JPH0359613A - Laser beam scanning device of electrophotography device - Google Patents

Abstract

PURPOSE:To eliminate the need to provide light sources individually to read a document and from an electrostatic latent image by splitting the laser beam from a laser light source by using a beam splitter, and using the two laser beams to read the document and form the electrostatic latent image. CONSTITUTION:The beam splitter 23 splits the laser beam outputted by the laser light source 21 into the two laser beams. Then, the two laser beams are made incident on one polygon mirror 25, one of the two laser beams which are reflected by the polygon mirror 25, i.e. R is used to scan the document, and the reflected light from the document 28 is guided to a photoelectric conversion element to read the document. A photosensitive body 26 is scanned with the other laser beam W according to read information on the document and the electrostatic latent image is formed on the photosensitive body. Consequently, two individual light sources are not required to read the document 28 and form the electrostatic latent image.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applied to factor ξ or digital copiers that can use plain paper, and by dividing a laser beam and making it incident on one polygon mirror. The present invention relates to a laser beam scanning device for an electrophotographic apparatus that reads a document and forms an electrostatic latent image on a photoreceptor.

[Conventional technology]

For example, as shown in FIG. 3, a conventional electrophotographic apparatus includes a reading means 15 for reading and scanning a document, and an electrostatic latent image forming means 16 for forming an electrostatic latent image on a photosensitive drum 11. It is equipped.

The reading means 15 includes a lamp light source 1 and a mirror group 2.
~4, lens 5, and line image sensor CCD (
A charge coupled device (hereinafter referred to as a CCD) 6 and conveying devices 12a to 12'' each including a group of conveying rollers are provided.

On the other hand, an electrostatic latent image forming means 16 for forming an electrostatic latent image on the photoreceptor drum 11 includes a laser unit 7, a polygon mirror 8, a reflecting mirror 10, a photoreceptor drum 11, etc. There is.

When reading a document, the document 13 is illuminated by the lamp light source 1 . The reflected light from the original 13 forms a band-shaped image on the CCD 6 via the mirror groups 2 to 4 and the lens 5. C
The CD 6 performs photoelectric conversion from one end of the pixel to the other end at once. Therefore, the electric signal output from the CCD '6 is an electric signal proportional to the darkness from one end of the document 13 to the other end. This means that one line of the original has been scanned. Electric signals from the CCD 6 are output to an image processing circuit (not shown). When the above scanning is completed, the original 13 is moved by one line scanning by the conveying devices 12a to 2f. By repeating these operations, all the characters, figures, etc. on the document 13 are photoelectrically converted and input to the image processing circuit.

The signal processed by the image processing circuit is input to a control means for a laser light source (not shown). The laser light source constituting the laser unit 7 emits a laser beam without being controlled by a signal from an image processing circuit. This laser beam is modulated into a recording image signal and is incident on a polygon mirror 8 that rotates at high speed. The reflected light from the polygon mirror 8 is further reflected at the anti-li boundary lo, and scans from one end of the photoreceptor drum 11 to the other end, thereby forming a linear electrostatic latent image on the surface of the photoreceptor drum 11. is formed. In this way, when the formation of the electrostatic latent image of the L line is completed, the photoreceptor drum 11 rotates.
Next, an electrostatic latent image is formed by line scanning. By repeating these operations, an electrostatic latent image is formed on the surface of the photoreceptor drum 11, the size of which corresponds to the document valve.

[Problem to be solved by the invention]

However, in the above conventional structure, the document reading means 1
5, many optical system components such as a lamp light source 1, mirror groups 2 to 4, and a lens 5 are required. Especially with digital copiers and fax machines that can use plain paper.
Since high-density reading of 400 dpi (datρer 1 nch) is required, an expensive high-density CCD and high-precision optical system components are required. Therefore, there are problems in that manufacturing costs are high, adjustment of optical system components is complicated, and high assembly accuracy is required.

[Means to solve the problem]

A laser beam scanning device for an electrophotographic apparatus according to the present invention includes:
In order to solve the above problems, in an electrophotographic device that scans a laser beam to generate an electrostatic latent image on a photoreceptor, the laser beam output from the laser light source is split into two laser beams by a beam splitter. Then, the above two laser beams are made incident on one polygon mirror, and one of the two laser beams reflected by the above polygon mirror scans the original, and the reflection from the original is detected. The original is read by guiding light to the photoelectric conversion element, while another laser beam scans the photoreceptor to form an electrostatic latent image on the photoreceptor based on the information read from the original. It is characterized by being configured as follows.

[For production]

According to the above configuration, the laser beam from the laser light source is split into two using a beam splinter, and the two laser beams are used for reading the original and forming an electrostatic latent image. There is no need to provide separate light sources for forming the electrostatic latent image. Furthermore, the laser beam used for reading the document and forming the electrostatic latent image is
Since the light is incident on the - polygon mirror, good synchronization is inevitably obtained between scanning for reading the document and scanning for forming the electrostatic latent image. When reading a document, the document is scanned with a laser beam that acts as a point light source, so that it can be read with high precision using an inexpensive photoelectric conversion element such as a pin photodiode.

Furthermore, expensive high-density CC as a means of reading manuscripts
Since D and various high-precision optical system parts are not required, manufacturing costs can be reduced and there is no need to worry about adjusting or assembling optical system parts.

[Example] An example of the present invention will be described below based on FIGS. 1 and 2.

As shown in FIG. 2, the electrophotographic apparatus according to the present invention includes a laser beam scanning device 40 and a recording means 41 that performs recording based on an electrostatic latent image on the photosensitive drum 26.

In the laser beam scanning device 40, a reflecting mirror 31 is disposed on the optical axis of the laser beam R emitted to the left side of the polygon mirror 25 in order to read a document.
The original 28 is placed on the optical axis of the laser beam R reflected by the laser beam R, and the optical axis of the laser beam W emitted to the right side of the polygon mirror 25 is placed on the right side of the polygon mirror 25 to form an electrostatic latent image on the photoreceptor drum 26. Hannen 1 Kagami 30 is placed above. Further, a photosensitive drum 26 is disposed on the optical axis of the laser beams I and W reflected by the reflecting mirror 30.

As shown in FIG. 1, the laser beam scanning device 40 includes:
It has a laser light source 21, and on the optical axis of the laser beam emitted from the laser light source 21, a laser beam R incident on the paper surface of the original 2 and a laser beam W incident on the photoreceptor drum 26 are aligned. A lens 22 is arranged so as to form a minute focus on the surface. A semiconductor laser diode is used as the laser light source 21, and since a constant amount of light is required to read the original on two days, a constant amount of light is always output.

On the optical axis of the laser beam emitted through the lens 22, there are a laser beam R that travels straight to the left, and a laser beam W that travels straight after passing through the beam splitter 23.
Beam splinter 23 for splitting the laser beam into two
are arranged. An optical modulator 24 is arranged on the optical axis of the laser beam W to change the strength of the laser beam W passing through the interior according to an electric signal applied from the outside.

On the optical axis of the laser beam R reflected by the reflecting mirror 27 and on the optical axis of the laser beam W passing through the optical modulator 24, there is 1.
Two polygon mirrors 25 are arranged. An original 28 is placed on the optical axis of the laser beam R reflected by the polygon mirror 25, and the laser beam R, which is the return light reflected from the original 28, reaches the polygon mirror 25. The polygon roller 25 has a polyhedral shape and is configured to be rotatable. Therefore, the laser beam R incident from a certain direction is transmitted to the rotating polygon mirror 25.
The direction of reflection changes as the surface angle changes. Using this phenomenon, the original 28 is linearly scanned. That is, by rotating the polygon mirror 25, the laser beam R scans the range shown by the broken line in a plane parallel to the plane of the paper.

On the optical axis of the returning laser beam R reflected by the polygon mirror 25, there is a photoelectric conversion element 29 that converts the incident light into an output voltage or an output current depending on the intensity of the incident light.
are arranged. On the optical axis of this returned light, there is a reflecting mirror 27.
However, since a small one is used that does not affect the optical image of the laser beam R of the returned light, the photoelectric conversion element 2
It does not adversely affect the incidence of the returning light into the input terminal 9.

On the other hand, a photosensitive drum 26 is arranged on the optical axis of the laser beam W reflected by the polygon mirror 25.

The laser beam W has its reflection direction changed by the polygon mirror 25 when it is incident from a certain direction, and linearly scans the photoreceptor drum 26 . That is, the laser beam W
scans within a plane parallel to the plane of the paper and within the range indicated by the broken line. The surface of the photoreceptor drum 26 is charged when an electrostatic latent image is formed, and when exposed to light, the resistance value of that portion decreases and is exposed. Therefore, if the light projected onto the photoreceptor drum 26 is made into an image, the photoreceptor drum 26
An electrostatic latent image will be formed on the surface.

On the other hand, the recording means 41 includes a paper cassette 33 containing recording paper, a pickup roller 34 for pulling out the recording paper from the paper cassette 33, and a transport roller for transporting the recording paper to the photosensitive drum 26. A group of transport devices 42a to 42d are provided. Also,
The recording means 41 includes a main charger 51, a developing device (not shown), a transfer charger 52, a cleaning device 53, and a static elimination lamp 50 around the photosensitive drum 26.
are provided. Furthermore, the recording means 41 includes a separation roller 35 for peeling off the recording paper circumferentially contacting the photosensitive drum 26, and a fuser roller 36 for fixing the toner image transferred onto the recording paper. A stacker 54 is provided for discharge processing.

In the above configuration, when reading the original 28,
Laser beam R split by beam splitter 23
is reflected by the reflecting mirror 27 and enters the polygon mirror 25. Laser beam R reflected by polygon mirror 25
is guided to the original 28 and irradiated onto the surface of the original 28. The laser beam R linearly scans the document 28 from one end to the other end as the polygon rotates. The laser beam R, which is the return light reflected from the original 28, is modulated in intensity depending on the shading of the characters and figures, and then enters the polygon mirror 25 again. The laser beam R of the returned light is
The light is reflected by the polygon mirror 25, enters the photoelectric conversion element 29, and is converted into an electrical signal. This electrical signal is input to an image processing circuit (not shown). In this manner, lines are read on the second day of the document.

As described above, when the laser beam R finishes reading one scan on the paper surface of the original 28, the original 28 is moved by the amount of linear scanning in the direction S perpendicular to this linear scanning by the operation of the transport devices 32a to 32f. . Then, the laser beam R linearly scans the surface of the original 28 in the same manner as described above. By repeating such operations, it is possible to scan the entire surface of the document for two days. In this way, the document can be scanned using the laser beam R, which can be treated as a point light source, so it can be read with high precision using an inexpensive pin photodiode without using a high-precision CCD. becomes possible.

On the other hand, when recording, the residual charge on the photoreceptor drum 26 is first removed by the static eliminating lamp 50, and the main charger 51 uniformly charges the photoreceptor drum 26. A latent image is formed.

The laser beam W is transmitted from an image processing circuit (not shown) to an optical modulator 2, where an image signal for recording based on the reading information of the original is sent to the optical modulator 2.
4, and the intensity of the light is modulated when it passes through the optical modulator 24. This modulated laser beam W is
It is reflected by the polygon mirror 25 and the photosensitive drum 2
incident on the surface of 6. As the polygon mirror 25 rotates, the laser beam W scans the photosensitive drum 26 from one end to the other end in a straight line. As a result, the photoreceptor drum 2
6, an electrostatic latent image of the line is formed. At the same time, the photoreceptor drum 26 rotates in the rotation direction N around the shaft 26a, so that the laser beam W scans the entire surface in a straight line, and an electrostatic latent image on the surface is formed on the photoreceptor drum 26. will be formed.

Next, toner inside a developing box (not shown) adheres to the electrostatic latent image formed on the photoreceptor drum 26, and the electrostatic latent image is developed. On the other hand, the recording paper is pulled out from the paper cassette 33 by a pickup roller 34, and is transported to the photosensitive drum 26 by transport devices 42a to 42d. This recording paper is placed in circumferential contact with the surface of the photoreceptor drum 26, and while it moves in synchronization with the rotation of the photoreceptor drum 26, the image on the photoreceptor drum 26 is transferred onto the surface of the recording paper by the transfer charger 52. Ru. Thereafter, the recording paper is separated from the photoreceptor drum 26 by the separation roller 35, while the residual toner on the photoreceptor drum 26 is removed by the cleaning device 53, and the charge is removed by the charge removal lamp 50. The recording paper peeled off from the photoconductor drum 26 passes through the fuser roller 36 of the fixing device, while the toner image is thermally fixed onto the recording paper and recorded as images such as characters and graphics. is discharged to a stacker 54. The moving path of such a series of recording sheets is indicated by an arrow 39.

As described above, this laser beam scanning device uses a single polygon mirror 25 for scanning the laser beam for both reading and recording the original, so it is possible to scan the laser beam using one polygon mirror 25. is no longer necessary.

(Effects of the Invention) As described above, the laser beam scanning type electrophotographic apparatus of the present invention is an electrophotographic apparatus that scans a laser beam to form an electrostatic latent image on a photoreceptor. The beam is split into two laser beams by a beam splitter, the two laser beams are made incident on one polygon mirror, and one of the two laser beams reflected by the polygon mirror is split into two laser beams. The beam scans the original, and the reflected light from the original is guided to a photoelectric conversion element to read the original. Based on the reading information of the original, another laser beam scans the photoreceptor. This configuration is characterized in that it is configured to form an electrostatic latent image on the photoreceptor.

Therefore, by splitting the laser beam emitted from one laser light source using a beam splitter, two separate light sources are not required for reading the document and forming an electrostatic latent image on the photoreceptor. By using one polygon mirror, reading the original and forming an electrostatic latent image on the photoreceptor are performed in synchronization with the scanning of the original and the scanning that forms the electrostatic latent image on the photoreceptor. I can do it. Since the document can be scanned using a laser beam that can be treated as a point light source, it is possible to read the document with high precision with a simple configuration. The laser beam scanning configuration allows many parts to be shared between reading the document and scanning to form an electrostatic latent image on the photoreceptor, simplifying the component configuration, reducing manufacturing costs, and making it easier to assemble and adjust optical system components. This has the effect that you no longer have to worry about it.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention. FIG. 1 is an explanatory diagram showing a laser beam scanning device. FIG. 2 is a block diagram schematically showing an electrophotographic apparatus incorporating the laser beam scanning device of the present invention. FIG. 3 is a schematic configuration diagram of an electrophotographic apparatus incorporating a conventional laser beam scan. 21 is a laser light source, 22 is a lens, 23 is a beam splitter, 24 is a light modulator, 25 is a polygon mirror, 26 is a photosensitive drum, 27 is a reflecting mirror, 28 is a document, and 29 is a photoelectric conversion element.

Claims (1)

[Claims] 1. In an electrophotographic device that scans a laser beam to form an electrostatic latent image on a photoreceptor, a laser beam output from a laser light source is split into two laser beams by a beam splitter. , the above two laser beams are made incident on one polygon mirror, and one of the two laser beams reflected by the above polygon mirror scans the document, and the reflected light from the document is The document is read by guiding it to the photoelectric conversion element, and based on the document reading information,
A laser beam scanning device for an electrophotographic apparatus, characterized in that it is configured to scan a photoreceptor with another laser beam to form an electrostatic latent image on the photoreceptor.