JPH01146138A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To perform the stable auto-tracking servo control of high precision by detecting plural auto-tracking error signals and using an average value of only auto-tracking error signals, which are within the range of an electric limiter set value, for the auto-tracking servo control. CONSTITUTION:Plural beams are projected to plural preliminarily formatted guide tracks 1a on an optical information recording medium 18, and plural auto-tracking error signals are calculated in accordance with plural tracking signals obtained by detecting respective reflected beams by plural photodetectors 22. It is discriminated whether each auto-tracking error signal is within the range of the preliminarily set electric limiter set value or not, and the average value of only auto-tracking error signals within the range of the electric limiter set value is used as an auto-tracking servo control signal. Thus, the precision of auto-tracking is improved several times even if the quantity of reflected light from the medium is changed by dust or flaws on the medium surface.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical information recording/reproducing device.
For example, it is suitably applied to an apparatus for recording information on a card-shaped or disk-shaped optical information recording medium and/or reproducing information recorded on the medium.

[Prior Art] Conventionally, a disc-shaped medium has been used to record information using light and read out the recorded information.

Various types such as card-shaped, tape-shaped, etc. are known. Among these, card-shaped optical information recording media (hereinafter referred to as "optical cards") are expected to be in great demand as mediums with large storage capacities that are small, lightweight, and convenient to carry.

In the above-mentioned optical card recording, information is recorded as an optically detectable recorded bit string by scanning a preset recording track on the optical card with a light beam that is modulated according to the recorded information and focused to a minute spot. is recorded.

Furthermore, to reproduce the information recorded on the optical card, the recorded bit string is scanned with a light beam having a constant power at a level that does not allow information to be written on the optical card.

This is done by focusing light modulated according to the recorded information onto an optical sensor and performing optical detection.

Scanning of an optical card with a light beam during such information recording and reproduction is performed by relative movement between the optical card and the light beam. When performing this relative movement, the main method for preventing track misalignment is to irradiate light onto guide tracks preformatted on the recording medium.
Autotrack servo control is performed by detecting changes in the amount of reflected light using a sensor or the like.

Conventionally, as an auto-tracking method, for example, in the push-pull method, one light beam is irradiated to two divided sensors, and in the three-beam method, two light beams are irradiated to two sensors, respectively.
In both methods, autotrack servo control is performed so that the difference in sensor output becomes zero.

FIG. 6 is a diagram showing a schematic configuration diagram of an optical information reproducing apparatus using the three-beam method.

In the same figure, the light emitted from the light source 100 becomes a parallel light beam through the collimator lens 101, and the light beam is formed by the diffraction grating +
03 into three luminous fluxes. These light beams pass through a polarizing beam splitter 104 and a 174-wavelength plate 105, and are imaged by an objective lens 106 onto an optical information recording medium 108 having a plurality of guide tracks formed substantially parallel to each other.

FIG. 7 shows the imaging state of the guide track 109 and the plurality of imaging spots 130, 131, and 132 on the optical information recording medium 108.

The reflected light from the recording medium 108 is transmitted to a wavelength plate 105 and a polarizing beam splitter 104 . Through the sensor lens 110 and the cylindrical lens 111, the optical sensor 115 is installed.
~117.

That is, the light of the imaging spot 131 is focused on the optical sensor 116, and the information signal SR recorded on the information track 140 is
is played. Furthermore, the light from the imaging spots 130 and 132 is imaged on the optical sensors 115 and 117, respectively, and a tracking error signal S7 is generated by the differential image amplifier 135.
is obtained.

[Problems to be Solved by the Invention] However, since both the three-beam method and the push-pull method described above perform autotrack servo control using one tracking error signal, for example, as shown in FIG. Due to dust or scratches on the surface,
Even if the amount of light reaching one sensor of the two-split sensor changes, the difference signal is controlled to zero, which may cause meandering recording or tax adjustment, or may limit the electrical control. This has the disadvantage that if the distance is exceeded, the track is likely to become misaligned.

[Means for Solving the Problem] In view of the problems of the prior art described above, an object of the present invention is to provide an optical system that can accurately track even if dust or scratches on the medium surface or other fluctuation factors occur. The purpose of the present invention is to provide a digital information reproducing device.

The above objects are an optical information recording medium provided with a plurality of guide tracks, a means for generating a light beam for recording and/or reproducing information on the medium, and a means for generating a plurality of light beams. means, an optical system for condensing the light flux for recording and/or reproduction and the plurality of light fluxes onto the medium as minute spot lights; and a photodetector for receiving the light via the medium. An optical information recording/reproducing device comprising a servo control means for causing the minute spot light for recording and/or reproduction to follow the guide track, wherein the plurality of light beams have a certain degree of spread on the recording medium. Moreover, the servo control means obtains at least two tracking error signals from the plurality of light beams, and is provided with an electric limiter for each of the plurality of error signals, so that the servo control means obtains at least two tracking error signals from the plurality of light beams, and is provided with an electric limiter for each of the plurality of error signals, and the servo control means is provided with an electric limiter for each of the plurality of error signals. This is achieved by an optical information recording/reproducing apparatus characterized in that the average value of track signals is used as the servo control signal.

[Operation] The optical information recording/reproducing device of the present invention irradiates a plurality of beams (at least two or more) onto a plurality of guide tracks preformatted on a medium, and receives each reflected light by a plurality of light receiving elements. A plurality of autotrack error signals are calculated from a plurality of track signals obtained by the detection, and it is determined whether or not the autotrack error signals are within a preset value of an electrical limiter. The average value of the track signal within the limiter setting value is used for the auto track servo and control signal.

As a result, even if the amount of light reflected from the medium changes due to dust or scratches on the medium surface, and the tracking error signal is so large that it exceeds the electrical limiter, limiter control allows the limiter setting to be adjusted. In order to use the average value of the remaining track signals within the value for servo control,
Compared to the conventional technology, the influence of dust or scratches on the medium surface is at most within the limiter setting value, and can be suppressed to one-fold of the number of detection signals, and the auto-tracking accuracy can be improved several times.

[Embodiments] Hereinafter, specific embodiments of the optical information recording/reproducing apparatus of the present invention will be described in detail based on the drawings.

FIG. 1 shows the optical arrangement of an optical head, an optical information recording medium, and the imaging state of a spot on the medium in a first embodiment of an optical information recording/reproducing apparatus according to the present invention.

In FIG. 1, 11 is a light source such as a semiconductor laser, 12 is a collimator lens that collimates the light from the light source 11, and 1
3 is a two-dimensional diffraction grating, 14 is a polarizing beam splitter, 1
5 is an I/4 wavelength plate, 16 is an objective lens, 18 is an optical information recording medium such as an optical card, 19 is a guide track on the medium 18, and 17 is a light beam spot.

The light emitted from the light source 11 becomes a parallel light beam by the collimator lens 12, and the light beam is divided into a plurality of light beams by the two-dimensional diffraction grating 13. These light beams pass through a polarizing beam splitter 14 and a quarter-wave plate 15, and then enter an objective lens 16.
As a result, the light is focused as a minute spot on the optical information recording medium 18 having a plurality of guide tracks 19 formed substantially parallel to each other.

A guide track 19 and a plurality of imaging spots S++ -3+a, Sx+ "S*s+" on the optical information recording medium 18
FIG. 2 shows the imaging state of SWI"sst.

Here, information recording/reproduction and autofocus servo control are performed at spot Sll, and spots S**, S*s,
It is assumed that autotrack servo control is performed using Sms, Ss++S*s, and Ss*.

In addition, in FIG. 1, the reflected light from the optical information recording medium 18 passes through the objective lens 16, and... An isolator optical system consisting of a 74-wavelength plate 15 and a polarizing beam splitter 14 causes total reflection at the polarizing beam splitter 14, and an image is formed on the light receiving element 22 by an astigmatism optical system consisting of a spherical lens 20 and a cylindrical lens 21. be done.

This light receiving element 22 is as shown in FIG.

In order to detect multiple reflected lights, lO division (a,.

ash ~ass+as+""'Rss) and are arranged as shown in the figure.

In the autofocus servo control in the optical information recording/reproducing apparatus in this embodiment, when the reflected light of the imaging spot S++ on the medium 18 is imaged on the four-split light receiving element all by the astigmatism optical system, An astigmatism method is used that takes advantage of the fact that the shape of this imaged spot changes as the objective lens 16 moves up and down.

On the other hand, in the auto track servo control, as shown in FIG. 2, a plurality of spots S□, S0°Sss, Ss++
The reflected light of sm+Sss is transmitted to a plurality of light receiving elements a□, amn+ats+as++as**as** shown in FIG.
Detected by (aau-ag1), (ass-ass)
, (ash-ass) are calculated, and an electrical limiter provided in advance is activated for each autotrack error signal.
Autotrack servo control is performed using the average value of autotrack error signals within the set value.

By the way, in the push-pull method and three-beam method as autotrack servo control methods that have been used in the past, 1
Autotrack servo control is performed using only the difference signal, so
For example, when the amount of light reflected from the medium changes due to dust or scratches on the medium surface, the imaging spot is moved from its normal position in the direction of the guide tracks so that the difference signal becomes zero. This causes meandering recording during recording and loss of synchronization during playback. Furthermore, if the limits of electrical control are exceeded, this becomes a direct cause of track misalignment.

In contrast to the conventional technology having such drawbacks, the autotrack servo control method adopted in the present invention is as described above, as shown in FIG.
The difference signals of I [ass-ass) are used as auto-track error signals, and a track difference signal having an error signal larger than the electric limiter setting value is wiped out by an electric limiter provided in advance for each, and the remaining Since the autotrack error signal within the electrical limiter setting value is averaged and the average value is used for autotrack servo control, even if the amount of reflected light changes due to dust or scratches on the surface of the medium 18, the autotrack error signal may change. Even if the difference becomes large, servo control can be performed using the remaining track difference signal, so the influence of dirt or scratches is less than the electrical limiter setting value.Furthermore, since the average is taken, auto track servo control can be performed using the remaining track difference signal. The viscosity of can be increased several times.

8(A), ([1), and (C) are such examples, respectively, when it is assumed that there is dust or scratch 25 in spot S0 in FIG. 2, and the signal level of all has decreased. (ash-ash1.(ass-as
s).

FIG. 3 is a diagram showing three sets of tracking error signals (ash-ass). The vertical axis represents the output of the autotrack error signal, and the horizontal axis represents time. The same figure (in bl, 4
0 is the limiter voltage level, 42 is dust, scratches 25
This is the so-called figure 8 curve.

FIG. 9 is a diagram showing an example of the circuit configuration of the photodetector according to this embodiment. In the figure, the processor 44
+-ashL (ass-a*mL (ash-ass
) is detected and the amount is set to limiter voltage 4.
Compare with 0 to determine the size. If it is large, the SW of the tracking error signal is turned off and tracking is performed using the average value of the remaining signals. At this time, in order to keep the gain of the servo signal constant, the processor 44 uses, for example, SWI.

When all of 2.3 are ON, SW4.5 is ON and S
WI, 2.3 (7) When two of them are ON and one is OFF, SW4 is OFF, SW5 is ON, and SWl,
2. When one of 3 is ON and 2 are OFF, SW4
．． 5 are controlled so that both are turned off.

In the present invention, when the two-dimensional diffraction grating 13 shown in FIG. The positional relationship between the imaging spot on 8 and the guide track can exist infinitely depending on the mutual relationship between the diameter and interval of the spots and the width and pitch of the guide track.

In all of these cases, it goes without saying that the same effects as in the first embodiment of the present invention can be obtained. As an example, as shown in FIG. In this case as well, (S's+-3'+s) shows the case where they are arranged substantially in parallel.

In the first embodiment, the error signals of (S'5s-S't*) and (S'+s-S'□) are applied to a limiter, and autotrack servo control is performed only with those that meet the conditions. You can get the same effect as .

In addition to the first embodiment, the plurality of light beam means in the present invention may include a method in which two one-dimensional diffraction gratings are used and superimposed so that the gratings intersect with each other, or a method in which a plurality of light sources are arranged two-dimensionally. In addition, there are methods that use a plurality of light sources arranged one-dimensionally and a one-dimensional diffraction grating, and in each method, it is possible to generate a plurality of light beams similar to the first embodiment, and, It is possible to obtain similar effects.

The present invention is not limited to the above-mentioned embodiments, and various modifications and applications are possible.

For example, in the embodiment described above, the error signal of the corresponding light spot was used as the auto-tracking signal, but a push-pull method may be adopted for each track.For example, as shown in FIG.

1. S” ■・S”+s and 311 l-s l
This is the case when the push-pull method is applied to each spot of l.sup.-Sool. In this case, each corresponding optical sensor needs to be divided into two in the direction in which the track extends.

Similarly, the heterodyne method may be applied to each optical spot; however, the method of tracking each optical spot requires a slightly smaller optical system than the methods shown in Figures 2 and 4. They tend to be complicated.

[Effects of the Invention] As explained above, according to the optical information recording/reproducing apparatus of the present invention, with regard to autotrack servo control, in the conventional technology, autotrack servo control is performed using only one signal, However, as shown in the embodiments of the present invention, a plurality of light beams can be , detects multiple autotrack error signals, activates a preset electrical limiter for each, and then controls the autotrack servo to calculate the average value of only the autotrack error signals within the electrical limiter setting value. By using this method, it is possible to avoid meandering recording, tax adjustment, and track misalignment due to dust or scratches on the media surface.
It is possible to provide an optical information recording/reproducing device that can perform autotrack servo control more stably and with higher precision than before.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the optical arrangement of an optical head, an optical information recording black body, and the imaging state of a spot on the medium in an optical information recording/reproducing apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram showing the positional relationship between the guide track on the medium and the imaging spot. FIG. 3 is a diagram showing the configuration of the light receiving element used in the first example. FIG. 4 is a diagram showing the positional relationship between the guide track on the medium and the imaging spot in the second embodiment. FIG. 5 is a diagram showing the positional relationship between the guide track on the medium and the imaging spot in the third embodiment. FIG. 6 and FIG. 7 are diagrams respectively showing the configuration of a conventional optical information reproducing apparatus employing the three-beam method and the positional relationship of the imaging spots. FIGS. 8A, 8B, and 8C are diagrams showing tracking error signals, respectively, and are diagrams for explaining the limiter voltage. FIG. 9 is a diagram showing an example of the circuit configuration of the photodetector according to this embodiment. 12: Two-dimensional diffraction grating 19: Guide track as++a**+as*+as++as**ass:
Tracking light-receiving element a++: 4-split light-receiving element Representative Patent Attorney Johei Yamashita Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (7)

[Claims] (1) an optical information recording medium provided with a plurality of guide tracks; a means for generating a light beam for recording and/or reproducing information on the medium; and a means for generating a plurality of light beams; an optical system that condenses a light beam for recording and/or reproduction and the plurality of light beams onto the medium as minute spot light; and a photodetector that receives the light that has passed through the medium. or an optical information recording/reproducing device comprising a servo control means for causing a minute spot light for reproduction to follow the guide track, wherein the plurality of light beams are arranged with a certain degree of spread on the recording medium, Moreover, the servo control means obtains at least two tracking error signals from the plurality of light beams, and provides an electric limiter for each of the plurality of error signals, and the average value of the tracking error signals within the limiter setting value. An optical information recording/reproducing apparatus characterized in that the servo control signal is used as the servo control signal. (2) The means for generating a plurality of light beams is formed by an optical element that divides the light beam from the means for generating a light beam for recording and/or reproducing information on the medium into a plurality of light beams. An optical information recording/reproducing apparatus according to claim 1. (3) The optical information recording/reproducing apparatus according to claim 1, wherein the direction in which the plurality of light beams are arranged is substantially parallel or perpendicular to the direction in which the plurality of guide tracks are arranged. (4) The optical information recording/reproducing apparatus according to claim 2, wherein the optical element for dividing the recording and/or reproducing light beam into a plurality of light beams is a two-dimensional diffraction grating. (5) Claim 2, characterized in that the optical element that divides the recording and/or reproducing light beam into a plurality of light beams is two one-dimensional diffraction gratings arranged to overlap each other. The optical information recording/reproducing device described above. (6) The optical information recording and reproducing apparatus according to claim 1, wherein the plurality of light beams are generated from a plurality of light sources arranged two-dimensionally. (7) The optical information recording/reproducing apparatus according to claim 1, wherein the plurality of light beams are generated by a combination of a plurality of light sources arranged one-dimensionally and a one-dimensional diffraction grating.