JP3582861B2 - Optical disc reproducing apparatus and pickup movement control method therefor - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an optical disk reproducing apparatus for reproducing an optical disk such as a CD (compact disk) and a CD-ROM, and a pickup movement control method thereof.
[0002]
[Prior art]
Conventionally, in an optical disk reproducing apparatus, when a pickup is moved to a desired position on an optical disk, the number of tracks traversed is detected by detecting an electrical ripple waveform in an RF signal generated when the pickup traverses a track. Counting is performed, and the movement reaching position (moving distance) of the pickup is determined based on the count value, and the pickup is guided to the target position.
[0003]
In this method, the key to accuracy is how accurately the ripple waveform can be detected from the RF signal. However, in recent years, the track pitch of an optical disk has been narrowing due to its high density, and it has become difficult to accurately detect the ripple waveform. This is because the level (waveform amplitude) of the ripple waveform in the RF signal generated when the pickup traverses the track becomes lower as the track pitch becomes narrower if the moving speed of the pickup at the time of reading information from the optical disk is the same. Therefore, when the pickup is moved at high speed during special reproduction such as high-speed search, a ripple waveform is not generated at a level sufficient for detection. As a result, the number of tracks crossed by the pickup is incorrectly counted, and the pickup cannot be moved to the target position correctly.
[0004]
To solve this problem, a method of slowing down the moving speed of the pickup is considered. However, the special reproduction speed such as search becomes slower, which is not an advantageous measure.
[0005]
As another method, a moving distance detector such as a tack is attached to a carriage equipped with a pickup, and at the time of high-speed special reproduction such as a search, the moving distance of the pickup is measured by using the moving distance detector. A method for controlling the movement of the pickup without relying on ripple waveform information has been proposed.
[0006]
However, this method requires high accuracy in mounting the moving distance detector, and increases the cost due to additional components of the moving distance detector.
[0007]
[Problems to be solved by the invention]
As described above, in the conventional optical disc reproducing apparatus, with respect to the movement control of the pickup during high-speed special reproduction such as search, the ripple waveform in the RF signal when the pickup crosses the track is detected and counted, and the movement arrival position of the pickup ( Travel distance). However, according to this method, unless the moving speed of the pickup is reduced, the accuracy of detecting the ripple waveform is degraded as the track pitch of the optical disk becomes narrower, and the pickup cannot be moved to the target position correctly.
[0008]
An object of the present invention is to solve such a problem, and an optical disk reproducing apparatus capable of accurately moving a pickup to or near a target position without being influenced by a track pitch of the optical disk, and a pickup movement control method thereof The purpose is to provide.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is based on a result obtained by moving the pickup from an initial position by a feed mechanism and obtaining respective times at which a plurality of points having different distances from the initial position are reached. Storage means storing distance-time information indicating the relationship between continuous distance and time, and when a target position to which the pickup is moved is specified, the current position of the pickup and the target position Is calculated, the time required to move the calculated distance is obtained based on the distance-time information stored in the storage means, and the feed mechanism is moved so that the pickup is moved by the obtained time. And control means for controlling.
[0010]
In addition, the present invention includes a correction unit that detects an error between the position after movement of the pickup and the target position, and corrects the distance-time information stored in the storage unit based on the error. .
[0011]
Further, according to the present invention, after turning on the main power source, the pickup is moved from the initial setting position for a predetermined time, an error between the position after the movement and a target position corresponding to the moving time is obtained, and the error is calculated based on the error. Another correction means for correcting the distance-time information stored in the storage means is provided.
[0012]
[Action]
In the present invention, the control means calculates the distance between the current position of the pickup and the target position when the target position to which the pickup is moved is specified, and stores the time required to move the calculated distance. Based on the distance-time information indicating the relationship between the continuous distance and the time stored in the means, the feed mechanism is controlled so that the pickup is moved by the determined time. The distance-time information is created based on a result obtained by moving the pickup from the initial position by the feed mechanism and obtaining respective times at which a plurality of points having different distances from the initial position are reached. If the content of the time information is correct, the correct travel time required to move the distance between the current position of the pickup and the target position can be known based on the distance-time information, and the pickup can be moved to the target position. Alternatively, it can be reliably moved to the vicinity thereof.
[0013]
The correction means detects an error between the position of the pickup after the movement and the target position, and corrects the distance-time information stored in the storage means based on the error. , The correct distance-time information can always be held.
[0014]
The other correction means moves the pickup from the initial setting position for a predetermined time after the main power is turned on, that is, before high-speed special playback such as a search operation is performed, and corresponds to the position after the movement and the movement time. The distance-time information stored in the storage means is corrected based on the error from the target position to be performed, so that even if the operation state of the feed mechanism of the pickup changes due to aging or the like, it is always correct. Distance-time information can be stored.
[0015]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a block diagram showing an overall configuration of an optical disc reproducing apparatus according to one embodiment of the present invention.
[0017]
In the figure, information is recorded on the optical disc 1 in units of sectors, and tracks, which are collections of one round of the sector, are arranged at a constant pitch in the radial direction of the disc. Reference numeral 2 denotes an optical pickup that irradiates the optical disc 1 with laser light and reads the intensity of the reflected light as a reproduction signal. The optical pickup 2 can be moved by a pickup feeding mechanism (not shown) in the direction of the arrow, that is, as shown in FIG. Reference numeral 3 denotes a data slicer that performs processing such as waveform equalization and data slicing on the output RF signal of the optical pickup 2 to obtain a binary signal. Reference numeral 4 denotes a PLL circuit that generates a data reproduction clock from the binary signal output from the data slicer 3. Reference numeral 5 denotes a demodulation / error correction circuit that performs demodulation and error correction on reproduced data fetched from the binary signal sequence using the clock. Reference numeral 6 denotes a drive circuit for driving the pickup feed mechanism. Reference numeral 7 denotes a microprocessor unit (hereinafter, referred to as an MPU) for controlling the entire apparatus, including a CPU, a ROM in which programs executed by the CPU and various data are fixedly stored, and a ROM. It is configured to include a nonvolatile memory such as an EEPROM that stores a distance-time table and the like described later. Although not shown, this apparatus is configured to include a disk drive system, various servo systems, and the like.
[0018]
The MPU 7 performs the following pickup movement control in accordance with a predetermined program in the ROM. The details will be described below.
[0019]
In FIG. 3, when the pickup 2 is moved from the position shown in the figure (initial setting position) in the direction of the arrow at the speed at the time of the high-speed special reproduction, the relationship between the moving distance and the required moving time is as shown in FIG. It will be.
[0020]
Therefore, if information indicating the relationship between the moving distance and the required moving time is prepared in advance, when the target position to which the pickup 2 is to be moved is specified, the current position of the pickup 2 and the target position are determined. From the distance and the information, the time required for the pickup 2 to move to the target position can be obtained, and the movement distance of the pickup 2 can be controlled almost accurately by time.
[0021]
In order to specifically implement the pickup movement control based on such time, accurate information indicating the relationship between the above-described movement distance and the time required for the movement is required. However, the relationship between the distance and the time varies slightly from product to product even for the same type of device, and the relationship changes from time to time due to aging.
[0022]
In view of such circumstances, in the present embodiment, a distance-time table indicating the relationship between the moving distance and the required moving time for each product is created on the manufacturing side before the device is shipped, and this is stored in the non-volatile memory in the MPU 7. It shall be recorded in the memory.
[0023]
A specific example method for creating this distance-time table will be described below. For example, as shown in FIG. 3, a plurality of points (for example, four points A, B, C, and D) are set between the innermost track and the outermost track on the optical disc 1, and for each point, The pickup 2 is moved from the position shown in the figure (initial setting position) to a target in the direction of the arrow at a speed at the time of high-speed special reproduction. The movement at this time is performed by moving the pickup 2 for a preset time for each point. That is, first, the pickup 2 is moved from the initial setting position to the point A as a target for the set time. After the movement, the track / sector information recorded on the optical disk 1 is detected, and it is checked to which position on the optical disk 1 the pickup 2 has actually moved. Then, an error between the actual movement position and the target position (point A) is detected, and the set time is corrected based on the error. Next, the pickup 2 is moved from the initial position to the target at the point B for the set time, and similarly, an error between the actual moving position and the target position (point B) is detected. Correct the set time. Hereinafter, similarly, the same processing is performed for each of the points C and D.
[0024]
The correction of the set time for each point described above is repeatedly executed for one point a plurality of times, and the average value is set for each point as the final set time before product shipment. Then, the distance-time table is created from the set time for each point.
[0025]
By the way, the distance-time table in consideration of the variation for each product is prepared as described above. In addition to this, in the present embodiment, the distance-time table mainly takes into account the aging of the operation state of the pickup feed mechanism. The contents of the time table can be corrected by the user. This operation will be described below.
[0026]
When the main power is turned on to the apparatus, the MPU 7 reads the contents of the distance-time table from the non-volatile memory, and approximates the relationship between the distance and time into an approximate expression. After the optical disk 1 is mounted on the apparatus, the MPU 7 immediately executes the same operation as the test movement of the pickup 2 before shipping the product, based on the relationship between the distance and the time expressed by the above formula. Then, based on the error between the actual movement position of the pickup 2 for each point and the target position, the relationship between the distance and the time expressed by the above formula is corrected.
[0027]
Thereafter, when a target position of the pickup 2 is designated for high-speed special reproduction such as a search operation, the MPU 7 obtains a distance Y from the current position of the pickup 2 to the target position, and moves the distance Y. The required time X is obtained from the above equation. Then, the pickup 2 is moved for the calculated time X, the track / sector information is detected at that position, and an error from the target position is determined.
[0028]
If the error is zero in this determination, the information is read from the optical disk 1 as it is. If there is an error, the pickup 2 is moved at a low speed, a ripple waveform in an RF signal generated when the pickup 2 crosses a track is detected, and the pickup 2 is moved to a target position. Then, the contents of the distance-time table are corrected again from the error.
[0029]
As described above, it is possible to move the pickup 2 to the target position or its vicinity at a stroke without depending on the ripple waveform information when the pickup 2 crosses the track, and it is also good for the optical disc 1 having a narrow track pitch. In addition, the pickup can be accurately moved to the target position or its vicinity.
[0030]
When the pickup 2 is moved to the target position, as shown in FIG. 5, it is necessary to reversely drive the feed motor and apply a brake to the motor before the pickup 2 reaches the target position. Therefore, specifically, a time point X1 at which the feed motor is reversely driven is obtained from the required travel time X with respect to the travel distance, and the feed motor is reversely driven at the time point X1, and finally reaches the required travel time X. It is necessary to make the motor stop at the moment.
[0031]
【The invention's effect】
As described above, according to the present invention, when the target position to which the pickup is to be moved is specified, the distance between the current position of the pickup and the target position is calculated, and the distance required for moving the calculated distance is calculated. The pickup can be moved for this time by obtaining the time, whereby the pickup can be accurately moved to the target position or the vicinity thereof without being affected by the track pitch of the optical disk.
[0032]
Further, in the present invention, when moving the pickup by the feed mechanism, distance-time information indicating the relationship between the continuous movement distance and the required movement time, based on the error between the movement position of the pickup and the target position, Furthermore, since the correction is made based on the error between the movement position of the pickup and the target position obtained by the test movement of the pickup after the main power is turned on, there is a change in the operation state of the pickup feed mechanism due to aging or the like. Can also be sequentially updated to correct distance-time information, and the accuracy of the pickup movement can be ensured as much as possible.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of an optical disc reproducing apparatus according to an embodiment of the present invention.
FIG. 2 is a plan view showing a relationship between an optical disk and a pickup in the optical disk reproducing device of FIG.
FIG. 3 is a diagram for explaining a specific method for creating a distance-time table.
FIG. 4 is a graph showing the relationship between the movement distance of a pickup and the time required for the movement.
FIG. 5 is a diagram illustrating a state of driving a motor when the pickup is moved to a target position.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Optical pickup, 3 ... Data slicer, 4 ... PLL circuit, 5 ... Demodulation / error correction circuit, 6 ... Drive circuit, 7 ... Microprocessor unit (MPU).

Claims (4)

A pickup for reading information recorded on an optical disc;
A feed mechanism for moving the pickup on the optical disc in a direction crossing tracks of the optical disc;
Said by the feed mechanism moves the pickup from the initial position, the distance from the initial position is created on the basis of the result of obtaining each time reaching the different points of the continuous distance and time Storage means for storing distance-time information indicating the relationship;
When a target position to which the pickup is to be moved is specified, the distance between the current position of the pickup and the target position is calculated, and the time required to move the calculated distance is stored in the storage means. An optical disc reproducing apparatus comprising: control means for controlling the feed mechanism so as to move the pickup by the determined time based on distance-time information. The optical disc reproducing apparatus according to claim 1,
An optical disc reproducing apparatus further comprising a correction unit for detecting an error between the position of the pickup after the movement and the target position, and correcting the distance-time information stored in the storage unit based on the error. apparatus. The optical disc reproducing apparatus according to claim 1,
After the main power is turned on, the pickup is moved from the initial setting position by a predetermined time, an error between the position after the movement and a target position corresponding to the movement time is obtained, and the error is stored in the storage means based on the error. An optical disc reproducing apparatus further comprising a correction unit for correcting the distance-time information. A pickup for reading information recorded on an optical disc;
A feed mechanism for moving the pickup on the optical disc in a direction crossing tracks of the optical disc;
Said by the feed mechanism moves the pickup from the initial position, the distance from the initial position is created on the basis of the result of obtaining each time reaching the different points of the continuous distance and time Storage means for storing distance-time information indicating the relationship is provided,
When a target position to which the pickup is to be moved is specified, the distance between the current position of the pickup and the target position is calculated, and the time required to move the calculated distance is stored in the storage means. A pickup movement control method, wherein the pickup mechanism is determined based on distance-time information, and the feed mechanism is controlled so as to move the pickup by the determined time.

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