JP4680604B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

The present invention relates to an optical scanning device and an image forming apparatus.

  In image recording in electrophotography, an image forming method using a laser is widely used to obtain high-definition image quality. In the case of electrophotography, a method of forming a latent image by rotating (sub-scanning) the drum while scanning the laser (main scanning) with a polygon mirror in the axial direction of the photosensitive drum is common. is there.

  On the other hand, in the field of image forming apparatuses (electrophotographic field), high definition of images and high speed of output are required. One method for achieving this is to increase the main scanning / sub-scanning speed and increase the output of the laser or to increase the sensitivity of the photoconductor. In order to improve performance, development of a light source or a high-sensitivity photosensitive member accompanying higher laser output, reinforcement of a housing that supports it by speeding up main and sub-scans, and development of a position control method during high-speed scanning, etc. , Many challenges arise, requiring a great deal of cost and time. In addition, when the resolution of an image is doubled for high definition of the image, twice the time is required in both the main scanning and sub-scanning directions. 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 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-beam, the area where the latent image is formed in one main scan is enlarged. When n lasers are used, the latent image is compared with the case where one laser is used. The formation 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 edge-emitting semiconductor lasers on one chip has been proposed in, for example, Patent Document 1 and Patent Document 2, but such a configuration is structurally and costly. Depending on the problem, 4 beams (2 beams × 2, 4 beams × 1) or 8 beams (2 beams × 4, 4 beams × 2) is the limit, and it corresponds to the speeding up of image output that will progress in the future. It is not possible.

  On the other hand, a surface emitting laser element (hereinafter referred to as a VCSEL), which has been actively researched in recent years, can be easily two-dimensionally integrated, and more VCSELs can be two-dimensionally integrated. By devising, it is possible to set the actual beam pitch narrower.

  In order to form a high-quality image using a plurality of laser beams, the uniformity of each laser beam is indispensable. For this purpose, the characteristics of each laser element must be uniform. In the case of a two-dimensional VCSEL array, a large number of VCSELs are manufactured in a dense state. At this time, there is a possibility that variations in the characteristics of the VCSELs in the central part and the peripheral part occur due to the influence of surrounding elements.

  In addition, since the two-dimensional VCSEL array has a narrow pitch and the VCSELs are densely packed, the influence of the thermal and electrical crosstalk of the adjacent VCSEL or the electric wiring for the VCSEL passing through the vicinity is extremely high. The structure is easy to receive. Therefore, the influence of thermal and electrical crosstalk is also easily expected to be different between the central portion and the peripheral portion. As a result, even if the VCSEL has exactly the same characteristics when driven individually, the array When driving at the same time, there is a risk of variations in the characteristics of the central and peripheral elements (VCSEL). Such a phenomenon is likely to hinder the uniformity of the latent image.

For these problems, in Patent Document 3, manufacturing variations are suppressed by forming an equivalent structure around the structure actually used as a VCSEL. The equivalent structure is used only as a dummy element, and is not actually used as a light source, so the effects of thermal and electrical crosstalk are not taken into consideration at all. (In other words, there is a very high possibility that the characteristics of the element (VCSEL) in the central portion and the peripheral portion vary).
JP 11-340570 A JP 11-354888 A JP 2000-114656 A

The present invention can effectively prevent variations in the characteristics of the surface emitting laser elements (VCSEL) in the central portion and the peripheral portion of the surface emitting laser array (that is, the elements in the central portion and the peripheral portion (VCSEL). It is an object of the present invention to provide an optical scanning device and an image forming apparatus that can achieve uniform characteristics.

In order to achieve the above object, the invention according to claim 1 includes a surface emitting laser array in which a plurality of surface emitting laser elements in which emitted laser light has a predetermined plane of polarization are arranged, and the surface emitting laser is further provided. A light source device in which a plurality of heat source elements that emit laser light having a polarization plane different from the polarization plane of the laser light emitted from each surface emitting laser element of the surface emitting laser array are provided around the array; Of the laser light from the apparatus, it comprises polarization means for transmitting only laser light of a predetermined polarization plane emitted from the surface emitting laser element, and scanning means for scanning the laser light. This is an optical scanning device .

According to a second aspect of the present invention, in the optical scanning device according to the first aspect, the surface-emitting laser array is a two-dimensional surface-emitting laser array.

According to a third aspect of the present invention, there is provided the optical scanning device according to the first or second aspect, wherein the optical scanning device includes a light receiving means for detecting a light output of the laser light emitted from each surface emitting laser element of the surface emitting laser array. A control means for controlling an injection current to each surface emitting laser element of the surface emitting laser array based on a light output detection result in the light receiving means; and An insertion means for inserting the laser light emitted from the array into the optical path is further provided.

According to a fourth aspect of the present invention, in the optical scanning device according to the first or second aspect, a part of the laser light emitted from each surface emitting laser element of the surface emitting laser array is reflected and the remaining laser is reflected. Optical means for transmitting light, light receiving means for detecting the light output of the laser light reflected by the optical means, and each surface emitting laser element of the surface emitting laser array based on the detection result of the light output in the light receiving means And a control means for controlling the injection current into.

According to a fifth aspect of the present invention, in the optical scanning device according to the third or fourth aspect, an enlarging means for enlarging laser light at a predetermined magnification is provided between the surface emitting laser array and the light receiving means. Further, it is provided.

The invention of claim 6 is the optical scanning apparatus according to any one of claims 1 to 5, the main scanning end detection means for detecting the main scanning end once in the main scanning direction end Further, the sub-scan is performed in synchronization with the main-scan end detection signal detected by the main-scan end detection means.

The invention of claim 7 wherein is an image forming apparatus characterized by optical scanning device is used according to any one of claims 1 to 6.

According to the first and second aspects of the present invention, the surface emitting laser array includes a surface emitting laser array in which a plurality of surface emitting laser elements each having a predetermined polarization plane of emitted laser light are arranged. around, since it has a light source device that provided a plurality heat source device which emits laser light of different polarization plane is the plane of polarization of the emitted laser light from the surface-emitting laser element of the surface-emitting laser array It is possible to effectively prevent variations in the characteristics of the surface emitting laser elements (VCSEL) in the central portion and the peripheral portion of the surface emitting laser array. That is, the characteristics of the element (VCSEL) in the central portion and the peripheral portion can be made uniform.

In particular, according to the second aspect of the present invention, in the optical scanning device according to the first aspect, the surface-emitting laser array is a two-dimensional surface-emitting laser array, and therefore forms a uniform latent image with high resolution. Is possible.

Further, according to claim 1, according to the second aspect of the invention, transmitting the above light source apparatus, among the laser light from the light source apparatus, only the laser beam of a predetermined polarization plane is emitted from the surface emitting laser element a polarizing means has a scanning means for scanning the laser beam, the light source device, since emits a plurality of laser light uniform in characteristics, a plurality of laser light uniform characteristics A plurality of lines can be scanned simultaneously, and a uniform latent image can be formed easily and quickly (in a short time). In particular, when a two-dimensional surface-emitting laser array is used as the surface-emitting laser array as described in claim 2 , it is possible to form a uniform latent image with high resolution using the two-dimensional surface-emitting laser array.

According to a third aspect of the present invention, in the optical scanning device according to the first or second aspect, the light receiving device detects the light output of the laser light emitted from each surface emitting laser element of the surface emitting laser array. Means for controlling the injection current to each surface emitting laser element of the surface emitting laser array based on the detection result of the light output in the light receiving means, and the light receiving means at a time other than during image formation. An insertion means for inserting the laser light emitted from the light emitting laser array into the optical path is further provided to control the injection current to each surface emitting laser element of the surface emitting laser array by detecting the laser light output. The laser light output from each surface emitting laser element of the surface emitting laser array can be kept uniform, and a uniform latent image can be stably formed.

According to a fourth aspect of the present invention, in the optical scanning device according to the first or second aspect, a part of the laser light emitted from each surface emitting laser element of the surface emitting laser array is reflected and remains. An optical means (for example, a half mirror) that transmits the laser light; a light receiving means that detects a light output of the laser light reflected by the optical means; and the surface emission based on a detection result of the light output in the light receiving means. Control means for controlling the injection current to each surface emitting laser element of the laser array is further provided, and each surface emitting laser element of the surface emitting laser array is detected by detecting the laser light output even during the latent image formation. Since the injection current is controlled, the laser light output from each surface emitting laser element of the surface emitting laser array can be kept uniform, and a uniform latent image can be stably formed. It is possible.

According to a fifth aspect of the present invention, in the optical scanning device according to the third or fourth aspect of the present invention, the laser beam is magnified at a predetermined magnification between the surface emitting laser array and the light receiving means. Since the means is further provided, the laser light output of each surface emitting laser element in the surface emitting laser array can be detected simultaneously and independently, and the laser of each surface emitting laser element in the surface emitting laser array can be detected. The light output can be kept uniform.

Further, according to according to the invention of claim 6, wherein, in the optical scanning apparatus according to any one of claims 1 to 5, the main scanning direction terminating in one main scanning to detect the main scanning end completion detection Means are further provided, and high-quality image formation can be performed in which sub-scanning is performed in synchronization with the main-scanning end detection signal detected by the main-scanning end detection means.

Further, according to the invention of claim 7, wherein, since an image forming apparatus characterized by optical scanning device is used according to any one of claims 1 to 6 (electrophotographic apparatus), Images (electrophotographic images) can be output at high speed.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  In recent years, in the field of electrophotography, there has been a demand for higher image output speed and higher image density. In the past, such demands have been met by increasing the speed of polygon mirrors and improving laser output.

  When performing image formation 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 photoconductor according to image information, and then the photoconductor drum is moved in the subscanning direction. The latent image was formed by repeating the process of scanning one pixel. 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 is a limit to the improvement in the number of revolutions of the polygon mirror and the laser output, and in particular, the former is about 2 to 3 times the 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 in the main scanning direction on the photoreceptor using a polygon mirror, multiple rows (multiple lines) can be simultaneously formed in accordance with the number of lasers in one main scanning. Since scanning can be performed, latent image formation can be realized at higher speed even if the rotation speed of the polygon mirror and the laser output are the same as before. However, edge-emitting semiconductor lasers that have been used in the past are difficult to realize other than a one-dimensional array in the multi-beam structure, and the power consumption is large, so that the output and the lifetime are not reduced due to mutual thermal interference. Is difficult. Even if it is realized, a very complicated process is required, and a significant increase in cost is inevitable 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. Needless to say, when a plurality of single-element edge-emitting semiconductor lasers are used, the number of optical systems is the same as the number of elements, and a significant increase in cost is inevitable.

  On the other hand, as means for simultaneously solving these problems, it is conceivable that a surface emitting laser array (hereinafter referred to as a VCSEL array) in which surface emitting laser elements (hereinafter referred to as VCSEL) are arrayed is used as a writing light source. The VCSEL can take out laser light perpendicularly to the substrate, so that high integration of elements is easy. Further, since the VCSEL has a light emission region that is significantly smaller than that of the edge-emitting laser, the power consumption is 1/10 or less.

  When an arrayed VCSEL, that is, a VCSEL array, is used for image formation, in order to achieve high image density reproducibility, it is important to make the characteristics of each VCSEL uniform. If the characteristics of each VCSEL are non-uniform, density unevenness occurs in the output image and high-quality image formation is prevented.

  In order to form a VCSEL array having uniform characteristics, firstly, improvement in manufacturing uniformity is considered as an issue. More specifically, it is possible to make the mesa diameter uniform in the mesa manufacturing process, or to make the oxidized constriction diameter uniform when an oxide constriction layer is used for the current confinement of the VCSEL.

  Regarding the mesa diameter uniformization, the mesa structure forming method is roughly classified into a dry etching method using RIE, a wet etching method using a sulfuric acid-based etchant, and the like. In either case, the peripheral etching rate tends to be higher than the central portion of the VCSEL array, that is, the peripheral mesa tends to be smaller than the central mesa. When the mesa diameters are different, it is difficult to produce a uniform oxidized constriction diameter in the subsequent current confinement layer production process, and it becomes difficult to ensure sufficient uniformity in the initial characteristics of the peripheral VCSEL and the central VCSEL, There is a risk of preventing high-definition image formation.

  On the other hand, even when a VCSEL array having a uniform mesa diameter can be manufactured by some method, the oxidized constriction diameters of the peripheral VCSEL and the central VCSEL are not uniform even in the subsequent formation of the oxidized constriction structure. There is a possibility. In the case where an AlAs layer is used as the oxidized constricting layer, it is generally known that the peripheral portion of the VCSEL array has a higher oxidation rate than the central portion. That is, in the oxidation confinement process of the VCSEL array, the oxidized constriction diameter in the peripheral portion tends to be smaller than the oxidized constriction diameter in the central portion. That is, the oscillation threshold current of the central VCSEL is likely to be higher than the oscillation threshold current of the peripheral VCSEL.

  As a method of simultaneously solving these problems, a method of arranging a dummy element not used as a light source around a VCSEL array used as a writing VCSEL can be considered, and thereby uniformity in the manufacturing process and uniformity of initial characteristics can be considered. It is possible to ensure the sex.

  However, in consideration of the uniformity of characteristics required for a VCSEL array as a light source for writing, the VCSEL array is repeatedly lit and extinguished in actual image formation. Must be considered. Thermal crosstalk can be considered as the main factor that disturbs the uniformity of characteristics during the operation of the VCSEL array. As long as a plurality of VCSELs are densely arrayed, it is impossible to completely eliminate these factors, and measures must be taken on the assumption that a constant thermal crosstalk always exists.

  That is, when the VCSEL array is, for example, a two-dimensional VCSEL array, the VCSEL present at the center of the VCSEL array is surrounded on all sides by other VCSELs, while the VCSEL array present at the periphery is three-way or two-way Since only the other VCSELs are adjacent to each other, there is a difference in thermal crosstalk between the central VCSEL and the peripheral VCSEL.

  At the time of image formation, there has been a problem that the latent image cannot be made uniform due to variations in the characteristics of the VCSEL array at the center and peripheral elements (VCSEL).

(First form)
The first aspect of the present invention includes a surface emitting laser array in which a plurality of surface emitting laser elements are arranged, and each surface emitting laser element of the surface emitting laser array is disposed around the surface emitting laser array. A light source device comprising a plurality of heat source elements that have the same active layer, can be energized, and do not emit laser light to the outside.

  Here, the surface-emitting laser element generally includes, for example, a first and second reflecting mirrors, an active layer sandwiched between the first and second reflecting mirrors, and a first reflecting mirror on the semiconductor substrate. A first contact layer for injecting current into the active layer through the first reflecting mirror, and an emission port electrically connected to the contact layer and for extracting laser light generated in the active layer A first ohmic electrode and a second ohmic electrode electrically connected to the semiconductor substrate are included.

  The surface emitting laser array may be a one-dimensional surface emitting laser array or a two-dimensional surface emitting laser array.

  In the first embodiment of the present invention, a surface emitting laser array in which a plurality of surface emitting laser elements are arranged is provided, and each surface emitting laser element of the surface emitting laser array is arranged around the surface emitting laser array Since there are a plurality of heat source elements that have the same active layer, can be energized, and do not emit laser light to the outside, the surface emitting laser elements (VCSEL) in the central part and the peripheral part of the surface emitting laser array It is possible to effectively prevent variations in characteristics. That is, the characteristics of the element (VCSEL) in the central portion and the peripheral portion can be made uniform.

  In particular, when the surface emitting laser array is a two-dimensional surface emitting laser array, a uniform latent image with high resolution can be formed.

  FIG. 1 is a diagram showing an example of a light source device according to the present invention. In the example of FIG. 1, a two-dimensional surface-emitting laser array (two-dimensional VCSEL array) is used as a surface-emitting laser array (VCSEL array). In order to make the characteristics of the VCSEL at the periphery of the VCSEL array and the VCSEL at the center of the VCSEL array uniform, heat source elements are arranged around the periphery of the.

  In the example of FIG. 1, the VCSELs are arranged at equal intervals on the first baseline defined on the two-dimensional VCSEL array, and further pass through the center of each VCSEL on the first baseline. They are also arranged at equal intervals on a second base line having a predetermined angle θ with respect to the one base line. At this time, the orthogonal projection points from the center of the VCSEL on the second baseline to the first baseline must be equidistant.

  At the time of image formation, not only the VCSEL but also the heat source element is energized / heated at the same time. Therefore, the thermal crosstalk between the VCSEL at the periphery of the VCSEL array and the VCSEL at the center is equal, Not only the characteristics but also the light emission characteristics during driving can be made uniform. However, the heat source element in the present invention is intended to make the characteristics of each VCSEL of the VCSEL array uniform, and does not contribute to image formation. It must be configured so that the laser beam cannot be extracted.

  The VCSEL has a configuration as shown in FIG. Referring to FIG. 2A, the laser light generated in the active layer by current injection by the first and second ohmic electrodes is resonated and amplified between the first and second ohmic electrodes, and taken out from the emission port. It is.

  On the other hand, in the first embodiment of the present invention, the heat source element has a structure as shown in FIG. 2B or 2C, and has a structure in which laser light cannot be extracted to the outside. ing. That is, in the example of FIG. 2B, the first ohmic electrode is formed on the entire surface of the first reflecting mirror, and no laser light is emitted to the outside. In the example of FIG. 2 (c), heat is generated in the active layer by current injection. However, since the first reflecting mirror is removed, resonance and amplification are not caused, and therefore laser oscillation does not occur and laser is externally emitted. The light cannot be extracted.

  As described above, the heat source element according to the first embodiment of the present invention may have any form as long as it can inject current into the active layer and cannot extract laser light to the outside. Although not limited to the configuration shown in (c), the present invention aims to equalize the thermal crosstalk between the peripheral portion and the central portion of the VCSEL array. It is desirable to have

(Second form)
According to a second aspect of the present invention, there is provided an optical scanning comprising: the light source device according to the first aspect; and scanning means for scanning a laser beam emitted from the surface emitting laser array of the light source device. Device.

  More specifically, the optical scanning device of the second embodiment includes a surface emitting laser array, means for converting laser light emitted from the surface emitting laser array into a parallel beam, and scanning 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.

  FIG. 3 is a diagram showing a specific example of the optical scanning device according to the second embodiment of the present invention. In the example of FIG. 3, the optical scanning device is a two-dimensional VCSEL array, a collimator lens (emitted from a surface emitting laser array). The laser beam is converted into a parallel beam, a polygon mirror (scanning unit), and an fθ lens (a unit that converts the scanned parallel beam so that a focal point is obtained on the same plane).

  In FIG. 3, the rotation axis of the polygon mirror is set perpendicular to the paper surface, and the first base line of the two-dimensional VCSEL array shown in FIG. 1 is perpendicular to the main scanning direction (parallel to the sub-scanning direction). In other words, it is set perpendicular to the paper surface. The collimator lens is designed to have a size that includes all the laser beams emitted from the two-dimensional VCSEL array. 3 is used in an image forming apparatus that scans a laser beam to form an image on a photosensitive drum.

  In the optical scanning device of FIG. 3, the laser light emitted from the two-dimensional VCSEL array is converted into a parallel beam by a collimator lens, and then scanned in the main scanning direction by a polygon mirror as scanning means. 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 VCSEL array is driven by a drive circuit (not shown) according to image information. When one main scan is completed, sub-scanning is started immediately in synchronization with it. However, since the conventional optical scanning apparatus has only one light source, 1 is written in one main scan. Since it is a line, the sub-scan was regarded as one line. On the other hand, 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. Therefore, the number of rows scanned in one sub-scan is similarly implemented for the number of rows corresponding thereto.

  In the present invention, the pitch of the laser beam is the interval indicated by a in FIG. 1, but the beam spot irradiated on the photosensitive drum is not in a line, and the mth beam on the second base line 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 the same 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 becomes possible.

(Third form)
According to a third aspect of the present invention, there is provided a surface-emitting laser array in which a plurality of surface-emitting laser elements in which emitted laser light has a predetermined plane of polarization is arranged, and the surface is arranged around the surface-emitting laser array. A light source device comprising a plurality of heat source elements that emit laser light having a polarization plane different from the polarization plane of laser light emitted from each surface emitting laser element of the light emitting laser array.

  Here, the surface-emitting laser element generally includes, for example, a first and second reflecting mirrors, an active layer sandwiched between the first and second reflecting mirrors, and a first reflecting mirror on the semiconductor substrate. A first contact layer for injecting current into the active layer through the first reflecting mirror, and an emission port electrically connected to the contact layer and for extracting laser light generated in the active layer A first ohmic electrode and a second ohmic electrode electrically connected to the semiconductor substrate are included.

  The surface emitting laser array may be a one-dimensional surface emitting laser array or a two-dimensional surface emitting laser array.

  In the third embodiment of the present invention, the laser light emitted has a surface-emitting laser array in which a plurality of surface-emitting laser elements each having a predetermined plane of polarization are arranged, and the surface is arranged around the surface-emitting laser array. There are multiple heat source elements that emit laser light with a polarization plane different from the plane of polarization of the laser light emitted from each surface emitting laser element of the light emitting laser array. Variations in the characteristics of the surface emitting laser element (VCSEL) can be effectively prevented. That is, the characteristics of the element (VCSEL) in the central portion and the peripheral portion can be made uniform.

  In particular, when the surface emitting laser array is a two-dimensional surface emitting laser array, a uniform latent image with high resolution can be formed.

  In the light source device of the first embodiment described above, the heat source element can be energized without contributing to image formation by making the structure of the heat source element different from that of the VCSEL. However, since the light source device of the first form has different configurations of the VCSEL and the heat source element, conduction of heat generated in the active layer to the adjacent VCSEL, that is, thermal crosstalk with the adjacent VCSEL is different. There is a possibility that the characteristics of all the VCSELs are not uniform.

  On the other hand, in the light source device of the third embodiment, the VCSEL and the heat source element have the same layer configuration, so that the characteristics of all the VCSELs can be made uniform.

  The method of defining the plane of polarization can be performed by devising the mesa shape or the shape of the laser emission port, but can also be performed by other methods.

(4th form)
According to a fourth aspect of the present invention, there is provided the light source device according to the third aspect, and polarization means that transmits only the laser light having a predetermined polarization plane emitted from the surface emitting laser element out of the laser light from the light source device. And a scanning means for scanning with the laser beam.

  More specifically, the optical scanning device of the fourth embodiment includes a surface emitting laser array, means for converting laser light emitted from the surface emitting laser array into a parallel beam, and scanning means for scanning the parallel beam. A polarizer having a function of transmitting only a specific plane of polarization provided between the two-dimensional surface-emitting laser array and the means for scanning the parallel beam, and focusing on the same plane from the scanned parallel beam. Means for converting so as to be obtained.

  FIG. 4 is a diagram showing a specific example of the optical scanning device according to the fourth embodiment of the present invention. In the example of FIG. 4, the optical scanning device includes a two-dimensional VCSEL array, polarizing means (polarizer), collimator lens (surface). The laser beam emitted from the light emitting laser array is converted into a parallel beam, a polygon mirror (scanning unit), and an fθ lens (a unit that converts the scanned parallel beam so that a focal point is obtained on the same plane). ing. In FIG. 4, the rotation axis of the polygon mirror is set perpendicular to the paper surface, and the first base line of the two-dimensional VCSEL array shown in FIG. 1 is perpendicular to the main scanning direction (parallel to the sub-scanning direction). In other words, it is set perpendicular to the paper surface. The polarization means and the collimator lens are designed to have a size that includes all the laser beams emitted from the two-dimensional VCSEL array. 4 is used in an image forming apparatus that scans a laser beam to form an image on a photosensitive drum.

  In the optical scanning device shown in FIG. 4, only laser light having a specific polarization plane is transmitted on the optical path of the laser light emitted from the two-dimensional VCSEL laser array and between the two-dimensional VCSEL laser array and the photosensitive member. By arranging the polarizing means having the above and setting so that only the laser light emitted from the VCSEL is transmitted through the polarizing means, only the laser light emitted from the heat source element can be selectively removed.

  The optical scanning device according to the fourth embodiment has a slightly complicated configuration as compared with the configuration of the optical scanning device according to the second embodiment. As described above, the light scanning device according to the third embodiment is used. Therefore, a more uniform image can be formed as compared with the optical scanning device of the second form using the light source device of the first form.

  In the fourth embodiment, the latent image forming process is the same as that described in the second embodiment.

(5th form)
According to a fifth aspect of the present invention, in the optical scanning device according to the second or fourth aspect, the light receiving means for detecting the light output of the laser light emitted from each surface emitting laser element of the surface emitting laser array, Control means for controlling the injection current to each surface emitting laser element of the surface emitting laser array based on the detection result of the light output in the light receiving means, and the light receiving means from the surface emitting laser array at a time other than image formation An insertion means for inserting the laser light into the optical path of the emitted laser light is further provided.

  FIG. 5 is a diagram showing a specific example of the optical scanning device of the fifth embodiment. In the example of FIG. 5, the optical scanning device includes a VCSEL array (for example, a two-dimensional VCSEL array) in the configuration example of FIG. Light receiving means for detecting the laser light emitted from the VCSEL and insertion means (not shown) for inserting the light receiving means between the VCSEL array and the scanning means (boligon mirror) are further provided.

  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 the example of FIG. 5, the light receiving means is at a position outside the optical path shown in FIG. 5a during image formation. However, when the image is not formed, the light receiving means is placed in the optical path shown in FIG. Inserted in position. Thus, the light receiving means inserted in the optical path detects the optical output of the laser light emitted from each VCSEL of the VCSEL array, and corrects the injection current to each VCSEL based on the result. Thereby, the laser light output emitted from each VCSEL of the VCSEL array can be kept uniform.

  Thus, in the fifth aspect of the present invention, in the optical scanning device of the second or fourth aspect, light reception for detecting the light output of the laser light emitted from each surface emitting laser element of the surface emitting laser array. Means for controlling the injection current to each surface emitting laser element of the surface emitting laser array based on the detection result of the light output in the light receiving means, and the light receiving means at a time other than during image formation. An insertion means for inserting the laser light emitted from the light emitting laser array into the optical path is further provided to control the injection current to each surface emitting laser element of the surface emitting laser array by detecting the laser light output. The laser light output from each surface emitting laser element of the surface emitting laser array can be kept uniform, and a uniform latent image can be stably formed.

  In the example of FIG. 5, the case of applying to the configuration example of FIG. 4 is shown, but the same can be applied to the configuration example of FIG. 3.

(Sixth form)
According to a sixth aspect of the present invention, in the optical scanning device of the second or fourth aspect, a part of the laser light emitted from each surface emitting laser element of the surface emitting laser array is reflected and the remaining laser light is reflected. Optical means (for example, a half mirror) to transmit, light receiving means for detecting the light output of the laser light reflected by the optical means, and each surface emitting laser array based on the detection result of the light output in the light receiving means Control means for controlling the injection current to the surface emitting laser element is further provided.

  FIG. 6 is a diagram showing a specific example of the optical scanning device according to the sixth embodiment. In the example of FIG. 6, each of the VCSEL arrays (for example, two-dimensional VCSEL arrays) in the configuration example of FIG. A half mirror that reflects part of the laser light emitted from the VCSEL and transmits the remaining laser light, and a light receiving means that detects the light output of the laser light reflected by the half mirror are further provided.

  In the configuration of the optical scanning device of the fifth embodiment described above, 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 the light receiving means and improve the positional accuracy of the light receiving means. Therefore, there is a risk that the configuration becomes complicated.

  On the other hand, in the optical scanning device of the sixth embodiment, a laser beam output loss is avoided by separating and reflecting a part of the laser beam by the optical means (half mirror) and detecting the reflected light by the light receiving means. The laser emitted from each VCSEL is detected by detecting the optical output of the laser light emitted from each VCSEL without correcting any moving means (insertion means) and correcting the injection current to each VCSEL. The light output can be kept uniform. Further, according to the sixth embodiment, it is possible to detect the light output even during the formation of the latent image, and even if the laser light output of each VCSEL fluctuates during the formation of the latent image, the injection current Correction and adjustment of the laser light output.

  As described above, in the sixth aspect of the present invention, in the optical scanning device of the second or fourth aspect, a part of the laser light emitted from each surface emitting laser element of the surface emitting laser array is reflected and remains. An optical means (for example, a half mirror) that transmits the laser light; a light receiving means that detects a light output of the laser light reflected by the optical means; and the surface emission based on a detection result of the light output in the light receiving means. Control means for controlling the injection current to each surface emitting laser element of the laser array is further provided, and each surface emitting laser element of the surface emitting laser array is detected by detecting the laser light output even during the latent image formation. Since the current injected into the surface is controlled, the laser light output from each surface emitting laser element of the surface emitting laser array can be kept uniform, and a uniform latent image can be stably formed. Can.

  In the example of FIG. 6, the case of applying to the configuration example of FIG. 4 is shown, but the same can be applied to the configuration example of FIG. 3.

(7th form)
According to a seventh aspect of the present invention, in the optical scanning device according to the fifth or sixth aspect, an enlarging means for enlarging laser light at a predetermined magnification is further provided between the surface emitting laser array and the light receiving means. It is characterized by being.

  FIG. 7 is a diagram showing a specific example of the optical scanning device of the seventh embodiment. In the example of FIG. 7, in the configuration example of FIG. 6, the laser emitted from the VCSEL array between the half mirror and the light receiving means. A magnifying means (for example, a magnifying lens) for magnifying light at a predetermined magnification is provided, and the light receiving means is configured to detect the light output of the laser light magnified by the magnifying means.

  Since each laser beam emitted from each VCSEL of the VCSEL array (two-dimensional VCSEL array) is actually close to each other, when each laser beam is emitted simultaneously from each VCSEL, each laser beam is emitted by the light receiving means. It is difficult to accurately separate and detect. Therefore, in the above-described fifth and sixth embodiments, when detecting the individual laser beams from each VCSEL by the light receiving means, it is necessary to drive each VCSEL of the VCSEL array individually (for example, sequentially).

  On the other hand, in the seventh embodiment, since the beam pitch of the laser light from each VCSEL of the VCSEL array is enlarged by the magnifying means (magnifying lens), each VCSEL is driven at the same time, and the laser light is simultaneously emitted from each VCSEL. Even if is emitted, each laser beam can be accurately separated and detected by the light receiving means.

  In the example of FIG. 7, a magnifying lens is added to the configuration of FIG. 6 to separate and detect individual laser beams. However, a configuration in which a magnifying lens is added to the configuration of FIG. Absent. In that case, when the image is formed, the magnifying lens is located at the position outside the optical path shown in FIG. 5a together with the light receiving means. Must be inserted in a position in the optical path shown in FIG.

(8th form)
According to an eighth aspect of the present invention, in the optical scanning device according to any one of the second, fourth to seventh aspects, a main scanning end detecting means for detecting the end of one main scanning is further provided at the end of the main scanning direction. The sub-scan is performed in synchronization with the main-scan end detection signal detected by the main-scan end detection means.

  FIG. 8 is a diagram showing a specific example of the optical scanning device of the eighth embodiment. In the example of FIG. 8, in the optical scanning device of FIG. 4, an optical sensor as main scanning end detection means is provided at the end of the main scanning direction. Is provided.

  In electrophotography, after main scanning by the polygon mirror (scanning means) in FIG. 8 is completed, image formation is performed by repeatedly scanning the photosensitive drum by a predetermined amount in the sub-scanning direction. Therefore, the main scanning and the sub-scanning are performed at a predetermined timing. However, the timing is shifted due to uneven rotation of the polygon mirror, and the shift is accumulated while the main scanning for one image is completed. There is a risk that high-quality image formation may be hindered.

  On the other hand, in the eighth embodiment, main scanning end detection means (photosensor in FIG. 8) for detecting the scanned laser light is provided at the end of the main scanning direction, and the laser is located at the position indicated by the broken line in FIG. When the light arrives, a single main scanning end signal is emitted from the optical sensor, and by performing sub-scanning in synchronization with the signal (by performing scanning control of the photosensitive drum in the sub-scanning direction), It is possible to prevent deterioration in image quality due to uneven rotation of the polygon mirror, and high-quality image formation can be performed.

  In the eighth embodiment, the latent image forming process is the same as that described in the second embodiment, except that the execution of sub-scanning is triggered by a main scanning end signal obtained from the main scanning end detection means. It is.

  Further, in the example of FIG. 8, the case of applying to the configuration example of FIG. 4 is shown, but the present invention can be similarly applied to the configuration examples of FIGS. 3, 5, 6, and 7.

(9th form)
According to a ninth aspect of the present invention, there is provided an image forming apparatus (electrophotographic apparatus) using the optical scanning device according to any one of the second, fourth to eighth aspects.

  Here, examples of the image forming apparatus include a copying machine, a printer, a facsimile machine, or a multifunction machine of these.

  FIG. 9 is a diagram showing a specific example of the image forming apparatus (electrophotographic apparatus) of the ninth embodiment. In FIG. 9, the optical scanning device includes second, fourth, fifth, sixth, seventh, The optical scanning device of any one of the eighth forms is used.

  The image forming process (electrophotographic forming process) using the image forming apparatus (electrophotographic apparatus) shown in FIG. 9 will be described below.

  In the electrophotographic apparatus of FIG. 9, the photosensitive drum is uniformly charged by the charging unit, and then a latent image is formed by the optical scanning device. The latent image forming process is the same as that described in the second embodiment. After the latent image is formed, the developing unit performs toner development on the latent image formed by the charge. Next, the toner image is transferred by a transfer unit onto a recording sheet supplied by a paper supply unit (not shown). Then, the toner image transferred onto the recording paper is thermally fixed by a fixing unit (not shown), and the electrophotographic image formation is completed. 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, it is possible to output electrophotographic images continuously and at high speed.

Example 1 relates to an image forming apparatus (electrophotographic apparatus) using the optical scanning device of the fourth mode (specifically, the optical scanning device of FIG. 4). As shown in FIG. 10, the VCSEL constituting the light source device includes Al _0.9 Ga _0.1 As / Al _0.3 Ga _0.7 As p-DBR as the first reflecting mirror and AlAs as the second reflecting mirror. / Al _0.3 Ga _0.7 As n-DBR, GaInP as a spacer layer, InGaAsP TQW including a GaInP barrier layer as an active layer, an n-GaAs (100) substrate as a semiconductor substrate, Au, Zn as a first electrode , Cr containing ohmic electrode, and the second electrode using Au, Ge, Ni containing ohmic electrode. Note that the composition of InGaAsP contained in the active layer is adjusted so that the oscillation wavelength is 780 nm.

  Further, regarding the arrangement in the two-dimensional VCSEL array, when a 4,800 dpi VCSEL array is designed, a in FIG. 11 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. For example, when b = 60 μm, θ = 85 °. When four elements are arranged on the second base line (θ = 85 °), c = 21.2 μm, and when eight second base lines are set, the total number of elements included in the two-dimensional VCSEL array is 32 pieces. Become.

  In the example of FIG. 11, each VCSEL in the two-dimensional VCSEL array has an oval shape whose long side is parallel to the first base line, and the heat source element has a long side with respect to the first base line. It has a vertical oval shape.

  On the other hand, the polarization means (polarization element) shown in FIG. 4 has its polarization plane adjusted so that the transmittance of the laser light emitted from the VCSEL is maximized, and at that time, the laser light emitted from the heat source element. Since the polarization plane is perpendicular to the polarization direction of the polarization means, the transmittance is zero.

  In FIG. 4, when the polygon mirror is a regular hexagon and is rotated at 12,000 rpm, the laser beam reflected by one reflecting surface of the polygon mirror is scanned once in the sub-scanning direction. 6 lines are scanned. Therefore, when using a 1-beam laser, it takes about 33 seconds to scan an A4 landscape image (39,600 lines), and the output speed at this time is 1.8 sheets / minute (A4 landscape). . On the other hand, when the two-dimensional VCSEL array (number of light emitting elements: 32) shown in the first embodiment is used, 32 lines can be scanned simultaneously, and the output speed is 58.1 sheets / minute.

When the two-dimensional VCSEL array used in this embodiment is used, the heat source elements are also turned on during image recording, so that the thermal crosstalk between the peripheral and central VCSELs is uniform, and uniform image formation is possible. Become.

It is a figure which shows an example of the light source device which concerns on this invention. It is a figure which shows an example of a surface emitting laser element and a heat-source element. It is a figure which shows the specific example of the optical scanning device of the 2nd form of this invention. It is a figure which shows the specific example of the optical scanning device of the 4th form of this invention. It is a figure which shows the specific example of the optical scanning device of a 5th form. It is a figure which shows the specific example of the optical scanning device of the 6th form. It is a figure which shows the specific example of the optical scanning device of a 7th form. It is a figure which shows the specific example of the optical scanning device of an 8th form. It is a figure which shows the specific example of the image forming apparatus (electrophotographic apparatus) of the 9th form. 1 is a diagram showing a surface emitting laser element used in Example 1. FIG. 1 is a diagram showing a two-dimensional surface emitting laser array used in Example 1. FIG.

Claims (7)

A surface-emitting laser array in which a plurality of surface-emitting laser elements each having a predetermined polarization plane of emitted laser light are arranged, and each surface-emitting laser element of the surface-emitting laser array is provided around the surface-emitting laser array a light source device that provided a plurality heat source device which emits laser light of different polarization plane is the plane of polarization of the laser light emitted from, among the laser beam from the light source device is emitted from the surface emitting laser element An optical scanning device comprising: polarization means that transmits only laser light having a predetermined polarization plane; and scanning means that scans the laser light . The optical scanning apparatus according to claim 1, wherein the surface emitting laser array, an optical scanning device which is a two-dimensional surface emitting laser array. The optical scanning apparatus according to claim 1 or claim 2, wherein a light receiving means for detecting the optical output of the laser light emitted from the surface-emitting laser element of the surface-emitting laser array, the detection result of the light output at the light receiving means Based on the control means for controlling the injection current to each surface emitting laser element of the surface emitting laser array, and the light receiving means on the optical path of the laser light emitted from the surface emitting laser array at a time other than during image formation An optical scanning device, further comprising an insertion means for insertion into the optical scanning device. The optical scanning apparatus according to claim 1 or claim 2, wherein an optical means for transmitting the reflected remaining laser beam a portion of the emitted laser light from the surface-emitting laser element of the surface-emitting laser array, optical means A light receiving means for detecting the light output of the laser light reflected by the light receiving means, and a control means for controlling an injection current to each surface emitting laser element of the surface emitting laser array based on a light output detection result in the light receiving means; Is further provided. 5. The optical scanning device according to claim 3 , further comprising an enlarging means for enlarging laser light at a predetermined magnification between the surface emitting laser array and the light receiving means. Optical scanning device. The optical scanning apparatus according to any one of claims 1 to 5, a main scanning end detection means is further provided for detecting the main scanning end once in the main scanning direction end, the main scanning end detection An optical scanning device characterized in that sub-scanning is performed in synchronization with a main-scanning end detection signal detected by the means. An image forming apparatus comprising the optical scanning device is used according to any one of claims 1 to 6.

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