JP2002029090A - Imaging apparatus and laser beam printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus which can output horizontal sync signals corresponding to respective laser beams stably based on laser beams impinging on a light receiving element with a time difference. SOLUTION: The imaging apparatus comprises means for modulating a plurality of laser beams by an image signal, means for scanning a photosensitive body with a modulated laser beam, and means for generating a horizontal sync signal by converting the plurality of laser beams photoelectrically wherein the horizontal sync signal generating means is irradiated with the plurality of laser beams with a time difference. The imaging apparatus is further provided a laser emission control means for causing to emit a plurality of laser beams forcibly immediately before the horizontal sync signal generating means is scanned by the plurality of laser beams and unlighting a first laser beam when the horizontal sync signal generating means generates a horizontal sync signal by the first laser beam at least before the horizontal sync signal generating means is scanned by a second laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary polygon mirror for scanning a laser beam modulated by an image signal on a photosensitive member which is an image forming surface, and to a plurality of laser beams modulated by the image signal. And an image forming apparatus for forming an image. Further, the present invention relates to a laser beam printer including the image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, a laser beam printer having such an image forming apparatus has a configuration as shown in FIG.

[0003] In the laser beam printer main body 100, reference numeral 110 denotes a process cartridge that can be attached to and detached from the laser beam printer 100. Process cartridge 1
A photosensitive drum 10 on which an electrostatic latent image is formed
2. A charging roller for uniformly charging the photosensitive drum 102 and a developing device for developing an electrostatic latent image formed on the photosensitive drum 102 by a laser beam with toner are provided. Reference numeral 101 denotes an optical unit, which is provided for scanning the photosensitive drum 102 with a laser beam. A transfer roller charger 103 transfers a toner image formed on the photosensitive drum 102 to a predetermined sheet.
Reference numeral 04 denotes a fixing device that melts the toner on the paper and fixes the paper on the paper. Reference numeral 106 denotes a discharge roller that discharges the fixed paper to the outside of the machine. A registration sensor 109 for detecting the leading edge of the paper, a cassette 109 for knowing in advance the size of the paper on which the paper is loaded, and a paper feed roller 108 for feeding paper from the cassette 109 are provided.

Next, the scanner unit 101 will be described.

FIG. 8 shows the internal configuration of the scanner unit 101. Reference numerals 208 and 209 denote semiconductor lasers that are turned on / off according to image signals.
Is a laser driver that drives the semiconductor lasers 208 and 209 according to an image signal from the engine control unit;
Reference numeral 211 denotes a collimator lens for converting diffused radiation of the laser light emitted from the semiconductor lasers 208 and 209 into parallel light, 212 denotes a cylindrical lens that reduces the parallelized laser light only in the vertical direction, and 202 denotes a rotating polygon mirror. A scanner motor 201 for rotating the scanner motor 202 based on a drive signal from the engine control unit 300
The scanner motor driver 203 drives the laser, 203 is a toric lens for returning the laser beam reflected by the rotating polygon mirror to parallel light again, and 207 receives the laser beam scanned by the rotating polygon mirror and reflected on the horizontal synchronization mirror 205. A horizontal synchronizing signal (/ BD signal, "/" indicates negative logic) for determining a writing start position of an image signal for each main scanning line is provided at a predetermined position outside an effective image area. A light receiving element (hereinafter referred to as a “BD sensor”), 204 is a rotating polygon mirror and an imaging lens for correcting the optical path length of the photosensitive drum, and 206 is a reflection mirror. Reflection mirror 20
The laser beam reflected by 6 is applied to the photosensitive drum 102. The BD sensor 207 holds the maximum value of the received light amount, and outputs a horizontal synchronization signal when a light amount equal to or more than a predetermined ratio of the held value is incident.

Next, the operation of the scanner unit 101 will be described with reference to FIG.

When the engine controller 300 receives the print signal (/ PRNT) from the printer controller 301, it turns on the scanner drive signal (/ SCNON) for the scanner motor driver 201 and rotates the scanner motor 202. When the scanner motor reaches a normal rotation, the scanner motor driver 201 outputs / SCNRDY.
Set the signal to True. In response to this, engine control section 300 outputs the / LON signal to obtain the / BD signal.
e. When the / BD signal is obtained, the engine control unit 3
00 is the / LON signal (/ LON1 and / LO
N2). Thus, a / BD signal can be obtained for each scan. Further, the engine control unit 300 determines the printing area in the main scanning direction by using
After a certain period of time after receiving the BD signal, / ENBL1, /
The ENBL2 signal is set to True, and is set to False after the lapse of the scanning time for the print area. On the other hand, after a certain period of time after receiving the / BD signal, the printer controller 301 responds to the image signals as dot information by / VDO1, / VDO.
Drive two signals.

[0008]

In the above conventional example, in order to output the first and second / BD signals in a separated form, the first and second laser beams are separated and the photoelectric conversion is performed. It is necessary to have a narrow slit for input to the element and a high-speed photoelectric conversion element capable of terminating the photoelectric conversion between the time when the first laser beam is input and the time when the second laser beam is input. . In an inexpensive slit and photoelectric conversion element, as shown in FIG. 10, before the first laser beam is input and before the light amount of the first laser beam falls below the slice level (shown by a broken line), the second laser beam Is input, the sum of the light amount of the first laser beam and the light amount of the second laser beam exceeds the slice level, and the / BD signal separated into two cannot be output from the BD sensor 207. For that purpose, the first or second /
When control for synchronizing the image writing position in the main scanning direction is performed using one of the BD signals, the first and second / BD are controlled.
If the time difference between the signals changes, control cannot follow the change. That is, an image formed on the photoconductor by the first laser beam and an image formed on the photoconductor by the second laser beam are shifted in the main scanning direction. Also,
In order to avoid this, when transmitting a / BD signal of a narrow pulse, if the transmission path is long, the / BD signal may disappear during transmission.

Accordingly, an object of the present invention is to provide an image forming apparatus capable of stably outputting a horizontal synchronizing signal corresponding to each laser beam based on the laser beams incident on the light receiving element with a time difference. I do.

[0010]

According to the present invention, there is provided an image forming apparatus, comprising: means for modulating a plurality of laser beams with an image signal; means for scanning the modulated laser beam on a photosensitive member; And a horizontal synchronizing signal generating means for generating a horizontal synchronizing signal for horizontal synchronizing the image signal, wherein the plurality of laser beams irradiate the horizontal synchronizing signal generating means with a time difference from each other. In the printer, the plurality of laser beams forcibly emit the plurality of laser beams from near the time of scanning on the horizontal synchronization signal generating means,
When the horizontal synchronizing signal generating means generates the horizontal synchronizing signal by the first laser beam, at least the second
Before the laser scans on the horizontal synchronizing signal generating means, the laser light emitting control means for turning off the first laser beam is provided.

Further, in the image forming apparatus according to the present invention, in the above-mentioned image forming apparatus, the laser emission control means includes:
When the first laser beam is turned off, the second laser beam is emitted.

Further, the image forming apparatus according to the present invention, in the above-mentioned image forming apparatus, further comprises a separating unit for separating the horizontal synchronizing signal by the first laser beam and the horizontal synchronizing signal by the second laser beam. It is characterized by comprising means.

Further, the image forming apparatus according to the present invention, in the above-mentioned image forming apparatus, further comprises a waveform shaping means for waveform-forming the horizontal synchronizing signal separated by the separating means into a prescribed pulse width. And

A laser beam printer according to the present invention includes the above-described image forming apparatus.

[0015]

FIG. 2 is a waveform diagram showing the amounts of two laser beams input to the BD sensor 207 and the output of the corresponding BD sensor according to the embodiment of the present invention.

In this embodiment, the BD sensor outputs a / BD signal at the same time when the first laser beam reaches the slice level of the photoelectric conversion element of the BD sensor. A signal for forcibly emitting a first laser beam to detect a second / BD signal with a rising edge of the / BD signal as a trigger (hereinafter, referred to as an "unblanking signal")
To turn off the first laser beam. By extinguishing the first laser beam at the same time that the first laser beam is detected, the input of the photoelectric conversion element can be reduced to a slice level or less before the second laser beam is input to the BD sensor, Independent detection of the second laser beam becomes possible. As described above, in the present embodiment, it is possible to obtain a separated / BD signal for each of the first and second laser beams by using inexpensive photoelectric conversion elements and slits.

[Embodiment 1] FIG. 1 is a block diagram showing a configuration of a portion according to the present embodiment of an image forming apparatus according to Embodiment 1.

The image forming apparatus according to the present embodiment comprises a first semiconductor laser 1, a second semiconductor laser 2, a plurality of laser beams as inputs, and a photoelectric conversion element having a certain slice level for outputting a / BD signal. / BD signal detection means (BD sensor) 3, first unblanking signal generation means 5 for generating an unblanking signal for forcibly emitting a laser beam for detecting the / BD signal with the / BD signal detection means, second Unblanking signal generating means 16,
J input first unblanking signal, K input / BD signal
A JK flip-flop 4 is provided as an input and outputs a signal for controlling ON / OFF of the first laser beam.

Next, the operation will be described.

First, when the output of the first unblanking signal generating means 5 goes high, the output of the JK flip-flop 4 goes high, and the first laser 1 emits light. At the same time when the first laser beam emitted from the first laser 1 reaches the slice level of the photoelectric conversion element of the / BD signal detecting means 3, the / BD signal detecting means 3 outputs a / BD signal. With the rising edge of the / BD signal as a trigger, the output of the JK flip-flop 4 is reset,
This output turns off the first laser beam. By extinguishing the first laser beam at the same time that the first laser beam is detected, by setting the input light amount of the photoelectric conversion element to a slice level or less before the second laser beam is input,
The detection of the second laser beam is enabled, and the / BD signal detecting means 3 detects the /
The BD signal and the / BD signal for the second laser beam can be separated and output.

[Embodiment 2] FIG. 3 is a block diagram showing a configuration of a part according to the present embodiment of an image forming apparatus according to Embodiment 3.

The image forming apparatus according to the present embodiment comprises a first semiconductor laser 1, a second semiconductor laser 2, a plurality of laser beams as input / BD signal detecting means 3, and a first unblanking signal generating means 5 The output of the second unblanking signal generating means 6 and the / BD signal detecting means 3
A / BD signal switching means 7 for switching the generated / BD signal and outputting it to the first and second unblanking signal generating means 5 and 6 is provided.

FIG. 4 shows the relationship between the first and second unblanking signals output by the first and second unblanking signal generating means 5 and 6 of the present embodiment and the / BD signal output by the / BD signal detecting means 3. It is a timing chart.

Next, the operation will be described.

First, when the output of the first unblanking signal generating means 5 becomes High, the first laser 1 emits light (T101). When the / BD signal detecting means 3 detects the first laser beam (T102), the / BD signal switching means 7 sets the output destination to the first unblanking signal generating means 5 and outputs the signal 11. The signal 11 causes the first unblanking signal generation means 5 to set the first unblanking signal 13 to Low, and the second unblanking signal generation means 6 causes the second unblanking signal generation means 6 to change to the second state by the falling edge of the first unblanking signal 13. The unblanking signal is set to High (T103). Therefore, the first laser beam is turned off and the second laser beam emits light. / B
If the D signal detecting means 3 outputs the second / BD signal by the second laser beam (T104), the / BD signal switching means 7 sends the output destination to the first unblanking signal generating means 5 Switching to the second unblanking signal generating means 6 outputs the signal 12, and upon receiving the signal 12, the second unblanking signal generating means 6 sets the second unblanking signal to Low (T105).

According to the present embodiment, the first laser beam and the second laser beam are switched at time 103, so that the first and second laser beams can be switched even when the interval between the first and second laser beams is small. BD signals can be separated and output.

[Embodiment 3] FIG. 5 is a block diagram showing a configuration of a portion relating to the present embodiment of an image forming apparatus according to the embodiment.

The image forming apparatus according to the present embodiment includes a first semiconductor laser 1, a second semiconductor laser 2, a plurality of laser beams as input / BD signal detection means 3, and a first unblanking signal generation means 5 The output of the second unblanking signal generating means 6 and the / BD signal detecting means 3
/ BD signal switching means 7 for switching the generated / BD signal and outputting the signals to the first and second unblanking signal generating means 5 and 6, the narrow pulse input from the / BD signal switching means having a predetermined width. First and second / BD shaping means 8 and 9 for shaping into pulses are provided.

FIG. 6 shows the first and second unblanking signals output from the first and second unblanking signal generating means 5 and 6 of the present embodiment, the / BD signal output from the / BD signal detecting means 3, First and second / BD signal shaping means 8,
9 is a timing chart of the / BD1 signal and the / BD2 signal output by the output unit 9;

Next, the operation will be described.

The operations of the first and second unblanking signal generating means 5 and 6, the first and second lasers 1 and 2, the / BD signal detecting means 3, and the / BD signal switching means 7 are the same as those of the third embodiment. Therefore, a duplicate description will be omitted. The first and second / BD signal shaping means 8 and 9 convert the input separated narrow / BD signals 11 and 12 into / B signals having a predetermined width.
It is shaped into a D signal and output. Therefore, the disappearance of the / BD signal during transmission can be prevented.

[0032]

According to the present invention, the following effects can be expected.

It is not necessary to use a thin slit and a high-speed photoelectric conversion element, and by using an inexpensive slit and a photoelectric conversion element,
The / BD signals for a plurality of adjacent laser beams can be obtained in a separated form. By obtaining the / BD signal for each laser beam in a separated form, even when the interval between the / BD signals changes, the image writing position in the main scanning direction can be synchronized using each / BD signal. Thus, an image having good jitter characteristics, that is, an image having no shift in the main scanning direction can be obtained. By switching the blanking signal, a separated / BD signal can be obtained even when the distance between the two lasers is short. By shaping each of the obtained / BD signals into a prescribed pulse width, a stable / BD signal that does not disappear during transmission can be output.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 shows a horizontal synchronization signal (/ B) according to the first embodiment of the present invention.
FIG. 6 is a waveform diagram showing a generation process of a (D signal).

FIG. 3 is a diagram illustrating a configuration of an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a timing chart of signals generated by an image forming apparatus according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration of an image forming apparatus according to a third embodiment of the present invention.

FIG. 6 is a timing chart of signals generated by an image forming apparatus according to Embodiment 3 of the present invention.

FIG. 7 is an overall configuration diagram of a laser beam printer including an image forming apparatus according to the present invention and a conventional example.

FIG. 8 is a configuration diagram of an optical unit of an image forming apparatus according to the present invention and a conventional example.

FIG. 9 is a circuit block diagram of an image forming apparatus according to a conventional example.

FIG. 10 is a waveform diagram showing a process of generating a horizontal synchronization signal (/ BD signal) according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st laser 2 2nd laser 3 / BD signal detection means 4 JK flip-flop 5 1st unblanking signal generation means 6 2nd unblanking signal generation means 7 / BD signal switching means 8 1st / BD Shaping unit 9 Second / BD shaping unit 207 Horizontal synchronization signal detecting unit (BD sensor) 208, 209 Laser driver 300 Engine control unit

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2C362 BA56 BA69 BA70 BB30 BB31 BB32 BB33 2H045 AA01 BA02 BA22 BA32 CA88 CA97 5C072 AA03 BA13 HA02 HA06 HA13 HB02 HB08 HB11 UA20 XA05

Claims (5)

[Claims] A means for modulating a plurality of laser beams with an image signal; a means for scanning the photosensitive member with the modulated laser beam; and a means for photoelectrically converting the plurality of laser beams to perform horizontal synchronization of the image signal. Horizontal synchronizing signal generating means for generating a horizontal synchronizing signal for capturing, wherein the plurality of laser beams irradiate the horizontal synchronizing signal generating means with a time difference from each other. When the plurality of laser beams are forcibly emitted from near the time of scanning on the signal generating means and the horizontal synchronizing signal generating means generates the horizontal synchronizing signal by the first laser beam, the second laser coming at the latest at the latest Comprises a laser emission control unit for turning off the first laser beam before scanning on the horizontal synchronization signal generation unit. An image forming apparatus comprising: 2. An image forming apparatus according to claim 1, wherein said laser emission control means emits said second laser beam when said first laser beam is turned off. apparatus. 3. The image forming apparatus according to claim 1, further comprising a separating unit configured to separate the horizontal synchronization signal based on the first laser beam and the horizontal synchronization signal based on the second laser beam. An image forming apparatus comprising: 4. The image forming apparatus according to claim 3, further comprising a waveform shaping unit for waveform-forming the horizontal synchronization signal separated by the separation unit into a prescribed pulse width. apparatus. 5. A laser beam printer comprising the image forming apparatus according to claim 1.