Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2000-01-27
2001-09-04
Schuberg, Darren (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S197100, C359S200700, C359S214100, C250S236000, C369S044170
Reexamination Certificate
active
06285484
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an optical disk drive.
Generally, an optical disk drive writes and reads data on an optical disk by means of a laser beam. The optical disk drive includes a light source module that emits the laser beam and an optical head carrying an object lens that converges the laser beam on a small light spot on the optical disk.
The tracking operation of the optical disk drive includes (1) a rough tracking operation and (2) a fine tracking operation. The rough tracking operation is accomplished by moving the optical head crossing the tracks of the optical disk. The fine tracking operation is accomplished by minutely moving the light spot on the optical disk. For this purpose, a galvano mirror is provided in a light path between the light source module and the object lens. By rotating the galvano mirror, the angle of incidence of the laser beam entering the object lens is changed, so that the light spot on the optical disk is moved.
FIGS. 1A and 1B
are a perspective view and a side view of a conventional galvano mirror system. The galvano mirror
44
is mounted to a mirror holder
42
. The mirror holder
42
is supported by a stator
41
via plate springs
43
so that the mirror holder
42
is rotatable about a rotation axis P. In order to actuate the galvano mirror
44
, a coil
45
is fixed to the mirror holder
42
. A magnet yoke
46
is provided to the stator
41
, which generates a magnetic field in which the coil
45
is positioned. When current flows in the coil
45
, the galvano mirror
44
is rotated as shown by A in
FIG. 1B
, due to an electromagnetic induction caused by the current flow in the coil
45
and the magnetic field caused by the magnets of the yoke
46
.
In order to detect the rotation of the galvano mirror
44
, a reflecting surface
50
is formed on one of side faces of the mirror holder
42
. Further, a photo-sensor
49
is provided to a circuit board
47
fixed to the stator
41
so that the photo-sensor
49
is faced with the reflecting surface
50
. The photo-sensor
49
includes an LED chip
49
A and two photo-transistors
49
B. The LED chip
49
A and the photo-transistors
49
B are disposed on a line that is perpendicular to the rotation axis of the mirror holder
42
. The two photo-transistors
49
B are located on both sides of the LED chip
49
A (on the above-mentioned line).
In a state the reflecting surface
50
is in parallel to the photo-sensor
49
, the lights emitted from the LED chip
49
A and reflected by the reflecting surface
50
equally reach two photo-transistors
49
B. When the mirror holder
42
is rotated as shown by A in
FIG. 1B
, light entering one of the photo-transistor
49
B is increased, while light entering the other photo-transistor
49
B is decreased. Thus, the rotation amount of the galvano mirror
44
can be detected by measuring the difference in outputs of two photo-transistors
49
B.
However, since the reflecting surface is provided to one of side faces of the mirror holder
42
, such a conventional galvano mirror system has a disadvantage such that an arrangement of the photo-sensor occupies relatively large space.
Further, if there is a difference in sensitivities of the photo-transistors
49
B, it may cause an offset. That is, there is a possibility that the outputs of two photo-transistors
49
B are not equal with each other, even if the reflecting surface
50
is in parallel to the photo-sensor
49
. In the conventional galvano mirror system, it is difficult to remove such offset.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a galvano mirror system that is compact in size and capable of detecting the rotation of a galvano mirror. It is another object of the present invention to provide a galvano mirror system wherein it is easy to remove an offset caused by a difference in sensitivity of sensors.
According to one aspect of the present invention, there is provided a galvano mirror system including (1) a galvano mirror having a mirror surface which reflects light for data to reading and data writing, (2) a mirror holder having a front portion to which the galvano mirror is mounted and a rear portion opposing to the front portion, (3) a stator which rotatably supports the mirror holder, (4) first and second reflecting surfaces provided to the rear portion of the mirror holder, (5) first and second photo sensors provided to the stator so that the first and second photo sensors are respectively faced with the first and second reflecting surfaces, each of the photo sensors comprising a light-emitting device and a light-receiving device, and (6) a controller which detects a rotation of the mirror holder according to a difference between outputs of the light-receiving devices of the first and second photo sensors.
With such an arrangement, since the first and second reflecting surfaces are provided to the rear portion of the mirror holder, the first and second photo-sensors (which are faced with the reflecting surfaces) can be located at the rear of the mirror holder. Thus, the space for the arrangement of the photo sensors can be relatively small.
In a particular arrangement, the light-emitting devices and the light-receiving devices (of the first and second photo sensors) are disposed in a certain direction that is perpendicular to a rotation axis of the mirror holder. Further, the first and second reflecting surfaces are disposed in the above-mentioned certain direction.
Optionally, the light-emitting devices (of the first and second photo sensors) are located on both sides of the light-receiving devices (of the first and second photo sensors) in the above-mentioned certain direction. Such arrangement prevents external light from entering the light-receiving devices.
Further optionally, the photo sensors can be fixed to a sensor holder mounted to the stator. The position of the sensor holder with respect to the mirror holder can be adjusted in the above-mentioned certain direction. If the position of the sensor holder is changed (with respect to the mirror holder), the positional relationship between each photo sensor and the corresponding reflecting surface is varied. Thus, even if there is a difference in sensitivities of the light-receiving devices, an offset caused by the difference (in sensitivities) can be easily removed by adjusting the position of the sensor holder.
According to another aspect of the present invention, there is provided a galvano mirror system including (1) a galvano mirror, (2) a mirror holder having a front portion to which the galvano mirror is mounted and a rear portion opposing to the front portion, (3) a stator which rotatably supports the mirror holder, (4) a reflecting surface provided to the rear portion of the mirror holder, (5) a photo sensor provided to the stator so that the photo sensor is faced with the reflecting surface, the. photo sensor comprising a light-emitting device and two light-receiving devices, and (6) a controller which detects the rotation of the mirror holder according to a difference in outputs of two light-receiving devices.
With such an arrangement, since the reflecting surface is provided to the rear portion of the mirror holder, the photo-sensor (which is faced with the reflecting surface) can be located at the rear of the mirror holder. Thus, the space for the arrangement of the photo sensor can be relatively small.
In a particular arrangement, a recess is formed at the rear portion of the mirror holder. In such case, the reflecting surface is formed on an end surface of a lib formed in the recess.
According to further aspect of the present invention, there is provided a galvano mirror system including (1) a galvano mirror having a front surface which reflects laser beam for data reading and data writing and a rear surface opposing to the front surface, (2) a mirror holder having a front portion (to which the galvano mirror is mounted) and a rear portion opposing to the front portion, (3) a stator which rotatably supports the mirror holder, (4) a reflecting surface pro
Nakagishi Toshio
Takishima Suguru
Asahi Kogaku Kogyo Kabushiki Kaisha
Assaf Fayez
Greenblum & Bernstein P.L.C.
Schuberg Darren
LandOfFree
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