JP2009260392A - Two-dimensional surface-emitting laser array, optical scanning device and electrophotographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable individual VCSELs to be easily wired independently and reduce thermal interference between the VCSELs, even when the VCSELs are highly integrated. <P>SOLUTION: A two-dimensional surface-emitting laser array is constituted of an active layer formed on a semiconductor substrate, a spacer layer formed sandwiching the active layer, a first and second reflective mirrors formed sandwiching the active layer and the spacer, a first electrode formed on the first reflective mirror, and a second electrode formed on the back of the semiconductor substrate. Each of the surface-emitting lasers is independently controlled, even in a case that a plurality of surface-emitting lasers are formed on one semiconductor substrate by forming a mesa structure by processing the first reflective mirror, the spacer layer and the active layer, and the first electrode on the mesa structure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a compound semiconductor device and a printer, and more particularly to a two-dimensional surface emitting laser array, an optical scanning apparatus, and an electrophotographic apparatus.

  Conventionally, an image forming method using a laser is widely used as an image forming means for obtaining high-definition image quality in image recording in electrophotography. In the case of electrophotography, a method is generally used in which a latent image is formed by rotating a drum (sub-scanning) while scanning a laser (main scanning) using a polygon mirror in the axial direction of a photosensitive drum.

  On the other hand, in the electrophotographic field, high definition of images and high speed of output are required. As a method for realizing this, a method of increasing the speed of both main scanning and sub-scanning and increasing the output of the laser or increasing the sensitivity of the photosensitive member can be considered, but this method improves the image forming speed. There are many issues such as the development of a light source or a high-sensitivity photosensitive member accompanying the increase in the output of a laser, the reinforcement of the housing that supports it by increasing the speed of main and sub-scans, and the development of a position control method during high-speed scanning. Occurs and requires a great deal of cost and time. In addition, when the resolution of an image is doubled in order to increase the definition of an image, twice the time is required in both the main scanning direction and the sub-scanning direction. . Therefore, in order to achieve high definition of images, it is necessary to simultaneously achieve high speed image output.

  As another method for achieving high-speed image output, a method of using a multi-beam laser is conceivable. In a current high-speed output machine, a plurality of lasers are generally used. By making the laser multi-beamed, the area where the latent image is formed in one main scan is enlarged, and when using n lasers, the above latent image is formed. The image forming area is n times, and the time required for image formation is 1 / n.

  As such an example, a multi-beam semiconductor laser having a plurality of light emitting light sources in one chip has been proposed (see, for example, Patent Documents 1 and 2). The beam or about 8 beams is the limit, and it is not possible to cope with the speeding up of image output that will be developed in the future.

  On the other hand, a surface emitting laser (hereinafter referred to as VCSEL), which has been actively researched in recent years, can be easily integrated two-dimensionally, and more VCSELs can be integrated two-dimensionally, and an integration method is devised. Thus, the actual beam pitch can be set narrower. However, as more VCSELs are integrated, complex wiring is required, which may hinder VCSEL integration.

  As a conventional technique, a two-dimensional VCSEL array using a plurality of VCSELs has been proposed (see, for example, Patent Document 3), and the arrangement of the VCSELs according to the present invention is determined as shown in FIG. That is, the VCSELs are arranged at equal intervals on the first base line, the plurality of VCSELs are passed through the centers of the plurality of VCSELs, and the second base line is defined at a predetermined angle and direction with respect to the first base line. They are arranged at equal intervals. However, in such an arrangement of VCSELs, considering the actual size of the VCSEL and the distance between adjacent VCSELs, independent wiring of the inner VCSEL is difficult with the means described therein, and even if realized, the arrangement of the VCSEL There are a lot of restrictions in balance with Furthermore, it will become increasingly difficult if the image resolution is improved in the future. In this conventional invention, the arrangement of the VCSEL as shown in FIG. 12B is also shown, but the same applies to this case. On the other hand, means for wiring the integrated VCSELs in a matrix has been proposed (see, for example, Patent Documents 3 and 4).

  However, when the VCSELs are highly integrated, the inventions of Patent Documents 3 and 4 cannot enable independent wiring of individual VCSELs, and cannot control all VCSELs completely independently.

  The present invention has been made in view of the above circumstances, and enables independent wiring of individual VCSELs even when VCSELs are highly integrated, and reduces thermal interference between the VCSELs. It is an object.

  Another object of the present invention is to provide an optical scanning device capable of recording high-definition images uniformly at high speed.

  Another object of the present invention is to provide an electrophotographic apparatus capable of outputting a high-speed recording medium.

  In order to achieve this object, the invention according to claim 1 includes first and second reflecting mirrors formed on a semiconductor substrate, and an active layer sandwiched between the first and second reflecting mirrors. A two-dimensional surface-emitting laser array, a plurality of surface-emitting lasers arranged at equal intervals on a first base line defined in a predetermined direction on a semiconductor substrate, and a 2n-th (n = 0, 1, 2,...), Passes through the center of the surface emitting laser, forms a predetermined angle θ with respect to the first base line, and is arranged at equal intervals on the second base line defined in a predetermined direction. The plurality of surface emitting lasers and the center of the 2n + 1-th (n = 0, 1, 2,...) Surface emitting laser on the first base line and a predetermined angle −θ with respect to the first base line The direction defined by the second base line is the third base defined in the predetermined direction on the opposite side across the first base line. A plurality of surface emitting lasers arranged at equal intervals on the line, and a center of the surface emitting laser on the first base line and a plurality of surface emitting lasers on the second and third base lines The orthogonal projection points on the first base line are arranged at equal intervals.

  The invention according to claim 2 is a two-dimensional surface-emitting laser array having first and second reflecting mirrors formed on a semiconductor substrate, and an active layer sandwiched between the first and second reflecting mirrors. The base points defined at equal intervals on the first base line defined in a predetermined direction on the semiconductor substrate and the 2nth (n = 0, 1, 2,...) On the first base line. A plurality of surface emitting lasers that pass through the base point, form a predetermined angle θ with respect to the first base line, and are arranged at equal intervals on the second base line defined in the predetermined direction, and the first base line 2n + 1 (n = 0, 1, 2,...) Passing through the base point, forming a predetermined angle −θ with respect to the first base line, and the direction defined by the second base line sandwiching the first base line A plurality of surface emitting lasers arranged at equal intervals on a third base line defined in a predetermined direction on the opposite side, and second and Orthographic projection points from the centers of the plurality of surface emitting lasers on the third base line to the first base line are arranged at equal intervals.

  According to a third aspect of the present invention, there is provided the two-dimensional surface-emitting laser array according to the first or second aspect, means for converting laser light emitted from the two-dimensional surface-emitting laser array into a parallel beam, and means for scanning the parallel beam. And means for converting so that the focal point is obtained on the same plane from the scanned parallel beam.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the light receiving element that detects the laser light emitted from the two-dimensional surface-emitting laser array, and the light-receiving element is scanned with the two-dimensional surface-emitting laser array. And means for inserting between the means.

  The invention according to claim 5 is the invention according to claim 3, wherein a half mirror that reflects part of the laser light emitted from the two-dimensional surface-emitting laser array and transmits the remaining laser light, and the reflected laser And a light receiving element for detecting light.

  The invention according to claim 6 is the invention according to claim 4 or 5, further comprising means for expanding the laser beam at a predetermined magnification between the two-dimensional surface-emitting laser array and the light receiving element. To do.

  According to a seventh aspect of the invention, in the invention according to any one of the third to sixth aspects, a light receiving element is provided at the scanning end.

  According to an eighth aspect of the invention, the optical scanning device according to any one of the third to seventh aspects is provided.

  According to the present invention, even when a large number of two-dimensional surface emitting laser arrays having a plurality of VCSELs are integrated, independent wiring of each VCSEL can be easily performed, and all the VCSELs can be controlled completely independently. it can.

It is a figure which shows the structure of each VCSEL which comprises a two-dimensional surface emitting laser array. It is a figure which shows the arrangement | sequence method of several VCSEL at the time of making into two-dimensional array. It is a figure which shows the independent wiring method of several VCSEL. It is a figure which concerns on Example 2 of this invention and shows the arrangement | sequence method of VCSEL in the two-dimensional surface emitting laser array by which the space | interval of each VCSEL was ensured. FIG. 9 is a diagram illustrating a configuration of an optical scanning device according to a third embodiment of the present invention, which includes a two-dimensional surface-emitting laser array, a collimator lens, a polygon mirror, and an fθ lens. FIG. 10 is a diagram illustrating an optical scanning device according to a fourth embodiment of the present invention, which includes a light receiving element that detects laser light emitted from a two-dimensional surface-emitting laser array, and a unit that inserts the light receiving element into an optical path. . A fifth embodiment of the present invention includes a half mirror that reflects part of laser light emitted from a two-dimensional surface-emitting laser array and transmits the remaining laser light, and a light receiving element that detects the reflected light. FIG. An optical scanning apparatus according to a sixth embodiment of the present invention, comprising means for enlarging laser light emitted from a two-dimensional surface-emitting laser array at a predetermined magnification and a light receiving element for detecting the enlarged laser light. FIG. FIG. 10 is a diagram illustrating an optical scanning device according to a seventh embodiment of the present invention that includes a light receiving element at the end in the scanning direction. FIG. 10 is a diagram illustrating an electrophotographic apparatus using an optical scanning device according to an eighth embodiment of the present invention. It is a figure which shows the electrophotographic apparatus containing the optical scanning device using a two-dimensional surface emitting laser array. It is a figure which shows arrangement | positioning of VCSEL of the two-dimensional VCSEL array using several VCSEL according to invention of patent document 3 which is a prior art.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  In recent years, in the field of electrophotography, higher speed of image output and higher density of images have been demanded. Until now, this requirement has been met by increasing the speed of the polygon mirror and improving the laser output.

  When forming an image in current electrophotography, laser light is reflected by a polygon mirror that rotates at high speed, and is irradiated in a row in the main scanning direction of the photosensitive member according to image information, and then the photosensitive drum is aligned in the sub-scanning direction. A latent image was formed by repeating the process of scanning pixels. When forming a latent image on the photoconductor, it is necessary to irradiate laser light with a certain energy or more per unit area. Therefore, in order to achieve high-speed latent image formation, the rotation speed of the polygon mirror is improved. Not only that, but also the laser power must be improved. However, there are limits to the improvement in the number of revolutions of the polygon mirror and the laser output, especially the former is about 2-3 times the current limit.

  As another method for realizing high-speed image formation, a multi-beam laser can be considered. When forming a latent image using a multi-beam laser, when scanning on the photosensitive member using the polygon mirror for main scanning, multiple rows can be scanned simultaneously according to the number of lasers in one scan, so the polygon mirror rotates. Even if the number and laser output are the same as before, latent image formation can be realized at higher speed. However, the edge-emitting semiconductor lasers used in the past are difficult to realize other than a one-dimensional array in the multi-beam configuration, and because of the large power consumption, it is difficult to prevent the output and lifetime from being reduced due to mutual thermal interference. It is. Even if it is realized, a very complicated process is required, and a significant increase in cost is unavoidable as compared with a single-element edge-emitting semiconductor laser. This tendency becomes more prominent as the number of beams increases, and it is difficult to cope with future image forming speedup. In the case of using a plurality of single-element single-surface-emitting semiconductor lasers, the number of optical systems is the same as the number of elements, and it goes without saying that a significant increase in cost is inevitable.

  On the other hand, as a means for solving these problems simultaneously, a writing light source in which surface emitting lasers are arrayed can be considered. Since VCSEL can extract laser light perpendicularly to the substrate, it is easy to highly integrate light emitting elements. However, when a large number of light emitting elements are integrated, it becomes a problem to realize independent wiring of the light emitting elements.

  FIG. 1 to FIG. 3 are diagrams for explaining the first embodiment. The configuration of each VCSEL constituting the two-dimensional surface emitting laser array in FIG. 1, and the arrangement method of a plurality of VCSELs when two-dimensionally arrayed in FIG. FIG. 3 shows an independent wiring method of the plurality of VCSELs, which will be described below.

  In FIG. 1 (a-1), an active layer formed on a semiconductor substrate, a spacer layer formed so as to sandwich the active layer, and first and second reflecting mirrors formed so as to sandwich them, a first reflection A surface emitting laser comprising a first electrode formed on a mirror and a second electrode formed on the back surface of a semiconductor substrate is shown. When a plurality of surface emitting lasers are formed on one semiconductor substrate by forming a mesa structure formed by processing up to the first reflector, spacer layer, and active layer, and forming a first electrode on the mesa structure Even so, each surface emitting laser can be controlled independently. The contact method of the first and second ohmic electrodes with the VCSEL is not limited to the example shown in FIG. 1 (a-1), but has an intracavity contact structure as shown in FIG. 1 (a-2). It doesn't matter.

  In FIG. 2, a first base line is defined on a semiconductor substrate, and VCSELs are arranged at equal intervals on the first base line. Among the plurality of VCSELs arranged on the first base line, the second n (n = 0, 1, 2,...) Th VCSEL passes through the center and the angle formed with respect to the first base line is θ. Two baselines are defined, and VCSELs are arranged at equal intervals on the second baseline. At this time, when the orthogonal projection point to the first base line is defined from the centers of the plurality of VCSELs arranged on the second base line, it is defined by the centers of the 2n and 2n + 1th VCSELs on the first base line. The line segments must be arranged so that the orthogonal projection points are equally divided (a in FIG. 2).

  Further, among the plurality of VCSELs arranged on the first base line, a third base line is defined so that the angle formed with respect to the first base line passes through the center of the 2n + 1-th VCSEL and becomes −θ. VCSELs are arranged at equal intervals on the three baselines. At this time, when the orthogonal projection point to the first base line is defined from the centers of the plurality of VCSELs arranged on the third base line, it is defined by the 2n + 1 and 2n + 2th VCSEL centers on the first base line. The line segments must be arranged so that the orthogonal projection points are equally divided. Note that the angles formed by the second and third baselines with respect to the first baseline have the same absolute value and opposite signs, so the third baseline is sandwiched between the first baseline and the opposite side of the second baseline. To position.

  When a plurality of VCSELs are arranged in this way, the orthogonal projection point from the center of the VCSEL on the second and third baselines to the first baseline and the centers of the plurality of VCSELs on the first baseline are Are all arranged at equal intervals.

  FIG. 3 shows an independent wiring method for each VCSEL of the two-dimensional surface-emitting laser array in the present invention. In the present invention, since the distance between the second and third base lines (2c * sinθ in FIG. 2) is wide, independent wiring of each VCSEL can be easily performed through the interval. When m VCSELs including the VCSEL on the first base line are arranged on the second base line, the relationship c = mb / tan θ is established. Therefore, the interval between the second and third baselines in the present invention is represented by 2 mb * cos θ. That is, since the distance between the second and third base lines increases according to the number of VCSELs on the second and third base lines, independent wiring of individual VCSELs can be easily performed regardless of the degree of integration of the VCSELs. can do. Note that the wiring method shown in FIG. 3 is merely an example, and any method can be used as long as independent wiring of each VCSEL is realized.

  On the other hand, in the two-dimensional surface emitting laser array according to the conventional VCSEL array method shown in FIG. 12, wiring must be performed through a very narrow distance between the VCSELs. Further, since the interval between VCSELs does not change regardless of the degree of integration of VCSELs, when more VCSELs are integrated, the independent wiring becomes increasingly difficult.

  As described above, according to the first embodiment, the second and third base lines that define the angles θ and −θ with respect to the first base line are defined alternately regardless of the degree of integration of the VCSEL in the two-dimensional surface-emitting laser array. By doing so, the interval between the integrated VCSELs can be increased, and independent wiring of each VCSEL can be easily implemented.

  In the two-dimensional surface emitting laser array, there are various problems due to the high integration of VCSELs, one of which is the wiring method of individual VCSELs as described above. The mutual interference of heat generated in the VCSEL can be considered. The heat generated in the active layer induces a decrease in luminous efficiency and lifetime of the active layer itself. In the case where the thermal interference from the adjacent VCSEL cannot be ignored, the characteristic deterioration becomes more remarkable. One effective means for eliminating such thermal interference is to increase the interval between individual VCSELs. However, in the conventional VCSEL arrangement method shown in FIG. 12, the distance between the VCSELs on the second base line can be increased by adjusting the angle formed by the first base line and the second base line. However, with regard to the spacing between the VCSELs on the first baseline and the m-th VCSEL on each second baseline, the spacing between the VCSELs is expanded in consideration of the purpose of use of the two-dimensional surface-emitting laser array. It is difficult to do.

  On the other hand, in the invention shown in the first embodiment, a sufficiently wide interval is used for the intervals between the VCSELs on the same second and third baselines and the m-th VCSELs on the second and third baselines. Although it is possible to ensure, a sufficient wide interval cannot be ensured only for the VCSEL on the first baseline.

  FIG. 4 is a diagram for explaining the second embodiment, and shows a method of arranging VCSELs in a two-dimensional surface-emitting laser array in which intervals between individual VCSELs are secured.

  In FIG. 4, a first base line is defined on the semiconductor substrate, and a plurality of base points are defined on the first base line at equal intervals. Of the plurality of base points defined on the first base line, the second base line so that the angle formed with respect to the first base line is θ from the 2n (n: 0, 1, 2,...) -Th base point. And VCSELs are arranged at equal intervals on the second baseline. At this time, when the orthogonal projection points to the first base line are defined from the centers of the plurality of VCSELs arranged on the second base line, the line segments defined by the 2n and 2n + 1 base points on the first base line Must be arranged so that the orthogonal projection points are equally divided (a in FIG. 4).

  Further, among the plurality of base points defined on the first base line, a third base line is defined so that an angle formed with respect to the first base line passes through the 2n + 1th base point and becomes −θ. VCSELs are arranged at equal intervals on the line. At this time, when the orthogonal projection points to the first base line are defined from the centers of the plurality of VCSELs arranged on the third base line, the line segments defined by the 2n + 1 and 2n + 2 base points on the first base line Must be arranged so that the orthogonal projection points are equally divided. Note that the angles formed by the second and third baselines with respect to the first baseline have the same absolute value and opposite signs, so the third baseline is sandwiched between the first baseline and the opposite side of the second baseline. To position.

  When a plurality of VCSELs are arranged by such a method, the orthogonal projection points from the centers of the VCSELs on the second and third baselines to the first baseline are all arranged at equal intervals.

  By adopting the VCSEL arrangement in this way, it is possible to secure the interval between the individual VCSELs for all the VCSELs in the two-dimensional surface emitting laser. The configuration of each VCSEL and the independent wiring method are the same as in the first embodiment.

  As described above, according to the second embodiment, by not arranging the VCSELs on the first base line, it is possible to increase the interval between all the VCSELs to prevent mutual thermal interference and to prevent deterioration of the characteristics of each VCSEL. Can do.

  FIG. 5 is a diagram for explaining the third embodiment, and shows a configuration of an optical scanning device including the two-dimensional surface-emitting laser array, the collimator lens, the polygon mirror, and the fθ lens of the first or second embodiment. In FIG. 5, the rotation axis of the polygon mirror is set perpendicular to the paper surface, and the first base line of the two-dimensional surface emitting laser array defined in Example 1 or 2 is parallel to the rotation axis of the polygon mirror. That is, it is set perpendicular to the paper surface. The collimator lens is designed to have a size that includes all the laser light emitted from the two-dimensional surface emitting laser array.

  Laser light emitted from the two-dimensional surface-emitting laser array is converted into a parallel beam by a collimator lens, and then scanned in the main scanning direction by a polygon mirror. The scanned laser light is set so that the focal point is obtained at all positions on the photosensitive drum by the fθ lens.

  In actual image formation, laser light scanned by a polygon mirror is scanned from left to right in the figure. At this time, the two-dimensional surface emitting laser array is driven by a drive circuit (not shown) according to image information. When one main scan is completed, sub-scanning starts immediately in synchronization with it. However, since the conventional optical scanning device has only one light source, it is written in one main scan. Since it is one line, the sub-scan is regarded as one line. However, since the present invention has a plurality of light sources (VCSEL), the number of rows corresponding to the number of light sources can be written in one main scan. Accordingly, the number of rows scanned in one sub-scan is similarly implemented for the corresponding number of rows.

  In the present invention, the pitch of the laser beam is an interval indicated by a in FIG. 2, but the beam spot irradiated on the photosensitive drum is not one line, and the mth on the second and third baselines in FIG. The spot from the VCSEL has an offset of ± mb from the spot from the VCSEL on the first baseline. Therefore, when writing image information during main scanning, the offset must be taken into consideration.

  In general, in an optical writing system having an equivalent optical output and polygon mirror rotation speed, when the number of lasers is n, the writing time required for one rotation of the photosensitive drum is 1 / n, which is significantly larger than the conventional one. High speed writing is possible.

  According to the present embodiment, a plurality of lines can be scanned simultaneously with a plurality of laser beams, and a latent image can be formed in a short time.

  FIG. 6 is a diagram for explaining the fourth embodiment, and includes a light receiving element for detecting laser light emitted from the two-dimensional surface emitting laser array, and means for inserting the light receiving element into the optical path. Is shown.

  In general, it has been confirmed that the output of a semiconductor laser gradually decreases with energization, and this phenomenon is more or less applicable to any semiconductor laser. The fluctuation of the laser output appears as uneven electric potential on the photoconductor in the latent image formation, and is finally observed as uneven image density. Therefore, when an image having a uniform density is formed, the laser light output must be made uniform.

  In this embodiment, when the image is formed, it is at a position outside the optical path shown in FIG. 6A, and when the image is not formed, it is inserted at a position inside the optical path shown in FIG. As a result, the laser light emitted from each VCSEL can be detected and measured, and the injection current to each VCSEL can be corrected based on the result, so that the laser light output emitted from each VCSEL can be kept uniform.

  Note that the latent image forming process is the same as that described in the configuration and operation of the third embodiment, and is therefore omitted here.

  FIG. 7 is a diagram for explaining the fifth embodiment. A half mirror that reflects a part of the laser light emitted from the two-dimensional surface emitting laser array and transmits the remaining laser light, and the reflected light are detected. 1 shows an optical scanning device including a light receiving element.

  In the configuration shown in the configuration and operation of Example 4, all the laser light can be used for forming a latent image during image formation, but on the other hand, it is possible to install a light receiving element moving means and improve the positional accuracy of the light receiving element. Therefore, there was a risk that the configuration would be complicated.

  In contrast, in the present embodiment, a part of the laser beam is separated and reflected by the half mirror, and the reflected light is detected by the light receiving element, so that it is emitted from each VCSEL without providing any moving means. It is possible to detect and measure the output of the laser light and to correct the injection current to each VCSEL, that is, to keep the laser light output emitted from each VCSEL uniform.

  Further, according to the present embodiment, it is possible to detect the laser light output even during the formation of the latent image, and even if the laser light output of each VCSEL fluctuates during the latent image formation, the injection current can be detected. Correction and adjustment of laser light output are possible.

  On the other hand, laser light output loss is inevitable because part of the laser light output is always separated and reflected by the half mirror.

  Note that the latent image forming process is the same as that described in the configuration and operation of the third embodiment, and is therefore omitted here.

  FIG. 8 is a diagram for explaining the sixth embodiment, and includes means for enlarging the laser light emitted from the two-dimensional surface emitting laser array at a predetermined magnification and a light receiving element for detecting the enlarged laser light. The optical scanning device characterized by this is shown.

  Although a plurality of laser beams emitted from the two-dimensional surface-emitting laser array used in the present invention are actually emitted, it is difficult to detect them separately because their intervals are narrow. Therefore, when detecting individual laser beams by the methods of Examples 4 and 5, it was necessary to drive them individually.

  On the other hand, in the present embodiment, the beam pitch is expanded by the magnifying lens, so that individual laser beams can be detected separately. In addition, since the laser output of each VCSEL in the two-dimensional surface emitting laser array can be detected simultaneously and independently, the laser light output can be kept uniform.

  In FIG. 7, a magnifying lens is added to the configuration of the fifth embodiment to separate and detect individual laser beams. However, a configuration in which a magnifying lens is added to the configuration of the fourth embodiment may be used. In that case, when the image is formed, it is at a position outside the optical path shown in FIG. 6A, and when the image is not formed, it is interlocked with the light receiving element at a position inside the optical path shown in FIG. Must be inserted.

  Note that the latent image forming process is the same as that described in the configuration and operation of the third embodiment, and is therefore omitted here.

  FIG. 9 is a diagram for explaining the seventh embodiment. In the optical scanning device shown in the third to sixth embodiments, an optical scanning device having a light receiving element at the end in the scanning direction is shown.

  In electrophotography, after main scanning by the polygon mirror in FIG. 9 is completed, image formation is performed by repeatedly scanning the photosensitive drum by a predetermined amount in the sub-scanning direction. Accordingly, the main scanning and the sub-scanning are performed at a predetermined timing. However, a deviation occurs due to uneven rotation of the polygon mirror, and the deviation accumulates during the main scanning for one image, so that a high quality image is obtained. May interfere with formation.

  On the other hand, in this embodiment, a means for detecting the laser beam scanned at the end of the main scanning direction is provided, and the main scanning and the sub scanning are performed by performing the sub scanning in synchronization with the signal of the end of one main scanning. Scanning can be easily synchronized, image quality deterioration due to uneven rotation of the polygon mirror can be prevented, and high-quality image recording can be performed.

  The latent image forming process is the same as that described in the configuration and operation of the third embodiment, except that the sub-scanning is performed with a main scanning end signal obtained from the laser beam detecting means as a trigger. I will omit it here.

  FIG. 10 is a diagram for explaining an embodiment 8, showing an electrophotographic apparatus using the optical scanning device of the embodiments 3 to 7, and showing an electrophotographic forming process using the present invention.

  After the photosensitive drum is uniformly charged by the charging unit, a latent image is formed by the optical scanning device. Since the latent image forming process is the same as that described in the configuration and operation of the third embodiment, it is omitted here. The latent image formed by the electric charge is developed with toner by a developing unit. The toner image is transferred by a transfer unit onto recording paper supplied by a paper supply unit (not shown). The toner image transferred onto the recording paper is heat-fixed by a fixing unit (not shown) to complete the electrophotographic image formation.

  On the other hand, after the latent image on the photosensitive drum to which the toner image has been transferred is erased by the static eliminator unit, the toner remaining on the photosensitive drum is removed by the cleaning unit. By repeatedly executing the above process, in this embodiment, an electrophotographic image can be output continuously and at high speed.

Here, an electrophotographic apparatus including an optical scanning apparatus using the two-dimensional surface-emitting laser array of Example 1 is shown. As shown in FIG. 11, the VCSEL constituting the present embodiment has Al _0.9 Ga _0.1 As / Al _0.3 Ga _0.7 As p-DBR as the first reflecting mirror and AlAs / Al _0.3 Ga _0.7 As n-DBR as the second reflecting mirror. , Using GaInP as a spacer layer, InGaAsP TQW including a GaInP barrier layer as an active layer, an n-GaAs (100) 15 ° off substrate as a semiconductor substrate, an ohmic electrode containing Au, Zn, Cr as a first electrode, a second An ohmic electrode containing Au, Ge, and Ni was used as the electrode. The composition of InGaAsP contained in the active layer is adjusted so that the oscillation wavelength is 780 nm.

  Regarding the arrangement in the two-dimensional surface emitting laser array, when a surface emitting laser array for 4,800 dpi is designed, a in FIG. 2 is uniquely determined to be 5.3 μm. b and θ can be arbitrarily determined as long as the relationship of tan θ = b / a is satisfied. If b = 60 μm, θ = 85 °. When 8 elements are arranged on each of the second and third baselines, c = 42.4 um, and when two second and third baselines are set, the total number of elements included in the two-dimensional surface emitting laser array Will be 32.

  In FIG. 5, when the polygon mirror is a regular hexagon and is rotated at 12,000 rpm, the laser beam reflected by one reflection surface of the polygon mirror is scanned once in the sub-scanning direction. Scanned. Therefore, when using a one-beam laser, it takes about 33 seconds to scan an A4 horizontal size image (39,600 lines), and the output speed at this time is 1.8 sheets / min (A4 horizontal). On the other hand, when the two-dimensional surface emitting laser array (number of light emitting elements: 32) shown in the present embodiment is used, 32 lines can be scanned simultaneously, and the output speed is 58.1 sheets / min.

  As mentioned above, although the Example of this invention was described, it is not limited to the said Example, A various deformation | transformation is possible in the range which does not deviate from the summary.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 f (theta) lens 3 Collimator lens 4 Two-dimensional surface emitting laser ray 5 Polygon mirror 6 Optical scanning device 7 Light receiving element 8 Reflected light 9 Half mirror 10 Magnifying lens 11 Optical sensor 12 Developing unit 13 Toner 14 Charging unit 15 Cleaning unit 16 Static elimination unit 17 Transfer unit 18 Recording paper

JP 11-340570 A JP 11-354888 A Japanese Patent No. 3198909 JP 2000-012973 A JP 2000-022274 A

Claims (8)

A two-dimensional surface-emitting laser array having first and second reflecting mirrors formed on a semiconductor substrate, and an active layer sandwiched between the first and second reflecting mirrors,
A plurality of surface emitting lasers arranged at equal intervals on a first base line defined in a predetermined direction on the semiconductor substrate;
Defines a predetermined angle θ with respect to the first base line through the center of the 2nth (n = 0, 1, 2,...) Surface emitting laser on the first base line. A plurality of surface emitting lasers arranged at equal intervals on the second base line,
Passes through the center of the 2n + 1th (n = 0, 1, 2,...) Surface emitting laser on the first base line, forms a predetermined angle −θ with respect to the first base line, and is a second base line And a plurality of surface emitting lasers arranged at equal intervals on a third base line defined in a predetermined direction on the opposite side across the first base line, and the first base line The center of the surface emitting laser on the base line and the orthogonal projection points from the center of the plurality of surface emitting lasers on the second and third base lines to the first base line are arranged at equal intervals. Two-dimensional surface emitting laser array. A two-dimensional surface-emitting laser array having first and second reflecting mirrors formed on a semiconductor substrate, and an active layer sandwiched between the first and second reflecting mirrors,
A base point defined at equal intervals on a first base line defined in a predetermined direction on the semiconductor substrate, and a 2nth (n = 0, 1, 2,...) On the first base line. A plurality of surface emitting lasers that pass through a base point, form a predetermined angle θ with respect to the first base line, and are equally spaced on a second base line defined in a predetermined direction;
A direction defined by the second base line passing through the 2n + 1th (n = 0, 1, 2,...) Base point on the first base line, forming a predetermined angle −θ with respect to the first base line. Is composed of a plurality of surface emitting lasers arranged at equal intervals on a third base line defined in a predetermined direction on the opposite side across the first base line, and the second and third bases A two-dimensional surface emitting laser array, wherein orthogonal projection points from the center of a plurality of surface emitting lasers on a line to the first base line are arranged at equal intervals. The two-dimensional surface-emitting laser array according to claim 1 or 2,
Means for converting the laser light emitted from the two-dimensional surface-emitting laser array into a parallel beam;
Means for scanning the parallel beam;
Means for converting the scanned parallel beam to obtain a focal point on the same plane;
An optical scanning device comprising: A light receiving element for detecting laser light emitted from the two-dimensional surface emitting laser array;
Means for inserting the light receiving element between the two-dimensional surface-emitting laser array and means for scanning the laser beam;
The optical scanning device according to claim 3, further comprising: A half mirror that reflects part of the laser light emitted from the two-dimensional surface-emitting laser array and transmits the remaining laser light;
A light receiving element for detecting the reflected laser beam;
The optical scanning device according to claim 3, further comprising:   6. The optical scanning device according to claim 4, further comprising means for expanding laser light at a predetermined magnification between the two-dimensional surface-emitting laser array and the light receiving element.   The optical scanning device according to claim 3, further comprising a light receiving element at a scanning end.   An electrophotographic apparatus comprising the optical scanning device according to claim 3.

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