Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1999-08-09
2001-07-17
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S201500, C369S044290
Reexamination Certificate
active
06262412
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical pick-up position detector for detecting a position of an optical pick-up for use in a recording/reproducing device for an optical disk such as a compact. disk.
2. Description of the Related Art
In recent years, optical disks have been used in various technical fields as recording media capable of mass data recording, and optical disk recording/reproducing devices have been actively improved for speeding up recording/reproducing of data relative to the optical disks.
FIG. 5
shows a suspension chassis structure of a compact disk player which has been generally used. In
FIG. 5
, numeral
1
denotes an optical pick-up for reading and writing data relative to an optical disk
6
,
2
a traverse motor for driving the optical pick-up
1
,
3
a lead screw, and
4
a guide shaft. The lead screw
3
has a thread which meshes with a thread of a joint portion
5
of the optical pick-up
1
. The rotation of the traverse motor
2
is transmitted to the lead screw
3
via gears and then to the optical pick-up I via the joint portion
5
so that the optical pick-up
1
is moved in a radial direction, i.e. radially inward or outward, with respect to the optical disk
6
.
When the optical disk
6
is inserted, the compact disk player once moves the optical pick-up
1
to the radially innermost position of he optical disk
6
for detecting a position of the optical pick-up
1
. When the optical pick-up
1
reaches the innermost position, the optical pick-up
1
pushes an inner switch
7
provided in the suspension chassis structure so that the switch
7
is closed to the ON state. In response to the closing operation of the switch
7
, the traverse motor
2
starts reverse rotation so that the optical pick-up
1
starts to move radially outward.
A series of the foregoing operations are controlled by an optical pick-up position detection circuit of the compact disk player.
FIG. 6
shows a structure of the conventional position detection circuit, while
FIG. 7
shows a timing chart for explaining an operation of the conventional position detection circuit. As shown in
FIG. 6
, the conventional position detection circuit comprises a suspension chassis section
8
, a relay connector section
9
and a main substrate section
10
. While the switch
7
is open (OFF state), a high-level signal S
5
of a given voltage is inputted into a microcomputer
13
via a resistor
12
from a power supply
11
for the microcomputer
13
. In response to the signal S
5
, the microcomputer
13
outputs a signal S
4
to a driver IC
14
so that the driver IC
14
gives a high-level signal S
1
to a relay connector terminal P
1
and a low-level signal S
2
to a relay connector terminal P
2
. As a result, the traverse motor
2
is rotated to move the optical pick-up
1
radially inward. In
FIG. 6
, numeral
15
denotes a power supply for the driver IC
14
.
When the optical pick-up
1
reaches the radially innermost position to push and close the switch
7
to the ON state, the voltage of the power supply
11
reaches the ground
17
via relay connector terminals P
3
and P
4
. Thus, signals S
3
and S
6
as well as a signal S
5
which is inputted into the microcomputer
13
become approximately OV, i.e. a low level. In response to the low-level signal S
5
, the microcomputer
13
outputs a signal S
4
to the driver IC
14
so that the driver IC
14
gives a low-level signal S
1
to the terminal P
1
and a high-level signal S
2
to the terminal P
2
. As a result, the traverse motor
2
starts reverse rotation to move the optical pick-up
1
radially outward.
In the foregoing conventional position detection circuit, however, the control implemented by the microcomputer
13
according to the state of the switch
7
is independent of the polarity of the voltage applied to the traverse motor
2
, and thus, four relay connector terminals are required. Further, although the information about the state (ON/OFF) of the switch
7
is fed to the microcomputer
13
, no information about the polarity of the voltage applied to the traverse motor
2
is fed back to the microcomputer
13
.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an improved optical pick-up position detector.
According to one aspect of the present invention, there is provided an optical pick-up position detector comprising an optical pick-up movable in radial directions of an optical disk for detecting signals on the optical disk; a motor for generating driving forces for moving the optical pick-up in the radial directions; a driver for applying a driving voltage to terminals of the motor for forward or reverse rotation of the motor according to a control signal; a controller having an input terminal connected to a power supply via a resistor and having a control terminal for outputting the control signal to the driver according to an electric potential at the input terminal; and a switch disposed between the input terminal of the controller and one of the terminals of the motor, the switch changing its operating state when the optical pick-up moves to exceed a reference position in a radially inward or outward direction with respect to the optical disk.
It may be arranged that the switch is connected to the input terminal of the controller via a diode.
It may be arranged that the diode is disposed so that a forward bias is applied thereto when the electric potential at the input terminal of the controller is higher than an electric potential at an opposite side of the diode.
It may be arranged that when the controller controls the driver to apply the driving voltage to the terminals of the motor for the forward rotation thereof, the optical pick-up moves to exceed the reference position in the radially inward direction to close the switch so that the input terminal of the controller is connected to the one of the terminals of the motor via the diode, and that when the controller controls the driver to apply the driving voltage to the terminals of the motor for the reverse rotation thereof while the switch is closed, the driver applies to the one of the terminals of the motor an electric potential which is higher than the electric potential at the input terminal of the controller.
REFERENCES:
patent: 4142209 (1979-02-01), Hedlund et al.
patent: 5631886 (1997-05-01), Suzuki
patent: 0770993 (1997-05-01), None
Hijikata Masakazu
Hirata Minoru
Connolly Bove & Lodge & Hutz LLP
Le Que T.
Matsushita Electric - Industrial Co., Ltd.
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