JP5582460B2 - Surface emitting laser array, optical scanning device, and image forming apparatus - Google Patents

Description

  The present invention relates to a surface emitting laser array, an optical scanning device, and an image forming apparatus. More specifically, the present invention relates to a surface emitting laser array in which a plurality of surface emitting lasers are two-dimensionally arranged, and an optical scanning device having the surface emitting laser array. And an image forming apparatus.

  In electrophotographic image recording, an image forming method using laser light 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 laser light (main scanning) using a polygon mirror in the axial direction of a photosensitive drum is used. It is.

  In such an electrophotographic field, higher definition of images and higher speed of output are required. In order to increase the definition of an image, when the resolution of the image is doubled, twice the time is required for both main scanning and sub-scanning. Therefore, four times the time is required for image output. Therefore, in order to achieve high definition of images, it is necessary to simultaneously achieve high speed image output.

  As a method for realizing high-speed image output, it is conceivable to increase the output of the laser, increase the number of beams, increase the sensitivity of the photosensitive member, and the like. In particular, in a high-speed output machine, it is common to use a multi-beam writing light source (multi-beam light source). Compared with the case of using one laser beam, when n laser beams are used at the same time, the latent image forming area in one scanning is n times, and the time required for image formation is 1 / n. Become.

  For example, Patent Document 1 discloses a photoelectric conversion element including a plurality of photoelectric conversion units on the same substrate. Patent Document 2 discloses a semiconductor light emitting element including a plurality of light emitting portions on the same substrate. Each element disclosed in Patent Document 1 and Patent Document 2 has a configuration in which a plurality of edge-emitting semiconductor lasers are arranged one-dimensionally. In these cases, the power consumption increases as the number of beams increases, and a new cooling system is required. Therefore, the cost is limited to about 4 beams or 8 beams.

  On the other hand, a surface emitting laser that has been actively studied in recent years can easily integrate a plurality of surface emitting lasers two-dimensionally. In addition, the surface-emitting laser consumes about one digit less power than the edge-type laser, and is advantageous for integrating many surface-emitting lasers two-dimensionally.

  For example, Patent Document 3 discloses an electrophotographic photosensitive member, a charging device that charges the electrophotographic photosensitive member, an exposure device that exposes the charged electrophotographic photosensitive member to form an electrostatic latent image, and an electrostatic latent image. An image forming apparatus comprising: a developing device that develops toner with toner to form a toner image; and a transfer device that transfers the toner image from the electrophotographic photosensitive member to a transfer medium. A multi-beam type exposure apparatus that forms an electrostatic latent image by scanning three or more light beams on the electrophotographic photosensitive member, and the electrophotographic photosensitive member is provided on the conductive substrate and the substrate. An image forming apparatus is disclosed in which the photosensitive layer includes a photoconductive layer containing an amorphous silicon-containing compound.

  Patent Document 4 has a plurality of light sources that generate light beams for scanning the surface to be scanned and light source driving means for driving them, and the light source driving means is adjacent to the surface to be scanned. Two sets of light sources corresponding to two scanning lines are set as one set, and one of the sets of light sources is set as a main light source and the other is set as a sub-light source, without changing the total light amount of the set of light sources, and By changing the light amount ratio between the main light source and the sub light source without causing the light amount of the sub light source to exceed the light amount of the main light source, the light beam generated from one set of light sources in the sub scanning direction on the surface to be scanned An optical scanning device for controlling the light amount distribution is disclosed.

  In Patent Document 5, a plurality of light beams emitted from a light source having three or more light emitting points are subjected to main scanning by deflecting and scanning the surface to be scanned by an optical deflector, and orthogonal to the main scanning direction. An optical scanning device that performs sub-scanning by relatively moving a surface to be scanned in a direction, and when each of a plurality of light emitting points of a light source is sequentially set as a target light emitting point, surrounding light emitting points adjacent to the target light emitting point The light emitting points are arranged two-dimensionally so that all the distances between them are equally spaced, and each of the light sources is scanned so that each scanning line by a plurality of light beams scans the surface to be scanned at regular intervals. An optical scanning device is disclosed in which the light emitting points are arranged by being rotated by a predetermined angle with respect to the main scanning direction or the sub scanning direction in the same plane.

  By the way, in the surface emitting laser array, when the interval between the adjacent light emitting units becomes narrow, there is a possibility that the output may be lowered or the reliability may be lowered due to the heat generated in the other light emitting units.

  The present invention has been made under such circumstances, and a first object of the present invention is to provide a surface emitting laser array that is less affected by thermal interference without causing an increase in size.

  A second object of the present invention is to provide an optical scanning device capable of scanning a surface to be scanned at high density and high speed.

  A third object of the present invention is to provide an image forming apparatus capable of forming a high-definition image at high speed.

According to a first aspect of the present invention, in the surface emitting laser array in which a plurality of light emitting units are two-dimensionally arranged, the plurality of light emitting units are orthogonally projected onto a virtual line extending in one direction. The interval on the line is a natural number multiple of a predetermined value, and the plurality of light emitting units includes a first light emitting unit, a second light emitting unit adjacent to the first light emitting unit when orthogonally projected, A third light-emitting part adjacent to the second light-emitting part when orthogonally projected, and the distance between the first light-emitting part and the second light-emitting part in the one direction is the second light-emitting part Unlike the interval between the light emitting unit and the third light emitting unit, the number of the plurality of light emitting units is an even number.

  In the present specification, the “light emitting portion interval” refers to the distance between the centers of two light emitting portions.

According to this, when the plurality of light emitting units are orthogonally projected onto the virtual line extending in one direction, the interval on the virtual line is a natural number multiple of the predetermined value. The plurality of light emitting units include a first light emitting unit, a second light emitting unit adjacent to the first light emitting unit when orthographically projected, and a third light emitting unit adjacent to the second light emitting unit when orthographically projected. With respect to one direction, the interval between the first light emitting unit and the second light emitting unit is different from the interval between the second light emitting unit and the third light emitting unit. In this case, even if the size is not increased so much, it is possible to widen the interval between the light emitting portions in the region that is more influenced by other light emitting portions. Therefore, the influence of thermal interference can be made smaller than before without increasing the size.

  According to a second aspect of the present invention, there is provided an optical scanning device that scans a surface to be scanned with light, including the surface emitting laser array of the present invention, wherein one direction of the surface emitting laser array is a sub-scanning direction. A light source unit that coincides with a direction corresponding to the light source unit; a deflector that deflects light from the light source unit; and a scanning optical system that condenses the light deflected by the deflector onto the surface to be scanned. An optical scanning device provided.

  According to this, since the surface emitting laser array of the present invention is provided, as a result, it becomes possible to scan the surface to be scanned at high density and at high speed.

  According to a third aspect of the present invention, there is provided an image comprising: at least one photosensitive member; and at least one optical scanning device according to the present invention that scans the at least one photosensitive member with light including image information. Forming device.

  According to this, since at least one optical scanning device of the present invention is provided, as a result, a high-definition image can be formed at high speed.

  From a fourth viewpoint, the present invention is an image forming apparatus including the surface emitting laser array of the present invention as a writing light source when writing image information on a photosensitive member.

  According to this, since the surface emitting laser array of the present invention is provided, as a result, a high-definition image can be formed at high speed.

It is a figure for demonstrating schematic structure of the laser printer which concerns on one Embodiment of this invention. It is the schematic which shows the optical scanning device in FIG. FIG. 3 is a diagram (No. 1) for explaining a surface emitting laser array included in a light source in FIG. 2; FIG. 3 is a diagram (part 2) for explaining a surface emitting laser array included in the light source in FIG. 2; It is FIG. (1) for demonstrating the comparative example of a surface emitting laser array. It is FIG. (2) for demonstrating the comparative example of a surface emitting laser array. It is a figure for demonstrating non-uniform interlaced scanning when the surface emitting laser array of FIG. 3 is used. It is a figure for demonstrating the modification 1 of a surface emitting laser array. FIG. 8 is a diagram for explaining unequal interlaced scanning when the surface emitting laser array of FIG. 7 is used. FIG. 5 is a diagram (part 1) for explaining the merit of an uneven interlaced scanning arrangement over an even interlaced scanning arrangement; FIG. 6 is a diagram (part 2) for explaining the merits of an unequal interlaced scanning arrangement over an even interlaced scanning arrangement; FIG. 10 is a diagram (No. 3) for explaining an advantage of an unequal interlaced scanning arrangement over an even interlaced scanning arrangement; FIG. 14 is a diagram (No. 4) for explaining a merit of the uniform interlaced scanning arrangement over the uniform interlaced scanning arrangement; It is a figure for demonstrating the modification 2 of a surface emitting laser array. FIG. 14 is a diagram for explaining unequal interlaced scanning when the surface emitting laser array of FIG. 13 is used. It is a figure for demonstrating the modification 3 of a surface emitting laser array. FIG. 16 is a diagram for explaining unequal interlaced scanning when the surface emitting laser array of FIG. 15 is used. It is a figure for demonstrating the modification 4 of a surface emitting laser array. It is a figure for demonstrating the modification 5 of a surface emitting laser array. It is a figure which shows schematic structure of a tandem color machine.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a laser printer 1000 as an image forming apparatus according to an embodiment of the present invention.

  The laser printer 1000 includes an optical scanning device 1010, a photosensitive drum 1030, a charging charger 1031, a developing roller 1032, a transfer charger 1033, a static elimination unit 1034, a cleaning blade 1035, a toner cartridge 1036, a paper supply roller 1037, a paper supply tray 1038, A registration roller pair 1039, a fixing roller 1041, a paper discharge roller 1042, a paper discharge tray 1043, and the like are provided.

  A photosensitive layer is formed on the surface of the photosensitive drum 1030. That is, the surface of the photoconductor drum 1030 is a scanned surface. Here, the photosensitive drum 1030 rotates in the direction of the arrow in FIG.

  The charging charger 1031, the developing roller 1032, the transfer charger 1033, the charge removal unit 1034, and the cleaning blade 1035 are each arranged in the vicinity of the surface of the photosensitive drum 1030. Then, along the rotation direction of the photosensitive drum 1030, the charging charger 1031 → the developing roller 1032 → the transfer charger 1033 → the discharging unit 1034 → the cleaning blade 1035 are arranged in this order.

  The charging charger 1031 uniformly charges the surface of the photosensitive drum 1030.

  The optical scanning device 1010 irradiates the surface of the photosensitive drum 1030 charged by the charging charger 1031 with light modulated based on image information from a host device (for example, a personal computer). As a result, a latent image corresponding to the image information is formed on the surface of the photosensitive drum 1030. The latent image formed here moves in the direction of the developing roller 1032 as the photosensitive drum 1030 rotates. The configuration of the optical scanning device 1010 will be described later.

  The toner cartridge 1036 stores toner, and the toner is supplied to the developing roller 1032.

  The developing roller 1032 causes the toner supplied from the toner cartridge 1036 to adhere to the latent image formed on the surface of the photosensitive drum 1030 to visualize the image information. Here, the latent image to which the toner is attached (hereinafter also referred to as “toner image” for the sake of convenience) moves in the direction of the transfer charger 1033 as the photosensitive drum 1030 rotates.

  Recording paper 1040 is stored in the paper feed tray 1038. A paper feed roller 1037 is disposed in the vicinity of the paper feed tray 1038, and the paper feed roller 1037 takes out the recording paper 1040 one by one from the paper feed tray 1038 and conveys it to the registration roller pair 1039. The registration roller pair 1039 temporarily holds the recording paper 1040 taken out by the paper supply roller 1037, and in the gap between the photosensitive drum 1030 and the transfer charger 1033 according to the rotation of the photosensitive drum 1030. Send it out.

  A voltage having a polarity opposite to that of the toner is applied to the transfer charger 1033 in order to electrically attract the toner on the surface of the photosensitive drum 1030 to the recording paper 1040. With this voltage, the toner image on the surface of the photosensitive drum 1030 is transferred to the recording paper 1040. The recording sheet 1040 transferred here is sent to the fixing roller 1041.

  In the fixing roller 1041, heat and pressure are applied to the recording paper 1040, whereby the toner is fixed on the recording paper 1040. The recording paper 1040 fixed here is sent to the paper discharge tray 1043 via the paper discharge roller 1042 and is sequentially stacked on the paper discharge tray 1043.

  The neutralization unit 1034 neutralizes the surface of the photosensitive drum 1030.

  The cleaning blade 1035 removes toner (residual toner) remaining on the surface of the photosensitive drum 1030. The surface of the photosensitive drum 1030 from which the residual toner has been removed returns to the position facing the charging charger 1031 again.

  Next, the configuration of the optical scanning device 1010 will be described.

  As shown in FIG. 2 as an example, the optical scanning device 1010 includes a light source 14, a coupling lens 15, an aperture plate 16, a cylindrical lens 17, a polygon mirror 13, a deflector side scanning lens 11a, and an image plane side scanning lens 11b. , And a scanning control device (not shown). In this specification, in the XYZ three-dimensional orthogonal coordinate system, the direction along the longitudinal direction of the photosensitive drum 1030 is defined as the Y-axis direction, and the direction along the optical axis of each scanning lens (11a, 11b) is defined as the X-axis direction. explain. In the following, for convenience, the direction corresponding to the main scanning direction is abbreviated as “main scanning corresponding direction”, and the direction corresponding to the sub scanning direction is abbreviated as “sub scanning corresponding direction”.

  As shown in FIG. 3 as an example, the light source 14 includes a two-dimensional array 100 in which 40 light emitting units (ch1 to ch40) are formed on one substrate, and is in a sub-scanning direction (hereinafter, for convenience). Eight light emitting section rows each including five light emitting sections arranged in a line along the “S direction” are arranged in the main scanning corresponding direction (hereinafter referred to as “M direction” for convenience). That is, the number of light emitting unit rows is larger than the number of light emitting units constituting one light emitting unit row.

  Here, in order to distinguish each light emitting part row, for the sake of convenience, the first light emitting part row L1, the second light emitting part row L2, the third light emitting part row L3, the fourth light emitting element row L2, from the left to the right in FIG. The light emitting part row L4, the fifth light emitting part row L5, the sixth light emitting part row L6, the seventh light emitting part row L7, and the eighth light emitting part row L8.

  Then, when 40 light emitting units are orthogonally projected onto a virtual line extending in the S direction, the light emitting unit that is closest to the −S side is set as the light emitting unit ch1, and the light emitting unit ch2, light emitting unit ch3,. ..., the light emitting unit ch40.

  Here, the five light emitting units of the first light emitting unit row L1 are the light emitting unit ch5, the light emitting unit ch13, the light emitting unit ch21, the light emitting unit ch29, and the light emitting unit ch37.

  The five light emitting units of the second light emitting unit row L2 are a light emitting unit ch6, a light emitting unit ch14, a light emitting unit ch22, a light emitting unit ch30, and a light emitting unit ch38.

  The five light emitting units in the third light emitting unit row L3 are a light emitting unit ch7, a light emitting unit ch15, a light emitting unit ch23, a light emitting unit ch31, and a light emitting unit ch39.

  The five light emitting units in the fourth light emitting unit row L4 are a light emitting unit ch8, a light emitting unit ch16, a light emitting unit ch24, a light emitting unit ch32, and a light emitting unit ch40.

  The five light emitting units in the fifth light emitting unit row L5 are a light emitting unit ch1, a light emitting unit ch9, a light emitting unit ch17, a light emitting unit ch25, and a light emitting unit ch33.

  The five light emitting units in the sixth light emitting unit row L6 are a light emitting unit ch2, a light emitting unit ch10, a light emitting unit ch18, a light emitting unit ch26, and a light emitting unit ch34.

  The five light emitting units in the seventh light emitting unit row L7 are a light emitting unit ch3, a light emitting unit ch11, a light emitting unit ch19, a light emitting unit ch27, and a light emitting unit ch35.

  The five light emitting units in the eighth light emitting unit row L8 are a light emitting unit ch4, a light emitting unit ch12, a light emitting unit ch20, a light emitting unit ch28, and a light emitting unit ch36.

  Regarding the M direction, the distance between the first light emitting part row L1 and the second light emitting part row L2 is X4, the distance between the second light emitting part row L2 and the third light emitting part row L3 is X3, and the third light emitting part row L3. And the fourth light emitting unit row L4 are X2, the fourth light emitting unit row L4 and the fifth light emitting unit row L5 are X1, and the fifth light emitting unit row L5 and the sixth light emitting unit row L6 are X2. The distance between the sixth light emitting part row L6 and the seventh light emitting part row L7 is X3, the distance between the seventh light emitting part row L7 and the eighth light emitting part row L8 is X4, and X1> X2> X3> X4. . That is, the two-dimensional array 100 is a so-called non-uniformly arranged two-dimensional array, and the interval between two light emitting unit rows that are located in the center of a plurality of rows and are adjacent to each other is located on the end side of the plurality of rows and is adjacent to each other. It is wider than the interval between the two light emitting unit rows.

  Then, when 40 light emitting units are orthogonally projected onto a virtual line extending in the S direction, if the predetermined value is c, as shown in FIG. 4, the light emitting units ch1 to ch20 are equally spaced 2c. The interval between the light emitting part ch20 and the light emitting part ch21 is 3c, and the light emitting part ch21 to the light emitting part ch40 are equally spaced 2c.

  Specifically, c = 4.4 μm, X1 = 48 μm, X2 = 46.5 μm, X3 = 38.5 μm, and X4 = 26 μm. The distance d1 between the light emitting part ch5 and the light emitting part ch13 in the S direction is 70.4 (= 2 × c × 8) μm, and the distance d2 between the light emitting part ch13 and the light emitting part ch21 in the S direction is 74.8 (= 2 × c × 7 + 3 × c) μm (see FIG. 3).

  Incidentally, FIG. 5A shows a conventional two-dimensional array in which 40 light emitting units are arranged at equal intervals in both the M direction and the S direction as a comparative example. In this two-dimensional array, so-called “adjacent scanning” is performed during main scanning (see FIG. 5B). That is, the two-dimensional array shown in FIG. 5A is a so-called “adjacent scanning arrangement” two-dimensional array.

  Returning to FIG. 2, the coupling lens 15 converts the light emitted from the light source 14 into substantially parallel light.

  The aperture plate 16 has an aperture and defines the beam diameter of the light that has passed through the coupling lens 15.

  The cylindrical lens 17 forms an image of the light that has passed through the opening of the aperture plate 16 in the vicinity of the deflection reflection surface of the polygon mirror 13 in the Z-axis direction.

  The optical system arranged on the optical path between the light source 14 and the polygon mirror 13 is also called a pre-deflector optical system. In the present embodiment, the pre-deflector optical system includes a coupling lens 15, an aperture plate 16, and a cylindrical lens 17.

  The polygon mirror 13 has a four-sided mirror, and each mirror serves as a deflection reflection surface. The polygon mirror 13 rotates at a constant speed around an axis parallel to the Z-axis direction, and deflects light from the cylindrical lens 17.

  The deflector-side scanning lens 11 a is disposed on the optical path of the light deflected by the polygon mirror 13.

  The image plane side scanning lens 11b is disposed on the optical path of light via the deflector side scanning lens 11a. Then, the light passing through the image surface side scanning lens 11b is irradiated on the surface of the photosensitive drum 1030, and a light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 1030 as the polygon mirror 13 rotates. That is, the photoconductor drum 1030 is scanned. The moving direction of the light spot at this time is the “main scanning direction”. The rotation direction of the photosensitive drum 1030 is the “sub-scanning direction”.

  As shown in FIG. 6, when the (n−1) -th main scan is completed, the scanning control device sets −c in the sub-scanning direction with respect to the irradiation position of the light from the light emitting unit ch21 on the surface of the photosensitive drum 1030. The photosensitive drum 1030 is rotated so that the light from the light emitting unit ch1 is irradiated at a position shifted by a corresponding value, and the n-th main scan is performed. When the n-th main scanning is completed, the light emitting unit ch1 shifts to a position shifted by a value corresponding to −c in the sub-scanning direction with respect to the light irradiation position from the light emitting unit ch21 on the surface of the photosensitive drum 1030. The photosensitive drum 1030 is rotated so that light is irradiated, and the (n + 1) th main scan is performed. That is, so-called “uneven interlaced scanning” is performed. Thereby, the surface of the photosensitive drum 1030 can be scanned at a constant interval corresponding to the predetermined value c in the sub-scanning direction. In this case, if the magnification of the optical system of the optical scanning device 1010 is about 1.2 times, the pitch in the sub-scanning direction on the surface of the photosensitive drum 1030 is about 5.3 μm, and the high density of 4800 dpi in the sub-scanning direction. Can be written with.

  By the way, so-called “uniform interlaced scanning” and a two-dimensional array suitable for it (two-dimensional array of uniform interlaced scanning arrangement) are disclosed in Japanese Patent Publication No. 1-445065 or Japanese Patent Publication No. 6-48846. .

  In the present embodiment, the light emitting portion ch1 is in the light emitting portion row L5, and the light emitting portion ch40 is in the light emitting portion row L4. That is, when 40 light emitting units are orthogonally projected on a virtual line extending in the S direction, the two light emitting units (ch1 and ch40) located at both ends with respect to the S direction are in positions other than both ends with respect to the M direction. Has been placed. As a result, the light emitting section ch1 and the light emitting section ch40 at both ends with respect to the S direction are close to each other with respect to the M direction, and the beam in the sub-scanning direction due to errors of the polygon mirror 13 (A dimension variation, surface tilt, axis tilt, etc.). Pitch error can be reduced.

  As described above, according to the surface-emitting laser array 100 according to the present embodiment, when 40 light emitting units are orthogonally projected onto a virtual line extending in the S direction (one direction) corresponding to the sub-scanning direction, When the value is c, the light emitting part ch1 to the light emitting part ch20 is equally spaced 2c, the distance between the light emitting part ch20 and the light emitting part ch21 is 3c, and the light emitting part ch21 to the light emitting part ch40 is equally spaced 2c. In this case, the size is slightly larger than that of the two-dimensional array with the adjacent scanning arrangement, but the heat dissipation is remarkably improved as compared with the two-dimensional array with the adjacent scanning arrangement. In other words, when compared at the same writing density, the element spacing in the sub-scanning direction can be widened, so that the output uniformity can be easily controlled by reducing the thermal interference, and density unevenness can be suppressed and high-quality image formation can be performed. Also, compared to a two-dimensional array with a uniform interlaced scanning arrangement, heat dissipation is improved even if the size is the same. That is, even if the size is not increased so much, the interval between the light emitting portions in the region that receives more influence from other light emitting portions can be increased. Therefore, it is possible to make the influence of thermal interference smaller than before without increasing the size.

  In addition, eight light emitting section rows each including five light emitting sections arranged in a line along the S direction are arranged in the M direction corresponding to the main scanning direction. With respect to the M direction, the distance between the first light emitting part row L1 and the second light emitting part row L2 is X4, the distance between the second light emitting part row L2 and the third light emitting part row L3 is X3, and the third light emitting part row L3. And the fourth light emitting unit row L4 are X2, the fourth light emitting unit row L4 and the fifth light emitting unit row L5 are X1, and the fifth light emitting unit row L5 and the sixth light emitting unit row L6 are X2. The distance between the sixth light emitting part row L6 and the seventh light emitting part row L7 is X3, the distance between the seventh light emitting part row L7 and the eighth light emitting part row L8 is X4, and X1> X2> X3> X4. .

  As a result, when a plurality of light emitting units operate simultaneously, the influence of heat generated from the light emitting units arranged in the peripheral part of the surface emitting laser array on the light emitting part arranged in the central part is reduced, and the central part is reduced. The temperature rise of the arranged light emitting units is reduced as compared with the case where a plurality of light emitting units are arranged at equal intervals in the S direction and the M direction. Therefore, the output characteristics of each light emitting section can be made uniform, and as a result, high quality image formation can be performed. In addition, since the temperature of the light emitting part that is the highest temperature is lowered, the lifetime of the surface emitting laser array can be extended.

  Further, the number of light emitting unit rows is larger than the number of light emitting units constituting one light emitting unit row. As a result, it is possible to increase the writing density while reducing the influence of thermal interference between the light emitting units and securing a space necessary for passing the wiring of each light emitting unit.

  Further, according to the optical scanning device 1010 according to the present embodiment, since the light source 14 has the surface emitting laser array 100, as a result, the surface of the photosensitive drum 1030 can be scanned at high density and high speed. It becomes. Furthermore, control for equalizing the output is facilitated by reducing thermal interference. As a result, uneven density in the output image is suppressed, and high-quality image formation can be performed.

  By the way, in the adjacent scanning (see FIG. 5), there is a case where a so-called reciprocity law failure of the photoconductor in which both ends in the main scanning direction are written darkly may occur. However, in this embodiment, since interlaced scanning can be performed, this can be reduced.

  Further, since the lifetime of the surface emitting laser array is long, the light source unit including the light source 14 can be reused.

  In addition, the laser printer 1000 according to the present embodiment includes the optical scanning device 1010. As a result, a high-definition image can be formed at high speed.

  If the image formation speed is about the same as the conventional one, it is possible to reduce the number of light emitting portions in the surface emitting laser array, greatly increasing the manufacturing yield of the surface emitting laser array and reducing the cost. Can be achieved.

  Further, even if the writing dot density increases, printing can be performed without reducing the printing speed.

  By the way, for example, when a surface emitting laser array is used for a so-called writing optical unit, the writing optical unit is disposable when the life of the light emitting unit is short. However, since the surface emitting laser array equivalent to the surface emitting laser array 100 has a long life, the writing optical unit using the surface emitting laser array equivalent to the surface emitting laser array 100 can be reused. Therefore, promotion of resource protection and reduction of environmental load can be achieved. This also applies to other devices using a surface emitting laser array.

  In the above embodiment, a surface emitting laser array 100A shown in FIG. 7 may be used instead of the surface emitting laser array 100. In the surface emitting laser array 100A, when 40 light emitting units are orthogonally projected onto a virtual line extending in the S direction, assuming that a predetermined value is c, the light emitting units ch1 to ch20 are equally spaced 2c. The interval between the part ch20 and the light emitting part ch21 is c, and the light emitting part ch21 to the light emitting part ch40 are equally spaced 2c. In this case, with respect to the S direction, the interval between the light emitting unit ch20 and the light emitting unit ch21 is narrower than other light emitting unit intervals, but with respect to the S direction, the other light emitting unit intervals are twice as large as in the case of FIG. Therefore, the size is slightly larger than that of the two-dimensional array with the adjacent scanning arrangement, but the heat dissipation can be remarkably improved as compared with the two-dimensional array with the adjacent scanning arrangement. FIG. 8 shows unequal interlaced scanning in this case. Also in this case, the surface of the photosensitive drum 1030 can be scanned at a constant interval corresponding to the predetermined value c in the sub-scanning direction. Note that X1 = 48 μm, X2 = 46.5 μm, X3 = 38.5 μm, and X4 = 26 μm. Further, in this case, as is apparent from a comparison between FIG. 6 and FIG. 8, unlike the above embodiment, the light emitting portion ch1 and the light emitting portion ch40 that are farthest apart in the sub-scanning direction are separated (not adjacent). Since writing is performed, the influence of banding due to the beam pitch error in the sub-scanning direction caused by the error of the polygon mirror 13 can be reduced, and deterioration in image quality can be reduced. Further, since the total distance in the sub-scanning direction can be shortened while performing interlaced scanning, it is possible to reduce the beam pitch error in the sub-scanning direction and stabilize the light spot. The total distance in the sub-scanning direction is only a little shorter with the 40ch array, but the difference is large with about 10ch array.

  Here, advantages of the unequal interlaced scanning arrangement over the uniform interlaced scanning arrangement will be described with reference to FIGS. Here, for the sake of clarity, a method of filling the sub-scanning direction with two main scans (abbreviated as “two-time scan method”) will be described here, but the sub-scan is performed with three or more main scans. The scanning direction may be filled. However, in the method of filling with three or more main scans, the interval between the light emitting portions is increased accordingly, so that a large optical element is required and the optical characteristics are deteriorated. Therefore, when the number of light emitting portions (number of channels) is large, the twice scanning method is preferable. Further, for example, as disclosed in Japanese Patent Application Laid-Open No. 2003-255247, in controlling each light emitting unit, the number of light emitting units in the array is preferably an even number such as a multiple of 8.

  FIG. 9 shows a case where uniform interlaced scanning is performed using a surface emitting laser array in which an even number (8 ch) of light emitting units are arranged in an even interlaced scanning manner. FIG. 10 shows a case where uniform interlaced scanning is performed using a surface emitting laser array in which an odd number (7 ch) of light emitting units are arranged in an even interlaced scanning manner. FIG. 11 shows a case where uneven scanning is performed using a surface emitting laser array in which an even number (8 ch) of light emitting units are arranged in uneven scanning. FIG. 12 shows a case where uneven scanning is performed using a surface emitting laser array in which an odd number (7 ch) of light emitting units are arranged in uneven scanning.

  As shown in FIG. 9, when the number of light emitting portions in the array is an even number in the interlace scanning, the scanning lines are filled, but the shift amount in the sub scanning direction is different for each main scanning. In order to change the amount of shift in the sub-scanning direction irregularly, it is necessary to change the rotation speed and shape of the polygon mirror and the rotation speed of the photosensitive drum. However, when switching the rotation speed and phase, uneven rotation occurs. In the polygon mirror, a positional deviation (vertical line fluctuation) in the main scanning direction and a positional deviation (banding or the like) in the sub-scanning direction are caused on the surface of the photosensitive drum, and it is extremely difficult to control these with high accuracy. Therefore, it is preferable that the rotation speed of the polygon mirror (main scanning speed) and the rotation speed of the photosensitive drum (sub-scanning speed) are constant during writing. Therefore, in the case of uniform interlaced scanning, when the two-time scanning method is adopted, the number of light emitting portions in the array needs to be an odd number. Note that the method of filling with three main scans is possible, but it is not preferable because the interval between the light emitting portions increases as described above.

  In the case of non-uniform interlaced scanning, the number of light emitting parts in the array needs to be an even number. In the case of an odd number, as shown in FIG.

  Therefore, in order to perform interlaced scanning with an even number of light emitting units, it is preferable to have an uneven interlaced scanning arrangement. Furthermore, in order to perform interlaced scanning with an even number of light emitting units without increasing the interval between the light emitting units, it is preferable that an unequal interlaced scanning arrangement is performed by the two-time scanning method.

  Moreover, in the said embodiment, it may replace with the said surface emitting laser array 100, and may use the surface emitting laser array 100B shown by FIG.

  In the surface emitting laser array 100B, when 40 light emitting units are orthogonally projected onto an imaginary line extending in the S direction, assuming that a predetermined value is c, the light emitting units ch1 to ch3, the light emitting units ch4 to ch6, Light emitting unit ch7 to light emitting unit ch9, light emitting unit ch10 to light emitting unit ch11, light emitting unit ch12 to light emitting unit ch15, light emitting unit ch26 to light emitting unit ch29, light emitting unit ch30 to light emitting unit ch31, light emitting unit ch32 to light emitting unit ch34, light emitting unit Ch35 to light emitting part ch37 and light emitting part ch38 to light emitting part ch40 are equally spaced c.

  In addition, light emitting unit ch3 to light emitting unit ch4, light emitting unit ch6 to light emitting unit ch7, light emitting unit ch9 to light emitting unit ch10, light emitting unit ch15 to light emitting unit ch16, light emitting unit ch29 to light emitting unit ch30, light emitting unit ch31 to light emitting unit ch32, The light emitting part ch34 to the light emitting part ch35 and the light emitting part ch37 to the light emitting part ch38 are equally spaced 2c.

  The light emitting portions ch17 to ch18, the light emitting portions ch23 to light emitting portion ch24 are equally spaced 3c, and the light emitting portions ch18 to light emitting portion ch20 and the light emitting portions ch21 to light emitting portion ch23 are equally spaced 4c.

  Further, the light emitting portions ch16 to ch17, the light emitting portions ch24 to the light emitting portions ch25 are equally spaced 5c, and the light emitting portions ch20 to the light emitting portions ch21 are spaced 7c.

  FIG. 14 shows non-uniform interlace scanning when this surface emitting laser array 100B is used. Also in this case, the surface of the photosensitive drum 1030 can be scanned at a constant interval corresponding to the predetermined value c in the sub-scanning direction. Note that X1 = 48 μm, X2 = 46.5 μm, X3 = 38.5 μm, and X4 = 26 μm.

  In the above embodiment, a surface emitting laser array 100C shown in FIG. 15 may be used instead of the surface emitting laser array 100.

  In the surface emitting laser array 100C, when 40 light emitting units are orthogonally projected onto an imaginary line extending in the S direction, if a predetermined value is c, the light emitting unit ch2 to the light emitting unit ch3, the light emitting unit ch5 to the light emitting unit ch7, Light emitting unit ch8 to light emitting unit ch9, light emitting unit ch12 to light emitting unit ch14, light emitting unit ch18 to light emitting unit ch19, light emitting unit ch22 to light emitting unit ch23, light emitting unit ch27 to light emitting unit ch29, light emitting unit ch32 to light emitting unit ch33, light emitting unit About ch34-light emission part ch36, and light emission part ch38-light emission part ch39, it is equal interval c.

  In addition, light emitting unit ch1 to light emitting unit ch2, light emitting unit ch4 to light emitting unit ch5, light emitting unit ch7 to light emitting unit ch8, light emitting unit ch9 to light emitting unit ch10, light emitting unit ch11 to light emitting unit ch12, light emitting unit ch14 to light emitting unit ch15, Light emitting part ch17 to light emitting part ch18, Light emitting part ch23 to light emitting part ch24, Light emitting part ch26 to Light emitting part ch27, Light emitting part ch29 to Light emitting part ch30, Light emitting part ch31 to Light emitting part ch32, Light emitting part ch33 to Light emitting part ch34, Light emitting part Ch36 to light emitting unit ch37 and light emitting unit ch39 to light emitting unit ch40 are equally spaced 2c.

  The light emitting unit ch3 to the light emitting unit ch4, the light emitting unit ch15 to the light emitting unit ch16, the light emitting unit ch19 to the light emitting unit ch22, the light emitting unit ch25 to the light emitting unit ch26, and the light emitting unit ch37 to the light emitting unit ch38 are equally spaced 3c. The light emitting unit ch10 to the light emitting unit ch11, the light emitting unit ch16 to the light emitting unit ch16, the light emitting unit ch24 to the light emitting unit ch25, and the light emitting unit ch30 to the light emitting unit ch31 are equally spaced 4c.

  FIG. 16 shows non-uniform interlace scanning when this surface emitting laser array 100C is used. Also in this case, the surface of the photosensitive drum 1030 can be scanned at a constant interval corresponding to the predetermined value c in the sub-scanning direction. Note that X1 = 26 μm, X2 = 70 μm, X3 = 26 μm, and X4 = 26 μm.

  Moreover, in the said embodiment, it may replace with the said surface emitting laser array 100, and may use the surface emitting laser array 100D shown by FIG.

  In the surface emitting laser array 100D, the light emitting part ch1 is arranged at the most −S side and the most −M side position, and the light emitting part ch40 is arranged at the most + S side and the most + M side position. When 40 light emitting units are orthogonally projected onto a virtual line extending in the S direction, assuming that a predetermined value is c, the light emitting units ch1 to ch16 are equally spaced 2c, and the light emitting units ch16 and ch17. Is 3c, and the light emitting part ch17 to light emitting part ch40 are equally spaced 2c. Further, with respect to the M direction, the intervals between the light emitting unit rows are equal.

  Moreover, in the said embodiment, it may replace with the said surface emitting laser array 100, and may use the surface emitting laser array 100E shown by FIG.

  In the surface emitting laser array 100E, the light emitting part ch1 is arranged at the most −S side and the most −M side position, and the light emitting part ch40 is arranged at the most + S side and the most + M side position. When 40 light emitting units are orthogonally projected onto a virtual line extending in the S direction, assuming that a predetermined value is c, the light emitting units ch1 to ch16 are equally spaced 2c, and the light emitting units ch16 and ch17. Is c, and the light emitting portion ch17 to light emitting portion ch40 are equally spaced 2c. Further, with respect to the M direction, the intervals between the light emitting unit rows are equal.

  In the above embodiment, the laser printer 1000 is described as the image forming apparatus. However, the present invention is not limited to this. In short, an image forming apparatus including the optical scanning device 1010 can form a high-definition image at high speed.

  For example, an image forming apparatus that includes the optical scanning device 1010 and that directly irradiates laser light onto a medium (for example, paper) that develops color with laser light may be used.

  Further, an image forming apparatus using a silver salt film as the image carrier may be used. In this case, a latent image is formed on the silver salt film by optical scanning, and this latent image can be visualized by a process equivalent to a developing process in a normal silver salt photographic process. Then, it can be transferred to photographic paper by a process equivalent to a printing process in a normal silver salt photographic process. Such an image forming apparatus can be implemented as an optical plate making apparatus or an optical drawing apparatus that draws a CT scan image or the like.

  In addition, even an image forming apparatus that forms a multicolor image can form a high-definition image at high speed by using an optical scanning device that supports color images.

  For example, as shown in FIG. 19, a tandem color machine 1500 corresponding to a color image and including a plurality of photosensitive drums may be used. The tandem color machine 1500 includes a black (K) photosensitive drum K1, a charger K2, a developing unit K4, a cleaning unit K5, a transfer charging unit K6, a cyan (C) photosensitive drum C1, a charging unit. A developing unit C2, a developing unit C4, a cleaning unit C5, a transfer charging unit C6, a magenta (M) photosensitive drum M1, a charging unit M2, a developing unit M4, a cleaning unit M5, and a transfer charging unit M6; A yellow (Y) photosensitive drum Y1, a charger Y2, a developing unit Y4, a cleaning unit Y5, a transfer charging unit Y6, an optical scanning device 1010A, a transfer belt 80, a fixing unit 30 and the like are provided. .

  The optical scanning device 1010A includes a surface emitting laser array for black, a surface emitting laser array for cyan, a surface emitting laser array for magenta, and a surface emitting laser array for yellow. A plurality of surface emitting lasers of each surface emitting laser array are two-dimensionally arranged in the same manner as any of the surface emitting laser arrays 100 to 100E. The light from the surface emitting laser array for black is irradiated to the photosensitive drum K1 through the scanning optical system for black, and the light from the surface emitting laser array for cyan passes through the scanning optical system for cyan. The light from the surface emitting laser array for magenta is irradiated to the photosensitive drum C1, and the light from the surface emitting laser array for yellow is irradiated to the photosensitive drum M1 through the magenta scanning optical system. The photosensitive drum Y1 is irradiated through the scanning optical system.

  Each photosensitive drum rotates in the direction of the arrow in FIG. 19, and a charger, a developing device, a transfer charging unit, and a cleaning unit are arranged along the rotation direction. Each charger uniformly charges the surface of the corresponding photosensitive drum. The surface of the photosensitive drum charged by the charger is irradiated with light by the optical scanning device 1010A, and an electrostatic latent image is formed on the photosensitive drum. Then, a toner image is formed on the surface of the photosensitive drum by the corresponding developing device. Further, the toner image of each color is transferred onto the recording paper on the transfer belt 80 by the corresponding transfer charging means, and finally the image is fixed on the recording paper by the fixing means 30.

  In a tandem color machine, color misregistration may occur due to manufacturing error or position error of each part. However, since the optical scanning device 1010A has a plurality of light emitting units arranged two-dimensionally, the light emission to be turned on. By selecting the part, it is possible to improve the color misregistration correction accuracy.

  In this tandem color machine 1500, instead of the optical scanning device 1010A, a black optical scanning device, a cyan optical scanning device, a magenta optical scanning device, and a yellow optical scanning device may be used. In short, the plurality of surface emitting lasers of each surface emitting laser array need only be two-dimensionally arranged in the same manner as any of the surface emitting laser arrays 100 to 100E.

  Further, if the plurality of surface emitting lasers is an image forming apparatus including a two-dimensionally arranged surface emitting laser array similar to any of the surface emitting laser arrays 100 to 100E, the image does not include an optical scanning device. It may be a forming device.

  As described above, the surface emitting laser array of the present invention is suitable for reducing the influence of thermal interference without increasing the size. Moreover, the optical scanning device of the present invention is suitable for scanning the surface to be scanned at high density and high speed. The image forming apparatus of the present invention is suitable for forming a high-definition image at high speed.

  11a: scanning lens (part of scanning optical system), 11b: scanning lens (part of scanning optical system), 13: polygon mirror (deflector), 14: light source (part of light source unit), 100: surface emission Laser array, 100A ... Surface emitting laser array, 100B ... Surface emitting laser array, 100C ... Surface emitting laser array, 100D ... Surface emitting laser array, 100E ... Surface emitting laser array, 1000 ... Laser printer (image forming apparatus), 1010 ... Optical scanning device, 1010A ... Optical scanning device, 1030 ... Photosensitive drum (photosensitive member), 1500 ... Tandem color machine (image forming device), K1, C1, M1, Y1 ... Photosensitive drum (photosensitive member), ch1 to ch40 ... light emitting part.

JP 11-340570 A JP 11-354888 A JP 2005-274755 A JP 2005-234510 A JP 2001-272615 A

Claims (10)

In a surface emitting laser array in which a plurality of light emitting portions are two-dimensionally arranged,
When the plurality of light emitting units are orthogonally projected onto a virtual line extending in one direction, an interval on the virtual line is a natural number multiple of a predetermined value,
The plurality of light emitting units are adjacent to the first light emitting unit, the second light emitting unit adjacent to the first light emitting unit when the orthographic projection is performed, and the second light emitting unit when the orthographic projection is performed. And a third light emitting unit
With respect to the one direction, an interval between the first light emitting unit and the second light emitting unit is different from an interval between the second light emitting unit and the third light emitting unit.
The number of the said several light emission parts is an even number, The surface emitting laser array characterized by the above-mentioned. The first to third light emitting units are arranged at the center of the two-dimensional array with respect to the one direction,
The second light emitting unit and the third light emitting unit are arranged near both ends of the two-dimensional array with respect to a direction orthogonal to the one direction,
The distance between the second light emitting unit and the third light emitting unit with respect to the one direction is narrower than the interval between the first light emitting unit and the second light emitting unit. The surface emitting laser array described. Regarding the one direction,
2. The surface emitting laser array according to claim 1, wherein an interval between the plurality of light emitting portions is wider in a central portion than in an end portion in the two-dimensional array. Regarding a direction orthogonal to the one direction,
The surface emitting laser array according to any one of claims 1 to 3, wherein the interval between the plurality of light emitting portions is wider at a central portion than at an end portion in the two-dimensional array. The plurality of light emitting units are arranged in a plurality of rows in a direction orthogonal to the one direction, and the light emitting unit row composed of at least two light emitting units arranged along the one direction.
5. The surface-emitting laser array according to claim 1, wherein the number of the light emitting unit rows is larger than the number of light emitting units constituting one light emitting unit row.   The two light emitting units located at both ends with respect to the one direction are arranged at positions excluding both ends with respect to a direction orthogonal to the one direction. The surface emitting laser array according to one item. An optical scanning device that scans a surface to be scanned with light,
A light source unit comprising the surface emitting laser array according to claim 1, wherein one direction of the surface emitting laser array coincides with a direction corresponding to a sub-scanning direction;
A deflector for deflecting light from the light source unit;
A scanning optical system for condensing the light deflected by the deflector onto the surface to be scanned. At least one photoreceptor;
An image forming apparatus comprising: at least one optical scanning device according to claim 7 that scans the at least one photosensitive member with light including image information.   The image forming apparatus according to claim 8, wherein the image information is multicolor color image information.   An image forming apparatus comprising the surface emitting laser array according to any one of claims 1 to 6 as a writing light source for writing image information on a photoconductor.

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