JPH0766946A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent uneven picture by devising a read period to be constant at all times in a copying machine using plural lasers so as to record the picture. CONSTITUTION:A write system index signal SW is inputted to a synchronization circuit 41 of a read system to generate a signal of one clock width (WINDY). A 1st counter 42 counts number of clocks from the input of the WINDY till a succeeding WINDY is received to measure the period of the index signal SW. A quotient resulting from dividing the measured period by a beam number at a divider 44 is inputted to a comparator 46. The comparator 46 provides an output when the count of the 2nd counter 45 is equal to the quotient. An index selector 47 selects an output of the comparator 46 and the WINDY based on the beam number and plural read system index signals SR are generated for one write scanning period and inputted to a timing generating circuit 48 to control a drive timing of a line sensor 49 for reading.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus,
Specifically, in an image forming apparatus configured to read an image of a document by photoelectric conversion and record the read image information with a plurality of laser beams modulated based on the read image information, a reading operation and a recording operation are performed. Technology for synchronizing.

[0002]

2. Description of the Related Art Conventionally, an original is optically scanned, an optical image thereof is received by a photoelectric conversion element such as a line image sensor, converted into an electric signal, and the electric signal is digitized. A digital copying machine configured to modulate a laser beam based on image information of a document converted into a signal and form an electrostatic latent image on a photoconductor by the laser beam is known.

In the writing device using the laser beam, a sensor (index sensor) for detecting the incident beam is provided in the scanning region of the laser beam, and the laser beam is detected based on the detection signal of the sensor. Forming a sync signal (index signal) for controlling the start of recording. Then, a data clock is generated based on the synchronization signal, and the laser is modulated based on the data clock.

On the other hand, in the image forming apparatus using the laser beam as described above, in order to increase the recording speed,
There is a configuration in which a plurality of lines are simultaneously recorded by using a plurality of laser beams.

[0005]

By the way, as described above, an image of an original is read by a photoelectric conversion element, and a plurality of laser beams are used based on the read image information to simultaneously image a plurality of lines on a recording medium. In the case of a copying machine configured to form a reading system, the reading cycle and the writing cycle are different, and the reading system index signal cycle is equal to the writing system index signal cycle divided by the number of beams. That is, the same number of reading system index signals as the number of beams are generated within one cycle of the writing system index signal.

Therefore, conventionally, in one cycle of the writing system index signal, the writing system index signal is used as one reading system index signal, and the other reading system index signals correspond to the period of the writing index signal and the number of laser beams. On the basis of this, it is configured to be generated in a preset cycle. For example, when the number of laser beams is three,
As shown in FIG. 7, within one cycle T of the write-system index signal, three read-system index signals are generated at a cycle t, and the first two read-system index signals are the write-system index signal cycle. The write system index signal is used as the last read system index signal, which is generated at a preset cycle from the number of laser beams. In this case, the cycle t of the reading system index signal is t = 3 / T.

However, when the cycle of the write-system index signal changes to T'as shown by the broken line in FIG. 7 due to uneven rotation of the polygon mirror or the like, the read-system index signal using the write-system index signal is also generated. Similarly, as indicated by the broken line in the figure, the same shift occurs, and the period of the reading system index signal during this period shifts from t to t '. For this reason, the period between the reading system index signals is not constant, which may cause image unevenness. The same thing occurs when the cycle of the write system index signal is changed, and in this case, the read system index signal cycle must be reset.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus which does not require resetting of the reading index signal period even when the writing index signal period changes.

[0009]

Therefore, in the image forming apparatus of the present invention, the reading means for reading the image of the original by the photoelectric conversion element, and the plurality of modulated images based on the image information read by the reading means. An image forming apparatus comprising: a writing unit configured to scan a recording medium by controlling a laser beam by a synchronization signal to record an image of the original on the recording medium, the writing unit generating a synchronization signal of the writing unit. System synchronizing signal generating means, cycle measuring means for measuring the period of the generated writing system synchronizing signal, dividing means for dividing the measured period of the writing system synchronizing signal by the number of laser beams, and the calculated value of the dividing means next time. Reading system synchronizing signal cycle setting means for setting the reading system synchronizing signal cycle during the writing scanning period of the writing system, and issuing the reading system synchronizing signal at the set cycle. A reading system synchronizing signal generation means for, configured to include a reading control means for controlling the reading by the reading means on the basis of the read system synchronizing signal generated by the set period.

Further, one of a plurality of read system synchronization signals generated from the read system synchronization signal generating means is synchronized with the write system synchronization signal within one write scanning period.

[0011]

In this structure, the period of the writing system synchronizing signal at that time is measured for each one writing scanning period controlled based on the writing system synchronizing signal, and the reading value is obtained by dividing the measured value by the number of laser beams. A plurality of reading-system synchronizing signals are generated and the reading is controlled at the period of the synchronizing signal, which is calculated in the next writing scanning period.
As a result, even if the cycle of the writing-system synchronizing signal changes, the cycle of the reading-system synchronizing signal is automatically adjusted each time, so that a uniform image signal can be obtained.

Further, by synchronizing one of a plurality of reading system synchronizing signals generated in one writing scanning period with the writing system synchronizing signal, the writing system and the reading system can be surely synchronized. Becomes

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a digital copying machine as an embodiment of an image forming apparatus according to the present invention. In FIG. 1, the digital copying machine of this embodiment is
It is composed of a scanner unit (reading unit) 1, an image processing unit 2 and a printer unit (writing unit) 3.

By driving the scanner unit 1 to optically scan the original 4, the image information of the original 4 is converted into an optical image, which is read by a line sensor composed of a CCD and the optical image is converted into an electrical signal ( Photoelectrically converted into electrical image information). The electric signal (analog signal) output from the scanner unit 1 is converted into a digital signal in the image processing unit 2 and subjected to various processing such as density conversion and scaling processing, and then output to the printer unit 3. To be done.

In the printer section 3, an image is recorded based on a digital signal (image data) of a predetermined bit formed by the image processing section 2. FIG. 2 shows a circuit configuration of the printer unit 3. In FIG. 2, the printer unit 3 is configured to record three lines simultaneously by three laser beams. The digital image data DATA of each line transferred from the image processing unit 2 are modulated circuits 11a, 11b, 11 respectively.
image data DATA and data clocks DCK1, DCK in the modulation circuits 11a, 11b, 11c.
2, a signal based on DCK3 is formed.

The signals from the modulation circuits 11a, 11b, 11c are supplied to the semiconductor lasers 13a, 13b, 13c via the laser drive circuits 12a, 12b, 12c, respectively, and three signals are modulated based on the image data. Image recording is performed with a laser beam. The laser drive circuits 12a, 12b, 12c are controlled by a control signal from the tamming circuit 14 so that they are driven only in the horizontal and vertical effective sections.

Each laser drive circuit 12a, 12b, 12c
A signal indicating the laser beam light amount from the semiconductor lasers 13a, 13b, 13c is fed back to the semiconductor lasers 13a, 13b, 1 so that the light amount becomes constant.
The drive of 3c is controlled. Semiconductor lasers 13a, 13
As shown in FIG. 3, the three laser beams respectively output from b and 13c are associated with the corresponding condenser lenses 15a and 1a.
It is formed into parallel beams by 5b and 15c, is deflected by the beam splitters 16a and 16b, and is irradiated onto the polygon mirror 17. The laser beam deflected by the polygon mirror 17 is scanned on the photosensitive drum (recording medium) 19 via the fθ lens 18. As a result, exposure corresponding to the image data is simultaneously performed for three lines, and an electrostatic latent image is formed on the photoconductor drum 19.

The scanning start point of the laser beam deflected by the polygon mirror 17 is reflected by the reflection mirror 20 and guided to the index sensor 21 when the laser beam is applied to the tip of the scanning line. Then, it is detected by the index sensor 21. The detection signal is supplied to the index signal generating circuit (write system synchronizing signal generation means) 22, an index signal (sync signal) for respectively controlling the recording start of each laser beam by the index signal generating circuit 22 S _W
Is formed.

The index signal S _W is _supplied to the synchronizing circuit 2
3 is supplied. The synchronization circuit 23, an oscillation circuit 24 basic clock CK having a predetermined frequency is supplied from the index signal S _W divided output in synchronism with the DCK1, DC
Outputs K2 and DCK3. The frequency division output DCK1, D
CK2 and DCK3 are modulation circuits 11a and 11 respectively.
The data clock is supplied to b and 11c.

The motor drive circuit 25 is a polygon mirror 1
It drives a motor that rotates 7, and its on / off control signal is supplied from a timing circuit 14. Since the reading frequency of the scanner unit 1 is equal to the writing frequency of the printer unit 3 divided by the number of beams, the index signal S of the printer unit 3 is obtained.
Within one cycle of _W (one scanning period), the scanner unit 1
Index signal, i.e. with an index signal S _W of system writes one of the reading system index signal S _R, others may be preliminarily determined from the period and the number of beams of the index signal S _W, but in this case the , when the period of the index signal S _W of the write system is varied,
The period of the reading system index signal S _R is not constant, which causes image unevenness, which is not preferable.

[0021] Therefore, in this embodiment, actually it measures the period of the index signal S _W of the printer portion 3 for each scan,
The next reading frequency in the scanner unit 1 is set every time based on the measured value. FIG. 4 shows the reading timing control unit of the scanner unit 1. In the figure, the write system index signal S from the printer unit 3
1 clock width synchronization signal (WINDY) by inputting _W
And the WIN from the synchronization circuit 41.
A first counter (cycle measuring means) 42 that is reset by the input of DY and starts counting the clock signal CK
A register 43 for loading the count value of the first counter 42 by inputting WINDY, a divider (divider) 44 for dividing the value of the register 43 by the number of laser beams in the printer unit 3, and a clock CK for counting. Two
The counter 45, a comparator (reading system synchronizing signal cycle setting means) 46 whose output becomes “1” when the value of the second counter 45 reaches the calculated value of the divider 44, and WINDY from the synchronizing circuit 41 are compared. An index selector 47 for selecting the output of the device 46 based on the number of beams to generate a read system index signal S _R , and an index selector 4
7 and a timing generation circuit (reading control means) 48 for driving and controlling the line sensor 49 in response to the input of the index signal S _R from 7.

Next, the operation of the circuit of FIG. 4 will be described with reference to the timing chart of FIG. When the index signal S _W of the write system with a printer section 3 to start of scanning of the laser beam is input to the synchronizing circuit 41, wherein the synchronization signal WINDY of one clock width is generated. This makes the first
The counter 42 is reset and starts counting the input clock CK. With the next occurrence of WINDY,
The first counter 42 is reset and starts counting the clock CK, while the register 43 loads the count value m of the first counter 42 at that time. Count value m loaded in the register 43 is the period of the write system index signal S _W.

Next, in the divider 44, the value m in the register 43 is divided by the number of beams 3, and the quotient n (= m / 3) is input to the comparator 46. In the comparator 46, the second counter 45
The output of "1" is generated when the clock count value of 1 becomes equal to the value n from the divider 44. That is, the comparator 46
The output becomes "1" every time the number of clocks becomes n. here,
The cycle in which the output of the comparator 46 becomes "1" is set as the cycle of the reading system index signal S _R.

In the index selector 47, the output of the comparator 46 input to the A terminal and the WINDY of the synchronizing circuit 41 input to the B terminal are selected based on the number of beams,
A reading system index signal S _R is generated. here,
When the number of beams is 3 as in this embodiment, WINDY
Is input, the output of the comparator 46 is selected until the output from the comparator 46 is input twice, the reading system index signal S _R is generated in synchronization with the output of the comparator 46, and then the WINDY side Is selected and the index signal S _R is generated in synchronization with the input of WINDY. When the number of beams is 2, WINDY and the output of the comparator 46 are alternately selected and the reading system index signal S _R is generated in synchronization with each input.

Then, in synchronization with the generation of the index signal S _R from the index selector 47, the timing generation circuit 48 drives and controls the line sensor 49 to perform the next reading operation. In this way, the cycle of the write-system index signal S _W is actually measured for each writing scan, and the cycle of the read-system index signal S _R is automatically calculated for each read operation based on the measured cycle and the number of beams. For adjustment, as shown in FIG. 6, even if the cycle T of the write-system index signal changes to the cycle T'due to the uneven rotation of the polygon mirror or the like or the change of the cycle, as in the conventional case shown in FIG. 3 in writing scan period
The periods of the three reading system index signals are not different, and the periods t of the three reading system index signals S _R within one writing scanning period are automatically corrected to a constant period t ′, which is even. Images can be obtained. Further, even when the write cycle is changed, it is not necessary to reset the read system cycle. Furthermore, it is possible to be caused to be synchronized with one write system index signal S _W of a plurality of reading system index signal S _R in one write scan period, the synchronization of the write system and reading system to ensure.

In this embodiment, the case where the number of laser beams is 3 has been described, but the same can be applied when the number of laser beams is 2 or more. Further, the configuration is such that one of the plurality of read system index signals S _R is synchronized with the write system index signal S _W in one write scan period, but the present invention is not limited to this, and is based on the operation result of the divider. All reading system index signals S by value
_R may be generated.

[0027]

As described above, according to the present invention, in an image forming apparatus which scans a recording medium by using a plurality of laser beams to record a read image, a synchronization signal generated in a writing system is generated. Since the configuration is such that the cycle is measured and the next sync signal for the read system is generated based on the measured cycle, the cycle of the sync signal for the read system is automatically set even if the cycle of the sync signal for the write system changes. It can be corrected and a consistent image can be obtained. Further, it is not necessary to reset the reading system cycle.

Further, by synchronizing one of the reading system synchronizing signals with the writing system synchronizing signal within one writing scanning period, the writing system and the reading system can be surely synchronized.

[Brief description of drawings]

FIG. 1 is a schematic system diagram of an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a printer unit according to the embodiment.

FIG. 3 is a configuration diagram showing an image exposure system in the printer unit of the above.

FIG. 4 is a block diagram showing a circuit configuration of a main part of a scanner unit according to the embodiment.

FIG. 5 is a timing chart of the sync signal generation operation of the scanner unit of the above.

FIG. 6 is a diagram for explaining a change state of a read system synchronization signal cycle when a write system synchronization signal cycle is changed in the embodiment.

FIG. 7 is a diagram for explaining a change state of a reading system synchronization signal period when the conventional writing system synchronization signal period changes.

[Explanation of symbols]

 1 Scanner Section 3 Printer Sections 13a to 13c Semiconductor Laser 17 Polygon Mirror 19 Photosensitive Drum 21 Index Sensor 22 Index Signal Generating Circuit 23 Synchronous Circuit (Write System) 41 Synchronous Circuit (Read System) 42 First Counter 44 Divider 45 Second Counter 46 Comparator 48 Timing Generation Circuit 49 Line Sensor

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Claims (2)

[Claims] 1. A reading means for reading an image of an original by a photoelectric conversion element, and a plurality of laser beams modulated based on image information read by the reading means are controlled by a synchronizing signal to scan a recording medium. An image forming apparatus comprising: a writing unit for recording an image of the original on the recording medium, wherein a writing system synchronizing signal generating unit for generating a synchronizing signal of the writing unit and a cycle of the generated writing system synchronizing signal. A period measuring means for measuring the period, a dividing means for dividing the period of the measured writing system synchronizing signal by the number of laser beams, and a reading for setting the calculated value of the dividing means as the reading system synchronizing signal period in the next writing scanning period. System synchronizing signal cycle setting means, reading system synchronizing signal generating means for generating a reading system synchronizing signal at a set cycle, An image forming apparatus characterized in that it is configured to include a reading control means, the controlling the reading by the reading means on the basis of the read system synchronizing signal generated by the cycle. 2. The constitution according to claim 1, wherein one of a plurality of reading system synchronizing signals generated from said reading system synchronizing signal generating means is synchronized with a writing system synchronizing signal within one writing scanning period. Image forming apparatus.