Photocopying – Projection printing and copying cameras – Identifying – composing – or selecting
Reexamination Certificate
1998-12-30
2001-05-08
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Identifying, composing, or selecting
C399S051000, C347S130000, C347S237000, C347S238000, C347S247000, C347S249000
Reexamination Certificate
active
06229593
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates an exposure device for use in a printer, a facsimile, a copying machine, etc.
2. Description of the Related Art
There has been known an image forming device such as a printer in which a latent image is formed on a surface of a photosensitive body and then developed with a developer, an image developed by the developer is transferred to a sheet, and a transferred image is fixed onto the sheet by a fixing unit.
FIG. 23
shows the structure of a conventional optical write head. As shown in the figure, the conventional optical write head includes a shift register
11
to which parallel data DATA
00
-
15
of 16 bits, a shift clock CLK and a start signal DSTAR are inputted, a register
12
to which the output of the shift register
11
and a latch signal LST are inputted, and a large number of LEDs (Light-Emitting Diodes)
13
aligned so as to conduct exposure for one line. The optical write head also includes switching elements
14
for controlling the on/off of the LEDs
13
and AND circuits
15
for controlling a logical product of the output of the register
12
and a drive signal DST to the switching elements
14
as a control signal.
In exposing for one line, the start signal DSTR is first inputted to the optical write head. And then, in synchronism with the shift clock CLK, image data as the parallel data DATA
00
to
15
for one line is inputted to the optical write head 16 bits by 16 bits. Thereafter, on the completion of the supply of the image data for one line, the latch signal LST and the drive signal DST are inputted to the optical write head.
On inputting the start signal DSTR, the shift register
11
starts to take the parallel data DATA
00
-
15
, and shifts data stored in the shift register
11
while taking new parallel data DATA
00
-
15
every time the shift clock CLK is inputted to the shift register
11
. On inputting the latch signal LST, the register
12
latches data for one line which is outputted from the shift register
11
to output the data. The AND circuits
15
to which the output of the shift register
11
is inputted, supplies a signal identical in level with a signal outputted from the shift register
11
to the switching element
14
, when the drive signal DST is inputted to the AND circuits
15
. Accordingly, only the LED
13
corresponding to the bit to which the shift register
11
outputs a high signal emits a light. Then, this state is maintained for a predetermined time so that exposure for one line is conducted in correspondence to the inputted image data. Thereafter the supply of image data relating to a succeeding line is conducted in the same procedure in order to make exposure for the succeeding line.
However, in the case of manufacturing an optical write head with the structure, shown in
FIG. 23
, including the large number of LEDs structures one line, a time proportional to the number of LEDs is required for setting data for one line.
For that reason, in order to reduce a time required for setting data for one line, there has been proposed an optical write head in which the optical write head (the shift register and the LEDs) is divided into plural groups and in which data is transferred in a parallel manner to the shift register belonging to each of those groups. For example, Japanese Patent Unexamined Publication Sho 58-48562 discloses an optical write head in which LEDs are divided into a plurality of groups, and plural circuits for driving the LEDs are provided in each group. As to thus structured optical writing head, an excellent printing result cannot be obtained because a light emission timing disperses although data setting is made at a high speed.
SUMMARY OF THE INVENTION
The present invention has been made in order to solve the above problems, and therefore an object of the present invention is to provide an exposure device which is capable of operating at a high speed and obtaining an excellent printing result.
In order to solve the above problems, according to the present invention, there is provided an exposure device comprising a light emitting element array including (N×M) numbers of light emitting elements disposed linearly, M numbers of data holding and outputting means for holding and outputting N numbers of pixel data, the M numbers of data holding and outputting means being adapted to shift the pixel data held therein and take supplied pixel data when the other pixel data is supplied to the M numbers of pixel data holding and outputting means, driving means for driving the (N×M) numbers of light emitting elements in the light emitting element array, simultaneously, according to the (N×M) numbers of pixel data outputted from the M numbers of data holding and outputting means when a stated control signal is inputted thereto, shift quantity designating means for designating the quantity of shift, storing means for storing pixel data contained in time-series image data as inputted, data adding means for adding first non-emission pixel data of the number corresponding to the quantity of shift before the stored pixel data, every time a predetermined quantity of pixel data is stored in the storing means, the non-emission pixel data is pixel data relating to the light emission elements which do not emit the light, and dividing and supplying means for adding second non-emission pixel data after the pixel data to which the first non-emission pixel data has been added so that the total number of pixel data becomes (N×M), and supplies the (N×M) numbers of pixel data as obtained to the M numbers of data holding and outputting means N numbers by N numbers.
In the exposure device thus structured according to the present invention, a preparation for driving all of the light emission elements is made in a time required for holding a predetermined number of pixels in one pixel data holding and outputting means. Also, since all of the light emission elements can be driven simultaneously by the driving means, the use of the exposure device according to the present invention enables an image forming device that can operate at a high speed and obtain an excellent printing result to be manufactured.
Also, since the dividing and supplying means operates in cooperation with the shift quantity designating means, the exposure device according to the present invention can correct a displacement in relative position between a photosensitive drum and a part (optical writing head) comprised of the light emission element array, the data holding and outputting means and the driving means, which is caused when the part is combined with the photosensitive drum (when the exposure device is manufactured).
In realizing the exposure device according to the present invention, it is desirable that the unit (the number of bits) of pixel data supplied to the dividing and supplying means is set to be larger than the unit of pixel data taken by the data holding and outputting means. In particular, it is desirable that the unit of pixel data supplied to the dividing and supplying means is set to be M times of the unit of pixel data taken by the data holding and outputting means.
With the application of the above structure, since parts requiring a high transfer rate is reduced, the exposure device can be manufactured more inexpensively.
The dividing and supplying means may supply the pixel data by use of M numbers of dual-port memories each of that can store at least (2×N) numbers of pixel data, in correspondence with the M numbers of data holding and outputting means, respectively. Also, the dividing and supplying means may supply the pixel data by use of M numbers of first memories that can store at least N pixel data in correspondence with the M numbers of data holding and outputting means, respectively, and M numbers of second memories that can store at least N pixel data in correspondence with the M numbers of data holding and outputting means, respectively.
Also, in realizing the exposure device by the application of the dividing and s
Nishiura Tamotsu
Tokairin Motohiro
Adams Russell
Armstrong Westerman Hattori McLeland & Naughton LLP
Brown Khaled
Fujitsu Limited
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