Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1999-04-23
2001-11-06
Tran, Thang V. (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044230, C369S044410
Reexamination Certificate
active
06314063
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application Nos. P10-115693 filed Apr. 24, 1998 and P11-086892 filed Mar. 29, 1999, which applications are incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an integrated light emitting and receiving device and an optical pick-up for emitting light to a recording medium, receiving reflected light modulated by pits formed on the recording medium, and detecting the focus condition and tracking condition based on the information of the reflected light.
2. Description of the Related Art
Recently, various kinds of recording media including recording media using a change of reflectance, optomagnetic recording media, and the like have been developed and proposed. Various kinds of optical disc players have been proposed and standardized.
In compact disc (CD), compact disc-read only memory (CD-ROM), and other so-called phase type optical disc players, the standards call for the depth of the pits formed in the optical disc to be about ⅕ of the wavelength of light.
On the other hand, in digital versatile disc (DVD), digital versatile disc-read only memory (DVD-ROM), and other more recent optical disc players, the standards call for the depth of the pits to be about ¼ of the wavelength of light.
In the above optical disc players, it is necessary to control the tracking servo system so as to make a laser spot follow the recording track of the optical disc and to control the focus servo system so as to keep the laser spot focused on the optical disc.
The tracking error signal and focus error signal for the tracking servo system are detected by for example an optical pick-up.
For example, as shown in
FIG. 1
, an optical picks-up is comprising of an object lens
2
arranged facing an optical disc
1
and a so-called laser coupler
3
hybridized for reducing the size and cost.
The laser coupler
3
has the structure illustrated in FIG.
2
and FIG.
3
. In the laser coupler
3
shown in FIG.
2
and
FIG. 3
, a prism
8
and a photodiode
11
are mounted on a semiconductor integrated circuit substrate
4
on which two photodetector
5
and
6
are formed.
In the photodiode
11
, a photodetector
12
for monitoring the laser output is formed. A laser diode
10
is mounted on the photo diode
11
.
The laser diode
10
outputs a laser beam to the beam splitting face
8
a
of the prism
8
and outputs a laser beam for auto power control (APC) to the laser which automatically controls the output of the laser diode
10
. The laser beam is received by the photodetector
12
. The laser beam output to the beam splitting face
8
a
of the prism
8
is reflected on the beam splitting face
8
and is focused on the signal face of the optical disc
1
through the object lens
2
.
The light is influenced by the pits of the optical disc
1
and is reflected to enter into the beam splitting face
8
a
through the same path.
The reflected light entering into the beam splitting face
8
a
is focused on the photodetector
5
and the reflected light on the photodetector
5
is reflected on the reflection face
8
b
to enter the photodetector
6
.
When obtaining a tracking error signal by the so-called push-pull method and obtaining a focus error signal by the so-called differential spot size method in a CD, CD-ROM, or other optical disc player, it is possible to adopt the configuration for example shown in FIG.
4
.
In
FIG. 4
the photodetectors
5
and
6
are each split into four light receiving regions a to d, i to e. The spot S of the reflected light strikes all of the receiving light receiving regions.
Note that the push-pull method features a very simple configuration and since basically a one-spot optical system is sufficient does not need grating such as in the so-called three-beam method.
If the tracking error signal is TE, the focus error signal is FE, and the amounts of the received light of the receiving light regions a to d and i to l are Ma to Md and Mi to Ml, the tracking error signal TE and the focus error signal FE can be calculated by the following equations (1) and (2):
FE=
[(
Ma+Md
)−(
Mb+Mc
)]−[(
Mi+Ml
)−(
Mj+Mk
)] (1)
TE=
[(
Ma+Mb
)−(
Mc+Md
)]+[(
Mk+Ml
)−(
Mi+Mj
)] (2)
An information signal RF recorded on the optical disc
1
can be calculated by the following equation (3):
RF=Ma+Mb+Mc+Mc+Md+Mi+Mj+Mk+Ml
(3)
On the other hand, in DVD, DVD-ROM, or other the optical disc player, as mentioned above, the depth of the pits of the disc is about ¼ of the wavelength &lgr; of the laser beam.
Therefore, if obtaining the tracking error signal TE by the above push-pull method, the component [(Ma+Mb)−(Mc+Md)]+[(Mk+Ml)−(Mi+Mj)] of the push-pull signal becomes so small that the tracking error signal cannot be obtained.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an integrated light emitting and receiving device capable of reducing the number of regions of the light receiving elements, detecting the focus condition and tracking condition by simple configurations, and reducing the size of a semiconductor integrated circuit substrate on which the light receiving elements are formed.
According to the present invention, there is provided an integrated light emitting and receiving device for emitting light to a recording medium on which a plurality of pits are formed, focusing the light on the recording medium, receiving the reflected light influenced by the pits, and detecting a focus condition and tracking condition of the light focused on the recording medium in accordance with the information of the reflected light, comprising first and second light receiving elements which are provided on a substrate and are divided into a plurality of light receiving regions; a light emitting element which is provided on the substrate and emits light in a predetermined direction; a light splitting means which is provided on the first and second light receiving elements, emits the light input from the light emitting element to the recording medium, focuses the reflected light from the recording medium onto the first light receiving element, and focuses the reflected light reflected from the first light receiving element onto the second light receiving element; a tracking condition detecting means for detecting the tracking condition only from information on the amounts of light received by the light receiving regions of the first light receiving element; a focus condition detecting means for detecting the focus condition only from information on the amounts of light received by the light receiving regions of the second light receiving element.
In the integrated light emitting and receiving device according to the present invention, the information of the amounts of received light of the first light receiving element and the second light receiving element are respectively used to detect the tracking condition and the focus condition. Therefore, since it is unnecessary to duplicately divide the first and second light receiving elements for detecting the tracking condition and the focus condition, it becomes possible to reduce the number of light receiving regions of the light receiving elements.
That is, in the first light receiving element, it is possible to provide the minimum number of light receiving regions for detecting the tracking condition, while in the second light receiving element, it is possible to provide the minimum number of light receiving regions for detecting the focus condition.
As the result, the configuration for detecting the tracking condition and the focus condition is simplified.
Alternatively, preferably the first light receiving element is divided into four light receiving regions along with the longitudinal
Sonnenschein Nath & Rosenthal
Sony Corporation
Tran Thang V.
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