JPS62176366A - Image forming device - Google Patents

Abstract

PURPOSE:To equalize incident diameters of plural laser light beams wit respect to a photosensitive body by approximately equalizing angles made by plural laser light beams and a normal vector at each incident point on the photosensitive body. CONSTITUTION:An optical system fixes a rotating mirror scan unit 212, reflecting mirrors 311, 312, 314, 315, 316 and 317 leading the 1st and 2nd laser light beans 309 and 310 scanned by the scan unit 212 to the prescribed position, and dust-preventing transmissive glasses 313 and 317 on a base 318. The laser light beams 309 and 310 are modulated according to the 1st and 2nd printed data, led to the photosensitive body 200, scan and expose in the axial direction of the photosensitive body 200. The angles -alpha and -beta made by the laser light beams 309 and 310 and the normal vector at points 336 and 337 incident on the photosensitive body 200 are set to attain -alpha -beta.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention 1] The present invention relates to an image forming apparatus suitable for application to a multicolor laser printer that performs a plurality of printing processes using, for example, scanning exposure using laser beam light and an electrophotographic process. Regarding.

[Technical background of the invention and its problems 1 Recently, multicolor laser printers have been considered that perform a plurality of printing steps using, for example, scanning exposure using laser beam light and an electrophotographic process. In this type of multicolor laser printer, it is desired that multicolor printing be performed in one process. To achieve this, it is necessary to devise a configuration of the optical system for scanning and exposing the photoconductor, and one of the technical challenges is to direct each laser beam light output from multiple laser emitters onto the photoconductor. When irradiating the top, each laser beam must have the same thickness.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its object is to provide an image forming apparatus that can make the incident diameters of a plurality of laser beams on a photoreceptor the same. It is in.

[Summary of the Invention] In order to achieve the above object, the present invention is characterized in that the angles between the plurality of laser beams and the normal vector at their respective points of incidence on the photoreceptor are approximately equal.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 does not show a two-color laser printer 199 as an example of an image forming apparatus according to the present invention, and is connected to a host system such as a computer or a word processor via a cable (not shown). Each dot image data is printed in a different color. That is, 200 is a drum-shaped photoreceptor as an image carrier, which is rotated in the direction of the arrow in the figure by a drive source (not shown). Around the photoreceptor 200, a first charger 201, a first charger 202, a first developer 203, a second charger 204, and a second solidity sensor are arranged in order along the rotation direction of the photoreceptor 200. Sensor 205, second developing device 206, pre-transfer charger 207, transfer charger 208, stripping charger 209
, a cleaner 210, and a static eliminator 211 are provided. Note that the first developing device 203 performs the first color development using the first color toner (non-magnetic component developer), and the second developing device 206 performs the second color development using the second color toner (non-magnetic component developer). Development shall be carried out. In this case, the development is performed on the photoreceptor 200 in a single color, and the developer is not applied in an overlapping manner.

First, the rotating photoreceptor 200 is charged by the first charger 201, and is output from the rotating mirror scanning unit 212, which will be described in detail later, and is output from the reflecting mirror 311.3.
A first electrostatic latent image is formed by scanning and exposing the photoconductor 200 with the second laser beam 310 reflected and guided by the second laser beam 310 and erasing the charges in the first image information portion.
The electrostatic latent image is developed with a first color toner by a first developer 203 to form a first color toner image. Next, the second charger 2
Photoreceptor 200 on which a first color toner image is formed by 04
output from rotating mirror scanning unit 212, which will be described in detail later, and reflecting mirrors 314, 315 .
The second laser beam light 310 is reflected at 316 and guided.
A second electrostatic latent image is formed by scanning and exposing the photoreceptor 200 and erasing the charge in the second image information portion, and this second electrostatic latent image is converted into a second color toner by a second developer 206. The toner image is developed to form a second color toner image.

On the other hand, a paper feeding device 213 that supplies paper P to the lower side of the photoreceptor 200 is provided at one side below the photoreceptor 200 . The paper feeding device 213 includes paper feeding cassettes 214 and 215 that are removable and have two upper and lower stages that store a plurality of sheets of paper P.
Then, one sheet of paper P is loaded from these paper feed cassettes 214 and 215.
Paper feed rollers 216 and 217 that take out sheets one by one, and a manual paper feed port formed above the upper paper feed cassette 214.

21 manual paper feed trays 218 attached to the manual paper feed tray 218, a pair of paper feed rollers 220 that feed the paper P supplied from the manual paper feed tray 219, and these paper feed rollers 216, 217, 22.
A pair of registration rollers 221 and the like are provided to receive the paper P fed at zero, align the leading edge of the paper P, and send out the paper P in synchronization with the image on the photoreceptor 200.

The paper P fed by the registration rollers 221 is sent to the transfer charger 208, where it is charged to the photoreceptor 200.
By coming into close contact with the surface of the photoreceptor 200, the two-color toner image (i.e., the first color,
(second color toner image) are respectively transferred. The paper P onto which each toner image has been transferred in this way is electrostatically peeled off from the photoreceptor 200 by the action of the peeling charger 209, and then transferred to the heat roller 22 as a fixing device by the suction conveyance belt 222.
3, the transferred image is heated and fixed by passing through this, and the sheet P after fixing is discharged to a paper discharge tray 225 by a pair of paper discharge rollers 224. On the other hand, the photoreceptor 200 after transfer is removed by a cleaner 210.
After the residual toner on the surface is removed by the static eliminator 21
1, the static electricity is removed and the battery returns to its initial state.

Next, the optical system will be explained in detail. First, as shown in FIG. 2, the rotating mirror scanning unit 212 scans the first . Reflection mirrors 311, 312, 314, 3 for guiding the second laser beam 309, 310 to a predetermined position
15,316°307, Transparent glass 3 for dustproofing optical system
By fixing the 13° 317 and a beam photodetector (not shown), differences in the laser beam diameter and scanning speed on the photoreceptor 200 due to errors in the optical path lengths of the respective laser beams can be minimized. The mutual adjustment of the laser beams can be easily performed before or after the optical system is installed in the body.

3-5 show rotating mirror scanning unit 212 in detail. The rotating mirror scanning unit 212 is
30 rotating mirrors (polygon mirrors) with 8 sides as main elements
0. A motor 329, f that rotationally drives the rotating mirror 300.
θ lens 301, first. Second semiconductor laser oscillator (hereinafter simply referred to as laser oscillator) 302, 303, collimator lenses 304, 305, prism 30 as a reflecting member
6 and a casing 330, the fθ lens 301
is mounted with screws on a flange 327 that is screwed onto the casing 330. First and second laser emitters 3
02, 303 and collimator lenses 304, 305, with an adjustable grip mechanism. Second laser unit 3
21° 322 is fixed to a holder 325 containing a cylindrical prism holder 324 to which the prism 306 is fixed, with fixing set screws 334 and 335 via an insulating plastic spacer 323. 1st. The second laser units 321 and 322 are arranged at right angles in a horizontal plane space and can be rotatably fixed at any position. mirror 300
is incident on the The holder 325 is fitted with a spacer 326 and screwed, and is attached to the casing 330. With the above configuration, the rotating mirror scanning unit 212 also includes adjustment of the optical axis of the laser beam, which contributes to the miniaturization and high precision of the optical system and also reduces assembly man-hours. Become.

In addition, 1. The second laser oscillators 302 and 303 control the first print data and the second print data by control means (not shown), respectively.
The laser oscillator 302 outputs a first loser beam 309 that is modulated according to the first print data, and the second laser oscillator 303 outputs a first loser beam 309 that is modulated according to the first print data. A second laser beam 310 modulated according to the second print data is output.

Next, the rotating mirror 300 and the first. Second laser unit 3
The relationship with 21.322 will be explained. Loser Unit 3
As shown in FIGS. 3 and 4, the first loser beam 309 output from the prism 30 has an anti-reflection coating on its entrance surface 306a and exit surface 306b.
6, the rotating mirror 3 is adjusted to be parallel to the second laser beam 310 in a horizontal space.
h from the central axis of 00! The light is incident vertically, and the fθ lens 30
After passing through the reflection mirror 311 as shown in FIG.
, 312 and the transparent glass 313 to the photoreceptor 20.
0 and scans from left to right in the axial direction of the photoreceptor 200 for exposure. The second laser beam 310 output from the second laser unit 322 is directly incident above h2 from the central axis of the rotating mirror 300 as shown in FIG. 31
6 and a transmitting glass 317 onto the photoreceptor 200, and is scanned and exposed in the same direction as the first laser beam 309.

1st. The second laser units 321 and 322 are attached to the holder 325 at a distance of hl + h2 as shown in FIG. The light passes above the prism 306 and is incident on the rotating mirror 300. At this time, the distance hl + h2 is determined by the laser beam diameter of the parallel light after passing through the collimator lenses 304 and 305, and the prism 306 and prism holder 324 are arranged so as not to hit the second laser beam 310. has been done. and a first degree second laser unit 32 having a first degree second laser emitting device 302 and 303;
No. 1,322 is attached to the casing 33 via the holder 325 so that the optical axis is located between the protrusions substantially horizontal to the base 318 before the laser beam enters the rotating mirror 300.
Fixed to 0. In addition, 1. When the second laser units 321 and 322 are arranged with respect to the base 318 so that the optical axis of the laser beam before entering the rotating mirror 300 is on a perpendicular plane, the second laser units 321 . 322 becomes difficult, the protection effect provided by the insulating spacer 323 is weakened, and furthermore, it becomes difficult to perform dustproofing and connector processing.

In addition, as shown in FIGS. 4 and 5, the optical axis points of the first and second laser units 321 and 322 and the rotating mirror 30
0 so that the line connecting each incident point 368° 369 on the reflective surface of 1.0 is horizontal to the base 318. Second laser units 321 and 322 are arranged. As a result, the first. The second laser units 321 and 322 can input the laser beam light to the rotating mirror 300 most easily and over the shortest distance, and reliability is also improved.

Here, in this embodiment, as shown in FIG. The angles between the second laser beam 309 and 310 and the normal vector at the respective incident points 336 and 337 on the photoreceptor 200 around the rotational direction of the photoreceptor 200 are −α and −
β is set to [−α−−β]. If [1α
1≠Iβ1], then the first . Second laser beam light 30
Even if the eight diameters of 9°310 are the same, the diameter of the beam on each photoreceptor 200 will change, which will affect the image quality. In addition, the first method also applies to changes in optical path length due to distortion of scanning lines. Second laser beam light 309
．． The relative error of 310 is reduced. That is, in this embodiment, [-α--β] is set, but the photoreceptor 200
Due to the arrangement of mechanical parts around [Iαl-1βI]
There is no problem with such an incident angle, that is, either the first or second laser beam light 309 or 310 may be at a (-) angle. In addition, in Figure 1, 3
38 is the center point of the photoreceptor 200.

FIG. 6 is a detailed view of the prism 306 and the prism holder 324, and FIG. 7 shows a cross section taken along the line A--A. The prism 306 is a cylindrical prism holder 324
A plastic spacer 358 and a presser plate are attached to each other by a leaf spring 359 without using screws or the like. The prism holder 324 is inserted into the hole of the holder 325 as shown in FIG. 5 or FIG. 361 rotates the prism holder 324, making it possible to easily and reliably adjust the angle of incidence of the first router beam 309 onto the rotating mirror 300. Figure 9 shows this situation. Note that a reflective mirror or the like may be used in place of the prism 306, and FIG. 10 shows an example thereof, in which a reflective mirror 355 is used in place of the prism 306.

FIG. 11 is a conceptual diagram showing the positional relationship of the laser beam light incident on the rotating mirror 300. FIG. 11(a) shows the case where a prism 306 is used, and FIG.
55 is used. In FIG. 11(a), 1. The first laser beam generated from the second laser generator 302 and 303. The second laser beams 309 and 310 are transmitted through collimator lenses 304 and 304, respectively. ．． 305, ideally becomes parallel light, but semiconductor laser oscillators generally have a deviation (astigmatism) between the light emitting points in the vertical and horizontal directions, so microscopically the light does not become parallel light. .

Therefore, the second laser beam 309 passing through the prism 306 must be incident on the rotating mirror 300 by a distance ΔQ longer than the second laser beam 310 that does not pass through the prism 306, as shown in FIG. , a difference occurs in the diameter of the laser beam on the actual photoreceptor 200. Therefore, in this embodiment, R2+Δρ=λI
1st so that A is 10℃ IB. Second laser oscillator 302
, 303 are arranged. This is the time. As a result, the 1° second laser beam 309 on the photoreceptor 200
．． 310 can be eliminated.

In FIG. 11(b), a reflecting mirror 355 is used instead of the prism 306, so the correction is not 8 concave as when using the prism 306, but as mentioned above, there is an astigmatic difference in the semiconductor laser oscillator. Therefore, 1st. The distance from the second laser generators 302 and 303 to the reflective surface of the rotating mirror 300 is arranged so that the following relationship approximately holds: 12' = (2s A' + (Ax B'). body 20
1st on 0. The diameters of the second laser beams 309 and 310 can be maintained at a predetermined size.

FIG. 13 shows the first (second) laser unit 321 (322).
) as seen from the back, and as mentioned above, the first. The second laser units 321 and 322 are exactly the same, and can be pressed onto the holder 325 via an insulating spacer 323 and fixed at any angular position using screws 334 and 335. Therefore, as shown in FIG.
has an elliptical shape of axb, but by tilting it by an angle θA as shown in FIG.
The beam becomes a spot 362' of 'xb', and a desired beam diameter can be obtained by changing the above-mentioned inclination angle θA.

Therefore, the first. The difference in beam diameter due to variations in the radiation angle of the second laser emitters 302 and 303 is caused by the difference in the beam diameter caused by the first. By changing the angle θA of the second laser units 321 and 322 according to the respective beam diameters, it is possible to perform adjustments such as making the beam diameters the same in the main scanning direction or the sub-scanning direction on the photoreceptor 200. can. In addition, 1
In a laser beam printer, slight variations in beam diameter will result in variations between machines, and as long as the variation in beam diameter is within the design range, it will not be much of a problem for the printer, but as in the present invention, In the case of a multi-beam laser printer with two or more light beams, variations in diameter between the respective beams directly appear as defects in image quality. In addition, the first and second laser units 321 and 322
Because they use exactly the same thing, the equipment is simpler,
It also contributes to reducing the number of parts.

FIG. 15 shows a state in which the 1° second laser beams 309 and 310 after passing through the collimator lenses 304 and 305 are hitting the reflective surface of the rotating mirror 300.

In the same figure (a), each beam light spot 363.36
4 shows the case where the long sleeves coincide with the horizontal direction of the rotating mirror 300, and FIG. The state of each beam light spot 363', 364 when tilted by θ2 is shown, and al, bl and a2. b2 indicates the diameter of each beam. At this time, the rotating mirror 300
The width W of is determined by the diameter of each beam light spot 363 and 364, and in this case h is the width W of the first beam spot 363 and 364 described above. Second
At the pitch of laser beam light 309.310, h=h1
+h2, and h is expressed by the inequality . Therefore, by substituting equation (2) into equation (1) above, ~V > b, Ios(45°) + b2ff19
(45°)+1, and the third item at this time is “+1
'' takes into consideration the droop of both end surfaces 365 and 366 of the rotating mirror 300.

The above shows the width W of the rotating mirror 300 using two light beams in this embodiment, but the same applies to two or more laser beams, and as shown in FIG. When there are laser beams, W>CΣbnoos45°]+1. This makes it possible to obtain the minimum and economical design value for the width W of the rotating mirror 300 for a plurality of laser beams.

Here, 81 structures around the beam photodetector 308 that generate horizontal synchronization signals essential for print control of a laser printer will be explained. In FIG. 2, a mirror 307 is provided at a predetermined location within the scanning range of the first loser beam 309 output from the rotating mirror scanning unit 212. is reflected and guided to beam photodetector 308. Figure 17 shows the beam photodetector 308 when the optical system in Figure 2 is viewed from above.
This is a diagram showing the surrounding area, and FIG. 18 is a detailed diagram of the main part. In FIGS. 17 and 18, the first loose beam 309 output from the rotating mirror scanning unit 212
is reflected by a reflecting mirror 307 and guided to a beam photodetector 308 placed at approximately the same distance as above the photoreceptor 200 . The reflecting mirror 307 is held by a temporary spring 340, and the leaf spring 340 is fixed on the base 318 with a screw through a bracket 328. Adjusted to optimally hit. At that time, the angle at which the leaf spring 340 and the reflecting mirror 307 are attached is determined.
The structure is designed to be able to hit objects, and its pressurization makes it resistant to movement and impact. In addition, by setting the angle φ between the reflecting mirror 307 and the base 318 when the reflecting mirror 307 is in an adjusted state to be less than 90'' or 90°, that is, by arranging the reflecting surface in the direction of gravity, the reflecting mirror The bracket 307 and the angle φ make it difficult for dirt, dust, and dirt to adhere to it, and the laser beam guided to the beam photodetector 308 can be stabilized for a long time.

The beam photodetector 308 uses, for example, a PIN diode, and is mounted on a printed circuit board 342. The printed circuit board 342 is fixed to the bracket 341 via a spacer 343.
A beam photodetector 308 is fixed to. A cylindrical spacer 331 including a cylinder lens part 344 made of methyl methacrylate as shown in FIG. . As a result, the horizontal synchronization signal is stabilized against blurring of the laser beam on the beam photodetector 308, insufficient New Year's Day, tilting of the rotating mirror 300, deflection, and impact. The spacer 331 has a cylinder lens part 344 and a holder part 345 integrated as shown in FIG. It is painted on. This is because when the laser beam light is guided to the beam photodetector 308 by the reflection mirror 307,
The laser beam light has a certain width, and the light that hits the peripheral part other than the cylinder lens part 344 also enters the beam photodetector 308 due to refraction etc., which causes noise in the horizontal synchronization signal and deteriorates the print image quality. This is because it will cause major defects. Therefore, by performing the above-described processing, it is possible to easily and inexpensively produce 1q of high quality printed images. Of course, it is also effective to perform a transmission prevention treatment other than black painting, and the material of the spacer 331 may be a material with high light transmittance such as polycarbonate other than methyl methacrylate.

[Effects of the Invention] As described in detail above, according to the present invention, the angles between the plurality of laser beams and the normal vector at each incident point on the photoreceptor are made approximately equal, so that the plurality of laser beams can be It is possible to provide an image forming apparatus in which the incident diameters of the beams of light on the photoreceptor can be made equal.

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention, and FIG. 1 is a diagram showing the state of incidence of laser beam light onto a photoreceptor, and FIG. 2 is a longitudinal sectional front view showing the configuration of a two-color laser printer. , Figure 3 is a cross-sectional view of the rotating mirror scanning unit seen from above.
FIG. 4 is a partially sectional side view of the rotating mirror scanning unit, and FIG. 5 is a side view of the rotating mirror scanning unit. A partial cross-sectional view of the arrangement of the second laser unit, FIG. 6 is a detailed view of the prism and prism holder, FIG. 7 is a cross-sectional view taken along the line A-A in FIG. 6, and FIG. 9 is a diagram explaining the installation state of the prism and prism holder, FIG. 9 is a diagram explaining the adjustment operation of the prism, FIG. 10 is a detailed diagram of the part when a reflecting mirror is used instead of the prism, and FIG. The figure is a conceptual diagram showing the positional relationship of the laser beam light incident on the rotating mirror, FIG. 12 is a diagram explaining correction in the prism, FIGS. 13 and 14 are diagrams explaining the operation of correcting the diameter of the laser beam light, 15 and 16 are diagrams explaining the width setting of the rotating mirror, FIG. 17 is a top view of the optical system, FIG. 18 is a side view showing the peripheral part of the beam photodetector, and FIG. 19 is a beam light FIG. 3 is a detailed view of the cylindrical spacer attached to the detector. 200...Photoreceptor, 201.204...
・Charger, 203.206...Developer, 212
...Rotating mirror scanning unit, 300...
...Rotating mirror (optical scanner), 301...fθ
Lens, 302, 303... Semiconductor laser oscillator, 304, 305... Collimator lens, 3
06... Prism, 309°310...
- Laser beam light, 321.322... Laser unit l-, 336, 337... Incident point of laser beam light, 355... Reflection mirror. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 5 Figure 10 Figure 6 Figure 7 Figure 8 (a) (b) Figure 12 Figure 13 (a) (b) Figure 14 ( a) (b) Fig. 15 Fig. 16 (a) (b) Fig. 19

Claims (6)

[Claims] (1) At least one optical scanner receives a plurality of laser beams output from a plurality of laser oscillators, and scans and exposes a rotating, pre-charged drum-shaped photoreceptor to a plurality of laser beams on the photoreceptor. In an image forming apparatus that forms a latent image of , and each of the latent images formed on the photoreceptor becomes a visible image, the normal line between the plurality of laser beams and the respective incident points on the photoreceptor is An image forming apparatus characterized in that the angles formed with the vector are approximately equal. (2) The angle between the plurality of laser beams and the normal vector at each point of incidence on the photoreceptor is
The angle around the rotation direction of the photoreceptor is (+), and the opposite direction is (
-), the image forming apparatus according to claim 1, wherein the angle including the sign is approximately equal to the (+) direction. (3) The angle between the plurality of laser beams and the normal vector at each point of incidence on the photoreceptor is
The angle around the rotation direction of the photoreceptor is (+), and the opposite direction is (
-), the image forming apparatus according to claim 1, wherein the angle including the sign is approximately equal to the (-) direction. (4) The angle between the plurality of laser beams and the normal vector at each point of incidence on the photoreceptor is
The angle around the rotation direction of the photoreceptor is (+), and the opposite direction is (
-), the angle including the sign is (+) or (-)
2. The image forming apparatus according to claim 1, wherein the image forming apparatus may be used in either direction, and the absolute values thereof are substantially equal. (5) The image forming apparatus according to claim 1, wherein the optical scanner uses a multifaceted rotating mirror. (6) The image forming apparatus according to claim 1, wherein the laser oscillator is a semiconductor laser oscillator.