JPS63231731A - Track jumping method for optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain the optimum timing of a servo application by detecting the level when a main beam intersects a guide track in the blind sector period of an S curve by the guide track and applying a deceleration pulse. CONSTITUTION:The S curve formed with two sub-beams has a waveform connected by the blind sector NSB where the main beam intersects the guide track GT and the S curve periods are found by the comparison of a zero-cross comparator ZX with the current position (f) of a sub-beam; when a servo is added at a point (g) a waveform detected by a window comparator WC, the zero-cross signal waveform of the S curve, and the detected level waveform when the main beam intersects the guide track are timed respectively. Therefore, when the main beam intersects the track guide during the movement of an objective lens, a pulse signal is generated in the NSB and a deceleration current is supplied to an actuator on the boundary of an adjacent track. Consequently, the main beam is focused on the intermediate point of the guide track.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a control method suitable for jumping the tracks of an information recording medium provided with a guide track such as an optical card that records and reproduces digital information using a laser beam. Regarding.

``Prior Art'' In optical recording media, such as compact discs, there is a difference between the center of the track where information is recorded and the center of rotation of the disc, or eccentricity, and the error of the playback device is about 200 microns, so the information bit pattern trunk is There will be a deviation of about 200 microns left and right, and the optical pickup will cause a difference of 1
Stable signal detection has become an important technology for accurately tracing tracks at 6 micron intervals.

Therefore, the accuracy of signal detection is to control the parallel movement of the objective lens left and right with an error of more than 1/10 of the track width, that is, less than 0.1 micron, but this tracking error signal indicates which direction to move, left or right. The three-spot method shown in FIG. 2 is generally known as a method of detecting this.

In this three-spot method, a laser beam B is applied to the diffraction grating 1 using a main laser spora (M) for detecting the signal and a focusing error signal, and two sub-laser spora (S) for detecting focusing error. -The sub-laser spot for extraction is placed with the main laser spot slightly shifted from front to back and left and right on the track where the pits are lined up.
The reflected light enters the photodetector 2 through the same optical path as the main laser.

If the main laser spot is tracing the track accurately, the output of the two sub-laser spots will be equal, and if the main laser spot shifts to the left, the sub-laser spot S2 will enter between the tracks and its output will become thicker. Shifts to the right and the sub-laser point S1 increases its output.

The left and right outputs of the photodetector are applied to an error amplifier 3, from which a tracking error signal is extracted.

Therefore, in order to find the track on which specific information is recorded, in order to make the optical pickup jump inward or outward from the current position of the main spot, we need to control the tracking actuator. This is done by adding (acceleration) and negative (deceleration) jump command pulse signals.

Optical cards are not rotated like compact discs (they record and reproduce information by reciprocating the head containing the laser light source in a straight line), and when changing tracks, they must be moved across the guide track. The only difference is in what they do.

Therefore, when reproducing information from a conventional optical card, there is a dead zone due to the guide track in the waveform of the tracking error signal, that is, the S curve, as seen from the graph in FIG. 1(a). In addition to not being able to obtain a negative-direction inversion signal using the zero-crossing method, the timing of applying the servo was difficult.

``Means for Solving the Problems'' However, the present invention solves the above-mentioned difficulties by determining the servo application timing by the zero-crossing method during the S-curve period, and when the main beam crosses the guide track during the dead zone period of the S-curve due to the guide track. By detecting the level of , a deceleration pulse is added to obtain the optimum timing for applying the servo.

Embodiment The servo application pattern at the time of trunk jump according to the present invention will be described in detail below with reference to the timing chart shown in FIG.

First, Fig. 1 (a) shows the tracking error signal waveform (S curve) by the Zabu beam, and Fig. 1 (b) shows the comparative output liquid form by the wind comparator for the S curve. The comparison output pattern by the zero cross comparator, and (d) in the same figure is the level detection output pattern of the main beam.

The optical card reader/writer (recording/playback device) has a guide track on the recording surface of the card to apply servo to the actuator, and information pits are recorded and formed between the track guides by the main beam in the middle. . The area of the pit is wider than the width of the guide track.Therefore, as shown in Figure 1(a), the S-curve formed by the two sub-beams is connected by a dead zone (NSB) where the main beam crosses the guide track. The S-curve period is determined by comparison using the zero-cross comparator at the sub-beam's current position (a), and if the servo is added at point (b), the peak value of the S-curve as shown in the figure (b) is determined by the window. The waveform detected by the comparator and the zero-crossing signal waveform of the S curve in the same figure (C) and the same figure (d)
) The detection level waveforms when the main beam crosses the guide track correspond to each timing.

Therefore, when one trunk is to be jumped, Figure 1 (
Assuming that point (a) in a) is the current position, when the main beam crosses the track guide while applying an accelerating current to the actuator and moving the objective lens, it will move to point (d) in the same figure.
), a pulse signal is generated during the dead zone period of the S curve, and this period becomes a switching point at which the deceleration current flows into the actuator at the boundary with the adjacent l/rack. Then the same figure (1
))) After the window comparator output becomes II'' and further reverses to 'L'', the switching point of the zero cross comparator output corresponds to the servo application point of the adjacent trunk, that is, point (b) in (a) of the same figure, and at this time The actuator speed is close to zero (the main beam is focused in the middle of the guide track and is drawn into the lock range of the servo system).

FIG. 3 shows the above system.

``Effect'' (According to the present invention, even if there is a dead zone period in the tracking error signal of the sub-beam, the point outside the servo pull-in area can be determined by detecting the peak of the S curve, and the optimum servo application can be determined by detecting the zero cross. By detecting the main beam cross-guide track level, the actuator acceleration/deceleration point in the dead zone can be accurately determined.
The servo application timing after a jump becomes accurate, and stable control without overshoot or undershoot is possible, and the CPU can easily judge the operation, which has great practical benefits.

[Brief explanation of drawings]

Figure 1 is a servo application timing chart during tracking jump. Figure 1 (a) shows the tracking error signal waveform due to the sub-beam, Figure 1 (b) shows the S-curve wind comparator comparison output waveform, and Figure 1 (c) shows the S-curve comparison output waveform. The zero-cross comparison output waveform, Figure (d) is the level detection pulse waveform when the main beam crosses the guide track, and Figure 2 is an optical system diagram explaining the three-spot method of a conventional optical recording information reproducing device. 3ωltL force ~ 1 leak/Uzuri ^ On the first light map. NSB... Dead band, PIA... Pull-in area, 1... Diffraction grating, 2... Photodetector, 3... Error amplifier, 4...
...Beam flinter, L, DET...Level detector, WC...Window comparator, ZX...Zero cross comparator, GT...Guide track, M...
・Main laser spot, S) IS2...Sub laser spot.

Claims (1)

[Claims] A laser light source is emitted from an information recording medium in which a plurality of guide tracks are provided on at least one surface of a carrier on which information is to be recorded, parallel to each other and at regular intervals, and information is recorded by pits between each guide track. In a track jump operation of an optical information recording and reproducing apparatus that records and reproduces the above information based on a three-beam method using a main beam spot and two sub-beam spots from a head including a main beam spot and two sub-beam spots, When the head moves, the peak value of the tracking error signal is detected via a window comparator, and an accelerating current is supplied to the actuator to move the objective lens toward the adjacent track, thereby determining the level at which the main beam crosses the guide track. The optical information recording and reproducing apparatus is characterized in that the actuator is controlled so that the objective lens is held in the middle between the guide tracks by detecting the current and switching to a deceleration current until the boundary reaches the adjacent track. How to track jump equipment.