Coherent light generators – Particular beam control device – Scanning
Reexamination Certificate
1999-01-21
2001-06-12
Evans, F. L. (Department: 2877)
Coherent light generators
Particular beam control device
Scanning
C372S026000, C372S029012, C372S029014, C347S237000, C347S247000, C250S305000, C250S234000
Reexamination Certificate
active
06246705
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device for an imaging device such as a laser beam printer, and more particularly, to an optical scanning device having a controller for outputting control data, and a driver for driving a light source in accordance with the control data.
Conventionally, optical scanning devices have been employed in electrophotographic imaging devices.
As an example of the electrophotographic imaging devices, a laser beam printer is known, which employs an optical scanning device and forms an image, based on image data, on a recording sheet in accordance with an electrophotographic image forming process.
The optical scanning device for the laser beam printer is provided with a light source for emitting a beam; a deflector for deflecting the beam emitted by the light source to scan within a predetermined angular range; and an f&thgr; lens which makes a spot formed, by the scanning beam, on a surface to be scanned to move at a predetermined speed. Generally, the light source includes a laser diode, and a collimator lens which converts a divergent light emitted by the laser diode to a parallel light beam.
When the optical scanning device as described above is employed in the laser beam printer, a laser beam, which is emitted by the laser diode and collimated by a collimating lens, forms a beam spot on a photoconductive drum, via the deflector such as a polygonal mirror and the f&thgr; lens. The surface of the photoconductive drum is evenly charged, and the beam spot moves on the photoconductive drum in a direction parallel to a rotation axis thereof. While the spot moves on the photoconductive drum, the laser diode is driven, by a driver, so that the intensity of the emitted beam is varied (i.e., modulated) in accordance with imaging data. Further, the photoconductive drum is rotated about the rotation axis. The direction parallel to the rotational axis of the photoconductive drum is generally referred to as a main scanning direction, and the direction in which the photoconductive drum is rotated is referred to as an auxiliary scanning direction. Since the beam spot moves within a circumferential surface of the photoconductive drum as being modulated in accordance with the imaging data, a two-dimensional latent image is formed on the circumferential surface of the photoconductive drum.
The latent image is developed by adhering toner to form a toner image. Then, the toner image is transferred on a recording medium such as a recording sheet. The transferred toner image is then fused/pressed, and thereby fixed on the recording sheet.
In order to maintain tone density of the toner image on the photoconductive drum regardless of changes of ambient temperature, the intensity of the beam emitted by the laser diode should be controlled. Further, in order to control the gradation of the toner image, a period during which the laser diode is driven and/or the intensity of the emitted beam should also be controlled.
Generally, the intensity of the beam and modulation is controlled by a driver which is constituted as a single board, and control data used for controlling the power and modulation of the beam is generated and transmitted to the driver by a controller which is constituted as another single board. The controller board and the driver board are provided in the optical scanning device, separately and connected by a harness and including a plurality of data busses.
FIG. 1
shows a control system of a conventional optical scanning device including a controller
20
A and a driver
10
A. The controller
20
A includes a control circuit
21
, a power control data outputting circuit
22
, and a modulation data outputting circuit
23
.
To the control circuit
21
, data representing temperature detected by a temperature sensor and imaging data representing an image to be drawn (printed) are input. The power control data outputting circuit
22
, which is controlled by the control circuit
21
, outputs power control data, as digital data, for changing the output power of a laser diode
2
so that a tone density of the toner image is adjusted. The modulation data outputting circuit
23
, which is also controlled by the control circuit
21
, outputs modulation data, as digital data, for modulating the beam emitted by the laser diode
2
based on the imaging data. In this example, the modulation data includes PWM (Pulse Width Modulation) data for controlling the width of the driving pulse of the laser diode.
The driver
10
A has a power control signal outputting circuit
12
which is a D/A (digital to analog) circuit, a drive circuit
11
, and a PWM signal outputting circuit
13
.
The power control signal outputting circuit
12
receives the power control data which is transmitted from the power control data outputting circuit
22
, through an eight-bit data bus
32
, and outputs a power control signal to the drive circuit
11
. The PWM signal outputting circuit
13
receives the PWM data transmitted from the PWM data outputting circuit
23
through an eight-bit data bus
33
, and outputs a PWM signal to the drive circuit
11
.
Further to the above an enabling signal is transmitted from the control circuit
21
to the drive circuit
11
, through a control signal line
41
. The drive circuit
11
controls the intensity of the emitted beam of the laser diode based on the power control signal, and modulates the emitted beam based on the PWM signal and the enabling signal.
In the conventional control system described above, in order to transmit the power control data and the PWM data, the controller
20
A and the driver
10
A are connected by eight-bit busses
32
and
33
. This structure requires a relatively large interface unit at each of the controller
20
A and the driver
10
A since the number of connector pins and lines are relatively large, and further a relatively large room to accommodate such an interface unit is also necessary. Furthermore, if an imaging device is of a multi-beam type imaging device using a plurality of beams simultaneously, corresponding number of interface units should be provided in the optical scanning device, which increases the size of the device as well as a manufacturing cost.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an optical scanning device which has less number of data buses in comparison with the conventional optical scanning device, and still enables the device to be made smaller in size, and at less manufacturing cost.
For the above object, according to the invention, there is provided an optical scanning device which is provided with:
(a) a light source that emits a light beam;
(b) a driver that controls output power and modulation of the light beam emitted by the light source;
(c) a controller that outputs power control data and modulation data respectively used for controlling the output power and modulation of the light beam to the driver; and
(d) a single data bus that connects the driver and the controller, the power control data and the modulation data being transmitted through the single data bus at different timing.
With this structure, through the single data bus, the power control data and the modulation data can be transmitted from the controller to the driver, and the driver can control the laser diode in accordance with both the power control data and the modulation data.
Optionally, the controller may output a timing control signal and transmission of the power control data and the modulation data may be switched in accordance with the timing control signal.
Accordingly, with one control signal, operation status of the driver and the controller can be controlled.
In particular, the controller may include:
a power control data outputting circuit that outputs the power control data as digital data;
a modulation data outputting circuit that outputs the modulation data as digital data; and
a control circuit that controls data output of the power control data outputting circuit and the modulation data outputting circuit, and
the driver may include
Asahi Kogaku Kogyo Kabushiki Kaisha
Evans F. L.
Greenblum & Bernstein P.L.C.
LandOfFree
Optical scanning device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical scanning device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical scanning device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2444809