JP5105253B2 - Optical scanning apparatus, image forming apparatus, and multicolor image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning apparatus applied to an image forming apparatus, a laser measuring apparatus, a laser processing apparatus, and the like, and a digital copying machine, a laser printer, and a laser plotter that include the optical scanning apparatus and can perform good image formation. The present invention relates to an image forming apparatus and a multicolor image forming apparatus such as a laser facsimile, or a multifunction machine having these functions.

In recent years, there has been a demand in the market for improvement in image quality of output images from image forming apparatuses such as digital copying machines, laser printers, laser plotters, laser facsimiles, or multifunction machines (MFPs) having these functions. In order to improve the image quality of the output image, it is essential to reduce and stabilize the beam spot diameter. Stabilization of the beam spot diameter can be achieved if the beam depth margin (distance in the optical axis direction that is less than or equal to the allowable beam spot diameter) is increased. However, the following relationship exists between the depth margin d and the beam spot diameter w (wavelength: λ),
d ∝ w ^ 2 / λ
There is a physical contradiction between beam spot diameter reduction and stabilization (expansion of depth margin), and when beam spot diameter reduction is realized, the depth margin usually becomes narrower and beam spot diameter The stability of is reduced.

  In order to reduce the beam spot diameter without narrowing the depth margin, it is necessary to expand the beam spot depth margin. As a method of expanding the depth margin, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2008-26586), the side lobe intensity of the beam profile on the scanned surface is increased using a phase type optical element. A method for increasing the depth margin is known.

  Further, parameters affecting the depth margin include the size of the aperture of the aperture member that is normally used in the optical scanning device and the size of the beam incident on the aperture member. If the size of the beam incident on the aperture member is smaller than the size of the opening, the side lobe intensity is weak on the scanned surface, and as a result, the depth margin is reduced. Conversely, if the beam is sufficiently large, the side lobe intensity increases and the depth margin increases.

In a general optical scanning device, it is necessary to ensure a depth margin in both the main scanning direction and the sub-scanning direction, so the ratio of the main scanning and sub-scanning of the size of the aperture of the aperture member and the incident on the aperture The ratio of the main scanning to the sub-scanning of the beam to be performed becomes important.
The size of the aperture of the aperture member and the ratio of main scanning to sub-scanning of the size of the aperture are determined by the optical system and the size of the beam spot on the surface to be scanned. The size of the beam incident on the aperture and the ratio of main scanning to sub scanning are determined by the divergence angle of the light source and the focal length of the coupling lens. It is desirable that the ratio between the main scanning and the sub scanning of the aperture and the ratio of the main scanning and the sub scanning of the beam incident on the aperture are the same, so that the depth margin in the main scanning direction and the sub scanning direction is increased. It can be secured efficiently. However, it is usually very difficult to do so.
For this reason, in either the main scanning direction or the sub-scanning direction, there is a problem that the size of the beam incident on the opening is reduced and the depth is reduced. If the focal length of the coupling lens is made sufficiently long, this problem can be avoided, but if so, the amount of light transmitted through the aperture is greatly reduced, which is very disadvantageous for speeding up the optical scanning device.

JP 2008-26586 A

  The present invention has been made in view of the above circumstances, and its purpose is to prevent a decrease in depth due to the relationship between the size of the aperture of the aperture member and the size of the beam incident on the aperture, thereby reducing the beam spot diameter. And an image forming apparatus using the same, and a multicolor image forming apparatus using the same.

In order to achieve the above object, the present invention employs the following solutions.
The first solving means of the present invention is an optical scanning device, comprising: a light source; a coupling lens for coupling divergent light from the light source; and an opening for transmitting only a part of the light beam from the light source. An aperture member having a phase, a phase optical element that partially changes the phase of the light beam, a deflecting unit that deflects and scans the light beam that has passed through the aperture member, and a scanning beam scanned by the deflecting unit. A scanning lens that forms an image on the surface to be scanned, where Im is the light intensity at the end in the main scanning direction at the opening of the aperture member, and Is is the light intensity at the end in the sub-scanning direction (here, opening) In the beam profile on the surface to be scanned, the phase-type optical element has a side lobe increase amount in a smaller direction between Im and Is. And to be greater than the direction of the side lobe increases the amount greater of Is, characterized in that it has the function of increasing the side lobe intensity.

According to a second solving means of the present invention, in the optical scanning device of the first solving means, in the shape of the phase modulation section in the phase type optical element, the width in the direction in which the increase amount of the sidelobe light is small is larger. It has a shape.
According to a third solving means of the present invention, in the optical scanning device of the first or second solving means, the phase modulation section of the phase type optical element has the opening of the aperture member in the traveling direction of the light beam. When an aperture projection part projected onto the phase-type optical element in parallel is considered, it is provided at least in the central part of the aperture projection part.
Furthermore, a fourth solving means of the present invention is the optical scanning device according to any one of the first to third solving means, wherein the shape of the phase modulation section is changed from one end of the opening to the other end. It has a shape that continues without interruption.
Further, the fifth solving means of the present invention is characterized in that, in the optical scanning device of any one of the first to fourth solving means, the phase-type optical element has only one phase modulation section. .

According to a sixth solving means of the present invention, in the optical scanning device according to any one of the second to fifth solving means, the shape of the phase modulation unit of the phase type optical element is a rectangular shape and the sidelobe light is A feature is that the width in the direction in which the increase amount is small has a larger shape.
According to a seventh aspect of the present invention, there is provided an optical projection apparatus according to the sixth aspect, wherein the aperture of the aperture member is projected onto the phase type optical element in parallel along the traveling direction of the light beam. When considering the portion, the longer width of the rectangular shape is equal to or larger than the opening projection portion.
Further, according to an eighth solving means of the present invention, in the optical scanning device according to any one of the first to seventh solving means, the shape of the opening of the aperture member is a rectangular shape.

According to a ninth solving means of the present invention, in the optical scanning device according to any one of the first to eighth solving means, the light source is a surface emitting laser or a surface emitting laser array, and Im <Is. And
According to a tenth solving means of the present invention, in the optical scanning device according to any one of the first to eighth solving means, the light source is an edge emitting laser array, and an arrangement direction of the light sources of the edge emitting laser array is changed. It is arranged to be inclined from the sub-scanning direction, and Im <Is.

The eleventh solving means of the present invention is the optical scanning device according to any one of the first to tenth solving means, wherein the phase type optical element has a side lobe increase amount in the main scanning direction in the sub scanning direction. The phase modulation unit in the phase type optical element that is larger than the side lobe increase amount and the phase type optical element in which the side lobe increase amount in the sub-scanning direction is larger than the side lobe increase amount in the main scanning direction. It has the phase modulation part which piled up the phase modulation part, It is characterized by the above-mentioned.
According to a twelfth solving means of the present invention, in the optical scanning device according to the eleventh solving means, the phase modulation section in the phase type optical element has a shape that is long in the main scanning direction and a shape that is long in the sub-scanning direction. It includes a shape.
Further, the thirteenth solving means of the present invention is characterized in that, in the optical scanning device of the twelfth solving means, the long shape in the main scanning direction and the long shape in the sub-scanning direction in the phase modulation section include a rectangle. .

A fourteenth solving means of the present invention is an image forming apparatus, the optical scanning device of any one of the first to thirteenth solving means, and the static formed on the image carrier by the optical scanning device. A developing unit that visualizes an electric image with toner, a transfer unit that transfers an image visualized on the image carrier to a recording medium, and a fixing unit that fixes the transferred image on the recording medium. It is characterized by having.
The fifteenth solving means of the present invention is a multi-color image forming apparatus, wherein the optical scanning device of any one of the first to thirteenth solving means and a plurality of image carriers on the optical scanning device. A developing unit that visualizes each of the electrostatic images formed on the image carrier with each color toner, a transfer unit that superimposes the color images visualized on the image carrier and transfers them to a recording medium, and a transferred image. And fixing means for fixing the image to the recording medium, and outputting a multicolor or color image.

In the optical scanning device of the present invention, by adopting the configuration of the first solving means, the amount of light transmitted through the opening is large, and the depth margin in the beam spot diameter on the scanned surface can be expanded, A high-speed and highly stable optical scanning device can be realized.
Further, in the optical scanning device of the present invention, by adopting the configuration of the second solution means, it is possible to increase the side lobes in the direction where the Im and Is are small.
Furthermore, in the optical scanning device of the present invention, by adopting the configurations of the third, fourth, and fifth solving means, the depth expansion can be effectively realized while avoiding the generation of high-order diffracted light, and the image can be realized. It is possible to prevent adverse effects and decrease in light utilization efficiency.

In the optical scanning device of the present invention, in addition to the above configuration and effects, the configuration of the sixth solving means is adopted, so that the increase amount in the direction in which the increase amount of the side lobe is small can be set smaller. The amount of increase in the direction in which the mass is large can be more intensively increased.
Further, in the optical scanning device of the present invention, by adopting the configuration of the seventh solving means, the side lobe intensity in the direction in which the side lobe increase amount is small can be hardly changed.
Furthermore, in the optical scanning device of the present invention, by adopting the configuration of the eighth solving means, it is possible to avoid a reduction in depth margin due to astigmatism.
Furthermore, in the optical scanning device of the present invention, by adopting the configuration of the ninth or tenth solution means, it is possible to increase the amount of light passing through the opening while avoiding a decrease in the depth margin, and to reduce the size and light. An optical scanning device with high utilization efficiency and wide depth can be realized.

In the optical scanning device of the present invention, by adopting the configurations of the eleventh and twelfth solving means, it is possible to obtain a good depth margin in both the main scanning direction and the sub-scanning direction without adversely affecting the image. it can.
In the optical scanning device of the present invention, the sidelobe intensity in the main scanning direction and the sub-scanning direction can be controlled completely independently by adopting the configuration of the thirteenth solution means.

  In the image forming apparatus or the multicolor image forming apparatus of the present invention, the depth margin is increased while the amount of light passing through the opening is increased by using the optical scanning device of any one of the first to thirteenth solving means. As a result, an image forming apparatus having high speed and high image stability can be realized. Furthermore, the frequency of process control can be reduced, and environmental loads such as toner consumption can be reduced.

  Hereinafter, the configuration, operation, and effects of the present invention will be described in detail based on the illustrated embodiments.

[Example 1]
(Description of optical scanning device)
First, an embodiment of an optical scanning device according to the present invention will be described with reference to FIGS.
FIG. 1 is a main scanning sectional view showing a configuration example of an optical scanning device, and shows a basic configuration example of an optical scanning device for one station. 2 is a three-dimensional view of the optical scanning device developed in the full-color image forming apparatus, and FIG. 3 is an optical system after the deflecting means (optical deflector such as a polygon mirror) 105 of the optical scanning device shown in FIG. It is sectional drawing which shows schematic structure of these.
The optical scanning device shown in FIGS. 1 to 3 is scanned by a light source unit 1001, a cylindrical lens 1041, an optical deflector 105 that deflects and scans a light beam from the light source unit 1001, and the optical deflector. The first scanning lenses 1061 to 1064 and the second scanning lenses 1071 to 1074 that image the scanned beam on the surface to be scanned (photosensitive drum as an image carrier) 1 (1Y, 1M, 1C, 1K) Here, scanning is performed for two stations in a direction facing the polygon mirror 105 as an example of the optical deflector. In FIGS. 1 and 2, for simplification of explanation, the light source unit 1001 and the optical system after the first scanning lens only illustrate one station.

  In the optical scanning device 3 shown in FIGS. 1 to 3, four photosensitive drums 1Y, 1M, 1C, and 1K that are the scanning surface 1 are arranged along the moving direction of the transfer belt 10, and toner images of different colors are sequentially arranged. In an image forming apparatus that forms a color image by transferring, each light scanning device is integrally formed, and all light beams are scanned by a single polygon mirror 105. The polygon mirror 105 has six surfaces and has a two-stage structure.

  As shown in FIG. 1, a light source unit 1001 includes a light source (for example, a semiconductor laser, a surface emitting laser, a surface emitting laser array, or an edge emitting laser array) 101 and a cup for coupling divergent light from the light source. A ring lens 102, an aperture member 103 having an opening that transmits only a part of the light beam from the light source, and a phase-type optical element 104 that partially changes the phase of the light beam are disposed. For example, the phase optical element 104 is provided between the aperture member 103 and the cylindrical lens 1041. In the example of FIG. 1, the phase optical element 104 is provided in close contact (integrated) with the aperture member 103.

  In the light source unit 1001, the light beam emitted from the light source 101 is converted into a substantially parallel light, a substantially divergent light beam, or a substantially convergent light beam by the coupling lens 102. In this embodiment, the light beam is substantially parallel light. Thereafter, the light beam 1002 cut to a desired light beam width by the aperture member 103 passes through the phase-type optical element 104, and is once condensed in the sub-scanning direction in the vicinity of the polygon mirror 105 by the cylindrical lens 1041, and the first scanning lens L1. (1061-1064) and a beam spot is formed on the scanned surface (image surface) 1 (1Y, 1M, 1C, 1K) by the scanning optical system including the second scanning lens L2 (1071-1074). As described above, the normal optical scanning apparatus employs a surface tilt correction optical system that once collects light in the sub-scanning direction in the vicinity of the polygon mirror 105 in order to reduce deterioration of optical characteristics due to the surface tilt of the polygon mirror 105. .

In the optical scanning device of this embodiment, the first scanning lens L1 (1061 to 1064) and the second scanning lens L2 (1071 to 1074) are both made of resin, and the diffraction grating is formed on one or more optical surfaces. You may do it.
Although the coupling lens 102 is made of glass mold and the cylindrical lens 1041 is made of glass, a diffractive structure may be formed and made of resin.
In general, as shown in FIG. 3, the folding mirrors (1111-1114, 1121-1124) are provided between the polarizing means (polygon mirror) 105 and the image plane (scanned surface) 1 (1Y, 1M, 1C, 1K). ) Is inserted, and the optical path is folded. In addition, although the embodiment in which the scanning optical system for each station is composed of two scanning lenses is shown, one or three or more scanning lenses may be used.

Expression expressions of the optical surface shape are as shown in the following Expressions 1, 2, and 3, where X is a coordinate in the optical axis direction of the lens, Y is a coordinate in the main scanning direction, and Z is a coordinate in the sub-scanning direction. C _m0 indicates the curvature in the main scanning direction at the center (Y = 0: cross section passing through the rotation center of the polygon mirror) and is the reciprocal of the radius of curvature Rm, and a ₀₀ , a ₀₁ , a _02,. Aspheric coefficient. C _S (Y) is the curvature in the sub-scanning direction with respect to Y, as shown in Equation 2, R _S0 represents the curvature on the optical axis in the sub-scanning direction, b ₀₀ , b ₀₁ , b ₀₂ ,. -Is an aspheric coefficient in the sub-scanning direction. K _Z (Y) in Formula 1 is as shown in Formula 3.

  Table 1 below shows the coefficients of the scanning lenses L1 and L2 and the cylindrical lens 1041, and Table 2 shows the distance between the optical elements and the refractive index (wavelength 655 nm) of each optical element. The coordinates in Table 2 are as shown in FIG. In Table 2, the “angle formed with the next surface” is an angle from the x axis, and the direction from the x axis to the y axis is positive. The “coordinate difference with the next surface center” is a value obtained by subtracting the coordinates of the current surface center from the coordinates of the next surface center. For the sake of simplicity, the description is made using either one of “distance and angle from the current surface center to the next surface center” and “coordinate difference from the next surface center”. Table 3 below shows coefficient data of the coupling lens 102, and the coupling lens 102 is a rotationally symmetric aspherical surface, and follows Formula 4 below. The exit surface (second surface) of the cylindrical lens 1041 is a flat surface. The coupling lens 102 is a glass mold, the cylindrical lens 1041 is made of glass, and the scanning lenses L1 and L2 are made of resin. Further, the lateral magnification of the scanning lens in the sub-scanning direction is about −0.96 times. Moreover, each dimension description unit of Tables 1-3 is mm.

  Note that the soundproof glass 108 in FIG. 1 is set to α = 16 deg and β = 2.8 deg, and the dustproof glass 1091 is disposed at an angle of 18.5 deg in the sub-scanning direction with respect to the direction perpendicular to the optical axis. Here, α is an angle from the x-axis toward the y-axis, and β is an angle from the z-axis toward the x-axis. Both thicknesses are 1.9 mm (refractive index is 1.514371 (wavelength 655 nm)).

(Explanation of depth expansion by phase type optical element)
Next, the phase type optical element 104 capable of expanding the depth margin will be described.
Several methods are known as methods for expanding the depth margin. For example, a method using a Bessel beam is known, and there are several methods for generating the method. Thus, it is not so preferable in terms of light utilization efficiency and layout. As described in Japanese Patent Application Laid-Open No. H10-228867, the depth expansion is preferably realized by slightly increasing the side lobe of the beam profile on the surface to be scanned using a phase type optical element.
The side lobe to be increased is preferably the primary side lobe intensity closest to the main lobe.

Here, the phase-type optical element 104 is an element that imparts a phase distribution to transmitted light by producing a concavo-convex structure on a transparent substrate. A phase distribution can also be provided by preparing a refractive index distribution instead of the uneven structure. Below, the part which gave the uneven structure (refractive index distribution structure) and changed the phase is called a phase modulation part.
By appropriately setting the structure of the phase modulation unit, it is possible to increase the side lobe of the beam profile on the surface to be scanned. Specific examples are shown below.

(Example 1-1)
As described above, the parameters that affect the depth margin include the size of the aperture of the aperture member 103 that is normally used in the optical scanning device and the size of the beam incident on the aperture member 103. If the size of the incident beam is small with respect to the size of the opening of the aperture member 103, the side lobe intensity becomes weak on the scanned surface, and as a result, the depth margin decreases. Conversely, if the beam is sufficiently large, the side lobe intensity increases and the depth margin increases.

FIG. 4 shows the simulation results. For the simulation, the optical system shown in FIG. 1 and Tables 1 to 3 was used. FIG. 4 is a beam spot diameter vs. defocus curve (hereinafter referred to as a BD curve) in the main scanning direction. In (a) and (b), the shape of the opening of the aperture member 103 is rectangular.
In FIG. 4A, the beam diameter on the aperture member 103 is 6.93 mm in the main scanning × 1.82 mm in the sub scanning, and the width of the aperture (rectangular) of the aperture member 103 is 5.00 mm in the main scanning × 1.28 mm in the sub scanning. Is a BD curve. Further, considering the cross section in the main scanning direction and the cross section in the sub scanning direction passing through the center of the opening of the aperture member 103, the light intensity at the opening end in the main scanning direction at the opening of the aperture member in the main scanning cross section is Im. In the sub-scanning section, if the light intensity at the opening end in the sub-scanning direction is Is, Im = 0.711 and Is = 0.787. However, the peak value at the opening is normalized to 1. Moreover, it is good also as a gravity center cross section instead of the cross section which passes along a center part, and there is almost no difference in a result.

  In the simulation, the beam incident on the aperture of the aperture member 103 is assumed to have a Gaussian distribution and is incident on the center of the aperture. Therefore, Im and Is have substantially the same value at both ends. When the values of Im and Is are different at both ends, the smaller value is set to Im and Is.

  FIG. 4B shows a case where the beam diameter on the aperture member 103 is 3.35 mm in the main scanning × 1.82 mm in the sub scanning, and the width of the opening (rectangular) of the aperture member 103 is 5.52 × 1.28 mm. It is a BD curve, Im = 0.257, Is = 0.787. BD curves of image heights ± 148.5, ± 100, ± 50, and 0 mm image height are drawn together. 4A and 4B, the beam spot diameter at an image height of 0 mm and a defocus of 0 mm is set to approximately 45 × 50 μm.

  4A and 4B, the defocus region (= depth) where the beam spot diameter is 50 μm or less is as follows. (A) is −2 mm to 1.8 mm (3.8 mm in width), and (b) is -1.6 mm to 1.5 mm (3.1 mm in width). As described above, when the light intensity at the end of the opening (Im in the above example) becomes small (Im = 0.711 in (a), Im = 0.257 in (b)), the depth decreases. . The beam profile in the main scanning direction (main scanning section) at this time is shown in FIG.

  FIG. 5A shows a beam profile (cross section of the center of gravity) in the main scanning direction at an image height of 0 mm and defocus of 0 mm, and FIG. 5B is a graph in which a part of FIG. The solid line (1) is a beam profile corresponding to FIG. 4A, and the broken line (2) is a beam profile corresponding to FIG. 4B. The side lobe peak intensity of the graph of the solid line (1) is larger than the side lobe peak intensity of the graph of the broken line (2), the solid line (1) is 4.2% and the broken line (2) is 2.0% ( The value is almost the same for both left and right side lobes).

Here, the side lobe peak intensity indicates the peak intensity of the side lobe closest to the main lobe. Normally, side lobes occur on both sides of the main lobe, but when the side lobe peak intensities on both sides are different, the smaller value is used.
From the above, it can be seen that when the light intensity at the edge of the opening decreases, the sidelobe peak intensity decreases and the depth margin decreases. Although only the main scanning section has been described above, the same can be said for the sub-scanning section.

  FIG. 6 shows an example (simulation result) that compensates for the above-described decrease in the depth margin using the phase optical element 104. The same optical system as described above was used for the simulation. 6A shows the phase-type optical element 104 used in the simulation, and a rectangular dotted line 104b is a shape obtained by projecting the opening of the aperture member 103 used in parallel with the optical axis (referred to as an aperture projection). Is shown.

In FIG. 6A, the hatched portion is the phase modulation unit 104a, and the phase difference from the non-phase modulation unit (other than the hatched portion) is set to π radians at the used wavelength (655 nm). The phase modulation unit 104a has a rectangular shape, the sub-scanning direction is larger than the aperture projection unit 104b, and the width in the main scanning direction is 100 μm. Further, the phase-type optical element 104 is arranged in close contact with and immediately after the aperture member 103 as shown in FIG. In the BD curve of FIG. 4B, the beam diameter on the aperture member is 3.35 mm in main scanning × 1.82 mm in sub scanning (same as in FIG. 4B), and the width of the opening (rectangle) is At 5.2 mm × 1.28 mm, Im = 0.300 and Is = 0.787.
FIG. 6B shows a BD curve in the main scanning direction, and the defocus region (= depth) where the beam spot diameter is 50 μm or less is −2.1 mm to 1.8 mm (width 3.9 mm). This is a depth margin equivalent to that shown in FIG.

FIG. 7 shows the beam profile (centroid cross section) in the main scanning direction when the phase type optical element 104 is used and the image height is 0 mm and the defocus is 0 mm.
A broken line (3) graph in FIG. 7A is a beam profile when the phase optical element 104 is used, and FIG. 7B is an enlarged graph of a part of FIG. The graph of the solid line (1) is the beam profile of FIG. 4A shown for comparison. The side lobe peak intensity of the broken line (3) graph is 5.9%.
In the above simulation (FIGS. 4A, 4B, and 6B), the side-lobe intensity in the sub-scanning direction does not change at all.

  When comparing the solid line (1) graph with the broken line graphs (2) and (3), the broken line graph (3) is the same as the broken line graph (2) (Im of (2)). = 0.257, Im of (3) = 0.300), but the sidelobe peak intensity is larger in (3) ((2) is 2.0%, (3) is 5.9%), Depth reduction due to Im reduction can be effectively suppressed, and a depth margin equivalent to (1) is obtained. When (1) and (3) are compared, Im is 0.771 for (1) and 0.300 for (3) (Is is the same). Accordingly, assuming that the amount of light emitted from the light source is equal, the amount of light transmitted through the aperture of the aperture member 103 is larger when (3) is small. Therefore, using the beam profile of the broken line graph (3), that is, using the phase type optical element 104 is advantageous in terms of light quantity, and is suitable for speeding up the optical scanning device.

  In an actual optical scanning device, the beam diameter on the aperture member 103 is determined by the divergence angle of the light source 101 and the focal length of the coupling lens 102 (one aspherical surface). When the focal length of the coupling lens 102 is changed, the beam diameter on the aperture member 103 can be varied, but the main scanning direction and the sub-scanning direction cannot be changed independently. If the coupling lens 102 is composed of a plurality of lenses, they can be changed independently, but the adjustment becomes complicated and the number of lenses increases, so that the stability is reduced and the cost is increased. It is not preferable. Therefore, in order to widen the depth margin, it is necessary to increase the focal length of the coupling lens 102. If Im <Is, for example, between Im and Is, the focal length is set according to Im. , Is is too large. If the values of Im and Is are too large, the amount of light transmitted through the opening of the aperture member 103 is reduced, which is disadvantageous for speeding up the optical scanning device. Therefore, the focal length is set according to the larger value of Im and Is (the larger value of Im and Is is preferably set to 0.7 to 0.9), and the smaller value of Im and Is. On the other hand, it is preferable to use the phase optical element 104 to increase the side lobe of the beam profile on the surface to be scanned and increase the depth margin. By doing so, it is possible to realize an optical scanning device that has a large amount of light transmitted through the opening of the aperture member 103 and a wide depth margin in the beam spot diameter on the surface to be scanned.

  The evaluation of Im and Is can be measured with a CCD camera using a lens such as an objective lens or a camera lens in a state where a light beam is incident on the opening of the aperture member 103, for example. In the imaging result by the CCD camera, the main scanning section and the sub-scanning section passing through the center of the opening of the aperture member 103 are extracted, and Im and Is may be obtained from the light intensity corresponding to the end of the opening. Moreover, it is good also as a cross section which passes along a gravity center instead of the cross section which passes along a center, and a difference hardly arises in a result. When obtaining Im and Is, it is preferable to normalize the peak intensity at the opening of the aperture member 103.

  Next, consider an aperture projection part in which the aperture part of the aperture member 103 is projected onto the phase optical element 104 in parallel along the traveling direction of the light beam. FIG. 8 shows an example of the shape of the phase modulation unit 104a that can increase the side lobe shape of the phase type optical element 104 in the direction of small Im and Is, and increases the side lobe in the main scanning direction. This is an example when it is assumed.

  In order to intensively increase the side lobes in the direction of small Im and Is, the phase modulation unit 104a in the phase-type optical element 104 has a width in the direction in which the amount of increase of the side lobe is large as shown in FIG. This can be realized by setting the width of the phase modulation unit 104a so that B is larger than A, where B is the width of the side lobe in the direction in which the amount of increase is small. When A or B is larger than the aperture projection part 104b, A or B is the width of the aperture projection part 104b. When the outer shape of the phase modulation unit 104a is a curve, a curve representing the outer shape is approximated by a straight line crossing the outer shape, and a rectangular shape is fitted with the same area, and the rectangular shape is considered. In addition, the dotted line part in FIG. 8 is the aperture projection part 104b. FIG. 8 shows a shape (longitudinal shape) in which the width in the sub-scanning direction is wider than the width in the main scanning direction, assuming that the side lobe intensity in the main scanning direction is increased. In order to increase the side lobe shape in the sub-scanning direction, a horizontally long shape may be used.

  8A and 8B, the phase modulation unit 104a has a rectangular shape, FIGS. 8C and 8D show that the phase modulation unit 104a has an elliptical shape, and FIGS. 8E and 8F show phase modulation. The part has a constricted central part. (G) fits the elliptical shape of (c) and (d), (h) fits the shape narrowed at the center of (e) and (f) with a rectangular shape (indicated by a thick dotted line 104c). It is a schematic diagram shown.

The above B (the longer width of the phase modulation unit 104a) may reach the edge of the aperture projection unit 104b, or may have a shape that fits in the aperture projection unit 104b, but the difference between A and B is as follows. The larger one is better, and the longer B is better. By doing so, the increase amount in the direction in which the increase amount of the side lobe can be set smaller, and the increase amount in the direction in which the increase amount of the side lobe is large can be increased more intensively.
It should be noted that since light hardly passes through the region outside the aperture projection part 104b, the optical characteristics are hardly affected even if the phase modulation part 104a is not provided.

  The phase modulation unit 104a in the phase optical element 104 is preferably provided at the center of the aperture projection unit 104b. When the light at the periphery of the aperture projection part 104b is condensed at one point (condensing point) on the surface to be scanned, the angle is larger than the light at the center part of the aperture projection part 104b (the light at the center part is It is assumed that the light enters the surface to be scanned at 0 degree). Since light incident at a large angle is a light wave having a high spatial frequency, if the phase of the light wave having a high spatial frequency is changed with respect to the light transmitted through the center of the aperture projection unit 104b, the light is collected. Since a peak tends to stand at a position away from the light spot (high-order diffracted light is likely to be generated), there is a risk of adversely affecting the image or reducing the light use efficiency. Therefore, the phase modulation unit 104a is preferably provided in the vicinity of the center of the aperture projection unit 104b. By doing so, it is possible to effectively expand the depth while avoiding the generation of high-order diffracted light, and to adversely affect the image. Can be prevented, and the light utilization efficiency can be prevented from decreasing.

  If the phase modulation unit 104a of the phase-type optical element 104 is cut in the middle, it may become a diffraction grating, and high-order diffracted light may be generated. Therefore, as shown in FIGS. 8A, 8 </ b> C, and 8 </ b> E, it is preferable to have a shape that continues from one end of the aperture projection portion 104 b to the other end without interruption. By doing so, generation of high-order diffracted light can be minimized.

  In addition, if the phase modulation unit 104a is provided at a plurality of locations on the phase-type optical element 104, it becomes a diffraction grating and high-order diffracted light may be generated. Therefore, the phase modulation unit 104a is provided only at one location. Is preferred.

  As the shape of the phase modulation unit 104a of the phase type optical element 104, the most desirable shape is a rectangular shape in which the width in the direction in which the increase amount of the side lobe light is small is larger than the direction in which the increase amount in the side lobe light is large. . By doing so, the increase amount in the direction in which the increase amount of the side lobe can be set smaller, and the increase amount in the direction in which the increase amount of the side lobe is large can be increased more intensively.

  In the rectangular phase modulation unit 104a as shown in FIGS. 8A and 8B, if the longer width is smaller than that of the aperture projection unit 104b, the increase amount of the side lobe is slightly small. Sidelobe strength increases. Therefore, the longer width of the rectangular phase modulation unit 104a is preferably the same as that of the aperture projection unit 104b or wider. By doing so, the side lobe intensity in the direction in which the side lobe increase is small hardly changes, which is desirable.

  In the above, the phase modulation unit 104a of the phase type optical element 104 has been described as an example in which the substrate is dug as shown in FIG. 6A. However, even if the phase modulation unit protrudes, there is no effect. It is equivalent.

  Further, if the aperture shape of the aperture member 103 is a shape other than a rectangle, the independence of the main scanning direction and the sub-scanning direction is lost, and astigmatism (the focus position in the main scanning direction and the focus position in the sub-scanning direction are deviated). This causes deterioration of the beam spot diameter (decrease in the depth margin). Therefore, the aperture shape of the aperture member 103 is preferably a rectangular shape (rectangular shape), and the depth margin can be increased by doing so.

  The aperture shape of the aperture member 103 is rectangular, the phase modulation unit 104a of the phase optical element 104 is rectangular, and the longer width is equal to or larger than the aperture projection unit 104b (for example, FIG. 8 ( a) example), the main scanning direction and the sub-scanning direction are independent, and the sidelobe intensity in either the main scanning direction or the sub-scanning direction (or both) can be selectively increased, and astigmatism is achieved. Since it is completely unaffected by aberrations, it is most suitable for the present invention.

(Example 1-2)
Next, an example in which a surface emitting laser or a surface emitting laser array is used as the light source 101 of the optical scanning device will be described.
A surface emitting laser emits a beam close to a perfect circle. Therefore, the shape of the opening of the aperture member 103 is desirably a shape having the same width in the main scanning direction and the sub-scanning direction, for example, a square shape or a circular shape. However, if an optical scanning device having such an aperture shape is designed, it is necessary to make the length of the optical system closer to the light source than the optical deflector (polygon mirror) 105. Will become larger. Therefore, the aperture shape of the aperture member 103 is set so that the width in the main scanning direction is longer than the width in the sub-scanning direction (that is, Im <Is), so that the optical system on the light source side than the polygon mirror 105 is set. It is better to shorten the length. However, as it is, the depth margin in the main scanning direction becomes narrow due to the small Im. If Im is sufficiently large, as described above, the amount of light passing through the opening is reduced, which is disadvantageous for speeding up. Therefore, Im is set low, and the depth margin in the main scanning direction is increased by increasing the side lobe intensity in the main scanning direction using the phase optical element 104 described in the first embodiment. good.

  The range of Im is more preferably 0.2 <Im (lower strength) <0.7. If Im (lower intensity) is 0.2 or less, the variation in the beam spot diameter on the surface to be scanned due to the variation in the divergence angle of the laser becomes large, which is not preferable. If it is larger than 0.7, the effect of expanding the depth by the phase type optical element 104 is reduced, and the amount of light passing through the opening of the aperture member 103 is reduced, which is undesirable and not preferred.

(Example 1-3)
Next, an embodiment when an edge emitting laser array is used as the light source 101 of the optical scanning device will be described.
If a plurality of light emitting portions of the edge emitting laser array are used in the sub-scanning direction, the interval between the plurality of light emitting portions must be set very narrow. If the interval between the light emitting portions is narrowed, thermal interference occurs between the light emitting portions, which causes deterioration of the laser modulation characteristics, which is not preferable. For this reason, the interval between the light emitting units is set to be relatively wide (about 10 to 30 μm), and instead, the arrangement direction of the light emitting units is preferably inclined from the sub-scanning direction.

  A schematic diagram of the arrangement of the light emitting portions of the edge emitting laser array is shown in FIG. FIG. 4A shows an example in which the arrangement direction of the light emitting parts of the edge emitting laser array is set to the sub-scanning direction, and FIG. 5B shows an example in which the arrangement direction of the light emitting parts is tilted from the sub-scanning difference direction. is there. An edge-emitting laser emits an elliptical beam with different divergence angles in directions orthogonal to each other. In the case of an edge-emitting laser array, an elliptical beam having a major axis perpendicular to the arrangement direction of the light emitting units. Is ejected. The tilt angle when tilting the arrangement direction of the light emitting units depends on the magnification in the sub-scanning direction of the optical system, the pitch between the light emitting points, and the writing resolution (dpi), but it may be necessary to tilt it to 45 degrees or more. In many cases, it is necessary to tilt to about 70 deg.

  As described above, when the arrangement direction of the emission points of the edge-emitting laser array is tilted, a beam having a wider width in the sub-scanning direction than in the main scanning direction is incident on the opening of the aperture member 103. As described above, in order to shorten the length of the optical system closer to the light source than the polygon mirror 105, the aperture shape of the aperture member 103 is longer in the main scanning direction than in the sub scanning direction. In this case, Im <Is and the depth margin in the main scanning direction is reduced. Designing to avoid this (for example, using an aperture shape that is longer in the sub-scanning direction, or reducing the pitch between the laser array emission points and reducing the tilt angle of the laser array), as described above, The length of the optical system on the light source side is longer than that of the polygon mirror 105, which may cause a problem that the writing optical system is enlarged and a problem such as a laser modulation characteristic.

Therefore, it is preferable not to use such a design, but to use an inclined laser array with an opening shape whose width in the main scanning direction is wider than that in the sub-scanning direction. Then, the side lobe intensity in the main scanning direction is preferably increased by using the phase optical element 104 described in the first embodiment, and the depth margin in the main scanning direction is preferably increased. By doing so, it is possible to realize an optical scanning device that is small in size, has good light utilization efficiency, and has a wide depth.
Note that the range of Im is more preferably set to 0.2 <Im (lower strength) <0.7 as described above.

(Example 1-4)
By applying the above, it is possible to realize the phase type optical element 104 that can arbitrarily control the side lobe intensity in both the main scanning direction and the sub-scanning direction. An example thereof is shown in FIG. FIG. 10 shows an example of a phase type optical element that increases the side lobe intensity in both the main scanning direction and the sub-scanning direction.
In order to arbitrarily control the side lobe intensity in both the main scanning direction and the sub-scanning direction, phase type optics in which the side lobe increase amount in the main scanning direction is larger than the side lobe increase amount in the sub-scanning direction. The phase modulator of the element (hereinafter referred to as Hm) and the phase modulator of the phase type optical element (hereinafter referred to as Hm) in which the side lobe increase amount in the sub-scanning direction is larger than the side lobe increase amount in the main scanning direction. Hs) can be realized by the phase type optical element 104 having the phase modulation unit 104a superposed on each other. Hm and Hs can be realized by the method described in the first embodiment (for example, FIG. 8).

In FIG. 10, the upper stage is a phase type optical element 104 having a phase modulation section (Hm + Hs) 104a that increases the side lobe intensity in both the main scanning direction and the sub-scanning direction, and the middle stage is a phase type optical element having Hs. The lower stage is a phase type optical element having Hm. 3A shows the phase modulation units Hm and Hs having a rectangular shape, FIG. 3B shows the phase modulation units Hm and Hs having an elliptical shape, and FIG. 3C shows the phase modulation units Hm and Hs. This is when the shape of Hs is constricted at the center.
In FIG. 10, it is assumed that the phase difference of the phase modulation unit 104a with respect to the non-phase modulation unit is π radians with respect to the wavelength used (for example, 655 nm).

  Here, superposing two phase type optical elements means adding the phases of the two phase type optical elements. In FIG. 10, the phase of the portion where the two phase modulation portions Hm and Hs of the phase optical element 104 overlap (the intersecting portion) is equivalent to the phase of the non-phase modulation portion (0 radians). . This is because π radians + π radians = 2π radians = 0 radians. As described above, it is preferable to set the portion where the two phase modulation units overlap with each other in a phase equivalent to that of the non-phase modulation unit.

  Moreover, the side lobe intensity is weaker and the depth is narrower in the smaller direction of Im and Is. Therefore, it is preferable to increase the increase amount of the side lobe intensity in the smaller direction between Im and Is and increase the increase amount of the depth margin. Even if the side lobe intensity in the larger direction of Im and Is is increased too much, the amount of increase in the depth margin cannot be increased, and conversely, the side lobe intensity is too large, which may adversely affect the image. . For this reason, it is preferable to increase the side lobe intensity increase in the smaller direction between Im and Is, so that the image is not adversely affected, and a good depth margin is obtained in both the main scanning direction and the sub-scanning direction. Can be obtained.

  When the phase of the phase modulation unit 104a is slightly shifted from π, the phase of the intersecting portion is slightly different from that of the non-phase modulation unit (for example, 0.9π + 0.9π = 1.8π), Even if the phase is the same as that of the non-phase modulation unit, there is almost no effect in practical use. Therefore, considering the processability of the element, it is desirable that the phase of the intersecting portion is the same as that of the non-phase modulation unit.

  Note that the most desirable in FIG. 10 is the phase type optical element 104 having the phase modulation unit 104a of FIG. 10A, where both Hm and Hs are considered to be rectangular shapes, and they are superposed. Well, by doing so, the sidelobe intensity in the main scanning direction and the sub-scanning direction can be controlled completely independently. That is, Hm can increase only the side lobe intensity in the main scanning direction, and Hs can increase only the side lobe intensity in the sub scanning direction. Further, as described above, if the opening shape is a rectangular shape, it is more preferable because it is not affected by astigmatism.

[Example 2]
(Description of image forming apparatus)
Next, a configuration example of an image forming apparatus using the optical scanning device described in the first embodiment is shown below.
FIG. 11 shows an example of the configuration of a multi-color image forming apparatus using the optical scanning device according to the present invention. Reference numerals 1Y, 1M, 1C, and 1K in the figure denote photosensitive drums arranged in parallel along the transfer belt 10, and the scanned surfaces (photosensitive drums) 1Y, 1M, and 1C shown in FIGS. , 1K.

  Each of the photosensitive drums 1Y, 1M, 1C, and 1K is rotated in the direction of the arrow in the drawing, and charging devices 2Y, 2M, 2C, and 2K (in the drawing, a contact type using a charging roller is shown). In addition, a charging brush, a non-contact type corona charger, or the like can also be used), the optical scanning device 3 of the present invention having the configuration described in the first embodiment, the developing devices 4Y, 4M, 4C of the respective colors, 4K, transfer devices (transfer charger, transfer roller, transfer brush, etc.) 5Y, 5M, 5C, 5K, cleaning devices 6Y, 6M, 6C, 6K and the like are arranged. In the figure, reference numeral 30 denotes a fixing device, 20 denotes a paper feed cassette on which a sheet-like recording medium S such as recording paper is stacked, 21 denotes a paper feed roller, 22 denotes a separation roller, 23 denotes a transport roller, and 24 denotes a registration roller. Show.

  The photosensitive drums 1Y, 1M, 1C, and 1K are exposed to a light beam that has been intensity-modulated in accordance with image information by an optical scanning device 3 that is a latent image forming unit, thereby forming an electrostatic latent image. The basic configuration of the optical scanning device 3 that performs this exposure step is as described in the first embodiment. In the example of FIG. 11, four deflectors (optical deflectors) 105 are used as in FIG. In this configuration, the system beams are distributed and scanned. That is, in the optical scanning device 3 shown in FIG. 11, four light source units 1001 and a cylindrical lens 1041 for corresponding to the four photosensitive drums 1Y, 1M, 1C, and 1K, one polygon mirror 105 that is a deflecting unit, It has four optical systems (first scanning lens (L1) 1061 to 1064, folding mirrors 1111 to 1114, 1121 to 1124, second scanning lens (L2) 1071 to 1074, etc.), and one deflection means (polygon) The mirror) 105 distributes and scans the four light beams to the left and right, and irradiates the photosensitive drums 1Y, 1M, 1C, and 1K with the light beams by the four optical systems.

  The electrostatic latent images formed on the photosensitive drums 1Y, 1M, 1C, and 1K are yellow (Y) developing device 4Y, magenta (M) developing device 4M, cyan (C) developing device 4C, and black (K) developing. The image is developed by the apparatus 4K and visualized as toner images of each color of yellow (Y), magenta (M), cyan (C), and black (K). The sheet-like recording medium S is fed one by one from the paper feed cassette 20 by the paper feed roller 21 and the separation roller 22 in synchronization with this development process, and reaches the registration roller 24 through the transport roller 23. Then, the sheet-like recording medium S is transferred to the transfer belt 10 by the registration rollers 24 in accordance with the timing at which the toner images on the photosensitive drums 1Y, 1M, 1C, and 1K visualized in the developing process come to the transfer position. The sheet-like recording medium S is carried by the transfer belt 10 and is sequentially conveyed to the transfer positions of the respective colors. Then, a transfer bias is applied by the transfer devices 5Y, 5M, 5C, and 5K arranged to face the photosensitive drums 1Y, 1M, 1C, and 1K with the transfer belt 10 interposed therebetween, and the photosensitive drums 1Y, 1M, and 5K are applied. The toner images of the respective colors on 1C and 1K are sequentially superimposed and transferred onto the sheet-like recording medium S. The four-color superimposed toner image (color image) transferred onto the sheet-like recording medium S is fixed by applying heat and pressure by the fixing device 30. Then, the sheet-like recording medium S on which the toner image is fixed is discharged to a paper discharge unit (not shown) outside the apparatus. The photosensitive drums 1Y, 1M, 1C, and 1K after the toner image transfer are cleaned by cleaning members (blades, brushes, etc.) of the cleaning devices 6Y, 6M, 6C, and 6K to remove residual toner and paper dust. .

  In the image forming apparatus shown in FIG. 11, a single color mode for forming an image of any one of yellow (Y), magenta (M), cyan (C), and black (K), yellow (Y), magenta ( M), Cyan (C), Black (K) Two-color mode that forms two colors of images, Yellow (Y), Magenta (M), Cyan (C), Black (K) It has a three-color mode in which three-color images are superimposed and a full-color mode in which a four-color superimposed image is formed as described above. Multicolor and full-color image formation is possible.

  In the image forming apparatus having the configuration shown in FIG. 11, a multicolor image is formed on the sheet-like recording medium S through the steps of charging → exposure → development → transfer in each color image forming unit. Instead of the method of transferring directly from the photosensitive drums 1Y, 1M, 1C, 1K to the sheet-like recording medium S, an intermediate transfer medium such as an intermediate transfer belt is used, and the photosensitive drums 1Y, 1M, 1C, 1K are transferred from the intermediate transfer belts. In addition, an intermediate transfer type image forming apparatus may be configured in which a primary transfer is performed to form an overlapping image of each color, and then secondary transfer is collectively performed from the intermediate transfer belt to the sheet-like recording medium S.

As described above, in the image forming apparatus according to the present invention, a multicolor or full-color image is formed on the sheet-like recording medium S through the steps of charging → exposure → development → transfer in the image forming unit of each color. Since the optical scanning device 3 using the phase type optical element 104 of the present invention is used in the above image forming apparatus, the depth margin can be increased while increasing the amount of light passing through the opening of the aperture member. The variation of the beam spot diameter on the body drum can be suppressed, and a high-quality image with a uniform dot diameter can be provided, so that an image forming apparatus that is fast and has high image stability can be realized. it can.
In addition, stabilization of the beam spot diameter on each photosensitive drum means that one of a plurality of process control conditions is stabilized. Therefore, the frequency of process control can be reduced, and the environmental load such as toner consumption reduction and energy saving can be reduced.

In the above-described embodiments, a multicolor image forming apparatus has been described as an example. However, the present invention can be applied to a single color image forming apparatus.
The optical scanning device of the present invention can also be applied to laser scanning laser processing devices, laser measuring devices, and the like.

It is a main scanning sectional view showing a basic configuration example of an optical scanning device. 1 is a perspective view showing a schematic configuration of an optical scanning device developed in a full-color image forming apparatus. It is sectional drawing which shows schematic structure of the optical system after the optical deflector (polygon mirror) of the optical scanning device shown in FIG. (A), (b) is a graph which shows the beam spot diameter vs defocus curve (BD curve) of the main scanning direction. (A) is a graph showing a beam profile (cross section of the center of gravity) in the main scanning direction at an image height of 0 mm and defocus of 0 mm, and (b) is a graph in which a part of (a) is enlarged. It is a figure which shows the Example (simulation result) which compensates the fall of a depth margin using a phase type optical element, Comprising: (a) is a figure (plan view and sectional drawing) which shows an example of a phase type optical element, (b) These are graphs showing the beam spot diameter vs. defocus curve (BD curve) in the main scanning direction when a phase type optical element is used. (A) is a graph showing the beam profile (centroid cross section) in the main scanning direction at an image height of 0 mm and defocus of 0 mm when using a phase type optical element, and (b) is a graph in which a part of (a) is enlarged. is there. It is a figure which shows the example of a shape of the phase modulation part which can increase intensively the side lobe shape of the direction of small Im and Is of a phase type optical element. It is a schematic diagram of the arrangement | sequence of the light emission part of an end surface light emitting laser array, (a) is a figure which shows the example when the arrangement direction of the light emission part of an end surface light emission laser array is set to the subscanning direction, (b) is a light emitting part. It is a figure which shows an example when using it by inclining the arrangement direction from a subscanning difference direction. It is a figure which shows the example of the phase type optical element which increases the side lobe intensity | strength of both the main scanning direction and a subscanning direction. 1 is a schematic configuration diagram illustrating a configuration example of a multi-color image forming apparatus using an optical scanning device according to the present invention.

Explanation of symbols

1 (1Y, 1M, 1C, 1K): surface to be scanned (photosensitive drum)
2Y, 2M, 2C, 2K: Charging device 3: Optical scanning device 4Y, 4M, 4C, 4K: Developing device 5Y, 5M, 5C, 5K: Transfer device 6Y, 6M, 6C, 6K: Cleaning device 10: Transfer belt 20 : Paper cassette 21: Paper feed roller 22: Separation roller 23: Transport roller 24: Registration roller 30: Fixing device 101: Light source 102: Coupling lens 103: Aperture member 104: Phase type optical element 104 a: Phase modulation unit 104 b: Aperture projection unit 105: optical deflector (polygon mirror (deflection means))
108: Soundproof glass 1001: Light source unit 1041: Cylindrical lenses 1061-1064: First scanning lens (L1)
1071-1074: 2nd scanning lens (L2)
1091: Dust-proof glass 1111-1114, 1121-1124: Folding mirror S: Sheet-like recording medium

Claims (15)

A light source;
A coupling lens for coupling divergent light from the light source;
An aperture member having an opening that transmits only a part of the light beam from the light source;
A phase-type optical element that partially changes the phase of a part of the luminous flux;
Deflection means for deflecting and scanning the light beam transmitted through the aperture member;
A scanning lens that forms an image of the scanning beam scanned by the deflecting unit on a surface to be scanned,
When the light intensity at the end portion in the main scanning direction at the opening of the aperture member is Im and the light intensity at the end portion in the sub-scanning direction is Is, the phase type optical element has the beam profile on the surface to be scanned in the beam profile. It has a function of increasing the side lobe strength so that the side lobe increase amount in the smaller direction of Im and Is is larger than the side lobe increase amount in the larger direction of Im and Is. An optical scanning device. The optical scanning device according to claim 1,
An optical scanning device characterized in that the phase modulation portion in the phase type optical element has a shape in which the width in the direction in which the increase amount of the sidelobe light is small is larger. The optical scanning device according to claim 1 or 2,
When the phase modulation unit of the phase type optical element is an aperture projection unit in which the aperture of the aperture member is projected onto the phase type optical element in parallel along the traveling direction of the light beam, at least of the aperture projection unit An optical scanning device characterized by being provided at the center. In the optical scanning device according to any one of claims 1 to 3,
2. The optical scanning device according to claim 1, wherein the phase modulation section has a shape that continues without interruption from one end of the opening to the other end. In the optical scanning device according to any one of claims 1 to 4,
The optical scanning device according to claim 1, wherein the phase modulation unit of the phase type optical element has only one portion. In the optical scanning device according to any one of claims 2 to 5,
An optical scanning device characterized in that the phase modulation section of the phase type optical element has a rectangular shape and a width in a direction in which the increase amount of the sidelobe light is small. The optical scanning device according to claim 6.
When considering an aperture projection part in which the aperture part of the aperture member is projected onto the phase optical element in parallel along the traveling direction of the light beam, is the longer width of the rectangular shape equal to the aperture projection part? Or an optical scanning device characterized by being larger than that. In the optical scanning device according to any one of claims 1 to 7,
The optical scanning device according to claim 1, wherein the opening of the aperture member has a rectangular shape. In the optical scanning device according to any one of claims 1 to 8,
An optical scanning device characterized in that the light source is a surface emitting laser or a surface emitting laser array, and Im <Is. In the optical scanning device according to any one of claims 1 to 8,
The light source is an edge-emitting laser array, and the arrangement direction of the light sources of the edge-emitting laser array is tilted from the sub-scanning direction so that Im <Is. In the optical scanning device according to any one of claims 1 to 10,
The phase type optical element includes a phase modulation unit in the phase type optical element in which the side lobe increase amount in the main scanning direction is larger than the side lobe increase amount in the sub scanning direction, and the side lobe increase amount in the sub scanning direction. An optical scanning device comprising: a phase modulation unit in which phase modulation units of phase type optical elements are superposed such that the amount of the side lobe is larger than the side lobe increase amount in the main scanning direction. The optical scanning device according to claim 11.
An optical scanning device, wherein the phase modulation unit in the phase type optical element includes a shape in which a long shape in the main scanning direction and a long shape in the sub-scanning direction intersect. The optical scanning device according to claim 12, wherein
The optical scanning device characterized in that the long shape in the main scanning direction and the long shape in the sub-scanning direction in the phase modulation unit include a rectangle. An optical scanning device according to any one of claims 1 to 13,
A developing unit that visualizes the electrostatic images formed on the image carrier by the optical scanning device with toner; a transfer unit that transfers the image visualized on the image carrier to a recording medium; An image forming apparatus comprising: a fixing unit that fixes the transferred image to the recording medium. An optical scanning device according to any one of claims 1 to 13,
A developing unit that visualizes the electrostatic images formed on the plurality of image carriers by the optical scanning device with each color toner, and the respective color images that are visualized on the image carrier are superposed on each other to form a recording medium. A multi-color image forming apparatus, comprising: a transfer unit that transfers to the recording medium; and a fixing unit that fixes the transferred image to the recording medium, and outputs a multicolor or color image.

Images