Optical device for recording and reproducing information

Details Optical device for recording and reproducing information Optical device for recording and reproducing information

2001-12-17

2004-05-25

Hindi, Nabil (Department: 2655)

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

C369S053370

Reexamination Certificate

active

06741538

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical pickup and so on used for an information processing apparatus for optically performing recording, reproduction, erasure and so on of information.
2. Related Art of the Invention
In the case of recording and reproducing on a plurality of record media for recording and reproducing at different wavelengths respectively by a single apparatus, an optical pickup having a plurality of light sources of different wavelengths according to the types of the record media is generally used.
FIG. 9
shows a configuration of the optical pickup in the past. Reference numerals
901
and
902
denote light source units of mutually different wavelengths, and though it is not shown, they are comprised of, for instance, a semiconductor laser, a hologram, a photo-detector and so on that are examples of the light sources as one piece. The light emitted from the light source unit
901
passes through a beam splitter (hereinafter, BS)
903
, and then it is condensed on a record medium
905
by a condenser lens
904
. The light reflected by the record medium
905
enters into the light source unit
901
by following a reverse optical path. The light incident on the light source unit
901
is diffracted by the hologram built into the light source unit, and various signals including focus, tracking and RF are detected by the photo-detector in the light source unit. However, the configuration of the inside of the light source units
901
and
902
and methods of detecting various signals are not substantial components of this technology and the present invention described hereafter, and also various configurations are already in the public domain, so that description thereof will be omitted.
The light emitted from the light source unit
902
is reflected by the BS
903
and then is condensed on the record medium
905
by the condenser lens
904
. The light reflected by the record medium
905
enters into the light source unit
902
by following the reverse optical path, and the various signals are detected as with the light source unit
901
. The BS
903
synthesizes and separates the lights from the light source units
901
and
902
, where a band-pass filter for controlling reflection and transmission of the lights by the wavelength, a polarizing beam splitter for controlling them by polarization, a half mirror for separating them into a transmitted light and a reflected light at an arbitrary ratio and so on are generally used. The light source units
901
and
902
are connected to a drive circuit
906
and a control circuit
907
, a drive circuit
908
and a control circuit
909
respectively, and the drive circuit supplies a current to the semiconductor laser that is the light source in the light source unit according to the signal from the control circuit so as to control light emission.
As this configuration in the past has the drive circuit and the control circuit provided to each light source unit, there are large amounts of circuitry in the entire optical pickup so that it has problems such as increased costs and upsizing of the apparatus.
SUMMARY OF THE INVENTION
An object of the present invention is to implement an optical pickup and so on for driving a plurality of light sources with a small amount of circuitry and having high-performance drive characteristics.
One aspect of the present invention is an optical pickup for recording and reproducing information on a plurality of record media respectively, said pick up having:
a plurality of light sources corresponding to said plurality of record media;
a drive circuit of driving one of said plurality of light sources;
switching means of switching a connection between said drive circuit and one of said plurality of light sources; and
a control circuit of controlling said drive circuit and said switching means, and wherein:
as for transmission line lengths between said switching means and said plurality of light sources, the shorter a wavelength of the light source is, the shorter the transmission line length thereof is.
Another aspect of the present invention is an optical pickup for recording and reproducing information on a plurality of record media respectively, said pickup having:
a plurality of light sources corresponding to said plurality of record media;
a plurality of drive circuits of driving said plurality of light sources respectively;
switching means of switching a signal from the outside to one of said drive circuits and outputting it; and
a control circuit of controlling said drive circuits and said switching means, and wherein:
as for transmission line lengths between said switching means and said plurality of light sources, the shorter a wavelength of the light source is, the shorter the transmission line length thereof is.
Still another aspect of the present invention is the optical pickup, wherein, when the wavelength of the light source of the shortest wavelength, of said plurality of light sources, is &lgr;
1
and the wavelengths of the other light sources are &lgr;
2
, &lgr;
3
, . . . &lgr;n (n=2, 3, 4 . . . ) in increasing order of wavelength, and the transmission line lengths between said plurality of light sources and said switching means are L
1
, L
2
, L
3
, . . . Ln in increasing order of wavelength, there is a relationship, between the wavelengths and the transmission line lengths, of L
1
/L
2
<&lgr;
1
/&lgr;
2
, L
1
/L
3
≦&lgr;
1
/&lgr;
3
, . . . L
2
/Ln≦&lgr;
1
/&lgr;n.
Yet still another aspect of the present invention is an optical pickup having:
a first light source of recording or reproducing information on a record medium;
a second light source of reproducing the information from said record medium;
a drive circuit of driving said first light source or second light source;
switching means of switching a connection between said drive circuit and said first light source or second light source; and
a control circuit of controlling said drive circuit and said switching means, and wherein:
a transmission line length between said switching means and said first light source is shorter than that between said switching means and said second light source.
Still yet another aspect of the present invention is an optical pickup having:
a first light source of recording or reproducing information on a record medium;
a second light source of reproducing the information from said record medium;
a first drive circuit of driving said first light source;
a second drive circuit of driving said second light source;
switching means of switching a signal from the outside to said first drive circuit or said second drive circuit and outputting it; and
a control circuit of controlling said first drive circuit, said second drive circuit and said switching means, and wherein:
a transmission line length between said switching means and said first light source is shorter than that between said switching means and said second light source.
A further aspect of the present invention is the optical pickup, wherein said first light source is plurality of light sources corresponding to a plurality of record media, and as for transmission line lengths between said switching means and said plurality of light sources, the shorter a wavelength of the light source is, the shorter the transmission line length thereof is.
A still further aspect of the present invention is the optical pickup, wherein, when the wavelength of the light source of the shortest wavelength, of said plurality of light sources, is &lgr;
1
and the wavelengths of the other light sources are &lgr;
2
, &lgr;
3
, . . . &lgr;n (n=2, 3, 4 . . . ) in increasing order of wavelength, and the transmission line lengths between said plurality of light sources and said switching means are L
1
, L
2
, L
3
, . . . Ln in increasing order of wavelength, there is a relationship, between the wavelengths and the transmission line lengths, of L
1
/L
2
≦&lgr;
1
/&lgr;
2
, L
1
/L
3
≦&lgr;
1
/&lgr;
3
, . . . L
1
/Ln≦&lgr;
1
/&lgr;n.
A yet further aspect of the present inventi

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