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Claims  |
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What we claim is:
1. A printing apparatus comprising:
(a) beam forming means which, by application of character dot signals,
forms a beam modulated by the character dot signals;
(b) deflecting means which deflects the modulated beam;
(c) a recording medium on which the modulated and deflected beam is
irradiated;
(d) dot signal forming means which, by application of character signals,
scanning line instructing signals and character size signals forms
character dot signals corresponding to the character signals and the
character size signals, and belonging to the instructed scanning lines;
(e) memory means having a plurality of unit memory regions for storing a
plurality of character signals corresponding to characters to be recorded
on said recording medium and character size signals indicating the size of
the characters to be recorded;
(f) character size converting means which converts character size signals
read from said memory means to converted character size signals indicating
a different character size;
(g) instructing means which instructs whether the character signals stored
in said memory means are to be utilized for recording on said recording
medium in a first mode or in a second mode; and
(h) control means which, when said instructing means instructs recording in
the first mode, reads out the character signals and the character size
signals from one of said unit memory regions in said memory means and
applies the read-out signals to said dot signal forming means, and which,
when said instructing means instructs recording in the second mode, reads
out the character signals and the character size signals from a plurality
of said unit memory regions, drives said character size converting means
to obtain simultaneously converted character size signals from the
character size signals read-out from said plurality of unit memory regions
and applies the read-out character signals and the converted character
size signals to said dot signal forming means.
2. A printing apparatus as claimed in claim 1, wherein said size converting
means converts character size signals to converted character size signals
indicating a smaller character size.
3. A printing apparatus as claimed in claim 1, wherein said dot signal
forming means includes character dot signal forming means which, by
application thereto of character signals, scanning line instructing
signals and character size signals, forms a plurality of character dot
signals corresponding to said character signals and character size signals
and belonging to the instructed scanning lines; dot signal accommodating
means for accommodating a plurality of character dot signals from said
character dot signal forming means; clock signal generating means which
generates clock signals; and sequential read-out means which reads out
sequentially the character dot signals in said accommodating means by
application to said dot signal accommodating means of the clock signals
obtained from said clock signal generating means.
4. A printing apparatus as claimed in claim 1, wherein each unit memory
region has sufficient memory capacity to accommodate therein the character
signals and the character size signals for recording one page of
characters.
5. A printing apparatus as claimed in claim 1, further comprising size
latch means to latch the character size signals read out of said memory
means, wherein said size converting means consists of a size decoder
controlled by said instructing means, said size decoder producing an
output in response to application of the character size signals latched by
said size latch means.
6. A printing apparatus as claimed in claim 1, wherein said control means
includes read-out region selecting means to select the unit memory region
from which the character signals and character size signals are to be read
out.
7. A printing apparatus comprising
(a) beam forming means which, by application of character dot signals
thereto, forms a beam modulated by the character dot signals;
(b) deflecting means to deflect the modulated beam;
(c) a recording medium on which the modulated and deflected beam is
irradiated;
(d) dot signal forming means which, by application of character signals,
scanning line instructing signals and character size signals, forms
character dot signals which correspond to the character signals and
character size signals and belonging to the instructed scanning lines;
(e) memory means having a plurality of unit memory regions, for storing a
plurality of character signals corresponding to characters to be recorded
on said recording medium and character size signals indicating the size of
the characters to be recorded;
(f) character size converting means which converts a first character size
signal read out from said memory means into a second character size signal
which differs from the character size indicated by said first character
size signal;
(g) instructing means which instructs whether said character signals stored
in said memory means are to be recorded on said recording medium in a
first mode or in a second mode;
(h) control means which, when said instructing means instructs recording in
the first mode, reads out the character signals and the character size
signal indicating the character size of the character signals from one of
the unit memory regions and applies said signals to said dot signal
forming means; and which, when said instructing means instructs recording
in the second mode, reads out character signals and character size
signals, when indicating the first character size, from a plurality of the
unit memory regions, and, at the same time, drives said character size
converting means to convert the first character size signals into second
character size signals and applies the character signals and the
associated converted second character size signals to said dot signal
forming means; and
(j) character dot signal suppressing means which, when the character size
signals read out of said memory means indicate the second character size
and said instructing means instructs the second mode, suppresses the
application of character dot signals to said beam forming means.
8. A printing apparatus as claimed in claim 7, wherein said beam forming
means consists of a semiconductor laser oscillator.
9. A printing apparatus as claimed in claim 7, wherein said recording
medium consists of a photosensitive drum.
10. A printing apparatus comprising:
(a) recording means which, by scanning a recording medium, records a
character on said recording medium with dots corresponding to character
dot signals;
(b) dot signal forming means which, by application of character signals,
scanning line instructing signals and character size signals forms
character dot signals corresponding to said character signals and
character size signals and belonging to the instructed scanning lines;
(c) memory means which stores character signals corresponding to characters
to be recorded on said recording medium and character size signals
indicating the size of the characters to be recorded;
(d) character size converting means for converting a first character size
signal read out of said memory means into a second character size signal
indicating a character size different from that represented by said first
character size signal;
(e) instructing means which instructs whether the character signals stored
in said memory means are to be utilized for recording on said recording
medium in a first mode or in a second mode;
(f) control means which, when said instructing means instructs recording in
the first mode, applies the character signals from said memory means and
the character size signal to said dot signal forming means; and which,
when said instructing means instructs recording in the second mode,
converts said character size signal, when a first character size signal,
into a second character size signal through said character size converting
means and applies the read out character signals and converted second
character size signal to said dot signal forming means; and
(g) suppressing means which, when the character size signal read out of
said memory means indicates a second character size and said instructing
means instructs recording in the second mode, suppresses recording by said
recording means.
11. A printing apparatus as claimed in claim 10, wherein said second size
signal indicates a smaller size character than that indicated by said
first size signal.
12. A printing apparatus as claimed in claim 10, wherein said recording
means comprises:
beam forming means which, by application of character dot signals, forms a
beam modulated by the character dot signals;
deflecting means for deflecting the modulated beam; and
a recording medium on which the modulated and deflected beam is irradiated.
13. A printing apparatus as claimed in claim 10, wherein said suppressing
means comprises conversion-suppressing means which prevents the output of
a converted character size signal when a second character size signal is
applied thereto.
14. A printing apparatus as claimed in claim 10, wherein said dot signal
forming means includes character dot signal forming means which, by
application of character signals, scanning line instructing signals and
character size signals, forms a plurality of character dot signals
corresponding to the character signals and character size signals and
belonging to the instructed scanning lines; dot signal accommodating means
which accommodates a plurality of character dot signals from said
character dot signal forming means; clock signal generating means which
generates clock signals; and sequential read-out means which, by
application of clock signals from said clock signal generating means to
said dot signal accommodating means, sequentially reads out the character
dot signals in said accommodating means.
15. A printing apparatus as claimed in claim 10, wherein said memory means
consists of a memory having a plurality of unit memory regions for storing
a plurality of character signals and character size signals.
16. A printing apparatus comprising:
(a) recording means which, by scanning a recording medium, records on said
recording medium characters formed by dots corresponding to character dot
signals;
(b) first dot signal forming means which, by application of character
signals, scanning line instructing signals and character size signals,
forms character dot signals corresponding to the character signals and
character size signals and belonging to the instructed scanning lines;
(c) second dot signal forming means which, by application of character
signals, scanning line instructing signals and character size signals,
forms character dot signals corresponding to the character signals and
character size signals and belonging to the instructed scanning lines;
(d) first memory means for storing a plurality of character signals
corresponding to characters to be recorded on said recording medium and
character size signals indicating the size of the characters to be
recorded;
(e) second memory means for storing a plurality of character signals
corresponding to characters to be recorded on said recording medium and
character size signals indicating the size of the characters to be
recorded;
(f) character size converting means which converts the character size
signals read out of said first and second memory means into converted
character size signals indicating a different character size;
(g) first applying means which reads out character signals and size signals
from said first memory means, and applies the read out character signals
and converted character size signals, obtained by applying the read out
character size signals to said character size converting means, to said
first dot signal forming means;
(h) second applying means which reads out character signals and size
signals from said second memory means and applies the read out character
signals and converted character size signals, obtained by applying the
read out character size signals to said character size converting means,
to said second dot signal forming means;
(i) signal applying means for applying the character dot signals obtained
from said first dot signal forming means and the character dot signals
obtained from said second dot signal forming means to said recording
means; and
(j) synchronizing means for synchronizing the operations of said first and
second applying means.
17. A printing apparatus as claimed in claim 16, wherein said character
size converting means includes a first character size converting means
which converts size signals read out of said first memory means to
converted character size signals indicating a different character size;
and a second character size converting means which converts size signals
read out of said second memory means to converted character size signals
indicating a different character size.
18. A printing apparatus as claimed in claim 16, wherein said signal
applying means comprises a logic circuit which adds together the character
dot signals obtained from said first dot signal forming means and those
obtained from said second dot signal forming means.
19. A printing apparatus as claimed in claim 16, wherein said recording
means comprises:
beam forming means which, by application of character dot signals, forms a
beam modulated by the character dot signals;
deflecting means which deflects the modulated beam; and
a recording medium on which the modulated and deflected beam is irradiated.
20. A printing apparatus as claimed in claim 16, wherein said first dot
signal forming means includes first character dot signal forming means
which, by application of character signals, scanning line instructing
signals and character size signals, forms a plurality of character dot
signals corresponding to the character signals and character size signals
and belonging to the instructed scanning lines; first dot signal
accommodating means which accommodates therein a plurality of character
dot signals from said character dot signal forming means; clock signal
generating means which generates clock signals; and first sequential
read-out means which, by application of the clock signals from said clock
signal generating means, sequentially reads out the character dot signals
in said first accommodating means.
21. A printing apparatus comprising:
(a) beam forming means which, by application of character dot signals,
forms a beam modulated by the character dot signals;
(b) deflecting means which deflects the modulated beam;
(c) recording medium on which the modulated and deflected beam is
irradiated;
(d) first dot signal forming means which, by application of character
signals, scanning line instructing signals and character size signals,
forms character dot signals corresponding to the character signals and
character size signals and belonging to the instructed scanning lines;
(e) second dot signal forming means which, by application of character
signals, scanning line instructing signals and character size signals,
forms character dot signals corresponding to the character signals and
character size signals and belonging to the instructed scanning lines;
(f) first memory means for storing character signals corresponding to
characters to be recorded on said recording medium and character size
signals indicating the size of the characters to be recorded;
(g) second memory means having a plurality of unit memory regions for
storing a plurality of character signals corresponding to characters to be
recorded on said recording medium and character size signals indicating
the size of the characters to be recorded;
(h) first character size converting means which converts the character size
signals read out of said first memory means into converted character size
signals indicating a different character size;
(i) second character size converting means which converts the character
size signals read out of said second memory means into converted character
size signals indicating a different character size;
(j) instructing means which instructs whether said character signals stored
in said second memory means are to be utilized for recording on said
recording medium in a first mode or in a second mode;
(k) repetitive read-out control means which, when said instructing means
instructs recording in the first mode, reads out the character signals and
the character size signals from one of the unit memory regions of said
second memory means and applies the read-out signals to said second dot
signal forming means, and which, when said instructing means instructs
recording in the second mode, reads out the character signals and the
character size signals from a plurality of the unit memory regions of said
second memory means and simultaneously obtains converted character size
signals by driving said second character size converting means and applies
these character signals and converted size signals to said second dot
signal forming means, and further reads out the character signals and the
character size signals repetitively from said first memory means, and
simultaneously obtains converted character size signals by driving said
first character size converting means and applies these character signals
and converted character size signals to said first dot signal forming
means; and
(m) applying means which applies both the character dot signals obtained
from said first dot signal forming means and the character dot signals
obtained from said second dot signal forming means to said beam forming
means.
22. A printing apparatus as claimed in claim 21, wherein said beam forming
means consists of a semiconductor laser oscillator.
23. A printing apparatus as claimed in claim 21, wherein said recording
medium consists of a photosensitive drum.
24. A printing apparatus comprising:
(a) recording means which, by scanning a recording medium, records on said
recording medium characters formed by dots corresponding to character dot
signals;
(b) dot signal forming means which, by application of character signals,
scanning line instructing signals and character size signals, forms
character dot signals and character size signals corresponding to the
character signals and belonging to the instructed scanning lines;
(c) memory means having a plurality of unit memory regions for storing a
plurality of character signals corresponding to characters to be recorded
on said recording medium and character size signals indicating the size of
the characters to be recorded;
(d) write-in means which writes recording information consisting of the
character signals and the character size signals into said memory means;
(e) blank code signal generating means for generating blank code signals;
(f) blank code signal write-in means which writes blank code signals from
said blank code signal generating means into the remainder of said unit
memory regions, when the write-in operation by said write-in means does
not fill a predetermined number of unit memory regions;
(g) instructing means which instructs whether said character signals stored
in said memory means are to be utilized for recording on said recording
medium in a first mode or in a second mode; and
(h) memory region control means which, when said instructing means
instructs recording in the first mode, reads out the character signals and
the character size signals from one of said unit memory regions of said
memory means to apply the same to said dot signal forming means, and
which, when said instructing means instructs recording in the second mode,
reads out the character signals and the character size signals indicating
the character size of the character signals from said predetermined number
of the unit memory regions for application of character signals and
character size signals to said dot signal forming means.
25. A printing apparatus as claimed in claim 24, wherein said dot signal
forming means forms no character dot signal when a blank code signal is
applied thereto.
26. A printing apparatus as claimed in claim 24, wherein said blank code
signal write-in means includes end detecting means which detects the end
of said recording information and gate means which applies an output from
said blank code signal generating means to said memory means after
detection of the end of said recording information by said end detecting
means.
27. A printing apparatus as claimed in claim 24, wherein said write-in
means includes first detecting means which detects recording information
for storage in a single unit memory region and second detecting means
which detects recording information for storage in a plurality of unit
memory regions.
28. A printing apparatus comprising:
(a) recording means which, by scanning a recording medium, records on said
recording medium characters formed by dots corresponding to character dot
signals;
(b) dot signal forming means which, by application of character signals,
scanning line instructing signals and character size signals, forms
character dot signals corresponding to the character signals and character
size signals and belonging to the instructed scanning lines;
(c) memory means having a plurality of unit memory regions for storing a
plurality of character signals corresponding to characters to be recorded
on said recording medium and character size signals indicating the size of
the characters to be recorded;
(d) instructing means which instructs whether said character signals stored
in said memory means are to be utilized for recording on said recording
medium in a first mode or in the second mode; and
(e) read-out means which sequentially reads out said character signals and
character size signals from one of the unit memory regions in said memory
means, when said instructing means instructs recording in the first mode,
and which alternately reads out character signals from a plurality of said
unit memory regions, when said instructing means instructs recording in
the second mode.
29. A printing apparatus as claimed in claim 28, wherein said recording
means comprises:
beam forming means which, by application of character dot signals, forms a
beam modulated by the character dot signals;
deflecting means which deflects the modulated beam; and
a recording medium on which the modulated and deflected beam is irradiated.
30. A printing apparatus as claimed in claim 29, wherein said read-out
means reads out character signals from different unit memory regions
during a single scanning when said instructing means instructs recording
in the second mode.
31. A printing apparatus comprising:
(a) beam forming means which, by application of character dot signals,
forms a beam modulated by the character dot signals;
(b) deflecting means to deflect said modulated beam;
(c) a recording medium, on which the beam deflected by said deflecting
means is irradiated,
(d) dot signal forming means which, by application of character signals and
scanning line instructing signals to instruct the scanning line, forms
character dot signals corresponding to said character signals and
belonging to the scanning line instructed;
(e) memory means having a plurality of unit memory regions for storing a
plurality of character signals to be recorded on said recording medium;
(f) instructing means which instructs whether said character signals stored
in said memory means are to be recorded on said recording medium in a
first mode or in a second mode;
(g) first control means which, when said instructing means instructs the
first mode, reads out the character signals from one of the unit memory
regions in said memory means and applies the read-out signals to said dot
signal forming means, and which, when said instructing means instructs the
second mode reads out the character signals from a plurality of said unit
memory region and applies the read-out character signals to said dot
signal forming means; and
(h) second control means which, when said instructing means instructs the
second mode, controls said dot signal forming means to form on said
recording medium characters smaller in size than that when said
instructing means has instructed the first mode.
32. A printing apparatus comprising:
(a) beam forming means which, by application of character dot signals,
forms a beam modulated by the character dot signals;
(b) deflecting means for deflecting the modulated beam;
(c) a recording medium on which the modulated and deflected beam is
irradiated;
(d) dot signal forming means which, by application of character signals,
scanning line instructing signals and character size signals forms
character dot signals corresponding to the character signals and the
character size signals, and belonging to the instructed scanning lines;
(e) memory means having a plurality of unit memory regions for storing a
plurality of character signals corresponding to characters to be recorded
on said recording medium and character size signals indicating the size of
the characters to be recorded;
(f) character size converting means which converts character size signals
read from said memory means to converted character size signals indicating
a different character size;
(g) instructing means which instructs whether the character signals stored
in said memory means are to be utilized for recording on said recording
medium in a first mode or in a second mode; and
(h) control means which, when said instructing means instructs recording in
the first mode, reads out the character signals and the character size
signals from one of said unit memory regions in said memory means and
applies the read-out signals to said dot signal forming means, and which,
when said instructing means instructs recording in the second mode, reads
out the character signals and the character size signals from said unit
memory regions, drives said character size converting means to obtain
converted character size signals from the character size signals read-out
from said plurality of unit memory regions and applies the read-out
character signals and the converted character size signals to said dot
signal forming means.
33. A printing apparatus comprising:
(a) recording means which, by scanning a recording medium, records on said
recording medium characters formed by dots corresponding to character dot
signals;
(b) first dot signals forming means which, by application of character
signals, scanning line instructing signals, forms character dot signals
corresponding to the character signals and belonging to the instructed
scanning lines;
(c) second dot signal forming means which, by application of character
signals, scanning line instructing signals, forms character dot signals
corresponding to the character signals and belonging to the instructed
scanning lines;
(d) first memory means for storing a plurality of character signals
corresponding to characters to be recorded on said recording medium;
(e) second memory means for storing a plurality of character signals
corresponding to characters to be recorded on said recording medium;
(f) first applying means which reads out character signals from said first
memory means, and applies the read out character signals, to said first
dot signal forming means;
(g) second applying means which reads out character signals and size
signals from said second memory means and applies the read out character
signals and converted character size signals, obtained by applying the
read out character size signals to said character size converting means,
to said second dot signal forming means;
(h) signal applying means for applying the character dot signals obtained
from said first dot signal forming means and the character dot signals
obtained from said second dot signal forming means to said recording
means; and
(i) synchronizing means for synchronizing the operations of said first and
second applying means. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to recording equipment with a recording position
adjuster, which is capable of recording upon a recording medium by means
of a scanning beam modulated by recording signals, particularly, recording
equipment with a recording position adjuster which can detect and command
recording positions by means of a beam detector that can detect specific
positions of the beam.
2. Description of the Prior Art
The general means of recording computer output on a medium is by pressing
type on a recording medium by hammers at the instant when a desired type
on a base revolving at a certain speed is just in face with the recording
paper. The hammering of types on the printing medium, is necessarily
noisy.
A non-impact printer in which an externally modulated beam scans on a
recording paper can provide a fine and high speed beam permitting high
resolution and high recording speed, without the noise of hammering type.
The means can be used in or in connection with computers as printing
equipment for recording the output signals.
In this scanning system, however, several scanning lines on a recording
medium make characters or signs, and, if the starting position of each
scanning line is not exactly at a set position, the scanning lines are
dislocated relative to one another in the scanning direction and the
recorded characters or signs sometimes are not readable.
SUMMARY OF THE INVENTION
A major object of the invention is to provide a position adjuster which
allows detection of an exact recording position, eliminating any
dislocation between the scanning lines.
Another object of the invention is to provide a position adjuster which can
detect an exact recording position with a very simple composition.
A further object of the invention is to provide a position adjuster which
allows starting at a certain position apart from a preset starting
position.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in greater detail with reference to the
accompanying drawings in which;
FIGS. 1 A through D is a block diagram of one embodiment of the invention.
FIG. 2 is a perspective view of a recording unit of the embodiment shown in
FIG. 1.
FIG. 3 is a further perspective view of the recording unit.
FIG. 4 is a side elevational view of a principal recording mechanism in the
recording unit.
FIGS. 5 (a) and (b) is a set of graphs indicating the relationship between
surface potential and ac discharge time.
FIG. 6 is an equivalent circuit of the recording unit.
FIGS. 7 A, B and C is a set of drawings illustrating the recording of
characters on the recording medium.
FIGS. 8 A and B illustrates the positioning of information on the recording
medium.
FIG. 9 illustrates a recording format on a recording paper.
FIG. 10 A is a block diagram in detail of the character generating circuit
of FIG. 1.
FIG. 10 B is an enlarged drawing illustrating the formation of a character
by means of a beam.
FIG. 11 is a block diagram detailing the recording clock generater in FIG.
1.
FIG. 12 is a set of wave forms illustrating the generation of recording
clock pulses.
FIG. 13 is another embodiment of a counter 195 shown in the block diagram
of FIG. 11.
FIG. 14 is a detailed block diagram in detail of the address counter 124 in
FIG. 1.
FIG. 15 is a detailed block diagram in detail of a changing circuit for the
embodiment of FIG. 1.
FIG. 16 is a detailed block diagram in detail of a vertical clock circuit
in FIG. 1.
FIG. 17 is a detailed block diagram in detail of a horizontal clock circuit
in FIG. 1.
FIG. 18 is a detailed block diagram of a line counter in FIG. 1.
FIGS. 19 A, B, C and FIG. 20 illustrate a process of multiple printing.
FIG. 21 is a top view of the recording unit in illustrating beam exposure
in the recording unit.
FIG. 22 is a diagram of the relative positions FIGS. 1A through 1D.
FIG. 23 is a block diagram in detail of a write-in circuit.
FIG. 24 is a block diagram in detail of a read-out circuit.
FIG. 25 shows in the form of a block diagram the relationship between page
buffer memories and address counters.
FIG. 26 is a detailed block diagram of the character generating circuit.
FIG. 27 is a circuit diagram of a size decoder in detail.
FIG. 28 is an another embodiment shown in a circuit diagram, for setting,
shift margin in FIG. 11.
FIG. 29 is an another embodiment of shift register 165 in FIG. 10.
FIG. 30 is a view of a photosensitive drum.
FIG. 31 is a circuit diagram of a recording control circuit in the
recording unit.
FIG. 32 shows the wave forms of signals generated by a rotating
photosensitive drum.
FIG. 33 is a block diagram of a reshaping circuit for paper feeding
signals.
FIGS. 34 and 35 are a set of wave forms of paper feeding signals and other
signals.
FIG. 36 is a block diagram of the reshaping circuit for paper feeding
signals.
FIG. 37 illustrates a side view of a group of rollers illustrating
paper-feeding.
FIG. 38 illustrates a perspective view of a group of rollers illustrating
paper-feeding.
FIG. 39 illustrates a driving mechanism for paper-feeding.
FIG. 40 is a circuit diagram of a paper-feeding control circuit.
FIG. 41 is a set of wave forms in the control circuit in FIG. 40.
FIGS. 42 and 43 are circuit diagrams for paper-feeding.
A preferred embodiment of a recording equipment using a laser beam for
scanning a recorded medium will be described in detail.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, there is shown a block diagram of said recording
equipment employing a laser beam which consists of an information
providing unit 100 such as a magnetic tape recorder, control unit 101
which controls information from said information providing unit 100 in
order to be recorded properly, and a recording unit 300 in which
information from said control unit 101 is recorded on a recording medium.
In this embodiment of the invention, recording unit 300 provides latent
images on a photosensitive material scanned by a laser beam which is
modulated by recorded information. The latent images are developed by
means of a toner and the developed image is transferred to a printing
paper. We will now describe in some detail such recording equipment. FIGS.
2 and 3 show a general perspective view of the recording equipment in
which a laser beam emitted from laser oscillator 301 is led to an input of
modulator 303 through reflectors 302. Reflectors 302 are provided only for
saving space by changing the optical path and can be eliminated if
desired.
In the modulator 303, an optoacoustic modulator utilizing optoacoustic
effect or an optoelectric modulator utilizing optoelectric effect, both
known, can be used.
The intensity of the laser beam is modulated in accordance with the
intensity of the input signals.
If laser oscillator 301 is a semiconductor laser or a circuit-controllable
gas laser, an internal modulation laser incorporating internally a
modulator element, beam expander 304 can be used, omitting modulator 303.
The laser beam through modulator 303 is magnified in beam diameter by means
of the beam expander 304, retaining parallelism of the light beam. This
magnified laser beam is led to polygonal/mirror 305 which has a plurality
of mirrors. Polygonal mirror 305 is mounted on a shaft supported with high
precision bearings (for example, pneumatic bearings) and is driven by a
constant speed motor 306 (for example, hysterisis synchronous motor, DC
servomotor). Laser beam 312 scans horizontally by means of rotation of the
polygonal mirror and is focused upon photosensitive drum 308 through an
imaging lens 307 having f-v characteristics. In common imaging lenses, the
imaging portion r on an imaging plane at the projection angle .theta. is
r=f.multidot.tan .theta. (1)
where f=focal length of imaging lens
In this embodiment, the projection angle of the reflected laser beam 312 on
the imaging lens 307 linearly changes with elapse of time. Accordingly,
the moving speed of the imaged spot on the imaging plane of photosensitive
drum 308 changes non-linearly i.e. is not at constant speed. With increase
of projection angle, the moving speed increases. In other words, a laser
beam which is periodically turned on for very short time intervals permits
a series of spots to be formed upon photosensitive drum 308, in which the
distances between the spots become wider near both extremities of the
drum. In order to avoid this result, imaging lens 307 is tailored so as to
have the property:
r=f.multidot..theta. (2)
Such a lens is called an imaging lens. And also, if parallel light is
focused as a spot through an imaging lens, the minimum diameter of the
spot is
dmin=2.44.lambda. f/A (3)
where
f: focal distance of imaging lens
.lambda.: wave length of light used
A: diameter of imaging lens
A sharper spot dmin can be obtained as A becomes larger, if f and .lambda.
are constant. The beam expander 304 mentioned above is used for this
effect. Beam expander 304, therefore, can be omitted as long as an
obtained diameter of a laser oscillator is as small as required. Beam
detector 318 consists of small slits and optoelectric sensors with high
response time (for example, a PIN diode). Beam detector 318 detects
position of scanning laser beam 312, and initiates a time interval
preceding the start of input signals to modulator 303 to impart the
desired information on the photosensitive drum. By this means, lack of
precision in the mirrors of the polygonal mirror and non-synchronization
of horizontal signals due to non-uniform rotation can be reduced
considerably and high quality images can be obtained, and the requirement
of precision in both polygonal mirror 305 and driving motor 306 is
somewhat reduced. The above-mentioned matters result in less technical
difficulties and reduce manufacturing costs.
As described, deflected and modulated laser beam 312 is irradiated on
photosensitive drum 308 and latent images are developed by an
electrophotographic process, fixed, and printed on printing mediums 311 of
ordinary paper to thereby produce hard copies.
Printing unit 319 will now be described by referring to FIG. 4. An example
of electrophotographic processes which can be applicable to the embodiment
is the Japanese Patent Publication 23910/67 corresponding to U.S. Pat. No.
3,666,363. A surface of a photosensitive drum 308 consisting of a
photoconductive layer and an insulating layer is first charged with
positive or negative charge, which traps in the photoconductive layer a
charge of the opposite polarity. Then said laser beam 312 irradiates the
charged insulated layer and ac corona discharge 310 is simultaneously
discharged. This allows patterns to form due to potential differences
resulting from patterns of light and dark produced by laser beam 312, and
then the insulated laser is uniformly exposed in order to obtain a high
contrast electrostatic image. The electrostatic image is visualized by
means of a major developing agent of charged color particles in developing
unit 313, and the visualized image is transferred to printing material 311
by using an internal or external electric field and is thermally fixed by
fixing means 315 such as ultrared ray lamps or heat plates. The
electro-photographic image is thereby printed on the copy medium. After
printing, cleaning unit 316 cleans the insulated layer to remove the
remaining charged particle so that photosensitive drum 308 can be used
repetitively.
The corona discharging unit for printing is numbered 314 and the post
corona discharger is numbered 317 and same members represent the same
units in all figures.
Next we describe, referring to FIG. 5, in this embodiment of the invention
the phenomena which occur in photosensitive agents when the surface charge
on an insulating surface is reduced by corona discharge and the surface is
irradiated by a laser beam after uniform charging on the surface of the
insulated layer in the photosensitive body.
FIG. 5 shows the change of surface potential of a photosensitive body.
In FIG. 5 (a), the frequency of ac corona discharge is considerably low. In
this case, the surface potential of the insulating surface during ac
corona discharge, depending upon the phase of the ac voltage, becomes
between the full line and the dotted line. The period of irradiation by
the laser beam is locally very short, for example, 150 nanoseconds in this
embodiment. This causes non-uniform static potential images after full
exposure by light on account of the non-uniform potential on the insulated
surface even though irradiation by laser is at a constant quantity. The
developed latent images are, therefore, not uniform, synchronizing with ac
frequency. In copying machines, this phenomenon is not significant because
the effect of the phase after luminous exposure on the total area of ac
discharge is made even.
To eliminate this non-uniformity, higher frequency ac discharging results
in decreasing the amplitude of variation synchronized with ac frequency of
the surface potential of the insulated layer (FIG. 5, b). According | | |
