JP4389735B2 - Optical scanning apparatus and beam waist position adjusting method - Google Patents

Description

  The present invention relates to an optical scanning device and a beam waist position adjusting method. More specifically, the present invention relates to an optical scanning device that divides a plurality of laser beams and scans a plurality of scan objects, and beam waist position adjustment in the optical scanning device. Regarding the method.

  For example, there is an image forming apparatus that uses a plurality of photosensitive members (scanned members) to improve the productivity of color images. For example, Patent Document 1 describes a laser beam printer that can reduce the size and reduce the cost by reducing the number of parts by deflecting a plurality of beams with a single deflector and scanning a plurality of photosensitive members. .

  In order to obtain a good image in such an image forming apparatus, it is necessary that a plurality of laser beams for scanning each photoconductor be imaged satisfactorily on each photoconductor, preferably with a uniform spot diameter. is there.

  In general, the imaging position on the surface to be scanned can be adjusted by adjusting the relative position of the laser and the collimating lens. However, in the configuration described in Patent Document 1, the collimating lens is commonly used for a plurality of laser beams. Therefore, only one point on one photoconductor among a plurality of photoconductors can be adjusted for image formation. In other words, since different positions on the other photoconductors or the same photoconductor are changed in accordance with the one-point image formation adjustment, there is a problem that a difference in beam diameters on a plurality of photoconductors becomes large.

  On the other hand, Patent Document 2 discloses a laser light generator provided with an adjusting means for making the spot diameters on the surface to be scanned substantially uniform by collimating all the laser beams from the semiconductor laser array substantially uniformly. Is described.

However, the laser beam generator described in Patent Document 2 does not consider scanning a plurality of different photoconductors. Even if the laser beams are configured to scan a plurality of different photoconductors, the laser beam generator is not provided for each beam. Therefore, there is a problem that the image forming position difference due to the error of these optical systems cannot be corrected.
JP-A-6-286226 JP-A-6-250126

  In view of the above facts, the present invention reduces the variation in spot diameter on each scanned object in an optical scanning device that scans a plurality of scanned objects by separating a plurality of laser beams emitted from the light source unit. Is an issue.

  According to the first aspect of the present invention, a light source unit having a plurality of light emitting points, a pre-deflection optical system that is commonly arranged for a plurality of laser beams emitted from the plurality of light emitting points of the light source unit, and the deflection Deflection means arranged in common to a plurality of laser beams that have passed through the previous optical system, a scanning optical system arranged in common to the laser beams deflected by the deflection means, and a plurality of laser beams Separating means for scanning so as to scan on the scanning object, optical elements provided corresponding to the plurality of laser beams, and the maximum spot diameter of each laser beam on the scanning objects And image forming adjustment means for adjusting so as to be substantially the same in any one set of a plurality of scanned objects.

  In this optical scanning device, a plurality of laser beams emitted from a plurality of light emitting points of the light source unit are deflected by the deflecting unit through the pre-change optical system. Further, the plurality of laser beams are separated by a separating unit through a common scanning optical system, and are incident on optical elements provided corresponding to the respective laser beams.

  The imaging adjustment means adjusts so that the maximum spot diameter of each laser beam on the plurality of scanned objects is substantially the same in any one of the plurality of scanned objects. That is, one set of laser beams adjusted by the imaging adjustment means has a maximum spot diameter on the scanning target, and the spot diameters of the other laser beams are equal to or less than the maximum spot diameter. . As a result, the variation in spot diameter is reduced, and a good laser beam can be obtained for all the scanning objects.

  According to a second aspect of the present invention, in the first aspect of the present invention, the imaging adjustment means can adjust a spot diameter based on spot diameters at a plurality of locations on each of the plurality of scanned objects. It is characterized by.

  As described above, the spot diameter can be adjusted based on the spot diameters at a plurality of locations on the scanned object, and can be set to a spot diameter within a predetermined variation without depending on the scanning position on the scanned object. Further, the variation in spot diameter can be suppressed regardless of the accuracy of the members constituting the optical scanning device.

  According to a third aspect of the present invention, a light source unit having a plurality of light emitting points, a pre-deflection optical system that is commonly arranged for a plurality of laser beams emitted from the plurality of light emitting points of the light source unit, and the deflection Deflection means arranged in common to a plurality of laser beams that have passed through the previous optical system, a scanning optical system arranged in common to the laser beams deflected by the deflection means, and a plurality of laser beams Separating means for separating so as to scan on the scanning object, optical elements provided corresponding to each of the plurality of laser beams, and the maximum beam of each laser beam with respect to the scanning surface on the plurality of scanning objects And image forming adjustment means for adjusting the waist shift so that the waist shift is substantially the same and has a different sign in any one of the plurality of scanned objects.

  In this optical scanning device, a plurality of laser beams emitted from a plurality of light emitting points of the light source unit are deflected by the deflecting unit through the pre-change optical system. Further, the plurality of laser beams are separated by a separating unit through a common scanning optical system, and are incident on optical elements provided corresponding to the respective laser beams.

  The imaging adjustment means adjusts so that the maximum beam waist deviation of each laser beam with respect to the scanning surface on the plurality of scanning objects is substantially the same and has a different sign in any one of the plurality of scanning bodies. That is, there is one set of laser beams adjusted by this imaging adjustment means, the maximum beam waist deviation being substantially the same and different signs on the scanned object, and the beam waist deviation of the other laser beams is The maximum beam waist deviation is below. As a result, the beam waist deviation is reduced, and a good laser beam can be obtained for all scanned objects.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the imaging adjustment means can adjust a beam waist deviation based on a plurality of beam waist diameters in each of the plurality of scanned objects. It is said that it is said.

  In this way, adjustment is made based on beam waist deviations at a plurality of locations on the scanned body, and the spot diameter can be made within a predetermined variation without depending on the scanning position on the scanned body. Further, the variation in spot diameter can be suppressed regardless of the accuracy of the members constituting the optical scanning device.

  In the first to fourth aspects of the invention, examples of the pre-deflection optical system include at least a coupling lens. In this configuration, as described in claim 5, the imaging adjustment means can be configured such that the relative position between the light source unit and the coupling lens can be adjusted.

  In a sixth aspect of the present invention, a light source unit having a plurality of light emitting points, a pre-deflection optical system that is commonly arranged for a plurality of laser beams emitted from the plurality of light emitting points of the light source unit, and the deflection Deflection means arranged in common to a plurality of laser beams that have passed through the previous optical system, a scanning optical system arranged in common to the laser beams deflected by the deflection means, and a plurality of laser beams Separating means for scanning so as to scan on the scanning object, optical elements provided corresponding to the plurality of laser beams, and beams between the laser beams for the scanning surfaces on the scanning objects And a waist displacement minimizing means for minimizing waist displacement.

  In this optical scanning device, a plurality of laser beams emitted from a plurality of light emitting points of the light source unit are deflected by the deflecting unit through the pre-change optical system. Further, the plurality of laser beams are separated by a separating unit through a common scanning optical system, and are incident on optical elements provided corresponding to the respective laser beams.

  The waist deviation minimizing means minimizes the beam waist deviation between the laser beams with respect to the scanned surface on the plurality of scanned objects. Thereby, the beam waist shift between the laser beams is reduced, and a good laser beam can be obtained for all the scanning objects.

  According to a seventh aspect of the invention, in the sixth aspect of the invention, the waist deviation minimizing means corrects an inclination of an approximate curve obtained by approximating beam waist positions in the plurality of scanned objects. By doing so, the beam waist shift is minimized.

  In this optical scanning device, for example, the beam waist position can be adjusted by the beam waist position adjusting method of claim 13.

  That is, first, in the beam waist position detecting step, each beam waist position in a plurality of scanned objects is detected. Then, in the approximate straight line calculating step, the approximate straight line is calculated from each detected beam waist position. In the first adjustment step, a relative difference in waist position deviation is adjusted so that the approximate straight line is parallel to an ideal straight line connecting the scanned positions of the plurality of scanned objects. Further, in the second adjustment step, the approximate straight line is slid so as to approach the ideal straight line.

  In the invention according to claim 6 or claim 7, the pre-deflection optical system may include at least a coupling lens. In this configuration, as described in (85), the waist deviation minimizing means can be configured such that a relative angle between the light source unit and the coupling lens can be adjusted.

  The invention according to claim 9 is the invention according to any one of claims 6 to 7, wherein the scanning optical system includes the waist deviation minimizing means. To do.

  As a result, since the waist deviation minimizing means can be configured by the scanning optical system which is a single optical system, the structure becomes simple.

  In the invention according to claim 10, the light source unit having a plurality of light emitting points, the pre-deflection optical system arranged in common for the plurality of laser beams emitted from the plurality of light emitting points of the light source unit, and the deflection Deflection means arranged in common to a plurality of laser beams that have passed through the previous optical system, a scanning optical system arranged in common to the laser beams deflected by the deflection means, and a plurality of laser beams Separating means for scanning so as to scan on the scanning object, optical elements provided corresponding to the plurality of laser beams, and beams between the laser beams for the scanning surfaces on the scanning objects A waist deviation minimizing means for minimizing a waist deviation, and an imaging adjustment means for shifting a beam waist deviation of each laser beam on the plurality of scanning objects.

  In this optical scanning device, a plurality of laser beams emitted from a plurality of light emitting points of the light source unit are deflected by the deflecting unit through the pre-change optical system. Further, the plurality of laser beams are separated by a separating unit through a common scanning optical system, and are incident on optical elements provided corresponding to the respective laser beams.

  The beam waist deviation between the respective laser beams with respect to the scanning surfaces on the plurality of scanned objects is minimized by the waist deviation minimizing means. Further, the beam waist shift of each laser beam is shifted by the image adjusting means. As a result, a good laser beam can be obtained on all the scanning objects.

  In the invention described in claim 11, a multi-beam light source in which a plurality of light sources are two-dimensionally arranged, and a pre-deflection optical system that is arranged in common for a plurality of laser beams emitted from a plurality of light emitting points of the multi-beam light source A deflection means for commonly deflecting the laser beams that have passed through the pre-deflection optical system, a scanning optical system that is commonly disposed for the laser beams deflected by the deflection means, and a plurality of Separating means for separating the laser beam into a plurality of beam groups and separating each of the beam groups so as to scan on the scanned object, an optical element provided corresponding to each of the plurality of beam groups, and the beam The beam waist position of the laser beam at the center of the array among the plurality of laser beams constituting the group is set as the representative beam waist position representing this beam group, and the representative beam waist position And a waist deviation adjusting means that adjusts so that the maximum beam waist deviation of each beam group is substantially the same and has a different sign in any one of a plurality of scanned objects. .

  In this optical scanning device, a plurality of laser beams emitted from a plurality of light emitting points of a multi-beam light source are deflected by a deflecting unit through a pre-change optical system. Further, the plurality of laser beams are separated by the separating means through a common scanning optical system. In the separating means, a plurality of laser beams are separated into a plurality of beam groups and incident on optical elements provided corresponding to the respective beam groups, and then the laser beams are scanned on the scanned object for each of these beam groups. The

  Here, the beam waist position of the laser beam at the center of the array among the plurality of laser beams constituting the beam group is set as a representative beam waist position representing this beam group. Then, the waist deviation adjusting means uses the representative beam waist position to adjust the maximum beam waist deviation of each beam group so as to be substantially the same and have the same sign in any one of the plurality of scanned objects. In this way, by determining the representative beam waist position and using it, even an optical scanning device that scans a plurality of scanned objects by forming a beam group with a plurality of laser beams can be effectively all. A good laser beam can be obtained on the object to be scanned.

  The invention according to claim 12 is a multi-beam light source in which a plurality of light sources are two-dimensionally arranged, and a pre-deflection optical system that is commonly arranged for a plurality of laser beams emitted from a plurality of light emitting points of the multi-beam light source. A deflection means for commonly deflecting the laser beams that have passed through the pre-deflection optical system, a scanning optical system that is commonly disposed for the laser beams deflected by the deflection means, and a plurality of Separating means for separating the laser beam into a plurality of beam groups and separating each of the beam groups so as to scan on the scanned object, an optical element provided corresponding to each of the plurality of beam groups, and the beam The center position of the beam waist position error among the multiple laser beams that make up the group is the representative beam waist position that represents this beam group, and the representative beam waist position is used. , Maximum beam waist displacement of each beam group, and having a waist shift adjustment means for adjusting so that the opposite sign at approximately the same in any one set of a plurality of scanned body.

  In this optical scanning device, a plurality of laser beams emitted from a plurality of light emitting points of a multi-beam light source are deflected by a deflecting unit through a pre-change optical system. Further, the plurality of laser beams are separated by the separating means through a common scanning optical system. In the separating means, the plurality of laser beams are separated into a plurality of beam groups, and are incident on optical elements provided corresponding to the respective laser beams. The laser beam is scanned on the object to be scanned for each beam group.

  Here, the center position of the beam waist position error among the plurality of laser beams constituting the beam group is set as a representative beam waist position representing this beam group. Then, the waist deviation adjusting means uses the representative beam waist position to adjust the maximum beam waist deviation of each beam group so as to be substantially the same and have the same sign in any one of the plurality of scanned objects. In this way, by determining the representative beam waist position and using it, even an optical scanning device that scans a plurality of scanned objects by forming a beam group with a plurality of laser beams can be effectively all. A good laser beam can be obtained on the object to be scanned.

  Since the present invention is configured as described above, in an optical scanning device that scans a plurality of scanned objects by separating a plurality of laser beams emitted from the light source unit, it is possible to reduce variations in spot diameters on the scanned objects.

 FIG. 1 shows the overall configuration of an optical scanning device 102 according to the first embodiment of the present invention. 2 and 3 show the light source device 104 of the first embodiment constituting the optical scanning device 102. In the following drawings, the main scanning direction is indicated by an arrow M, and the sub-scanning direction is indicated by an arrow S.

  As shown in FIG. 1, the optical scanning device 102 includes a multi-beam light source 110 having a plurality of light emitting points. A plurality of laser beams emitted from the multi-beam light source 110 are collected by a single coupling lens 112, pass through a common pre-deflection optical system 114, and have a single deflector 116 having a plurality of reflecting surfaces. Is incident on. The plurality of beams are deflected by the movement of the reflecting surface by the rotation of the deflector 116, and are subjected to an imaging action by a scanning lens (scanning optical system) 118 common to each laser beam, and are given an fθ characteristic.

  The deflected plural beams are separated by the separation mirror 120, and after being folded by the folding mirrors 122A to 122D specific to each laser beam, a plurality of photosensitive beams are passed through the cylinder mirrors 124A to 124D having power in the sub-scanning corresponding direction. An image is formed on the bodies 126A to 126D to form spots.

  The laser beam that scans each of the photoconductors 126A to 126D is independently modulated to form a latent image on each photoconductor. Then, it is visualized in different colors by a developing device (not shown), and further transferred to a recording medium (not shown) to form a multi-color image (for example, a color image).

  As shown in FIGS. 2 and 3, the multi-beam light source 110 is mounted on the laser control board 108 and is attached to the housing 106 via fixed support points 130 and 132 and an adjustment support point 128. Here, by adjusting the adjustment support point 128, the support point moves in the optical axis direction, and the light source tilts up and down. Further, the image formation position adjustment (shift adjustment) can be performed by moving the coupling lens 112 in the optical axis direction along the holding portion 106H of the housing 106.

  An aperture 134 is disposed behind the coupling lens 112, and is shaped so that the laser beam has a desired shape.

  FIG. 4 conceptually shows an example of the beam waist position and spot diameter in the optical scanning device 102 of the present embodiment. The beam waist position indicates a position where the minimum spot diameter is obtained when the laser beam is imaged.

  Here, not only the wavelength difference of the laser beam but also the position variation and power variation of the cylinder mirrors 124A to 124D, the beam waist position may be shifted by ΔAc, ΔBc, ΔCc, ΔDc on the scanned surface. The maximum value is ΔZmax (ΔAc) and the minimum value is ΔZmin (ΔDc), and the front side and the rear side are asymmetric with respect to the surface to be scanned. In addition, the spot diameter on the photoconductor 126A is large, the spot diameter on the photoconductor 126C is small, and the entire photoconductor has an uneven spot diameter. As described above, since a desired image formation state (beam waist position and spot diameter) is not achieved in the photoconductors 126A to 126D, it is difficult to obtain a good color image.

  In this embodiment, the spot diameter of each laser beam is observed at each of the scanning positions Ac, Bc, Cc, and Dc on the plurality of photoconductors 126A to 126D, and the coupling lens 112 is illustrated based on the value. 2 Move in the direction of arrow A. Because of this movement, the spot diameters of the respective photoconductors 126A to 126D change. Therefore, any one of a plurality of photoconductors, that is, two photoconductors, is adjusted to have the maximum spot diameter. Therefore, of the plurality of photoconductors, the spot diameters of the two photoconductors are the same and the maximum size, and the other two photoconductors have a spot diameter of the maximum size or less.

  FIG. 5A shows the state of spot images on the photoconductors 126A to 126D. FIG. 5B shows the relationship between the position on the surface to be scanned and the spot diameter. In FIG. 5A, a broken line indicates before adjustment according to the present embodiment, and a solid line indicates after adjustment. The distance between the broken lines or the distance between the solid lines at the positions where the broken lines or the solid lines intersect with the photoconductors 126A to 126D substantially indicates the spot diameter. As can be seen from the above, in the above example, the difference between the spot diameter on the photoconductor 126A and the spot diameter on the photoconductor 126C is large, and the spot diameters on the photoconductors 126A to 126D are uneven.

  On the other hand, in the present embodiment, as indicated by a solid line in FIG. 5A, the maximum spot diameter Wmax is adjusted on the two scanned surfaces of the photoconductor 126A and the photoconductor 126C. Spot diameters of Wmax or less can be realized on the scanned surfaces of the other photoreceptors 126B and 126D, and variations in spot diameters on the scanned surfaces can be reduced.

  Note that, as in this embodiment, if each laser beam has an independent optical system (folding mirrors 122A to 122D, cylinder mirrors 124A to 124D, etc.), the optical magnification differs for each optical system, and the beam waist The minimum spot diameter at the location may be different. However, even if the minimum spot diameters are different in this way, in this embodiment, it is possible to reduce variations in spot diameters on the surface to be scanned.

The spot diameter can be observed by the method shown in FIG. 6, for example. In this method, an output from the light amount detector 138 is taken on the surface to be scanned through the slit 136, and the slit 136 is moved in a predetermined direction (X direction) on the surface to be scanned as shown in FIG. A light intensity distribution can be obtained. In the present embodiment, with respect to the peak intensity P, the intensity width P × 1 / e ² is defined as the spot diameter. FIG. 7 also shows that the spot diameter W1 after adjustment is smaller than the spot diameter W2 before adjustment indicated by the broken line, and the spot diameter is made uniform.

  As described above, in the present embodiment, by performing appropriate image formation adjustment, the spot diameters on the plurality of scanned surfaces can be made closer to a uniform state, and a good color image can be obtained.

  Next, a second embodiment of the present invention will be described. In the second embodiment, the basic configuration of the optical scanning device is substantially the same as that of the first embodiment shown in FIG. 1, but in addition to the image formation adjustment of the first embodiment, a plurality of photoconductors 126A to 126D. The spot diameters are observed at different scanning positions As, Ac, Ae / Bs, Bc, Be / Cs, Cc, Ce / Ds, Dc, De (see FIG. 1). Here, the subscripts s, c, and e indicate the scan start position, the scan center position, and the scan end position, respectively. Then, the coupling lens 112 is adjusted so that the maximum spot diameter is substantially the same for any one of the plurality of photoconductors.

  In this way, by adjusting the image formation based on the spot diameters at a plurality of scanning positions, manufacturing errors of the scanning lens 118 and optical elements for each laser beam (folding mirrors 122A to 122D, cylinder mirrors 124A to 124D, etc.) Variations in spot diameter due to assembly errors can be eliminated, and spot diameters with less variation can be obtained at all positions of each scanned object.

  Next, a third embodiment of the present invention will be described. In the third embodiment, the basic configuration of the optical scanning device is substantially the same as that of the first embodiment shown in FIG. 1, but at each of the scanning positions Ac, Bc, Cc, Dc of the plurality of photoconductors 126A to 126D. The difference is that the beam waist position of each laser beam is observed, and the coupling lens 112 is moved in the direction of arrow A in FIG. Due to this movement, the beam waist position of each laser beam is also moved, so that the maximum beam waist deviation of each laser beam is substantially the same and has a different sign in any one of the plurality of scanned objects. Adjust.

  FIG. 8A shows the state of spot images on the photoconductors 126A to 126D. FIG. 8B shows the relationship between the position on the surface to be scanned and the spot diameter. As shown in FIGS. 4A and 4B, the beam waist position deviation Zmax on the photoconductor 126A and the beam waist position deviation Zmax on the photoconductor 126C are equal to each other (that is, so-called on the photoconductor 126A). The focus position is adjusted to the rear side, and the photosensitive member 126C is adjusted to move the focus position to the front side).

  As a result, the spot diameters on the four photoconductors 126A to 126D are equal to or smaller than the spot diameter Wmax of the photoconductor 126A or the photoconductor 126C, so that a good image can be obtained.

The measurement of the beam waist position can be performed by moving the knife edge 140 provided with the light amount detector 138 in two places separated by a predetermined distance 2Δ in parallel with the surface to be scanned as shown in FIG. When the knife edge 140 is moved at the speed T, the output of the light quantity detector 138 becomes as shown by the broken line in FIG. 16, and by differentiating this with time, a waveform corresponding to the beam intensity distribution is obtained as shown by the solid line in FIG. can get. The width W of 1 / e ² intensity corresponds to the spot diameter with respect to the peak P of the intensity distribution. As shown in FIG. 17A, the width W changes along the optical axis direction. The center of the position where the spot diameters obtained from two knife edges 140 separated by a predetermined distance 2Δ are the same is the beam waist position, and the beam intensity distribution there is the minimum spot diameter as shown in FIG. Wmin.

  In this example, the knife edge 140 is moved. However, even when the laser beam is moved (that is, scanned) with respect to the knife edge, measurement can be performed by the same principle. Also, the spot diameter can be measured using the slit 136 shown in FIG.

  Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, the basic configuration of the optical scanning device is substantially the same as that of the first embodiment shown in FIG. 1, but different scanning positions As, Ac, and Ae for each of the plurality of photoconductors 126A to 126D. The beam waist position is observed at / Bs, Bc, Be / Cs, Cc, Ce / Ds, Dc, and De, and the maximum value of the beam waist position deviation from the scanned surface is substantially the same at any one of the observation positions. The coupling lens 112 is adjusted so as to have different signs.

  FIGS. 12A and 12B show the image formation state of each scanning object adjusted based on the beam waist position only at one place (position Ac in this example) on the scanning surface. Yes. In such an adjustment method, the minimum spot diameter can be obtained at the position Ac, but each beam waist position shift occurs at other positions. For example, the beam waist position shift at the position Ds in the photoreceptor 126D becomes considerably large, and the spot diameter Wmax at the position Ds also becomes larger than a desired spot diameter.

  On the other hand, in the present embodiment, on each scanned surface, based on the beam waist positions at a plurality of locations, the maximum value of the beam waist position deviation is substantially the same and has a different sign at any one of the observation positions. adjust. For example, as shown in FIG. 13, the maximum beam waist position deviation ΔBc on the surface to be scanned on the photoconductor 126B (this is the surface to be scanned (126B), the same applies) and the surface to be scanned on the photoconductor 126D. Adjustment is made so that the maximum beam waist position deviation ΔDs is substantially the same and has a different sign. By adjusting in this way, the maximum spot diameter Wmax can be made smaller than the desired spot diameter. For this reason, not only the beam waist difference between the photosensitive members but also the beam waist difference due to the manufacturing error or assembly error of the scanning lens 118 or each optical element for each laser beam, that is, the image formation adjustment considering the curvature of field. Thus, a spot diameter with little variation can be obtained at all positions of each photoconductor.

  Next, a fifth embodiment of the present invention will be described.

  14A and 14B show the configuration of the optical scanning device 152 of the fifth embodiment. Also in the fifth embodiment, a plurality of laser beams are emitted from the multi-beam light source 110 as in the first embodiment. The light emitting points for emitting the plurality of laser beams are arranged at a distance of L1 or L2 from the optical axis of the coupling lens 112. The laser beam is scanned through a common deflector 116 and a scanning lens (not shown in FIG. 14, refer to FIG. 4), and folding mirrors 122A to 122D and cylinder mirrors (optical elements) provided for each of the plurality of laser beams. Through 124A to 124D, images are formed on the plurality of photosensitive members 126A to 126D to form spots.

  Here, assuming that the beam waist position deviation on each of the photoconductors 126A to 126D is ΔAc, ΔBc, ΔCc, and ΔDc, in this embodiment, a straight line (approximate straight line AL) that approximates the beam waist position deviation amount is used as the photoconductor. By adjusting the imaging position so as to coincide with 126A to 126D, the beam waist difference in each of the photoconductors 126A to 126D is reduced to obtain a uniform spot diameter. In order to reduce the beam waist difference, the multi-beam light source 110 is tilted with respect to the optical axis of the coupling lens 112 as shown in FIG. As a result, the beam waist position on the photoreceptor (scanned surface) is inclined.

  FIGS. 15A and 15B show how the image formation position is adjusted by tilting the beam waist position on the photoconductor in this manner. A distance Li × βi (where i is 1 to 4) obtained by multiplying the beam waist position deviations ΔAc, ΔBc, ΔCc, ΔDc on the respective photoconductors 126A to 126D and the distance from the optical axis in the multi-beam light source 110 by the magnification of the optical system. Natural number) is calculated, and an approximate straight line AL is obtained by the least square method or the like. Then, by adjusting the inclination of the multi-beam light source 110, the approximate straight line AL is adjusted to be a straight line BL parallel to the surface to be scanned.

  Thereafter, when the shift adjustment by the movement of the coupling lens 112 described above is performed, the approximate straight line AL coincides with the surface to be scanned. Since the waist position deviation on each scanned surface from the scanned surface is minimized, a uniform spot diameter less than a desired diameter can be obtained.

  Further, as shown in FIG. 16A, even when there is a beam waist position difference on the same photoconductor, that is, when there is a field curvature, detection is performed at a plurality of locations on the same scanning body to correct the field curvature. It is also possible. That is, as shown in detail in FIG. 9B, the beam waist position deviation at the center of scanning is normalized, and the inclination of the image plane is calculated from the waist position deviation at both ends. Based on this, rotation of the common scanning lens 118 (see FIG. 1) in the direction of the arrow R1 corrects the inclination of the image plane, and the waist shift with respect to the scanning center is minimized.

  Thereafter, by correcting the above-described waist deviation for each surface to be scanned, it is possible to obtain a spot diameter with little variation at all the positions of the photosensitive members 126A to 126D.

  Particularly, in the case of a configuration in which a plurality of laser beams emitted from a single multi-beam light source 110 are separated and a plurality of photosensitive members are scanned as in the present embodiment, the pitch between the plurality of laser beams in the multi-beam light source 110 is 100 μm. To 500 μm, and the beam waist difference on the scanned surface also increases. Therefore, it is particularly effective to perform the above-described image position adjustment.

  In the above description, the multi-beam light source 110 is tilted, but the same effect can be obtained by tilting the coupling lens 112.

  Next, a sixth embodiment of the present invention will be described. As shown in FIGS. 17 and 18, in the sixth embodiment, a plurality of light emitting points of the multi-beam light source 110 are two-dimensionally arranged, and a plurality of beams emitted from the plurality of light emitting points are divided, A plurality of beam groups GA, GB, GC, GD are formed. Each of the laser beams of these beam groups scans one of a plurality of corresponding scanning objects. For example, as shown in FIG. 18, if each light emitting point in m rows and n columns is given a number Ch (m, n), the light emitting points Ch (1, 1) to Ch (1, n) whose row number is 1 are used. ), One beam group is formed. Similarly, a beam group is formed for each light emitting point whose row number is 2, 3,..., M.

  In this way, when the plurality of photosensitive members 126A to 126D are scanned for each beam group, an imaging position difference between different laser beams occurs even at the same scanning position of the same scanning body. This is largely because the two-dimensional light source is inclined with respect to the plane orthogonal to the optical axis of the coupling lens 112 as shown in FIG.

  Thus, when an imaging position difference occurs even at the same scanning position of the same photosensitive member, when the laser beam is emitted from the coupling lens 112, a laser beam in a direction approaching the coupling lens 112 (for example, a light emitting point Ch) is generated. (The light beam corresponding to (1, 1)) becomes diffused light, and the laser beam in the direction away from the light beam (for example, light beam corresponding to Ch (1, 5)) becomes convergent light, so that there is a waist difference on the surface to be scanned. appear. In contrast, in the present embodiment, image formation adjustment is performed with reference to the position near the optical axis, that is, the waist position of the laser beam at the center of the array of light emitting points. As a result, as shown in FIG. 19A, it is possible to reduce the variation in spot position on the scanning target due to the waist difference.

  Further, when there is an imaging position difference due to a wavelength difference between the laser beams, adjustment with the laser beam from the light emission point at the center of the array is not always good, but in this case, as shown in FIG. As described above, the waist position of each laser beam is measured, and the center of the beam having the maximum waist shift is set as the waist position of the beam group, and image formation adjustment is performed to reduce the above-described waist position shift between the plurality of photoconductors. Thereby, all the laser beams are within a predetermined waist position deviation, and the variation in spot diameter can be reduced.

1 is a schematic perspective view illustrating an overall configuration of an optical scanning device according to a first embodiment of the present invention. It is sectional drawing of the light source device which shows the image formation adjustment means of the optical scanning device of 1st Embodiment of this invention. It is a perspective view of a light source device showing an imaging adjustment means of the optical scanning device according to the first embodiment of the present invention. It is explanatory drawing which shows the waist position between several beams in the optical scanning device of 1st Embodiment of this invention. It is explanatory drawing for demonstrating the image formation position adjustment in the optical scanning device to 1st Embodiment of this invention. It is explanatory drawing which shows the specific method for observing the spot diameter of a laser beam. It is a graph which shows the relationship between the intensity distribution of a laser beam, and a spot diameter. It is explanatory drawing for demonstrating the image formation position adjustment in the optical scanning device to 3rd Embodiment of this invention. It is explanatory drawing which shows the specific method for observing the beam waist position of a laser beam. It is a graph which shows the relationship between the intensity distribution of a laser beam, and a beam waist position. It is explanatory drawing which shows the beam waist position of a laser beam. It is explanatory drawing which shows the image formation state in each to-be-scanned body adjusted based on the beam waist position of only one place on a to-be-scanned surface for the comparison with 4th Embodiment of this invention. It is explanatory drawing explaining the beam waist position adjustment in the optical scanning device of 4th Embodiment of this invention. It is explanatory drawing which shows schematic structure of the optical scanning device of 5th Embodiment of this invention, (A) is before adjustment, (B) is after adjustment. It is explanatory drawing explaining the beam waist position adjustment in the optical scanning device of 5th Embodiment of this invention. It is explanatory drawing explaining the beam waist position adjustment in the optical scanning device of 5th Embodiment of this invention. It is a schematic perspective view which shows the whole structure of the optical scanning device of 6th Embodiment of this invention. It is a perspective view which expands and shows the vicinity of the light source device of the optical scanning device of 6th Embodiment of this invention. It is explanatory drawing explaining the beam waist position adjustment in the optical scanning device of 6th Embodiment of this invention.

Explanation of symbols

102 optical scanning device 104 light source device 106 housing 106H holding unit 108 control board 110 multi-beam light source 112 coupling lens 114 pre-deflection optical system 116 deflector 118 scanning lens 120 separation mirror 122A mirror 124A cylinder mirror 126 photoconductor 128 adjustment support point 130 Fixed support point 134 Aperture 136 Slit 138 Light quantity detector 140 Knife edge 152 Optical scanning device AL Approximate straight line As, Ac, Ae / Bs, Bc, Be / Cs, Cc, Ce / Ds Scanning position Ch Light emitting point

Claims (13)

A light source unit having a plurality of light emitting points;
A pre-deflection optical system disposed in common with a plurality of laser beams emitted from a plurality of light emitting points of the light source unit;
Deflection means arranged in common to the plurality of laser beams that have passed through the pre-deflection optical system and deflecting these laser beams;
A scanning optical system disposed in common with the laser beam deflected by the deflecting means;
Separating means for separating a plurality of laser beams so as to scan on a plurality of scanned objects;
An optical element provided corresponding to each of the plurality of laser beams;
Imaging adjustment means for adjusting the maximum spot diameter of each laser beam on the plurality of scanned objects to be substantially the same in any one of the plurality of scanned objects;
An optical scanning device comprising:   The optical scanning apparatus according to claim 1, wherein the imaging adjustment unit is capable of adjusting a spot diameter based on a plurality of spot diameters in each of the plurality of scanned objects. A light source unit having a plurality of light emitting points;
A pre-deflection optical system disposed in common with a plurality of laser beams emitted from a plurality of light emitting points of the light source unit;
Deflection means arranged in common to the plurality of laser beams that have passed through the pre-deflection optical system and deflecting these laser beams;
A scanning optical system disposed in common with the laser beam deflected by the deflecting means;
Separating means for separating a plurality of laser beams so as to scan on a plurality of scanned objects;
An optical element provided corresponding to each of the plurality of laser beams;
Imaging adjustment means for adjusting the maximum beam waist shift of each laser beam with respect to the scanning surface on the plurality of scanned objects to be substantially the same and different in any one of the plurality of scanned objects;
An optical scanning device comprising:   4. The optical scanning device according to claim 3, wherein the imaging adjustment means is capable of adjusting a beam waist deviation based on a plurality of beam waist diameters in each of the plurality of scanned objects. . The pre-deflection optical system includes at least a coupling lens;
5. The optical scanning device according to claim 1, wherein the imaging adjustment unit is capable of adjusting a relative position between the light source unit and the coupling lens. A light source unit having a plurality of light emitting points;
A pre-deflection optical system disposed in common with a plurality of laser beams emitted from a plurality of light emitting points of the light source unit;
Deflection means arranged in common to the plurality of laser beams that have passed through the pre-deflection optical system and deflecting these laser beams;
A scanning optical system disposed in common with the laser beam deflected by the deflecting means;
Separating means for separating a plurality of laser beams so as to scan on a plurality of scanned objects;
An optical element provided corresponding to each of the plurality of laser beams;
Waist deviation minimizing means for minimizing beam waist deviation between each laser beam with respect to the scanning surface on the plurality of scanned objects;
An optical scanning device comprising:   7. The waist deviation minimizing unit minimizes the beam waist deviation by correcting an inclination of an approximate curve obtained by approximating beam waist positions in the plurality of scanned objects. The optical scanning device according to 1. The pre-deflection optical system includes at least a coupling lens;
The optical scanning device according to claim 6, wherein the waist deviation minimizing unit is capable of adjusting a relative angle between the light source unit and the coupling lens.   The optical scanning apparatus according to claim 6, wherein the scanning optical system includes the waist deviation minimizing unit. A light source unit having a plurality of light emitting points;
A pre-deflection optical system disposed in common with a plurality of laser beams emitted from a plurality of light emitting points of the light source unit;
Deflection means arranged in common to the plurality of laser beams that have passed through the pre-deflection optical system and deflecting these laser beams;
A scanning optical system disposed in common with the laser beam deflected by the deflecting means;
Separating means for separating a plurality of laser beams so as to scan on a plurality of scanned objects;
An optical element provided corresponding to each of the plurality of laser beams;
Waist deviation minimizing means for minimizing beam waist deviation between each laser beam with respect to the scanning surface on the plurality of scanned objects;
Imaging adjustment means for shifting the beam waist shift of each laser beam on the plurality of scanned objects,
An optical scanning device comprising: A multi-beam light source in which a plurality of light sources are two-dimensionally arranged;
A pre-deflection optical system arranged in common for a plurality of laser beams emitted from a plurality of light emitting points of the multi-beam light source;
Deflection means arranged in common to the plurality of laser beams that have passed through the pre-deflection optical system and deflecting these laser beams;
A scanning optical system disposed in common with the laser beam deflected by the deflecting means;
Separating means for separating a plurality of laser beams into a plurality of beam groups, and separating each of the beam groups so as to scan on a scanned object;
An optical element provided corresponding to each of the plurality of beam groups;
Of the plurality of laser beams constituting the beam group, the beam waist position of the laser beam at the center of the array is set as a representative beam waist position representing this beam group, and the maximum beam waist of each beam group is obtained using the representative beam waist position. Waist shift adjusting means for adjusting the shift so that the shift is substantially the same and has a different sign in any one of a plurality of scanned objects;
An optical scanning device comprising: A multi-beam light source in which a plurality of light sources are two-dimensionally arranged;
A pre-deflection optical system arranged in common for a plurality of laser beams emitted from a plurality of light emitting points of the multi-beam light source;
Deflection means arranged in common to the plurality of laser beams that have passed through the pre-deflection optical system and deflecting these laser beams;
A scanning optical system disposed in common with the laser beam deflected by the deflecting means;
Separating means for separating a plurality of laser beams into a plurality of beam groups, and separating each of the beam groups so as to scan on a scanned object;
An optical element provided corresponding to each of the plurality of beam groups;
Among the plurality of laser beams constituting the beam group, the center position of the beam waist position error is set as a representative beam waist position representing this beam group, and the maximum beam waist deviation of each beam group is determined using the representative beam waist position. A waist deviation adjusting means for adjusting so as to have substantially the same and different signs in any one of a plurality of scanned objects;
An optical scanning device comprising: A beam waist position adjusting method for adjusting a beam waist position in the optical scanning device according to claim 7,
A beam waist position detecting step of detecting each beam waist position in the plurality of scanned objects;
An approximate line calculation step for calculating the approximate line from each detected beam waist position;
A first adjustment step of adjusting a relative difference in waist position deviation so that the approximate straight line is parallel to an ideal straight line connecting the scanned positions of the plurality of scanned objects;
A second adjustment step of sliding the approximate straight line closer to the ideal straight line;
A beam waist position adjusting method characterized by comprising:

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