JPS62177520A - Optical scanner - Google Patents

Abstract

PURPOSE:To attain polychromatic printing stabilized in printing quality by adjusting distances from the 1st-n-th laser oscillators up to the laser beam incident point of an optical scanner in accordance with optical systems arranged between respective laser oscillator and the optical scanner. CONSTITUTION:The 1st and 2nd laser beams 309, 310 generated from the 1st and 2nd laser oscillators 302, 303 are ideally made parallel beams through respec tive collimeter lenses 304, 305, but the deviation of light emitting points in vertical and horizontal directions generally exists in the semiconductor laser oscillators and the light beams are not made parallel beams at the time of accurate observation. Since the 1st and 2nd laser oscillators 302, 303 are ar ranged so that l2+DELTAl=l1A+l1B is formed, the dispersion of the diameters of the 1st and 2nd laser beams 309, 310 on a photosensitive body can be removed and both the diameters can be equal. When the optical scanner is applied to a polychromatic laser printer, polychromatic printing stabilizing its printing quality can be attained.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention is applicable to, for example, a multicolor laser printer having a plurality of steps of printing by scanning exposure with laser beam light and an electrophotographic process. The present invention relates to an optical scanning device that scans and exposes a photoreceptor using a single optical scanner.

[Technical Background of the Invention and Problems Therewith] Recently, a multicolor laser printer has been considered, which has 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 an optical system for scanning and exposing the photoconductor, that is, the configuration of the optical scanning device.One of the technical challenges is to scan and expose the photoconductor. It is necessary to make all eight diameters of the plurality of laser beams equal.

[Purpose of the Invention] The present invention has been made in view of the above-mentioned circumstances, and its purpose is to make all eight diameters of a plurality of laser beams on a surface to be scanned equal. An object of the present invention is to provide an optical scanning device that, when applied to a printer, enables multicolor printing with stable print quality.

[Main points of the invention] In order to achieve the above object, the present invention provides a light beam that scans a surface to be scanned by receiving laser beam light output from a plurality of laser oscillators with a single optical scanner via an optical system. The scanning device is characterized in that the distance from each of the laser oscillators to the laser beam incident point of the optical scanner is adjusted in accordance with the optical system provided therebetween.

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

FIG. 19 shows, for example, a two-color laser printer 199 to which the optical scanning device according to the present invention is applied, and is connected to a host system such as a computer or a word processor via a cable (not shown), and receives two-color laser printer 199 from the host system. Print the dot image data of each seed 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 and a position sensor 20 are arranged in order along the direction of rotation of the photoreceptor 200.
2. First developing device 203, second charging device 204, second level sensor 205, second developing device 206, pre-transfer charging device 20
7, a transfer charger 208, a peeling charger 209, a cleaner 210, and a static eliminator 211 are provided. In addition,
The first developing device 203 performs first color development using a first color toner (non-magnetic component developer), and the second developing device 206 performs second color development using a second color toner (non-magnetic component developer). 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 photoconductor 200 is charged by the first charger 201, and the electricity is outputted from the rotating mirror scanning unit 212, which will be described in detail later, and is output from the reflecting mirror 31L31.
A first electrostatic latent image is formed by scanning and exposing the photoreceptor 200 with the second laser beam 310 that is reflected and guided by the second laser beam 310 and erasing the charges in the first image information portion. The latent image is developed with a first color toner by a first developing device 203 to form a first color toner image. Next, the second charger 20
4, the photoconductor 200 on which the first color toner image has been formed is recharged, and the toner image is outputted from the rotating mirror scanning unit 212, which will be described in detail later, and reflected by the reflecting mirrors 314, 315.3.
A second 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 second image information portion.
The electrostatic latent image is developed with a second color toner by a second developer 206 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 . Paper feed! Reference numeral 213 denotes a paper feed cassette 214 and 215 that is removable and has two upper and lower stages that stores a plurality of sheets of paper P.
Then, one sheet of paper P is loaded from these paper cassettes 214 and 215.
Paper feed rollers 216 and 217 that take out sheets one by one, a manual paper feed tray 219 attached to the manual paper feed port 218 formed above the upper paper feed cassette 214, and this manual paper feed tray 2
A pair of paper feed rollers 22 that feed paper P supplied from 19
0, and a pair of registration rollers 221 that receive the paper P sent by these paper feed rollers 216, 217, and 220, align the leading edge of the paper, and send out the paper P in synchronization with the image on the photoreceptor 200. It is set up and configured.

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,
The second color toner @) is transferred respectively. 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 there, and the sheet P after fixing is discharged to the paper discharge tray 225 by a pair of paper discharge rows 5224. 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 the 19th factor, the rotating mirror scanning unit 212 scans the first . Reflection mirrors 311, 312, 314 for guiding the second laser beam 309, 310 to a predetermined position,
315° 316.307, by fixing the transmission glass 313.317 for dustproofing the optical system and a beam photodetector (not shown), the laser beam on the photoreceptor 200 due to the error in the optical path length of each laser beam light can be prevented. Differences in light diameter and scanning speed are kept to a minimum, and the mutual adjustment of the laser beams can be easily performed before or after the optical system is installed in the body.

3 to 5 show in detail a rotating mirror scanning unit 212 as an optical scanning device according to the present invention. The rotating mirror scanning unit 212 includes an eight-sided rotating mirror (polygon mirror) 300 and a rotating mirror 300 as main elements.
a motor 329 that rotationally drives the fθ lens 301, a first
．． Second semiconductor laser oscillator (hereinafter simply referred to as laser oscillator) 302, 303, collimator lens 304° 305
, a prism 306 as a reflective member and a casing 3
30, the fθ lens 301 is mounted with a screw on a flange 327 that is screwed to the casing 330. 1st. A first laser oscillator including a second laser oscillator 302, 303 and a collimator lens 304, 305 and equipped with an adjustment mechanism. The second laser units 321 and 322 have a cylindrical prism holder 324 to which the prism 306 is fixed.
A fixing set screw 334.3 is inserted into the holder 325 with a built-in insulating plastic spacer 323.
It is fixed at 35. First and second laser units 32
1.322 is arranged at right angles in horizontal plane space and can be rotatably fixed at any position, and the second laser beam light 309 of the second laser unit 321 is adjusted by the prism 306 and is incident on the rotating mirror 300. Ru. 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 emitters 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 laser beam 309 that is modulated according to the first print data, and the second laser oscillator 303 outputs a second laser beam 309 that is modulated according to the first print data. A second laser beam 310 modulated according to print data is output.

Next, the rotating mirror 300 and the first. Second laser unit 3
The relationship with 21.322 will be explained. The third laser beam 309 output from the second laser unit 321
Prism 3 with anti-reflection coating applied to the entrance surface 306a and the exit surface 306b as shown in FIG.
06, the second laser beam light 310
is adjusted so that it is parallel to the horizontal plane space, and is incident downward from the central axis of the rotating mirror 300, and is directed downward to the fθ lens 3.
After passing through the reflection mirror 31 as shown in FIG.
1.312 and the photoreceptor 20 through the transparent glass 313
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 transmitted to the rotating mirror 3 as shown in FIG.
The light is incident above h2 from the center axis of the laser beam 00, is guided onto the photoreceptor 200 through the reflecting mirrors 314, 315, 316 and the transmitting glass 317 as shown in FIG. 19, and is scanned in the same direction as the first laser beam 309. Expose.

1st. The second laser units 321 and 322 are attached to the holder 325 with 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. There is. and a first degree second laser unit 32 having a first degree second laser oscillator 302 and 303;
1,322 is fixed to the casing 330 via a holder 325 on a plane space whose optical axis is parallel to the base 318 before the laser beam enters the rotating mirror 300. In addition, 1. Second laser unit 321°322
If the optical axis before entering the rotating mirror 300 is placed on a perpendicular plane with respect to the base 318, the protection effect provided by the insulating spacer 323 will be weakened, and furthermore, it will be difficult to handle dustproofing and connectors. become.

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 at the shortest distance, and the reliability is also improved.

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. FIG. 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. 1 is a conceptual diagram showing the positional relationship of the laser beam light incident on the rotating mirror 300, and FIG.
06 is used, and the same figure (b) shows the case where the reflection mirror 35 is used.
5 is used.

In FIG. 1(a), 1. Second laser oscillator 302
．． The first one that occurred from 303. Second laser beam light 309
．． 310 are collimator lenses 304 and 305, respectively.
Ideally, the light passes through the light and becomes parallel light, but semiconductor laser oscillators generally have a deviation (astigmatism) between the light emitting points in the vertical and horizontal directions, so the light does not become parallel light microscopically. Therefore, as shown in FIG. 2, the second laser beam 309 passing through the prism 306 must have a longer incident distance on the rotating mirror 300 by a distance Δ than the second laser beam 310 that does not pass through the prism 306. For example, a difference occurs in the diameter of the laser beam on the actual photoreceptor 200. Therefore, in this embodiment, 122+Δj2−nt
The first and second laser oscillators 302 and 303 are disposed at A+(lt e toner;b).This occurs at this time.As a result, the 1° second laser beam 309. Eliminate variation in diameter of 310,
They can be made equal.

FIG. 1(b) shows a reflection mirror 3 instead of the prism 306.
55, there is no need for the same correction as when using the prism 306. However, as mentioned above, due to the astigmatism difference of the semiconductor laser oscillator, the first. The distance from the second laser emitting device 302, 303 to the reflecting surface of the rotating mirror 300 is arranged so that the relationship Q2'-11A'+11e' approximately holds true. As a result, the first . Second laser beam light 309
．． 310 diameters can each be kept equal.

FIG. 11 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 the holder 3 is
25 can be fixed at any angular position using screws 334 and 335. Therefore, as shown in FIG. 12(a), the laser beam spot 362 on the photoreceptor 200 has an elliptical shape of aXb, but by tilting it by the angle θA as shown in FIG. (1))
As shown in FIG. 2, a spot 362' is formed on the photoreceptor 200 in the direction of a' x b' in the main scanning direction and the sub-scanning direction, 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 oscillator 302 and 303 is caused by the difference in the beam diameter due to the variation in the radiation angle of the second laser oscillator 302 and 303. 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. 13 shows a state in which the 1° second laser beam light 309, 310 after passing through the collimator lenses 304, 305 hits 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 axis coincides with the horizontal direction of the rotating mirror 300, and FIG. This figure shows the state of each beam light spot 363' and 364 when tilted by θ2.
al, bl and (7a2.b2 in a> indicate the respective beam diameters. 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=hi
+h2, and h is expressed by the inequality. Therefore, by substituting equation (2) into equation (1) above, W ) b, oos (45°) + b2oos(
45°)+1, and the third item "+1" at this time takes into consideration the sagging 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 beams1, and generally as shown in FIG. When there are n laser beams, W>[Σbn rm 4.5°]+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, the mechanism around the beam photodetector 308, which generates a horizontal synchronization signal essential for printing control of a laser printer, will be explained. In FIG. 19, a reflecting 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, and the second loser beam 309 is reflected by the reflecting mirror 307. and guided to a beam photodetector 308. Figure 15 shows the beam photodetector 308 when the optical system in Figure 19 is viewed from above.
This is a diagram showing the surrounding area, and FIG. 16 is a detailed diagram of the main part. In FIGS. 15 and 16, 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 leaf spring 340, which is fixed on the base 318 with a screw through a bracket 328. Adjusted to optimally hit. At this time, the mounting angle of the leaf spring 340 and the reflecting mirror 307 is designed such that when the adjustment screw 339 protrudes from the bracket 328 by a distance G, the laser beam light hits the beam photodetector 308. The pressurized structure makes it resistant to vibrations and shocks. In addition, the reflection mirror 307
Reflection mirror 307 and base 3 when adjusted
By setting the angle φ made with 18 to 90° or less than 90°, that is, by arranging the reflective surface in the direction of gravity, the reflective mirror 307 is difficult to attract dirt, dust, and dirt due to the bracket 328 and the angle φ. Therefore, 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 portion 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 light intensity, tilting of the rotating mirror 300, and exposure to shock. 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 carrying out the above-mentioned processing, it is possible to easily and inexpensively produce a high quality printed image.Of course, it is also effective to perform a transmission prevention processing other than black coating, and the spacer 331 The material may be other than methyl methacrylate, for example, a material with high light transmittance such as polycarbonate.

FIG. 18 is a diagram showing how the cover of the optical system and the reflection mirror are attached. In the second laser beam 309, the reflecting mirrors 311 and 312 are connected to a pair of brackets 352.
and a fixing leaf spring 354, and the bracket 352 is fixed on the base 318. The reflecting mirror 312 can be adjusted by three optical path adjusting screws 351.
It is supported at a point to allow adjustment of the optical path. The dustproof transparent glass 313 is fixed to the base 318 by a bracket (not shown). A first cover 319 that covers the first loser beam 309 connects the rotating mirror scanning unit 212 and the reflecting mirror 314 to the first cover 319 . It is fixed to the base 318 while covering the second laser beam 309 and 310 so as not to block it. The space between the fθ lens 301 and the first cover 319 is covered with a sealing material 350 such as maltbrene. Note that the rotating mirror scanning unit 212 is covered by a second cover 367. This results in
When replacing the rotating mirror scanning unit 212, it can be easily replaced by simply opening the second cover 367, regardless of other optical components. On the other hand, also for the second laser beam 310, the reflecting mirror 314 is fixed by a pair of brackets 353, and the brackets 353 are fixed on the base 318. The reflecting mirrors 315 and 316 are fixed by a pair of brackets 348 and a fixing leaf spring 347, and the bracket 348 is fixed below the base 318. The reflecting mirror 316 is supported at three points by three optical path adjustment screws 346, so that the optical path can be adjusted. Transparent glass 31 for dustproofing
7 is fixed to the bracket 348 by a bracket 370. The cover of the second laser beam light 310 is
It is folded back by the reflecting mirror 314 and is covered by a first cover 319 until it crosses the base 318 downward, and then covered by a third cover 320 fixed under the base 318.

A scanning window 357 for guiding the second laser beam 310 onto the photoreceptor 200 is formed in the third cover 320 . Then, the third cover 320 and the bracket 348
and are sealed with a sealing material 349 such as maltbrene.

[Effect of the invention 1] As detailed above, according to the present invention, a single optical scanner receives laser beam light output from a plurality of laser oscillators through an optical system, and scans a surface to be scanned. In the scanning device, the distance from each of the laser oscillators to the laser beam incident point of the optical scanner is adjusted according to the optical system provided therebetween, so that multiple laser beams can be transmitted on the surface to be scanned. It is possible to provide an optical scanning device in which all the diameters can be made equal and, when applied to a multicolor laser printer, for example, it is possible to perform multicolor printing with stable print quality.

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention. Fig. 1 is a conceptual diagram showing the positional relationship of the laser beam light incident on the rotating mirror, Fig. 2 is a diagram explaining correction in the prism, and Fig. 3 is a conceptual diagram showing the positional relationship of the laser beam light incident on the rotating mirror. 4 is a sectional view of the rotating mirror scanning unit as seen from above, FIG. 4 is a partially sectional side view of the rotating mirror scanning unit, and FIG. 5 is a sectional 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. Figures 1 and 12 are diagrams for explaining the operation of correcting the diameter of the laser beam, Figures 13 and 14 are diagrams for explaining the width setting of the rotating mirror,
Figure 5 is a top view of the optical system, Figure 16 is a side view showing the peripheral part of the beam photodetector, Figure 17 is a detailed view of the cylindrical spacer attached to the beam photodetector, and Figure 18 is a diagram of the optical system. The installation of the cover and reflective mirror is shown in the longitudinal side view, which explains the installation condition.
FIG. 19 is a longitudinal sectional front view showing the configuration of a two-color laser printer. 200...photoreceptor surface to be scanned), 212...
...Rotating mirror scanning unit (light scanning device), 300
...Rotating mirror (optical scanner), 301...
... fθ lens, 302.303 ... semiconductor laser oscillator, 304.305 ... collimator lens, 306 ... prism, 309.310 ...
...Laser beam light, 321.322...
・Laser unit, 355... Reflection mirror. Applicant's agent Patent attorney Takehiko Suzue (a) (b)! Figure 1 Figure 10 g Figure 8 Figure 9 Figure 11 (a) (b) Figure 12 (a) (b) Figure 13 Figure 14 (a) (b) Figure 17

Claims (8)

[Claims] (1) first to nth (n is an integer) laser oscillators that each generate a laser beam; laser beam light output from at least the second and subsequent laser oscillators among the first to nth laser oscillators; an optical system that reflects the laser beam light output from the first laser oscillator and the laser beam reflected by the optical system substantially in parallel in the same direction as the laser beam light output from the first laser oscillator; a single optical scanner that receives light on the same surface and scans a surface to be scanned with the laser beam light; from the first to nth laser oscillators to the laser beam incident point of the optical scanner. An optical scanning device characterized in that the distance between is adjusted according to the optical system provided therebetween. (2) The optical scanning device according to claim 1, wherein the optical scanner uses a multifaceted rotating mirror. (3) The optical scanning device according to claim 1, wherein the optical system uses a prism. (4) The distance from the second and subsequent laser oscillators to the laser beam incident point of the optical scanner is set to be smaller than the distance from the first laser oscillator to the laser beam incident point of the optical scanner. If the length of the laser beam incident surface (output surface) is t, the refractive index of the prism is n, and the angle between the laser beam incident on the prism and the optical axis is θ, then t(1-1/n) '×_c_o_sθ/_c_o_sθ'
) However, the optical scanning device according to claim 3, wherein the length is increased by n_s_i_nθ=n'_s_i_nθ'. (5) The optical scanning device according to claim 1, wherein the optical system uses a reflecting mirror. (6) The optical scanning device according to claim 5, wherein distances from the first to nth laser oscillators to the laser beam incident point of the optical scanner are approximately equal. (7) The first to nth laser oscillators are semiconductor laser oscillators.
The optical scanning device described in Section 1. (8) The optical scanner device according to claim 1, wherein the surface to be scanned is a photoreceptor of a multicolor laser printer.