Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1998-11-02
2001-07-31
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S237000, C358S001160
Reexamination Certificate
active
06268878
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical writing head driving device and a method of driving the optical writing head which optically writes data onto a photosensitive member with a plurality of light-emitting diodes.
2. Description of the Related Art
Forming an electrostatic latent image onto a photosensitive member with lights from an optical writing head comprising a plurality of light-emitting diodes (LED) in an image forming apparatus such as a printer has been known as a conventional technique. In such a technique, for example, the LEDs are arranged in a line in the primary scanning direction, that is, in a direction perpendicular to the sheet feeding direction. The LEDs emit lights in accordance with image data and optically write the image data onto a photosensitive member.
Generally, the LEDs in the optical writing head emit lights unevenly because luminescence of each of the diodes differs from each other. The unevenness of the lights from the LEDs causes deterioration of an electrostatic latent image to be formed on the photosensitive member, and a resultant image on a sheet is also deteriorated.
To overcome the above problem, a modified optical writing head driving device can adjust unevenness of lights from LEDs in an optical writing head.
FIG. 11
is a schematic diagram exemplifying such a conventional optical writing head driving device whose LEDs emit lights evenly.
An optical writing head driving device
100
shown in
FIG. 11
comprises a ROM
101
, a head controller
102
, and an LED head
103
.
The ROM
101
is an EEPROM or the like with small capacity, and inputs and outputs data serially. The ROM
101
previously stores adjustment data for adjusting unevenness of lights from LEDs in the LED head
103
.
The head controller
102
reads out image data from a frame memory or the like (not shown), reads out the adjustment data from the ROM
101
, and outputs the read image data and adjustment data to the LED head
103
.
The LED head
103
comprises a plurality of LEDs arranged in a line in the primary scanning direction and a driver circuit which drives the LEDs to emit lights. The LED head
103
adjusts drive signals from the head controller
102
. The drive signals correspond to the image data. The LEDs are driven in accordance with the adjusted drive signals and emit lights.
An operation of the optical writing head driving device
100
will now be described with reference to a timing chart shown in FIG.
12
. The head controller
102
outputs a chip-select signal (CS) to the ROM
101
, as a result, the ROM
101
is selected. The head controller
102
outputs a sync signal (SCK), a command for reading and address (Si) to the selected ROM
101
. The head controller
102
serially reads out an 8-bit adjustment data (So) from the ROM
101
while being synchronized with the sync signal (SCK). The head controller
102
outputs the read adjustment data and the image data from the frame memory (not shown) to the LED head
103
. The LED head
103
adjusts the drive signals from the head controller
102
. The drive signals are prepared for driving the LEDs and correspond to the image data. The LEDs are driven in accordance with the adjusted drive signals and emit lights for optically writing image data onto the photosensitive member.
As described above, the optical writing head driving device
100
has to take steps of reading the adjustment data from the ROM
101
by the head controller
102
and outputting the adjustment data from the head controller
102
to the LED head
103
, in order to make the LEDs emit lights evenly. Because of those required steps, it takes a longer time for optical writing in such a device than in a device without a light adjusting function.
Time (TW) for reading the adjustment data (So) for one line where the ROM
101
is an EEPROM whose clock frequency is 2 MHz and the number of the LEDs arranged in the LED head
103
in a line is 3840, is obtained by an equation of:
TW=½(MHz)×8(bit/dot)×3840(dots)≈16(msec.)
Velocity (Vppc) of the optical writing process where the resolution is 300 dpi (dots per inch: 1 inch=25.4 mm) is determined by the adjustment data reading time (TW) for one line with an equation of:
Vppc=25.4(mm)/300(dpi)÷TW≈5.3(mm/sec.)
A printer or the like having the optical writing head driving device
100
as its printing section cannot realize high speed printing because its throughput is a couple of sheets per minutes when using sheets whose length in the sub scanning direction (i.e. the sheet feeding direction) is 210 mm.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical writing head driving apparatus and a method of driving an optical writing head which makes light-emitting diodes emit lights evenly but realize high speed optical writing.
To accomplish the above object, an optical writing head driving device according to a first aspect of the present invention comprises an optical head in which a plurality of light emitting elements are arranged in a line in the main scanning direction wherein said light emitting elements in said optical writing head emit lights in accordance with image data by which a photosensitive member is exposed, said optical writing head driving device comprises:
first storage means for previously storing adjustment data prepared for adjusting the quantity of light emission of each light emitting element in said optical writing head;
second storage means for storing adjustment data which is substantially the same as the adjustment data stored in said first storage means, whose data transfer rate is higher than that of said first storage means;
read means for reading out the adjustment data from said second storage means;
adjustment means for adjusting drive signals, which correspond to the image data and are prepared for driving said light emitting elements, in accordance with the adjustment data read out by said read means;
element select/drive means for sequentially selecting said light emitting elements in said optical writing head by a predetermined unit, and for driving said selected light emitting elements unit by unit; and
drive signal supply means for supplying the drive signals adjusted by said adjustment means to said light emitting elements selected by said element select/drive means.
According to the above optical writing head driving device, the read means reads out the adjustment data in the second storage means prepared for adjusting the quantity of light emission of the light emitting elements with high data transfer rate. The adjustment means adjusts the drive signals, which correspond to the image data and are prepared for driving corresponding light emitting elements, in accordance with the adjustment data read out by the read means. The element select/drive means sequentially selects the light emitting elements in the optical writing head by a predetermined unit, and drives the selected light emitting elements unit by unit. The drive signal supply means supplies the adjusted drive signals to the selected light emitting elements. As a result, the optical writing head driving device realize even-light emission from the light emitting elements and high speed optical writing, because the adjustment data is read out from the second storage means with high data transfer rate and the drive signals are adjusted in accordance with the read adjustment data.
Said optical writing head comprises a plurality of light emitting element arrays each having a predetermined unit of said light emitting elements, and said light emitting element arrays are arranged in a line in the main scanning direction;
said element select/drive means sequentially select said light emitting elements in said optical writing head array by array, and drives said selected light emitting elements array by array; and
said drive signal supply means supplies the drive signals adjusted by said adjustment means to corresponding light emitting elements in said light emitting eleme
Hashimoto Jun
Nagasaka Toshio
Yajima Toshiaki
Casio Computer Co. Ltd.
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Le N.
Nguyen Lamson D.
LandOfFree
Optical writing head driving device and method of driving... 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 writing head driving device and method of driving..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical writing head driving device and method of driving... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2440093