JPH0316037A - Tracking servo-circuit - Google Patents

Abstract

PURPOSE:To stop the operation of a correcting means at that time point even if a storage means stores an erroneous value due to noise, so that an error of a tracking error signal does not become larger by operating the correcting means only when a sector mark signal and a total reflection area instructing signal are detected alternately. CONSTITUTION:This circuit is provided with a first signal inspecting means 1 for inspecting a fact that a total reflection area instructing signal 20 and a sector mark signal 13 are detected alternately as a pair, and a second signal inspecting means 2 for checking a fact that the total reflection area instructing signal 20 or the sector mark signal 13 or a signal for showing a pair of both the signals is inputted at least once after an output of the signal detecting means 1 becomes active. In this case, when an output 16 of a second signal inspecting means 2 goes to active after the output 15 of a first signal inspecting means 1 goes to active, an offset correction of a tracking error signal is executed. In such a way, an offset can be eliminated exactly from the tracking error signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tracking servo circuit in an optical information recording/reproducing device.

[Conventional technology] Optical information recording and reproducing devices record and reproduce information by focusing a laser beam onto the recording medium of an optical disk (hereinafter, the focal point of the light is referred to as a spot). It has a groove (hereinafter referred to as a track) that guides the track. An optical information recording/reproducing device generates a tracking error signal from reflected light or transmitted light from a recording medium to indicate a relative positional deviation between the track and the track, and controls the spot to follow the track (hereinafter referred to as tracking servo). It is carried out. Tracking servo circuits generally detect reflected or transmitted light with multiple sensors,
These outputs are differentially amplified to create a tracking error signal, and the track position is controlled so that the value becomes O.

At this time, unnecessary offset components are generally generated in the tracking error signal due to the inclination of the disk, resulting in a drawback that accurate position control cannot be performed. As a method to eliminate this drawback, a method has been devised in which a part of the track is provided with an area where there is no track (hereinafter referred to as a total reflection area) to remove 7 sectors of the tracking error signal. (1973-19250). This method takes advantage of the property that only the offset appears in the tracking error signal when there is a spot in the total reflection area, stores the amount of offset at that time, and removes the offset from the tracking error signal. .

Therefore, the conventional tracking servo circuit has a circuit for removing a certain amount of offset as shown in FIG. Reflected light or transmitted light from the recording medium is converted into an electrical signal by the split type optical sensor 5. By differentially amplifying each output of the split type optical sensor 5 by the detection means 6,
Generate a tracking error signal. At this point, the tracking error signal includes an offset error caused by the inclination or warpage of the recording medium. In the storage means 4, a switch is opened or closed by a total reflection area instruction signal indicating that the spotato is in the total reflection area, and a switch is opened or closed in the detection means 6.
The amount of offset 1 appearing in is memorized. Then, the correction means 5 uses the value stored in the storage means 4 to remove the offset component from the tracking error signal. What is important here is that an accurate offset amount must be stored in the storage means.

[Problem to be Solved by the Invention] However, the prior art However, if the total reflection area instruction signal is output when the spot is not in the total reflection area, there is a problem that the storage means 4 stores a value different from the desired offset amount. When such a situation occurs,
On the other hand, the tracking error signal contains a large error, making it impossible to accurately track the slot 1. Further, immediately after the tracking servo circuit starts operating, the output of the storage means 4 is at an undefined k value, and due to this influence, there is also the problem that the spot cannot be drawn into the tracking servo operation.

Therefore, the present invention is intended to solve these problems, and its purpose is to provide a tracking servo circuit of the present invention for solving the problem of disc [ll]. In a tracking servo circuit that causes the light beam subboard 2} focused on the disk to follow a guide g4 (track) provided in advance on the disk, b) a split-type optical sensor that receives reflected light or transmitted light from the recording medium; C) a detection means for differentially amplifying the output of the split optical sensor to generate a tracking error signal indicating a relative positional deviation between the spot and the track; and d) a detecting means provided in advance on the disk. storage means for storing an offset amount of the tracking error signal according to an instruction of a total reflection area instruction signal indicating an area with no track; #) the total reflection area instruction signal and the sector mark signal are alternately paired; The first step is to check that it has been detected.
and f) after the output of the first signal testing means becomes active, at least one signal indicating the total internal reflection area indication signal or the sector mark signal or a pair of both signals is activated.
a second signal inspection means for checking whether the times have been input; and ! i) correcting the tracking error signal based on the output of the storage means, and determining whether or not to perform the correction operation based on the output of the second signal inspection means;
It is characterized by comprising a correction means that changes the

Since the present invention has the above-described configuration, the sector mark signal (described later in the embodiment) and the total reflection area instruction signal are detected in pairs alternately by the first signal inspection means. If not, the second signal detection means is not operated, so the correction means does not perform offset correction. Therefore, the correction means does not operate immediately, and the correction means does not start the correction until the signal indicating the total reflection area instruction signal, the sector mark signal, or a pair of both signals is received at least once and the correct offset amount is stored in the storage means. It starts to work.

[Example code] Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 is an example of a configuration diagram of a tracking servo circuit according to the present invention. 1 indicates a first signal inspection means, and 2 indicates a second signal inspection means. Specific circuit examples of the first signal testing means and the second signal testing means are shown in FIGS. 2 and 6, respectively. The split type optical sensor 5 receives reflected light or transmitted light from the recording medium. The detection means 6 differentially amplifies both outputs of the split optical sensor 5 to generate a tracking error signal. The tracking error signal is adjusted so that it becomes 0 when the spot is at the optimal position on the track. However, an offset occurs in the output of the detection means 6 due to the inclination of the recording medium and the like. The storage means 4 stores the offset amount of the tracking error signal at the timing of the total reflection area instruction signal 20. That is, when the spot is located in the total reflection region, the switch is turned on and the output of the detection means 6 is stored in the capacitor. Since there is no track in the total reflection area, only the offset amount is output from the detection means 6 at this point. By turning off the switch of the storage means 4 before the spot returns to the track area, only the offset amount of the tracking error signal is stored in the storage means 4. The offset is removed from the tracking error signal by the correction means 3, and an accurate tracking error signal 19 is output. The correction means 3 is provided with a changeover switch, and it is possible to select whether or not to perform offset correction of the tracking error signal. In this embodiment, the output 15 of the first signal testing means 1
When the output 16 of the second signal inspection means 2 becomes active after the output 16 becomes active, the offset of the tracking error signal is corrected.

Incidentally, in a recording medium used in an optical information recording/reproducing apparatus, tracks are arranged in units called sectors, and one total reflection area is provided in each sector. In addition, at the beginning of each sector, there is an area where information called a sector mark is recorded, and optical information recording/reproducing devices usually mark the sector immediately after the spot passes through that area to indicate the beginning of the sector. Mark signal 13 is being detected. Therefore, the sector mark signal 15 and the total reflection area instruction signal 20
must be detected in alternating pairs. For example, the first signal inspection means shown in FIG.
3 and the total reflection area instruction signal 20 are detected in alternating pairs, the output 15 is activated (active High).
Let it be h. ). If the sector mark signal and the total reflection area indication signal are not detected in alternating pairs due to noise being superimposed on the total reflection area indication signal 20, the output 15 of the first signal inspection means immediately becomes inactive. Become. Further, for example, in the second signal inspection means shown in FIG. 3, when the second pulse of the total reflection area instruction signal 200 is input after the output 15 of the first signal inspection means becomes active, the output 16 becomes active. Become. Immediately after the tracking servo movement starts, it is not known what kind of value is stored in the storage means 4. Further, even if the storage means 4 malfunctions due to the influence of noise, the stored value will be significantly different from the offset amount.

Therefore, immediately after the tracking servo burst starts or when the first signal inspection means 15 is inactive, the correction means 3 is made inactive so that the output of the recording means 4 does not affect the tracking error signal.

FIG. 4 shows the actual state of each signal. Track shape 1 where all the respective signals are active high signals
7 indicates a sector mark area, and 8 indicates a total reflection area. The track shape diagram here is a schematic diagram for explaining the present invention, and the shape and size of each part are different from the actual one. After the power supply 1B is turned on, when the sector mark on the track is read, a sector mark signal pulse 9 is detected. When the spot is located on the total reflection area 8, a total reflection area indication signal pulse 10 is detected. 9,100
The output 15 of the first signal testing means after the pulse has been detected.
becomes active. At this point, the output 16 of the second signal testing means is inactive. When the second total reflection area indicating signal pulse 11 is detected after the output 15 of the first signal testing means becomes active, the output 16 of the second signal testing means becomes active. From this point on, the correction means 3 operates to remove the offset from the tracking error signal. Since the normal total reflection area indication signal 20 is always detected by detecting the signal twice,
This means that the storage means accurately stores the offset amount.

Here, it is assumed that the noise 12 is superimposed on the total reflection area instruction signal. When this happens, a value different from the offset amount is stored in the storage means 4. However, no sector mark signal is detected between the noise 12 and the correct total reflection area instruction signal pulse 11. Therefore, the first signal testing means detects the abnormality and makes the output 15 inactive. As a result, the output 16 of the second signal testing means is also inactive, the correction means 6 is switched, and the output of the storage means 4 no longer influences the tracking error signal.

If the switch of the correction means 6 is not switched υ when 12 noises are superimposed, the final tracking error signal is corrected based on the output of the storage means 4 which stores a value different from the offset amount. The tracking error signal 19 contains a large error (which makes accurate tracking operation impossible). After the output 16 of the second signal testing means becomes inactive, follow the same procedure as when turning on the power. Restart tracking error signal correction.

In the above embodiments, the total reflection area indicating signal was used as an input to the second signal inspection means. However, the first
The signal inspection means obtains a paired signal 14 indicating that the sector mark signal and the total reflection area instruction signal appear in alternating pairs, so the paired signal 14 and sector mark signal 13 that appear there are shown in FIG. It may be used instead of the total reflection area indicating signal as an input to the second signal inspection means shown in FIG. Also,
In this embodiment, the number of inputs of the total reflection area instruction signal, etc. necessary to activate the output of the second signal inspection means is set to two, but if it is input more than once, it is the same as in this embodiment. You can expect great effects.

[Effects of the Invention] As described above, in the present invention, the correction means operates only when the sector mark signal and the total reflection area instruction signal are detected alternately. Even if 1. is stored, the operation of the correction means is stopped at that point, so that the error of the 1. racking error signal does not become large. Further, after the sector mark signal and the total reflection area indication signal are detected alternately in pairs, the correction means is operated after detecting the total reflection area indication signal or the sector mark signal or a pair thereof at least once. Therefore, the correction means operates after the storage means stores an accurate offset amount, and the tracking servo operation no longer operates abnormally.

Therefore, the tracking of the optical information recording/reproducing device has become stable.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a tracking servo circuit according to the present invention. FIG. 2 is a circuit diagram of the first signal testing means in FIG. 1. FIG. 5 is a circuit diagram of the second signal testing means in FIG. 1. FIG. 4 is a timing diagram of the tracking servo circuit of the present invention. Figure 5 shows the structure of a conventional tracking servo circuit...
......First signal inspection means......Second
Signal inspection means...Correction means...Storage means...Divided optical sensor...Detection means

Claims (1)

[Claims] a) A light beam spot focused on a recording medium of a disk is guided by a guide groove (track) provided in advance on the disk.
a tracking servo circuit that tracks the spot and track, b) a split-type optical sensor that receives reflected light or transmitted light from the recording medium; and c) differential amplification of the output of the split-type optical sensor to detect the spot and the track. d) detecting means for generating a tracking error signal indicating a relative positional deviation; and d) storing an offset amount of the tracking error signal according to a total reflection area indicating signal provided in advance on the disk and indicating an area without a track. storage means; e) first signal inspection means for inspecting that the total reflection area instruction signal and the sector mark signal are detected in alternating pairs; and f) the first signal inspection means. g) a second signal inspection means for checking whether a signal indicating the total reflection area indication signal or the sector mark signal or a pair of both signals is inputted at least once after the output becomes active; A tracking servo circuit comprising a correction means that corrects the tracking error signal based on the output of the storage means and switches whether or not to perform the correction operation based on the output of the second signal inspection means.