Optical pickup apparatus

Details Optical pickup apparatus Optical pickup apparatus

2000-12-27

2003-12-09

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

C369S112200, C369S112190, C369S112230

Reexamination Certificate

active

06661765

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-010721, filed Jan. 19, 2000; and No. 2000-252564, filed Aug. 23, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to an optical pickup apparatus for executing at least one of data recording and reproduction by applying a laser beam to a data recording medium.
A magneto-optical pickup apparatus is known as an apparatus capable of repeatedly recording and reproducing data. The most important demand for this apparatus is downsizing. To satisfy the demand, various means are being proposed. For example, Japanese Patent Application KOKAI Publication No. 10-143934 discloses an all-in-one type magneto-optical pickup apparatus as shown in FIG.
14
.
This optical pickup apparatus comprises a silicon substrate
32
, a hologram element
38
provided on the silicon substrate
32
, a Wollaston prism
40
and a polarizing prism
39
provided on the hologram element
38
. The hologram element
38
has a beam branching function. The Wollaston prism
40
and the polarizing prism
39
are formed integral as one body. The polarizing prism
39
has a polarization beam separating film
39
a
and an inclined surface
39
b.
The polarization beam separating film
39
a
has a transmittance of substantially 70% and a reflectance of substantially 30% for P-polarized light, and has a reflectance of substantially 100% for S-polarized light. The inclined surface
39
b
reflects light reflected by the polarization beam separating film
39
a,
thereby branching the light.
In the above-described optical pickup apparatus, a laser diode
33
emits a P-polarized light beam. The laser beam emitted from the laser diode
33
passes through the hologram element
38
and enters the polarizing prism
39
. Part of the laser beam entering the prism
39
passes through the polarization beam separating film
39
a,
and is then converged by an objective
42
onto a magneto-optical disk
43
. When the converged laser beam is reflected from the magneto-optical disk
43
, the direction of polarization of the laser beam is rotated through substantially about 0.5° by a magnetic signal recorded in the magneto-optical disk
43
. As a result, the laser beam reflected from the magneto-optical disk
43
has a small amount of S-polarized light component that serves as a magneto-optical signal. This reflected light again enters the polarizing prism
39
via the objective
42
.
Almost all the light having the S-polarized light component, which is contained in the light entering the polarizing prism
39
, is reflected from the polarization beam separating film
39
a
of the prism
39
, and then reflected from the inclined surface
39
b
of the prism
39
. The thus-branched light enters the Wollaston prism
40
. The light entering the Wollaston prism
40
branches into two polarized light beams. The polarizations of these two beams are perpendicular to each other. These two beams enter respective sections
36
a
and
36
b
of a photodiode
36
for data signal detection. Data detection is executed by detecting the difference between two signals output from the sections
36
a
and
36
b.
On the other hand, part of the light, which has the P-polarized light component and enters the polarizing prism
39
, passes through the polarization beam separating film
39
a
and then enters the hologram element
38
. At this time, “+” first-order diffracted light and “−” first-order diffracted light are generated. Thus, the light entering the hologram element
38
branches into two light beams. The “+” first-order diffracted light and “−” first-order diffracted light enter photodiodes
34
and
35
for error signal detection, respectively. At this time, the “+” first-order diffracted light is converged in a position between the hologram element
38
and the photodiode
34
by the lens effect of the hologram element
38
. On the other hand, the “−” first-order diffracted light is converged in a position beyond the photodiode
35
. Using this phenomenon, a focus error is detected by detecting the spot sizes of the light beams on the photodiodes
34
and
35
. Further, an error in tracking is detected by detecting the positions of light spots on the photodiodes
34
and
35
.
Since, in general, light emitted from a laser is divergent light, the magneto-optical pickup apparatus disclosed in Japanese Patent Application KOKAI Publication No. 10-143934 can use only the central part of a laser beam, and cannot use the peripheral part of the beam. Accordingly, the efficiency of use of light is low. This means that the disclosed apparatus cannot be used as a magneto-optical pickup apparatus that requires a high laser output, such as a rewritable magneto-optical pickup apparatus, or as a magneto-optical pickup apparatus in which the rotational speed of the disk is increased to increase the transfer rate.
Moreover, when using even the peripheral part of a laser beam, the disclosed apparatus requires a large polarizing prism that can receive a wide range of light. This makes it difficult to reduce the size of the apparatus.
In other words, the all-in-one type pickup apparatus disclosed in Japanese Patent Application KOKAI Publication No. 10-143934 can not satisfy the requirements of increasing the efficiency of use of light, that is, increasing the power of the light applied to the data recording medium as well as of downsizing the pickup apparatus.
BRIEF SUMMARY OF THE INVENTION
It is the object of the invention to provide a compact optical pickup apparatus which has higher efficiency of use of light.
To attain the object, according to one aspect of the invention, there is provided an optical pickup apparatus for executing at least one of data recording and reproduction by applying a laser beam to a data recording medium, comprising: a semiconductor substrate having a main surface; a light source for emitting a laser beam in a direction substantially perpendicular to the main surface of the semiconductor substrate; an NA converter for receiving the laser beam emitted from the light source and for outputting the laser beam so that a divergent angle of the outputted laser beam smaller than a divergent angle of the received laser beam; an objective opposed to the data recording medium; a first beam branching unit for permitting one of transmission therethrough and reflection therefrom of the laser beam outputted from the NA converter to thereby guide the laser beam to the data recording medium via the objective so that the laser beam reflects from the data recording medium, the first beam branching unit also transmits therethrough and reflects therefrom a part of and another part of the laser beam reflecting from the data recording medium and then passing through the objective, respectively, thereby branching the laser beam in two directions; and a first light receiving element provided at the semiconductor substrate, for receiving the laser beam branched by the first beam branching unit.
According to the other aspect of the invention, there is provided an optical pickup apparatus for executing at least one of data recording and reproduction by applying a laser beam to a data recording medium, comprising: a semiconductor substrate having a main surface; a light source for emitting a laser beam in a direction substantially perpendicular to the main surface of the semiconductor substrate; a means for receiving the laser beam emitted from the light source, converting the received laser beam and for outputting the laser beam so that a divergent angle of the outputted laser beam smaller than a divergent angle of the received laser beam; an objective opposed to the data recording medium; a means for permitting one of transmission therethrough and reflection therefrom of the laser beam outputted from the divergent angle converting means to thereby guide the laser beam to the data recording medium via the objec

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