JPS58158044A - Recording and reproducing system of optical disc - Google Patents

Abstract

PURPOSE:To compensate errors in detecting the focus deviation occuring in the difference in the intensity of reflected light between the recording stage and reproducing stage, etc., by deciding the ratio between the difference in the quantities of the light detected in divided photodetectors and the total quantity of detected light as the final result of the detection of the focus deviation. CONSTITUTION:When beam light is correctly focused onto an optical disc 11 and has no deviation in focus, the incident pattern of the reflected beam formed on the photodetecting surface of a photodetector 22 is a circular pattern, but when a deviation in focus arises, said pattern forms a deformed pattern extending in a vertical or horizontal direction. The respective output signals A-D of the photodetector 22 are supplied to adding amplifiers 241, 242, a difference detecting circuit 25, a ratio operating circuit 27, etc., whereby the ratio between (A+C)- (B+D) and (A+B+C+D) is calculated. The result of the calculation is supplied to a driving circuit 28, by which the position of an objective lens 18 is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a recording and reproducing system for an optical disc in, for example, an optical storage device, in which information is recorded or reproduced by irradiating a beam of light onto a rotating optical disc.

[Technical background of the invention]

In general, optical disks are high-density information recording media that use LED light, and optical storage devices using them have recently attracted a lot of attention as information memories with unprecedented large capacity. This type of optical storage device, which is being considered for application in file devices, rotates an optical disc on which recording tracks are pre-formed in advance by pre-groups on its surface in a serpentine shape, and produces a single radar beam. By alternately switching the light between the reproduction beam light and the recording beam light, the reproduction beam light is used to track the pre-group L, and therefore, the recording beam light is used to form data bits corresponding to the recorded information on the pre-group. When information is recorded and the returned information is played back, data bits are formed using the 9 preglue function. , t, b The information is reproduced by detecting data bits while tracking the recording tracks with a reproduction beam light.

However, in such an optical storage device, the width of the recording track formed on the optical disk is approximately 1 mm, and an objective lens is used to cover such a very narrow recording track. The beam light is focused
Therefore, on the optical disk there is always about 1-.$11
It is necessary to perform accurate focusing to obtain a single spot.

However, optical discs usually have slight scratches, variations in eccentricity or thickness, and vibrations in the optical system, so the relationship between the recording track on the optical disc and the objective lens may be affected. Distance fluctuations occur in the threshold. If such fluctuations occur even slightly, the beam light will be out of focus on the optical disk, making it impossible to always accurately focus the beam light. This has an adverse effect on the recording or playback of the image, causing recording gaps or playback gaps, making accurate recording or playback impossible. A focus control method is used in which the distance between the optical disk and the objective lens is always kept constant by optically detecting it and moving the objective lens accordingly.
A typical example is the astigmatism method (%
No. 4539) is known. This is a method in which light reflected from above on an optical disk based on a recording beam light and a reproduction beam light is irradiated onto a multi-segmented light receiver 1 as shown in FIG.
The four square-shaped light-receiving elements arranged in the receiver IK are the output cams of Is elbe1@* Id e B * C
e D detects changes in the shape of the reflected beam light, uses this change in shape to detect changes in the distance between the optical disk and the objective lens, and uses this detection signal to move the objective lens. In the astigmatism method, the shape change of the reflected beam light is
Add the outputs A and C of the light receiving element Ill e Je (A+
C) L, and light receiving elements Jb located at mutually symmetrical positions,
The outputs B and D of 14 are regarded as addition (BAD)L, and the difference between these addition results @(M+C)-(BAD).

[Problems with background technology]

By the way, in an optical storage device that performs recording and reproduction, the recording beam light forms a data beam on the optical disk (ToJ) - Therefore, the energy of the recording beam light is set to be at least 10 times the energy kaf of the reproduction beam light. Therefore, the intensity of the reflected beam light generated during recording is much larger than the intensity of the main reflected beam light during playback, and the shape change of the reflected beam light during playback is an absolute value "( A+C
) - (BAD)", then the shape change of the reflected beam light during recording is the absolute value "K(A+C)".
-K(BAD)" - In this case, the magnitude of K is about dK)3 - In other words, the detected value of distance variation between the optical disk and the objective lens is large between recording and playback. This results in a shift, which has the drawback that accurate focus control cannot be performed and reliable recording and reproduction of information cannot be performed.

[Purpose of the invention]

This invention was made in view of the above circumstances,
The purpose is to provide an optical disk recording and reproducing system that enables reliable recording and reproducing of information without causing a focus shift or track shift of the beam light on the optical disk.

[Summary of the invention]

In this invention, reflected light from a recording medium is irradiated onto a plurality of divided light receiving means, and when detecting a defocus or deviation based on the difference in the amount of light received by each light receiving means in the light receiving means, the amount of light received is detected. By dividing the difference by the total amount of light received by the receiver, and using the ratio of the difference in the amount of light received as a result of this division to the total amount of light received as the final defocus detection result or track deviation detection result), during playback. This book compensates for defocus detection errors or tracking error detection errors caused by differences in the intensity of reflected light between recording and recording.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, 11 is an optical disk (optical recording medium),
On its surface (lower surface in the figure), recording tracks are pre-recorded with 71 rows of pre-glue. It is formed in an irral shape (concentric circles). Reference numeral 12 denotes a motor for rotationally driving the optical disk 11, and 13 an optical system for recording and reproducing.The optical disk 110 is linearly moved in the radial direction by a linear motor mechanism (not shown). The optical head 13 includes a semiconductor radar oscillator 14, a collimator lens 151, a polarizing beam splitter 16, a λ/4 plate 11. an objective lens 18; a driving girth coil 19 for moving the objective lens in a direction perpendicular to the surface of the optical disk 11; and a cylindrical lens) eXO.

It is composed of a condensing lens 21, a 4-split light receiver 22, and the like. That is, the Rade oscillator 14 is driven and controlled by the drive circuit 23, and its output light beam is configured to be switched into two beams: a reproduction beam light and a recording beam light having stronger energy. Therefore, the beam light from the Rade oscillator 14 is transmitted to the collimator v
The beam is collimated at y and e 15, and guided through a beam ray 16 and a λ/4 plate tube 1 to an objective lens 18, where it is focused to about 1 ka4 and irradiated onto an optical disk 11. Then, the reflected light from the optical disk 11 passes through the objective lens 18, the λ/4 plate 17, the beam sinter 1σ, the cylindrical lens elO, and the focusing lens 21, and is directed to the light receiving surface Kk of the light receiver 22. It is set to K so that it can be photoelectrically converted. For example, as shown in FIG. 3, the light receiver 22 is arranged in a square shape and includes 94 light receiving elements J.
The photodetector is composed of J&@Jjb@Jj@ejJd, and the reflected light is focused approximately at the center of the square.

Light receiving elements 22ae2 located at mutually symmetrical positions of the light receiver 22
The output signals M and C of 2e are each output from a summing amplifier 24. The light-receiving elements 12b and 2 are supplied to the
The output signals B-D of 2a are respectively input to summing amplifiers 24.2a. The output signals of these summing amplifiers x41, 24□ are supplied to a difference detection circuit (for example, a differential amplifier) 25, and also to a summing circuit (for example, a summing amplifier) 26. The output signals of the difference detection circuit 2j and the addition circuit 26 are supplied to a ratio calculation circuit (for example, an analog divider) 27. This ratio calculation circuit 27 calculates the ratio between the detection result of the difference detection circuit 25 and the calculation result of the addition circuit 26.
Then, the output signal of the ratio calculation circuit 21 is supplied to the drive circuit 28. This drive circuit 28 is connected to the ratio calculation circuit 2.
1 drives the coil 9 according to the calculation result of 1.Next, when recording 1 information in the above configuration, the optical head 13 and the optical disk 1
For example, the laser oscillator 1 is located at the outermost periphery on the
4 outputs the reproduction beam light, and passes it through the objective lens 18.
At this time, the optical disk 11 rotates at a predetermined speed, and the reproduction beam light starts tracking from the outermost portion of the recording track.

Thus, the beam of light reflected from the optical disk 11 by the reproduction beam is guided to the light receiver 22 and focused on its light receiving surface. At this time, ・
The incident arm turn of the reflected beam light is caused by the action of the astigmatism optical system formed by the combination K of the cylindrical lens 2o and the condensing lens 21, and is caused by the action of the astigmatic optical system on the optical disk 11 and the objective lens 18.
Three types of shapes are formed depending on the distance between The incident pattern of the beam light becomes a circular shape P with the minimum area as shown in Fig. 3.
For example, if the optical disc 11 moves in the direction m away from the objective lens 18 and a defocus occurs, the above incident pattern will become a deformed I-arm turn P2 extending in the vertical direction, and conversely, the optical disc 11 will move in the direction closer to the objective lens 18. When a focus shift occurs due to movement, the above-mentioned incident turn becomes a deformed pattern P that extends in the horizontal direction.The light receiver 22 charges and converts the reflected light according to the incident/four turns, and outputs the output signal A-D.
summing amplifier 24. Supply to t j 4□. The summing amplifier 241 adds and amplifies the signals A and C to output a signal corresponding to (Arc).Summing amplifier 24
2 is fi(B) by adding and amplifying signals B and D.
Output a signal corresponding to (A + AD) - In this case, (A +
C) signal and (BAD) signal are respectively X in FIG.
It becomes a low level signal as shown by the period ・Thus, (A
(10) signal and (BAD) signal are supplied to the difference detection circuit 25, and from this difference detection circuit 25 ((A10)-(BA
D)) signal is output i.e. 1 this ((Arc)
-(BAD)) signal corresponds to the incident pattern of the reflected beam light on the light receiver 22. Also, (Arc
) and (BAD) signals are supplied to an adder circuit 26, which outputs an (A+C+B+D) signal. This (A+C+B+D) signal is transmitted to the photoreceiver xz'
This corresponds to the total amount of incident light at t1c. Therefore, in the ratio calculation circuit JF, [(Arc)-(BAD)
)/(A+C+B+D) is performed, and ((Arc)
-(BAD)) and (A+C+B+D) is calculated. This calculation result is supplied to the drive circuit 28 as the final detection result for the incident pattern of the reflected beam light, and this is used to determine the position of the objective lens 18. is corrected so that the reproduction beam light is always accurately focused on the recording track on the optical disk 11.

However, now, the recording information node h is the drive circuit jJK.
When supplied, the drive circuit 23 switches the output beam of the radar oscillator 24 to the recording beam only during the period t4 pulse h, and forms a data bit corresponding to the pulse h on the first recording track. At this time, since the energy of the recording beam is several ten times that of the reproduction beam, the beam reflected from the optical disk 11 by the recording beam becomes very strong. Therefore, the summing amplifier J 4i, J
The (Arc) signal and (BAD) signal obtained from 4□ become high level signals for each recording beam, as shown in the Y period in FIG.

When the average value of the (Arc) signal and (BAD) signal (indicated by the dashed line in Fig. 4) is calculated for this Y period, the absolute value is twice that of the X period.
c) and K(BAD)・The value of K is K)3
It is m degrees. Thus, the K(Arc) signal and the K(B
AD) signal is supplied to the difference detection circuit 25, and the difference detection circuit 26 outputs the [K(Arc)-K(BAD)] signal. That is, this (K(Arc)-K(BAD))
) This corresponds to the incidence/arm turn of the reflected beam light on the signal line receiver 22. Further, the K (Arc) signal and K (BAD) No. 41 are supplied to the adder circuit 26.
A K(A+C+B+D) signal is output from this adder circuit 26. This K(A+C+B+D) signal corresponds to the total amount of incident light on the receiver 22. Therefore, in the ratio calculation circuit 21, [K(Arc)- K(BAD))
/K(A+C+B+D) is calculated, and (K(M+c
) −K(BAD)] and K(A+C×B×D) is calculated. Here, comparing the calculation of the ratio calculation circuit 21 between the X period and the Y period, ((Arc)-(BAD))/(A+C+B+D)
1m-(K(Arc,)-K(BAD))/K(A0C
10B+D) It's exactly the same. Therefore, regardless of the energy difference between the reproduction beam light and the recording beam light, accurate focus control is always possible.It is also possible to reliably record and reproduce information.Next, it is possible to accurately record and reproduce information. In the case of reproduction, focus control is performed by the same operation as in the above-mentioned period X. In this case, the radar oscillator 14 continuously outputs only the reproduction beam light.

In the above embodiments, control for defocusing has been described, but when recording and reproducing information, it is common to deal with the track deviation K with respect to the optical disc. Therefore, the track deviation is detected by adding the output signals of two adjacent light receiving elements of the light receiver 22, and adding the output signals of two other adjacent light receiving elements,
The difference between the two addition results is used as the detection result, but even when detecting this track deviation, it is necessary to deal with errors caused by the difference in beam light intensity between recording and playback. Similarly to the above defocus detection,
The ratio between the difference between the two addition results (the total detection result) and the addition result of the output signals of each light receiving element (the total amount of light received by the light receiver 22) is calculated, and this ratio is taken as the final detection result. In the above embodiment, the case where a 4-split light receiver is used is described, but the detection of track deviation can be similarly carried out using a 2-segment light receiver. It goes without saying that the invention is not limited to the examples, and that various modifications can be made without changing the gist.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an optical disk recording and reproducing method that enables reliable recording and reproducing of information without causing defocus or deviation of the beam light with respect to the optical disk.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a four-division optical receiver O for explaining conventional focus control, FIG. Figure 4 showing the configuration of light reception and an example of the incident pattern for it.
The figure is a signal waveform diagram for explaining the operation of the same embodiment. 11... Optical disk, (optical recording medium), IJ...
To optics, x4-... semiconductor radar oscillator, 18...
・Objective lens, 19...Voice coil, 22-・Four division light receiver (multiple division light receiver), 241, 1t4□・−Summing amplifier, 25・−Difference detection circuit, 26… Addition circuit,
21-Ratio calculation circuit, 28... Drive circuit, 1st diagram, 3rd diagram, 4th diagram, Saima-

Claims (1)

[Claims] In a device that records or reproduces information by irradiating a beam of light onto an optical disk, there is provided a plurality of divided light receiving means for receiving reflected light from the optical disk and converting it into an electrical signal, and this plurality of divided light receiving means. a first detecting means for detecting focal shift or track deviation by detecting a difference signal of a predetermined light receiving means; and a first detecting means for detecting a focal shift or a track shift by detecting a difference signal of a predetermined light receiving means, and a total amount of light received by the light receiving means is detected from each output signal of the plurality of divided light receiving means a second detection means; a ratio calculation means for calculating a ratio between the detection result of the first detection means and the detection result of the second detection means; and an optical head driven according to the calculation result of the ratio calculation means. 1. A recording and reproducing method for an optical disc, comprising: a driving means for recording and reproducing an optical disc.