JPH0630159B2 - Optical information recording / reproducing device - Google Patents

Description

The present invention relates to an optical information recording / reproducing apparatus for an optical video disc, a digital audio disc, or the like.

[Conventional technology]

In recent years, optical information recording / reproducing devices such as optical video discs and digital audio discs have become widespread. In such an optical information recording / reproducing apparatus, a disc as an information recording medium is irradiated with light such as laser light to record / reproduce information. FIG. 3 schematically shows a state in which a laser beam or the like is applied to the disc. That is, in the figure, 1 is a disk, 2 is a track formed on the disk 1 in a spiral or concentric shape, and 3 is a spot formed as a result of irradiating the disk 1 with a laser beam or the like. The spot 3 is tracking-controlled by a tracking control means (not shown) so as to follow the track 2. Further, the spot 3 is always focused on the track 2 (disk 1) by a focus control means (not shown). Then, the information recorded on the track 2 is reproduced by the reflected light of the light applied to the disk 1, the synchronizing signal and the like are separated and extracted from the reproduced signal, and the rotation of the disk 1 is controlled by the spindle control means (not shown). It has become.

For example, when the focus servo loop is locked in at startup, when the pickup (not shown) is gradually moved closer to the disc 1, the diameter D of the spot 3 gradually decreases from a large value and becomes the minimum at the focus position. Although it becomes large again as it approaches the disk 1, it becomes a value near the minimum value after the focus servo locks in, and this value does not change greatly as long as the focus servo operates normally.

The diameter D of the spot 3 at the in-focus position is preferably small in order to increase the recording density, but if it is too small, the level of the reproduction signal also becomes small, so there is a limit to making it small. Also, if it is made larger (especially if the pitch of the track 2 is set to p and it is made larger than the length 2pt), the crosstalk from the adjacent track 2 is increased by that much, and therefore it cannot be made too large. Therefore, the value of the diameter D of the spot 3 is generally set to be equal to or slightly larger than the width t of the track 2.

[Problems to be Solved by the Invention] As described above, in the conventional device, the diameter D of the spot 3 is
Is set to a value equal to or slightly larger than the width t of the track 2, so that, for example, when the tracking servo loop is turned off or when the tracking servo loop remains on, the search or scan is performed. In the case of forcibly moving the pickup in the radial direction of the disc 1 for operation, not only when the spot 3 is located on the track 2 as shown by the solid line in FIG.
As shown by the broken line, the time for positioning between tracks becomes long, and during that time, the reproduction RF signal cannot be obtained, or even if it is obtained, the level becomes extremely low, and there is a drawback that dropouts occur frequently. Further, as a result, the synchronization signal required for spindle control cannot be obtained, and the spindle servo is disturbed.

[Means for solving problems]

FIG. 1 shows a block diagram of an optical information recording / reproducing apparatus of the present invention. In FIG. 1, reference numeral 11 denotes a light receiving element for receiving the reflected light from the disk 1, for example, a focus servo by a so-called astigmatism method. 4 if done
It is divided. The outputs of the diagonally arranged elements of the four-divided light receiving element 11 are added by adders 12 and 13, and then added to the inverting and non-inverting input terminals of the operational amplifier 16 via the addition resistors 14 and 15. Each is input. An adder 17 adds the outputs of the adders 12 and 13. The operational amplifier 16 has its output terminal and inverting terminal connected via a feedback resistor 18, and its non-inverting terminal is grounded by a resistor 19 to form a differential amplifier 20. The difference signal (focus error signal) between the outputs of the adders 12 and 13 output from the differential amplifier 20 is supplied to the focus motor 23 via the equalizer 21 and the buffer amplifier 22. 24
Is, for example, monitoring the level of an input tracking error signal, or monitoring a signal from a control means such as a microcomputer (not shown) to detect ON / OFF (close, open) of the tracking servo loop, It is a detection means for detecting a search or scan operation. The output of the detection means 24 controls the on / off of the switch 25. Reference numeral 26 is a potential generator that generates a predetermined potential such as a battery, and is a switch 25.
When is turned on, a predetermined potential is applied to the inverting terminal of the differential amplifier 20 via the resistor 27.

[Action]

Then, the operation will be explained. The disk 1 is irradiated,
The reflected light is incident on the light receiving element 11 via an astigmatism generating means (not shown) such as a cylindrical lens. A differential signal of the signals added by the adders 12 and 13 among the four outputs of the light receiving element 11 is obtained by the differential amplifier 20, and the focus error signal is passed through the equalizer 21 and the buffer amplifier 22. Is supplied to the focus motor 23, and the focus motor 23 drives an objective lens (not shown) or the like to adjust the distance between the objective lens and the disc and control the in-focus state. On the other hand, as shown in FIG.
A tracking servo loop (not shown) operates so that the upper spot 3 follows the track 2. Therefore, the addition output of the adders 12 and 13 is obtained from the adder 17, and the RF signal can be obtained from this addition output. A predetermined information signal is demodulated from this RF signal, and a synchronization signal and the like are separated and supplied to a spindle servo circuit (not shown) to control the rotation of the disk 1. In this way, the normal reproduction operation is performed.

In such a state, for example, when the tracking servo loop is turned off or a search or scan operation is instructed due to some cause, the detection means 24 detects this and turns on the switch 25 which has been turned off until now. To do. As a result, the potential output from the potential generator 26 is the resistance 27.
Is applied to the differential amplifier 20 via the, and an offset is given to the output of the differential amplifier 20. Therefore, the focus servo is applied at a position where the distance between the objective lens and the disc 1 is slightly deviated from that in the focused state, and the spot 3
The diameter D is larger than that in the focused state.

This will be described with reference to FIG. When the distance between the objective lens and the disc 1 changes, the focus error signal changes as shown in FIG. That is, when the objective lens gradually approaches the disc 1 from a position away from the position A,
A positive focus error signal starts to appear in the position B, peaks at the position B, decreases thereafter, becomes substantially zero at the position C (focus position), then becomes negative at the position D, peaks at the position E, and becomes zero again. . It has a so-called S-shaped characteristic. The diameter D of the spot 3 is the smallest at the position C (focus position), and is larger on the position B side or the position D side than that. The offset value (potential) is adjusted and set so that the objective lens is located between the position B and the position D with respect to the disc 1. If the offset is larger than that, the focus servo may be unlocked when the offset is given.

When the diameter D increases, the RF signal can be reproduced from the left and right tracks 2 even when the spot 3 is located between the tracks, and the sync signal and the like can be separated from it.
It can be supplied to the spindle servo circuit. Therefore, even if the tracking servo loop is turned off, the possibility that the spindle servo loop will malfunction will be reduced.

〔effect〕

As described above, in the present invention, when the focus servo loop is locked (turned on) and the spot on the disk may be located between the tracks, the focus servo loop is set so that the spot becomes large. Since the offset is applied, the RF signal can be reproduced even when the spot is located between the tracks, and the synchronization signal and the like can be extracted from the RF signal to prevent the time axis servo such as the spindle servo from malfunctioning. Can be prevented. Further, since the offset is canceled during normal reproduction, crosstalk does not increase.

[Brief description of drawings]

FIG. 1 is a block diagram of an optical recording / reproducing apparatus of the present invention, FIG. 2 is a characteristic diagram of a focus error signal thereof, and FIG. 3 is a plan view schematically showing a state of a spot on a disc. 1 ... disk, 2 ... track 3 ... spot, 11 ... light receiving element 12, 13, 17 ... adder 20 ... differential amplifier, 21 ... equalizer 22 ... buffer amplifier 23 ... focus motor 24 ...... Detection means 25 ...... Switch 26 ...... Potential generator

Claims (3)

[Claims] 1. An optical information recording / reproducing apparatus for irradiating light emitted from a light source onto an information recording medium to record / reproduce information, the detecting means detecting a focus state of light irradiating the information recording medium, Focus control means for controlling the focus state of the light on the information recording medium in response to a focus error signal from the detection means, and offset means for offsetting a signal supplied to the focus control means A first focus is on the information recording medium without applying the offset by the offset means when a focus servo loop including the detecting means and the focus control means is turned on, From the position where the light is focused on the information recording medium, It is possible to control switching to the second state are shifted interference, an optical information recording and reproducing apparatus characterized in that it is switched to the second state when the tracking servo loop is turned off. 2. An optical information recording / reproducing apparatus for irradiating an information recording medium with light emitted from a light source to record / reproduce information, and detecting means for detecting a focus state of light irradiating the information recording medium. Focus control means for controlling the focus state of the light on the information recording medium in response to a focus error signal from the detection means, and offset means for offsetting a signal supplied to the focus control means A first focus is on the information recording medium without applying the offset by the offset means when a focus servo loop including the detecting means and the focus control means is turned on, From the position where the light is focused on the information recording medium, NOTE deviation is a possible second state and the switching control, optical information recording and reproducing apparatus characterized in that it is switched to the second state during the scan or search operation. 3. The optical system according to claim 1 or 2, wherein the offset is set to a value between a positive peak and a negative peak of the focus error signal. Information recording / reproducing apparatus.