JP4938375B2 - Optical scanning device and image forming device - Google Patents

Description

  The present invention relates to an optical scanning device for forming a latent image on an image carrier, a copying machine having the optical scanning device, a printer, a facsimile, a multifunction device having at least two of these functions, and an image forming device such as a plotter. About.

In image recording in electrophotography, an image forming method using a laser is widely used as an image forming means for obtaining high-definition image quality. In the case of electrophotography, a method of forming a latent image by rotating a drum (sub-scanning) while scanning a laser (main scanning) using a polygon mirror in the axial direction of a photosensitive drum is used.
In such an electrophotographic field, higher density of images and higher speed of image output are required. However, image densification and image output speed are in a trade-off relationship and are required to be compatible.

As a method for achieving both, it is conceivable to increase the rotation speed of the polygon scanner. However, this increases the noise of the polygon scanner, the power consumption, and the durability.
As a method for preventing this, there is a multi-beam method, and the following methods can be considered.
(1) As described in Patent Document 2 and the like, a method of synthesizing a plurality of end surface light emitting LDs (2) a one-dimensional LD array for end surface light emission (3) a two-dimensional LD array

Here, the method of synthesizing the edge-emitting LD is inexpensive because a general-purpose 1LD can be used, but it is difficult to stably maintain the relative positional relationship between the LD and the coupling lens with a plurality of beams. In other words, the interval between the scanning lines formed on the surface to be scanned by the multi-beam becomes non-uniform. In this method, it is difficult to have a very large number of light sources, and it is difficult to achieve ultra high density and high speed.
The one-dimensional LD array of edge emission can make the scanning line interval uniform, but the power consumption of the element increases. Further, if the number of beams is extremely increased, the amount of deviation of the beam from the optical axis of the optical element of the optical system increases, and the optical characteristics deteriorate.
On the other hand, a surface emitting laser (vertical cavity surface emitting laser, VCSEL) is a semiconductor laser that emits light in a direction perpendicular to a substrate, and is easily two-dimensionally integrated. Further, the power consumption is about an order of magnitude smaller than that of the edge type laser, which is advantageous for integrating more light sources in two dimensions.

As examples of a writing optical system that scans using polygons, those described in Patent Documents 1 and 2 are known.
Patent Document 1 describes an image forming apparatus using a surface-emitting LD, and the distance between the most peripheral light sources in the main scanning direction is shorter than the distance between the most peripheral light sources in the sub-scanning direction. Yes.
Patent Document 2 describes a configuration in which a two-dimensionally arranged light source and a scanning optical system are combined, and the distance between the most peripheral light sources in the main scanning direction and the distance between the most peripheral light sources in the sub-scanning direction. Are the same length.

JP 2004-287292 A JP-A-2005-250319

As described above, conventionally, the distance between the most peripheral light sources in the main scanning direction is shorter than or equal to the distance between the most peripheral light sources in the sub-scanning direction.
At this time, in order to obtain a scanning line interval corresponding to high density on the surface to be scanned, it is necessary to reduce the absolute value of the lateral magnification in the sub-scanning direction of the optical system, resulting in insufficient light quantity. In particular, in the case of a surface emitting laser element, high output is a big problem, which is a serious problem. In particular, with the configuration described in Patent Document 1, it is difficult to achieve both ultra-high density and light intensity.
Further, in order to reduce the absolute value of the lateral magnification in the sub-scanning direction of the entire optical system, it is necessary to bring the optical element closest to the scanning surface of the scanning optical system and having positive power in the sub-scanning direction closer to the scanning surface. For this reason, the size of the optical element closest to the surface to be scanned increases, resulting in an increase in cost.

In addition, the housing for mounting the optical element becomes large, resulting in a problem that the machine size (device size) becomes large. Further, the space between the surface to be scanned and the scanning optical system is narrowed, the amount of toner that can be deployed is reduced, and it is necessary to frequently replace the toner.
In addition, a space for arranging a means for carrying out an electrophotographic process such as a charging means, a transfer means, a developing means, and a fixing means necessary for image output is reduced, and the charging means is on the opposite side to the scanning optical system. Therefore, the transfer unit, the developing unit, and the fixing unit must be provided, and the machine size becomes large.
Another method for reducing the absolute value of the lateral magnification in the sub-scanning direction of the entire optical system is to reduce the absolute value of the lateral magnification in the sub-scanning direction of the pre-deflector optical system. Therefore, it is necessary to bring the line image forming lens close to the deflecting means close to the deflecting means (polygon scanner), and there is a problem that the line image forming lens is affected by heat generation by the polygon scanner.

  The present invention provides an optical scanning device capable of realizing high speed and high density by improving the light utilization efficiency, and obtaining good optical characteristics in both the main scanning direction and the sub-scanning direction. An object of the present invention is to provide an image forming apparatus having a scanning device.

To achieve the above object, according to the first aspect of the present invention, a light source in which a plurality of semiconductor lasers are arranged two-dimensionally, a first optical system for guiding a plurality of beams from the light source to a deflecting means, and the deflecting means and a second optical system for guiding the scanned surface multiple beams from said first optical system includes a coupling lens for coupling the beam emitted from the light source, the beam from the coupling lens An anamorphic lens that forms a line image that is long in the main scanning direction, and an opening that restricts the light beam in the main scanning direction and the sub-scanning direction with respect to the beam emitted from the coupling lens, and in the main scanning direction The distance between the light sources at the outermost periphery is longer than the distance between the light sources at the outermost periphery in the sub-scanning direction, the anamorphic lens has a positive power in the main scanning direction, and width Greater than the sub-scanning direction width, at least one of the outermost periphery of the light emitting portion of the light source is directed to an optical scanning apparatus characterized by increasing the light emission amount from the light emission portion other than the most peripheral.

The invention according to claim 2 is an image forming apparatus using the optical scanning device according to claim 1 .

According to a third aspect of the invention, a multi-color image forming apparatus using the optical scanning device according to the first aspect is provided .

According to the present invention, according to the present invention, if the distance between the most peripheral light sources in the main scanning direction is longer than the distance between the most peripheral light sources in the sub-scanning direction, it becomes easy to cope with high density, and the anamorphic lens By having positive power in the main scanning direction, the distance between the beams on the polygon mirror surface of the two most peripheral beams is shortened, and good optical characteristics can be obtained in both main scanning and sub scanning.
Further, by using the surface emitting LD array, the polygon scanner can be rotated at a low speed, and the power consumption for driving the light source can be reduced.
In addition, it is possible to realize an optical scanning device that can reduce variations in the amount of light and has no density unevenness.
In addition, an image forming apparatus compatible with high density and high speed can be provided.

A first embodiment of the present invention will be described below with reference to FIGS.
First, the basic configuration of the optical scanning device according to the present embodiment will be described with reference to FIG. The light source 1 is a two-dimensionally arranged semiconductor laser. The light beam emitted from the light source 1 becomes weakly divergent light by the coupling lens 2, passes through the aperture 3 as an opening, and is parallel light in the main scanning direction by the anamorphic lens 4, and in the vicinity of the polygon mirror 5 as the deflecting means in the sub-scanning direction. The light beam is focused.
The light beam is further deflected by the polygon mirror 5, and forms an image on the image surface 9 as a scanned surface through the dust-proof glass 8 by the deflector side scanning lens 6 and the image surface side scanning lens 7. A soundproof glass 10 is disposed between the polygon mirror 5 and the deflector-side scanning lens 6. The light source 1 and the coupling lens 2 are fixed to the same member made of aluminum.
Reference numeral 11 denotes a dummy mirror. The coupling lens 2, the aperture 3, the anamorphic lens 4, the dummy mirror 11, and the soundproof glass 10 constitute a first optical system that guides a plurality of beams from the light source 1 to the polygon mirror 5.
The soundproof glass 10, the deflector side scanning lens 6, the image plane side scanning lens 7, and the dustproof glass 8 constitute a second optical system that guides a plurality of beams from the polygon mirror 5 to the scanned surface.

Next, the light source 1 composed of a surface emitting laser array will be described in detail.
The surface emitting laser array of this embodiment can be manufactured as follows. This is a structural example of a 780-nm band surface emitting laser using a current confinement structure in which an AlAs layer is selectively oxidized.
The wavelength can be selected according to the sensitivity characteristics of the photoconductor as the image carrier. FIG. 3 shows a schematic diagram of a cross-sectional structure. FIG. 4 shows an enlarged view of the periphery A of the active layer.
As shown in FIG. 3, the surface emitting laser element has an active layer 21 made of an Al _0.12 Ga _0.88 As quantum well layer / Al _0.3 Ga _0.7 As barrier layer on an n-GaAs substrate 20. 1 wavelength optical thickness resonator region composed of Al _0.6 Ga _0.4 As spacer layer 22 and 40.5 pairs of n-Al _0.3 Ga with an optical thickness of each layer λ / 4. Lower reflector 23 composed of _0.7 As high refractive index layer / n-Al _0.9 Ga _0.1 As low refractive index layer and 24 pairs of p-Al _0.3 Ga _0.7 As high refractive index layer / P-Al _0.9 Ga _0.1 As The structure is sandwiched between the upper reflecting mirrors 24 made of a low refractive index layer.

Further, an AlAs selectively oxidized layer (current injection portion) 25 is provided on the upper reflecting mirror 24 that is λ / 4 away from the resonator region. In addition, between each layer of a reflective mirror, the composition gradient layer from which a composition changes gradually for resistance reduction is included.
For these crystal growths, MOCVD or MBE can be used. Next, a mesa shape is formed by dry etching. In general, the etching surface reaches the lower reflecting mirror 23. Next, the AlAs selective oxidation layer 25 whose side surfaces are exposed by the etching process is heat-treated in water vapor to oxidize the surroundings to an AlxOy insulator layer, and the device driving current path is not oxidized at the center. A current confinement structure is formed that limits only to the region. Subsequently, a SiO ₂ protective layer (not shown) is provided, and the etched portion is further filled with polyimide to be flattened. On the upper reflector 24 having the p contact layer (p-GaAs contact layer) 26 and the light emitting portion 27. The polyimide and the SiO ₂ protective layer (not shown) were removed, the p-side individual electrode 28 was formed in addition to the light emitting portion 27 on the p-contact layer 26, and the n-side common electrode 29 was formed on the back surface.

In FIG. 3, reference numeral 30 denotes an AlxOy current confinement layer, and 31 denotes an insulating film (polyimide).
In FIG. 4, reference numeral 32 denotes an Al _0.12 Ga _0.88 As active layer, 33 denotes an Al _0.3 Ga _0.7 As barrier layer, and 34 denotes an Al _0.6 Ga _0.4 As upper part. The spacer layer, 35 is an Al _0.6 Ga _0.4 As lower spacer layer, 36 is an Al _0.9 Ga _0.1 As low refractive index layer (λ / 4) at the bottom of the upper reflector, _Reference numeral 37 denotes an Al _0.9 Ga _0.1 As low refractive index layer (λ / 4) at the top of the lower reflecting mirror.

In the case of this embodiment, the mesa portion formed by the dry etching method becomes each surface emitting laser element. The method of forming the array arrangement of the present invention can be formed by forming a photomask along the array arrangement of the present invention, forming an etching mask by a normal photolithography process, and etching.
For electrical and spatial separation of each element of the array, it is preferable to provide a groove between the elements of about 5 μm or more. This is because if it is too narrow, it becomes difficult to control etching. In addition to the circular shape as in the present embodiment, the mesa portion can have any shape such as an ellipse, a square, or a rectangular rectangle. Further, the size (diameter or the like) is preferably about 10 μm or more. This is because if it is too small, heat is accumulated during device operation, and the characteristics deteriorate.

The array arrangement of the present embodiment is a 4 × 8 array as shown in FIG. The adjacent elements in the sub-scanning direction are equally spaced: d, and the positional relationship of the array in the sub-scanning direction is equally spaced C ′ = d / n. The adjacent elements in the main scanning direction are at equal intervals: X. Specifically, d was 18.4 μm and X was 30 μm. C ′ = 2.3 μm.
When the element spacings d and X of the present embodiment are applied to the conventional example shown in FIG. 2, C = d / n = 4.6 μm. Therefore, a perpendicular line is dropped from the center of each element of the array of the present embodiment in the sub-scanning direction. The distance C ′ between the elements in the sub-scanning direction at this time is 50%, and it can be seen that according to the present invention, the density becomes high even if the element spacing in the plane is the same.
Note that the element spacings d and X need to be determined in consideration of the influence of thermal interference from other elements when operating in the array in addition to the above process restrictions.
In addition, since the element spacing in the main scanning direction that does not affect the density increase in the sub-scanning direction has been expanded, the effect of thermal interference between each element is reduced and the space required to pass the wiring of each element is secured. can do.

Note that the above-described 780 nm band surface emitting laser can be manufactured using another material. FIG. 5 shows an enlarged view around the active layer.
As shown in FIG. 5, the active layer has a compressive strain composition, a GaInPAs quantum well active layer 32 ′ having a band gap wavelength of 780 nm, and a Ga _0.6 In having a lattice-matched four-layer tensile strain. A clad layer (in this embodiment, spacer layers 34 'and 35' in the present embodiment) that is composed of a _0.4 P barrier layer 33 'and has a wide band gap (Al _0.7 Ga _0.3 ) _{0 .5} In _0.5 P is used.
The band gap difference between the cladding layer and the quantum well active layer can be made extremely large as compared with the case where the carrier confinement cladding layer is formed of AlGaAs. Others are the same as FIG.

  Table 1 shows an AlGaAs (spacer layer) / AlGaAs (quantum well active layer) system 780 nm and 850 nm surface emitting semiconductor laser, and an AlGaInP (spacer layer) / GaInPAs (quantum well active layer) system 780 nm surface emitting semiconductor laser. The band gap difference between the spacer layer and the well layer and the barrier layer and the well layer with the typical material composition is shown. Note that the spacer layer is a layer between the active layer and the reflecting mirror in the case of a normal configuration, and indicates a layer having a function as a cladding layer for confining carriers.

As shown in Table 1, according to the AlGaInP (spacer layer) / GaInPAs (quantum well active layer) system 780 nm surface emitting semiconductor laser, the AlGaAs / AlGaAs system 780 nm surface emitting semiconductor laser as well as the AlGaAs / AlGaAs system 850 nm surface are used. It can be seen that the band gap difference can be made larger than that of the light emitting semiconductor laser.
Specifically, the band gap difference between the clad layer and the active layer is 743 meV, which is extremely large, compared to 466 meV (when the Al composition is 0.6) when the clad layer is formed of AlGaAs. Similarly, the band gap difference between the barrier layer and the active layer also has a dominant difference, resulting in good carrier confinement.
In addition, since the active layer has compressive strain, the increase in gain is increased by band separation of heavy holes and light holes. Because of these high gains, the output was high at a low threshold.

This effect cannot be obtained with a 780 nm or 850 nm surface emitting laser made of an AlGaAs system having substantially the same lattice constant as the GaAs substrate.
Further, by lowering the threshold value by improving carrier confinement and increasing the gain by the strained quantum well active layer, the reflectivity of the light extraction side DBR can be reduced, and the output can be further increased.
Further, when the gain is increased as in this embodiment, a decrease in light output due to a temperature rise can be suppressed, and the array element spacing can be further narrowed.
In addition, the active layer and the barrier layer are made of a material that does not contain Al, and are formed as an Al-free active region (a quantum well active layer and a layer adjacent thereto). The formation of the light-emitting recombination center can be suppressed, and the life can be extended. Thereby, the writing unit (optical scanning device) or the light source unit can be reused.

The optical scanning device according to this embodiment will be described in more detail.
As shown in FIG. 2, the conventional two-dimensional LD array has four columns in the main scanning direction and eight rows in the sub-scanning direction. Therefore, the distance between the most peripheral light sources in the main scanning direction is (n−1) × X = 3X (n = 4), and the distance between the most peripheral light sources in the sub-scanning direction is (m−1) × d = 7d (m = 8), and 7d> 3X.
At this time, if the horizontal magnification in the sub-scanning direction of the entire optical system is βs, the pitch of the scanning line interval on the surface to be scanned is | βs | × d / 4, and a desired pitch can be obtained in the case of high density correspondence. It becomes difficult.
For example, in the case of 2400 dpi, 25.4 / 2400 = 10.6 μm, and in the case of 4800 dpi, 25.4 mm / 4800 = 5.3 μm, but | βs | × d / n needs to be equal to this value There is.

One means for achieving this is illustrated in FIG. As shown in the figure, there are 8 columns in the main scanning direction and 4 rows in the sub-scanning direction. Accordingly, the distance between the most peripheral light sources in the main scanning direction is (n−1) × X = 7X (n = 8), and the distance between the most peripheral light sources in the sub-scanning direction is (m−1) × d = 3d (m = 4) and 7X> 3d.
Therefore, the distance between the most peripheral light sources in the main scanning direction is longer than the distance between the most peripheral light sources in the sub-scanning direction. At this time, the pitch of the scanning line interval on the surface to be scanned is | βs | × d / 7, which makes it easier to obtain a desired pitch in the case of high density support than in the conventional example.
That is, when the distance between the light sources in the outermost periphery in the main scanning direction is made longer than the distance between the light sources in the outermost periphery in the sub-scanning direction, it becomes easy to cope with high density. However, the distance between the outermost periphery of the light source in the main scanning direction becomes large.

At this time, as shown in FIG. 7A, the two most peripheral beams are greatly separated on the polygon mirror surface, and the beam spot diameters in the main scanning and sub-scanning directions are improved with respect to all the beams. It becomes difficult.
Therefore, as shown in FIG. 7B, when the anamorphic lens 4 has a positive power in the main scanning direction, the distance between the beams on the polygon mirror surface of the two most peripheral beams becomes short, and the main scanning, sub-scanning, Good optical characteristics can be obtained in both scanning.

As described above, making the distance between the outermost beams in the main scanning direction longer than the distance between the outermost beams in the sub-scanning direction is effective for increasing the density in the sub-scanning direction.
At this time, if the aperture diameter for restricting the beam is larger on the sub-scanning side than on the main-scanning side, the light amount variation becomes large. 8A and 8B, the amount of optical axis deviation from the coupling lens 2 is the same for both main scanning and sub-scanning, and the aperture diameter in the main scanning direction (main aperture diameter) is the aperture diameter in the sub-scanning direction (sub-scanning). In this case, as can be seen from this figure, the larger the aperture diameter, the smaller the light quantity change rate (reduction amount) with respect to the optical axis deviation. Therefore, it is necessary to make the aperture diameter in the main scanning direction with a large optical axis deviation larger than the aperture diameter in the sub-scanning direction.

  As shown in FIG. 9, since the beam at the outermost periphery does not coincide with the center of the aperture 3 and the center of the beam, the light utilization efficiency of the peripheral beam is lower than that of the center beam. Therefore, by setting the light amount of the most peripheral beam high, an optical scanning device without density unevenness can be realized.

Based on FIG. 10, the outline of the configuration of the image forming apparatus according to the present embodiment will be described.
A photoconductor 100 as an image carrier, which is a surface to be scanned, is uniformly charged by a charging unit 101, and an electrostatic latent image is formed by the optical scanning device 102 described above. The electrostatic latent image is developed with toner by the developing unit 103 and visualized.
The toner image on the photoconductor 100 is transferred by the transfer unit 104 onto the sheet-like recording medium S conveyed at a predetermined timing from a paper supply unit (not shown). The sheet-like recording medium S to which the toner image has been transferred is sent to the fixing means 105 where the toner image is fixed by heat and pressure. The sheet-like recording medium S that has been fixed is stacked on a paper discharge tray (not shown).
Residual toner is removed from the surface of the photoreceptor 100 after the transfer by the cleaning means 106. Thereafter, the surface potential of the photoconductor 100 is initialized and prepared for the next image forming process.
By using this optical scanning apparatus 102, a high-density and high-speed compatible image forming apparatus can be provided.

A second embodiment (multicolor image forming apparatus) will be described with reference to FIG. In FIG. 11, photoconductors 201Y, 201M, 201C, and 201K rotate in the direction of the arrow, and charging members 202Y, 202M, 202C, and 202K, developing devices 204Y, 204M, 204C, and 204K, transfer charging units 206Y and 206M are rotated in the order of rotation. 206C, 206K and cleaning means 205Y, 205M, 205C, 205K are provided.
The charging members 202Y, 202M, 202C, and 202K are members that constitute a charging device for uniformly charging the surface of the photoreceptor. The surface of the photosensitive member between the charging member and the developing devices 204Y, 204M, 204C, and 204K is irradiated with a beam by an optical scanning device (writing unit) 207 so that an electrostatic latent image is formed on the photosensitive member. .
Based on the electrostatic latent image, each developing device 204 forms a toner image on the surface of the photoreceptor. The transfer charging units 206Y, 206M, 206C, and 206K sequentially transfer the toner images of the respective colors onto a recording sheet (not shown) conveyed by the conveyance belt 208, and finally the fixing unit 210 fixes the image on the recording test.

(Example)
The optical system data is shown below.
The light source wavelength is 780 nm, and the arrangement shown in FIG.
The light emitting area diameter is 4 μm, and as described above, the array is 4 × 8, and d = 18.4 μm and X = 30 μm.
The coupling lens is expressed by the following equation on both sides.
x = (h ^ 2 / R) / [1 + √ {1- (1 + K) (h / R) ^ 2}] + A4 · h ^ 4 + A6 · h ^ 6 + A8 · h ^ 8 + A10 · h ^ 10 (1) )
Here, when the distance from the optical axis is h, the paraxial radius of curvature is R, the conic constant is K, and the higher order coefficient is A4, the coefficients are as follows.
(First side)
R = 98.97
K = −18.9
A4 = −2.748510E-06
A6 = 7.513797-07
A8 = −5.817478-08
A10 = −2.4475370-09
(Second side)
R = −31.07
K = −0.35
A4 = 1.210E-06
A6 = 6.782E-08
A8 = 2.523E-08
A10 -4.670E-09
The refractive index is 1.5119. Here, d1 (see FIG. 6, the same applies hereinafter) = 42.39, and a cover glass having a refractive index of 1.5112 and a thickness of 0.3 is inserted therebetween. D2 = 3.8.

The anamorphic lens is a cylindrical surface having a first surface having power in the sub-scanning direction, and a second surface having a positive power in the main scanning direction. Since it has a positive power in the main scanning direction, the above effect can be obtained.
The sub-scanning radius of curvature of the first surface is 55, and the main scanning radius of curvature of the second surface is -500.
Here, d3 = 117.2 and d4 = 3.

The aperture is disposed at a position 58.2 mm away from the second surface of the anamorphic lens toward the deflecting unit, and is disposed closer to the deflector than the rear focal position of the coupling lens. Here, d5 = 120.2.
At this time, a soundproof glass having a wall thickness of 1.9 mm and a refractive index of 1.5112 is provided between the anamorphic lens and the polygon mirror and between the polygon mirror and the scanning lens 6. Here, the polygon mirror has four surfaces and the inscribed circle radius is 7 mm.
D6 = 36.7, d7 = 8, d8 = 101.9, d9 = 3, d10 = 138.2. The dust-proof glass No. 8 has a refractive index of 1.5112 and a wall thickness of 1.9 mm.

In Table 2, R _m is "paraxial curvature in the main scanning direction", R _s is a "paraxial curvature in the sub-scanning direction", D is represents the distance between the optical elements. The unit is mm.
A 9 mm dust-proof glass G2 is arranged. Each surface of the scanning lens 6 and the scanning lens 7 is an aspherical surface, and the entire surface has a “non-arc shape given by Formula 1” in the main scanning direction, and a sub-scanning section (virtual parallel to the optical axis and the sub-scanning direction). This is a special surface in which the curvature in the target cross-section “changes according to Equation 2” in the main scanning direction.

"Change of curvature in sub-scan section"
Curvature in the sub-scanning section: C _s (Y) (Y: coordinates in the main scanning direction with the optical axis position as the origin) is expressed in the sub-scanning section including the optical axis. The curvature radii of: R _s (0), B ₁ , B ₂ , B ₃ ,.
Cs (Y) = 1 / Rs (0) + B1 · Y + B2 · Y ^ 2 + B3 · Y ^ 3 + (2)

  Table 3 lists the coefficients of the incident side surface (special surface) of the scanning lens 6.

  Table 4 lists the coefficients of the exit side surface (special surface) of the scanning lens 6.

  Table 5 lists the coefficients of the incident side surface (special surface) of the scanning lens 7.

  Table 6 lists the coefficients of the exit side surface (special surface) of the scanning lens 7.

Further, the aperture diameter is a rectangular shape having a main size of 5.5 mm and a sub size of 1.18 mm.
The aberration diagram is shown in FIG.
The beam spot diameter is as follows and is corrected well.
Image height (mm) Main scan Sub scan (μm)
-161.5 54.12 56.48
-150 53.49 55.90
-100 53.54 55.65
-50 52.80 54.71
0 52.33 54.08
50 52.86 54.73
100 53.51 55.67
150 53.38 55.88
161.5 54.24 56.46
At this time, | βm | = 4.9 and | βs | = 2.3, and a scanning line interval of 5.3 μm can be obtained on the surface to be scanned, which is applicable to 4800 dpi.

It is a schematic plan view which shows arrangement | positioning of the surface emitting laser array of the optical scanning device which concerns on 1st Embodiment. It is a schematic plan view which shows arrangement | positioning of the surface emitting laser array in the past. It is sectional drawing of the element of the surface emitting laser array shown in FIG. It is an expanded sectional view of the active layer periphery structure of the A section of FIG. It is a figure which shows the modification of the part shown in FIG. It is main scanning sectional drawing of an optical scanning device. It is a figure which shows the beam state when the distance between the most peripheral light sources in the main scanning direction is made longer than the distance between the most peripheral light sources in the sub-scanning direction. The figure which shows the malfunction which will end, (b) is a figure which shows the state which corrected this malfunction by the characteristic of an anamorphic lens. It is a figure which shows the relationship between an aperture diameter and the light quantity change rate with respect to an optical axis deviation, and is a figure in case the aperture diameter of a main scanning direction is larger than the aperture diameter of a subscanning direction. It is a figure which shows the state in which the light utilization efficiency of a peripheral beam is falling with respect to a center beam. 1 is a schematic configuration diagram of an image forming apparatus. It is a schematic block diagram of the multicolor image forming apparatus which concerns on 2nd Embodiment. FIG. 6 is an aberration diagram according to Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Coupling lens 3 Aperture as opening 4 Anamorphic lens 5 Polygon mirror as deflection means

Claims (3)

A light source in which a plurality of semiconductor lasers are arranged two-dimensionally;
A first optical system for guiding a plurality of beams from the light source to a deflecting means;
And a second optical system for guiding the scanned surface multiple beams from said deflecting means,
The first optical system includes a coupling lens that couples a beam emitted from the light source , an anamorphic lens that forms a beam image from the coupling lens into a line image that is long in a main scanning direction , and the coupling lens. An opening that restricts the light beam in the main scanning direction and the sub-scanning direction with respect to the emitted beam , and
The distance between the light sources at the outermost periphery in the main scanning direction is longer than the distance between the light sources at the outermost periphery in the sub-scanning direction,
The anamorphic lens has a positive power in the main scanning direction,
The width of the opening in the main scanning direction is larger than the width in the sub-scanning direction,
An optical scanning device characterized in that at least one of the light emitting parts at the outermost periphery of the light source has a larger light emission amount than light emitting parts other than the light emitting element at the outermost periphery . An image forming apparatus using the optical scanning device according to claim 1 . A multicolor image forming apparatus using the optical scanning device according to claim 1.

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