JP5261894B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner of a new configuration capable of being made high in operating speed and high in density by improving availability of light rays. <P>SOLUTION: The optical scanner has: a light source 1 in which a plurality of light emitting elements are arranged two-dimensionally; first optical systems 2 to 4 which guide the plurality of light beams from the light sources 1 to a deflection means 5; and second optical systems 6 and 7 which guide the plurality of light beams from the deflection means 5 to a face 9 to be scanned. When the scanning direction with the deflection means 5 is defined as a main scanning direction and the direction which is orthogonal to the main scanning direction and to the optical axes of the first and the second optical systems is defined as a subscanning direction, the distance between the light emitting elements on the outermost periphery in the main scanning direction is longer than that between the light emitting elements on the outermost periphery in the subscanning direction, further, the absolute value ¾&beta;s¾ of the transverse magnification in the subscanning direction of the optical systems is made larger than the absolute value ¾&beta;m¾ of the transverse magnification in the main scanning direction, thus the beam pitch on a face to be scanned is made small, thereby easily making the optical scanner high in density and high in operating speed. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an optical scanning device and an image forming apparatus such as a digital copying machine, a facsimile, a printer, a plotter, or a complex machine using the optical scanning device.

  In image recording in an electrophotographic image forming apparatus, 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 an electrophotographic system, a laser is scanned (main scanning) using a polygon scanner (rotating polygonal mirror) which is one of deflection means in the axial direction of a photosensitive image carrier (for example, a photosensitive drum), A general method is to form a latent image by rotating the photosensitive drum (sub-scanning). In the field of electrophotography, there is a demand for higher image density and faster image output. 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 high image density and image output speed, it is conceivable to increase the rotation speed of the polygon scanner. However, this increases the noise of the polygon scanner, increases the power consumption, and deteriorates the durability.

Therefore, as a method for preventing such a problem, there is a multi-beam light source, and the following methods are conceivable.
(1) A method of combining light beams from a plurality of light sources (for example, edge-emitting semiconductor lasers (LDs)) (see Patent Document 1, etc.).
(2) A method using an edge-emitting type one-dimensional LD array in which a plurality of light-emitting elements are arranged one-dimensionally.
(3) A method using a surface-emitting type two-dimensional LD array in which a plurality of light-emitting elements are two-dimensionally arranged.

  Here, in the method of combining light beams from a plurality of edge-emitting LDs, a general-purpose semiconductor laser (LD) can be used, which is inexpensive, but the relative positional relationship between the LD and the coupling lens. Is difficult to stably maintain with a plurality of light beams, and 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.

  In the method using the edge-emitting type one-dimensional LD array, the edge-emitting type one-dimensional LD array can make the scanning line interval uniform, but the power consumption of the light-emitting element increases, the beam When the number is extremely increased, there is a problem that 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, in a method using a surface emitting type two-dimensional LD array, a surface emitting laser (vertical cavity surface emitting laser, VCSEL) is a semiconductor laser (LD) that emits light in a direction perpendicular to a substrate. Two-dimensional integration is easy. Furthermore, the power consumption is about an order of magnitude smaller than that of the edge-emitting laser, which is advantageous for two-dimensional integration of more light sources. FIG. 12 shows an example of the arrangement of light emitting elements of a conventional surface emitting laser array. In this example, 32 light emitting elements are arranged in 8 rows × 4 columns.

  By the way, as an example of a writing optical system that scans using a polygon scanner, there are conventional techniques described in Patent Document 1 and Patent Document 2, but the distance between the most peripheral light sources in the main scanning direction is the maximum in the sub-scanning direction. It is shorter than or equal to the distance between surrounding light sources. 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 type laser element, high output is a big problem, which is a serious problem. Further, in order to reduce the absolute value of the lateral magnification in the sub-scanning direction of the entire optical system, an optical element having a positive power in the sub-scanning direction is disposed at a position closest to the scanning surface of the scanning optical system. It is necessary to bring the optical element closer to the surface to be scanned. For this reason, the size of the optical element closest to the surface to be scanned is increased, 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 becomes large. Further, the space between the surface to be scanned and the scanning optical system is narrowed, the amount of toner in the developing unit that can be provided in the image forming apparatus is reduced, and toner replacement must be performed frequently. 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 optical system in front of the deflecting means. At this time, it is necessary to bring a line image forming optical element (for example, a cylindrical lens) close to the deflecting means close to the deflecting means (polygon scanner), and the line image forming optical element is affected by heat generation by the polygon scanner. The problem occurs.

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

  The present invention has been made in view of the above circumstances, and can solve the above-described problems of the prior art and improve the light utilization efficiency, thereby realizing a high speed and a high density. Another object of the present invention is to provide an optical scanning device having a simple structure, and further to provide an image forming device that includes the optical scanning device and can perform image formation corresponding to high speed and high density. To do.

In order to achieve the above object, the present invention employs the following technical means.
The first means of the present invention is an optical scanning device, wherein a light source in which a plurality of light emitting elements are arranged two-dimensionally, a first optical system for guiding a plurality of light beams from the light source to a deflecting means, A second optical system for guiding a plurality of light beams from the deflecting means to the surface to be scanned, the scanning direction by the deflecting means being the main scanning direction, and the main scanning direction and the optical axes of the first and second optical systems The distance between the outermost light emitting elements in the main scanning direction is longer than the distance between the outermost light emitting elements in the sub scanning direction, and the first optical system Has a coupling lens for coupling a plurality of light beams emitted from the light source, and an opening for restricting at least a light beam in the main scanning direction with respect to the plurality of light beams emitted from the coupling lens. The opening is on the rear side of the coupling lens. From the point position, characterized in that it is deployed side closer to the deflection means.
According to a second means of the present invention, in the optical scanning device of the first means, the opening restricts the light flux in the main scanning direction and the sub-scanning direction, and the width of the opening in the main scanning direction is the same as that in the sub-scanning direction. It is characterized by being larger than the width .
According to a third means of the present invention, in the optical scanning device of the second means, at least one of the outermost light emitting elements among the two-dimensionally arranged light emitting elements is more than the light emitting elements other than the outermost periphery. It is characterized by increasing the light emission amount.
According to a fourth means of the present invention, in the optical scanning device of any one of the first to third means, the lateral magnification in the main scanning direction of the optical system between the light source and the scanned surface is βm, and the light source When the horizontal magnification in the sub-scanning direction of the optical system between the scanning surface and the scanning surface is βs,
| Βm |> | βs |
It satisfies the following conditions.

According to a fifth means of the present invention, in the optical scanning device according to any one of the first to fourth means, the light source in which the plurality of light emitting elements are arranged two-dimensionally has each light emitting element in the sub-scanning direction. M (m ≧ 2) are arranged in a one-dimensional manner, and n (n ≧ 2) one-dimensional columns in the sub-scanning direction are arranged substantially in the main scanning direction, and m × n light emission is performed. The positional relationship of each light emitting element in the sub-scanning direction when the perpendicular is lowered from the element (m ≦ n) to a straight line parallel to the sub-scanning direction is equal.
According to a sixth means of the present invention, in the optical scanning device according to any one of the first to fifth means, the light source in which the plurality of light emitting elements are arranged two-dimensionally is a primary light in the sub-scanning direction. When the arrangement pitch of the original m light emitting elements is d and the arrangement pitch of the n arrangements in the main scanning direction is X,
X> d
It is characterized by.

The seventh means of the present invention is a photosensitive drum as an image carrier, a charging device that uniformly charges the surface of the photosensitive member, an optical scanning device that forms an electrostatic latent image by irradiating the photosensitive drum with a light beam, In an image forming apparatus including a developing device that develops an electrostatic latent image with toner and a transfer device that transfers the image to a recording medium, image formation is performed using the optical scanning device of any one of the first to sixth means. It is characterized by.
According to an eighth means of the present invention, in the image forming apparatus of the seventh means , at least the photosensitive drum and the charging device are arranged in parallel, and the developing device includes a multicolor developing device, A multicolor image is formed by using the optical scanning device of any one of the sixth to sixth means.

The optical scanning device of the first means of the present invention is characterized in that the distance between the most peripheral light emitting elements in the main scanning direction is longer than the distance between the most peripheral light emitting elements in the sub-scanning direction. It becomes easy to handle. In the optical scanning device of the fourth means, in addition to the above configuration, the absolute value | βs | of the lateral magnification in the sub-scanning direction of the entire optical system is further calculated from the absolute value | βm | of the lateral magnification in the main scanning direction. by also increasing, it is possible to reduce the pitch on the surface to be scanned, corresponds becomes easier to densification.
Further, by using a surface-emitting LD array in which a plurality of light emitting elements are arranged two-dimensionally as a light source, the deflection means (for example, a polygon scanner) can be rotated at a low speed, and further, the light source is driven. The power consumption can be reduced.

In the optical scanning device of the fifth means, in addition to the above-described configuration, the light source in which the plurality of light emitting elements are arranged two-dimensionally includes m light emitting elements one-dimensionally in the sub-scanning direction (m ≧ 2). And n (n ≧ 2) one-dimensional rows in the sub-scanning direction are arranged in the main scanning direction, and from the m × n light emitting elements (m ≦ n) in the sub-scanning direction. The positional relationship of the light emitting elements in the sub-scanning direction when the perpendicular is drawn down to a straight line parallel to is equal to each other, and the configuration of the first means is the number of columns and rows of the light emitting elements. The effect similar to the above can be acquired by prescribing by the relationship.
In addition, in the optical scanning device of the sixth means, in addition to the above configuration, the light source in which the plurality of light emitting elements are arranged in a two-dimensional manner is a light emitting element in a one-dimensional array of m in the sub-scanning direction. When the arrangement pitch is d and the arrangement pitch of the n arrangements in the main scanning direction is X,
X> d
As a result, the element spacing in the main scanning direction, which does not affect the increase in density in the sub-scanning direction, is widened, and it is necessary to reduce the influence of thermal interference between elements and to pass the wiring of each element. Space can be secured.

In the optical scanning device of the first means, the addition to the configuration of the first means, said first optical system includes a coupling lens for coupling the plurality of light beams emitted from the light source, the coupling lens An opening (for example, an aperture) that restricts at least a light beam in the main scanning direction with respect to the plurality of light beams emitted from the light source. By being arranged on the side closer to the polygon scanner, the distance between the center lines of the outermost light beams on the deflecting reflecting surface (for example, the polygon mirror surface) of the deflecting means is shortened, and the image planes of main scanning and sub scanning are reduced. The curvature can be improved, and a good beam spot diameter can be obtained in both main scanning and sub-scanning.

In the optical scanning device of the third means, in addition to the configuration of the second means, at least one of the most peripheral light emitting elements among the two-dimensionally arranged light emitting elements is more than the light emitting elements other than the most peripheral light emitting elements. By increasing the light emission amount, it is possible to suppress a decrease in the light amount of the most peripheral beam. That is, when a light source in which a plurality of light emitting elements are arranged two-dimensionally is used, the center of the opening (for example, aperture) and the center of the beam of the light beam at the outermost periphery do not coincide with each other (see FIG. 7). The peripheral beam has lower light utilization efficiency than the central beam. Therefore, by increasing the light emission amount of the most peripheral light emitting element and setting the light amount of the most peripheral beam high, it is possible to realize an optical scanning device having no density unevenness.

In the optical scanning device of the second means, the first optical system includes a coupling lens for coupling a plurality of light beams emitted from the light source, and a plurality of light beams emitted from the coupling lens. On the other hand, it has an opening (for example, an aperture) that restricts a light beam in the main scanning direction and the sub-scanning direction, and the width of the opening in the main scanning direction is larger than the width in the sub-scanning direction, thereby reducing variation in the amount of light. can do.
Here, in the configurations of the fourth to sixth means, the amount of optical axis deviation of the most peripheral beam from the coupling lens is larger in the main scanning direction than in the sub scanning direction. However, when the aperture diameter for restricting the beam is larger in the sub-scanning direction than in the main scanning direction, the light amount variation becomes large. 8A and 8B, the amount of optical axis deviation from the coupling lens is the same for both the main scanning and the sub scanning, and the aperture diameter in the main scanning direction (the main aperture diameter in FIG. 8B) is the sub scanning direction. Is larger than the aperture diameter (sub-aperture diameter in FIG. 8A). As can be seen from FIG. 8, at this time, the larger the aperture diameter, the smaller the light quantity change rate with respect to the optical axis deviation. I understand that. 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. In order to make the horizontal magnification in the sub-scanning direction smaller than the horizontal magnification in the main scanning direction,
It is necessary to increase the aperture diameter in the main scanning direction / the aperture diameter in the sub-scanning direction, and in this sense, the configuration of the second means is significant.

In the present invention, with the above-described configuration and effects, a low-cost, simple configuration, high-density, high-speed support, and a plurality of beams can acquire a stable small beam spot regardless of temperature fluctuations. It is possible to realize an optical scanning device that can stably acquire the scanning line interval between the beams and that has a small difference in the amount of light between the multiple beams.
In the image forming apparatus of the seventh means, an image forming apparatus compatible with high density and high speed can be realized by performing image formation using the optical scanning apparatus having the above-described configuration and effects.
Further, in the image forming apparatus of the eighth means, by forming a multi-color image using the optical scanning device having the above-described configuration and effect, an image forming apparatus capable of high-density and high-speed and compatible with multi-color can be obtained. Can be realized.

[Embodiment 1]
Hereinafter, the configuration, operation, and effects of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram showing a basic configuration example of an optical scanning device according to the present invention. An optical system constituting the optical scanning device passes through an optical axis in a main scanning direction (a deflection scanning direction by a deflecting unit). It is the figure expanded and shown on the parallel plane (it is called a main scanning plane or a main scanning cross section).
In FIG. 1, reference numeral 1 denotes a surface emitting semiconductor laser array (LD array) in which a plurality of light emitting elements are two-dimensionally arranged, 2 is a coupling lens, 3 is an aperture (opening), and 4 is anamorphic. Lens 5 is a polygon mirror of a deflector (polygon scanner) as a deflecting means (only one deflecting reflection surface of the polygon mirror is shown in the figure), 6 is a deflector side scanning lens, and 7 is an image surface side scan. A lens, 8 is dustproof glass, 9 is an image plane (scanned surface), 10 is soundproof glass, and 11 is a dummy mirror.

  The light beam emitted from the light source 1 becomes weakly divergent light by the coupling lens 2, passes through the aperture 3, and becomes parallel light in the main scanning direction by the anamorphic lens 4 and converges near the polygon mirror 5 in the sub-scanning direction. Further, the light is deflected by the polygon mirror 5 and formed on the image surface 9 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 provided between the polygon mirror 5 of the deflector and the deflector-side scanning lens 6. The light source 1 and the coupling lens 2 are fixed to the same holding member (not shown) made of aluminum.

(Description of surface emitting laser)
A surface-emitting LD array used as the light source 1 of the optical scanning device having the configuration shown in FIG. 1 is a surface-emitting laser having a wavelength of 780 nm band using a current confinement structure in which an AlAs layer is selectively oxidized, for example. The wavelength can be selected in accordance with the sensitivity characteristics of the photoconductor of the image forming apparatus. FIG. 3 shows a schematic diagram of a cross-sectional structure of a light emitting element (surface emitting laser element) constituting the surface emitting LD array. FIG. 4 shows an enlarged view around the active layer (A portion in the drawing) of the element of FIG.

The surface emitting laser element having a cross-sectional structure as shown in FIG. 3 can be manufactured as follows.
First, an active layer composed of an Al _0.12 Ga _0.88 As quantum well layer / Al _0.3 Ga _0.7 As barrier layer is formed on an n-GaAs substrate, and an Al _0.6 Ga _0.4 As spacer is formed. A resonator region having a one-wavelength optical thickness composed of layers is formed by 40.5 pairs of n-Al _0.3 Ga _0.7 As high-refractive index layers / n-Al _{0. 9} Ga _0.1 as and a lower reflector formed of a low refractive index layer, _p-Al 0.3 _{Ga 0.7} as high refractive index layer 24 pairs _{/ p-Al} 0.9 _{Ga 0.1} as low refractive index The structure is sandwiched between upper reflecting mirrors composed of layers. Further, an AlAs selectively oxidized layer is provided on the upper reflecting mirror 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. A well-known MOCVD method or MBE method can be used for the crystal growth.

Next, a mesa shape is formed by dry etching. In general, the etching surface reaches the lower reflecting mirror. Then, the AlAs selectively oxidized layer side is exposed through an etching process to oxidize the surrounding is heat-treated in water vapor, instead of the insulating layer of Al _X O _Y, optionally oxidized in the center of the path of the device operation current A current confinement structure is formed that restricts only to a non-AlAs region. Subsequently, an SiO ₂ protective layer (not shown) is provided, and the etching portion is further buried and flattened with polyimide, and the polyimide and the SiO ₂ protective layer (not shown) on the upper reflecting mirror having the p contact layer and the light emitting portion are provided. ), A p-side individual electrode was formed in addition to the light emitting portion on the p-contact layer, and an n-side common electrode was formed on the back surface.

  In the case of the present embodiment, the mesa portion formed by the dry etching method becomes each emitting element (surface emitting laser element). The method of forming the two-dimensional 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 the width of the groove is too narrow, it becomes difficult to control the 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, it is preferable that the size (diameter and the like) of the mesa portion is about 10 μm or more. This is because if the mesa portion is too small, heat is accumulated during the operation of the element, and the characteristics are deteriorated.

  The array arrangement of the light emitting elements of the light source 1 of the present embodiment is, for example, a 4 × 8 array of 4 rows and 8 columns as shown in FIG. 2 (the circular white portions in the figure are light emitting elements (light emitting points)). ). The interval between adjacent elements in the sub-scanning direction is set at an equal interval: d, and the positional relationship of the array in the sub-scanning direction is set at an equal interval: C2 = d / n. The distance between adjacent elements in the main scanning direction is equal to X. Specifically, d is 18.4 μm, X is 30 μm, and C2 = 2.3 μm.

When the element spacings d and X of the present embodiment are applied to the array arrangement of the conventional example of FIG. 12, C = d / n = 4.6 μm, so that the sub-center from the element center of the array of the present embodiment shown in FIG. The distance C2 between the elements in the sub-scanning direction when the vertical line is lowered in the scanning direction is 50% of C in FIG. 12, and even if the element spacing in the plane is the same, the density becomes high according to the present invention. I understand. 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 surface-emitting laser element in the 780 nm band can be manufactured using another material. FIG. 5 shows an enlarged view around the active layer of the device. As shown in FIG. 5, the active layer is composed of three GaInPAs quantum well active layers having a compressive strain composition and a band gap wavelength of 780 nm, and Ga _0.6 In ₀ having four layers of lattice-matched tensile strain. _.4 P barrier layer, and a clad layer (a spacer layer in this embodiment) for confining electrons, which 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. The rest of the structure is the same as that shown in FIG.

  Table 1 below shows an AlGaAs (spacer layer) / AlGaAs (quantum well active layer) system 780 nm, 850 nm surface emitting semiconductor laser, and an AlGaInP (spacer layer) / GaInPAs (quantum well active layer) system 780 nm surface emitting type. The band gap difference between the spacer layer and the well layer and the barrier layer and the well layer in the typical material composition of the semiconductor laser 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) 780 nm surface emitting semiconductor laser, the AlGaAs / AlGaAs 780 nm surface emitting semiconductor laser as well as the AlGaAs / AlGaAs 850 nm surface 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 with a low threshold. This effect cannot be obtained with a surface-emitting laser of 780 nm or 850 nm manufactured by 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 the present 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. As a result, the writing unit or the light source unit can be reused.

(Explanation of first and fourth means)
As shown in FIG. 12, the conventional two-dimensional array of surface emitting laser arrays has four columns in the main scanning direction and eight rows in the sub-scanning direction. Therefore, the distance between the most peripheral light emitting elements in the main scanning direction is
(N−1) × X = 3X (n = 4)
And the distance between the light emitting elements at the outermost periphery in the sub-scanning direction is
(M−1) × d = 7d (m = 8)
And
7d> 3X
It becomes. At this time, the pitch of the scanning line interval on the surface to be scanned is | βs | × d / 4, and it is difficult to obtain a desired pitch in the case of high density correspondence. For example, in the case of 2400 dpi,
25.4 mm / 2400 = 10.6 μm
In the case of 4800 dpi,
25.4 mm / 4800 = 5.3 μm
However, it is necessary to make | βs | × d / n equal to this value.

One means for achieving this is illustrated in FIG. FIG. 2 is a schematic plan view showing the arrangement of the light emitting elements of the surface emitting laser array of the present invention, in which the main scanning direction pitch X is longer than the sub scanning direction pitch d, and the number of arrangements in the main scanning direction and the sub scanning direction. This is an example of when is different. As shown in FIG. 2, the arrangement is 8 columns in the main scanning direction and 4 rows in the sub-scanning direction. Therefore, 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
It becomes.
Therefore, the distance between the most peripheral light emitting elements in the main scanning direction is longer than the distance between the most peripheral light emitting elements 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. In other words, if the distance between the light emitting elements at the outermost periphery in the main scanning direction is made longer than the distance between the light emitting elements at the outermost periphery in the sub scanning direction, it becomes easy to cope with high density.
Further, the absolute value | βs | of the horizontal magnification in the sub-scanning direction of the entire optical system is made smaller than the absolute value | βm | of the horizontal magnification in the main scanning direction (| βm |> | βs |). The pitch on the scanning surface can be reduced, and it becomes easy to cope with high density.
Although a method of making the distance between the most peripheral light emitting elements in the main scanning direction shorter than the distance between the most peripheral light emitting elements in the sub-scanning direction and reducing | βs | Since the above-mentioned various problems occur, it is not preferable.

(Explanation of the fifth means)
In the fifth means, in addition to the configuration of the first or fourth means, the light source 1 in which a plurality of light emitting elements are arranged two-dimensionally includes m light emitting elements one-dimensionally in the sub-scanning direction (FIG. 2). In the example, m = 4) and n one-dimensional columns in the sub-scanning direction are arranged substantially in the main scanning direction (n = 8 in the example of FIG. 2), and m × n light emitting elements. The configuration is such that the positional relationship of each light emitting element in the sub-scanning direction when the perpendicular is lowered from (m ≦ n) to a straight line parallel to the sub-scanning direction is an equal interval. By defining the relationship between the number of columns and the number of rows of light emitting elements, the same effect as described above can be obtained.

(Explanation of sixth means)
As described above, how to reduce the scanning line interval on the surface to be scanned is a big problem. In the optical scanning device of the sixth means, in addition to the configuration of the fifth means, a plurality of light emitting elements are provided. The two-dimensionally arranged light source has a one-dimensional array of m light emitting elements in the sub-scanning direction as d, and an array pitch of n arrays in the main scanning direction as X.
X> d
As a result, the element spacing in the main scanning direction, which does not affect the increase in density in the sub-scanning direction, is widened, and it is necessary to reduce the influence of thermal interference between elements and to pass the wiring of each element. Space can be secured.

(Explanation of the first means)
In the optical scanning device of the first means , the first optical system includes a coupling lens 2 that couples a plurality of light beams emitted from a light source, and a plurality of light beams emitted from the coupling lens 2. On the other hand, it has an opening (for example, aperture) 3 that restricts at least the light beam in the main scanning direction, and the opening 3 is disposed closer to the deflecting means (for example, polygon mirror) 5 than the rear focal position of the coupling lens 2. It is set as the structure made.

Hereinafter, a description will be given with reference to FIGS. Both figures show the arrangement of the optical system in the main scanning section.
FIG. 6A is an explanatory diagram when the aperture 3 is arranged at the rear focal position of the coupling lens 2. When the first to fourth means are employed, the distance between the light emitting elements at the outermost periphery in the main scanning direction is increased. At this time, if the aperture 3 for limiting the beam in the main scanning direction is arranged at the rear focal position of the coupling lens 2, the beam is separated on the polygon mirror surface as shown in the drawing, and in particular, the optical characteristics of the outermost beam. The characteristics will deteriorate. In this configuration, the most important characteristic is to obtain a desired scanning line interval on the surface to be scanned. Even if the aperture 3 is disposed at the rear focal position of the coupling lens 2, high image quality, high density, and high speed are achieved. Although a corresponding optical scanning device is used, in order to further improve the beam spot diameter characteristics of main scanning and sub scanning, the configuration shown in FIG. That is, the aperture 3 is arranged closer to the deflecting means (polygon mirror) 5 than the rear focal position of the coupling lens 2. At this time, the distance between the center lines of the most peripheral beams on the polygon mirror surface is shortened, and the field curvature of the main scanning and the sub scanning can be improved, and both the main scanning and the sub scanning are good. A beam spot diameter can be obtained.

(Explanation of the third means)
In the optical scanning device of the third means, in addition to the above configuration, at least one of the most peripheral light emitting elements out of the two-dimensionally arranged light emitting elements has a larger light emission amount than the light emitting elements other than the most peripheral light emitting element. Thus, it is possible to suppress a decrease in the light amount of the most peripheral beam. That is, as shown in FIG. 7, when the light source 1 in which a plurality of light emitting elements are arranged in a two-dimensional manner is used, the center of the aperture 3 and the center of the beam of the light beam at the outermost periphery do not coincide with each other. The light utilization efficiency of this beam is lower than that of the central beam. Therefore, by increasing the light emission amount of the most peripheral light emitting element and setting the light amount of the most peripheral beam high, it is possible to realize an optical scanning device having no density unevenness.

(Explanation of the second means)
In the optical scanning device of the second means, in addition to the above-described configuration, the first optical system includes a coupling lens 2 that couples a plurality of light beams emitted from the light source 1, and the coupling lens 2. An opening (for example, an aperture) 3 that restricts light beams in the main scanning direction and the sub-scanning direction is provided for a plurality of emitted light beams, and the width of the aperture 3 in the main scanning direction is larger than the width in the sub-scanning direction. Thus, the variation in the amount of light can be reduced.

Here, in the configurations of the fourth to sixth means, the optical axis deviation amount of the most peripheral beam from the coupling lens 2 is larger in the main scanning direction than in the sub scanning direction. However, when the aperture diameter for restricting the beam is larger in the sub-scanning direction than in the main scanning direction, the light amount variation becomes large. 8A and 8B, the amount of optical axis deviation from the coupling lens is the same for both the main scanning and the sub scanning, and the aperture diameter in the main scanning direction (the main aperture diameter in FIG. 8B) is the sub scanning direction. Is larger than the aperture diameter (sub-aperture diameter in FIG. 8A). As can be seen from FIG. 8, at this time, the larger the aperture diameter, the smaller the light quantity change rate with respect to the optical axis deviation. I understand that. 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. In order to make the horizontal magnification in the sub-scanning direction smaller than the horizontal magnification in the main scanning direction,
It is necessary to increase the aperture diameter in the main scanning direction / the aperture diameter in the sub-scanning direction, and in this sense, the configuration of the second means is significant.

[Embodiment 2]
Next, FIG. 9 shows a configuration example of an image forming apparatus using the optical scanning device according to the present invention. The image forming apparatus shown in FIG. 9 has a photosensitive drum 111 formed in a cylindrical shape as an image bearing member, and a charging device 112 (charging roller in the figure) for uniformly charging the surface of the photosensitive member around the photosensitive drum 111. In addition, a charging brush, a non-contact type corona charger, etc. can also be used.) Light that irradiates the photosensitive drum with a light beam to form an electrostatic latent image A scanning device 113; a developing device 114 that develops the electrostatic latent image on the photosensitive drum with toner; and a transfer device 115 that transfers the toner image visualized on the photosensitive drum by development onto the sheet-like recording medium S Although a transfer roller is shown in the figure, a corona charger or the like may be used), and it has a cleaning device 116 that removes transfer residual toner after transfer. Reference numeral 117 denotes a fixing device.

The photosensitive drum 111 is provided with a photosensitive layer made of a photoconductive photosensitive material that becomes a dielectric when exposed to light, in the dark, on the outer surface of a conductive cylinder such as a grounded metal. Yes.
The photosensitive drum 111 is rotated at a constant speed in the direction of the arrow in the figure, and the charging device 112 uniformly charges the surface of the photosensitive drum.

  Next, a light beam whose intensity is modulated in accordance with image information is irradiated onto a part of the photosensitive drum 111 by the optical scanning device 113. The portion of the photosensitive drum 111 exposed to the light beam becomes a conductor, and the charge on the surface of the photosensitive member is eliminated by the escape of the charge on the surface of the photosensitive member through the conductive cylinder. In addition, the charge of the portion where the light beam has not been exposed is maintained as it is. In this way, an electrostatic latent image is formed on the surface of the photoreceptor.

Next, the toner charged to the same polarity as the surface of the photoreceptor by the developing device 114 adheres only to the portion where the charge on the surface of the photoreceptor disappears, and is visualized as a toner image.
The toner image on the photoreceptor is transferred by electrostatic force and pressure by the transfer device 114 onto a sheet-like recording medium S such as a recording sheet or an OHP sheet fed from a sheet feeding unit (not shown). The toner image transferred onto the sheet-like recording medium S is fixed by applying heat and pressure by the fixing device 117. Then, the sheet-like recording medium S on which the toner image is fixed is discharged to a paper discharge unit (not shown) outside the apparatus. Further, the photoreceptor 111 after the toner image transfer is cleaned by a cleaning member (blade, brush, etc.) of the cleaning device 116 to remove residual toner and paper dust.

  As described above, in the image forming apparatus having the configuration shown in FIG. 9, image formation is performed through the steps of charging → exposure → development → transfer → fixing → cleaning. By using the described optical scanning device of the present invention, a high-density and high-speed compatible image forming apparatus can be realized.

[Embodiment 3]
FIG. 10 shows an example of the configuration of a multi-color image forming apparatus using the optical scanning device according to the present invention. Reference numerals 111Y, 111M, 111C, and 111K in the figure are photosensitive drums arranged in parallel along the transfer belt 118, and are rotated in the direction of the arrow in the figure. Around the photosensitive drums 111Y, 111M, 111C, and 111K, as in FIG. 9, charging devices 112Y, 112M, 112C, and 112K (in the drawing, contact type using charging rollers are shown, but in addition, Charging brush, non-contact type corona charger, etc.), optical scanning device 113, developing devices 114Y, 114M, 114C, 114K for each color, transfer device (transfer charger, transfer roller, transfer brush, etc.) 115Y, 115M, 115C, 115K and cleaning devices 116Y, 116M, 116C, 116K are provided. In the figure, reference numeral 117 denotes a fixing device, 119 denotes a paper feeding cassette on which a sheet-like recording medium S such as recording paper is stacked, 120 denotes a paper feeding roller, 121 denotes a separation roller, 122 denotes a conveyance roller, and 123 denotes a registration roller. Show.

  The photosensitive drums 111Y, 111M, 111C, and 111K are exposed to a light beam that has been intensity-modulated in accordance with image information by an optical scanning device 113, which is a latent image forming unit, to form an electrostatic latent image. The basic configuration of the optical scanning device 113 that performs this exposure process is as described in the first embodiment, and four optical scanning devices may be arranged corresponding to the photosensitive drums 111Y, 111M, 111C, and 111K. In the example of FIG. 10, the configuration is such that four multi-beams are distributed and scanned by one deflecting means. That is, the optical scanning device shown in FIG. 10 includes four systems of multi-beam light sources and first and second optical systems for respectively corresponding to the four photosensitive drums 111Y, 111M, 111C, and 111K, and one deflection. The four multi-beams are divided and scanned by the means, and the optical path of each multi-beam is bent by the mirror provided in the second optical system and irradiated to each of the photosensitive drums 111Y, 111M, 111C, and 111K.

  The electrostatic latent images formed on the photosensitive drums 111Y, 111M, 111C, and 111K are yellow (Y) developing device 114Y, magenta (M) developing device 114M, cyan (C) developing device 114C, and black (K) developing. The image is developed by the device 114K and visualized as toner images of each color of yellow (Y), magenta (M), cyan (C), and black (K). Further, the sheet-like recording medium S is fed from the paper feed cassette 119 one by one by the paper feed roller 120 and the separation roller 121 in synchronization with this development process, and reaches the registration roller 123 through the transport roller 122. Then, the sheet-like recording medium S is transferred to the transfer belt 118 by the registration rollers 123 in accordance with the timing at which the toner images on the photosensitive drums 111Y, 111M, 111C, and 111K that have been visualized in the development process come to the transfer position. The sheet-like recording medium S is carried by the transfer belt 118 and is sequentially conveyed to the transfer positions of the respective colors. Then, a transfer bias is applied by the transfer devices 115Y, 115M, 115C, and 115K arranged to face the photosensitive drums 111Y, 111M, 111C, and 111K with the transfer belt 118 interposed therebetween, and the photosensitive drums 111Y, 111M, and 111K, respectively. The toner images of the respective colors on 111C and 111K are sequentially superimposed and transferred onto the sheet-like recording medium S. The four-color superimposed toner image (color image) transferred onto the sheet-like recording medium S is fixed by applying heat and pressure by the fixing device 117. Then, the sheet-like recording medium S on which the toner image is fixed is discharged to a paper discharge unit (not shown) outside the apparatus. The photosensitive drums 111Y, 111M, 111C, and 111K after the toner image transfer are cleaned by cleaning members (blades, brushes, etc.) of the cleaning devices 116Y, 116M, 116C, and 116K to remove residual toner and paper dust. .

  In the image forming apparatus shown in FIG. 10, a single color mode for forming an image of any one of yellow (Y), magenta (M), cyan (C), and black (K), yellow (Y), magenta ( M), Cyan (C), Black (K) Two-color mode that forms two colors of images, Yellow (Y), Magenta (M), Cyan (C), Black (K) It has a three-color mode in which three-color images are superimposed and a full-color mode in which a four-color superimposed image is formed as described above. Multicolor and full-color image formation is possible.

  Further, in the image forming apparatus having the configuration shown in FIG. 10, multicolor image formation is performed on the sheet-like recording medium S through the steps of charging → exposure → development → transfer in each color image forming unit. Instead of the method of transferring directly from the photosensitive drums 111Y, 111M, 111C, 111K to the sheet-like recording medium S, an intermediate transfer member such as an intermediate transfer belt is used, and the intermediate transfer members are transferred from the photosensitive drums 111Y, 111M, 111C, 111K. In addition, an intermediate transfer type image forming apparatus may be configured in which a primary transfer is performed to form an overlapped image of each color and then secondary transfer is performed collectively from the intermediate transfer member to the sheet-like recording medium S.

  As described above, in the multicolor image forming apparatus according to the present invention, a multicolor image is formed on the sheet-like recording medium S through the steps of charging → exposure → development → transfer in each color image forming unit. By using the optical scanning device of the present invention described in the first embodiment for the optical scanning device 113, it is possible to realize a high-density, high-speed compatible and multi-color compatible image forming apparatus.

Specific examples (optical system data) of the optical scanning device according to the present invention are shown below.
The arrangement of the optical system of the optical scanning device is the same as in FIG. The wavelength of each light emitting element of the light source 1 is 780 nm, and the plurality of light emitting elements are arranged two-dimensionally as shown in FIG.
The diameter of the light emitting region (circular white portion in FIG. 2) is 4 μm, and as described above, the array is 4 × 8, and the element interval (pitch) d in the sub-scanning direction is d = 18. The element spacing (pitch) X in the main scanning direction is 4 μm, and X = 30 μm.

The coupling lens 2 of the first optical system has a surface shape expressed by the following formula (1) on both the first surface and the second surface.
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 coefficients are A4, A6, A8, and A10, the respective coefficients are as follows. The refractive index is 1.5119.

(First side)
R = 98.97
K = −18.9
A4 = −2.748510E-06 (meaning E-06 = × 10 ⁻⁶ (the same applies hereinafter))
A6 = 7.513797E-07
A8 = −5.817478E-08
A10 = -2.475370E-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

Here, d1 in FIG. 1 is 42.39 mm, and a cover glass having a refractive index of 1.5112 and a thickness of 0.3 mm is inserted therebetween.
D2 = 3.8 mm.

The anamorphic lens 4 is a cylindrical surface having a first surface having power in the sub-scanning direction, and a second surface having a cylindrical surface having power in the main scanning direction. The sub-scanning radius of curvature of the first surface is 55 mm, and the main scanning radius of curvature of the second surface is -500 mm. Here, d3 = 117.2 mm and d4 = 3 mm in FIG.
The aperture 3 is disposed at a distance of 58.2 mm from the second surface of the anamorphic lens 4 to the deflection means side, and is disposed closer to the deflector (polygon mirror) 5 than the rear focal position of the coupling lens 2. Has been. Here, d5 = 120.2 mm. The aperture diameter is a rectangular shape with a main scanning direction of 5.5 mm and a sub-scanning direction of 1.18 mm.

At this time, a soundproof glass 10 having a wall thickness of 1.9 mm and a refractive index of 1.5112 is provided between the anamorphic lens 4 and the polygon mirror 5 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.
Further, in FIG. 1, d6 = 36.7 mm, d7 = 8 mm, d8 = 101.9 mm, d9 = 3 mm, d10 = 138.2 mm. Table 2 below shows optical system data after the optical deflector (polygon mirror) 5.

In the notation of Table 2, R _m is “paraxial curvature in the main scanning direction”, R _s is “paraxial curvature in the sub scanning direction”, and D represents the distance between the optical elements. The unit is mm. A dust-proof glass 8 is disposed between the scanning lens 7 and the scanned surface 9, and the dust-proof glass 8 has a refractive index of 1.5112 and a wall thickness of 1.9 mm.

Each surface of the deflector-side scanning lens 6 and the image plane-side scanning lens 7 constituting the second optical system is aspherical, and the entire surface is “a non-circular shape given by the following formula (2)” in the main scanning direction. Thus, the curvature in the sub-scanning section (virtual section parallel to the optical axis and the sub-scanning direction) is a special surface that “changes according to the following equation (3)” in the main scanning direction.
That is, the non-arc shape in the main scanning plane (virtual flat section including the lens optical axis and parallel to the main scanning direction) is a paraxial radius of curvature in the main scanning plane on the optical axis: R _m , the main scanning direction. The distance from the optical axis in Y: Y, the conic constant: K, and the higher order coefficients: A ₁ , A ₂ , A ₃ , A ₄ , A ₅ , A ₆ ,. Using X, polynomial:
X = (Y ² / Rm) / [1 + √ {1- (1 + K) (Y / Rm) ² }]
+ A ₁・ Y + A ₂・ Y ² + A ₃・ Y ³ + A ₄・ Y ⁴ + A ₅・ Y ⁵ + A ₆・ Y ⁶ + ... (2)
Represented by When one or more of odd-order coefficients: A ₁ , A ₃ , A ₅ ... Is not “0”, the non-circular arc shape given by Equation (2) is asymmetric in the main scanning direction.

[Change in curvature in sub-scan section]
The expression expressing the state in which the curvature in the sub-scanning section: C _s (Y) (Y: coordinates in the main scanning direction with the optical axis position as the origin) changes in the main scanning direction is in the sub-scanning section including the optical axis. Are as follows, with R _s (0), B ₁ , B ₂ , B ₃ ,... As coefficients.
Cs (Y) = {1 / Rs (0)} + B 1 · Y + B 2 · Y 2 + B 3 · Y 3 + B 4 · Y 4 + B 5 · Y 5 + ··· (3)
When one or more of the odd-order coefficients B ₁ , B ₃ , B ₅ ... Is not “0”, the “curvature in the sub-scanning section” given by the equation (3) changes asymmetrically in the main scanning direction.

  The coefficients of the first surface (incident side surface (special surface)) of the scanning lens 6 are shown in Table 3 below. Further, the coefficients of the second surface (exit side surface (special surface)) of the scanning lens 6 are shown in Table 4 below. Further, the coefficients of the first surface (incident side surface (special surface)) of the scanning lens 7 are shown in Table 5 below. Table 6 below shows coefficients of the second surface (exit side surface (special surface)) of the scanning lens 7.

FIG. 11 shows aberration diagrams in the optical scanning device of the present embodiment. The aberrations are corrected favorably. Further, the beam spot diameter on the scanned surface (image surface) 9 is as shown in Table 7 below, and is corrected well.
At this time, the absolute value of the horizontal magnification in the main scanning direction is | βm | = 4.9, the absolute value of the horizontal magnification in the sub-scanning direction is | βs | = 2.3, and the scanning surface is scanned with 5.3 μm. The line spacing can be obtained, and the present invention can be applied to a high-density and high-speed image forming apparatus as a high-density optical scanning apparatus of 4800 dpi.

1 is a diagram illustrating an embodiment of the present invention, and is a schematic configuration diagram illustrating a basic configuration example of an optical scanning device. It is a schematic plan view which shows the example of arrangement | positioning of the light emitting element of the surface emitting laser array which concerns on this invention. It is sectional drawing which shows the outline of the cross-sectional structure of the light emitting element (surface emitting laser element) which comprises a surface emitting LD array. FIG. 4 is an enlarged view of a main part around an active layer (A part in the drawing) of the light emitting device of FIG. 3. It is a principal part enlarged view of the active layer periphery which shows another example of the cross-sectional structure of a light emitting element. It is explanatory drawing which shows the relationship between the arrangement position of a coupling lens and an aperture in the optical scanning device of this invention. It is a figure which shows the position shift with respect to the center of an aperture of the beam from a center light emitting element, and the beam from the most peripheral light emitting element at the time of using the light source which arranged the several light emitting element in the two-dimensional form. It is a figure which shows the case where the amount of optical axis deviations from a coupling lens is the same in both main scanning and sub scanning, and the aperture diameter in the main scanning direction is larger than the aperture diameter in the sub scanning direction. 1 is a schematic configuration diagram illustrating a configuration example of an image forming apparatus according to the present invention. 1 is a schematic configuration diagram illustrating a configuration example of a multicolor image forming apparatus according to the present invention. It is an aberration diagram in the optical scanning device of the embodiment of the present invention. It is a schematic plan view which shows the example of arrangement | positioning of the light emitting element of the conventional surface emitting laser array.

Explanation of symbols

1: Light source (surface emitting laser array)
2: Coupling lens 3: Aperture (opening)
4: Anamorphic lens 5: Polygon mirror (deflection means)
6: Deflector scanning lens 7: Image surface scanning lens 8: Dust-proof glass 9: Image surface (scanned surface)
10: Soundproof glass 11: Dummy mirror 111, 111Y, 111M, 111C, 111K: Photosensitive drum 112, 112Y, 112M, 112C, 112K: Charging device 113: Optical scanning device 114, 114Y, 114M, 114C, 114K: Developing device 115, 115Y, 115M, 115C, 115K: transfer device 116, 116Y, 116M, 116C, 116K: cleaning device 117: fixing device 118: transfer belt 119: paper feed cassette 120: paper feed roller 121: separation roller 122: transport roller 123: Registration roller S: Sheet-shaped recording medium

Claims (8)

A light source in which a plurality of light emitting elements are arranged two-dimensionally;
A first optical system for guiding a plurality of light beams from the light source to a deflecting means;
A second optical system for guiding a plurality of light beams from the deflecting means to a scanned surface;
When the scanning direction by the deflecting means is the main scanning direction, and the direction perpendicular to the optical axis of the main scanning direction and the first and second optical systems is the sub-scanning direction, between the light emitting elements at the outermost periphery in the main scanning direction The first optical system includes a coupling lens that couples a plurality of light beams emitted from the light source, and the cup. An opening that restricts at least a light beam in the main scanning direction with respect to the plurality of light beams emitted from the ring lens, and the opening is closer to the deflecting unit than a rear focal position of the coupling lens. optical scanning device characterized in that it is deployed. 2. The optical scanning device according to claim 1, wherein the opening restricts a light flux in a main scanning direction and a sub scanning direction, and a width of the opening in the main scanning direction is larger than a width in the sub scanning direction. Optical scanning device.   3. The optical scanning device according to claim 2, wherein at least one of the light emitting elements arranged in the two-dimensional array has a larger light emission amount than light emitting elements other than the light emitting element other than the light emitting element. Optical scanning device. In the optical scanning device according to any one of claims 1 to 3,
When the lateral magnification in the main scanning direction of the optical system between the light source and the scanned surface is βm, and the lateral magnification in the sub-scanning direction of the optical system between the light source and the scanned surface is βs,
| Βm |> | βs |
An optical scanning device characterized by satisfying the following condition. The optical scanning device according to any one of claims 1 to 4,
In the light source in which the plurality of light emitting elements are arranged in a two-dimensional manner, each light emitting element is arranged one-dimensionally in the sub-scanning direction (m ≧ 2), and further, a one-dimensional row in the sub-scanning direction. Are arranged approximately in the main scanning direction (n ≧ 2),
In addition, the positional relationship of the light emitting elements in the sub-scanning direction when the perpendicular is lowered from the m × n light-emitting elements (m ≦ n) to the straight line parallel to the sub-scanning direction is equally spaced. Optical scanning device. In the optical scanning device according to any one of claims 1 to 5,
The light source in which the plurality of light emitting elements are arranged in a two-dimensional manner has an arrangement pitch of light emitting elements in a one-dimensional array of m in the sub-scanning direction, d, and an arrangement pitch of n arrays in the main scanning direction. When X is
X> d
An optical scanning device characterized by that. A photosensitive drum as an image carrier, a charging device that uniformly charges the surface of the photosensitive member, an optical scanning device that forms an electrostatic latent image by irradiating the photosensitive drum with a light beam, and developing the electrostatic latent image with toner 7. An image forming apparatus comprising a developing device and a transfer device for transferring to a recording medium, wherein the image forming apparatus performs image formation using the optical scanning device according to claim 1. The image forming apparatus according to claim 7, wherein at least the photosensitive drum and the charging device are arranged in parallel, and the developing device includes a multicolor developing device. An image forming apparatus for forming a multicolor image using the optical scanning apparatus of No. 1.

Images