JP4006208B2 - Multi-beam scanning device and image forming apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a multi-beam scanning device and an image forming apparatus using the same, and in particular, a light beam emitted from a light source means is reflected and deflected by a polygon mirror as a deflecting means, and the surface to be scanned is optically scanned via a scanning optical means. In particular, the present invention relates to an optical scanning optical system suitable for an image forming apparatus such as a laser beam printer having an electrophotographic process, a digital copying machine, or a multi-function printer (multi-function printer). The present invention relates to a multi-beam scanning device that simultaneously scans a light beam to achieve high speed and high definition, and always obtains a good image with reduced jitter.
[0002]
[Prior art]
  Conventionally, the multi-beam scanning apparatus has a synchronization detecting means for accurately determining the writing position on the photosensitive image carrier.
[0003]
  FIG. 23 is a perspective view of a main part of this type of conventional multi-beam scanning apparatus. 24A is a cross-sectional view of the main part in the main scanning direction (main scanning cross-sectional view) showing an optical path from the light source means of FIG. 23 to the synchronization detection means, and FIG. 24B is a synchronous detection from the light source means of FIG. It is principal part sectional drawing (sub-scanning sectional view) of the subscanning direction which showed the optical path to a means.
[0004]
  In the figure, the synchronization detection means 90 is a light detection element (BD sensor) 92 that detects that a synchronization detection light beam (BD light beam) has entered, and a slit (BD slit) that determines the synchronization position incident on the BD sensor 92. 91).
[0005]
  In FIG. 23, a part (BD light beam) of a plurality of light beams deflected by the deflecting surface 85 a of the deflecting means (optical deflector) 85 optically scans on the BD slit 91 and enters the opening of the BD slit 91. It is configured to reach the BD sensor 92 when it is approaching. That is, the BD slit 91 serves as a synchronization position determination unit that determines the timing of synchronization detection. There is also a configuration in which the edge of the BD sensor 92 is used as a synchronization position determining means instead of the BD slit 91.
[0006]
  The conventional multi-beam scanning device reduces the influence of surface tilt by optically conjugating the deflecting surface 85a of the optical deflector 85 and the BD sensor 92 within the sub-scanning section. The BD light beam reaches different positions in the sub-scanning direction.
[0007]
  Japanese Patent Application Laid-Open No. 7-281113 discloses a configuration of a scanning optical device having synchronization detecting optical means separate from the scanning optical means using synchronization detecting means in which the synchronization position determining means is a slit. . As a result, the scanning optical means and the scanning optical apparatus using the same are made compact.
[0008]
  Japanese Patent Application Laid-Open No. 2001-21819 discloses a configuration of a multi-beam scanning device in which an aperture stop is disposed between an optical element that is closest to the deflection unit among the optical elements that constitute the incident optical unit and the deflection unit. Yes. In this publication, the degree of freedom of arrangement of optical elements is improved.
[0009]
  Both of these scanning optical devices perform highly accurate image information recording by aligning the writing start position on the surface to be scanned by the synchronization detecting means.
[0010]
[Problems to be solved by the invention]
  In order to record image information with high accuracy in a multi-beam scanning device, a plurality of light beams are focused on the entire surface to be scanned, and jitter (print position deviation in the main scanning direction) is corrected well. This is very important.
[0011]
  However, when the edge of the BD slit 91 or the edge of the BD sensor 92, which is the synchronization position determining means, becomes uneven due to a manufacturing error or is tilted due to an assembly error or rotation adjustment of the light source means, a plurality of BD light beams are sub-scanning cross sections. Since the positions reaching the synchronization position determining means are different from each other, the synchronization detection timing is relatively shifted. This is a problem because it causes jitter on the surface to be scanned.
[0012]
  Note that the jitter here refers to a print position shift in the main scanning direction due to the inconsistency of the writing positions of the scanning lines corresponding to a plurality of BD light beams.
[0013]
  The present invention does not generate jitter on the surface to be scanned even when the edge of the BD slit or the edge of the BD sensor, which is the synchronization position determining means, becomes uneven due to manufacturing errors or tilts due to assembly errors or rotation adjustment of the light source means. It is an object of the present invention to provide a multi-beam scanning device capable of always obtaining a good image and an image forming apparatus using the same.
[0014]
[Means for Solving the Problems]
  The multi-beam scanning device according to the first aspect of the present invention is a light source unit having a plurality of light emitting units arranged separately from each other in the main scanning direction and the sub scanning direction, and is emitted from the plurality of light emitting units in the sub scanning section. An aperture stop that crosses a plurality of light beams, an optical deflector that deflects and scans a plurality of light beams emitted from the light emitting units, andIncident optical means for forming a plurality of light beams emitted from the plurality of light emitting sections on the deflection surface of the optical deflector as a line image elongated in the main scanning direction within a sub-scanning section;Scanning optical means for imaging a plurality of light beams deflected and scanned on the deflecting surface of the optical deflector on the scanned surface;Detecting a plurality of light beams deflected and scanned by the deflection surface of the optical deflector;Synchronization detecting means for generating a synchronization signal for determining the timing of the writing position on the surface to be scanned, and a multi-beam scanning device comprising:
  The synchronization detection means includes a synchronization detection sensor, a synchronization detection optical element that guides a plurality of light beams deflected and scanned by a deflection surface of the optical deflector to the synchronization detection sensor,Disposed in the optical path between the synchronization detection optical element and the synchronization detection sensor;Synchronization position determination means for determining the timing of synchronization detection;A correction optical element disposed in an optical path between the synchronization position determination means and the synchronization detection sensor;With
  The aperture stop is disposed in the optical path between the optical deflector and the optical element closest to the optical deflector among the optical elements disposed from the light source means to the optical deflector,
  Within the sub-scan section, the aperture stop and the synchronization position determining means are optically conjugate with each other by the optical element for synchronization detection.And
Within the sub-scan section, the optical detection element and the correction optical element form an optically conjugate relationship between the deflection surface of the optical deflector and the synchronous detection sensor.It is characterized by that.
[0015]
  According to a second aspect of the present invention, in the first aspect of the invention, the plurality of light beams deflected and scanned by the deflecting surface of the optical deflector are guided to the synchronization detection sensor without passing through the scanning optical means. It is characterized by that.
[0016]
  The image forming apparatus of the invention of claim 3Claim 1 or 2And developing the electrostatic latent image formed on the photosensitive member by a light beam scanned by the multi-beam scanning device as a toner image. Development device and transfer for transferring the developed toner image onto a transfer materialmeansAnd a fixing device for fixing the transferred toner image to the transfer material.
[0017]
  The image forming apparatus of the invention of claim 4Claim 1 or 2And a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the scanning optical device.
[0018]
  Each of the color image enlargement forming apparatuses of claim 5 isClaim 1 or 2A plurality of multi-beam scanning devices, and a plurality of image carriers which are arranged on the scanning surface of each multi-beam scanning device and form images of different colors. It is a feature.
[0019]
  According to a sixth aspect of the invention, there is provided a printer controller according to the fifth aspect of the invention, further comprising a printer controller that converts color signals input from an external device into image data of different colors and inputs the image data to each multi-beam scanning device. It is said.
[0020]
[0021]
[0022]
[0023]
[0024]
[0025]
[0026]
[0027]
[0028]
[0029]
[0030]
[0031]
DETAILED DESCRIPTION OF THE INVENTION
  (Reference Example 1)
  FIG. 1 is a perspective view of an essential part of Reference Example 1 of the multi-beam scanning apparatus of the present invention. FIG. 2 is a sectional view (main scanning sectional view) of the main part in the main scanning direction of Reference Example 1 of the multi-beam scanning apparatus of the present invention.
[0032]
  In this specification, the direction in which the light beam is reflected and deflected (deflected and scanned) by the deflecting means is defined as the main scanning direction, and the direction perpendicular to the optical axis and the main scanning direction of the scanning optical means is defined as the sub-scanning direction.
[0033]
  In the figure, reference numeral 1 denotes a light source means, which comprises, for example, a semiconductor laser array having two light emitting points (light emitting portions). The number of light emitting points may be three or more.
[0034]
  A condensing lens system 2 has a single collimator lens, and converts each of two light beams emitted from the light source means 1 into parallel light beams. The condenser lens system may be composed of a plurality of lenses. The condensing lens system may convert two light beams emitted from the light source means 1 into a divergent light beam or a convergent light beam as necessary.
[0035]
  Reference numeral 3 denotes an aperture stop, which limits the widths of two light beams emitted from the light source means 1.
[0036]
  A cylindrical lens 4 has a predetermined refractive power only in the sub-scanning direction, and the two light beams that have passed through the collimator lens 2 are long in the main scanning direction in the vicinity of the deflection surface 5a of the deflecting means 5 to be described later. It is formed as a line image.
  Here, the collimator lens 2 and the cylindrical lens 4 are collectively referred to as incident optical means.
[0037]
  An optical deflector 5 serving as a deflecting unit is composed of, for example, a six-sided polygon mirror (rotating polygonal mirror), and is rotated at a constant speed in the direction of arrow A in FIG.
[0038]
  Reference numeral 7 denotes a scanning optical means (scanning lens system) having imaging performance and fθ characteristics, which has one fθ lens having an anamorphic refractive power, and receives two light beams reflected and deflected by the optical deflector 5. An image is formed on the photosensitive drum surface 8 as a scanning surface, and the surface tilt of the deflecting surface 5a of the optical deflector 5 is corrected.
[0039]
  At this time, the two light beams (scanning light beams) reflected and deflected by the deflecting surface 5a of the optical deflector 5 are guided to the photosensitive drum surface 8 via the scanning optical means 7, and the optical deflector 5 is guided in the direction of arrow A. , The optical drum surface 8 is simultaneously optically scanned in the arrow B direction (main scanning direction).
[0040]
  Further, a part of the two light beams reflected and deflected by the optical deflector 5 (BD light beam: light beam for synchronization detection) is folded back by the synchronization detection mirror (BD mirror) 9 via the scanning optical means 7, respectively, and the photosensitive drum. The light is incident on the synchronous detection means 10 including a slit (BD slit) 11 as a synchronous position determining means at a position optically equivalent to the surface 8 and a BD sensor 12 as a light detection element. The timing of the writing position (scanning start position) on the photosensitive drum surface 8 is adjusted using the synchronization signal obtained from the synchronization detection means 10. As a result, two scanning lines are formed on the photosensitive drum surface 8 to perform image recording.
[0041]
  The BD slit 11 has a light shielding wall (BD slit portion) in the main scanning direction, and determines the timing of synchronization detection (BD detection).
[0042]
  3 (A) and 3 (B) are respectivelyReference example 12A and 2B are diagrams showing an optical path from the light source means to the synchronization detection means, in which FIG. 3A is a main scanning sectional view, and FIG.
[0043]
  In the main scanning section shown in FIG. 3A, the two divergent light beams emitted from the semiconductor laser array 1 are converted into parallel light beams by the collimator lens 2, and the light beam width is determined by the aperture stop 3. At this time, the two light beams intersect at the position of the aperture stop 3. The two light beams that have passed through the aperture stop 3 enter the deflecting surface 5a of the optical deflector 5 through the cylindrical lens 4. A part of the two light beams (BD light beam) reflected and deflected by the deflecting surface 5a of the optical deflector 5 is condensed by the scanning lens system 7 on the BD slit 11 which is a synchronization position determining means. The light beam that has passed through the opening 11 a enters the BD sensor 12.
[0044]
  At this time, since the two BD light beams are scanned at different positions in the main scanning direction, there is a predetermined time difference from the time when the previous BD light beam is detected to the time when the next BD light beam is detected. By shifting the light emission timing by this predetermined time, the writing positions of all the scanning lines are made uniform.
[0045]
  In the sub-scan section shown in FIG. 3B, the two divergent light beams emitted from the semiconductor laser array 1 are converted into parallel light beams by the collimator lens 2 in the same manner as in the main scan section, The beam width is determined. At this time, the two light beams intersect at the position of the aperture stop 3. The two light beams that have passed through the aperture stop 3 are imaged by the cylindrical lens 4 in the vicinity of the deflection surface 5a of the optical deflector 5. Part of the two light beams (BD light beams) reflected and deflected by the deflecting surface 5a of the optical deflector 5 are guided to the BD slit 11 and the BD sensor 12 through the scanning lens system 7, respectively.
[0046]
  At this time, the aperture stop 3 where the two light beams intersect and the BD slit 11 are optically conjugated by the scanning lens system 7 so that the two BD light beams are at the same position on the BD slit 11 or substantially the same. The position is scanned. That is, the two BD light beams reach the same position on the BD slit 11 or substantially the same position.
[0047]
  Since the scanning lens system 7 has a power arrangement in the sub-scanning direction suitable for this, the lens portion that optically scans the effective scanning area on the photosensitive drum surface 8 and the lens portion that guides to the synchronization detecting means 10 include: The focal lengths in the sub-scanning direction are different from each other, an image is formed on the photosensitive drum surface 8 in the effective scanning area, and the aperture stop 3 and the BD slit 11 are optically conjugate in the optical path for synchronization detection. Is possible.
[0048]
  Here, an effect obtained when a plurality of BD light beams reach the same position or substantially the same position on the BD slit 11 will be described.
[0049]
  FIGS. 4A, 4B, and 4C are schematic views of main parts schematically showing how the BD slit 11 is scanned in the conventional multi-beam scanning device, and FIG. FIG. 4B is a main part schematic diagram when the BD slit 11 is rotated, and FIG. 5C is a main part schematic diagram when the edge of the BD slit is uneven. is there.
[0050]
  When the BD slit 11 is normally arranged as shown in FIG. 4A, a time difference for scanning the interval L between two BD light beams on the BD slit 11 when light is detected by a BD sensor (not shown). dT is generated. This time difference dT is a fixed value determined by the optical arrangement. Considering the time difference dT, the time from when the A laser (first BD light beam) is emitted until the B laser (second BD light beam) is emitted is calculated. The writing start position on the photosensitive drum surface 8 is aligned by making it open.
[0051]
  However, when the BD slit 11 is rotated and arranged due to an assembly error as shown in FIG. 4B, in addition to the predetermined time difference dT, the distance difference to the BD slit opening due to the inclination of the BD slit 11. A time difference ΔdT for causing the BD light beam to scan ΔL is generated. As a result, as shown in FIG. 5B, the writing position of the B laser is shifted by ΔJ in proportion to the time difference ΔdT with respect to the A laser, which causes a problem that jitter occurs.
[0052]
  Also, as shown in FIG. 4C, when the edge of the BD slit 11 is uneven due to a manufacturing error, the distance to the BD slit opening in addition to the predetermined time difference dT as in the case where the BD slit 11 rotates A time difference ΔdT for causing the BD light beam to scan the difference ΔL is generated. As a result, as shown in FIG. 5B, the writing position of the B laser is shifted by ΔJ with respect to the A laser, which causes a problem that jitter occurs.
[0053]
  The problem of jitter generation due to the inclination or non-linearity (irregularity / curvature) of the BD slit 11 is a problem peculiar to a multi-beam scanning device that simultaneously scans a plurality of light beams, and an optical scanning device that optically scans one light beam. This is a phenomenon that does not occur.
[0054]
  6A, 6B and 6C are respectively shown.Reference example 1FIG. 2 is a schematic diagram of a main part schematically showing a state of scanning a slit in the multi-beam scanning apparatus of FIG. 1, (A) is a schematic diagram of the main part when the BD slit is normally arranged, and (B) is a BD slit. FIG. 4C is a schematic diagram of a main part when the edge of the BD slit is uneven.
[0055]
  Reference example 1Then, since the two BD light beams are configured to reach the same position on the BD slit 11 or substantially the same position, even when the BD slit 11 shown in FIG. Even when the BD slit 11 shown in FIG. 6 (B) rotates due to an assembly error or when the BD slit 11 shown in FIG. 6 (C) becomes uneven due to a manufacturing error, the slit openings of two BD light fluxes are reached. The difference in the distance of L remains L, and the timing of light detection of the B laser does not deviate from that of the A laser. Therefore, as shown in FIG. 5A, the writing position of the B laser on the photosensitive drum surface 8 with respect to the A laser can always be matched regardless of the shape and arrangement of the BD slit 11, and the occurrence of jitter can be avoided. it can.
[0056]
  Note that optical elements having an optically conjugate relationship between the aperture stop 3 and the BD slit 11 include, for example, a lens, a mirror, a diffractive optical element, a stop, and the like.
[0057]
  in this wayReference example 1Then, as described above, the aperture stop 3 and the BD slit 11 are optically conjugated in the sub-scan section so that a plurality of BD light beams reach the same position or almost the same position on the BD slit 11. As a result, there is a manufacturing error or assembly error of the BD slit 11 from when the BD light beam scanned first is detected by the BD sensor 12 to when the next scanned BD light beam is detected. However, it is possible to provide a multi-beam scanning apparatus in which the writing position is always constant and there is no jitter.
[0058]
  In addition to the above, the means for the plurality of BD light beams to reach the same position or substantially the same position on the BD slit 11 can be configured by using, for example, a prism as shown in FIG. .
[0059]
  That is, in the sub-scan section in the same figure, a part of the light beam emitted from the first light source 1a (BD light beam) is deflected by the prism 15 arranged behind the optical deflector 5, and the first light beam on the BD slit 11 is obtained. The second light source 1b is made to reach the same position or a substantially same position as a part of the light beam emitted from the light source 1b (BD light beam). Even if a prism or the like is used in this way,Reference example 1The same effect can be obtained.
[0060]
  still,Reference example 1In FIG. 3, the light beam from the light source means 1 may be guided directly to the optical deflector 5 through the aperture stop 3 without using the collimator lens 2 and the cylindrical lens 4.
[0061]
  AlsoReference example 1In FIG. 1, the scanning optical means 7 is composed of one lens. However, the present invention is not limited to this. For example, the scanning optical means 7 may be composed of two or more lenses.
[0062]
  (Reference example 2)
  FIG. 8 shows a multi-beam scanning apparatus according to the present invention.Reference example 2FIG. FIG. 9 shows a multi-beam scanning device according to the present invention.Reference example 2FIG. 3 is a cross-sectional view (main scanning cross-sectional view) of the main part in the main scanning direction. 8 and 9, the same elements as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.
[0063]
  Reference example 2However, the difference from the reference example 1 described above is that the two BD light beams traveling toward the synchronization detection means 10 are synchronized with the synchronization detection means 10 via the synchronization detection optical means 13 (synchronization detection optical element) separate from the scanning optical means 7. And the aperture stop 3 is disposed between the cylindrical lens 4 and the optical deflector 5. Other configurations and optical effects areReference example 1It is substantially the same as this, and the same effect is acquired by this.
[0064]
  That is, in the figure, reference numeral 13 denotes a synchronization detection optical means, which is a synchronization detection lens (BD lens) having a single anamorphic power in which the power in the sub-scanning direction is stronger than the power (refractive power) in the main scanning direction. ), And part of the two light beams (BD light beams) deflected by the optical deflector 5 are respectively guided to the synchronization detecting means 10. The synchronization detection optical means 13 may be composed of a plurality of lenses.
[0065]
  Table 1 showsReference example 2The optical arrangement from the light source means 1 to the synchronization detection means 10 of the multi-beam scanning device in FIG.
[0066]
[Table 1]
[0067]
  10A, 10B, and 10C are respectively shown.Reference example 25A is a diagram showing an optical path from the light source means to the synchronization detection means, in which FIG. 10A is a main scanning sectional view, FIG. 10B is a sub-scanning sectional view, and FIG. FIG.
[0068]
  In FIG. 10A, two divergent light beams emitted from the semiconductor laser array 1 are converted into parallel light beams by the collimator lens 2, pass through the cylindrical lens 4, and then the light beam width is limited by the aperture stop 3 to deflect light. Incident on the deflecting surface 5 a of the vessel 5. Part of the two light beams (BD light beams) reflected and deflected by the deflecting surface 5a of the optical deflector 5 are condensed by the BD lens 13 on the BD slit 11 which is a synchronization position determining means, and the opening of the BD slit 11 The BD light beam that has passed through 11a enters the BD sensor 12 that is a light detection element.
[0069]
  In FIG. 10B, two divergent light beams emitted from the semiconductor laser array 1 are converted into parallel light beams by the collimator lens 2 and imaged in the vicinity of the deflection surface 5 a of the optical deflector 5 by the cylindrical lens 4. Further, the beam width is limited by the aperture stop 3 disposed between the cylindrical lens 4 and the deflecting surface 5a of the optical deflector 5. At this time, the two light beams intersect at the position of the aperture stop 3. The two light beams that have passed through the aperture stop 3 are reflected and deflected by the deflecting surface 5 a of the optical deflector 5. A part of the two light beams (BD light beam) reflected and deflected by the deflecting surface 5a is guided to the BD slit 11 and the BD sensor 12 through the BD lens 13, respectively. Here, the BD lens 13 optically conjugates the aperture stop 3 and the BD slit 11 in the sub-scan section, so that the two BD light beams are at the same position or substantially the same position on the BD slit 11. It is configured to reach. With this configuration, it is possible to provide a multi-beam scanning apparatus that is not affected by manufacturing errors, assembly errors, and the like of the BD slit 11 and that avoids the occurrence of jitter.
[0070]
  Reference example 2Then, as described above, by using the BD lens 13 separate from the scanning lens system 7 in the optical path toward the synchronization detection means 10, the focal length in the main scanning direction is shortened and the synchronization detection means 10 from the optical deflector 5 is shortened. The entire optical path is shortened to make the entire device compact. Further, by eliminating the BD mirror and shortening the optical path, the entire apparatus is simplified and the cost is reduced.
[0071]
  Further, the BD lens 13 can freely determine the focal length in the sub-scanning direction independently of the scanning lens system 7, so that the aperture stop 3 and the BD slit 11 are optically connected regardless of the arrangement of the aperture stop 3 and the BD slit 11. Can be conjugated. Moreover, the freedom degree of arrangement | positioning of the aperture stop 3 and the BD slit 11 can also be improved.
[0072]
  Further, since the aperture stop 3 is disposed between the cylindrical lens 4 and the optical deflector 5, the aperture stop 3 and the line image formed in the vicinity of the deflecting surface 5a can be brought close to each other. The light beam width in the sub-scanning direction of the BD light beam can be made relatively small.
[0073]
  The light beam width in the sub-scanning direction of the BD light beam on the BD slit 11 is related to the allowable shift amount of the arrival position of the plurality of BD light beams in the sub-scanning direction on the BD slit 11. That is, when the amount by which the arrival position in the sub-scanning direction shifts for each of a plurality of BD light beams on the BD slit 11 is dZ, and the light beam width in the sub-scanning direction of the BD light beam on the BD slit 11 is Ds.
        dZ ≦ Ds / 5 ………(1)
It is good to satisfy the condition.
[0074]
  More preferably,
        dZ ≦ Ds / 10 ………(2)
It is good to do.
[0075]
  Here, dZ is the amount of deviation between the first BD light beam and the second BD light beam in the sub-scanning direction. When there are three or more BD light beams, the second BD light beam and the third BD light beam It is the amount of deviation from the adjacent BD light beam, like the amount of deviation from the BD light beam.
[0076]
  Also, if the beam width in the sub-scanning direction of the BD light beam on the BD slit 11 is too small, the BD light beam is easily affected by unevenness of the BD slit 11 when the arrival position in the sub-scanning direction is shifted by a small amount for each of the plurality of BD light beams. Therefore, the allowable deviation of the arrival position in the sub-scanning direction cannot be increased. If it is too large, vignetting will occur at the BD sensor 12 and the writing start position will be shifted, or the amount of vignetting will differ for each BD light beam, causing jitter.
[0077]
  ThereforeReference example 2Then, when the width of the BD sensor 12 in the sub-scanning direction is Dc (mm), the light beam width Ds (mm) of the BD light beam on the BD slit 11 in the sub-scanning direction is
        0.05 ≦ Ds ≦ Dc ………(3)
Is preferable.
[0078]
  Reference example 2Then, the aperture diameter of the aperture stop 3 has an elliptical shape in which the main scanning direction is 2.08 mm and the sub-scanning direction is 1.42 mm. The BD sensor 12 has a circular shape (Dc = 1.25 mm) with a diameter of 1.25 mm. At this time, the beam width in the sub-scanning direction of the BD beam on the BD slit 11 is Ds = 0.99 mm.(1)It is the structure which satisfies. Furthermore, the amount by which the arrival position in the sub-scanning direction of the two BD light beams on the BD slit 11 is dZ = 0.00 mm, which is a conditional expression(1)And conditional expressions(2)Is satisfied.
[0079]
  Here, the optical conjugate relationship between the aperture stop 3 and the BD slit 11 will be described with reference to Table-1.
[0080]
  As shown in Table 1, the optical means for synchronization detection arranged between the aperture stop 3 and the BD slit 11 is composed of only a single lens (BD lens) 13 as described above, and has a sub-scanning cross section. The image of the aperture stop 3 is formed by the BD lens 13 at a position of 45.000 (mm) from the exit surface of the BD lens 13. The distance from the exit surface of the BD lens 13 to the BD slit 11 is 45.000 (mm), and the BD slit 11 is disposed at the image position of the aperture stop 3. This configuration indicates that the aperture stop 3 and the BD slit 11 are optically conjugated by the BD lens 13. As a result, as shown in FIG. 10C, part of the two light beams (BD light beams) emitted from the semiconductor laser array 1 reach the same position or substantially the same position on the BD slit 11, respectively. Can do.
[0081]
  At this time, when the distance from the emission surface of the BD lens 13 to the BD slit 11 is L2, and the distance from the emission surface of the BD lens 13 to the conjugate point with the aperture stop 3 is L,
        ΔL = L−L2 ………(4)
And
        | ΔL / L | ≦ 0.01 ………(5)
It is desirable to satisfy the following conditions.
[0082]
  More preferably,
        | ΔL / L | ≦ 0.005 ………(6)
Meets the conditionsFeetIt is good to make it.
[0083]
  Conditional expression above(5)If the distance is outside the range, a plurality of BD light fluxes are greatly scattered in the sub-scanning direction on the BD slit 11, and the BD slit 11 is easily affected by the shape error and the arrangement error, and the amount of jitter generated becomes unacceptable. It ’s not good.
[0084]
  Reference example 2Then, since the aperture stop 3 and the BD slit 11 are completely conjugated,
        ΔL = 0.000 ………(7)
That is,
        | ΔL / L | = 0.000(8)
It is.
[0085]
  Of course, the above conditional expression(5)Further conditional expressions(6)Is satisfied.
[0086]
  FIG. 11 is an enlarged view of the vicinity of the semiconductor laser array and the synchronous detection means. In the figure, the same elements as those shown in FIG.
[0087]
  In the figure, the synchronization detection means 10 comprises the BD slit 11 as a synchronization position determination means and the BD sensor 12 as a light detection element as described above. The semiconductor laser array 1 and the BD sensor 12 are attached to the same base 16, and the BD slit 11 is integrally formed with a laser holder 17 that is a holding member for holding the semiconductor laser array 1, and a set of laser units 18. Is configured. This reduces the number of parts and reduces costs. In the figure, the BD lens 13 is a composite plastic lens integrally formed with the cylindrical lens 4.
[0088]
  FIG. 12A is a schematic diagram of a main part when the laser unit 18 is viewed from the cylindrical lens side along the optical axis direction of the collimator lens, and FIG. 12B is a diagram illustrating the laser unit 18 along the optical axis of the collimator lens. It is the principal part schematic when it rotates only the angle (alpha) as a center axis | shaft. In FIGS. 9A and 9B, the same elements as those shown in FIG.
[0089]
  The scanning line pitch on the surface to be scanned needs to be a predetermined interval determined by the resolution, and the semiconductor laser array 1 is generally adjusted by rotating.Reference example 2In this case, the laser unit 18 in which the semiconductor laser array 1 and the synchronization detection means 10 are integrated is adjusted by rotating it around the optical axis of the collimator lens. At this time, the BD slit 11 serving as the synchronization position determining means also rotates together.
[0090]
  In a configuration in which a plurality of BD light beams pass through different positions on the BD slit, which is a synchronous position determining means, in the sub-scan section as in the conventional multi-beam scanning device, the BD slit is inclined with respect to the BD light beam. As a result, jitter is a problem.
[0091]
  ThereforeReference example 2Then, it is possible to provide a multi-beam scanning device in which jitter does not occur by configuring so that a plurality of BD light beams reach the same position or substantially the same position on the BD slit 11 in the sub-scan section.
[0092]
  That isReference example 2Has the effect of avoiding the occurrence of jitter due to the adjustment of the scanning line pitch interval of the multi-beam scanning device in which the light source means 1 and the BD slit 11 are integrally formed.
[0093]
  still,Reference example 2Then, the optical path from the optical deflector 5 to the synchronization detection means 10 is guided to the synchronization detection means 10 via the BD lens 13 separate from the scanning lens system 7 without passing through the scanning lens system 7. The present invention is not limited to this. For example, even if light is guided to the synchronization detection means 10 via the BD lens 13 after passing through the scanning lens system 7, the same effect as the present invention can be obtained.
[0094]
  in this wayReference example 2Then, by arranging the BD lens 13 separate from the scanning lens system 7 in the optical path from the optical deflector 5 to the synchronization detecting means 10 as described above, the aperture stop 3 is not affected by the shape of the scanning lens system 7. The degree of freedom of arrangement of the aperture stop 3 and the BD slit 11 can be increased while keeping the optically conjugate relationship between the BD slit 11 and the BD slit 11. Further, since the distance from the optical deflector 5 to the synchronization detecting means 10 can be shortened, the multi-beam scanning device can be configured compactly.
[0095]
  Further, by arranging the aperture stop 3 in the vicinity of the optical deflector 5, the aperture stop 3 that is optically conjugate with the BD slit 11 can be brought close to the line image position, so that the BD light beam on the BD slit 11 can be obtained. Can be kept relatively small. Thereby, the BD sensor 12 having a small and simple configuration can be used.
[0096]
  Further, by forming the BD slit 11 integrally with the holding member of the semiconductor laser array 1, the number of parts can be reduced and the cost can be reduced. Further, it is possible to avoid the occurrence of jitter by using the above-mentioned effect with respect to the rotation (inclination) of the BD slit when the holding member of the light source means is rotated when adjusting the scanning line interval on the surface to be scanned. it can.
[0097]
  (Embodiment1)
  FIG. 13 shows an embodiment of the multi-beam scanning device of the present invention.1FIG. 3 is a cross-sectional view (main scanning cross-sectional view) of the main part in the main scanning direction. FIG. 14 shows an embodiment of the present invention.1FIG. 6 is a sub-scan sectional view showing an optical path from a light source unit to a synchronization detection unit in FIG. 13 and 14, the same elements as those shown in FIG. 9 are denoted by the same reference numerals.
[0098]
  Table-2 shows the optical arrangement from the light source means 1 to the synchronization detection means 10 of the multi-beam scanning device in this embodiment.
[0099]
[Table 2]
[0100]
  In the present embodiment, the above-mentionedReference example 2The difference is that an optical element 14 is arranged between a BD slit 11 as a synchronization position determination means and a BD sensor 12 as a light detection element. Other configurations and optical effects areReference example 2It is substantially the same as this, and the same effect is acquired by this.
[0101]
  That is, reference numeral 14 in the drawing denotes a correction lens (correction optical element) (BD correction lens) for synchronization detection as an optical element, which has a positive power in the sub-scanning direction. Similar to the second embodiment described above, the aperture stop 3 and the BD slit 11 are conjugated by the BD lens 13 which is an optical means for synchronization detection, so that one of the two light beams reflected and deflected by the optical deflector 5 is obtained. The parts (BD light fluxes) reach the same position or substantially the same position on the BD slit 11.
[0102]
  Further, in the present embodiment, the optical system including the BD lens 13 and the BD correction lens 14 optically conjugates the deflecting surface 5a of the optical deflector 5 and the BD sensor 12 in the sub-scan section, thereby obtaining 2 Two BD light beams are configured to form an image (condensate) on the BD sensor 12. By adopting this configuration, by passing the BD light beam through the BD slit 11 with the light beam width in the sub-scanning direction being large, it is possible to reduce the occurrence of jitter when the two BD light beams pass through a position slightly shifted in the sub-scanning direction. The influence can be reduced, and the arrangement accuracy of the BD sensor 12 can be relaxed by reducing the beam width of the BD light beam on the BD sensor 12. Further, since a small BD sensor 12 can be used, there is an effect that the cost can be reduced.
[0103]
  At this time, by using the BD correction lens 14, the light beam width in the sub-scanning direction of the BD light beam reaching the BD slit 11 can be increased without being affected by the width of the BD sensor 12 in the sub-scanning direction.
[0104]
  Increasing the beam width in the sub-scanning direction of the BD beam on the BD slit 11 has an advantage that the allowable amount of positional deviation in the sub-scanning direction in which the two BD beams reach the BD slit 11 can be increased.
[0105]
  As described above, in the present embodiment, by arranging the BD correction lens 14 that exerts the condensing function in the sub-scanning direction between the BD slit 11 and the BD sensor 12 as described above, a desired light flux is formed on the BD slit 11. The light beam width in the sub-scanning direction of the BD light beam on the BD sensor 12 can be further reduced while maintaining the width. Thereby, the BD sensor 12 having a small and simple configuration can be used.
[0106]
  Further, by making the deflecting surface 5a of the optical deflector 5 and the BD sensor 12 optically conjugate in the sub-scan section, the tilting effect of the tilting surface can be obtained even in the optical path for synchronization detection. Even if it occurs, the BD sensor 12 can be prevented from being removed.
[0107]
  (Reference example 3)
  FIG. 15 shows a multi-beam scanning apparatus according to the present invention.Reference example 3FIG. 3 is a cross-sectional view (main scanning cross-sectional view) of the main part in the main scanning direction. 16A and 16B are respectivelyReference example 32A and 2B are diagrams showing an optical path from the light source means to the synchronization detection means, in which FIG. 3A is a main scanning sectional view, and FIG. FIG. 16C is a front view when the BD sensor shown in FIG. 15 is viewed from the front. 15 and 16, the same elements as those shown in FIGS. 9 and 10 are denoted by the same reference numerals.
[0108]
  Table 3 showsReference example 3The optical arrangement from the light source means 1 to the synchronization detection means 10 of the multi-beam scanning device in FIG.
[0109]
[Table 3]
[0110]
  Reference example 3In the aboveReference example 2The difference is that the synchronization position determination means is the edge of the BD sensor 12. Other configurations and optical effects areReference example 2It is substantially the same as this, and the same effect is acquired by this.
[0111]
  That is, in the main scanning section shown in FIG. 16A, the optical scanning is performed by the BD lens 13 which is an optical means for synchronization detection, and the synchronization detection is performed at the edge of the BD sensor 12. In the sub-scan section, the aperture stop 3 and the edge of the BD sensor 12 are optically conjugate, and the two BD light beams reach the same position or substantially the same position of the edge of the BD sensor 12. . Accordingly, even when the edge of the BD sensor 12 is inclined due to an assembly error or is non-linear (irregularity / curvature) due to a manufacturing error, the B laser (second BD light beam) is compared with the A laser (first BD light beam). It is possible to provide a multi-beam scanning device in which the timing of synchronous detection of (BD light flux) does not shift and jitter does not occur.
[0112]
  In FIG. 16C, 12a is an edge of the BD sensor 12, and 12b is a light receiving surface of the BD sensor 12.
[0113]
  in this wayReference example 3Then, as described above, the synchronization position determining means is used as the edge of the BD sensor 12, thereby reducing the number of parts and reducing the cost.
[0114]
  (Reference example 4)
  FIG. 17 shows a multi-beam scanning apparatus according to the present invention.Reference example 4FIG. FIG. 18 shows a multi-beam scanning apparatus according to the present invention.Reference example 4FIG. 3 is a cross-sectional view (main scanning cross-sectional view) of the main part in the main scanning direction. 17 and 18, the same elements as those shown in FIGS. 13 and 14 are denoted by the same reference numerals.
[0115]
  Table-4Reference example 4The optical arrangement from the light source means 1 to the synchronization detection means 10 of the multi-beam scanning device in FIG.
[0116]
[Table 4]
[0117]
  Reference example 4In the above-described embodiment1The difference is that a synchronization detection diaphragm (BD diaphragm) 15 is provided in the optical path from the optical deflector 5 to the synchronization detection means 10. Other configurations and optical actions are embodiments1It is substantially the same as this, and the same effect is acquired by this.
[0118]
  That is, in the figure, reference numeral 15 denotes a synchronous detection stop (BD stop), which restricts the width of a part of the two light beams reflected by the optical deflector 5 (BD light beam).
[0119]
  Reference example 4In FIG. 5, a part of the two light beams (BD light beam) reflected and deflected by the optical deflector 5 is limited in the light beam width by the BD diaphragm 15, condensed by the BD lens 13, and guided to the synchronization detecting means 10. Two BD light beams are imaged on the BD slit 11 by the BD lens 13 in the main scanning section. At this time, since the BD diaphragm 15 is provided, two BD light beams pass through the optical axis of the BD lens 13 and form an image on the BD slit 11. Therefore, the arrangement error of the BD lens 13 and the BD slit 11 and the manufacture of the BD lens. It is possible to avoid the problem of jitter that occurs due to the influence of focus variation due to errors.
[0120]
  FIG. 19 illustrates the present invention.Reference example 4FIG. 6 is a sub-scan sectional view showing an optical path from a light source unit to a synchronization detection unit in FIG. In the figure, the same elements as those shown in FIG.
[0121]
  In the same figure, the two BD light beams have their light beam widths restricted by the BD stop 15 as in the main scanning section, and are guided to the synchronization detecting means 10 via the BD lens 13. The synchronization detection means 10 includes a BD slit 11, a BD correction lens 14, and a BD sensor 12. In the optical path from the optical deflector 5 to the BD sensor 12, the BD lens 13 causes the BD diaphragm 15 and the BD slit 11 to be connected. As an optically conjugate relationship, the positions at which the two BD light beams are positioned (scanned) on the BD slit 11 are the same or substantially the same. This avoids the occurrence of jitter due to the inclination of the BD slit 11 due to an assembly error and the non-linearity (irregularity / curvature) of the BD slit 11 due to a manufacturing error.
[0122]
  Further, the optical system constituted by the BD lens 13 and the BD correction lens 14 makes the BD sensor 12 an optically conjugate relationship between the deflecting surface 5a of the optical deflector 5 and two BDs on the BD sensor 12. The light beam is condensed and the influence of the surface tilt of the deflecting surface 5a of the optical deflector 5 is avoided.
[0123]
  Reference example 4, The beam width in the sub-scanning direction of the BD light beam on the BD slit 11 is Ds = 0.437 mm, and the deviation amount of the arrival position of the two BD light beams on the BD slit 11 in the sub-scanning direction is dZ = 0.004 mm. And the conditional expression(1)And conditional expressions(2)It is the structure which satisfies.
[0124]
  Further, since the width of the BD sensor 12 in the sub-scanning direction is Dc = 1.25 mm, the configuration satisfies the conditional expression (3), but a BD correction lens 14 is provided between the BD slit 11 and the BD sensor 12. Since the BD light beam is condensed, the width of the light beam in the sub-scanning direction of the BD light beam on the BD sensor 12 can be reduced, and the BD sensor 12 may cause vignetting without necessarily satisfying the upper limit of the conditional expression (3). Synchronization detection can be performed.
[0125]
  (Reference Example 5)
  FIG. 20 shows a multi-beam scanning apparatus according to the present invention.Reference Example 5FIG. 6 is a sub-scan sectional view showing an optical path from a light source unit to a synchronization detection unit in FIG. In the figure, the same elements as those shown in FIG.
[0126]
  Reference Example 5In the aboveReference example 2The difference is that the light source means 81 is configured by arranging two semiconductor lasers 81a and 81b having one light emitting point, and two light beams (chief rays) from the semiconductor lasers 81a and 81b intersect in the sub-scan section. When the point to be crossed is a cross point P, the BD lens 13 disposed between the optical deflector 5 and the BD slit 11 makes the cross point P and the BD slit 11 optically conjugate. is there. Other configurations and optical effects areReference example 2It is substantially the same as this, and the same effect is acquired by this.
[0127]
  That is, 81 is a light source means, which comprises two first and second semiconductor lasers 81a and 81b each having one light emitting point. Reference numerals 2a and 2b denote condensing lens systems, each having a single collimator lens, which convert divergent light beams emitted from the corresponding light source means 81a and 81b into parallel light beams. Reference numerals 3a and 3b denote aperture stops, which limit the widths of the light beams emitted from the corresponding light source means 81a and 81b, respectively.
[0128]
  Reference Example 5The two divergent light beams emitted from the light source means 81 are converted into parallel light beams by the respective collimator lenses 2a and 2b, the light beam widths are limited by the respective aperture stops 3a and 3b, and are incident on one cylindrical lens 4. ing. The two light beams are formed by the cylindrical lens 4 in the vicinity of the deflection surface 5a of the optical deflector 5 as a line image that is long in the main scanning direction. Then, a part of the two light beams (BD light beam) deflected by the deflecting surface 5a is synchronously detected through a BD lens 13 and a BD slit 11 as a synchronous position determining means and a BD sensor 12 as a light detection element. Guided to means 10.
[0129]
  At this time, the two light beams emitted from the light source means 81 intersect between the cylindrical lens 4 and the deflecting surface 5a of the optical deflector 5, and when this intersecting point is taken as a cross point, it is within the sub-scanning cross section. The BD lens 13 optically conjugates the cross point P and the BD slit 11. As a result, the two BD light beams reach the same position or substantially the same position on the BD slit 11, and a multi-beam scanning device that avoids the occurrence of jitter due to the inclination or non-linearity (irregularity / curvature) of the BD slit 11. Can be provided.
[0130]
  [Image forming apparatus]
  FIG. 21 shows the embodiment described above.1FIG. 2 is a cross-sectional view of a main part in a sub-scan section showing an embodiment of an image forming apparatus (electrophotographic printer) using the multi-beam scanning apparatus of FIG. In FIG. 21, reference numeral 104 denotes an image forming apparatus. Code data Dc is input to the image forming apparatus 104 from an external device 117 such as a personal computer. The code data Dc is converted into image data (dot data) Di by a printer controller 111 in the apparatus. This image data Di is used in each embodiment.1Are input to the optical scanning unit 100 having the configuration shown in FIG. The light scanning unit (multi-beam scanning device) 100 emits a light beam (light beam) 103 modulated in accordance with the image data Di, and the light beam 103 causes the photosensitive surface of the photosensitive drum 101 to move in the main scanning direction. Scanned.
[0131]
  The photosensitive drum 101 serving as an electrostatic latent image carrier (photoconductor) is rotated clockwise by a motor 115. With this rotation, the photosensitive surface of the photosensitive drum 101 moves in the sub-scanning direction perpendicular to the main scanning direction with respect to the light beam 103. Above the photosensitive drum 101, a charging roller 102 for uniformly charging the surface of the photosensitive drum 101 is provided so as to contact the surface. The surface of the photosensitive drum 101 charged by the charging roller 102 is irradiated with the light beam 103 scanned by the optical scanning unit 100.
[0132]
  As described above, the light beam 103 is modulated based on the image data Di, and by irradiating the light beam 103, an electrostatic latent image is formed on the surface of the photosensitive drum 101. This electrostatic latent image is developed as a toner image by a developing device 107 disposed so as to abut on the photosensitive drum 101 further downstream in the rotational section of the photosensitive drum 101 than the irradiation position of the light beam 103. .
[0133]
  The toner image developed by the developing unit 107 is transferred onto a sheet 112 as a transfer material by a transfer roller (transfer unit) 108 disposed below the photosensitive drum 101 so as to face the photosensitive drum 101. The paper 112 is stored in the paper cassette 109 in front of the photosensitive drum 101 (on the right side in FIG. 21), but can be fed manually. A paper feed roller 110 is provided at the end of the paper cassette 109, and feeds the paper 112 in the paper cassette 109 into the transport path.
[0134]
  As described above, the sheet 112 on which the unfixed toner image has been transferred is further conveyed to a fixing device behind the photosensitive drum 101 (left side in FIG. 21). The fixing device includes a fixing roller 113 having a fixing heater (not shown) therein and a pressure roller 114 disposed so as to be in pressure contact with the fixing roller 113, and has been fed from the transfer unit. The unfixed toner image on the sheet 112 is fixed by heating the sheet 112 while being pressed by the pressure contact portion between the fixing roller 113 and the pressure roller 114. Further, a paper discharge roller 116 is disposed behind the fixing roller 113, and the fixed paper 112 is discharged out of the image forming apparatus.
[0135]
  Although not shown in FIG. 21, the print controller 111 controls not only the data conversion described above but also each part in the image forming apparatus including the motor 115 and the polygon motor in the optical scanning unit 100. Do.
[0136]
  [Color image forming apparatus]
  FIG. 22 is a schematic view of a main part of a color image forming apparatus according to an embodiment of the present invention. This embodiment is a tandem type color image forming apparatus in which four multi-beam scanning devices are arranged in parallel and image information is recorded on a photosensitive drum surface as an image carrier. In FIG. 22, 60 is a color image forming apparatus, 71, 72, 73, and 74 are multi-beam scanning apparatuses each having one of the configurations shown in the first to sixth embodiments, and 21, 22, 23, and 24 are image carriers. The photosensitive drums 31, 32, 33, and 34 are developing units, and 51 is a conveyor belt.
[0137]
  In FIG. 22, R (red), G (green), and B (blue) color signals are input to the color image forming apparatus 60 from an external device 52 such as a personal computer. These color signals are converted into C (cyan), M (magenta), Y (yellow), and B (black) image data (dot data) by a printer controller 53 in the apparatus. These image data are input to the multi-beam scanning devices 71, 72, 73, 74, respectively. From these multi-beam scanning devices, light beams 41, 42, 43, and 44 modulated according to each image data are emitted, and the photosensitive surfaces of the photosensitive drums 21, 22, 23, and 24 are emitted by these light beams. Are scanned in the main scanning direction.
[0138]
  The color image forming apparatus according to the present embodiment includes four multi-beam scanning devices (71, 72, 73, 74), each of C (cyan), M (magenta), Y (yellow), and B (black). The image signals (image information) are recorded on the surfaces of the photosensitive drums 21, 22, 23, and 24 in parallel with each other, and a color image is printed at high speed.
[0139]
  As described above, the color image forming apparatus according to the present embodiment uses the light beams based on the respective image data by the four multi-beam scanning devices 71, 72, 73, 74, and the corresponding photosensitive drums 21, It is formed on the 22, 23, and 24 surfaces. Thereafter, a single full color image is formed by multiple transfer onto a recording material.
[0140]
  As the external device 52, for example, a color image reading device including a CCD sensor may be used. In this case, the color image reading apparatus and the color image forming apparatus 60 constitute a color digital copying machine.
[0141]
【The invention's effect】
  According to the present invention, a part (BD light beam) of a plurality of light beams deflected by the deflecting unit is configured to reach the same position or substantially the same position of the synchronous position determining unit in the sub-scan section. And a multi-beam scanning device capable of avoiding jitter generated when the synchronization position determining means is inclined, uneven, or further curved, and thereby can always obtain a good image. An image forming apparatus can be achieved.
[Brief description of the drawings]
FIG. 1 of the present inventionReference example 1Main part perspective view
FIG. 2 of the present inventionReference example 1Main scanning cross section of
FIG. 3 of the present inventionReference example 1Of the optical path from the light source means to the synchronization detection means
Schematic
FIG. 4 is a main part schematic diagram for explaining the configuration of a conventional synchronization position determining means;
FIG. 5 is a diagram for explaining jitter due to a write position deviation of each scanning line;
FIG. 6 shows the present invention.Reference example 1Outline of the main part explaining the configuration of the synchronous position determination means
Sketch
FIG. 7 is a schematic view of the main part of the optical path from the light source means to the synchronization detection means.
FIG. 8 shows the present invention.Reference example 2Perspective view
FIG. 9 shows the present invention.Reference example 2Main scanning cross section of
FIG. 10 shows the present invention.Reference example 2Of the optical path from the light source means to the synchronization detection means
Schematic diagram
FIG. 11 shows the present invention.Reference example 2Enlarged view of the vicinity of the light source means and synchronization detection means
FIG. 12 shows the present invention.Reference example 2Schematic diagram of the main part of the laser unit
FIG. 13 shows an embodiment of the present invention.1Main scanning cross section of
FIG. 14 shows an embodiment of the present invention.1Of the optical path from the light source means to the synchronization detection means
Schematic diagram
FIG. 15 shows the present invention.Reference example 3Main scanning cross section of
FIG. 16 shows the present invention.Reference example 3Of the optical path from the light source means to the synchronization detection means
Schematic diagram
FIG. 17 shows the present invention.Reference example 4Perspective view
FIG. 18 shows the present invention.Reference example 4Main scanning cross section of
FIG. 19 shows the present invention.Reference example 4Of the optical path from the light source means to the synchronization detection means
Schematic diagram
FIG. 20 shows the present invention.Reference Example 5Of the optical path from the light source means to the synchronization detection means
Schematic diagram
FIG. 21 is a cross-sectional view of an image forming apparatus of the present invention.
FIG. 22 is a cross-sectional view of a color image forming apparatus of the present invention.
FIG. 23 is a perspective view of a conventional multi-beam scanning device.
FIG. 24 is from the light source means of the conventional multi-beam scanning device to the synchronization detection means.
Schematic diagram of the main part of the optical path
[Explanation of symbols]
    1 Light source means (semiconductor laser array)
    2 Condensing lens system (collimator lens)
    3 Aperture stop
    4 Cylindrical lens
    5 Deflection means (polygon mirror)
    6 Driving means
    7 Scanning optical means (fθ lens system)
    8 Scanned surface (photosensitive drum surface)
    9 BD mirror
    10 Synchronization detection means
    11 Synchronization position determination means (BD slit)
    12 BD sensor
    13 BD lens
    14 BD correction lens
    71, 72, 73, 74 Multi-beam scanning device
    21, 22, 23, 24 Image carrier (photosensitive drum)
    31, 32, 33, 34 Developer
    41, 42, 43, 44 Light beam
    51 Conveyor belt
    52 External equipment
    53 Printer Controller
    60 color image forming apparatus
    100 Multi-beam scanning device
    101 Photosensitive drum
    102 Charging roller
    103 Light beam
    104 Image forming apparatus
    107 Developing device
    108 Transfer roller
    109 Paper cassette
    110 Paper feed roller
    111 Printer controller
    112 Transfer material (paper)
    113 Fixing roller
    114 Pressure roller
    115 motor
    116 Paper discharge roller
    117 External equipment

Claims (6)

Light source means having a plurality of light emitting portions arranged apart from each other in the main scanning direction and the sub scanning direction, an aperture stop for crossing a plurality of light beams emitted from the plurality of light emitting portions in the sub scanning section, and the plurality An optical deflector that deflects and scans a plurality of light beams emitted from the light emitting unit, and a plurality of light beams emitted from the plurality of light emitting units as a line image elongated in the main scanning direction on the deflection surface of the optical deflector. Incident optical means for forming an image in a scanning section, scanning optical means for forming an image on a scanned surface by a plurality of light beams deflected and scanned by the deflecting surface of the optical deflector, and a deflecting surface of the optical deflector Synchronization detecting means for detecting a plurality of light beams deflected and scanned and generating a synchronization signal for determining the timing of the writing position on the surface to be scanned,
The synchronization detection means includes a synchronization detection sensor, a synchronization detection optical element for guiding a plurality of light beams deflected and scanned by a deflection surface of the optical deflector to the synchronization detection sensor, and the synchronization detection optical element. Synchronous position determining means disposed in the optical path between the synchronization detection sensors and determining the timing of synchronization detection, and a correction optical element disposed in the optical path between the synchronization position determination means and the synchronization detection sensor And comprising
The aperture stop is disposed in the optical path between the optical deflector and the optical element closest to the optical deflector among the optical elements disposed from the light source means to the optical deflector,
In the sub-scan section, the aperture stop and the synchronization position determining means are optically conjugate with each other by the synchronization detection optical element ,
A multi-beam scanning device characterized in that, in the sub-scan section, the deflection surface of the optical deflector and the synchronization detection sensor are optically conjugate with each other by the synchronization detection optical element and the correction optical element .   2. The multi-beam according to claim 1, wherein the plurality of light beams deflected and scanned by the deflection surface of the optical deflector are guided to the synchronization detection sensor without passing through the scanning optical means. 3. Scanning device. An electrostatic latent image formed on the photosensitive member by the multi-beam scanning device according to claim 1, the photosensitive member disposed on the surface to be scanned, and a light beam scanned by the multi-beam scanning device. An image forming apparatus comprising: a developing device that develops a toner image; a transfer unit that transfers the developed toner image onto a transfer material; and a fixing device that fixes the transferred toner image onto the transfer material. apparatus. 3. An image forming apparatus comprising: the multi-beam scanning apparatus according to claim 1; and a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the scanning optical apparatus. . A plurality of multi-beam scanning devices each comprising the multi-beam scanning device according to claim 1 and a plurality of images which are arranged on a scanning surface of each multi-beam scanning device and form images of different colors. A color image forming apparatus comprising a carrier. 6. The color image forming apparatus according to claim 5 , further comprising a printer controller that converts color signals input from an external device into image data of different colors and inputs the image data to each multi-beam scanning device.