JPH11328680A - Optical disc reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disc reproducing device producing playback signals having high signal level simultaneously from a plurality of tracks while suppressing deterioration of playback signal due to effect of tracking offset, residual error of tracking, crosstalk, or the like. SOLUTION: Reflected light of a light beam projected across a plurality of tracks on an optical disc is arranged in the direction orthogonal to the scanning direction of track and detected by a light receiving element 5 arranged to allot a plurality of light receiving sections S1-Sn for each track in order to play back information recorded on a plurality of tracks simultaneously. In such an optical disc player, amplifying means G1-Gn amplifies the output from the light receiving section corresponding to each track at a specified gain ratio and an adder means A1-AN adds the output from the amplifying means in correspondence with each track to produce the playback signal of each track.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light receiving element which irradiates a light beam so as to straddle a plurality of tracks on an optical disk and reflects a reflected light of the light beam in a direction perpendicular to the track scanning direction. The present invention relates to an optical disk reproducing apparatus for reproducing information recorded on a plurality of tracks at the same time by detecting the information.

[0002]

2. Description of the Related Art Conventionally, there has been widely known an apparatus for simultaneously reproducing information of a plurality of tracks on an optical disk by using a light receiving element in which a plurality of light receiving sections are arranged in a direction orthogonal to the scanning direction of the tracks (see FIG. 1). For example, JP-A-5-128585
Issue publication). The optical disc reproducing apparatus includes: an irradiating unit that irradiates a light beam so as to straddle a plurality of tracks on the optical disc; A level detecting means for detecting a signal level in each light receiving section using each output from the plurality of light receiving sections, and one track from output signals of the plurality of light receiving sections based on a detection result of the signal level in each light receiving section. By selecting one signal, a reproduction signal corresponding to actual track scanning is to be output. Further, in the case where a track is scanned so as to straddle two adjacent light receiving units, there is a case where a signal obtained by simply adding the outputs of two adjacent light receiving units is output as a signal. .

[0003]

By the way, as described above, an optical disc reproducing apparatus for obtaining a track reproduction signal by selecting and outputting one signal for one track from the output signals of a plurality of light receiving sections. Even if the track width (width of the information pit) is larger than the width of the light receiving section formed by dividing the light receiving element into a plurality, the output of one light receiving section even when the track scanning always extends over the plurality of light receiving sections. Select only signals. Therefore, a reproduced signal is obtained from only a part of the actual track, and there is a problem that the S / N is deteriorated. Conversely, even if the track width is smaller than the width of the light receiving section, the same applies to the case where a track scan straddles two adjacent light receiving sections due to the influence of a tracking offset or a tracking residual error. For this reason, the S / N is deteriorated. In order to prevent this, there has been proposed a method of obtaining a reproduction signal by simply adding the outputs of the two light receiving units when the track scan straddles two adjacent light receiving units as described above.

However, simply adding the outputs of two adjacent light receiving sections is equivalent to treating two adjacent light receiving sections as one large light receiving section, so that the substantial resolution of the light receiving sections is reduced. Would. The effect is small when one light receiving portion is sufficiently small with respect to the track width, but when the light receiving portion is large with respect to the track width, for example, when there are approximately two or less light receiving portions for one track, the cross stroke , And the characteristics of the reproduced signal are degraded. The present invention has been devised in view of the above problems and effectively solving them. An object of the present invention is to provide an optical disc reproducing apparatus capable of suppressing deterioration of a reproduced signal due to the influence of tracking offset, tracking residual error, crosstalk, etc., and simultaneously obtaining a good reproduced signal having a high signal level from a plurality of tracks. Is to do.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a method of forming a light beam reflected over a plurality of tracks on an optical disk in a direction perpendicular to the scanning direction of the tracks. In an optical disc reproducing apparatus that reproduces information recorded on a plurality of tracks at the same time by detecting with a light receiving element arranged so that a plurality of light receiving sections are assigned to each track, Amplifying means for amplifying each output of the light receiving unit at a predetermined gain ratio, and adding means for obtaining a reproduced signal for each track by adding each output from the amplifying means in correspondence with each track. It comprises so that it may be provided.

As described above, information recorded on a plurality of tracks on an optical disk is arranged by a plurality of, for example, at least three or more light-receiving units arranged in a direction orthogonal to the track scanning direction. Detecting and further amplifying each output of the light receiving section corresponding to each track at a predetermined ratio by an amplifying means, and adding these by an adding means, the influence of tracking offset, tracking residual error, crosstalk, etc. Therefore, it is possible to simultaneously obtain a good reproduction signal having a high signal level from a plurality of tracks.

In this case, a signal level detecting means for detecting a signal level of each signal output from each of the light receiving sections, and the predetermined gain in the amplifying means according to the signal level detected by the signal level detecting means. Gain control means for changing the ratio of the signal, the signal level output from each light receiving section is detected, and the gain of the predetermined ratio is adjusted according to the detected level, that is, by performing weighting by the control means. Just set it.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical disk reproducing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing an optical disk reproducing apparatus of the present invention, and FIG. 2 is a circuit diagram showing a signal processing system of the apparatus shown in FIG.
FIG. 1 mainly shows an irradiation optical system for irradiating an optical disc 1 with a laser beam L for reading and a light receiving element. In FIG. 1, reference numeral 2 denotes a light source for outputting a laser beam L. It is composed of an array, an LED and the like. Reference numeral 3 denotes a half mirror, 4 denotes a condensing lens for condensing the laser beam L passing through the half mirror 3 on the surface of the optical disk 1, and 5 denotes a light receiving element for receiving reflected light from the optical disk 1 and converting the reflected light into an electric signal. Reference numeral 10 denotes a reproducing system for obtaining an audio signal, a video signal, and the like from the electric signal obtained by the light receiving element 5.

The light receiving element 5 has, for example, an elongated shape and is divided into a plurality of, for example, n pieces, so that the light receiving elements 5 are arranged in a direction orthogonal to the optical track running direction as shown in FIG. In addition, a plurality of light receiving sections S1 to Sn are formed. The light receiving element 5 is divided so that at least three or more light receiving portions S1 to Sn are assigned to one track in a direction orthogonal to the track traveling direction.
That is, it is divided so that at least 3 × N light receiving sections are formed for N tracks. FIG. 2 shows a case where three light receiving sections are assigned to one track for convenience of explanation, and the light receiving sections corresponding to track 1, track 2, track 3,. S4 to S6, S7 to S9,... S
(N-2) to Sn. Incidentally, the relationship is 3 × N = n. G1 to Gn are amplifying means with variable gains, for example, variable gain amplifiers, and amplify the outputs of the light receiving units S1 to Sn with a predetermined gain. The gains of the variable gain amplifiers G1 to Gn are variably controlled so as to have a predetermined ratio for each track as described later.

[0010] A1 to AN are, for example, adding means composed of adders, which add the outputs of the variable gain amplifiers G1 to Gn for each corresponding track to obtain a reproduced signal. Here, since three light receiving sections are assigned to one track, the outputs of three variable gain amplifiers are added. Reference numeral 6 denotes level detection means for detecting the level of the output signal of each of the light receiving sections S1 to Sn. Reference numeral 7 denotes gain control means, based on the output of the level detection means 6, for three tracks corresponding to one track. The gain ratio for each variable gain amplifier is variably set, and the signal is output to each of the variable gain amplifiers G1 to Gn as a gain control signal.

Next, the operation of the apparatus configured as described above will be described. First, the laser light L emitted from the light source 2 passes through the half mirror 3 and the objective lens 4 and is applied so as to straddle a plurality of tracks on the optical disc 1. Light reflected in accordance with information on a plurality of tracks on the optical disk 1 passes through the objective lens 4 and is guided to the light receiving element 5 by the half mirror 3 and is converted into an electric signal. In the light receiving element 5, the respective light receiving sections S1 to Sn detect the respective reflected lights, output the electric signals converted according to the light amounts to the variable gain amplifiers G1 to Gn, respectively, and simultaneously send the electric signals to the signal level detecting means 6. The signal level detecting means 6 detects the signal level in each of the light receiving sections S1 to Sn as an average signal level over a certain period of time or a cumulative signal level, and sends the result to the gain control means 7.

The gain control means 7 sets an addition ratio of the output signals of the respective light receiving sections based on the detection result of the signal level detection means 6, and outputs a gain control signal representing a gain in accordance with the addition ratio to each of the light reception sections. It is sent to the variable gain amplifiers G1 to Gn. In the variable gain amplifiers G1 to Gn, each light receiving unit S1 has a gain corresponding to a gain control signal.
After the output signals from .about.Sn are weighted and amplified, they are sent to the corresponding adders A1 to AN. The output signals weighted as described above are respectively added by the adders A1 to AN in correspondence with each track,
It is output as a reproduction signal of each track. In this manner, the reproduction signal of the track 1 is obtained by amplifying the output signals of the light receiving sections S1 to S3 by the gain of the predetermined ratio set by the gain control means 7 and then adding the signal by the adder G1 to the track 2 .., S (n−2) are the reproduction signals of the light receiving sections S4 to S6, which are similarly obtained by adding the output signals of the light receiving sections S4 to S6 by the adder G2. To Sn can be obtained as signals added by the adders A3 to AN, respectively.

Next, an example of a method for setting an addition ratio (gain ratio) according to the present invention will be described. FIG. 3 is a diagram showing an example of a positional relationship between the light receiving unit and the track scanning and a detection result of the signal level of each light receiving unit at that time. First, the truck
As shown in FIG. 3A, when scanning near the center of the corresponding three light receiving sections, the signal level of each light receiving section is as shown in FIG.
Are distributed so that the signal level of the light receiving portion located at the center, for example, S2, S5, S8,... Among the three light receiving portions corresponding to each track becomes the highest. In this case, for the track 2, the corresponding three light receiving units S4, S5,
The respective signal levels of S6 are av4, aav5, av
Therefore, the addition ratio (gain ratio) of the output signals of the light receiving units S4, S5, and S6 is set to be the same as the signal level ratio of av4: av5: av6. As a result, the signal ratio of the light receiving unit S5, which is mainly scanned by the track, is increased, and the signal ratio of the light receiving units S4, S6 that hardly scans the track and easily contains a false signal such as crosstalk from an adjacent track is increased. Lower, and as a result,
A good reproduction signal of track 2 having a high signal level can be obtained. Good reproduction signals can be obtained for other tracks by similarly setting the addition ratio corresponding to each track.

Next, a case in which a track is deviated from the vicinity of the center of the corresponding three light receiving sections due to the influence of a tracking offset or the like and is constantly straddling the two light receiving sections will be described with reference to FIG. . In this case, FIG.
As shown in (A), the track is located off the center of the corresponding three light receiving units, and scans across the two light receiving units. The signal level of each light receiving section is shown in FIG.
3B, and the peak value is slightly shifted as compared with the case shown in FIG. Describing the track 2, three corresponding light receiving sections S4,
The signal levels of S5 and S6 are detected as av4, av5, and av6. In this case, as in the case described with reference to FIG. 3, the addition ratio (gain ratio) of the output signals of the light receiving units S4, S5, and S6 is set to be av4: av5: av6. Thereby, the light receiving section S5 near the track scanning position,
The signal ratio of S6 can be increased, and the signal ratio of the light receiving section S4 that includes a large amount of crosstalk from an adjacent track can be reduced, so that a good reproduction signal of track 2 can be obtained. Similarly, reproduction signals corresponding to other tracks are obtained for other tracks.

Due to uneven track pitch or positional deviation of the light receiving section, among many tracks, one track scans near the center of the corresponding light receiving section, and another track scans the center of the corresponding light receiving section. There is a case where scanning is performed with a shift in the vicinity, but even in such a case, a good reproduction signal can be obtained from each track by a method similar to the case of FIGS. In the above embodiment, an example in which the width of one light receiving portion is larger than the track width has been described. However, the light receiving elements are divided so that the width of the light receiving portion is smaller than the track width, and the track scanning is performed. Will be described over a plurality of light receiving units. FIG. 5 shows the present situation at this time, and FIG. 5B shows the detection result of the signal level of each light receiving unit in the case shown in FIG. In the above embodiment, three light receiving units correspond to one track. Here, a case where six light receiving units correspond to one track will be described. In this case, as a matter of course, assuming that tracks 1 to N are simultaneously reproduced, there are 6 × N light receiving sections. For example, the track 1 corresponds to the light receiving units of S1 to S6, the track 2 corresponds to the light receiving units of S7 to S12, and so on.

As described above, even when the number of light receiving sections (the number of signals) that must be added to obtain a reproduction signal for one track increases, the addition ratio (gain ratio) for each track is the same as that described above. 3 and FIG. 4. That is, the track 2 will be described. The signal levels of the corresponding six light receiving sections S7, S8,... S12 are higher in the light receiving sections closer to the track scanning, such as cv7, cv8,. Since the signal level is distributed lower in a light receiving unit farther from the light source and including more crosstalk from an adjacent track, the addition ratio of the output signals of the six light receiving units S7, S8,. What is necessary is just to set. Also, by setting the addition ratio for the other tracks in the same manner as described above, good reproduction signals can be simultaneously obtained from a plurality of tracks.

As described above, the method of setting the addition ratio (gain ratio) according to the signal level of each light receiving section has been described as one embodiment of the present invention. Instead, the envelope of the reproduction signal of each track is set to the envelope. The detection may be performed, and the addition ratio may be controlled and set so that the size of the envelope is maximized. In this embodiment, only the output signal of the light receiving section corresponding to each track, that is, only the output signal of the corresponding three light receiving sections is added in the case of FIG. The target to be added including a part of the corresponding light receiving unit, that is, by overlapping the adjacent light receiving unit with the adjacent track, the light receiving unit to be added is selected by the detection value of the signal level,
A method such as setting an addition ratio may be employed. In this case, a good reproduction signal can be obtained even when the tracking residual error is large, that is, when the tracking servo has low tracking accuracy.

Furthermore, in this embodiment, the method of variably setting the addition ratio has been described. However, the tracking accuracy of the tracking servo is sufficiently high. When the positional relationship is always substantially constant, the addition ratio may be always constant (fixed value).

[0019]

As described above, according to the optical disk reproducing apparatus of the present invention, the following excellent operational effects can be exhibited. When a reproduction signal is obtained from output signals of three or more light receiving units corresponding to one track, each output is weighted at a predetermined ratio and added instead of simply adding each output. In addition, it is possible to suppress the deterioration of the reproduction signal due to the influence of the tracking residual error, crosstalk, and the like, and to simultaneously obtain a good reproduction signal having a high signal level from a plurality of tracks.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an optical disk reproducing device of the present invention.

FIG. 2 is a circuit diagram showing a signal processing system of the device shown in FIG.

FIG. 3 is a diagram illustrating an example of a positional relationship between a light receiving unit and track scanning, and a detection result of a signal level of each light receiving unit at that time.

FIG. 4 is a diagram illustrating an example of a positional relationship between a light receiving unit and track scanning when a tracking offset exists, and a detection result of a signal level of each light receiving unit at that time.

FIG. 5 is a diagram illustrating an example of a positional relationship between a light receiving unit and a track scanning when there are six light receiving units with respect to a track, and a detection result of a signal level of each light receiving unit at that time.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Light source, 3 ... Half mirror, 4 ... Objective lens, 5 ... Light receiving element, 6 ... Signal level detection means, 7
... gain control means, 10 ... reproduction system, A1 to AN ... adders (addition means), G1 to Gn ... variable gain amplifiers (amplification means), S1 to Sn ... light receiving units.

Claims (2)

[Claims] 1. A method of arranging reflected light of a light beam applied so as to straddle a plurality of tracks on an optical disk in a direction orthogonal to a scanning direction of the track, and assigning a plurality of light receiving units to each track. In an optical disc reproducing apparatus that simultaneously reproduces information recorded on a plurality of tracks by detecting with a light receiving element configured, an amplification for amplifying each output of the light receiving section corresponding to each track at a predetermined gain ratio. An optical disk reproducing apparatus, comprising: a unit; and an adding unit that adds each output from the amplifying unit in correspondence with each of the tracks to obtain a reproduced signal for each track. 2. A signal level detecting means for detecting a signal level of each signal output from each of said light receiving units, and said predetermined gain in said amplifying means in accordance with the signal level detected by said signal level detecting means. 2. The optical disc reproducing apparatus according to claim 1, further comprising: gain control means for changing a ratio.