JPH10109441A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device, with which neighboring light beams can easily be synchronized with each other and respective beam intensities can be uniformized. SOLUTION: In a constitution, in which a photosensitive body drum 309 is scanned with light beam and, at the same time, light beams are synchronized to the main scanning direction of the light beam with each other on the basis of the output of a light sensor 305, which is provide outside an image region so as to receive light beams, a detecting device 306 of the extremum of photosensor output for detecting the maxima or minima of the photosensor output is equipped so as to generate the synchronizing signals 323 and 324 when the maxima of the photosensor output are obtained in the device 306 of the extremum of the photosensor output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital copying machine,
The present invention relates to an image forming apparatus having an optical scanning device used for a writing system such as a laser printer, and more particularly to an image forming apparatus having an optical scanning device that remarkably improves a recording speed by forming a multi-beam.

[0002]

2. Description of the Related Art In such a conventional optical scanning device, it is common to scan a photosensitive member with one light beam.
A multi-beam type optical scanning device configured to scan a plurality of light beams simultaneously has been put to practical use in order to increase the recording speed as compared with the case of scanning with a light beam. As a technique for realizing a multi-beam optical scanning device, for example, a method of combining light beams of a plurality of semiconductor lasers has been proposed.

In the optical scanning apparatus using a plurality of laser beams as described above, setting a synchronization signal for each of the beams and individually controlling the modulation of the light source is necessary in order to avoid a deviation of the scanning position. Required. Conventionally, various methods have been proposed. For example, there is a method in which, after the same segment signal corresponding to the incidence of the first beam is detected, an appropriate delay is given to use it as a second synchronization signal. However, according to the above method, the interval between the two beams may vary depending on the use environment, so that it is difficult to form a synchronization signal with high accuracy, and it is necessary to adjust the delay time with high accuracy. However, there is a problem that the mass production effect is not excellent.

As a method of solving such a problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 02-188713, beams incident on an optical sensor are sequentially detected in time series, and a synchronization signal of each beam is detected. Something to do is suggested. Japanese Patent Application Laid-Open No. 06-246964 generates a frequency-divided signal at the rise of the detected optical sensor output, and further activates each of the two multivibrators at the rise / fall of the divided signal. With the configuration as a trigger, a synchronization signal of two beams is obtained.

[0005] Generally, of the area scanned by the light beam,
By arranging an optical sensor outside the image area and binarizing the photoelectric polarization conversion of the optical sensor at an appropriate threshold level,
The synchronization signal of the light beam can be obtained. Here, as described above, by synchronizing the output of each optical sensor that scans the optical sensor in time series independently with each other, synchronous signals of a plurality of light beams are obtained independently.

[0006]

However, since the beam intensity of the light beam has a Gaussian distribution, the two beams are sufficiently separated in time as shown in FIG. However, when the two beams are close in time as shown in FIG. 17, the optical sensor output signals A and B for the two beams are easy to classify. There is a disadvantage that the signal C is synthesized and becomes a signal C, and it becomes impossible to separate two light beams to obtain a synchronization signal. When two beams are close to each other as shown in FIG. 16 but they are separated from each other so as not to form a waveform forming one vertex, the signals A and B are separated so as to be binarized. Needed to adjust the threshold for.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art. It is possible to easily synchronize adjacent light beams, and to make uniform the intensity of each beam. It is an object of the present invention to provide an image forming apparatus having a simple configuration.

[0008]

In order to achieve the above object, an image forming apparatus according to the present invention comprises an optical sensor for scanning an object to be scanned with a light beam and receiving the light beam provided outside an image area. In an image forming apparatus having an optical scanning device that synchronizes the light beam in the main scanning direction based on an output, an optical sensor output pole that differentiates an output of the optical sensor and detects a maximum value or a minimum value of the optical sensor output. And a synchronizing signal for the light beam when a maximum value of the optical sensor output is obtained by the optical sensor output extreme value detecting device.

According to the image forming apparatus of the present invention having the above-described configuration, a synchronization signal is generated at the time when the extreme value based on the differential value and the maximum value are generated, so that the synchronization of the light beam is ensured. Can be

Alternatively, an image forming apparatus according to the present invention comprises:
The object to be scanned is scanned by a plurality of (N) light beams, and the synchronization of the plurality of light beams in the main scanning direction is performed based on the output of an optical sensor that receives the light beams provided outside the image area. An image forming apparatus having an optical scanning device, comprising: an optical sensor output extreme value detecting device that differentiates the output of the optical sensor and detects a local maximum value or a local minimum value of the optical sensor output; A synchronizing signal for each of the plurality of light beams is generated when a maximum value of the optical sensor output is obtained by the device.

According to the above configuration, it is easy to synchronize the light beams so close that the combined wave does not form a waveform having one vertex.

Further, the image forming apparatus according to the present invention scans an object to be scanned with a plurality of (N) light beams, and based on an output of an optical sensor provided outside the image area and receiving the light beams. An image forming apparatus having an optical scanning device for synchronizing the plurality of light beams in the main scanning direction, wherein an output of the optical sensor is differentiated to detect a maximum value or a minimum value of the optical sensor output. A light beam intensity adjusting device for adjusting the beam intensity of the light beam, wherein the plurality of light beams are obtained at the time when the minimum value is obtained by the optical sensor output detected by the optical sensor output extreme value detecting device. While generating the synchronization signal of each beam, the time at which the minimum value is obtained by the optical sensor output detected by the optical sensor output extreme value detection device is the time at which the two maximum values which are temporally before and after are obtained. And adjusting the plurality of light beams each of said light beam intensity to be placed between.

Therefore, with the above configuration, the beam intensity of each light beam is made uniform.

[0014]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram of an embodiment of an image forming apparatus according to the present invention. Print data 320 input from a scanner, an image memory (not shown) or the like is divided into even-line data and odd-line data by a print control unit 301, and the semiconductor lasers 10 and 11 in a light source unit 303 are passed through a semiconductor laser control unit 302. Modulation signal. Further, the semiconductor laser control unit 302 outputs a modulation signal for causing the light source unit 303 to emit a semiconductor laser so that the laser beam is incident on the optical sensor 305 arranged outside the image area.

In the light source unit 303, the print data for two lines is converted into two semiconductor laser beams, and is combined by the beam combining prism 19. Beam combining prism 1
9 are deflected in common by the polygon mirror 304, and the two laser beams L1 and L2
9 is exposed. Further, the two laser beams L1 and L2 scan the optical sensor 305 outside the image area in the scanning area, and the optical sensor 305 photoelectrically converts the light beams sequentially incident in a time series into an optical sensor output 321. Is output to the optical sensor output extreme value detecting device 306.

The optical sensor output extreme value detecting device 306 of the present invention.
Receives the optical sensor output 321 from the optical sensor 305, differentiates it, detects the maximum value / minimum value, and sets it as the optical sensor output extreme value signal 322. Synchronous signal generator 307
Generates an odd line synchronization signal 323 and an even line synchronization signal 324, which are synchronization signals for each line, based on the optical sensor output extreme value signal 322, and outputs them to the print control unit 301.
The print control unit 301 determines the print data write timing of each line based on the odd line synchronization signal 323 and the even line synchronization signal 324. Further, the print control unit 301
The synchronous reset signal 329 is sent to the synchronous signal generator 30
7 is reset.

According to the present invention, as described above, the light sensor output 32
Since the local maximum point (the peak of the light beam intensity) is a synchronization timing, a synchronization signal for each line is generated.
Even when two light beams are close to each other and separation is difficult, each line can be easily synchronized.

Next, each of the above components will be described.
FIG. 2 is an exploded perspective view illustrating the configuration of the light source unit 303 shown in FIG. FIG. 3 is an explanatory diagram of the sub-scanning pitch. Hereinafter, the principle of beam combining in the apparatus of the present invention will be described with reference to FIGS. As shown in FIG. 2, the light source unit 303 is configured to combine and emit light beams L1 and L2 generated by the two semiconductor lasers 10 and 11. Each of the two semiconductor lasers 10 and 11 has a direction perpendicular to the pn junction plane as X.
The laser beams that are arranged on the same plane so as to coincide with the directions of the 0 axis and the X1 axis and emitted are collimator lenses 12 and 13
The laser beams are shaped into laser beams 14 and 15 each having a parallel beam diameter.

Of these light beams, one of the light beams 15 is incident on the beam combining prism 19 with the polarization plane rotated by 90 ° by the half-wave plate 18, is internally reflected at an inclination 19 a, and is further reflected on the polarization beam splitter surface. The light is reflected by 19b and is synthesized near the optical axis of the light flux 14 serving as a reference.

In this case, the semiconductor laser 11 and the collimator lens 13 are slightly decentered. Thereby, the light is emitted at a predetermined angle α in the main scanning direction, and as shown in FIG. 2, the entire light source device is rotated around the optical axis on the recording surface at an interval L in the main scanning direction. By rotating, the sub-scanning pitch can be made variable. In the figure, P1 and θ1 have the highest resolution and the narrowest sub-scanning pitch, and P2 and θ2 are next.

In addition to the configuration example using two semiconductor lasers as described above, the light source may be configured by a semiconductor laser array having a plurality of light emitting points that can be independently modulated in one chip.

FIG. 4 is an explanatory diagram of a configuration example and operation of an optical sensor applied to the image forming apparatus according to the present invention. Although a photodiode is generally used as a device constituting the optical sensor 305, the light receiving surface of the photodiode is larger than the beam diameter of the light beam. The received light energy is an integral amount while the beam is scanning the photodiode, and thus, for example, FIG.
A Gaussian distribution as shown in FIG. 7 cannot be observed.

Therefore, in the present invention, the optical sensor 305 is configured by arranging a slit smaller than the beam diameter on the light receiving surface as shown in FIG. With this configuration, it is possible to detect the light beam energy for each minute area in the scanning direction, and the detection accuracy is improved.

FIG. 5 is an explanatory diagram of a configuration example of an optical sensor output extreme value detecting device applied to the image forming apparatus according to the present invention. FIG. 6 shows two light beams incident on the optical sensor output, and FIG. 7 shows a signal obtained by differentiating the optical sensor output. Further, FIG. 8 shows the extreme value signal of the optical sensor output. Here, two light beams A and B incident on the optical sensor 305
Are in a partially superposed positional relationship as shown in FIG. Therefore, the optical sensor output differentiating device 501 in the optical sensor output extreme value detecting device 306 differentiates the optical sensor output 321 into a waveform as shown in FIG. Next, the comparator 502 compares the differentiated waveform signal with a signal of 0 V, and makes a waveform that rises when the voltage changes from a minus voltage to a plus voltage and falls when the voltage changes from a plus voltage to a minus voltage, and converts the waveform into an optical sensor. The output extreme value signal 322 is used.

That is, the optical sensor output extreme value signal 322
Is a signal that rises when the optical sensor output 321 reaches a local minimum value and falls when the optical sensor output 321 reaches a local maximum value, as shown in FIG. The present invention provides an optical sensor output extreme value signal 322.
, The synchronization timing of each line is set at the falling edge of. Although FIG. 5 shows a simple configuration example using an operational amplifier, a more precise circuit configuration can be used when more accurate differentiation operation and comparison operation are required.

FIG. 9 shows an example of the configuration of the synchronization signal generator 307. FIG. 10 shows a timing chart of each signal of the synchronization signal generator 307. As described above, the synchronization timing of each line can be obtained at the falling edge of the optical sensor extreme value detection signal 322. Therefore, the JK latches 702 and 703 rising at the falling edge of the optical sensor output extreme value detection signal 322 for each line are used. Configure to provide. At this time, in order to mask the synchronization signal other than the line for which the synchronization signal is to be started, the mask sequencer 7 is used.
01, the synchronization mask signals 731 and 732 of each line
Generate

The odd line synchronizing mask signal 731 first rises by the synchronizing reset signal 329 output in advance before detecting synchronization in each line, and falls at the first falling of the optical sensor output extreme value detection signal 322. To The even line synchronization mask signal 732 rises at the first falling edge of the optical sensor output extreme value detection signal 322, and falls at the second falling edge of the optical sensor output extreme value detection signal 322.

Since each synchronization mask signal is wired to the CLR pin of each JK latch, no synchronization signal is output when the corresponding synchronization mask signal is L. Further, since the synchronization mask signal for each line falls at each falling edge of the optical sensor output extreme value detection signal 322, the synchronization signal for each line falls at the next moment after rising, and the pulse width is reduced. Can be shorter.

In the above embodiment, an example has been described in which N is set to 2 and two beams of odd lines and even lines are used. Even when N is 3 or more, a synchronization signal corresponding to each beam is generated. It may be configured as follows.

FIG. 11 is a block diagram of another embodiment of the image forming apparatus according to the present invention. Another embodiment will be described below with reference to FIG. Note that the same parts as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in the figure, the light beam intensity adjusting device 408 sends a light beam to the semiconductor laser controller 302 based on the maximum value and the minimum value of the light beam obtained from the light sensor output extreme value signal 322. Intensity adjustment signals 425, 426
Is output.

In general, since the beam intensities of a plurality of light beams vary, it is necessary to adjust the output power by measuring the beam intensity of each beam. When a plurality of beams are close to each other so that the combined wave does not form a waveform having one vertex, the time when the minimum value is obtained at the foot between the two beams is almost two when the intensity of the two beams is equal. It is at the center of the maximum value of the beam (the peak of the light beam intensity). If the beam intensity of one of the beams is large,
The local minimum value is offset as in 2.

If the modulation signal to the semiconductor laser is adjusted so that the minimum value is at the center, the beam intensities of the two beams become substantially equal. Therefore, in the present embodiment, the semiconductor laser control unit 302 is required to set the time point at which the minimum value of the optical sensor output extreme value signal 322 is obtained to be halfway between the time points at which the two local maximum values are temporally changed. On the other hand,
Light beam intensity adjustment signals 425 and 426 are output. The light beam intensity adjustment signals 425 and 426 are, for example, the time from the maximum value of the light beam on the odd line to the next minimum value and the time from the minimum value to the maximum value of the light beam on the even line.

FIG. 13 shows a light beam intensity adjusting device 408.
An example of the configuration will be described. FIG. 14 shows a light beam intensity adjusting device 4.
08 shows a timing chart of each signal.

The JK latch 903 and the D latch 904 are first reset by a synchronization reset signal 329 output in advance before detecting synchronization in each line. The odd line beam intensity adjustment counter 901 starts counting at the rising edge of the output Q of the JK latch 903 that toggles at the falling edge of the optical sensor output extreme value detection signal 322, and toggles at the rising edge of the optical sensor output extreme value detecting signal 322. The counting is terminated at the rising edge of the inverted output Q bar of the D latch 904.

Counter 902 for adjusting even line beam intensity
Is configured to start counting at the rising edge of the inverted output Q bar of the D latch 904 and end counting at the rising edge of the inverted output Q bar of the JK latch 903. The time To between the maximum value of the odd line beam counted by the odd line beam intensity adjustment counter 901 and the next minimum value To
d becomes the odd line light beam intensity adjustment signal 425, and the time Te from the minimum value counted by the even line beam intensity adjustment counter 902 to the maximum value of the even line beam.
v becomes an even-line light beam intensity adjustment signal 426.

The semiconductor laser controller refers to the light beam intensity adjustment signals 425 and 426, and adjusts the modulation signal to the semiconductor laser so that each beam intensity adjustment signal becomes equal. That is, when the odd-line light beam intensity adjustment signal 425 is smaller than the even-line light beam intensity adjustment signal 426, the even-line beam intensity is higher than the odd-line beam intensity. Try to weaken.

In the above-described embodiment, an example has been described in which N is set to 2 and two beams of an odd line and an even line are used. However, even when N is 3 or more, the local maximum value of each beam and the next line What is necessary is just to comprise so that the time of the minimum value with a beam may be counted.

[0039]

As described in detail above, claim 1 of the present invention
An image forming apparatus according to (1), which scans an object to be scanned with a light beam, and synchronizes the light beam in a main scanning direction based on an output of a light sensor provided outside the image area and receiving the light beam. An image forming apparatus having an optical sensor output extreme value detecting device that differentiates the output of the optical sensor and detects a local maximum value or a local minimum value of the optical sensor output, and the optical sensor output extreme value detecting device detects the optical sensor output. Since the configuration is such that the synchronization signal of the light beam is generated at the time when the maximum value is obtained, there is an effect that the synchronization can be ensured.

An image forming apparatus according to a second aspect of the present invention comprises:
A light that scans the object to be scanned with a plurality of (N) light beams and synchronizes the plurality of light beams in a main scanning direction based on an output of an optical sensor provided outside the image area and receiving the light beams. An image forming apparatus having a scanning device includes an optical sensor output extreme value detecting device that differentiates the output of the optical sensor and detects a maximum value or a minimum value of the optical sensor output. Since the synchronization signal of each light beam is generated when the maximum value of the output is obtained, it is easy to synchronize the light beams so close that the synthesized wave does not have a waveform having one vertex. be able to.

An image forming apparatus according to a third aspect of the present invention comprises:
The object to be scanned is scanned by a plurality of (N) light beams, and the plurality of light beams are synchronized in the main scanning direction based on the output of an optical sensor that receives the light beams provided outside the image area. In an image forming apparatus having an optical scanning device, an optical sensor output extreme value detecting device for differentiating the output of the optical sensor and detecting a maximum value or a minimum value of the optical sensor output and a light beam intensity adjustment for adjusting the beam intensity of the light beam. A device for generating a synchronization signal for each light beam when a maximum value of the optical sensor output is obtained by the optical sensor output extreme value detection device so that the adjacent light beams can be synchronized independently. The light beam of each of the light beams is such that the time at which the minimum value is obtained from the optical sensor output detected by the optical sensor output extreme value detection device is intermediate between the time points at which the two local maximum values are temporally changed. Since the intensity is adjusted, it is possible to easily synchronize the light beams so close that the combined wave does not form a waveform having one vertex, and to equalize the beam intensity of each beam. it can.

[Brief description of the drawings]

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

FIG. 2 is an exploded perspective view showing a configuration example of a light source unit applied to the image forming apparatus according to the present invention.

FIG. 3 is a diagram illustrating the principle of the light source unit shown in FIG. 2;

FIG. 4 is an explanatory diagram of a configuration example and operation of an optical sensor applied to the image forming apparatus according to the present invention.

FIG. 5 is an explanatory diagram of a configuration example of an optical sensor output extreme value detection device applied to the image forming apparatus according to the present invention.

FIG. 6 is an operation explanatory view of the optical sensor output extreme value detecting device shown in FIG. 5;

FIG. 7 is an operation explanatory view of the optical sensor output extreme value detecting device shown in FIG. 5;

8 is an operation explanatory view of the optical sensor output extreme value detecting device shown in FIG. 5;

FIG. 9 is a block diagram of a configuration example of the synchronization signal generator shown in FIG. 1;

10 is a timing chart of each signal of the synchronization signal generator shown in FIG.

FIG. 11 is a block diagram of another embodiment of the image forming apparatus according to the present invention.

FIG. 12 is an explanatory diagram of a beam intensity difference.

13 is a block diagram of a configuration example of the synchronization signal generator shown in FIG.

14 is a timing chart of each signal of the synchronization signal generator shown in FIG.

FIG. 15 is an explanatory diagram of a superimposed state of beams.

FIG. 16 is an explanatory diagram of a superimposed state of beams.

FIG. 17 is an explanatory diagram of a superimposed state of beams.

[Explanation of symbols]

 1 Image forming apparatus according to the present invention 10 Semiconductor laser 11 Semiconductor laser 19 Beam combining prism 301 Print control unit 302 Semiconductor laser control unit 303 Light source unit 304 Polygon mirror 305 Optical sensor 306 Optical sensor output extreme value detector 307 Synchronous signal generator 309 Photoconductor drum 320 Print data 321 Optical sensor output 322 Optical sensor output extreme value signal 323 Synchronous signal 324 Synchronous signal 329 Synchronous reset signal

Claims (3)

[Claims] An optical scanning device that scans an object to be scanned by a light beam and synchronizes the light beam in a main scanning direction based on an output of an optical sensor that receives the light beam provided outside an image area. An image forming apparatus having an optical sensor output extreme value detecting device for differentiating the output of the optical sensor and detecting a local maximum value or a local minimum value of the optical sensor output. An image forming apparatus for generating a synchronizing signal of the light beam when a maximum value is obtained. 2. A scanning target object is scanned by a plurality of (N) light beams, and a main light beam of the plurality of light beams is output based on an output of a light sensor provided outside the image area and receiving the light beams. An image forming apparatus having an optical scanning device that synchronizes in a scanning direction, comprising: an optical sensor output extreme value detecting device that differentiates an output of the optical sensor and detects a maximum value or a minimum value of the optical sensor output; An image forming apparatus, wherein a synchronizing signal for each of the plurality of light beams is generated when a maximum value of an optical sensor output is obtained by a sensor output extreme value detecting device. 3. A scanning target is scanned by a plurality of (N) light beams, and a main light beam of the plurality of light beams is output based on an output of a light sensor provided outside the image area and receiving the light beams. In an image forming apparatus having an optical scanning device that synchronizes in a scanning direction, an optical sensor output extreme value detecting device that differentiates the output of the optical sensor and detects a maximum value or a minimum value of the optical sensor output,
A light beam intensity adjusting device that adjusts a beam intensity of the light beam; a synchronization signal of each of the plurality of light beams at a time when a minimum value is obtained at an optical sensor output detected by the optical sensor output extreme value detecting device. And the point at which the local minimum value is obtained by the optical sensor output detected by the optical sensor output extreme value detection device is arranged in the middle of the point in time at which two local maximum values are obtained before and after in time. An image forming apparatus, wherein the light beam intensity of each of a plurality of light beams is adjusted.