JP2007183354A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical scanner capable of reducing the unevenness of illuminance on an image face caused by the influence of both of the unevenness of light quantity depending on the field angle of a light source means and the unevenness of light quantity due to the tilt of an optical axis, and reducing the difference in the illuminance on the image face among a plurality of luminous fluxes, and to provide an image forming apparatus using the optical scanner. <P>SOLUTION: The optical scanner has: the light source means 1 in which a plurality of light emitting parts are separated from one another in a main scanning direction; an incident optical system LA which allows the plurality of luminous fluxes emitted from the plurality of light emitting parts incident on a rotating polygon mirror 5 with a width broader than the width in a main scanning direction of the deflecting faces 5a of the rotating polygon mirror; and an imaging optical system 6 which focuses the plurality of luminous fluxes reflected and deflected on the rotating polygon mirror onto a face to be scanned 8, wherein the respective elements are set to satisfy the following conditions (1) and/or (4): (4) 1(mm)≤ΔL≤6 (mm), where ΔL (mm)=2×finc×tanα+(X×W)/(finc), where finc stands for the focal length of the incident optical system in the main scanning direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical scanning device and an image forming apparatus using the same, and is suitable for an image forming apparatus such as a laser beam printer, a digital copying machine, a multi-function printer (multi-function printer) having an electrophotographic process, for example.

  Conventionally, an optical scanning device is used in an image forming apparatus such as a laser beam printer, a digital copying machine, or a multifunction printer. In this optical scanning device, a light beam emitted from a light source means is guided to a rotating polygon mirror (polygon mirror) as a deflecting means by an incident optical system. Then, the light beam deflected by the rotating polygon mirror is imaged in a spot shape on the surface of the photosensitive drum as the surface to be scanned by the imaging optical system, and the light beam is optically scanned with the light beam.

  In such an optical scanning device, the light beam emitted from the light source means is converted into a parallel light beam by a collimator lens or the like, and the light beam converted into the parallel light beam is corrected by a cylindrical lens in order to perform tilt correction. To form a line image. Then, the light beam deflected by the deflection surface of the rotary polygon mirror is scanned at a constant speed on the surface of the photosensitive drum by the imaging lens to form a spot.

  In recent years, with the increase in speed and size of devices such as laser beam printers, digital copiers, and multifunction printers, it has been desired to make scanning optical systems used as optical systems faster and more compact. As a method for speeding up, for example, there is a method using an overfilled optical system (hereinafter also simply referred to as “OFS system”) (see Patent Documents 1 and 2).

  In this OFS system, it is sufficient that the deflecting surface of the rotating polygon mirror has a light beam width necessary for substantially deflecting scanning in a wide incident light beam. Therefore, the rotating polygon mirror has a small diameter and the number of surfaces. It is possible to increase the frequency and is suitable for high speed.

  In the OFS system, the incident light beam on the rotary polygon mirror has a Gaussian distribution so that the light intensity is maximized in the vicinity of the optical axis of the condenser lens, and the area where reflection and deflection occurs as the field angle (scanning angle) increases. Changes from near the optical axis to the end. For this reason, the OFS system has a problem in that the illuminance on the surface to be scanned decreases as the image height increases, so-called unevenness in the amount of light occurs.

Patent Documents 1 and 2 disclose a method for correcting or reducing the unevenness in the amount of light on the surface to be scanned.
JP-A-8-160338 JP 9-96769 A

  In recent years, an optical scanning device in an image forming apparatus such as a laser beam printer, a digital copying machine, or a multi-function printer is compatible with high-speed image formation and high definition (high DPI) using the OFS method.

  However, in order to cope with higher speed and higher definition, the number of light beams emitted from the light source means may be increased. In addition to increasing the number of beams, there are methods using known techniques such as increasing the number of deflection surfaces of the rotating polygon mirror and rotating the rotating polygon mirror at high speed.

  However, in both cases, the upper limit values for high speed and high definition are determined in terms of the size and manufacturing of the optical scanning device. For this reason, it is very difficult to cope with higher speed and higher definition.

  In order to achieve high speed and high definition, the present applicant has previously proposed using light source means (surface emitting laser) having two or more light emitting portions as light source means in the optical scanning apparatus of the OFS method. ing. Here, the present inventor has found that when light source means such as a semiconductor laser emitting two or more beams is used in the OFS optical system, there are the following problems that have not been disclosed so far. The problem will be described below.

  FIG. 19 is a schematic diagram in a main scanning section of an incident optical system in an OFS system using light source means (light source) having two light emitting portions (light emitting points).

  In the figure, reference numeral 200 denotes a light source means having two light emitting portions A and B, which is composed of, for example, a monolithic two-beam semiconductor laser. W is an interval in the main scanning direction between the two light emitting portions A and B. 201 is a front principal point position of an incident optical system (not shown) having a condenser lens, a cylindrical lens, etc., 202 is a rear principal point position of the incident optical system, 203 is a rear focal position of the incident optical system, and 204 is incident. This is the optical axis of the optical system. Reference numeral 205 denotes a deflection position of a rotary polygon mirror as a deflecting means, and 205a denotes a deflection surface of the rotary polygon mirror. Also, in the figure, the intensity center (maximum intensity) position of the light beam emitted from the two light emitting portions A and B is indicated by a broken line (light beam) 301, and its half-value intensity (FWHM) is indicated by a solid line (light beam) 302. Yes.

  FIG. 21 shows the relative relationship between the beam radiation angle and the beam intensity.

  In FIG. 19, the light beams emitted from the two light emitting portions A and B arranged apart from the optical axis 204 of the incident optical system in the main scanning direction intersect with each other at the rear focal position 203 at the intensity center position 301. And intersects with the optical axis 204. The two light beams 301 intersecting with the optical axis 204 correspond to a distance ΔL (maximum intensity of the two light beams) on the deflection surface 205a in the main scanning direction according to the distance X from the rear focal position 203 to the deflection position 205 of the rotary polygon mirror. The images are separated by a distance of the center point).

  In the case of an OFS system using such light source means having two or more (two in the figure) light emitting units, there are the following problems.

  The image surface illuminance unevenness occurs on the surface to be scanned due to the influence of both the light amount unevenness due to the angle of view of the light source means and the light amount unevenness due to the inclination of the optical axis of the light source means. (Unevenness of light intensity due to angle of view and inclination of optical axis).

  ◎ Because two or more light beams are used, the light beams emitted from the two light emitting units arranged apart from the optical axis of the incident optical system are separated from each other on the deflection surface because the intensity center positions are separated from each other. An image plane illuminance difference occurs between two light beams (between beams) on the scanning plane. (Light amount unevenness generated by a light source (multi-beam light source) having a plurality of light emitting portions).

  According to the present invention, it is possible to reduce the image surface illuminance unevenness caused by both the light amount unevenness due to the angle of view of the light source means and the light amount unevenness due to the tilt of the optical axis, and the image surface illumination difference between a plurality of light beams by an optical method. It is an object of the present invention to provide an optical scanning device that can be used and an image forming apparatus using the same.

The optical scanning device of the invention of claim 1
Light source means in which a plurality of light emitting sections are separated in the main scanning direction, a rotating polygon mirror, and a light beam width in the main scanning direction of each of a plurality of light beams emitted from the plurality of light emitting sections is a deflection surface of the rotating polygon mirror An incident optical system that is incident on the deflecting surface in a state wider than the width in the main scanning direction, and an imaging optical system that forms an image on the surface to be scanned with a plurality of light beams deflected and scanned by the rotary polygon mirror In an optical scanning device,
The rotation angle of the rotary polygon mirror when scanning off-axis from the axis on the surface to be scanned is θp [°], the number of deflection surfaces of the rotary polygon mirror is N, and the circumscribed circle radius of the rotary polygon mirror R _p [mm], the inclination angle of the light source means in the main scanning direction is α [°], the beam radiation angle of the light beam emitted from the light emitting part of the light source means is θ _FFP [°], the incident The focal length of the optical system in the main scanning direction is finc [mm], the distance from the back focal position of the incident optical system to the deflection surface of the rotary polygon mirror in the main scanning section is X [mm], When the maximum light emitting portion interval is W [mm], the minimum value and the maximum value of the relational expression (2) shown below are b _min and b _max , respectively.

However,
ΔL [mm] = 2 × finc × tan α + (X × W) / (finc) (3)
Each element is set so as to satisfy the following conditions.

The invention of claim 2 is the invention of claim 1,
The light source means is a surface emitting laser.

The invention of claim 3 is the invention of claim 1 or 2, wherein
The number of light beams emitted from the light source means is 3 or more.

The image forming apparatus of the invention of claim 4
A plurality of optical scanning devices according to any one of claims 1 to 3 are provided, and two or more different scanning surfaces can be scanned.

The invention of claim 5 is the invention of claim 4,
The rotary polygon mirrors of the plurality of optical scanning devices are the same.

An optical scanning device according to a sixth aspect of the present invention comprises:
The light source means in which a plurality of light emitting sections are separated in the main scanning direction, the deflecting means, and the light beam width in the main scanning direction of each of the plurality of light beams emitted from the plurality of light emitting sections is the main surface of the deflection surface of the deflecting means. An incident optical system that is incident on the deflecting surface in a state wider than the width in the scanning direction; and an imaging optical system that forms an image on the scanned surface with a plurality of light beams deflected and scanned by the deflecting surface of the deflecting unit. In an optical scanning device,
The focal length in the main scanning direction of the incident optical system is finc [mm], the distance from the rear focal position of the incident optical system to the deflection surface of the deflecting means in the main scanning section is X [mm], and the main scanning direction. When the maximum light emitting portion interval is W [mm] and the inclination angle of the light source means in the main scanning direction is α [°]
1 [mm] ≤ ΔL ≤ 6 [mm] (4)
However,
ΔL [mm] = 2 × finc × tan α + (X × W) / (finc) (3)
Each element is set so as to satisfy the following conditions.

The invention of claim 7 is the invention of claim 6,
The light source means is a surface emitting laser.

The invention of claim 8 is the invention of claim 6 or 7, wherein
The number of light beams emitted from the light source means is 3 or more.

The image forming apparatus of the invention of claim 9
A plurality of optical scanning devices according to any one of claims 6 to 8 are provided, and two or more different scanning surfaces can be scanned.

The invention of claim 10 is the invention of claim 9,
The deflecting means of the plurality of optical scanning devices is the same.

An image forming apparatus according to an eleventh aspect of the present invention comprises:
The optical scanning device according to any one of claims 1 to 3 or 6 to 8, the photosensitive member disposed on the surface to be scanned, and the photosensitive member by a light beam scanned by the optical scanning device. A developing device that develops the electrostatic latent image formed thereon as a toner image, a transfer device that transfers the developed toner image to a transfer material, and a fixing device that fixes the transferred toner image to the transfer material; It is characterized by having.

An image forming apparatus according to the invention of claim 12
An optical scanning device according to any one of claims 1 to 3 or 6 to 8, and a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the optical scanning device. It is characterized by that.

The color image forming apparatus of the invention of claim 13
Each has a plurality of image carriers that are arranged on the surface to be scanned of the optical scanning device according to any one of claims 1 to 3 or claims 6 to 8 and that form images of different colors. It is characterized by.

The invention of claim 14 is the invention of claim 13,
It is characterized by having a printer controller that converts color signals input from an external device into image data of different colors and inputs them to each optical scanning device.

  According to the present invention, by appropriately setting each element of the light source means and the incident optical system, the image plane illuminance caused by both the light amount unevenness due to the angle of view of the OFS light source means and the light amount unevenness due to the inclination of the optical axis. The unevenness and the image plane illuminance difference between the plurality of light beams can be reduced by an optical method. As a result, a high-speed and high-definition optical scanning device and an image forming apparatus using the same can be achieved.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view of main parts in the main scanning direction (main scanning cross-sectional view) of Example 1 of the present invention, and FIG. 2 is a cross-sectional view of main parts in the main scanning direction of the incident optical system shown in FIG. In FIG. 2, the folding mirror 7 shown in FIG. 1 is omitted.

  In the following description, the main scanning direction is a direction perpendicular to the rotation axis of the rotating polygon mirror and the optical axis of the imaging optical system (the direction in which the light beam is reflected and deflected (deflected and scanned) by the rotating polygon mirror). The sub-scanning direction is a direction parallel to the rotation axis of the rotary polygon mirror. The main scanning section is a plane including the main scanning direction and the optical axis of the imaging optical system. The sub-scanning section is a section perpendicular to the main scanning section.

  In the figure, reference numeral 1 denotes light source means having a plurality of light emitting portions, which is composed of a surface emitting laser (VCSEL) which is a monolithic multi-laser in which 16 light emitting portions (16 beams) are arranged in the main scanning direction.

  Since the surface emitting laser 1 has a relatively narrow radiation angle (FWHM) due to its structure, unevenness in the amount of light easily occurs due to the influence of the tilt of the optical axis and the peak position difference (light amount difference) of the beam intensity.

  In the present embodiment, the present invention can be applied more effectively if the number of light beams emitted from the light source means is 3 or more.

  A light beam conversion element (collimator lens) 2 converts a light beam emitted from the light source means 1 into a parallel light beam (or a divergent light beam or a convergent light beam).

  A cylindrical lens 3 has a predetermined power (refractive power) only in the main scanning section (main scanning direction), and can adjust the focus position on the surface to be scanned.

  Reference numeral 4 denotes an anamorphic lens having negative (concave) power in the main scanning section and positive (convex) power in the sub-scanning section (sub-scanning direction). The anamorphic lens 4 forms a focal line on a deflecting surface 5a of a rotary polygon mirror 5 to be described later in the sub-scanning section, widens the light beam width in the main scanning section, corrects the wavefront aberration, and forms a spot shape on the scanned surface. Is corrected well.

  Reference numeral 7 denotes a folding mirror for making the entire apparatus compact, and deflects the light beam that has passed through the anamorphic lens 4 with respect to the main scanning direction and guides it to the rotary polygon mirror 5.

  Each element of the collimator lens 2, the cylindrical lens 3, the anamorphic lens 4 and the first imaging lens 6a described later constitutes an element of the incident optical system LA.

  Reference numeral 5 denotes a rotating polygon mirror (polygon mirror) as a deflecting means having 10 deflecting surfaces, and is rotated at a constant speed in the direction of arrow A in the figure by a driving means (not shown) such as a motor.

  An imaging optical system (fθ lens system) 6 includes first and second imaging lenses (fθ lenses as anamorphic lenses) 6a and 6b each having an aspheric shape in the main scanning section. The imaging optical system 6 focuses a light beam based on image information reflected and deflected by the rotary polygon mirror 5 onto a spot on a photosensitive drum surface 8 as a scanned surface in the main scanning section. In addition, the tilting of the deflecting surface is compensated for by optically conjugating the deflecting surface 5a of the rotary polygon mirror 5 and the photosensitive drum surface 8 in the sub-scan section. The first imaging lens 6a also constitutes a part of the incident optical system LA.

  In this embodiment, a light beam (incident light beam) incident on the rotary polygon mirror 5 passes through the first imaging lens 6a, and a light beam deflected by the rotary polygon mirror 5 (scanning light beam) is again formed into the first image. A double-pass configuration for entering the lens 6a is adopted.

  Reference numeral 8 denotes a photosensitive drum surface as a surface to be scanned.

  In this embodiment, a plurality of light beams emitted after being modulated from the semiconductor laser 1 are converted into parallel light beams by the collimator lens 2, converted into a convergent light beam once by the cylindrical lens 3, and incident on the anamorphic lens 4. Of the light beams incident on the anamorphic lens 4, the light beams in the sub-scanning section converge and pass through the first imaging lens 6 a (double path configuration) and enter the deflection surface 5 a of the rotary polygon mirror 5. An image is formed as a line image 5a (line image elongated in the main scanning direction) on 5a.

  At this time, the light beam incident on the deflecting surface 5 a is predetermined with respect to a plane perpendicular to the rotation axis of the rotary polygon mirror 5 from the sub-scanning section including the rotation axis of the rotary polygon mirror 5 and the optical axis of the imaging optical system 6. The incident light beam and the deflected light beam are separated from each other (obliquely incident optical system).

  On the other hand, a plurality of light beams in the main scanning section diverge and pass through the first imaging lens 6a to be converted into parallel light beams, and enter the deflection surface 5a from the center of the deflection angle of the rotary polygon mirror 5. (Front incidence). The beam width of the parallel beam at this time is set to be sufficiently wide with respect to the facet width of the deflection surface 5a of the rotary polygon mirror 5 in the main scanning direction (OFS system).

  The plurality of light beams deflected and reflected by the deflection surface 5a are guided to the photosensitive drum surface 8 through the first and second imaging lenses 6a and 6b, and the rotary polygon mirror 5 is rotated in the direction of arrow A. Thus, optical scanning is performed on the photosensitive drum surface 8 in the direction of arrow B (main scanning direction). Thereby, an image is recorded on the photosensitive drum surface 8 as a recording medium.

  Table 1 shows numerical values of the optical elements constituting the light source and the incident optical system LA of the present embodiment.

  In the present embodiment, the shapes of the first and second imaging lenses (G1, G2 lenses) 6a and 6b are expressed by the following mathematical expressions. The origin is the intersection of the lens surface of the imaging lens and the optical axis. As shown in FIG. 1, on the scanning start side and the scanning end side with respect to the optical axis, the optical axis is the x axis, the direction perpendicular to the optical axis in the main scanning section is the y axis, and the optical axis is orthogonal to the sub scanning section. The direction to be taken is the z axis, and can be expressed by the following continuous function.

  Scan start side

  End of scanning

R is a radius of curvature, and K, B ₄ , B ₆ , B _{8 and} B ₁₀ are aspherical coefficients.

  In this embodiment, the shape in the main scanning direction is symmetric with respect to the optical axis, that is, the aspheric coefficients on the scanning start side and the scanning end side are made to coincide.

  Further, the sub-scanning direction is the scanning start side and the scanning end side with respect to the optical axis, and the curvature in the sub-scanning cross section (surface including the optical axis and perpendicular to the main scanning cross section) of the second imaging lens 6b is set. In the effective part of the lens, it is continuously changed. Further, the shape of one surface of the second imaging lens 6b in the main scanning direction and the sub-scanning direction is configured symmetrically with respect to the optical axis.

  The shape in the sub-scanning direction is the scanning start side and the scanning end side with respect to the optical axis, the optical axis is the x axis, the direction orthogonal to the optical axis in the main scanning section is the y axis, and the optical axis is orthogonal to the sub scanning section The direction to be taken is the z axis, and can be expressed by the following continuous function.

  Scan start side

  End of scanning

(r 'is the sub-scanning direction of curvature _{radius, D 2, D 4, D} 6, D 8, D 10 coefficients)
The coefficient suffix s represents the scanning start side, and e represents the scanning end side.

  Here, the radius of curvature in the sub-scanning direction is a radius of curvature in a cross section orthogonal to the shape (bus line) in the main scanning direction.

Table 2 shows various numerical values of the optical scanning device of the first embodiment. Here, “E−x” indicates “10 ^−x ”.

  Next, in the optical scanning device using the OFS system, a cause of occurrence of unevenness in the amount of light on the surface to be scanned (image surface illumination unevenness) will be described.

  In the OFS system, the cause of unevenness in the amount of light on the surface to be scanned can be classified into the following three types.

(a) Uneven light intensity due to movement of entrance pupil position
(b) Unevenness in the amount of light generated due to the angle deviation of the optical axis of the light source
(c) Unevenness in light quantity generated by a light source (multi-beam light source) having a plurality of light emitting sections Hereinafter, each nonuniformity in light quantity of (a), (b), and (c) will be described in order.

(a) Unevenness of light amount due to movement of entrance pupil position FIG. 3 is a schematic diagram showing a deflected light beam deflected by a rotary polygon mirror and its intensity distribution. In the OFS system, the total amount of light in the light beam differs between when the deflected light beam scans the center of the image (passes through the optical axis of the imaging lens) and when it scans the image end (passes through the axis of the imaging lens). That is, in FIG. 3, when the light beam is deflected and scanned from the scanning start side to the scanning end side by the rotation of the rotary polygon mirror, the deflection surface (incidence pupil position) of the rotary polygon mirror continues from the deflection surface 57d to the deflection surface 57f. Move on. For this reason, it is shown that a light amount difference (image surface illuminance unevenness) occurs on the surface to be scanned.

  The amount of light (image surface illuminance) on the surface to be scanned is proportional to the integral amount in the range of the beam width 58d cut by the width of the deflection surface 57d and the beam width 58e cut by the width of the deflection surface 57e. To do.

  In general, an OFS system that deflects and scans a light beam that is wider than the width of the deflecting surface is such that the entrance pupil of the imaging optical system coincides with the deflecting surface. Occur.

  In FIG. 3, 501 is the intensity center position, and 510 and 520 are the beam widths.

  As shown in FIG. 4, when a normal laser light source is used, the beam intensity on the deflection surface is a Gaussian shape, and therefore when the pupil moves according to the angle of view, the light amount difference (image height) depends on the scanning position (image height) of the surface to be scanned. Unevenness of image plane illuminance) occurs.

  In the UFS (underfilled scanning) system in which the light beam narrower than the width of the deflecting surface in the main scanning direction is deflected and scanned by the deflecting surface, the image surface illuminance unevenness does not occur because the pupil of the imaging optical system is an aperture stop.

(b) Unevenness of light quantity caused by angle deviation of optical axis of light source FIG. 5 is a schematic diagram in the main scanning section from the light source means to the rotary polygon mirror, and FIG. 6 shows a deflected light beam deflected by the rotary polygon mirror and its intensity. It is a schematic diagram which shows.

  In FIG. 5, the light beam emitted from the light source means 400a is converted into a parallel light beam at the front principal point position 401 of the incident optical system and travels toward the deflection surface 405 of the rotary polygon mirror. Here, it is assumed that the angle of the light source unit 400a is inclined by an angle α ° from the vertical direction to the light source unit 400b due to an attachment angle error of the light source unit 400a or an error in packaging the chip. In this case, the intensity center position in FIG. 6 is separated from the intensity center position (optical axis of the incident optical system) 410 when it is not inclined, and away from the position 420 (intensity center position when the optical axis is inclined). . In FIG. 5, 410m and 410n are marginal rays of the light flux from the light source means 400a. Reference numerals 420m and 420n denote marginal rays of the light flux from the light source means 400b.

  FIG. 20 is an enlarged view of the main scanning section of the light source unit.

  When the laser optical axis is not inclined, that is, when the center of the beam intensity is parallel to the optical axis of the incident optical system, the optical axis of the laser beam emitted from all the light emitting points is not inclined. (Α = 0 deg.). However, when the light source is tilted due to an element manufacturing error or mounting error, the optical axis of the laser beam, that is, the center of the beam intensity is not parallel to the optical axis of the incident optical system (α ≠ 0).

At this time, when the focal length of the incident optical system (not shown) in the main scanning direction is finc [mm] and the inclination angle of the light source means in the main scanning direction is α [°], the distance ΔL1 [mm] of the intensity center position. ]
ΔL1 ＝ f _inc × tan α
It can be expressed as

  When the light beam is deflected and scanned from the scanning start side to the scanning end side by the rotation of the rotating polygon mirror, the deflection surfaces (incidence pupil positions) of the rotating polygon mirror are the deflection surfaces 57d to 57e in FIG. Move continuously to 57f. At this time, the amount of light (image surface illuminance) on the surface to be scanned is a light beam width 41 to 42 in which the beam intensity 400 is cut by the width of the deflecting surface 57d and a light beam width 43 to 44 that is cut by the width of the deflecting surface 57e. It is proportional to the integral value of the range. Further, the amount of light (image plane illuminance) on the surface to be scanned is proportional to the integral value in the range of light beam widths 45 to 46 in which the beam intensity 400 is cut by the width of the deflection surface 57f.

  FIG. 7 shows the integration result. FIG. 7 is a diagram showing the relationship between the scanning position (image height) and the image plane illuminance when the optical axis of the light source is inclined in the main scanning direction.

  As shown in FIG. 7, as the deflection scanning is performed from the scanning start side (left side) to the scanning end side (right side), the light amount increases, reaches the maximum value, and then decreases again. That is, it can be seen that the image plane illuminance on the surface to be scanned is tilted, and the ratio between the maximum value and the minimum value of the image plane illuminance is larger than in the case where there is no tilt of the light source shown in FIG.

(c) Unevenness in the amount of light generated by a light source (multi-beam light source) having a plurality of light-emitting portions Next, unevenness in the amount of light generated when a multi-beam light source is used will be described. 8 is a schematic diagram showing the deflected light beam from the light emitting part A (laser A) and its intensity in FIG. 19, and FIG. 9 is a schematic diagram showing the deflected light beam from the light emitting part B (laser B) and its intensity in FIG. It is.

  When the multi-beam light source is used as described above with reference to FIG. 8, the optical axis 501 of the incident optical system is separated from the center position 601 of the beam intensity, and the distance is from the rear focal position 203 of the incident optical system shown in FIG. It increases in proportion to the distance X to the deflection surface 205a.

  The total amount of light in the light beam differs when the deflected light beam scans the center of the image (passes through the optical axis of the imaging lens) and scans the image edge (passes off the axis of the imaging lens). That is, in FIG. 8, when the light beam is deflected and scanned from the scanning start side to the scanning end side by the rotation of the rotating polygon mirror, the deflection surface (incidence pupil position) of the rotating polygon mirror moves from the deflection surface 57d to the deflection surface 57f. It shows that a light amount difference occurs on the surface to be scanned due to continuous movement.

  The amount of light (image surface illuminance) on the surface to be scanned is the integration of the beam intensity distribution 600A in the regions of the beam widths 61A to 62A cut out by the width of the deflection surface 57d and the beam widths 63A to 64A cut out by the width of the deflection surface 57e. Proportional to quantity. Further, the amount of light (image plane illuminance) on the surface to be scanned is proportional to the integral amount of a region (not shown) in which the beam intensity distribution 600A is cut out in the range of the width of the deflection surface 57f.

  Similarly, when a multi-beam light source is used in the light emitting section B in FIG. 9, the optical axis 501 of the incident optical system and the intensity center position 601 of the beam are separated, and the distance is after the incident optical system shown in FIG. The distance increases in proportion to the distance X from the side focal position 203 to the deflection surface 205a.

  The total amount of light in the light beam differs when the deflected light beam scans the center of the image (passes through the optical axis of the imaging lens) and scans the image edge (passes off the axis of the imaging lens). That is, when the light beam is deflected and scanned from the scanning start side to the scanning end side by the rotation of the rotary polygon mirror, the deflection surface (incidence pupil position) of the rotary polygon mirror is continuously applied to the deflection surfaces 57d to 57f. It shows that there is a difference in the amount of light on the surface to be scanned due to movement.

  The amount of light (image surface illuminance) on the surface to be scanned is the integration of the beam intensity distribution 600B in the regions of the beam widths 61B to 62B cut out by the width of the deflection surface 57d and the beam widths 63B to 64B cut out by the width of the deflection surface 57e. Proportional to quantity. Further, the amount of light (image surface illuminance) on the surface to be scanned is proportional to the amount of integration in the range of a region (not shown) cut out in the range of the width of the deflection surface 57f.

  FIG. 10 shows the light quantity distribution on the scanned surface of the deflected light beams of the light emitting part A and the light emitting part B. The light quantity distribution A for the light emitting part A in FIG. 8 and the light quantity distribution B for the light emitting part B in FIG. 9 are symmetric with respect to the image center (optical axis of the imaging lens), and the maximum position of the image plane illuminance is off-axis. is doing. In FIG. 10, ΔAB is a light amount difference between two light beams.

  In this embodiment, in order to reduce the image plane illuminance unevenness on the surface to be scanned and the image plane illuminance difference between a plurality of light fluxes (a), (b), and (c) described above, the following conditional expression (1 ) Or / and each element is set to satisfy conditional expression (4).

That is, in this embodiment, the rotation angle of the rotary polygon mirror when scanning off-axis from the axis on the surface to be scanned is θp [°], the number of deflection surfaces of the rotary polygon mirror is N, and the rotation polygon mirror has Let the circumscribed circle radius be r _p [mm]. Further, the inclination angle of the light source means in the main scanning direction is α [°], and the beam emission angle of the light beam emitted from the light source means in the main scanning direction (the angle when the value from the peak value is reduced to ½) is θ _FFP. [°].

  Details of θp will be described with reference to FIG.

  FIG. 22 is a schematic diagram showing an optical path from the deflecting means to the surface to be scanned. When the surface normal direction of the deflection means (polygon mirror) when scanning the center position of the image is 0 deg., The surface normal θr of the polygon mirror scans the effective image area within the range of −θp <θr <θp. Yes. That is, the light beam reflected by the polygon mirror is deflected by | 4θp | from one image end toward the other image end, thereby forming an image in the effective image area.

Further, as shown in FIG. 21, θ _FFP is the full width at half maximum of the laser beam (Gaussian beam) from the light source. Since a normal laser has a fundamental mode in the transverse mode, the beam intensity with respect to the radiation angle exhibits a Gaussian shape in FIG. FFP is usually defined by the radiation angle of a beam having an intensity that is 50% (half value) of the maximum intensity of a Gaussian shaped laser beam (FWHM).

Further, when the focal length in the main scanning direction of the incident optical system is finc [mm], and the minimum value and the maximum value of the following relational expression (2) are b _min and b _max , respectively.

Each element is set to satisfy the following conditions.

  Or / and the following conditional expression (4) is satisfied.

1 [mm] ≤ ΔL ≤ 6 [mm] (4)
However, in the above conditional expressions (1) and (4),
ΔL [mm] = 2 × finc × tan α + (X × W) / (finc) (3)
It is.

  ΔL in the above expression (3) represents the peak position difference (interval between the central points of the maximum intensity of two light beams) on the deflection surface of the rotary polygon mirror. In Equation (3), X is the distance [mm] from the back focal position of the incident optical system to the deflection surface of the rotary polygon mirror in the main scanning section, and W is the maximum light emitting section interval [mm] in the main scanning direction. .

  Conditional expression (1) above defines the amount of light unevenness in one scanning line on the surface to be scanned, and if it deviates from conditional expression (1), it is difficult to reduce unevenness in image surface illumination, difference in image surface illumination, etc. It ’s not good.

  Conditional expression (4) defines the peak position difference ΔL of the beam intensity on the deflecting surface of the rotating polygon mirror, and if it deviates from conditional expression (4), it will reduce image surface illuminance unevenness, image surface illuminance difference, etc. Is not good because it becomes difficult.

  In the present embodiment, it is more desirable to set the conditional expressions (1) and (4) as follows.

1 [mm] ≤ ΔL ≤ 3 [mm] (4a)
Note that if the beam intensity peak position difference ΔL deviates by more than half of the scanning line interval, the print quality is extremely deteriorated. Therefore, it is necessary to make the beam intensity peak position difference ΔL not more than half the scanning line interval.

Therefore, the conditional expression (4) is changed to 0.5 [mm] ≦ ΔL / 2 ≦ 3 [mm] (4b)
May be replaced.

  In this embodiment, the focal length finc [mm] of the incident optical system in the main scanning direction and the distance X [mm] from the rear focal position of the incident optical system in the main scanning section to the deflection surface of the rotary polygon mirror are as follows. Is set. Further, the inclination angle α [°] of the light source means in the main scanning direction and the maximum light emitting portion interval W [mm] in the main scanning direction are set as follows.

finc = 71.698mm
X = 969.829mm
α = 0.5 °
W = 0.3mm
Therefore, the peak position difference ΔL of the beam intensity on the deflection surface of the rotary polygon mirror is ΔL = 2 × 71.698 × tan (0.5 °) + 969.829 × 0.3 / 71.698 = 5.31 [mm]
This satisfies the conditional expression (4).

Further, the beam radiation angle θ _FFP in the main scanning direction of the light beam emitted from the light source means is
θ _FFP = 8 °
Therefore, unevenness in the amount of light in one scanning line on the scanned surface
1-bmin / bmax = 0.45
This satisfies the conditional expression (1).

  In this embodiment, by setting the elements so as to satisfy the conditional expressions (1) and (4) in this way, it is possible to suppress the light amount unevenness of the scanning line on the scanned surface to 0.5 or less. Moreover, the light quantity difference between 16 beams can be suppressed to 0.5 or less.

  As described above, in this embodiment, the elements constituting the light source means and the incident optical system are appropriately set as described above. By taking into account the effects of both the light intensity unevenness due to the angle of view of the OFS light source means and the light intensity unevenness due to the tilt of the optical axis, the image surface illumination unevenness and the image surface illumination difference between multiple beams should be reduced by an optical method. Thus, a high-speed and high-definition optical scanning device can be achieved.

In this embodiment, the imaging optical system 6 is composed of two lenses. However, the present invention is not limited to this. For example, the imaging optical system 6 may be composed of a single lens or three or more lenses. Further, the imaging optical system may be configured to include a diffractive optical element.
[Color image forming device]
FIG. 11 is a cross-sectional view (sub-scanning cross-sectional view) of the main part in the sub-scanning direction of an image forming apparatus (color image forming apparatus) using a plurality of optical scanning devices shown in FIG.

  The image forming apparatus in the present embodiment is composed of the same rotary polygon mirror 5 and four optical scanning devices (stations) S1, S2, S3, S4 using the rotary polygon mirror 5 in common with two stations. Yes. The same rotating polygonal mirror 5 scans the photosensitive drum surfaces 8a, 8b, 8c, and 8d as different scanning surfaces, and forms a color image by multiple development.

  In FIG. 11, two rotating polygon mirrors 5 are illustrated. The rotating polygon mirror 5 is configured, for example, in two upper and lower stages, and reflects and deflects two light beams respectively on different deflection surfaces of the rotating polygon mirror 5. is doing.

  In FIG. 11, reference numeral 5 denotes a rotating polygon mirror (polygon mirror) as a common deflecting means, which is rotated at a constant speed in a predetermined direction by a driving means (not shown) such as a motor. 6a is a first imaging lens provided at each station, and 6b is a second imaging lens provided at each station. In the present embodiment, the first and second imaging lenses 6a and 6b constitute the imaging optical system of each of the stations S1, S2, S3 and S4.

  9a is a reflection mirror (bending mirror) arranged at station S1, 9b and 9c are reflection mirrors arranged at station S2, 9d is a reflection mirror arranged at station S3, and 9e and 9f are reflections arranged at station S4. It is a mirror. These reflecting mirrors 9a, 9b, 9c, 9d, 9e, and 9f are more rotated than the second imaging lens 6b in the optical path from the rotating polygon mirror 5 to the scanned surface 8 (8a, 8b, 8c, 8d). Located on the mirror 5 side.

  In this embodiment, the reflecting surfaces of the reflecting mirrors 9a, 9c, 9d, and 9f located closest to the surface to be scanned in each of the stations S1, S2, S3, and S4 are formed to bend in the longitudinal direction. Thus, in this embodiment, the curvature of the scanning line on the scanned surfaces 8a, 8b, 8c, and 8d in the sub-scanning direction (scanning line bending) is corrected.

  Reference numerals 8a, 8d, 8c, and 8d denote photosensitive drum surfaces as scanned surfaces corresponding to the stations S1, S2, S3, and S4, respectively.

  The image forming apparatus in this embodiment is configured by using a plurality of stations (optical scanning devices), and passes through the first imaging lens 6a by separating the light beam in the sub-scanning direction on the facets of the polygon mirror. The light beam is easily separated and guided to different scanning surfaces. In addition, since the first fθ lens 6a is shared by the two stations S1, S2 (S3, S4), the number of lenses can be reduced, and the entire apparatus can be simplified.

  FIG. 12 is a sectional view (main scanning sectional view) of the main part in the main scanning direction of the incident optical system according to Example 2 of the present invention. 12, the same elements as those shown in FIG. 2 are given the same reference numerals.

  This embodiment differs from the first embodiment described above in that the number of light emitting portions of the light source means 121 and the power and optical arrangement of each optical element constituting the incident optical system LA are different. Other configurations and optical functions are the same as those in the first embodiment, and the same effects are obtained.

  That is, in the figure, reference numeral 121 denotes a light source means having a plurality of light emitting portions (light emitting portions), and a monolithic multi having 64 light emitting portions (64 beams) arranged two-dimensionally in the main scanning direction and the sub-scanning direction. It consists of a surface emitting laser (VCSEL) which is a laser.

  Table 3 shows numerical values of each optical element constituting the light source and the incident optical system of the present example.

  In this embodiment, the focal length finc [mm] of the incident optical system in the main scanning direction and the distance X [mm] from the rear focal position of the incident optical system in the main scanning section to the deflection surface of the rotary polygon mirror are as follows. Is set. Further, the inclination angle α [°] of the light source means in the main scanning direction and the maximum light emitting portion interval W [mm] in the main scanning direction are set as follows.

finc = 71.698mm
X = 634.125mm
α = 0.3 °
W = 0.3mm
Therefore, the peak position difference ΔL of the beam intensity on the deflecting surface of the rotating polygon mirror is ΔL = 2 × 71.698 × tan (0.3 °) + 634.125 × 0.3 / 71.698 = 3.40 [mm]
This satisfies the conditional expression (4).

Further, the beam radiation angle θ _FFP in the main scanning direction of the light beam emitted from the light source means is
θ _FFP = 8 °
It is. Therefore, unevenness in the amount of light in one scanning line on the scanned surface
1-bmin / bmax = 0.38
This satisfies the conditional expression (1).

  In this embodiment, by setting each element so as to satisfy the conditional expressions (1) and (4) as described above, the unevenness of the light amount of the scanning line on the scanned surface can be suppressed to 0.5 or less, and 64 The light amount difference between the beams can be suppressed to 0.5 or less.

  In the present embodiment, as compared with the first embodiment described above, the amount of light unevenness is smaller and the total length of the incident optical system can be shortened, so that a higher-definition and compact optical scanning device can be provided.

  FIG. 13 is a sectional view (main scanning sectional view) of the main part in the main scanning direction of the incident optical system according to Example 3 of the present invention. In FIG. 13, the same elements as those shown in FIG.

  The difference between the present embodiment and the first embodiment is that the number of light emitting portions of the light source means 131, the configuration of the incident optical system, the power of each optical element constituting the incident optical system, and the optical arrangement are different. It is. Other configurations and optical functions are the same as those in the first embodiment, and the same effects are obtained.

  That is, in the figure, reference numeral 131 denotes a light source means having a plurality of light emitting portions, and a surface emitting laser (VCSEL) having 32 light emitting portions (32 beams) arranged two-dimensionally in the main scanning direction and the sub-scanning direction. It has become more.

  Table 4 shows numerical values of each optical element constituting the light source and the incident optical system of this example.

  In this embodiment, the focal length finc [mm] of the incident optical system in the main scanning direction and the distance X [mm] from the rear focal position of the incident optical system to the deflection surface of the rotary polygon mirror in the main scanning section are as follows. Is set. Further, the inclination angle α [°] of the light source means in the main scanning direction and the maximum light emitting section interval W [mm] in the main scanning direction are set as follows.

finc = 71.698mm
X = 334.073mm
α = 0.3 °
W = 0.21mm
Therefore, the peak position difference ΔL of the beam intensity on the deflecting surface of the rotary polygon mirror is ΔL = 2 × 71.698 × tan (0.3 °) + 334.073 × 0.21 / 71.698 = 1.73 [mm]
This satisfies the conditional expression (4).

Further, the beam radiation angle θ _FFP in the main scanning direction of the light beam emitted from the light source means is
θ _FFP = 10 °
Therefore, unevenness in the amount of light in one scanning line on the scanned surface
1-bmin / bmax = 0.21
This satisfies the conditional expression (1).

  In this embodiment, by setting each element so as to satisfy the conditional expressions (1) and (4) as described above, it is possible to suppress the uneven light amount of the scanning line on the surface to be scanned to 0.5 or less. The light amount difference between the beams can be suppressed to 0.5 or less.

  Further, in this embodiment, compared with the second embodiment, the light amount unevenness is smaller, the total length of the incident optical system can be shortened, and the number of lenses can be reduced, so that a higher-definition and compact optical scanning device can be achieved. it can.

  FIG. 14 is a sectional view (main scanning sectional view) of the principal part in the main scanning direction of Embodiment 4 of the present invention, and FIG. 15 is a sectional view of the principal part in the main scanning direction of the incident optical system shown in FIG. 14 and 15, the same elements as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.

  This embodiment differs from the first embodiment described above in that the power and optical arrangement of each optical element constituting the incident optical system LA and the number of lenses of the imaging optical system 16 are different. Other configurations and optical functions are the same as those in the first embodiment, and the same effects are obtained.

  That is, in the figure, reference numeral 142 denotes a collimator lens, which has a configuration in which two lenses are bonded together. Reference numeral 143 denotes a spherical lens (beam expander) which has a negative power, expands the beam width in the main scanning direction, and allows the focus position on the scanned surface 8 to be adjusted. A cylindrical lens 144 has a predetermined power only in the sub-scan section, and forms an incident light beam as a line image on the deflection surface 5a of the rotary polygon mirror 5 in the sub-scan section.

  An imaging optical system 16 includes first and second glass imaging lenses (anamorphic lenses) 16a and 16b, both of which are aspherical in the main scanning section, and a third imaging lens made of resin. 16c. The imaging optical system 16 images a light beam based on image information reflected and deflected by the rotary polygon mirror 5 onto a spot on a photosensitive drum surface 8 as a scanning surface in the main scanning section. In addition, the tilting of the deflecting surface is compensated for by optically conjugating the deflecting surface 5a of the rotary polygon mirror 5 and the photosensitive drum surface 8 in the sub-scan section. The first and second imaging lenses 16a and 16b also constitute part of the incident optical system LA.

  Table 5 shows numerical values of the optical elements constituting the light source and the incident optical system of the present example.

Table 6 shows various numerical values of the optical scanning device of Example 4 of the present invention. Here, “E−x” indicates “10 ^−x ”.

  In this embodiment, the focal length finc [mm] of the incident optical system in the main scanning direction and the distance X [mm] from the rear focal position of the incident optical system to the deflection surface of the rotary polygon mirror in the main scanning section are as follows. Is set. Further, the inclination angle α [°] of the light source means in the main scanning direction and the maximum light emitting section interval W [mm] in the main scanning direction are set as follows.

finc = 110.220mm
X = 597.267mm
α = 0.5 °
W = 0.3mm
Therefore, the peak position difference (difference in the amount of light between multiple beams) ΔL on the deflection surface of the rotating polygon mirror is ΔL = 2 × 110.220 × tan (0.5 °) + 597.267 × 0.3 / 110.220 = 3.55 [mm]
This satisfies the conditional expression (4).

Further, the beam radiation angle θ _FFP in the main scanning direction of the light beam emitted from the light source means is
θ _FFP = 8 °
Therefore, unevenness in the amount of light in one scanning line on the scanned surface
1-bmin / bmax = 0.23
This satisfies the conditional expression (1).

  In this embodiment, by setting each element so as to satisfy the conditional expressions (1) and (4) in this way, the unevenness of the light amount of the scanning line on the surface to be scanned can be suppressed to 0.5 or less. The light amount difference between the beams can be suppressed to 0.5 or less.

  In this embodiment, since the first and second imaging lenses 16a and 16b mainly having power in the main scanning direction are made of glass, a high-definition optical scanning device with higher environmental stability is provided. Can be provided.

[Image forming apparatus]
FIG. 16 is a cross-sectional view of the main part in the sub-scanning direction showing an embodiment of the image forming apparatus of the present invention. In the figure, 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. The image data Di is input to the optical scanning unit 100 having the configuration shown in any one of the first to fourth embodiments. The light scanning unit 100 emits a light beam 103 modulated in accordance with the image data Di, and the light beam 103 scans the photosensitive surface of the photosensitive drum 101 in the main scanning direction.

  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.

  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 rotation direction of the photosensitive drum 101 than the irradiation position of the light beam 103.

  The toner image developed by the developing unit 107 is transferred onto a sheet 112 as a transfer material by a transfer roller 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. 16), 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.

  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. 16). 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. Then, the sheet 112 conveyed from the transfer unit is heated while being pressed by the pressure contact portion between the fixing roller 113 and the pressure roller 114 to fix the unfixed toner image on the sheet 112. 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.

  Although not shown in FIG. 16, the print controller 111 controls not only the data conversion described above, but also controls each part in the image forming apparatus including the motor 115 and a polygon motor in the optical scanning unit described later. I do.

The recording density of the image forming apparatus used in the present invention is not particularly limited. However, considering that the higher the recording density is, the higher the image quality is required, the configurations of the first to fourth embodiments of the present invention are more effective in an image forming apparatus of 1200 dpi or more.
[Color image forming device]
FIG. 17 is a sub-scan sectional view of the color image forming apparatus of the present invention.

  In this figure, 60 is a color image forming apparatus, 11 is an image forming apparatus having the structure shown in FIG. 11, 21, 22, 23 and 24 are photosensitive drums as image carriers, and 31, 32, 33 and 34 are respectively. Each is a developing unit. Reference numeral 51 denotes a conveyance belt, 52 denotes an external device such as a personal computer, and 53 denotes a printer controller that converts color signals input from the external device 52 into image data of different colors and inputs them to the image forming apparatus 11.

  In the figure, the color image forming apparatus 60 receives R (red), G (green), and B (blue) color signals 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 image forming apparatus 11. The image forming apparatus 11 emits light beams (light beams) 41, 42, 43, and 44 that are modulated according to each image data, 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.

  The color image forming apparatus in this embodiment emits light beams corresponding to C (cyan), M (magenta), Y (yellow), and B (black) from one image forming apparatus 11. Then, image signals (image information) are recorded on the photosensitive drums 21, 22, 23, and 24, and a color image is printed at high speed.

  In the color image forming apparatus of this embodiment, as described above, the latent image of each color is formed on the corresponding photosensitive drums 21, 22, 23, and 24 using the light beams based on the respective image data by one image forming apparatus 11. Forming. After that, multiple transfer is performed on the recording material on the conveyance belt 51 to form one full-color image, and the full-color image is transferred to a sheet member (paper).

As the external device 52, for example, a color image reading device including a CCD (line 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.
[Color image forming device]
The color image forming apparatus of the present invention is not limited to the configuration shown in FIG. That is, in the same figure, four optical scanning devices 61, 62, 63, 64 having the configuration shown in any of the first to fourth embodiments are arranged side by side on the photosensitive drum surfaces 21, 22, 23, 24 in parallel. It is composed of a tandem type color image forming apparatus that records image information corresponding to each color light. In the figure, the same elements as those shown in FIG.

FIG. 3 is a main scanning sectional view of the optical scanning device according to the first embodiment of the present invention. FIG. 3 is a main scanning sectional view of the incident optical system according to the first embodiment of the present invention. Schematic diagram showing the deflected light beam and its intensity in Example 1 of the present invention The figure which shows the scanning position (image height) and image surface illumination intensity of Example 1 of this invention. FIG. 3 is a main scanning sectional view from the light source to the deflection surface according to the first embodiment of the present invention. Schematic diagram showing the deflected light beam and its intensity when the optical axis of the light source of Example 1 of the present invention is inclined in the main scanning direction. The figure which shows the scanning position (image height) and image surface illumination intensity when the optical axis of the light source of Example 1 of this invention inclines in the main scanning direction. Schematic diagram showing the deflected light beam from the light emitting part A (laser A) and its intensity in FIG. Schematic diagram showing the deflected light beam from the light emitting section B (laser B) and its intensity in FIG. The figure which shows the scanning position (image height) and image surface illumination intensity of the light emission part A and the light emission part B in FIG. FIG. 3 is a sub-scan sectional view of the image forming apparatus according to the first exemplary embodiment of the present invention. Main-scan sectional view of the incident optical system of Example 2 of the present invention Main-scan sectional view of the incident optical system according to Example 3 of the present invention Main scanning sectional view of Embodiment 4 of the present invention Main-scan sectional view of the incident optical system according to Example 4 of the present invention FIG. 3 is a sub-scan sectional view showing an embodiment of the image forming apparatus of the present invention. 1 is a schematic view of a main part of a color image forming apparatus according to an embodiment of the present invention. 1 is a schematic view of a main part of a color image forming apparatus according to an embodiment of the present invention. Schematic diagram showing the deflected luminous flux and its intensity when the light source has an angle of view in the main scanning direction The figure which shows the beam intensity center when the light source has an optical axis inclination in the main scanning direction Diagram explaining θ _FFP Diagram explaining θ _P

Explanation of symbols

1,121,131 Light source means (surface emitting laser diode)
2 Light flux conversion element (collimator lens)
3 Cylindrical lens 4 Anamorphic lens 7 Folding mirror 5 Deflection means (polygon mirror)
5a Deflection surface 6, 16 Imaging optical system 6a, 16a First imaging lens 6b, 16b Second imaging lens 16c Third imaging lens 8 (8a, 8b, 8c, 8d) Scanned surface (photosensitive) Body drum)
9 (9a, 9b, 9c, 9d, 9e, 9f) Reflection mirror S1, S2, S3, S4 Station (optical scanning device)
11 Image forming apparatus 61, 62, 63, 64 Optical 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 device 53 Printer controller 60 Color image forming apparatus 100 Optical 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 (14)

Light source means in which a plurality of light emitting sections are separated in the main scanning direction, a rotating polygon mirror, and a light beam width in the main scanning direction of each of a plurality of light beams emitted from the plurality of light emitting sections is a deflection surface of the rotating polygon mirror An incident optical system that is incident on the deflecting surface in a state wider than the width in the main scanning direction, and an imaging optical system that forms an image on the surface to be scanned with a plurality of light beams deflected and scanned by the rotary polygon mirror In an optical scanning device,
The rotation angle of the rotary polygon mirror when scanning off-axis from the axis on the surface to be scanned is θp [°], the number of deflection surfaces of the rotary polygon mirror is N, and the circumscribed circle radius of the rotary polygon mirror R _p [mm], the inclination angle of the light source means in the main scanning direction is α [°], the beam radiation angle of the light beam emitted from the light emitting part of the light source means is θ _FFP [°], the incident The focal length of the optical system in the main scanning direction is finc [mm], the distance from the back focal position of the incident optical system to the deflection surface of the rotary polygon mirror in the main scanning section is X [mm], When the maximum light emitting portion interval is W [mm], the minimum value and the maximum value of the relational expression (2) shown below are b _min and b _max , respectively.

However,
ΔL [mm] = 2 × finc × tan α + (X × W) / (finc) (3)
An optical scanning device characterized in that each element is set so as to satisfy the following conditions.   2. The optical scanning device according to claim 1, wherein the light source means is a surface emitting laser.   3. The optical scanning device according to claim 1, wherein the number of light beams emitted from the light source means is 3 or more.   An image forming apparatus comprising a plurality of optical scanning devices according to claim 1, wherein two or more different scanning surfaces can be scanned.   The image forming apparatus according to claim 4, wherein the rotary polygon mirrors of the plurality of optical scanning devices are the same. The light source means in which a plurality of light emitting sections are separated in the main scanning direction, the deflecting means, and the light beam width in the main scanning direction of each of the plurality of light beams emitted from the plurality of light emitting sections is the main surface of the deflection surface of the deflecting means. An incident optical system that is incident on the deflecting surface in a state wider than the width in the scanning direction; and an imaging optical system that forms an image on the scanned surface with a plurality of light beams deflected and scanned by the deflecting surface of the deflecting unit. In an optical scanning device,
The focal length in the main scanning direction of the incident optical system is finc [mm], the distance from the rear focal position of the incident optical system to the deflection surface of the deflecting means in the main scanning section is X [mm], and the main scanning direction. When the maximum light emitting portion interval is W [mm] and the inclination angle of the light source means in the main scanning direction is α [°]
1 [mm] ≤ ΔL ≤ 6 [mm] (4)
However,
ΔL [mm] = 2 × finc × tan α + (X × W) / (finc) (3)
An optical scanning device characterized in that each element is set so as to satisfy the following conditions.   7. The optical scanning device according to claim 6, wherein the light source means is a surface emitting laser.   8. The optical scanning device according to claim 6, wherein the number of light beams emitted from the light source means is three or more.   9. An image forming apparatus comprising a plurality of optical scanning devices according to claim 6 and capable of scanning two or more different surfaces to be scanned.   The image forming apparatus according to claim 9, wherein the deflecting units of the plurality of optical scanning devices are the same.   The optical scanning device according to any one of claims 1 to 3 or 6 to 8, the photosensitive member disposed on the surface to be scanned, and the photosensitive member by a light beam scanned by the optical scanning device. A developing device that develops the electrostatic latent image formed thereon as a toner image, a transfer device that transfers the developed toner image to a transfer material, and a fixing device that fixes the transferred toner image to the transfer material; An image forming apparatus comprising:   An optical scanning device according to any one of claims 1 to 3 or 6 to 8, and a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the optical scanning device. An image forming apparatus.   Each has a plurality of image carriers that are arranged on the surface to be scanned of the optical scanning device according to any one of claims 1 to 3 or claims 6 to 8 and that form images of different colors. A color image forming apparatus.   14. The color image forming apparatus according to claim 13, further comprising a printer controller that converts color signals input from an external device into image data of different colors and inputs the converted image data to each optical scanning device.