JP2003025626A - Multibeam writing unit and imaging apparatus comprising it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multibeam writing unit in which image quality can be prevented from deteriorating by improving accuracy of the intensity of light of a sync detection signal. SOLUTION: The multibeam writing unit comprises a plurality of light emitting sources (laser light sources 10), a rotary polariscope (rotary scanning means 14) for polarizing/scanning a plurality of writing lights from respective light emitting sources simultaneously, optical lenses (11, 13, 17, 18, 20) constituting an optical system for scanning the plurality of writing lights, and a sync detection signal generating means having a photosensor 25 generating a sync signal for regulating the starting position of writing on the surface of a photosensitive body 21 and a sync detection mirror 23 wherein a plurality of beams are lighted at the time of generating the sync signal by irradiating the photosensor 25 with a light beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical (beam) writing apparatus for forming an optical writing latent image on a photoconductor, and more particularly to a multi-beam writing apparatus which adopts a writing method using a plurality of laser beams. The present invention relates to an image forming apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer or a copying machine using an electrophotographic method, a charging device uniformly charges the surface of a photosensitive member, and then an optical writing unit is used to handle externally recorded data. It is common to irradiate the surface of the photoconductor with a light beam to generate an electrostatic latent image.

In such an optical writing means, the light beam for irradiating the surface of the photoconductor is formed by condensing parallel light rays emitted from the laser diode, and the surface of the photoconductor is scanned by the rotating polarization means. At the time of such scanning, the optical writing means of the laser scanning optical system needs a synchronization signal that defines the writing start timing, and this signal is generated by the synchronization detection means provided at an arbitrary position of the optical writing means. . Further, as a method of forming an electrostatic latent image, a so-called binary recording method in which a light beam is turned on or off on a surface of a photoconductor has become popular. In the binary recording method, halftone reproduction is realized by performing image processing such as a dither method and an error diffusion method on the recording signal.

Then, an image visualization agent is attached to the electrostatic latent image formed on the surface of the photoconductor by a developing means to obtain a visualized image visualized on the surface of the photoconductor, and then the visualized image is transferred by a transfer means. Is transferred to a recording medium. Thereafter, the unfixed visualized image transferred to the recording medium is heated and pressed by the fixing means and fixed on the recording medium.

In recent years, in such an image forming apparatus, demands for higher pixel density and higher speed are increasing, and at the same time, demands for improving image quality are also increasing.
It is known that factors such as gradation, sharpness, and graininess that define image quality are greatly affected by the higher pixel density and higher speed. In particular, the positional accuracy of the dots forming the image greatly affects the gradation and sharpness. Further, the decrease in the accuracy of the synchronization signal that defines the write start timing causes the fluctuation of vertical lines and the like, which causes the deterioration of the image quality.

In an image forming apparatus with a pixel recording density of 1200 dpi and an optical writing frequency of 60 MHz, which the applicant of the present invention has begun to develop, according to experimental results, it is visually confirmed that when adjacent pixels cause a deviation of 1.5 pixels. It has been confirmed that line fluctuation is observed and sharpness or graininess deteriorates. The shift of 1.5 pixels is 24.99 nsec when the optical writing frequency is 60 MHz.

Further, according to the experiment by the applicant, the deviation between adjacent pixels in the image quality in which the fluctuation of the vertical line is allowed is 1.
It has been proved that 2 pixels is the limit value. This time,
The shift of 1.2 pixels is 20 nsec as the sync shift value of the sync signal when the optical writing frequency is 60 MHz.

[0008]

As described above, the pixel density is 1
High pixel density of 200 dpi, optical writing frequency 60 MH
In order to obtain an image quality satisfying the sharpness and the graininess in a high-speed image forming apparatus of z, it is a big problem to reduce the jitter of the sync detection signal.

As a cause of jitter of the synchronizing signal, the incident light is incident on the jitter of the polygon mirror rotating motor which constitutes the rotating polarization means, and the optical sensor which constitutes the synchronization detecting means by the surface tilt of each surface of the polygon mirror. Fluctuation of conditions,
It is known that the light quantity of the laser diode fluctuates.

FIG. 8 shows that the sync detection signal width changes and the sync start position changes due to the change in the photodiode output due to the light intensity. It is known that the greater the light intensity to the photodiode, the greater the sync signal width and the more stable the sync signal. Such contents are disclosed in JP-A-1
Japanese Unexamined Patent Publication No. 0-319331 discloses a technique for controlling the laser beam light intensity for a synchronization signal to be higher than that at the time of lighting for obtaining the first synchronization signal. However, the above publication only specifies that the light intensity for obtaining the synchronization signal is equal to the maximum intensity during normal image formation.

By the way, according to the research conducted by the applicant, in a high-speed image forming apparatus having a high pixel density of 1200 dpi and an optical writing frequency of 60 MHz developed by the applicant, the light intensity for obtaining a synchronizing signal is It became clear that a light intensity higher than the maximum light intensity at the time of normal image generation is required. Light of such intensity is described in the above-mentioned Japanese Patent Laid-Open No. 10-
There is a problem that the content disclosed in Japanese Patent No. 3193331 cannot be obtained.

In view of the above problems, it is a first object of the present invention to provide a multiple beam writing apparatus capable of improving the accuracy of the light intensity of the sync detection signal and preventing the deterioration of the image quality. To do.

A second object of the present invention is to provide an image forming apparatus capable of outputting an image having an image quality excellent in sharpness, gradation and graininess by forming an image using the multi-beam writing apparatus. The purpose of.

[0014]

In order to achieve the first object of the present invention, the invention according to claim 1 simultaneously polarizes and scans a plurality of light emitting sources and a plurality of writing lights from the respective light emitting sources. Synchronous detection signal generation having a rotary polarizer, an optical lens that constitutes a scanning optical system that scans a plurality of writing lights, an optical sensor that generates a synchronization signal that defines the writing start position on the photoconductor surface, and a synchronization detection mirror In the multi-beam writing apparatus provided with the means, a multi-beam writing apparatus that illuminates a plurality of beams when irradiating the optical sensor with a light beam to generate a synchronization signal is the most main feature.

According to a second aspect of the present invention, the light intensities of the light beams simultaneously received by the optical sensor are such that the sum of the light intensities of the light beams of each combination becomes equal in a combination of an arbitrary number of light beams. The main feature of the multi-beam writing apparatus according to claim 1 is that the number of combinations of light beams and the light intensity of each light beam in the combination can be set arbitrarily.

According to a third aspect of the present invention, the light intensity of each light beam in the combination of light beams is made equal.
The multi-beam writing device described is the main feature.

According to a fourth aspect of the present invention, there is provided a multi-beam writing apparatus according to the first aspect, wherein a beam converging member is added on a multi-beam optical path so as to converge the plurality of light beams to an arbitrary light receiving point of the optical sensor. Is the main feature.

A fifth aspect of the present invention is characterized in that the beam converging member is arranged at an intermediate portion of an optical path between the optical sensor and the synchronous detection mirror, and a main feature of the multiple beam writing apparatus is the fourth beam writing apparatus. .

According to a sixth aspect of the present invention, a plurality of light beams simultaneously received by the light sensor are arranged in parallel in a row orthogonal to the beam scanning direction in the light sensor so that an intermediate portion on the optical path of the plurality of light beams. The main feature of the multi-beam writing apparatus according to claim 1 is that a beam direction changing member is added.

The invention according to claim 7 is characterized mainly in the multi-beam writing apparatus according to claim 6, wherein the beam converging member has the beam converging member according to claim 4 also having its function.

In order to achieve the second object of the present invention, the invention according to claim 8 is the most main feature of the image forming apparatus using the multiple beam writing apparatus according to any one of claims 1 to 7. And

The ninth aspect of the invention is characterized mainly in the image forming apparatus according to the eighth aspect, which is provided with an electrophotographic image forming means.

The tenth aspect of the invention is characterized mainly in the image forming apparatus according to the eighth aspect, which is equipped with an image forming means of a digital electrophotographic system.

The invention according to claim 11 has a pixel density of 12
The image forming apparatus according to claim 10, which is 00 dpi, has a main feature.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a multiple beam writing apparatus according to an embodiment of the present invention, and FIG. 2 is a configuration diagram of an optical sensor. The configuration of the multiple beam writing apparatus shown in FIG. 1 will be described together with its operation.

A plurality of laser beams emitted from a plurality of laser light sources 10 are collimated by a condenser lens 11 and only a required beam diameter is taken out by an aperture 12 having a slit portion corresponding to a dot size. The beam is formed into an appropriate beam diameter by the lens 13, and is scanned in the main scanning direction which is the long axis direction of the photoconductor 21 by the polygon mirror 15 which is the rotary scanning means 14.

Arranged on the optical path are fθ lenses 17 and 18, which are an optical system for converting a constant-angle scan into a constant-speed scan, an optical-path changing mirror 19, and a cylinder lens 20 for collecting light in the rotation direction of the photoconductor. Then, the minute laser beam spot is imaged on the surface of the photoconductor (imaging spot array 22). further,
The beam returned by the synchronization detection mirror 23 is applied to the optical sensor 25 via the beam converging member 26,
As a result, a synchronization signal is generated.

As shown in FIG. 2, when the laser (light) beam irradiates the photodiode of the optical sensor 25, a current flows through the photodiode and a voltage is obtained at the end thereof. The comparator compares this voltage with the reference voltage to generate a synchronization signal.

In the image forming apparatus studied by the applicant of the present invention, a combination of a beam spot diameter of 35 μm and a photoconductor film thickness of 30 μm is used, and the light intensity on the photoconductor surface is aimed at an integrated light quantity value of 45 μw. However, when the integrated light amount value (light intensity) on the surface of the photoconductor at the time of image formation is set to 45 μw, the light intensity applied to the optical sensor 25 becomes 120 μw or more in the integrated light amount value, which is stable within 10 μsec of jitter. A sync signal is obtained. In other words, a stable synchronization detection signal can be obtained by increasing the intensity of the irradiation light to the optical sensor 25 for generating the synchronization detection signal, which is higher than the light intensity required for image formation.

That is, when the optical sensor 25 is irradiated with a light beam to generate a synchronization signal, when the light beam passes through the optical sensor 25, a plurality of beams are turned on to stably generate a synchronization detection signal. can do. Eg 1
When a 4-channel laser diode of CH, 2CH, 3CH, and 4CH is used, 1CH and 2CH are combined and light is emitted at the same time to obtain a synchronization signal.
Such combinations include 1CH and 3CH, 1C
H and 4CH, 2CH and 3CH, 2CH and 4CH, 3CH
And 4CH, 1CH and 2CH and 3CH, 1CH and 2CH and 4CH, 1CH and 3CH and 4CH, 2CH and 3CH and 4
Various types such as CH can be considered.

Further, the required light intensity can be realized by combining arbitrary beams among a plurality of beams. 1C
When a laser diode of 4 channels of H, 2CH, 3CH, 4CH is used, a synchronization signal is obtained by combining 1CH and 2CH and emitting light at the same time. Then, the light intensity received by the optical sensor 25 is Ps1CH +
Ps2CH. Similarly, the combination is 1C
H and 3CH, 1CH and 4CH, 2CH and 3CH, 2CH
And 4CH, 3CH and 4CH, 1CH and 2CH and 3CH,
1CH, 2CH and 4CH, 1CH and 3CH and 4CH, 2
Various types such as CH, 3CH, and 4CH can be considered.

Further, by averaging the light emission energy of the light beam when passing through the optical sensor 25, the temperature rise of the light source for emitting light can be approximated, and the light intensity fluctuation for each line can be suppressed. For example, 1CH,
When using a 4-channel laser diode of 2CH, 3CH, 4CH, 1CH, 2CH, 3CH, 4CH
In case of simultaneously emitting light and obtaining a synchronization signal, each 1CH,
Light intensity of 2CH, 3CH, 4CH is Ps1CH, Ps2
When CH, Ps3CH, Ps4CH, optical sensor 25
The light intensity received by Ps1CH + Ps2CH + Ps3C
H + Ps4CH, Ps1CH = Ps2CH = Ps3
By setting CH = Ps4CH, the emission energy can be evenly dispersed in each channel, and the fluctuation of the light intensity due to the temperature rise can be suppressed small.

FIG. 3 is a perspective view of a laser diode as a multiple laser light source. Four lasers arranged vertically are simultaneously irradiated during one scanning to form a beam spot at four lines at a time in the main scanning direction of the photoconductor rotation direction. At this time, when the pitch of each 4 lines is 1200 dpi, the cylinder lens 13 is adjusted to be 21.16 μm.
Adjusted by. Optical sensor 25 for obtaining synchronization detection signal
On the surface, when receiving a plurality of beams, a more stable signal is generated when the light receiving diameter is not diverged and is formed in a single small area. As described above, the beam receiving diameter of the beam is formed in a single small area by adding the beam converging member 26 on the plural beam optical paths. A converging lens or a prism can be used as the beam converging member 26.

FIG. 4 shows a four-channel multiple laser light source 10
The beam converging member 26 by the plurality of beams emitted from the
It is a schematic diagram which forms a laser spot on the optical sensor 25 via. As shown in the figure, the spot of the four-channel light beam is converged by the beam converging member 26. Further, the beam converging member 26 is disposed between the synchronous detection mirror 23 and the optical sensor 25, and is also disposed as close to the optical sensor 25 as possible, which is advantageous when forming a plurality of beams in a single small area. .

In an optical writing device using a plurality of laser light sources 10, when a plurality of beam spots are formed on the photoconductor 21, the light beam should have an arbitrary angle with the perpendicular line to the main scanning direction of the long axis direction of the photoconductor 21. It is generally laid out in. This is mostly due to restrictions from the layout of the image forming apparatus, but even in the image forming apparatus studied by the applicant, the multiple laser light source 10 is
The photoconductor is arranged so as to be inclined by 23 degrees with respect to the rotation direction of the photoconductor and the paper conveyance direction.

FIG. 5 is an explanatory view showing a beam spot aligned with an inclined beam spot. Assuming that the sheet is conveyed above the plural laser light sources, the plural laser light sources 10 are arranged at an arbitrary angle with respect to the sheet conveying direction, and the beam spot formed when the plural beams are simultaneously irradiated is an inclined beam spot 31. Become. In order to form the beam spots 32 vertically aligned in the paper transport direction, the beam irradiation timings for the reference beam among the plurality of beams, such as during the scanning on the photosensitive member surface, may be controlled.

However, as described above, the multiple laser light source 1
Even when 0 is tilted, when a plurality of beams are received on the optical sensor surface, a more stable signal is generated by forming the light receiving diameter in a single small area without diverging. To this end, a plurality of beams are emitted at the same time, and when the plurality of beams are received by the optical sensor 25,
A beam direction changing member is added to an intermediate portion on the optical paths of the plurality of beams so as to be parallel to a column orthogonal to the beam scanning direction.

FIG. 6 is a schematic diagram showing how a plurality of tilted laser light sources 10 irradiate a beam onto an optical sensor via a beam direction changing member. In this example, the synchronization detection mirror 23 is used as a beam direction changing member, and the plurality of beams emitted from the plurality of laser light sources 10 are directed by the beam direction changing member 23 to the light receiving element surface of the optical sensor 25 in a direction orthogonal to the scanning direction. It has been modified to be parallel. The beam direction changing member may be realized by using the beam converging member 26. For example, a prism or the like is used as the beam converging member 26, and the plurality of beams emitted from the prism are light receiving elements of the optical sensor 25. It can be arranged parallel to the plane in a direction orthogonal to the scanning direction.

FIG. 7 is a schematic view of the image forming apparatus according to the embodiment of the present invention. Charging means 4 around the photoconductor 21
1. An optical writing unit (a plurality of beam writing apparatus of the present invention) 42, a developing unit 43, a transfer unit 44, and a cleaning unit 45 are arranged, and when the image forming apparatus control unit (not shown) instructs to start image formation. The photoconductor 21 rotates clockwise, and the optical writing means 42 drives the polygon motor to generate a synchronization signal. The photoconductor 21 is charged by the charging unit 41, a latent image corresponding to the image data input from an external input device (not shown) is formed by the optical writing unit 42, and the visualized image is formed by the image visualization agent by the developing unit 43. To get

The sheet stored in the sheet storage section 46 is fed by the sheet feeding means 47, and is sent out by the registration section 48 at the same timing as the sheet conveyance timing and the writing timing. Then, the visible image by the image visualization agent can be transferred to a predetermined position on the sheet by the transfer means 49. The sheet is conveyed by the conveyor belt 49, the visible image formed by the image visualization agent transferred onto the sheet is fixed by the fixing unit 50, and the input image data is visualized and fixed on the sheet.

By using the optical writing means 42 of the present invention in the image forming apparatus, it becomes possible to accurately generate the synchronization detection signal, prevent deterioration of image quality due to vertical line fluctuations, and sharpness. An image forming apparatus capable of outputting an image with good gradation and graininess can be provided.

A configuration using a conventional electrophotographic process method can be proposed as the image forming apparatus. An OPC film is formed on the photosensitive layer of the photoconductor, and a toner formed of resin is used as an image visualization agent. Even in such a conventional electrophotographic process method, by using the optical writing means 42 of the present invention, it is possible to accurately generate a synchronization detection signal, and prevent deterioration of image quality due to vertical line fluctuations and the like. It is possible to provide an image forming apparatus capable of outputting an image having good sharpness, gradation, and graininess.

Further, even in the image forming apparatus of the laser beam digital electrophotographic system using the laser diode as a plurality of writing lights of the optical writing means 42, by using the optical writing means 42 of the present invention, the synchronization detection signal can be accurately detected. Therefore, it is possible to provide an image forming apparatus capable of generating an image, preventing deterioration of image quality due to vertical line fluctuations, etc., and capable of outputting an image having good sharpness, gradation and graininess.

Furthermore, the digital writing pixel density is 12
In the image forming apparatus having a high pixel density of 00 dpi, by using the optical writing unit 42 of the present invention, it is possible to accurately generate the synchronization detection signal, prevent deterioration of image quality due to vertical line fluctuation, and the like. It is possible to provide an image forming apparatus that can remarkably realize the effect of being able to output an image with good sharpness, gradation, and graininess.

[0045]

According to the first aspect of the present invention, a plurality of light emitting sources, a rotary polarizer that simultaneously polarizes and scans a plurality of writing lights from the respective light emitting sources, and a scanning optical system that scans a plurality of writing lights. In the multi-beam writing apparatus including an optical lens that configures, a photodetector that generates a sync signal that defines a writing start position on the photoconductor surface, and a sync detection signal generation unit that has a sync detection mirror, the optical sensor is By illuminating multiple beams when irradiating a light beam and generating a synchronization signal, it is possible to secure the necessary and sufficient light intensity that the optical sensor receives so as to stably generate the synchronization detection signal. As a result, the accuracy of the synchronization signal is improved and the deterioration of image quality such as vertical line fluctuation can be prevented.

According to the second aspect of the present invention, the light intensity of the light beams simultaneously received by the optical sensor is equal to the sum of the light intensity of the light beams of each combination in an arbitrary number of light beam combinations. The number of light beams combined and the light intensity of each light beam in that combination can be set arbitrarily, so that the optical sensor can receive the sufficient light necessary to stably generate the synchronization detection signal. The strength can be set and secured, the accuracy of the synchronization signal is improved, and the deterioration of image quality such as vertical line fluctuation can be prevented.

According to the third aspect of the present invention, by making the light intensities of the respective light beams in the combination of the light beams equal, the temperature difference between the light emitting sources is eliminated, the thermal crosstalk is reduced, and each synchronous detection is performed. It is possible to stably generate the synchronization detection signal by reducing the fluctuation of the light intensity in the light source, improve the accuracy of the synchronization signal, and prevent the image quality deterioration such as vertical line fluctuation.

According to the fourth aspect of the present invention, a plurality of light beams are converged on arbitrary light receiving points of the optical sensor,
By adding a beam converging member on the multi-beam optical path, multiple beams can be superimposed on the minimum surface, stable light intensity can be obtained, the accuracy of the synchronization signal can be improved, and image deterioration such as vertical line fluctuations can be prevented. Can be prevented.

According to the fifth aspect of the invention, the beam converging member is arranged in the intermediate portion of the optical path between the optical sensor and the synchronous detection mirror, so that the plurality of light beams can be reliably reflected in the optical sensor section. The beam can be focused.

According to the sixth aspect of the invention, on the optical paths of the plurality of light beams, the plurality of light beams simultaneously received by the light sensor are arranged in parallel in a row orthogonal to the beam scanning direction in the light sensor. By adding a beam direction conversion member to the middle part, multiple beams can be received by the optical sensor at the same timing, there is no variation in the incidence of each light beam, the accuracy of the synchronization signal is improved, and image quality such as vertical line fluctuations is improved. Deterioration can be prevented.

According to the invention of claim 7, the beam converging member of the beam converging member of claim 4 also functions as the beam direction changing member, so that a plurality of beams can be easily received by the optical sensor at the same timing. It becomes possible to
There is no variation in the incidence of each light beam, the accuracy of the synchronization signal is improved, and deterioration of image quality such as vertical line fluctuation can be prevented.

According to the eighth aspect of the present invention, by using the multi-beam writing apparatus of the present invention, it is possible to generate an accurate synchronizing signal, eliminate vertical line fluctuations, and improve sharpness, gradation and graininess. An image forming apparatus capable of outputting an image with good image quality can be provided.

According to the ninth aspect of the present invention, even in the image forming apparatus using the conventional electrophotographic system, by using the multi-beam writing apparatus of the present invention, it is possible to generate a highly accurate synchronization signal, and the vertical line It is possible to provide an image forming apparatus capable of outputting an image having high image quality with good sharpness, gradation and graininess without fluctuation.

According to the invention of claim 10, further,
Even in a digital electrophotographic image forming apparatus, by using the multi-beam writing apparatus of the present invention, it is possible to generate an accurate synchronization signal, eliminate vertical line fluctuations, and obtain good image quality with sharpness, gradation, and graininess. It is possible to provide an image forming apparatus capable of outputting the image.

According to the eleventh aspect of the present invention, in the image forming apparatus having a high pixel density in which the digital writing pixel density is 1200 dpi, the multi-beam writing apparatus of the present invention is used to accurately generate the synchronization detection signal. It is possible to provide an image forming apparatus capable of preventing the deterioration of image quality due to vertical line fluctuations and the like, and remarkably embodying the effect of outputting an image with good sharpness, gradation, and graininess. it can.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a multiple beam writing apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an optical sensor.

FIG. 3 is a perspective view of a laser diode as a multiple laser light source.

FIG. 4 is a schematic diagram showing how a laser spot is formed on an optical sensor through a beam converging member by a plurality of beams emitted from a plurality of four-channel laser light sources.

FIG. 5 is an explanatory diagram showing a beam spot aligned with an inclined beam spot.

FIG. 6 is a schematic diagram showing how a plurality of tilted laser light sources irradiate a beam on an optical sensor through a beam direction changing member.

FIG. 7 is a schematic diagram of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 8 is an explanatory diagram of a relationship between light intensity and synchronization signal generation.

[Explanation of symbols]

10 Multiple Laser Light Sources 11 Condensing Lens 12 Aperture 13 Cylinder Lens 14 Rotation Scanning Means 15 Polygon Mirror 17, 18 fθ Lens 19 Optical Path Change Mirror 20 Cylinder Lens 21 Photosensitive Body 22 Imaging Spot Row 23 Synchronous Detection Mirror 25 Optical Sensor 26 Beam Convergence Member 31 Inclined beam spot 32 Aligned beam spot 41 Charging means 42 Optical writing means (multi-beam writing device of the present invention) 43 Developing means 44 Transfer means 45 Cleaning means 46 Paper accommodating section 47 Paper feeding section 48 Register section 49 Conveyor belt 50 Fixing means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/113 H04N 1/04 104A F term (reference) 2C087 AB01 AC08 BA03 BD24 CB20 DA06 2C362 BA56 BA67 BA69 BB30 BB31 BB33 2H045 BA23 BA33 CA89 CA98 CB42 2H076 AB05 AB06 AB08 AB12 AB31 5C072 AA03 BA04 BA15 HA02 HA06 HA08 HA13 HB04 HB13

Claims (11)

[Claims] 1. A plurality of light emitting sources, a rotary polarizer that simultaneously polarizes and scans a plurality of writing lights from each light emitting source, an optical lens that constitutes a scanning optical system that scans a plurality of writing lights, and a photoconductor surface. In a multi-beam writing apparatus provided with a light sensor for generating a sync signal for defining a writing start position to a writing position and a sync detection signal generating means having a sync detection mirror, the light sensor is irradiated with a light beam to generate a sync signal. The multi-beam writing apparatus is characterized in that a plurality of beams are turned on during the operation. 2. The light intensity of the light beams simultaneously received by the optical sensor is set so that the sum of the light intensity of the light beams of each combination becomes equal in an arbitrary number of combinations of the light beams, and 2. The multi-beam writing apparatus according to claim 1, wherein the number of combinations and the light intensity of each light beam in the combination can be arbitrarily set. 3. The multi-beam writing apparatus according to claim 2, wherein the light intensities of the light beams in the combination of the light beams are made equal. 4. The multi-beam writing apparatus according to claim 1, wherein a beam converging member is added on a multi-beam optical path so as to converge the plurality of light beams to an arbitrary light receiving point of the optical sensor. 5. The multi-beam writing apparatus according to claim 4, wherein the beam converging member is arranged in an optical path intermediate portion between the optical sensor and the synchronization detection mirror. 6. A beam direction changing member is provided at an intermediate portion on an optical path of the plurality of light beams so that the plurality of light beams simultaneously received by the light sensor are arranged in parallel in a row orthogonal to a beam scanning direction in the light sensor. The multi-beam writing apparatus according to claim 1, further comprising: 7. The multi-beam writing apparatus according to claim 6, wherein the beam converging member has the beam converging member according to claim 4 also having the function thereof. 8. An image forming apparatus using the multi-beam writing apparatus according to claim 1. Description: 9. The image forming apparatus according to claim 8, further comprising an electrophotographic image forming unit. 10. The image forming apparatus according to claim 8, further comprising a digital electrophotographic image forming unit. 11. The image forming apparatus according to claim 10, wherein the pixel density is 1200 dpi.