JPH06164847A - Laser beam scanner - Google Patents

Abstract

PURPOSE:To provide the inexpensive compact laser beam scanner in which a full color picture of high picture quality is formed in a short time through the use of plural laser beams by providing an index sensor to obtain a synchronizing signal of the plural laser beams. CONSTITUTION:An index sensor 30 is made up of a photo sensor base 33, a polarized light filter 32 and a wavelength filter 31. Four photosensors are provided in the photo sensor base 33. When a laser beam L passes through the wavelength filter 31 and the polarized light filter 32, laser beams L1-L4 whose combination in the polarized light direction and the wavelength differs are detected by each photo sensor. A timing when a latent image is overlapped onto the picture is matched by the detection of the laser beams L1-L3 by the 1st-3rd photo sensors. Then the start point of the picture and the latent image is arranged by the detection of the laser beams L2-L4 by the 2nd-4th photo sensors to form the picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam scanning device for scanning a laser beam to form an image, and in particular, an image is formed by sorting the laser beam according to the polarization direction and wavelength of the laser beam. The scanning device.

[0002]

2. Description of the Related Art Image formation by a conventional laser beam is
Especially in image formation in a full-color image forming apparatus,
The latent image formation and development operations by one system of laser beam scanning by one color signal have been obtained by repeating the photoconductor by the number of color signals.

FIG. 4 is a diagram showing the above conventional example.

In FIG. 4, a polygon mirror 13, f which rotates a laser diode (not shown) as a light emitting source is used.
The laser beam L modulated by the color signal for yellow (Y) development through the θ lens 14 and the cylindrical lens 15 has its optical path bent by the mirrors M1, M2 and M3, is scanned, and is charged by the charger 52. Photoconductor drum
A latent image is formed by the rotation of 51 in the direction of the arrow (sub-scanning). Then, the latent image is developed by the yellow (Y) toner developing sleeve 531 of the developing device 53 to form an image of yellow (Y) toner.

The tip of the yellow (Y) toner image reaches the charger 52 again by the rotation of the photosensitive drum 51 and is charged, and by the laser beam L modulated by the color signal for developing the next magenta (M), A latent image is formed so as to overlap with the arrival of the yellow (Y) toner image, and the latent image is developed by a developing sleeve 532 of magenta (M) toner.

By repeating this procedure, latent images of cyan (C) and black (K) are formed and developed. Therefore, when the photosensitive drum 51 rotates four times, yellow (Y), magenta (M) and cyan ( A full-color image with four color toners of C) and black (K) is formed on the photosensitive drum 51. Then, the full-color image formed on the photosensitive drum 51 is transferred and fixed on the recording paper by means not shown to be completed.

As described above, full-color image formation according to the present method involves the operation of latent image formation and development by one-system laser beam scanning by one color signal by rotating the photosensitive member by the number of color signals. It was obtained by repeating.

As another method, a latent image is formed and developed by scanning a laser beam of a first system with one color signal on a photosensitive member moving at a constant speed, and then the next color signal is generated. Latent image formation by scanning of the second system laser beam is performed and developed in accordance with the arrival of the developing unit by the previous color signal, and in the same manner, the third and fourth image signals by the next color signal. This method was obtained by repeating latent image formation and development by scanning with a laser beam of the above system. Therefore, according to this method, a latent image is formed by a laser beam and then developed, so that a full-color image can be formed in a short time because the latent images are successively formed next to each other.

5 and 6 are views showing the above-mentioned conventional example. First, FIG. 5 will be described.

In FIG. 5, in the scanning of the laser beams of the first to fourth systems described above, two-stage overlapping polygon mirrors 131 and 132 are provided, and the laser beams scanned by the polygon mirrors are respectively shown in the figure. As described above, dedicated fθ lenses 141, 142, 143, 144, cylindrical lenses 151, 152, 153, 154, mirrors M11, M12, M13,
A laser beam LY of the first system having a laser diode (not shown), which has M14 and is modulated by each color signal of yellow (Y), magenta (M), cyan (C), and black (K), as an emission light source. , The laser beam LM of the second system, the laser beam LC of the third system, and the laser beam LK of the fourth system are scanned by the polygon mirrors 131 and 132 and moved in the arrow directions. , 524 on the photoconductor belt 511 charged by the latent images PY, PM, P
C and PK are formed.

More specifically, the polygon mirror 132 on the lower side of the rotating polygon mirrors 131, 132 in two layers is first modulated by a color signal for yellow (Y) development. The laser beam LY passes through the fθ lens 141 and the cylindrical lens 151, the optical path is bent by the mirror M11 and scanned, and the latent image PY is formed by the movement (sub-scanning) of the photoconductor belt 511 charged by the charger 521 in the arrow direction. To do. Then, subsequently, the latent image is developed by the yellow (Y) toner developing sleeve 531 to form an image of the yellow (Y) toner. The above is the latent image formation and development by the scanning of the laser beam LY of the first system.

Then, the leading edge of the image of the yellow (Y) toner reaches the next charger 522 by the movement of the photosensitive belt 511 and is charged, and the polygon mirrors 131 and 132 are rotated in two stages.
The laser beam LM of the second system, which is modulated by the color signal for developing the next magenta (M) by the upper polygon mirror 131, passes through the fθ lens 142, the cylindrical lens 152 and the optical path by the mirror M12. The latent image is bent and scanned, and a latent image is formed so as to overlap with the arrival of the image of the yellow (Y) toner, and then the latent image is developed by the developing sleeve 532 of the magenta (M) toner. The above is the latent image formation and development by the scanning of the laser beam LM of the second system.

Thereafter, the cyan (C) and black (K) latent images are formed and developed by scanning the laser beams LC and LK of the third and fourth systems by the same means as described above. ) When the development of the toner by the developing sleeve 534 is completed, a full-color image with four color toners of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the photosensitive belt 511. become. Therefore, a full-color image can be formed in a short time.

Next, FIG. 6 will be described.

In FIG. 6, the laser light sources 111, 112, 113 and 114 of the laser beam emitting section 110 emit laser beams whose wavelengths and polarization directions are different from each other, and the four laser beams are the same as those described above. The laser beams of the four systems are modulated by the color signals of the four kinds of color toners and become the laser beams of the first system to the fourth system as in the case described above. A first imaging optical system 1 that is bundled as a laser beam and is scanned by a polygon mirror through a cylindrical lens.
Is formed.

More specifically, as an example, the laser light source 11
1 is a P-polarized laser beam with a wavelength of 830 nm and is yellow (Y)
The first system laser beam L1 modulated by a color signal for development is emitted.

Similarly, the laser light source 112 has a wavelength of 830n.
The laser beam L2 of the second system, which has been modulated by the magenta (M) color signal with m and S polarization, has a wavelength of 670 nm by the laser light source 113 and the third laser beam L2 with the cyan (C) color signal which is S polarization. Laser beam L3 of the system
Emits a laser beam L4 of a fourth system which is P-polarized and has a wavelength of 670 nm and is modulated by a black (K) color signal.

The first light emitted from the laser light sources 111 and 112,
The laser beams L1 and L2 of the second system are bundled as a laser beam L12 having a wavelength of 830 nm having one P-polarized light and S-polarized light by a polarization beam splitter BS2 that reflects S-polarized light and transmits P-polarized light. Similarly, the laser light source 11
The third and fourth laser beams L3 and L4 emitted from the light sources 3 and 114 reflect the same S-polarized light and transmit the P-polarized light as described above. It is bundled as a laser beam L34 having a wavelength of 670 nm.

The laser beam L12 and the laser beam L34 reflected by the mirror M reflect a laser beam having P polarization and S polarization at a wavelength of 830 nm and a laser beam having P polarization and S polarization at a wavelength of 670 nm. Is bundled as a laser beam L having wavelengths of 830 nm and 670 nm having one P-polarized light and S-polarized light by the transmitting wavelength beam splitter BS1 and is imaged on the mirror surface of the polygon mirror 13 by the cylindrical lens 12. The image optical system 1 is formed.

Then, the rotating polygon mirror 13, fθ
The laser beam L passing through the lens 14 and the cylindrical lens 15 has its optical path bent or transmitted by the wavelength beam splitter BS1, the mirror M, and the polarization beam splitters BS2 and BS3 to form a scanning image, and the photoreceptor belt charged by the charger. On the 511, a second image forming optical system 2 that forms a latent image by moving (sub-scanning) the photosensitive belt 511 in the direction of the arrow is formed.

Further details will be described with reference to FIG. FIG. 2 is a diagram for explaining the situation in which the laser beam is reflected and transmitted by the beam splitter and the mirror depending on the polarization direction of the light and the wavelength of the light. The laser beam L that has passed through the rotating polygon mirror 13, the fθ lens 14, and the cylindrical lens 15 and is bundled into one is reflected by the wavelength beam splitter BS1 and the laser beam L12 having a wavelength of 830 nm having P polarization and S polarization is also reflected. 670nm with P and S polarization
Laser beam L34 having a wavelength of
1 is transmitted.

A laser beam L12 having a wavelength of 830 nm having P-polarization and S-polarization reflected by the wavelength beam splitter BS1 is 830 n P-polarized by the polarization beam splitter BS2.
A laser beam L1 having a wavelength of m is transmitted, and a laser beam L2 having an S polarization of 830 nm is polarized beam splitter BS2.
Is reflected by.

On the other hand, the laser beam L34 having a P-polarized light and S-polarized light having a wavelength of 670 nm transmitted through the wavelength beam splitter BS1 has its optical path bent by the mirror M and the laser beam L3 having a wavelength of 670 nm having S-polarization by the polarization beam splitter BS3. Is reflected, and the P-polarized laser beam L4 having a wavelength of 670 nm is transmitted through the polarization beam splitter BS3.

As described above, the laser beam L1 is the laser beam of the first system which is modulated by the color signal of yellow (Y), and hereinafter, the laser beams L2, L3, L are similarly.
Reference numeral 4 denotes laser beams of the second, third, and fourth systems which are modulated by magenta (M), cyan (C), and black (K) color signals. Therefore, the laser beam L1 of the first system after passing through the polarization beam splitter BS2 scanned by the rotating polygon mirror 13 moves in the arrow direction of the photosensitive belt 511 charged by the charger 521 (sub-scan). To form a latent image PY. Then, subsequently, the latent image is developed by the yellow (Y) toner developing sleeve 531 to form an image of the yellow (Y) toner.

Then, the front end of the image of the yellow (Y) toner reaches the next charger 522 by the movement of the photosensitive belt 511, is charged, and is reflected by the polarization beam splitter BS2 scanned by the rotating polygon mirror 13. Second
The laser beam L2 of the above system overlaps with the arrival of the image of the yellow (Y) toner to form a latent image PM, and then the latent image is developed by the developing sleeve 532 of the magenta (M) toner.

The cyan (C) and black (K) latent images are formed and developed by the third and fourth laser beams L3 and L4 by the same means as described above.

When the development of the black (K) toner by the developing sleeve 534 is completed, a full-color image with four color toners of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the photoreceptor belt 511. As described above, the full-color image can be formed in a short time as in the conventional example described with reference to FIG.

[0028]

As described above with reference to FIG. 4, in the conventional example, the operation of latent image formation and development by one system of laser beam scanning by one color signal is performed to form a full-color image. Since it is obtained by rotating the photoconductor by the number of color signals and repeating the same, it takes four times as long as an image forming time as compared with monocolor.

In the conventional example described in FIG. 5 and FIG. 6 which is an improvement of this, since the latent image forming and developing operations by the laser beams of the first to fourth systems are performed next to each other one after another. As compared with the conventional example described in FIG. 4, the image forming time can be made much shorter.

However, in the case of the conventional example of FIG. 5, since the dedicated optical system is provided for each of the laser beams of the first system to the fourth system as described above, the structure becomes complicated and the number of parts is increased. Also increased, which in turn increased costs. Further, as shown in FIG. 5, since these optical systems are arranged on both sides of the polygon mirror, a laser beam scanning device which requires a large area in terms of space is also provided, and therefore the image forming device is also large. There was also a problem of becoming.

A further improvement of this is the conventional example described with reference to FIG. 6, and as described above, the first to the fourth systems are four types of laser beams in which two types of wavelengths and polarization directions are combined. 4 system laser beams L1, L2, L3,
L4 is bundled as one laser beam L by the first imaging optical system 1.

In order to bundle the laser beams L1, L2, L3 and L4 of the first to fourth systems as one laser beam L, as described above, the polarization beam splitter B is used.
S2, BS3, wavelength beam splitter BS1, mirror M
Are using. And these beam splitters,
Unless the incident angles of the laser beams L1 and L4 and the further bundled laser beams L12 and L34 with respect to the mirror are completely adjusted, the single laser beam L is not completely bundled. Unless this adjustment is incomplete and the laser beam L is not completely bundled, the latent images PY, PM, PC and PK formed in the second image forming optical system are displaced from each other. The image becomes a high quality image and not a high quality image.

However, the adjustment of the laser beam L completely bundled by the above-mentioned incident angle adjustment is very delicate and difficult, and the adjustment is unstable even if it is a little. Therefore, it is very difficult to obtain a high-quality image as an image forming apparatus, and a costly beam splitter is often used in the first imaging optical system. It was a high cost device as well as adjustment costs.

The present invention has been made to solve the above problems. That is, a high-quality full-color image can be formed in a short time by using a plurality of laser beams having different polarization directions, wavelengths, and combinations thereof, and the cost is low.
The object is to provide a compact laser beam scanning device.

[0035]

The object is to connect a first image forming optical system on the front side of the polygon mirror including a cylindrical lens for forming an image of a laser beam on the polygon mirror and a rear side of the polygon mirror. A second image forming optical system including a cylindrical lens for forming an image of the laser beam at an image position, wherein a plurality of laser beams pass through a set of the second image forming optical systems. In the device, in order to obtain the synchronization signals of the plurality of laser beams for image formation, a polarization filter, a wavelength filter, or a polarization filter and a wavelength are provided in front of the plurality of sensors provided in the second imaging optical system. This is achieved by a laser beam scanning device characterized in that both filters of the filters are arranged in an overlapping manner, and the above-mentioned object is to achieve the above-mentioned plurality of laser beams. Polarization direction have, or wavelength, or a combination of the polarization direction and wavelength of that achieved by the laser beam scanning apparatus, wherein different.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to FIGS.

FIG. 1 is a perspective view showing an embodiment of a laser beam scanning device of the present invention.

In FIG. 1, reference numeral 110 denotes a laser beam emitting section which emits four types of laser beams.
It consists of 2, 113 and 114. The laser light source 111 emits a first system laser beam L1 modulated by a color signal for yellow (Y) development with a P-polarized laser beam having a wavelength of 830 nm, for example. Similarly, the laser light source 112 has a wavelength of 830 nm and the laser beam L2 of the second system modulated by the magenta (M) color signal with S polarization.
The laser light source 113 has a wavelength of 670 nm and is S-polarized in cyan (C).
Laser beam L of the third system modulated by the color signal of
3, a laser light source 114 has a wavelength of 670 nm, P-polarized laser beam L4 modulated by a black (K) color signal.
Is emitting.

Then, the laser beams L1, L2, L3,
L4 forms a first imaging optical system 1 in which an image is formed on the mirror surface of the polygon mirror 13 by each cylindrical lens 12 of each laser beam.

Then, the rotating polygon mirror 13, fθ
Each laser beam passing through the lens 14 and the cylindrical lens 15 has its optical path bent by the wavelength beam splitter BS1, the mirror M, and the polarization beam splitters BS2 and BS3, or is transmitted and imaged for scanning to form a photosensitive belt. On the 511, a second image forming optical system 2 that forms a latent image by moving (sub-scanning) the photosensitive belt 511 in the direction of the arrow is formed.

Further, the laser beams L1, L2, L3, L
4, outside the scanning area for image formation in the second imaging optical system 2, in the present embodiment, in the region on the left side of the second imaging optical system 2, the passing laser beams L1, L2, L3. , L4 and an index sensor 30 for obtaining a synchronization signal of the laser beam for image formation.

The index sensor 30 is a photo sensor substrate
A polarization filter 32 is arranged in front of 33, and a wavelength filter 31 is arranged in front of it.

Next, description will be made also with reference to FIG.

FIG. 3 is an enlarged view of the index sensor 30 for easy description.

In FIG. 3, 33 is a photo sensor substrate,
As shown in the figure, four photo sensors PS1 and PS
2, PS3, PS4 are provided. Then, on the front side of the photosensor substrate 33, a polarizing filter 321 that allows the laser beam having the P polarization in the left half to pass therethrough but does not pass the laser beam having the S polarization, and a laser beam having the S polarization in the right half passes through. A polarization filter 32 made of a polarization filter 322 that does not pass a laser beam having P polarization is disposed.

Further, on the front side of the polarization filter 32,
A wavelength filter 311 whose both ends pass a laser beam having a wavelength of 830 nm but does not pass a laser beam having a wavelength of 670 nm, and a laser beam whose central part passes a laser beam having a wavelength of 670 nm but has a wavelength of 830 nm A wavelength filter 31 made of a wavelength filter 312 that does not pass is disposed.

Then, the laser beams L1, L2, L3,
Outside the scanning area for forming an image in the second image forming optical system 2 of L4, in the present embodiment, in the area on the left side of the second image forming optical system 2, the fθ lens 14 and the cylindrical lens 15 are passed. The laser beam L is reflected by the mirror MI and the optical path is bent in the direction of the index sensor 30.

Then, the laser beam L passes through the wavelength filter 31 and the polarization filter 32 described above, so that the wavelength 830n
The m- and P-polarized laser beam L1 is detected by the photosensor PS1. Similarly, the S-polarized laser beam L2 having a wavelength of 830 nm is detected by the photosensor PS2 at a wavelength of 670 nm and S
The polarized laser beam L3 is detected by the photo sensor PS3.
The P-polarized laser beam L4 having a wavelength of 670 nm is detected by the photosensor PS4.

As a means for detecting a laser beam in which various wavelengths and polarizations are combined, a member having both functions of a wavelength filter and a polarization filter is provided in front of the photo sensor or integrated with the photo sensor. The same effect can be obtained with this.

Next, a more detailed description will be given with reference to FIG. Figure 2
FIG. 4 is a diagram for easily understanding the situation where the laser beam is reflected and transmitted by the beam splitter and the mirror depending on the polarization direction of the light and the wavelength of the light as described above. The laser beams having passed through the rotating polygon mirror 13, the fθ lens 14, and the cylindrical lens 15 are reflected by the wavelength beam splitter BS1 into laser beams L1 and L2 having a wavelength of 830 nm having P-polarized light and S-polarized light. The polarized laser beams L3 and L4 having a wavelength of 670 nm pass through the wavelength beam splitter BS1.

The P-polarized and S-polarized laser beams L1 and L2 having a P-polarization and S-polarization reflected by the wavelength beam splitter BS1 pass through the polarization beam splitter BS2 and the S-polarized laser beam L1 having a P-polarization wavelength of 830 nm passes therethrough. In 8
The laser beam L2 having a wavelength of 30 nm is reflected by the polarization beam splitter BS2.

On the other hand, the laser beams L3 and L4 having P-polarization and S-polarization having a wavelength of 670 nm transmitted through the wavelength beam splitter BS1 have their optical paths bent by the mirror M, and the laser beam having a wavelength of 670 nm having S-polarization by the polarization beam splitter BS3. The beam L3 is reflected, and the P-polarized laser beam L4 having a wavelength of 670 nm passes through the polarization beam splitter BS3.

As described above, the laser beam L1 is the laser beam of the first system which is modulated by the color signal of yellow (Y), and the laser beams L2, L3, and L are the same.
Reference numeral 4 denotes laser beams of the second, third, and fourth systems which are modulated by magenta (M), cyan (C), and black (K) color signals. Therefore, the laser beam L1 of the first system after passing through the polarization beam splitter BS2 scanned by the rotating polygon mirror 13 moves in the arrow direction of the photosensitive belt 511 charged by the charger 521 (sub-scan). Although the latent image PY is formed by the laser beam L1, the photosensor PS1 of the index sensor 30 described above immediately before the start of formation of the latent image PY by the laser beam L1.
After a predetermined time from the detection of, the latent image PY is started to be formed on the photosensitive belt 511. The latent image PY is subsequently developed by a yellow (Y) toner developing sleeve 531 to form a yellow (Y) toner image.

The timing at which the latent image is formed by superimposing on the yellow (Y) toner image by the next laser beam L2 is exactly the predetermined time after the detection of the laser beam L1 by the photosensor PS1. A latent image is formed by a magenta (M) color signal by the laser beam L2 at the same timing so that the images can be superimposed. Then, as in the case of the laser beam L1,
Immediately before the start of formation of the latent image PM, the above-mentioned index sensor 30
The photosensor PS2 detects the laser beam L2, and after a predetermined time, the cue is aligned with the yellow (Y) toner image and the formation of the latent image PM is started. Then, subsequently, the latent image is developed by the developing sleeve 532 of magenta (M) toner.

Similarly, the laser beams L2 from the photosensors PS2 and PS3 of the index sensor 30 are
The detection of L3 adjusts the timing of superimposing the latent image on the image, and the photo sensor P of the index sensor 30.
By detecting the laser beams L3 and L4 by S3 and PS4, the image and the latent image are aligned with each other to form an image, and a developing sleeve of cyan (C) toner and black (K) toner
Development by 533 and 534 is performed.

The developing sleeve 53 for the black (K) toner
When the development by 4 is completed, a full-color image with four color toners of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the photoconductor belt 511, and accordingly, a full-color image is formed. Images can also be formed in a short time.

As described above, in the laser beam scanning device of the present invention, the laser beam is composed of a plurality of laser beams having different polarization directions, wavelengths, or combinations of polarization directions and wavelengths of the laser beams.

Then, the laser beam is detected by the index sensor for each polarization direction, wavelength, or combination of polarization direction and wavelength of the individual laser beams so that the overlay timing of images and the cue position are not shifted. This makes it possible to easily form high-quality images. In addition, since the index sensor can detect each laser beam individually, only one set of the second imaging optical system is required, which is very effective for downsizing the device and reducing the cost by reducing the number of parts. It came to work.

[0059]

According to the present invention, it is possible to stably form a high-quality full-color image in a short time by using a plurality of laser beams having different polarization directions, wavelengths, and combinations thereof. A compact laser beam scanning device having a small number of points and a low cost has been provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a laser beam scanning device according to the present invention.

FIG. 2 is a diagram for explaining a situation where a laser beam is reflected and transmitted by a beam splitter and a mirror depending on the polarization direction and wavelength of light.

FIG. 3 is a diagram illustrating an index sensor.

FIG. 4 is a side view of a conventional laser beam scanning device.

FIG. 5 is a perspective view of another conventional laser beam scanning device.

FIG. 6 is a perspective view of another conventional laser beam scanning device.

[Explanation of symbols]

 1 First imaging optical system 110 Laser beam emitting section 111, 112, 113, 114 Laser light source 12, 15 Cylindrical lens 13 Polygon mirror 14 fθ lens 2 Second imaging optical system 30 Index sensor 31 Wavelength filter 32 Polarization filter 511 Photoconductor belt 521, 522, 523, 524 Charger 531, 532, 533, 534 Development sleeve L, L1, L2, L3, L4 Laser beam BS1, BS2, BS3 Beam splitter M Mirror PS1, PS2, PS3, PS4 Photo Sensor

Claims (2)

[Claims] 1. A first imaging optical system on the front side of the polygon mirror including a cylindrical lens for forming an image of the laser beam on the polygon mirror, and the laser beam on an imaging position on the rear side of the polygon mirror. A second imaging optical system including a cylindrical lens for forming an image,
In a laser beam scanning device in which a plurality of laser beams pass through a set of the second imaging optical system, in order to obtain a synchronization signal of the plurality of laser beams for image formation, A laser beam scanning device characterized in that a polarizing filter, a wavelength filter, or both a polarizing filter and a wavelength filter are arranged in an overlapping manner in front of a plurality of sensors provided in an imaging optical system. 2. The laser beam scanning device according to claim 1, wherein the plurality of laser beams have different polarization directions, wavelengths, or combinations of polarization directions and wavelengths.