JP2003145829A - Multibeam recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a multibeam recorder performing monochromatic recording using a multibeam and color recording using a single beam in order to satisfy both high speed monochromatic recording and high quality color image in which operation of the recorder is sustained upon failure of a laser by performing the recording entirely using a single beam. SOLUTION: A beam detector for detecting synchronization of multibeam detects failure of a light source, and single beam recording mode is selected when a failure is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser printer,
The present invention relates to a multi-beam recording device used in a digital copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, as a recording apparatus of this type, a plurality of beams from a plurality of recording light sources (laser light sources) are used to simultaneously perform recording by optical writing for a plurality of scanning lines to improve the scanning speed. There is known a multi-beam system that aims to achieve this.

As an example of the multi-beam system, there is a system in which a plurality of recording light sources are arranged obliquely with respect to the main scanning direction.

In this case, since each spot by the recording light source has a positional deviation in the main scanning direction, when each recording light source is modulated and driven according to the image information signal, each position in the main scanning direction is changed. It has to be driven at a timing corresponding to the deviation. For this reason, for example, the leading beam of the plurality of recording light sources is used to perform synchronization detection by the beam detector for synchronization, and the clock synchronized with this is used to drive the other recording light sources for modulation. There is.

[0005]

However, in this type of multi-beam recording apparatus, a plurality of beams emitted from a plurality of recording light sources are deflected and scanned in the main scanning direction by a common rotary polygon mirror, and an image is formed. An optical system is used to focus and image as a minute spot on the recording medium. Even if one beam is synchronized, the subsequent beams are not always synchronized due to variations in the surface precision of the rotating polygon mirror. There is no guarantee that it will be obtained, and there will be cases where a dot position shift or the like occurs and a high-quality image cannot be obtained.

Further, due to the relative differences in the emission wavelengths of the plurality of beams emitted from the plurality of recording light sources, the relative differences in the optical path lengths from the respective light sources to the photoconductor, and the like, a scanning magnification shift occurs between the main plurality of beams, In some cases, high-quality images cannot be obtained.

Particularly, in the case of a color image which is required to have a high quality, the dot position deviation and the main scanning magnification deviation as described above cause a color deviation, and therefore it is necessary to suppress it as much as possible.

Therefore, a method is conceivable in which a high-quality color image is recorded by one beam, and a black and white or single-color image in which characters are mainly used and which does not require such high-quality image is recorded by a multi-beam.

In this case, when a color image is recorded, it is better to use a beam emitted from a specific recording light source so that the quality of the recorded image is stable. However, if the light source fails, a black and white or color image is obtained. However, there is also the problem that writing becomes impossible.

The object of the present invention is to enable high-quality image recording,
An object of the present invention is to provide a multi-beam recording apparatus capable of recording an image even if one of a plurality of recording light sources fails.

[0011]

A multi-beam recording apparatus according to the present invention firstly provides a plurality of recording light sources that are independently modulated and driven according to image information, and emits from these recording light sources. A multi-beam recording apparatus in which a plurality of beams are deflected and scanned in the main scanning direction by a common rotating polygonal mirror, and are focused and imaged as fine spots on a recording medium by an imaging optical system to perform recording by optical writing. In the first recording mode in which recording is performed using the plurality of recording light sources on the recording medium that moves in the sub-scanning direction at least at the first speed, and in the sub-scanning direction at the second speed. The recording medium has two modes, that is, a second recording mode in which one of the plurality of recording light sources is selectively used to perform recording on the recording medium. When an abnormality in one Kutomo is detected, characterized in that the recording is performed by the second recording mode.

Secondly, the first recording mode and the second recording mode
In the recording mode, the recording density in the sub-scanning direction is the same.

Thirdly, the beam detecting means used for synchronous detection is used to detect the abnormality of the plurality of recording light sources.

[0014]

(Embodiment) FIG. 11 and FIG. 12 are a block diagram and a diagram showing the structure of a digital color copying machine to which the present invention is applied.

This example has a digital color image reader section in the upper part and a digital color image printer section in the lower part.

In the reader unit, the original 30 is placed on the original table glass 31 and is exposed and scanned by the exposure lamp 32, so that the reflected light image from the original 30 is condensed by the lens 33 on the full color sensor 34, and color images are obtained. Obtain a decomposed image signal. The color separation image signal is passed through an amplification circuit (not shown). It is processed by a video processing unit (not shown) and sent to the printer section.

In the printer section, the photosensitive drum 1 which is an image carrier is rotatably supported in the direction of the arrow, and a pre-exposure lamp 11, a corona charger 2, a laser exposure optical system 3, and a potential sensor 12 are provided around the photosensitive drum 1. , Four developing devices 4y, 4c, 4m, 4Bk of different colors, the on-drum light amount detecting means 13, the transfer device 5, and the cleaning device 6 are arranged.

In the laser exposure optical system 3, the image signal from the reader unit is converted into an optical signal at the laser output unit, the converted laser light is reflected by the rotary polygon mirror (polygon mirror) 3a, and the lens 3b and It is projected onto the surface of the photosensitive drum 1 through the mirror 3c.

When forming an image on the printer section, the photosensitive drum 1
Is rotated in the direction of the arrow, and the photosensitive drum 1 is uniformly charged by the charger 2 after the charge is removed by the pre-exposure lamp 11, and the light image E is irradiated for each separated color to form a latent image.

Next, a predetermined developing device is operated to develop the latent image on the photosensitive drum 1 to form a resin-based toner image on the photosensitive drum 1. The developing device is an eccentric cam 24.
By the operations of y, 24c, 24m, and 24Bk, the photosensitive drum 1 is selectively approached according to each separated color.

Further, the toner image on the photosensitive drum 1 is
The sheet cassette 7 transfers the sheet onto a sheet supplied to a position facing the photosensitive drum 1 via the transport system and the transfer device 5. In this example, the transfer device 5 includes a transfer drum 5a, a transfer charger 5b, and an attraction charger 5 for electrostatically attracting a sheet.
A carrier sheet 5f made of a dielectric material is provided in the peripheral opening area of the transfer drum 5a which has a suction roller 5g, an inner charging device 5d, and an outer charging device 5e facing each other. It is stretched integrally on a cylinder. Carrying sheet 5
For f, a dielectric sheet such as a polycarbonate film is used.

A desired number of color images are transferred to the sheet thus sucked and conveyed to the carrying sheet 5f to form a full-color image.

In the case of forming a full-color image, when the transfer of the four color toner images is completed in this way, the sheet is separated from the transfer drum 5a by the action of the separating claw 8a, the separating push-up roller 8b and the separating charger 5h, and the heat roller. Fixing device 9
The sheet is discharged to the tray 10 via the.

On the other hand, after the transfer, the photosensitive drum 1 is subjected to the image forming process again after the residual toner on the surface is cleaned by the cleaning device 6.

When images are formed on both sides of the sheet,
Immediately after the fixing device 9 is discharged, the transport path switching guide 19 is driven, and after being guided to the reversing path 21a via the transport vertical path 20, the reverse end of the reversing roller 21b causes the trailing end when fed to the beginning. Then, it is withdrawn in the direction opposite to the direction in which it was fed and is stored in the intermediate tray 22. After that, an image is formed on the other surface by the above-described image forming step.

Further, in order to prevent the powder from being scattered on the carrier sheet 5f of the transfer drum 5a, the oil on the sheet, and the like, a backup that faces the brush 14 via the fur brush 14 and the carrier sheet 5f. Cleaning is performed by the action of the brush 15 and the backup brush 17 that faces the roller 16 via the oil removing roller 16 and the carrying sheet 5f. Such cleaning is performed before or after image formation, and at any time when a jam (paper jam) occurs.

Further, in this embodiment, the eccentric cam 25 is operated at a desired timing and the cam follower 5i integrated with the transfer drum 5f is operated to arbitrarily set the gap between the carrying sheet 5a and the photosensitive drum 1. It has a configurable configuration. For example, during standby or when the power is off, the transfer drum and the photosensitive drum are separated from each other.

In FIG. 1, the polygon mirror 3a having eight faces
It shows how the beam laser is deflected.
A and B are beams emitted from the respective light emitting element lasers A and B of the beam laser. Since the arrangements of the laser A and the laser B are different in the main scanning direction, the scannable positions on the photosensitive drum 1 are also different. Therefore, the position on the polygon mirror and the position on the lens used in each optical path corresponding to the same main scanning position are different. Therefore, the beam detector of FIG. 11 synchronizes and writes an image at a predetermined timing. However, if the surface precision of the polygon mirror is not uniform or is deformed by rotation, or if the precision of the lens surface is poor, the dots at the left end are written so that laser A and laser B are written at the same main scanning position. Even if the (spot) positions are aligned, the positions of the other dots are displaced as shown in FIG.

Further, as shown in FIG. 3, since the laser A and the laser B scan on the photosensitive drum 1 at positions displaced by one line in the sub-scanning direction, the curvature of the photosensitive drum 1 and the photosensitive drum 1
The main scanning magnification is different due to the difference in the optical path length due to the influence of the incident angle with respect to or the difference in the wavelength between the laser A and the laser B, and even if the central dot positions are adjusted so that the dot deviation at both ends is minimized, FIG. The images having different widths as shown in are repeated every other line.

Since the positional deviation of these dots and the deviation of the main scanning magnification are minute, they do not pose a problem in a monochrome image.
However, in a color image in which images of four colors overlap, color misregistration occurs. Therefore, in the case of color images, laser A
And use only one of laser B and recording.

FIG. 5 is a flow chart showing the flow of image recording.

First, in step S101, a laser check is performed. As shown in FIG. 10, the polygon mirror is rotated in step S201, the laser A is turned on in step S202, and it is determined in step S203 whether the amount of light detected by the beam detector of FIG. 11 is within a predetermined range. If the detected light amount is within the predetermined range, the process proceeds to step S205, and if not, the step S205.
After the flag indicating the failure of the laser A is set at 204, the process proceeds to step S205. Laser A in step S205
Is turned off, laser B is turned on in step S206, and laser B is turned on in step S207 as in step S203.
The amount of light is detected to make a determination. If the detected light amount is within the predetermined range, the process proceeds to step S209, and if not, the flag indicating the failure of the laser B is set in step S208 and then the process proceeds to step S209. After turning off the laser B in step 209, the polygon mirror is stopped in step S210. Next, in step S211, it is determined whether or not both the laser A and the laser B have a flag indicating a failure. If both are flagged as faulty, the process proceeds to step S212, a display indicating that there is a fault and repair is required is displayed, and then at step S213, the operation of the device is prohibited. If neither the laser A nor the laser B is flagged as a failure, or if only one is flagged, the laser check is ended. Next, in step S102 of FIG. 5, it is determined whether color printing (multicolor printing) or monochrome printing (monochromatic printing). If monochrome printing, proceed to step S103. If color printing is also performed, step S10.
Go to 5. In step S103, it is determined whether one of the lasers has a flag indicating a failure. If the flag is set, the process proceeds to step S105, and if it is not set, the process proceeds to step S104. In step S104, the first recording mode is set, and in step S105
Then, the second recording mode is set. As shown in FIGS. 6 and 7, in the second recording mode, steps S131-
In S133, the recording density in the sub-scanning direction is set to 600 dpi, the moving speed of the photosensitive drum in the sub-scanning direction is set to 117 mm / s, and the rotation speed of the polygon mirror is set to 345.5 s ⁻¹ . Of these, the laser used for recording is selected. Similarly the first
In step S121 to S123, the recording density in the sub-scanning direction is set to 600 dpi, the moving speed of the photosensitive drum in the sub-scanning direction is set to 190 mm / s, and the number of revolutions of the polygon mirror is set to 280.5 s ⁻¹ , but the laser is set to 2 in steps S121 to S123. The laser is not selected because it is used together. Laser selection is performed as shown in FIG.

In step S141, it is determined whether or not a flag indicating a failure of the laser A is set. If it is not set, the laser A is selected in step S142, and if it is set, the laser B is selected in step S143. Next, a series of printing operations shown in steps S106 to S112 of FIG. 5 is performed, and the number of printed sheets is counted up in step S112.

Here, Nc, Nca and Nt, which will be described later, are counters stored in a storage means (not shown), and Nt: total number of printed sheets Nc: number of color printed sheets Nca: number of color printed sheets when laser A is used. .

To count up, as shown in FIG. 9, the total number of printed sheets Nt is incremented by 1 in step S151. Next, in step S152, it is determined whether to perform color printing or monochrome printing. If it is monochrome printing, the count-up is ended, and if it is color printing, the number of color printed sheets Nc is incremented by 1 in step S153. Next, in step S154, it is determined whether or not printing is performed using the laser A. If the laser A is not used, the count-up is ended. If the laser A is used, the number of color prints Nca using the laser A is incremented by 1 in step S155, and the count-up is ended. Next, in step S113 of FIG. 5, it is determined whether printing is completed. If printing has not ended, step S
106 to S112 are repeated to return to step S113,
If the printing is finished, the process is finished.

By setting these two recording modes, high-quality color printing and high-speed black-and-white printing are both possible.
It can be realized with a high definition of 00 dpi. Further, even if one of the laser A and the laser B fails, printing cannot be stopped.

[0037]

As described above, according to the present invention,
First, a plurality of recording light sources that are independently modulated and driven according to image information are provided, and a plurality of beams emitted from these recording light sources are deflected and scanned in the main scanning direction by a common rotating polygon mirror. In a multi-beam recording apparatus in which a focusing optical image is focused on a recording medium by an imaging optical system and recording is performed by optical writing, the recording medium is moved at least at a first speed in the sub-scanning direction. A first recording mode in which recording is performed using all of the plurality of recording light sources, and one of the plurality of recording light sources is provided on the recording medium that moves in the sub-scanning direction at a second speed. There are two modes, a second recording mode in which recording is selectively used, and when an abnormality is detected in at least one of the plurality of recording light sources, the second recording mode is used for recording. Multibeam recording degradation of image quality can be prevented by, and capable image recording even if one of the plurality of recording light source failure by is performed.

Secondly, since the recording densities in the main scanning direction and the sub-scanning direction are the same in the first recording mode and the second recording mode, high definition images are maintained in both modes.

Third, since the beam detecting means used for synchronous detection is used to detect the abnormality of the plurality of recording light sources, it is not necessary to provide a dedicated detecting means for detecting the abnormality.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical path of a two-beam laser in a main scanning direction.

FIG. 2 is a diagram showing dot shift due to a two-beam laser.

FIG. 3 is a diagram showing an optical path of a two-beam laser in a sub scanning direction.

FIG. 4 is a diagram showing a main scanning magnification shift due to a two-beam laser.

FIG. 5 is a flowchart showing a flow of image recording.

FIG. 6 is a flowchart for setting a second recording mode.

FIG. 7 is a flowchart for setting a first recording mode.

FIG. 8 is a flowchart of laser selection.

FIG. 9 is a flowchart of counting up.

FIG. 10 is a flowchart of laser check.

FIG. 11 is a block diagram of a digital color copying machine.

FIG. 12 is a diagram showing the structure of a digital color copying machine.

[Explanation of symbols]

1 photosensitive drum 3 Laser exposure optical system 3a polygon mirror 3b lens 3c mirror Beams and spots emitted from Laser A B Beams and spots emitted from Laser B

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Claims (3)

[Claims] 1. A plurality of recording light sources that are independently modulated and driven according to image information are provided, and a plurality of beams emitted from these recording light sources are deflected and scanned in a main scanning direction by a common rotary polygon mirror. In the multi-beam recording apparatus configured to focus and image as a minute spot on the recording medium by the imaging optical system to perform recording by optical writing, the recording medium moving at least at the first speed in the sub-scanning direction. A first recording mode in which recording is performed using all of the plurality of recording light sources, and one of the plurality of recording light sources on the recording medium that moves in the sub-scanning direction at a second speed. There are two modes, a second recording mode in which recording is selectively performed, and when the abnormality is detected in at least one of the plurality of recording light sources, the second recording mode is used. To A multi-beam recording device characterized by further recording. 2. The multi-beam recording apparatus according to claim 1, wherein the recording density in the sub-scanning direction is the same in the first recording mode and the second recording mode. 3. The multi-beam recording apparatus according to claim 1, wherein a beam detecting means used for synchronous detection is used to detect an abnormality of the plurality of recording light sources.