JPH0316104Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a tracking feed control device in a compact disk player, etc. In particular, during random access, the objective lens of an optical reading unit is moved in the disk radial direction by a tracking pulse. The present invention relates to a tracking feed control device that performs fine feeding.

<Prior Art> In compact disc players and video disc players, an optical pickup for reading digital information recorded on a disc is positioned at a desired position, and the information can then be read from that position. (referred to as random access method). In other words, during random access,
A deviation signal corresponding to the deviation between the current position and the target position of the optical pickup is generated, and the deviation signal is input to the slider motor drive circuit to rotate the slider motor, thereby moving the optical pickup toward the target position. . After the optical pick-up reaches the vicinity of the target position, the objective lens constituting the optical pick-up is finely fed at low speed by a tracking pulse (tracking feed) to read information from the disk and send it to the sub-coding P channel. When a logical 1 indicating the beginning of a song is written, the objective lens is assumed to have reached the target track and stops.

Incidentally, information pits are recorded on the disk in a spiral manner with a track pitch of 1.6 microns using the CLV method (constant linear velocity control method). When reading information, the rotational speed of the disk is controlled so that the speed of the optical pickup in the circumferential direction of the disk (referred to as linear speed) is constant, and the optical pickup reads information from the disk under the constant linear speed. Therefore, when the optical pickup moves with the same number of tracks near the inner and outer peripheries of the disk, the number of read information is greater on the outer periphery than on the inner periphery.In other words, time information (absolute time before and after movement) The difference in information) changes more greatly on the outer circumference than on the inner circumference. In addition to audio data, sub-coding is recorded on the CD, and the sub-coding allows absolute time information from the beginning to be recognized.

<Disadvantages of the Prior Art> In the conventional tracking feed, a tracking pulse of constant amplitude and constant width is generated to move the objective lens a predetermined number of tracks, regardless of the position of the optical pickup. Therefore, there is a difference in time information between when the optical pickup is present near the inner circumference and when it is present near the outer circumference. Note that the time information here refers to the difference in absolute time information before and after the track has been moved a predetermined number of tracks by the tracking pulse. This is the time required to move the number of tracks in the direction.

In this way, in the conventional method, the time information per tracking pulse differs between the inner and outer peripheries of the disk, so if tracking feed is performed uniformly during random access, it is difficult to feed near the inner periphery, but it is difficult to feed near the outer periphery. Then there was the problem of making it easier to send. In other words, since the time information per tracking pulse is small near the inner circumference, the number of tracking pulses input until reaching the target track increases, and the disadvantage is that the time required to reach the target track increases accordingly. It was hot.

<Purpose of the invention> The purpose of the invention is to provide a tracking feed control device that can keep the time information associated with the movement per one tracking pulse constant regardless of the radial position of the optical pickup and can perform uniform tracking feed. The goal is to provide the following.

Another object of the present invention is to provide a tracking feed control device that can increase the amount of movement per one tracking pulse as the optical pickup is closer to the inner circumference, thereby keeping the time information associated with the movement per one tracking pulse approximately constant. It is to provide.

<Summary of the invention> The tracking feed control device of the invention includes a position detector that detects the radial position of an optical reading unit (optical pickup) with respect to the disk, and a position detector that detects the radial position of the optical reading unit (optical pickup) with respect to the disk. It has an amplitude control circuit that increases the amplitude of the tracking pulse, and uses the amplitude-controlled pulse to move the optical reading unit in the disk radial direction.
According to this tracking feed control device, regardless of the radial position of the optical reading unit, the time information can be made constant due to the movement per one tracking pulse, and uniform tracking feed can be performed. can.

<Example> Fig. 1 is an explanatory diagram of the main parts of a compact disc player including a tracking feed control device according to the present invention, and Fig. 2 is a circuit diagram of an amplitude control circuit constituting the tracking feed control device of the present invention. FIG. 3 is a schematic explanatory diagram of a general optical pickup. Acoustic signals are digitally recorded on the compact disc 1, and control data called frame synchronization signals and subcoding are also recorded for each predetermined number of data. In addition, sub-coding is P, Q,
Consists of 8 bits R, S, T, U, V, W,
One block is formed by 98 sub-codings, and information indicating the beginning of the song is recorded in the P channel of the block, and information indicating the beginning of the song is recorded in the Q channel (a) The song number corresponding to the current position of the optical pickup 2, (b) Information on how many minutes and seconds from the beginning of the song number (referred to as a time record) and what frame the optical pick-up exists, (c) and the absolute time record from the initial position of the optical pick-up 2 ( absolute time information) etc. are recorded.

The optical pickup 2 optically reads disc information recorded on the compact disc 1 and inputs it to the waveform processing circuit 3. The waveform processing circuit 3 amplifies the RF signal output from the optical pickup 2, and also shapes the waveform at a predetermined slice level.
Signal obtained by waveform shaping (called EFM signal)
is input to the control unit 4 and CLV circuit 5. The control unit 4 demodulates the EFM signal, separates the audio data and sub-coding, performs error detection/correction processing on the audio data, performs DA conversion, and outputs the data to the audio circuit 6. Also, the control unit 4
analyzes the Q channel of the sub-coding, extracts data indicating the current song number, elapsed time for each song, total elapsed time, etc., inputs it to the display device 7 for display, and performs random access control. Let's do it. On the other hand, the CLV circuit 5 generates the EFM signal and the crystal oscillator built in the control unit 4.
A drive signal for rotating the spindle motor 8 at a constant circumferential speed is output using the 4.3218 MHz clock signal CLS.

Now, when the currently playing song ends while the song number to be selected next is input from the operation panel 9, the control unit 4 moves the optical pickup 2 to the current position and the target position where the predetermined song number is recorded. A pick-up feed pulse PFP with a pulse width corresponding to the deviation between the two is input to the slider motor 11 via the slider motor drive circuit 10. As a result,
The slider motor 11 rotates, and the optical pickup 2
move towards the target position. When the optical pick-up 2 reaches the vicinity of the target position (when a time corresponding to the pulse width of the pick-up feed pulse PFP has elapsed), the control unit 4 finely moves the objective lens attached to the optical pick-up 2 in the track direction. Generate tracking pulse TRP and control pulse BRP for this purpose. In addition, tracking pulse
TRP and control pulse BRP have a constant amplitude and a constant width, as shown in FIGS. 4A and 4B. In addition, when moving the optical pickup 2 toward the outer circumference, the control unit 4 applies a tracking pulse to the line _l2 .
In addition to outputting TRP, a braking pulse BRP is output to line _l1 , and when moving the optical pickup 2 toward the inner circumference, line _l1 is the tracking pulse TRP.
It also outputs a braking pulse to line _l2 .
A synthesis circuit 12 synthesizes the tracking pulse TRP and the braking pulse BRP to generate an objective lens feeding pulse.
LFP (see FIG. 4 C or D) is generated, and the objective lens feed pulse LFP is input to the amplitude control circuit 13. On the other hand, the position detector 14 operates in conjunction with the optical pickup 2 to generate a voltage signal PVS having a level corresponding to the radial position of the optical pickup 2, and inputs it to the amplitude control circuit 13. Note that as the position detector 14, for example, a variable resistor is used.

The amplitude control circuit 13 modulates the amplitude of the objective lens feed pulse LFP, which is the output of the synthesis circuit 12, in accordance with the radial position of the optical pickup 2.
That is, the amplitude control circuit 13 operates so that the closer the optical pickup 2 is to the inner circumference, the larger the amplitude of the pulse is output. Note that a tracking feed control device is constituted by the synthesis circuit 12, the amplitude control circuit 13, and the position detector 14.

FIG. 2 is a block diagram showing an example of the amplitude control circuit 13. The function generator 13a is configured to generate a larger voltage as the radial position of the optical pickup 2 is closer to the inner circumference, in other words, the smaller the output voltage of the position detector 14 is. Polarity discriminator 1
3b determines the polarity of the objective lens feed pulse LFP output from the synthesis circuit 12, and if the polarity is positive, a signal PS is output during that time, and if it is negative, a signal NS is output during that time. Analog gate 13c is opened by signal PS, and analog gate 13d is opened by signal NS. Further, the inverter 13e inverts the polarity of the output voltage of the function generator 13a. Therefore, the objective lens feed pulse shown in FIG.
When LFP is input, depending on the radial position of the optical pickup 2 at that time, in other words, the closer the optical pickup is to the inner circumference, the larger the amplitude of the sending pulse FP (see the dotted line in Fig. 4C) is sent to the synthesis circuit. 13f
It is output from Furthermore, if the objective lens feed pulse LFP shown in Fig. 4D is input, a feed pulse FP (see the dotted line in Fig. 4D) having an amplitude corresponding to the radial position of the optical pickup at that time is similarly synthesized. It is output from the circuit 13f.

Sending pulse output from amplitude control circuit 13
FP is applied to the tracking coil of optical pickup 2. The objective lens, which is a component of the optical pickup 2, is moved in the disk radial direction by a tracking pulse TRP' included in the feed pulse FP, and is also braked by a control pulse BRP'.
In other words, the objective lens is tracking pulse
The amount corresponding to the amplitude of TRP' will be located in the radial direction of the disk. FIG. 3 is a schematic explanatory diagram of the optical pickup 2, in which 2a is an objective lens, 2b, 2
b' is a magnetic field generation unit that generates a magnetic field with the polarity shown, 2c is a bobbin, 2d is a tracking coil,
2e is a focus coil. Bobbin 2c is A
It is disposed so as to be movable in the direction of the arrow and the direction of the arrow B, and an objective lens 2a is attached to the bobbin, and a tracking coil 2d and a focus coil 2e are attached to the bobbin.
are wrapped around each other. Therefore, when the tracking coil 2d is energized, the bobbin 2 is moved by electromagnetic force.
In other words, the objective lens 2a moves in the direction of arrow A to perform tracking feed, and when the focus coil 2e is energized, the objective lens 2a moves in the direction of arrow B to perform focus adjustment.

<Effects of the invention> As explained above, in this invention, the closer the disk radial position of the optical pickup 2 is to the inner circumference, the greater the amplitude of the tracking pulse, and the closer to the outer circumference, the smaller the amplitude. The amount of movement per one tracking pulse increases as the distance approaches the inner circumference. Therefore, the time information per one tracking pulse can be kept approximately constant regardless of the position of the optical pickup, allowing uniform tracking feed. . Unlike conventional devices, the time required for random access control does not differ between the outer and inner peripheries, and even when the optical pickup is near the inner periphery, it is the same as when it is near the outer periphery. Quick random access is now possible.

In the above explanation, the present invention was applied in detail to a compact disc player, but the present invention is of course applicable not only to such a case but also to a disc device in which information is written using the CLV method. . Further, the amplitude control circuit 13 is not limited to the one shown in FIG. 2, and can be modified in various ways, such as by controlling the gain of the amplifier.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the main parts of a compact disc player including a tracking feed control device according to the present invention, FIG. 2 is a circuit diagram of an amplitude control circuit constituting the tracking feed control device of the present invention, and FIG. FIG. 4 is a schematic explanatory diagram of a general pickup, and is a waveform diagram of each part of the amplitude control circuit according to the present invention. 1... Compact disk, 2... Optical pickup, 3... Waveform processing circuit, 4... Control unit, 5... CLV circuit, 8... Spindle motor,
9...Operation panel, 11...Slider motor, 1
2... Synthesis circuit, 13... Amplitude control circuit, 14...
...Position detector.

Claims (1)

[Claims for Utility Model Registration] (1) In a tracking feed control device that uses tracking pulses to move an optical reading unit that optically reads information recorded on a disk rotating at a constant linear velocity, A position detector for detecting the radial position of the optical reading unit with respect to the disk, and an amplitude control circuit that increases the amplitude of the tracking pulse as the radial position of the reading unit approaches the inner circumference. Features a tracking feed control device. (2) The tracking feed control device according to claim 1, wherein the tracking pulse moves an objective lens of an optical reading unit.