Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1998-12-07
2001-01-23
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S130000, C347S247000
Reexamination Certificate
active
06177949
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an exposure apparatus used in a printer, a facsimile, a copying machine, and the like, and also to an optical write head employed in such an exposure apparatus. More specifically, the present invention is directed to such optical write head/exposure apparatus capable of writing data in a high speed without fluctuations in light emitting timing.
2. Description of the Related Art
Conventionally, in image forming apparatuses such as printers, latent images are formed on the surfaces of photosensitive members, the latent images are developed by using developing agent, and images developed by the developing agents are transferred to paper, and thereafter the transferred images are fixed on the paper by using fixing devices.
To form the latent images on the surfaces of the photosensitive members in such images forming apparatuses, exposure apparatuses are provided. These exposure apparatuses utilize LED (Light Emitting Diode) arrays and laser beams. In an exposure apparatus with employment of such an LED array, a plurality of LED elements, the total number of which is defined so as to achieve necessary resolution, are arranged in a predetermined range, so that an LED array (namely, optical write head) is formed.
FIG. 7
schematically indicates an arrangement of one conventional optical write head. As shown in this drawing, this conventional optical write head is constituted by a shift register
11
, a register
12
, and a large number of LEDs
13
. To the shift register
11
, 16-bit parallel data DATA
00
to DATA
15
, a shift clock CLK, and a start signal DSTAR are inputted. Both an output from this shift register
11
and a latch signal LST are entered into the register
12
. A large number of LEDs
13
are arranged in one line, by which a 1-line exposuring operation can be performed. Furthermore, the conventional optical write head is arranged by a switching element
14
and an AND gate circuit
15
. The switching element
14
turns ON/OFF the LEDs
13
. The AND gate circuit
15
AND-gates the output from the register
12
with a drive signal DSTB, and supplies the AND-gated signal as a control signal to the switching element
14
.
When the 1-line exposing operation is carried out, the start signal DSTR is first inputted to this optical write head. Then, the image data for 1 line are entered to the optical write head as the parallel data DATA
00
to DATA
15
in unit of 16 bits in synchronism with the shift clock CLK. Thereafter, when the supply of the image data for 1 line is accomplished, the latch signal LST is entered, and also the drive signal DSTB is entered.
When the start signal DSTR is entered to the shift register
11
, this shift register
11
starts to acquire the parallel data DATA
00
to DATA
15
. Every time the shift clock CLK is inputted thereto, this shift register
11
shifts the parallel data stored therein, and also acquires new parallel data DATA
00
to DATA
15
. When the latch signal LST is inputted into the register
12
, this register
12
latches the data for 1 line which are outputted from the shift register
11
, and then outputs the latched data. Upon receipt of the drive signal DSTB, the AND gate circuit
15
into which the data outputted from the shift register
11
is inputted supplies such a signal having the same level as that of the signal derived from the shift register
11
to the switching element
14
. As a result, only LEDs
13
emit the light, and these LEDs
13
correspond to the bits of the shift register
11
from which high level signals are outputted. Then, while this condition is maintained for a preselected time period, the 1-line exposing operation responding to the inputted image data is carried out. Thereafter, the image data as to the next 1 line are supplied in a similar process operation in order to execute the next 1-line exposing operation.
As apparent from the foregoing descriptions, when an optical write head is manufactured in such a manner that a total number of LEDs which constitute 1 line is increased and the circuit arrangement shown in
FIG. 7
is employed, such a time duration directly proportional to this total number of LEDs is necessarily required so as to set image data for 1 line.
Accordingly, other types of optical write heads have been proposed. That is, in order to shorten the time duration required to set the image data for 1 line, the optical write head constructed of shift registers, LEDs and the like is subdivided into a plurality of groups. The image data can be transferred in a parallel manner to the shift registers belonging to each of the subdivided groups. For instance, Japanese Unexamined Patent Application No. 58-48562 opened in 1983 discloses such an optical write head that the LEDs are subdivided into a plurality of LED groups, and the control circuits used to drive LEDs belonging to a subdivided LED group are employed with respect to each of these LED groups. However, in this type of optical write head having the above-described subdivided LED groups/control circuits, although the image data can be set in high speed, the light emitting timing is fluctuated. As a result, there is a problem that the print effects could not be obtained under better conditions.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-described problem, and therefore, has an object to provide an optical write head which can constitute an exposure apparatus which is operable in high speed and capable of achieving print effects under better conditions.
Another object of the present invention is to provide an exposure apparatus equipped with the above-described inventive optical write head, which can be operated in high speeds and further can provide better print effects under such conditions.
To achieve the above-described objects, an optical write head, according to an aspect of the present invention, is featured by arranging such an optical write head by using: a light emitting element array constituted by a plurality of light emitting elements arranged in a line form; a plurality of pixel data holding/outputting means capable of holding/outputting a predetermined number of pixel data, for shifting such pixel data held therein when pixel data is supplied, and also for acquiring the supplied pixel data; and light emitting element array driving means for simultaneously driving the plurality of light emitting elements employed in the light emitting element array in accordance with the pixel data outputted from the plurality of pixel data holding/outputting means when predetermined control signals are inputted.
In the optical write head with employment of the above-described structure, the driving operations for the light emitting elements can be prepared within such a time period required to cause one pixel data holding/outputting means to hold a preselected number of pixels. Also, all of the light emitting elements can be simultaneously driven by the light emitting element array driving means. When the optical write head according to the present invention is combined with, for instance, such a distributing means to form an exposure apparatus, this exposure apparatus can be operated in high speeds, while achieving printing results under better conditions. This distributing means stores pixel data contained in time-sequential image data entered thereinto, and also distributes the stored pixel data to M pieces of pixel data holding/outputting means with respect to N pieces of these pixel data every time (N×M) pieces of pixel data are stored thereinto.
To realize the optical write head according to the present invention, as each of the pixel data holding/outputting means, a means for acquiring the image data when a shift clock is entered is employed. Furthermore, the shift clocks may be preferably, separately entered into a plurality of pixel data holding means.
With employment of such a structure, the circuit for supplying the image data to the optical write head can be more readily formed which may
Nishiura Tamotsu
Tanaka Hideo
Tokairin Motohiro
Armstrong, Westerman Hattori, McLeland & Naughton
Fujitsu Limited
Le N.
Nguyen Lamson D.
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