JPS6260139A - Corrector for detecting sensitivity of tracking error signal - Google Patents

Abstract

PURPOSE:To correct easily the detecting sensitivity of the tracking error signal by calculating the difference of error between both divided detection outputs given from a 3-beam pickup and driving this pickup so that said difference of phase is equal to zero. CONSTITUTION:The detection outputs given from detectors A and B are supplied to an adder 14 among those 4-split main detectors A'nD which receive the reflected light caused by a main beam. While the detection outputs of the detectors C and D are supplied to an adder 15. Then the detection outputs of both adders 14 and 15 are supplied to a phase difference detecting circuit 16. The DC output corresponding to the difference of phase given from the circuit 16 is supplied to an error amplifier 13. The output of the amplifier 13 is applied in such direction where said phase difference output is equal to zero against a motor 19 of a drive mechanism 18 which drives a 3-beam track 10 toward an arrow head B. Thus it is possible to correct the detecting sensitivity of the tracking error signal to the optimum level at all times during the reproduction of a track 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical disc reproducing device, and more particularly to a correction device for tracking error signal detection sensitivity using a three-beam pickup.

[Technical background of the invention]

Recently, optical disc playback devices have been commercialized that play back optical discs, such as CD grayers, on which information is recorded as pit rows with different light reflectances on spiral tracks. One main beam and two sub-beams are irradiated onto the disc as an optical big beam used in this type of playback device, and information components and fragments are extracted from the light reflected by the main beam among the reflected lights. A so-called three-beam pickup is known that detects a cass error component and also detects a tracking error component from light reflected by a pair of sub-beam lights.

In other words, this 3-piece pick-up! By irradiating the light beam from the light source onto the disk through the diffraction grating, the main beam light spot 7) M"::"' (as shown in Figure 3) is projected onto the center of the track. and a predetermined distance (0, 4, which is a distance of 1/4 of the track pitch of 1.6 μm in CD) on opposite sides of each other.
A pair of sub-beam light spots l'51tS2 are irradiated at a position offset by .mu.m). As shown in FIG.
A tracking error signal can be obtained by detecting with SD2 and extracting the difference with operational amplifier opi. Note that the reflected light from the main beam light spot M is divided into four components and detected by a four-split main detector MD, and information components (RF multiplied signals and 7-occurrence error signals can be obtained.

By the way, when the three-beam pickup is installed in an optical disc player, a pair of sub-beam optical spots (81) are installed so that the above-mentioned tracking error signal can be extracted with maximum sensitivity.

It is necessary to adjust S2 so that it can correctly irradiate the above-mentioned positional relationship.

For this reason, conventionally, the tracking error signal from the operational amplifier OP1 is supplied to the one-phenomenon waveform observation device CRT while the disk is rotated and focus serve is applied, and the waveform '5r: is observed, and the amplitude value is the maximum. By relatively adjusting the mounting position tt of the pickup and the mounting side, the above-mentioned three-beam light spot was adjusted so that the positional relationship was correctly arranged. In addition, so that this adjustment point does not change at each position in the radial direction of the disk,
It is necessary to substantially correct the tracking error signal detection sensitivity by moving the beam spot in a circle centered on the rotation center of the disk, that is, in a direction perpendicular to the tangential line of the track.

[Problems with background technology]

However, in the conventional adjustment method as described above, the angle of the diffraction grating deviates greatly from the optimum point within its variable range and ends up on the track <g4b as shown by the array line A in FIG. ．． In this case, two or more maximum amplitude points of the tracking error signal appear as shown in FIG. 5, making the correct adjustment position (angle) unclear.

For this reason, it has been considered to provide a mechanical stopper in advance for the purpose of limiting the angular variation range of the diffraction grating, but in reality, it is difficult to employ it due to structural problems.

In addition, in the conventional adjustment method, the tracking error signal is measured at two or three points in order to minimize changes in the detection sensitivity of the tracking error signal at each position in the radial direction of the disk. , which only corrects the tracking error detection sensitivity, is actually insufficient and complicated. Moreover, since the tracking servo operation must be interrupted each time,
It is impossible to even make this correction while actually playing a disc.

[Purpose of the invention]

Therefore, the present invention was made in view of the above points, and it is an optical disc playback device that detects tracking error signals using a three-beam pickup, and provides a method for easily and accurately correcting the detection sensitivity of tracking error signals to an optimal value. It is an object of the present invention to provide a correction device for tracking error signal detection sensitivity.

[Summary of the invention]

That is, the tracking error signal detection sensitivity correcting device according to the present invention reproduces an optical disc using a three-beam pickup, and calculates the level difference between each detection output from a pair of sub-detectors of the three-beam pickup. In an optical disc playback device in which a tracking sensor obtains a tracking error detection signal, a first means for taking a phase difference between detection outputs divided into two in a track tangential direction from a main detector of the three-beam pickup; , and a second means for driving the three-beam pickup in the direction of the track 5Hq so that the phase difference output by the first means becomes zero.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to the N-side.

That is, in FIG. 1, A-D and EF produce one main beam light spot and a pair of sub-beam source spots from a light source (not shown) via a diffraction grating or the like on the tracks of the optical disc 2Q in a predetermined arrangement as described above. A main detector and a sag detector are provided in a three-beam pickup 1o, which is configured to irradiate the beam with a beam and detect each of the reflected beams individually. As shown in the figure, the main detectors A to D have a first dividing line bisected in the direction of the track fluid gland, and a second dividing line that orthogonally bisects the first dividing line. It is divided into four parts and receives the reflected light component of the one main beam described above.

Normally, the main detectors A to D are used to detect an RF signal using the sum signal component of each of their outputs, and to calculate the RF signal to obtain an error signal. , not shown here. Further, the pair of sub-detectors E and F separately receive reflected light components from the pair of sag beams.

A pair of sub-detectors E each receive reflected light components from the pair of sub-beams.

Each detection output from F is used to obtain a tracking error signal by extracting a difference therebetween by an operational amplifier 12. This tracking error signal is normally supplied to a tracking serge system (not shown).

Also, among the detection outputs from the four-split main detectors A to D that receive the reflected light from the main beam, the detection outputs from the detectors A and B located on the left side as viewed in the track row direction are sent to the first adder. 14. Further, each detection output from the detectors C and D, which are also located on the right side, is supplied to the second adder 15.

And the above 1. Each addition output from the second adder 14, 15 is supplied to a phase difference detection circuit 16, and a DC output corresponding to the phase difference from this phase difference detection circuit 16 is supplied to the error loudspeaker 13.・This error The output of the amplifier 13 connects the three beams to the disk 2 as shown by arrow B.
The motor 9, which serves as a drive source for a drive mechanism 18 consisting of a rack and a pinion gear, etc., is provided so as to be movable in the direction of the liquid gland with respect to the track 0, and can be driven in a direction such that the phase difference output becomes zero. given in relation.

By the way, the above-mentioned 3-beam pickup 10 is attached to a predetermined part of the CD grayer main body (not shown) and is movable in the radial direction of the disc 2o as shown by the arrow C in the figure. In other words, the disc is rotated by a disc motor (not shown), and the above-mentioned
A foot servo system (not shown) based on a cass error signal and a toss kinder servo system based on a tracking error signal? system? In the driven state, the tracking error signal detection sensitivity correction device operates.

Such a tracking error signal detection sensitivity correction device can reliably correct even if the tracking error signal indicates that the beam array position deviates significantly from the optimal position as described above. . Additionally, the tracking error signal detection sensitivity can always be accurately corrected to the optimum value during three-beak reproduction so that the above-mentioned phase difference output becomes zero. That is, no matter how the beam array position deviates at each position in the disk radial direction, tJr, the main detector A as shown in FIG.

The point where the relative phase difference (time difference) (I) between the sum component of B and the sum component of main detectors C and D becomes zero is the point that gives the maximum point of the tracking error signal (II), or the beam array position is correct. Since the sensitivity correction device can automatically correct the fact that only one point is given only when a single point is given when the can be taken as a thing.

It goes without saying that the present invention is not limited to the embodiments described above and illustrated, and that various modifications and applications can be made without departing from the gist of the invention.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a tracking error signal detection sensitivity correction device according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is a conventional tracking error signal detection sensitivity correction device. FIG. 4 is a diagram showing a beam arrangement for explaining a method of adjusting signal detection sensitivity. FIG. 4 is a configuration diagram of the same conventional method. FIG. 5 is a waveform diagram showing a tracking error signal according to FIG. 4. 11...3 beam pickup, 20...disk, A-D...main detector, E, F...subdetector, 12...operational amplifier, 13...error amplifier 14.15. ... Adder, 16... Phase difference detection circuit, 18... 1 drive mechanism, 19... Motor. 1st illustration of Takehiko Suzue, patent attorney

Claims (1)

[Claims] An optical disc is reproduced by a 3-beam pickup, and a tracking error detection signal for tracking servo is obtained by taking the level difference between each detection output from a pair of sub-detectors of the 3-beam pickup. In the disc playback device, a first means for taking a phase difference between each detection output divided into two in a track tangential direction from a main detector of the three-beam pickup, and a first means for taking a phase difference between the detection outputs from the main detector of the three-beam pickup, and a phase difference output from the first means so that the phase difference output becomes zero. and second means for driving the three-beam pickup in a direction tangential to the rack.