appropriately selecting the voltages of + a and -b. For example, by setting + a = 0, it is possible to close the tracking servo at the zero crossing point of the tracking error signal. In this case, the movable optical system 10
1 means that the tracking servo system starts operating stably without unnecessary displacement. Next, if any disturbance (vibration, disk defect, etc.) is applied to the device while the tracking servo system is operating,
The tracking servo system may not be in a normal state. At this time, the tracking error signal (the output of the differential amplifier)
At 104), a signal crossing the track appears. This is detected by the window comparator 109, the number of times the track is traversed is calculated by the counter 110, and the latch circuit 111 is held when the specified number is reached. Then, the counter 121 is immediately held, and a signal indicating the position of the movable optical system 101 without a DC offset is output to the output of the operation amplifier 119. This is input to the terminal 105-2 of the switch 105, and a signal passed through a delay circuit 112 for giving a time for stabilizing the output of the differential amplifier 119 is applied to the terminal 105.
The 5-2 side is connected. In this way, the position of the movable optical system 101 is controlled so that the output of the position detector 117 becomes 0, and does not significantly deviate from the position when the tracking servo system is operating normally. Of course, when the disturbance is removed, the tracking servo system starts a normal operation again. That is, the pull-in operation of the tracking servo system is performed again. As described above, according to the present invention, the tracking servo system is normally controlled by a tracking error signal obtained by a track on a disk, and when this tracking servo cannot operate normally due to a disturbance, the movable optical system It operates according to the position detection signal indicating the position. Thereby, even when the tracking servo system of the movable optical system uses a movable optical system that can follow from the inner circumference to the outer circumference of the disk, stable operation is guaranteed. In addition, even when the tracking servo system is turned on, a range in which the tracking servo system can be pulled in stably can be detected from the tracking error signal, and a period during which a quick pull-in operation can be performed can be set. As described above, the separation optical system has a great effect, thereby enabling the practical use of a separation optical system capable of performing a high-speed search.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a principle (block) diagram of a tracking device according to an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation principle thereof, and FIG. FIG. 4 is a detailed block diagram of the tracking device of the embodiment, FIG. 4 is a waveform diagram showing the operation of the embodiment, and FIG. 5 is a block diagram showing a conventional tracking device. 50: a disk, 52: a movable optical system, 60: a fixed optical system, 68: a switch, 56: a drive device for displacing the movable optical system.

Claims (1)

(57) [Claims] In a tracking device of a recording / reproducing apparatus for recording / reproducing an information signal on a recording track by using a light beam on a record carrier having a recording track, an optical head for generating a light beam is incident on an objective lens and the objective lens. A movable optical system part integrally configured with an optical element to be separated, and a fixed optical system part having at least a laser and a light receiving device, and the only scanning device that moves only the movable optical system in the radial direction of the record carrier. And a tracking servo system for tracking the only scanning device to a recording track of the record carrier,
When the tracking servo system is pulled into the recording track, a polarity and a DC level of the tracking error signal are detected from a tracking error signal obtained by irradiating the recording track with a light beam, and the polarity indicates information. A tracking device, wherein the tracking servo system starts the pull-in operation when the polarity is a predetermined polarity for pull-in on recording tracking to be recorded and the DC level is within a predetermined range. 2. A position detector for detecting the position of the movable optical system is provided. If a tracking error signal exceeds a specified range during operation of the tracking servo system, a signal obtained by removing a DC component from the output of the position detector is used as a tracking servo. 2. The tracking device according to claim 1, wherein the tracking error signal is supplied to the system instead of the tracking error signal.