JP2693608B2 - Information recording disk playing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an information recording disk playing device.

BACKGROUND ART The recording density of an information recording disk (hereinafter, simply referred to as a disk) is determined by a pitch of recording tracks (hereinafter, simply referred to as a track pitch), and the track pitch is predetermined as a standard. Therefore, the disc playing device is adjusted so that a disc having a predetermined recording density can be played. For this reason, the conventional disc playing device cannot cope with discs having a track pitch other than the prescribed one.

On the other hand, recently, the densification of disks is being promoted,
With the development of a disc having a recording density higher than the current recording density, track pitches of a plurality of standards will exist. In this case, the conventional disc playing device cannot play discs having different recording densities (track pitches), and a countermeasure against it is desired.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an information recording disc playing device capable of playing discs having different recording densities (track pitches) by the same device.

[Structure of the Invention] An information recording disk playing device according to the present invention is designed to detect a recorded information reading spot from an information recording surface based on a pair of preceding and following tracking information detecting spots in relative movement with respect to the disk. A pair of photoelectric conversion means for receiving the reflected light respectively are provided, and a tracking error signal corresponding to the deviation amount of the recording information reading spot with respect to the recording track of the disk in the disk radial direction based on each output of the pair of photoelectric conversion means. And an information recording disk playing device including a tracking servo loop for controlling the recording information reading spot to be biased in the disk radial direction based on the tracking error signal. Spot for disc radius The track pitch detecting means is provided for detecting the track pitch of the disk based on the phase difference between the outputs of the pair of photoelectric conversion means when the disk is moved in the opposite direction.

[Operation of the Invention] In the information recording disk playing device according to the present invention,
In the open state of the tracking servo loop, while moving the recording information reading spot in the disk radial direction, the output positions of the pair of photoelectric conversion means that respectively receive the reflected light from the information recording surface based on the pair of tracking information detecting spots. The track pitch of the disc is detected based on the phase difference.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, three beam spots obtained by converging a laser beam, namely, a recording information reading spot S ₁ and a pair of preceding and following tracking information when the spot S ₁ moves relative to the disk in the rotational direction, respectively. The detection spots S ₂ , S ₃ are irradiated onto the recording track T of the disc from a pickup (not shown) in a positional relationship shown in the figure. The reflected light from the disk surface due to these beam spots enters the photoelectric conversion elements 1 and 2 and 3 built in the pickup.

The photoelectric conversion element 1 is composed of a so-called four-segment photodetector,
The sum of the four outputs becomes the read RF (high frequency) signal. On the other hand, the respective outputs of the pair of photoelectric conversion elements 2 and 3 are supplied to the differential amplifier 4 to derive the difference between the two outputs, and the difference output (S ₂ −
S ₃ ) becomes the tracking error signal. When the recording information reading spot S ₁ moves from _one recording track T ₁ to an adjacent storage track T ₂ as shown in FIG. 2 (A), the tracking error signal (S ₂ -S ₃ ) shows As shown in B), the waveform becomes a sine wave, the signal level of which is proportional to the deviation amount of the recording information reading spot S _{1 from} the recording track T, and the zero cross point is at the center position of the recording track T and the adjacent track T ₁ , T ₂ respectively correspond to intermediate positions.

The tracking error signal has its frequency and phase characteristics compensated by the equalizer 5 and is supplied to the loop switch 6. The tracking error signal passed through the loop switch 6 is supplied to the tracking actuator 9 via the adder 7 and the drive circuit 8. This tracking actuator 9
Is an action to bias the disk radial direction in accordance with the spot S ₁ to allowed to accurately follow the recording information reading spot S ₁ to the recording track T in the tracking error signal level. Thus, a tracking servo loop is formed.

The controller 10 controls ON (close) / OFF (open) of the loop switch 6. When the loop switch 6 is in the ON state, the tracking servo loop is in the closed state, and in this loop closed state, the tracking servo is performed according to the tracking error signal level. The controller 10 turns off the loop switch 6 at the time of low-speed rotation such as the start of disk rotation, and issues a start command to the drive voltage generation circuit 11. In the loop open state in which the loop switch 6 is in the off state, in order to move the recording information reading spot S ₁ at a constant speed, for example, from the inner circumference of the disc toward the outer circumference in response to a start command from the drive voltage generation circuit 11. A driving voltage is generated, and this driving voltage is added to the adder 7
And the tracking actuator 9 via the drive circuit 8.
Is applied to

In this example, by applying a drive voltage to the tracking actuator 9, the spot for reading recorded information is read.
Although S ₁ is moved in the disc radial direction, the recording information reading spot S ₁ is applied by applying a drive voltage to a drive source of a carriage (not shown) that carries a pickup and is movable in the disc radial direction. Can be moved in the radial direction of the disk.

The outputs of the pair of photoelectric conversion elements 2 and 3 are the phase difference detection circuit 12
Is also supplied. The phase difference detection circuit 12 includes, for example, as shown in FIG. 3, waveform shaping circuits 21 and 22 for shaping the outputs of the pair of photoelectric conversion elements 2 and 3, and these waveform shaping circuits 21 and 22.
Each of the outputs of 2 is input as an exclusive OR circuit 23, and an LPF (low-pass filter) 24 for converting the pulse width of the output pulse of the exclusive OR circuit 23 into an analog voltage. A phase difference signal having a level corresponding to the phase difference between the outputs of the photoelectric conversion elements 2 and 3 is output. This phase difference signal becomes the comparison input of the comparator 13. Comparator 13
Has a reference level Vr set corresponding to a track pitch of, for example, 1.2 μm. By comparing the phase difference signal level with the reference level Vr, the track pitch of the disc It is determined whether the type is 1.6 μm (large phase difference) or 0.8 μm (small phase difference). The determination result is supplied to the controller 10 as track pitch information. Based on the track pitch information, the controller 10 controls various switching such as servo gain, disk rotation speed, and signal processing system.

Here, the principle of detecting the track pitch based on the phase difference between the outputs A and B of the pair of photoelectric conversion elements 2 and 3 will be described.

4, the track pitch is p, the distance between the recording information reading spot S ₁ and the pair of tracking information detecting spots S ₂ and S ₃ in the disk radial direction is d, and each of the photoelectric conversion elements 2 and 3 is If the amplitude of the outputs A and B is E and the moving speed when the recording information reading spot S ₁ is moved in the disk radial direction is v, then the outputs A and B of the photoelectric conversion elements 2 and 3 are
Is It is expressed as Further, the phase difference θ between the outputs A and B of the photoelectric conversion elements 2 and 3 is It is expressed as

Here, if the distance d is constant, as is apparent from FIG. 5 showing the relationship between the phase difference θ and d / p, the photoelectric conversion element 2,
The track pitch p can be obtained from the phase difference θ of each output of 3.

As described above, according to the method of detecting the track pitch p from the phase difference θ between the outputs of the photoelectric conversion elements 2 and 3, the recording information reading spot S ₁ is less likely to be affected by the speed v across the recording track. It is possible to detect the track pitch with high reliability.

As described above, in the information recording disk playing device according to the present invention, the disk based on the pair of tracking information detecting spots is moved in the disk radial direction while the recording information reading spot is moved in the open state of the tracking servo loop. The track pitch of the disk is detected based on the phase difference between the outputs of the pair of photoelectric conversion units that receive the light reflected from the surface, and the track pitch is detected without adding a special sensor. Since various kinds of switching can be automatically performed, disks having different recording densities (track pitches) can be played by the same device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a relationship between a moving position of a recording information reading spot S ₁ with respect to a recording track and a tracking error signal level, and FIG. FIG. 4 is a block diagram showing an example of a concrete circuit configuration of the phase difference detection circuit in FIG. 4, and FIG. 4 is a moving position of the recording information reading spot S ₁ and the pair of tracking information detecting spots S ₂ and S _{3 in} the radial direction of the disc. And the output waveforms M, A, and B of the photoelectric conversion elements 1 to 3, and FIG. 5 is a characteristic diagram showing the relationship between the phase difference θ and d / p. Description of symbols of main parts 1-3 ... photoelectric conversion element 6 ... loop switch 9 ... tracking actuator 10 ... controller 12 ... phase difference detection circuit

Claims (1)

(57) [Claims] 1. A pair of pair of receiving light reflected from an information recording surface based on a pair of preceding and following tracking information detecting spots, respectively, when the recording information reading spot is moved relative to the information recording disk in the rotational direction. It has a photoelectric conversion means, and generates a tracking error signal according to the deviation amount in the disk radial direction of the recording information reading spot with respect to the recording track of the information recording disk based on each output of the pair of photoelectric conversion means, An information recording disk playing device including a tracking servo loop for controlling the recording information reading spot to be biased in the disk radial direction based on the tracking error signal. Move the spot in the radial direction of the disc An information recording disk playing device comprising track pitch detecting means for detecting a track pitch of the information recording disk based on a phase difference between outputs of the pair of photoelectric conversion means when the information recording disk is moved.