JPH0434209B2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) The present invention relates to an optical information recording/reproducing device.

(Prior Art) Conventionally, as an optical information recording/reproducing apparatus using an optical disk having spiral or concentric tracks, an optical pickup optical system focuses a light beam onto the track to record information on the track. A method for reproducing recorded information is known.

Such a recording/reproducing apparatus requires focusing control to accurately focus the light beam spot onto the track, and tracking control to align the focus position of the light beam with the track. By the way, if the disk surface of the optical disk is tilted or warped, or if there is a misalignment in the optical system of the optical pickup, a steady offset will occur in the tracking control signal, making it difficult to perform tracking control properly. The problem is that there is no.

This problem will be explained in detail below using FIGS. 2 to 7.

FIG. 2 is a simple block diagram of a tracking servo system that performs tracking control. Reference numeral 1 denotes a tracking control light-receiving element that detects the deviation of the light beam in the tracking direction, and in this example, it is shown as being divided into two parts. Reference numeral 2 designates a subtracter for determining the difference between the outputs of the light receiving elements, 3 an actuator drive circuit including a phase compensation circuit, etc., and 4 an actuator for displacing the objective lens 5 in the tracking direction. Tracking control signal for the output of subtracter 2
It is called TES.

As mentioned earlier, an optical disk has tracks formed in a spiral or concentric pattern on the disk.
As shown in FIG. 3, tracks 7 for recording information appear on the optical disc 6 as irregularities.

FIG. 4 schematically shows the change in the amount of light on the light receiving element based on the relationship between the focusing position of the light beam and the track position. The amount of received light 9 changes, and the output of the subtracter 2 (tracking control signal
TES) changes from positive to negative. Figure a shows the case where the change is positive, and figure c shows the case where the change is negative. Figure b shows a case where the light beam is accurately focused on the track, and the tracking control signal TES becomes 0.

When the light beam enters the disk surface perpendicularly without any tilt, as the relative position between track 7 and light beam 8 changes, the center of the track and the middle of each track will become 0V as shown in Figure 5a. A roughly sinusoidal tracking control signal TES is obtained.
Since the tracking servo system controls the light beam position so that the tracking control signal TES becomes 0 near the center of the track, the light beam will normally be focused at the center of the track. However, if the light beam is not irradiated perpendicularly to the disk surface due to the inclination or warpage of the disk, the tracking control signal will not become 0V at the center of the track as shown in FIG. 5b, thereby causing an offset of Voff ₀ . Therefore, the light beam is focused at a distance of Xoff ₀ from the center of the track.

A similar phenomenon also occurs when an adjustment error occurs in the optical system of the optical pickup. FIG. 6 shows a case where the optical system is properly adjusted, and the center of the light beam 8 coincides with the center of the track 7, so that the amount of received light 9 is equally divided on each element j, k of the light receiving element 1. The tracking control signal TES, which is the output of the subtracter 2, becomes 0. As mentioned earlier, the servo system controls the light beam position so that the tracking control signal TES becomes 0.
In this case the light beam is controlled correctly to the center of the track. Next, if an adjustment error occurs in the optical system, an offset of Voff ₁ will occur in the tracking control signal TES even if the light beam is correctly focused on the center of the track as shown in FIG. 7a. If the servo system is operated so that the tracking control signal TES becomes 0, the center of the light beam will be focused at a distance of Xoff ₁ from the track center as shown in FIG. 7b. In this way, if the center of the light beam is focused away from the center of the track, not only will information not be recorded or reproduced correctly, but information such as sector numbers may be placed on one part of the track and not on other parts. With disks formed in different shapes, an abnormal spurt occurs in the tracking control signal TES when the light beam approaches the boundary between the two parts due to the difference in optical and physical properties between the two parts, which causes tracking to be delayed. Problems such as control becoming unstable may occur.

As a conventional technique related to this problem,
There is a technique disclosed in Publication No. 61925. This technology is
The above problem is solved by detecting the offset voltage that appears on the tracking control signal when scanning the optical beam across the track in order to access the target track on the optical disk, and subtracting this from the tracking control signal. This is what we aim to do. However, this method causes the following problems.

First, since the offset voltage is detected from the tracking control signal while the light beam is scanning to the target track, it is not necessarily possible to correct the warpage or inclination of the disk at the target track. This is particularly noticeable when scanning a large displacement such as from the inner circumference to the outer circumference of the disk.

Second, when recording and reproducing information repeatedly on the same track, it is impossible to cope with changes in the relative tilt of the disk and the light beam caused by disturbances.

(Purpose) Therefore, the present invention always corrects the light beam position in a desired track regardless of the amount of displacement during scanning or changes in the state of the disk and light beam due to disturbances, and easily and reliably controls tracking. The purpose of this invention is to provide a new optical information recording/reproducing device that can perform the following.

(Example) Examples of the present invention will be described below.

The optical information recording and reproducing apparatus according to the present invention has undergone technical improvements based on the following operating principle. That is, for example, when recording and reproducing information on a disk having spiral tracks, a jump between tracks may be performed in order to stay (stop at the same track) when accessing a desired track. Yes (see Figure 8).
The tracking control signal TES during this jump becomes as shown in Fig. 9, and at this time, the positive peak voltage V ₁
and 1/2 of the algebraic sum of the negative peak voltage _V2 gives the offset voltage Voff of the TES.

The configuration of an embodiment of the optical information recording/reproducing apparatus according to the present invention based on this operating principle is as shown in FIG. A tracking control signal TES is generated by calculating the difference between the outputs of each element j and k of the tracking control light receiving element 1 using a subtracter 2. 10 and 11 are peak voltage detection circuits, each of which receives a tracking control signal.
Detects the positive and negative peak voltages of TES. Reference numeral 12 denotes an adder that calculates 1/2 of the algebraic sum of the positive and negative peak voltages, and thereby detects the offset voltage Voff of the above-mentioned tracking control signal TES. 13
is a holding circuit that holds this offset voltage Voff. 14 is this held offset voltage
This is a subtractor that subtracts Voff from the original tracking control signal TES, resulting in an output _TES0 . A timing generation circuit 15 generates a timing control signal for the peak voltage detection circuits 10, 11 and the offset voltage holding circuit 13 at the time of track jump (when a jump signal is generated). FIG. 11 shows signal waveforms at each part. This subtractor 14
By driving the actuator 4 through the drive circuit 3 with the output TES 0 _{of 0} and displacing the objective lens 5, the light beam is corrected to be accurately focused at the center of the track, and the above-mentioned disadvantage does not occur. Here, the offset voltage holding circuit 13 updates the offset voltage held when performing a jump between tracks.

(Effects) According to the method of the present invention, in order to correct the offset in the track where information is actually recorded/reproduced at the time of track jump, it is possible to correct the warpage/inclination at each position in the radial direction of the disk and the temporal optical system. It becomes possible to accurately focus the light beam on the track even when there is an adjustment error. Furthermore, if the offset is corrected every time the track jump is performed, it is possible to cope with subtle adjustment deviations of the optical system, and control accuracy is further improved. Even in a disk having concentric tracks, information can be recorded between adjacent tracks as shown in FIG.
When playback is performed, a jump is performed when moving to any track, and offset correction is optimally performed for each track. Therefore, the advantages described above remain unchanged. Of course, the above-mentioned correction does not necessarily need to be performed for each track jump, and may be performed depending on the situation.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of an embodiment of the optical information recording/reproducing apparatus according to the present invention, FIG. 2 is a schematic block diagram of a conventional tracking servo system, FIG. 3 is an explanatory diagram of an optical disk, and FIG. 4 is a schematic block diagram of a conventional tracking servo system. An explanatory diagram to explain the principle of tracking control. Figure 5 is an explanatory diagram to explain how the inclination of the disk causes poor tracking control. Figures 6 and 7 are diagrams to explain how misalignment of the optical system causes tracking control. Figure 8 is an explanatory diagram to explain the path of the light beam during stay operation on a disk with spiral tracking. Figure 9 is an illustration of tracking during track jump. FIG. 10 is a signal waveform diagram showing the waveform of the control signal TES, FIG. 10 is an explanatory diagram showing the path of a light beam on a desired track in a disk having concentric tracks, and FIG. 11 is a timing waveform diagram of the operation of each part. In the figure, 1... light receiving element for tracking control, 2
...Subtractor, 3...Actuator drive circuit, 4
...Actuator, 5...Objective lens, 6...
Optical disk, 7... Track, 8... Light beam,
9... Amount of light received (light beam reflected on the disk surface), 10... Positive peak voltage detection circuit, 11...
Negative peak voltage detection circuit, 12...1/2 adder,
13...offset voltage holding circuit, 14...subtractor, 15...timing generation circuit.

Claims (1)

[Scope of Claims] 1. An optical information recording and reproducing device that records information or reproduces recorded information by focusing a light beam onto a recording track of an optical disk in which tracks are formed in a spiral or concentric pattern. A light beam driving means for performing a track-to-track jump for the purpose of stalling operation on a specific track, a detection means for detecting an offset voltage appearing in a tracking control signal at the time of the track-to-track jump, and the above-mentioned detection means A holding means for holding an offset voltage newly detected by the detection means in place of the currently held offset voltage at the time of a track-to-track jump for detecting an offset voltage; and a record of information on the offset voltage held by the holding means. Alternatively, an optical information recording/reproducing method characterized by comprising a subtracting means for subtracting from a tracking control signal during reproduction, and a servo system driving means for controlling the position of the light beam based on an output signal of the subtracting means. Device. 2. The optical information recording and reproducing apparatus according to claim 1 or 2, wherein the detecting means detects the offset voltage every time a jump between tracks is performed. 3. The detection means detects the positive and negative peak voltages of the tracking control signal by the control signal from the timing generation means which generates a new timing control signal in response to the control signal from the optical beam drive means that performs the jump between tracks. A detection means for detecting during the track-to-track jump and 1/1/2 of the algebraic sum of the positive and negative peak voltages that are the output of this detection means.
2. The optical information recording and reproducing apparatus according to claim 1, further comprising an output means for outputting a voltage of 2. 4. An optical information recording and reproducing apparatus according to claim 3, wherein said timing generating means generates a control signal to said detecting means every time a jump between tracks is performed.