JP2002250884A - Light beam scanning device, image reader using the same, image forming device, and color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of a relative curvatura of scanning lines and to realize the speeding-up and a high resolution. SOLUTION: The device is composed of two light source parts 1 and 2 which have different wavelengths, an optical deflector 9 with which respective luminous fluxes emitted from the light source parts are scanned, a first image-formation optical system which is arranged between the light source parts and the optical deflector and guides respective luminous fluxes emitted from the light source parts upon the deflecting face of the optical deflector, a second image-formation optical system which is arranged between the optical deflector and a plane 13 to be scanned and composed of a single curved mirror 11, and an optical separation means 12 which is arranged between the optical deflector and the plane to be scanned and generates a curvatura of scanning lines. The light source parts, the optical deflector, the first and the second image-formation optical systems are arranged in a way that the luminous fluxes from the first image-formation optical system is made incident diagonally with respect to a plane which includes the normal line of the deflecting plane of the optical deflector and in parallel with the main scanning direction, and the luminous fluxes from the optical deflector is made incident diagonally with respect to a plane which includes the normal line at the vertex of the curved mirror and in parallel with the main scanning direction. Respective luminous fluxes separated by the optical separation means are image-formed on positions which are different in a sub-scanning direction on the plane to be scanned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device used for a laser beam printer, a laser facsimile, a digital copier, and the like, and an image reading device, an image forming device, and a color image forming device using the same.

[0002]

2. Description of the Related Art Many optical scanning devices used in laser beam printers and the like include a semiconductor laser as a light source, a polygon mirror as an optical deflector, and a light source for correcting surface tilt of the optical deflector. And a second imaging optical system that forms a uniform spot at a constant speed on the surface to be scanned.

The second image forming optical system of the conventional optical scanning device is f
Although it is configured using a plurality of large glass lenses called a θ lens, there are problems that it is difficult to reduce the size and it is expensive. Therefore, in recent years, as an optical scanning device that realizes miniaturization and cost reduction, an optical scanning device using one curved mirror in the second imaging optical system has been proposed (Japanese Patent Application Laid-Open Nos. 11-30710 and 11-3011). -15376
No. 4 publication). Further, in order to realize higher-speed printing, a plurality of light sources is required.

[0004]

However, the optical scanning device proposed in the above publication requires a single curved mirror to correct all aberrations, so that the degree of freedom in design is small. For this reason, the amount of change in the imaging magnification in the sub-scanning direction at the scanning center and the periphery becomes large, and a plurality of light sources are used.
When a plurality of scanning lines are formed on the image plane, a change in the imaging magnification in the sub-scanning direction causes a change in the interval between the scanning lines (relative scanning line curvature), which makes it difficult to achieve high image quality. There is a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art.
Even when a plurality of light sources of the optical scanning device composed of a plurality of curved mirrors are used, the occurrence of relative scanning line curvature is suppressed,
It is an object of the present invention to provide an optical scanning device capable of realizing low cost, high speed, and high resolution.

[0006]

To achieve the above object, a first configuration of an optical scanning device according to the present invention is to scan at least two light sources having different wavelengths and light beams from the light sources. A light deflector, a first imaging optical system disposed between the light source unit and the light deflector, and guiding each light beam from the light source unit onto a deflection surface of the light deflector; A second imaging optical system, which is arranged between the optical deflector and the surface to be scanned, and is also arranged between the optical deflector and the surface to be scanned, and separates a light beam and scans the light. A light separating unit that generates line curvature, wherein the light source unit, the light deflector, the first imaging optical system, and the second imaging optical system are configured to perform the first imaging. The light beam from the optical system is inclined with respect to a plane parallel to the main scanning direction and including a normal to the deflection surface of the optical deflector. And the light flux from the optical deflector is disposed so as to be obliquely incident on a plane (YZ plane) including a normal line at the vertex of the curved mirror and parallel to the main scanning direction, and is arranged by the light separating means. Each of the separated light beams forms an image at a different position on the surface to be scanned in the sub-scanning direction.

According to the first configuration of this optical scanning device, the scanning line curvature generated by the light separating means is generated in the direction for correcting the relative scanning line curvature between scanning lines on the surface to be scanned of each light beam. Therefore, high speed and high resolution can be realized.

Further, in the first configuration of the optical scanning device according to the present invention, the second imaging optical system generates the scanning line curvature in a direction for correcting the scanning line curvature generated by the light separating means. Is preferred. According to this preferred configuration, it is possible to easily realize high resolution.

In the first configuration of the optical scanning device according to the present invention, it is preferable that a light combining unit is further provided between the light source units having different wavelengths and the optical deflector. According to this preferred configuration, two inexpensive light sources can be used without requiring a special light source that emits light beams of two different wavelengths. In addition, as the photosynthesis means, for example,
A dichroic mirror can be used.

Further, in the first configuration of the optical scanning device according to the present invention, it is preferable that reflection positions of the respective light beams from the light sources having different wavelengths on the curved mirror are different in the sub-scanning direction. In this case, the reflection position of each light beam on the curved mirror has a small change (relative scanning line curvature) in the sub-scanning direction interval between the imaging positions of each light beam in the entire effective scanning area on the surface to be scanned. It is preferable that they are shifted in a direction (a direction in which the relative scanning line curvature is corrected). Further, in this case, the reflection position of each light beam on the curved mirror is shifted in the direction in which the interval in the sub-scanning direction between the image forming positions of each light beam in the entire effective scanning area on the scanned surface is shifted. preferable.
According to these preferred configurations, it is possible to realize high resolution by setting each scanning line to a desired interval.

In the first configuration of the optical scanning device according to the present invention, it is preferable that incident angles of the respective light beams from the light sources having different wavelengths to the curved mirror are different in the sub-scanning direction. In this case, when the angle of incidence of each light beam on the curved mirror is small, the change in the interval in the sub-scanning direction between the image forming positions of each light beam in the entire effective scanning area on the surface to be scanned (relative scanning line curvature) is small. It is preferable that they are shifted in a direction (a direction in which the relative scanning line curvature is corrected). Also, in this case,
It is preferable that the angle of incidence of each light beam on the curved mirror is shifted in a direction in which the distance between the image forming positions of each light beam in the sub-scanning direction in the entire effective scanning area on the surface to be scanned increases. According to these preferred configurations, it is possible to realize high resolution by setting each scanning line to a desired interval.

Further, the reflection position on the curved mirror and the angle of incidence on the curved mirror may be different from each other.

In the first configuration of the optical scanning device according to the present invention, it is preferable that the light separating means is a prism. If a prism is used as the light separating means, light beams having different wavelengths can be separated by a difference in refractive index. Also, in this case, the different wavelength is λA
, ΛB, the angle between the entrance surface and the exit surface of the prism is θpz, the distance between the exit surface of the prism and the surface to be scanned in the optical path of wavelength λA is D, and the wavelength λA of the material forming the prism is Assuming that the refractive index is nA, the refractive index at the wavelength λB is nB, and the interval in the sub-scanning direction between the imaging positions of the light beams of the respective wavelengths at the scanning center is xd, the following conditional expressions (4) to (6) are obtained. It is preferable to satisfy.

[0014]

(Equation 4)

[0015]

(Equation 5)

[0016]

(Equation 6)

According to this preferred embodiment, the relative scanning line curvature is corrected, and high resolution can be realized.

In a second configuration of the optical scanning device according to the present invention, at least two light source units, an optical deflector for scanning each light beam from the light source unit, the light source unit and the optical deflector are provided. And a first imaging optical system that forms a line image on the deflection surface of the optical deflector, and one curved mirror that is disposed between the optical deflector and the surface to be scanned. An optical scanning device comprising: a second imaging optical system; and a sub-scanning direction control unit that changes a tilt or a height of at least one light beam in a sub-scanning direction, wherein the light source unit, the optical deflector, First
The image forming optical system and the second image forming optical system are arranged such that a light beam from the first image forming optical system is inclined with respect to a plane including a normal to the deflecting surface of the optical deflector and parallel to a main scanning direction. And the light flux from the optical deflector is arranged so as to be obliquely incident on a plane (YZ plane) including a normal line at the vertex of the curved mirror and parallel to the main scanning direction.

According to the second configuration of this optical scanning device, the sub-scanning direction control means can control the image forming position of at least one light beam on the surface to be scanned in the sub-scanning direction. The relative scanning line curvature between the scanning lines on the surface to be scanned can be corrected, and high speed and high resolution can be realized.

Further, in the second configuration of the optical scanning device according to the present invention, the sub-scanning direction control means may include an imaging position of a light beam from each of the light source units in an effective scanning area on the surface to be scanned. It is preferable to control the inclination or height in the sub-scanning direction so that the change in the interval in the sub-scanning direction becomes smaller. According to this preferred configuration, it is possible to easily realize high resolution.

Further, in the second configuration of the optical scanning device according to the present invention, it is preferable that the sub-scanning direction control means is disposed between the light source unit and the optical deflector. According to this preferred configuration, control becomes easy.

As the sub-scanning direction control means, for example, a prism or a galvanometer mirror can be used.

Further, the configuration of the image reading device according to the present invention is characterized in that the optical scanning device of the present invention is used as the optical scanning device.

Further, the configuration of the image forming apparatus according to the present invention is characterized in that the optical scanning device of the present invention is used as the optical scanning device.

Further, the configuration of the color image forming apparatus according to the present invention comprises a plurality of image forming units which are held so as to form a cylinder and correspond to a plurality of colors including a developing device and a photosensitive member, and a shaft of the cylinder. A transfer unit that moves each image forming unit between an image forming position and a standby position by simultaneously rotating the plurality of image forming units around a center, and the image forming unit that is located at the image forming position. A transfer member is brought into contact with a photoreceptor, and with the switching of the image forming unit located at the image forming position, the toner images of each color formed on each photoreceptor are sequentially transferred to the transfer member, and the toner of each color is transferred. 2. A color image forming apparatus comprising: transfer means for forming a color toner image on the transfer body by superimposing images; and an optical scanning device for exposing the photoconductor, wherein the optical scanning device is used as the optical scanning device. Characterized by using the optical scanning apparatus according to any one of 17.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to embodiments.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
FIG. 2 is a perspective view showing a configuration of an optical scanning device according to the embodiment.

In FIG. 1, reference numeral 1 denotes a first semiconductor laser as a light source unit that emits a light beam having a wavelength of 780 nm, 2 denotes a second semiconductor laser that emits a light beam having a wavelength of 670 nm, and 9 denotes a first and a second semiconductor laser. A polygon mirror as an optical deflector for scanning each light beam from the semiconductor lasers 1 and 2;
Is a first light beam which is a convergence light beam from the first semiconductor laser 1.
4 is a second axially symmetric lens that converges the light beam from the second semiconductor laser 2 as convergent light, and 5 has refractive power only in the sub-scanning direction. 1
First, the light flux from the semiconductor laser 1 is formed as a line image.
A second cylindrical lens 6 having a refractive power only in the sub-scanning direction and forming a light beam from the second semiconductor laser 2 as a linear image on the deflection surface of the polygon mirror 9; Transmit a 780 nm light flux,
A dichroic mirror as a light combining means for reflecting a light beam having a wavelength of 670 nm, and a folding mirror 8. Here, the first axially symmetric lens 3, the first cylindrical lens 5, the dichroic mirror 7, and the folding mirror 8
Is disposed between the first semiconductor laser 1 and the polygon mirror 9, and functions as a first imaging optical system for guiding a light beam from the first semiconductor laser 1 onto the deflection surface of the polygon mirror 9. I do. Similarly, an optical system including the second axially symmetric lens 4, the second cylindrical lens 6, the dichroic mirror 7, and the folding mirror 8 is disposed between the second semiconductor laser 2 and the polygon mirror 9,
It functions as a first imaging optical system for guiding the light beam from the second semiconductor laser 2 onto the deflection surface of the polygon mirror 9. Also,
13 is a photosensitive drum as a surface to be scanned, 12 is disposed between the polygon mirror 9 and the photosensitive drum 13, and has a wavelength of 780.
A prism 10 serving as a light separating unit for separating a light beam having a wavelength of 670 nm and a light beam having a wavelength of 670 nm is a rotation center axis of the polygon mirror 9. Reference numeral 11 denotes a curved mirror that is disposed between the polygon mirror 9 and the prism 12, and functions as a second imaging optical system that generates a scanning line curve in a direction in which the scanning line curve generated by the prism 12 is corrected.

In this optical scanning device, each light beam (a light beam having a wavelength of 780 nm and a light beam having a wavelength of 670 nm) from the first and second semiconductor lasers 1 and 2 is reflected at different positions on the curved mirror 11 in the sub-scanning direction. It is configured to be.
In this case, the reflection position of each light beam on the curved mirror 11 is set in such a direction that the change of the interval (relative scanning line curvature) in the sub-scanning direction between the image formation positions of each light beam in the entire effective scanning area on the photosensitive drum 13 is reduced. It is desirable that they are shifted. In this case, it is desirable that the reflection position of each light beam on the curved mirror 11 is shifted in the direction in which the interval in the sub-scanning direction between the image forming positions of each light beam in the entire effective scanning area on the photosensitive drum 13 is widened.

In the present optical scanning device, each light beam (wavelength 780 n) from the first and second semiconductor lasers 1 and 2 is used.
The angle of incidence of the light beam of m and the light beam of 670 nm in wavelength on the curved mirror 11 is different in the sub-scanning direction.
In this case, the angle of incidence of each light beam on the curved mirror 11 is set so that the change in the interval (relative scanning line curvature) of the image forming position of each light beam in the sub-scanning direction over the entire effective scanning area on the photosensitive drum 13 is reduced. It is desirable that they are shifted. In this case, it is desirable that the angle of incidence of each light beam on the curved mirror 11 be shifted in the direction in which the distance between the image forming positions of each light beam in the sub-scanning direction in the entire effective scanning area on the photosensitive drum 13 increases.

FIG. 2 is a cross-sectional view of the optical scanning device of FIG. 1 cut along a plane including the scanning center axis and parallel to the sub-scanning direction. FIG.
As shown in (1), each member of the present optical scanning apparatus is configured such that the light beam from the folding mirror 8 constituting the first imaging optical system is parallel to the plane parallel to the main scanning direction including the normal to the deflection surface of the polygon mirror 9. Obliquely in the sub-scanning direction so that the light beam from the polygon mirror 9 is obliquely incident on a plane (YZ plane) including the normal at the apex of the curved mirror 11 and parallel to the main scanning direction. Are located.

In FIG. 2, r is the inscribed radius of the polygon mirror 9, D1 is the distance between the deflecting reflection point of the polygon mirror 9 and the curved mirror 11, D2 is the distance between the curved mirror 11 and the exit surface of the prism 12, D3. Is the distance between the exit surface of the prism 12 and the photosensitive drum 13 in the optical path of the wavelength of 780 nm, θp
Is the angle between the optical axis of the light beam from the return mirror 8 and the normal to the deflection surface of the polygon mirror 9, and θm is the polygon mirror 9
Is the angle between the optical axis of the light beam from the deflecting surface and the normal at the vertex of the curved mirror 11, and θpz is the angle between the entrance surface and the exit surface of the prism 12. The refractive index of the glass material (Bk7) forming the prism 12 at a wavelength of 780 nm is 1.511183, the refractive index at a wavelength of 670 nm is 1.513905, and the center thickness of the prism 12 is 5 mm.

The surface shape of the curved mirror 11 is such that the coordinates in the sub-scanning direction with the vertex of the surface as the origin and the coordinates in the main scanning direction are x.
The sag amount from the vertex at the position of (mm) and y (mm) is defined by the following (Equation 7) to (Equation 10) as z (mm) (the direction in which the reflected light flux is directed is positive).

[0034]

(Equation 7)

[0035]

(Equation 8)

[0036]

(Equation 9)

[0037]

(Equation 10)

Here, (Equation 8) is an equation showing a non-circular arc which is a shape on the generating line, (Equation 9) is an equation showing a radius of curvature in the sub-scanning direction (x direction) at the y position. 10)
Is an expression indicating the amount of twist at the y position. Note that RDy
(Mm) is the radius of curvature of the vertex in the main scanning direction, RDx
(Mm) is the radius of curvature in the sub-scanning direction. K is a conic constant indicating the bus shape, AD, AE, AF, and AG are higher-order constants indicating the bus shape, and BC, BD, BE, BF, and BG are constants that determine the radius of curvature in the sub-scanning direction at the y position. E
C, ED, and EE are torsion constants that determine the amount of torsion at the y position.

The following are specific numerical examples. The maximum image height is Ymax, and the corresponding polygon rotation angle is αmax.

(Numerical Example 1)

[0041]

[Table 1]

(Numerical example 2)

[0043]

[Table 2]

(Numerical example 3)

[0045]

[Table 3]

Hereinafter, the operation of the optical scanning device configured as described above will be described with reference to FIGS.

The wavelength 780 n from the semiconductor lasers 1 and 2
The light beams of m and 670 nm are converged by the axisymmetric lenses 3 and 4, respectively, and converged only in the sub-scanning direction by the cylindrical lenses 5 and 6, respectively. The light having a wavelength of 780 nm transmitted through the cylindrical lens 5 is transmitted through the dichroic mirror 7, and the light having a wavelength of 670 nm transmitted through the cylindrical lens 6 is transmitted through the dichroic mirror 7.
And the two light beams are combined. After the two combined light beams are turned back by the turning mirror 8, they are formed as a line image on the deflecting surface (reflecting surface) of the polygon mirror 9. When the polygon mirror 9 rotates around the rotation center axis 10, the light flux formed as a line image is scanned by the polygon mirror 9, and is converged by the curved mirror 11. The luminous flux converged by the curved mirror 11 is separated into two luminous fluxes by the prism 12 and then imaged on the photosensitive drum 13.

The curved mirror 11 corresponds to the non-arc shape of the cross section in the main scanning direction and each image height so as to correct the field curvature in the main scanning direction, the field curvature in the sub scanning direction, and the fθ error. The radius of curvature in the sub-scanning direction is determined. Further, the curved mirror 11 has a torsion amount of a surface at a position corresponding to each image height so that oblique incidence on the polygon mirror 9 and the curved mirror 11 and a scanning line curvature generated by the prism 12 can be corrected. It is decided.

When the two light beams are combined in exactly the same light path, assuming that the incident surface of the prism 12 is arranged perpendicular to the optical axis of the light beam in the sub-scanning direction (see FIG. 2), the surface to be scanned is The interval x0 between the imaging positions of the two light beams at the upper scanning center is defined by the following (Equation 11) to (Equation 13).

[0050]

[Equation 11]

[0051]

(Equation 12)

[0052]

(Equation 13)

Since the amount of curvature of the scanning line when refracted by the prism 12 is different between the two light beams due to the difference in wavelength, if the two light beams are combined in exactly the same optical path, the photosensitive drum 13 Above, a relative scan line curvature occurs. FIG. 3 shows the relationship between relative scanning line curvature and image height in the case of Numerical Example 1.

In this embodiment, the light beam having a wavelength of 670 nm is shifted and tilted in the sub-scanning direction so that the relative scanning line curvature generated by the prism 12 can be corrected. The following Table 4 shows the shift amount ΔMx and tilt amount Δ in the curved mirror 11 of each of Numerical Examples 1 to 3.
Mβ, the distance xd between the two scanning lines in a state where the relative scanning line curvature is corrected (the distance in the sub-scanning direction between the image forming positions of light beams of each wavelength at the scanning center).

[0055]

[Table 4]

As can be seen from the above (Table 4), x0 <x
The relative scanning line curvature is corrected in the state of d.

FIGS. 4 and 5 show the characteristics of Numerical Example 1, FIGS. 6 and 7 show the characteristics of Numerical Example 2, and FIGS. 8 and 9 show the characteristics of Numerical Example 3. FIG. In each figure,
(A) and (b) show the characteristics of a light beam having a wavelength of 780 nm, (a) shows the fθ error, and (b) shows the amount of field curvature. (C) shows the scanning line curvature of a light beam having a wavelength of 780 nm, and (d) shows the scanning line curvature of a light beam having a wavelength of 670 nm. Since the second imaging optical system is constituted only by the mirror (curved mirror 11), the performance change due to the difference in wavelength does not matter for the fθ error and the field curvature.

Here, the fθ error (ΔY) is the scanning speed per unit rotation angle of the polygon mirror 9 near the scanning center (the speed at which the light beam is scanned on the surface of the photosensitive drum 13).
Is V (mm / deg), the rotation angle of the polygon mirror 9 is α (deg),
When the image height is Y (mm), this is the amount indicated by the following (Equation 14).

[0059]

[Equation 14]

In the present embodiment, the surface shape of the curved mirror 11 is defined by the above (Equation 7) to (Equation 10). However, if the same shape can be represented, other expressions are used. May be used.

In the present embodiment, the incident surface of the prism 12 is arranged perpendicular to the optical axis of the light beam, but the incident surface of the prism 12 is inclined with respect to the optical axis of the light beam. Even if designed, similar performance can be obtained.

[Second Embodiment] FIG. 10 is a perspective view showing a configuration of an optical scanning device according to a second embodiment of the present invention.

In FIG. 10, reference numeral 14 denotes a first semiconductor laser serving as a light source for emitting a light beam having a wavelength of 780 nm;
Denotes a second semiconductor laser as a light source unit that emits a light beam having a wavelength of 670 nm, and 23 denotes a first and second semiconductor laser 1.
A polygon mirror as an optical deflector that scans each light beam from 4 and 15; 16 is a first axially symmetric lens that converges the light beam from the first semiconductor laser 14; A second axially symmetric lens 18 having a convergent light beam has a refractive power only in the sub-scanning direction, and forms a light beam from the first semiconductor laser 14 as a line image on the deflection surface of the polygon mirror 23. A first cylindrical lens 19 having a refractive power only in the sub-scanning direction, and forming a light beam from the second semiconductor laser 15 on the deflection surface of the polygon mirror 23 as a linear image;
20 transmits a light beam having a wavelength of 780 nm and a wavelength of 670 n
A dichroic mirror 21 as a light synthesizing means for reflecting the light flux of m is disposed between the second cylindrical lens 19 and the dichroic mirror 20, and the light flux from the second semiconductor laser 15 in the sub-scanning direction is driven by a piezoelectric element or the like. A prism 22 as a sub-scanning direction control means capable of changing the inclination is a folding mirror. Here, the optical system including the first axially symmetric lens 16, the first cylindrical lens 18, the dichroic mirror 20, and the folding mirror 22 is disposed between the first semiconductor laser 14 and the polygon mirror 23, Functions as a first imaging optical system for guiding the light beam from the semiconductor laser 14 onto the deflection surface of the polygon mirror 23. Similarly, the second axially symmetric lens 17 and the second cylindrical lens 1
9, an optical system including a prism 21, a dichroic mirror 20, and a folding mirror 22 is disposed between the second semiconductor laser 15 and the polygon mirror 23, and deflects a light beam from the second semiconductor laser 15 to the polygon mirror 23. It functions as a first imaging optical system for guiding on a surface. Also, 26
Is a photosensitive drum as a surface to be scanned, 24 is a rotation center axis of the polygon mirror 23, 25 is a curved mirror disposed between the polygon mirror 23 and the photosensitive drum 26 and functioning as a second imaging optical system.

Prism 21 as sub-scanning direction control means
Are the light source units (the first and second semiconductor lasers 1) in the entire effective scanning area on the photosensitive drum 26 as the surface to be scanned.
It is desirable to control the inclination in the sub-scanning direction in a direction in which the change in the interval in the sub-scanning direction of the image forming position of the light beam from the sub-scanning direction is reduced.

FIG. 11 is a cross-sectional view of the optical scanning device of FIG. 10 cut along a plane including the scanning center axis and parallel to the sub-scanning direction.
As shown in FIG. 11, each member of the optical scanning device has a surface in which a light beam from the folding mirror 22 constituting the first imaging optical system is parallel to the main scanning direction and includes a normal to the deflection surface of the polygon mirror 23. And the light from the polygon mirror 23 is arranged obliquely in the sub-scanning direction so that the light flux from the polygon mirror 23 is obliquely incident on a plane including the normal line at the vertex of the curved surface mirror 25 and parallel to the main scanning direction. ing.

In FIG. 11, r is the inscribed radius of the polygon mirror 23, D1 is the distance between the deflecting reflection point of the polygon mirror 23 and the curved mirror 25, D2 is the distance between the curved mirror 25 and the photosensitive drum 26, and θp is the turnback. The angle between the optical axis from the mirror 22 and the normal to the deflection surface of the polygon mirror 23, and θm is the angle between the optical axis of the light beam from the deflection surface of the polygon mirror 23 and the normal to the vertex of the curved mirror 25. .

The surface shape of the curved mirror 25 is the same as that in the first embodiment (Equation 7) to (Equation 1).
0).

The following are specific examples of numerical values. The maximum image height is Ymax, and the corresponding polygon rotation angle is αmax.

(Numerical example 4)

[0070]

[Table 5]

Hereinafter, the operation of the optical scanning device configured as described above will be described with reference to FIGS.

The light beams of two different wavelengths synthesized by the dichroic mirror 20 are scanned by the polygon mirror 23 and converged by the curved mirror 25. The light flux converged by the curved mirror 25 forms an image on the photosensitive drum 26. In this case, the wavelength 670n from the second semiconductor laser 15 is set so that the positions of incidence of the two light beams on the curved mirror 25 are slightly different in the sub-scanning direction.
The light beam of m is tilted by a small angle by the prism 21, and two scanning lines are formed on the photosensitive drum 26 although not shown.

FIG. 12 shows a wavelength 780n in the case of Numerical Example 4.
This shows the characteristics of the light flux of m. In FIG. 12, (a) is fθ
The error, (b) shows the curvature of field, and (c) shows the curvature of the scanning line. FIG. 13 shows the amount of curvature of the scanning line of a light beam having a wavelength of 670 nm generated when the interval between two scanning lines on the photosensitive drum 26 is 43 μm and control is not performed. In the present embodiment, the prism 21 is controlled so as to correct the relative scanning line curvature.

In this embodiment, the prism 21 is used as sub-scanning direction control means capable of changing the inclination of the light beam from the second semiconductor laser 15 in the sub-scanning direction.
Is used, but is not necessarily limited to this. For example, a galvanometer mirror may be used, or a dichroic mirror may be used to control the inclination.

In the present embodiment, the inclination of the light beam from the semiconductor laser in the sub-scanning direction is changed by using the sub-scanning direction control means. However, the present invention is not necessarily limited to this configuration. Instead, the height of the light beam from the semiconductor laser in the sub-scanning direction may be changed.

Further, in this embodiment, the prism 21 as the sub-scanning direction control means is disposed between the second cylindrical lens 19 and the dichroic mirror 20, but is not necessarily limited to this configuration. is not. The sub-scanning direction control means may be arranged between the light source unit (second semiconductor laser 15) and the optical deflector (polygon mirror 23).

[Third Embodiment] FIG. 14 is a perspective view showing the structure of an image reading apparatus according to a third embodiment of the present invention.

In FIG. 14, reference numerals 1 to 12 denote members of the optical scanning device according to the first embodiment shown in FIG. Reference numeral 27 denotes a reading surface, and 28 and 29 transmit light beams from the respective semiconductor lasers 1 and 2, and the reading surface 2
Half mirror for reflecting the return light from 7 to the detection system, 3
Reference numerals 0 and 31 denote detectors, and reference numerals 32 and 33 denote detection optical systems that guide return light to the detectors 30 and 31.

As described above, by using the optical scanning device of the first embodiment as the optical scanning device of the image reading device, a high-speed and high-resolution image reading device can be realized.

In the image reading device of the present embodiment, the optical scanning device of the first embodiment is used as the optical scanning device. However, the present invention is not necessarily limited to this configuration. The optical scanning device according to the second embodiment may be used.

[Fourth Embodiment] FIG. 15 is a schematic sectional view showing the structure of an image forming apparatus according to a fourth embodiment of the present invention. The optical scanning device of the second embodiment is used as the optical scanning device of the image forming apparatus.

In FIG. 15, reference numeral 34 denotes a photosensitive drum whose surface is covered with a photosensitive member whose charge changes when irradiated with light;
Reference numeral 5 denotes a primary charger for attaching and charging electrostatic ions on the surface of the photoreceptor; 36, a developer for attaching charged toner to a printing portion; 37, a transfer charger for transferring the attached toner to paper; A cleaner 39 for removing the toner, a fixing device 39 for fixing the transferred toner to the sheet, a paper cassette 40, a light source block 41 composed of a semiconductor laser, an axisymmetric lens, a cylindrical lens, a prism and a dichroic mirror, 42 Is a polygon mirror, 4
3 is a curved mirror.

As described above, a high-speed and high-resolution image forming apparatus can be realized by using the optical scanning apparatus of the second embodiment as the optical scanning apparatus of the image forming apparatus.

In the image forming apparatus of this embodiment, the optical scanning device of the second embodiment is used as the optical scanning device. However, the present invention is not necessarily limited to this configuration. The optical scanning device according to the first embodiment may be used.

[Fifth Embodiment] FIG. 16 is a schematic sectional view showing the structure of a color image forming apparatus according to a fifth embodiment of the present invention. The optical scanning device of the second embodiment is used as an optical scanning device of the color image forming apparatus.

In FIG. 16, 44Y, 44M, 44
C and 44B are image forming units corresponding to the respective colors of yellow, magenta, cyan, and black.
Each of the image forming units 45 is a photosensitive drum whose surface is covered with a photosensitive member whose charge changes when irradiated with light, and 46 is a primary drum which is charged by attaching electrostatic ions to the surface of the photosensitive member. A charger 47 is a developing device for attaching the charged toner to the printing section, and a cleaner 48 is for removing the remaining toner. Reference numeral 49 denotes a transfer belt on which a toner image formed on the photosensitive drum 45 of each color is transferred; 50, a transfer charger for transferring toner adhered to the transfer belt 49 to paper;
Reference numeral 51 denotes a fixing device for fixing the transferred toner to paper,
Reference numeral 2 denotes a paper feed cassette; 53, a light source block including a semiconductor laser, an axisymmetric lens, a cylindrical lens, a prism, and a dichroic mirror; 54, a polygon mirror; and 55, a curved mirror.

Image forming units 44Y and 4 corresponding to four colors
4M, 44C, 44B are held to form a cylinder. Then, by simultaneously rotating the image forming units 44Y, 44M, 44C, and 44B around the axis of the cylinder, the image forming units 44Y, 44M, 44C,
44B is positioned at the image forming position (in FIG.
5B) and the standby position. Thereby, each photosensitive drum 45Y, 45M, 45
The toner images of the respective colors formed on C and 45B are sequentially transferred to the transfer belt 49, and the toner images of the respective colors are superimposed to form a color toner image on the transfer belt 49.

The light source block 53, the polygon mirror 54,
The optical scanning device constituted by the curved mirror 55 is designed such that the reflection angle of the light beam by the curved mirror 55 is 30 (deg) which is optimal for the color image forming apparatus of the present embodiment. Therefore, only the curved mirror 55 is disposed near the axis of the cylinder, and the light beam reflected by the curved mirror 55 is directly guided to the photosensitive drums 45Y, 45M, 45C, and 45B.

As described above, by using the optical scanning device of the second embodiment as the optical scanning device of the color image forming device, a high-speed and high-resolution color image forming device can be realized.

[0090]

As described above, according to the present invention,
The second scanning optical system is constituted by only one curved mirror, and the relative scanning line curvature, which is a problem when a plurality of light sources are used, is described below.
Since the correction is performed using the prism or the sub-scanning direction control means, high-speed and high-resolution can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an optical scanning device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the optical scanning device of FIG. 1 cut along a plane including a scanning center axis and parallel to a sub-scanning direction.

FIG. 3 is a diagram illustrating a relationship between relative scanning line curvature and image height in the case of Numerical Example 1 according to the first embodiment of the present invention.

FIGS. 4A and 4B are characteristic diagrams of a luminous flux having a wavelength of 780 nm in the case of Numerical Example 1 according to the first embodiment of the present invention, wherein FIG. 4A illustrates an fθ error, and FIG.

5A and 5B are characteristic diagrams of Numerical Example 1 according to the first embodiment of the present invention, in which FIG. 5C shows a scanning line curvature of a light beam having a wavelength of 780 nm, and FIG. 5D shows a scanning line curve of a light beam having a wavelength of 670 nm. Figure showing each

6A and 6B are characteristic diagrams of a luminous flux having a wavelength of 780 nm in Numerical Example 2 according to the first embodiment of the present invention, where FIG. 6A illustrates an fθ error, and FIG. 6B illustrates an amount of field curvature.

FIGS. 7A and 7B are characteristic diagrams of Numerical Example 2 according to the first embodiment of the present invention, in which FIG. 7C illustrates a scanning line curvature of a light beam having a wavelength of 780 nm, and FIG. Figure showing each

8A and 8B are characteristic diagrams of a light beam having a wavelength of 780 nm in the case of Numerical Example 3 according to the first embodiment of the present invention, where FIG. 8A illustrates an fθ error, and FIG.

FIGS. 9A and 9B are characteristic diagrams of Numerical Example 3 according to the first embodiment of the present invention, in which FIG. 9C illustrates a scanning line curvature of a light beam having a wavelength of 780 nm, and FIG. Figure showing each

FIG. 10 is a perspective view illustrating a configuration of an optical scanning device according to a second embodiment of the present invention.

FIG. 11 is a cross-sectional view of the optical scanning device of FIG. 10 cut along a plane including a scanning center axis and parallel to a sub-scanning direction.

FIG. 12 is a numerical example 4 according to the second embodiment of the present invention.
FIGS. 7A and 7B are characteristic diagrams in the case of FIG. 7A, where FIG. 7A shows an fθ error, FIG. 7B shows an image surface curvature amount, and FIG.

FIG. 13 is a diagram illustrating a scanning line bending amount of a light beam having a wavelength of 670 nm generated when control is not performed according to the second embodiment of the present invention.

FIG. 14 is a perspective view illustrating a configuration of an image reading apparatus according to a third embodiment of the present invention.

FIG. 15 is a schematic sectional view showing the configuration of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 16 is a schematic sectional view illustrating a configuration of a color image forming apparatus according to a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st semiconductor laser 2 2nd semiconductor laser 3 1st axis symmetric lens 4 2nd axis symmetric lens 5 1st cylindrical lens 6 2nd cylindrical lens 7 Dichroic mirror 8 Folding mirror 9 Polygon mirror 10 Polygon mirror Center axis of rotation 11 curved mirror 12 prism 13 photosensitive drum 14 first semiconductor laser 15 second semiconductor laser 16 first axially symmetric lens 17 second axially symmetric lens 18 first cylindrical lens 19 second cylindrical lens Reference Signs List 20 dichroic mirror 21 prism 22 folding mirror 23 polygon mirror 24 rotation center axis 25 curved mirror 26 photosensitive drum 27 reading surface 28 half mirror 29 half mirror 30 detector 31 detector 32 detection optical system 33 detection optical system 34 sensitivity Optical drum 35 Primary charger 36 Developing device 37 Transfer charger 38 Cleaner 39 Fixing device 40 Paper cassette 41 Light source block 42 Polygon mirror 43 Curved mirror 44 Image forming unit 45 Photosensitive drum 46 Primary charger 47 Developing device 48 Cleaner 49 Transfer belt Reference Signs List 50 transfer charger 51 fixing device 52 paper feed cassette 53 light source block 54 polygon mirror 55 curved mirror

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 17/08 B41J 3/00 D H04N 1/113 H04N 1/04 104A (72) Inventor Daisaburo Matsuki Osaka 1006 Kadoma Kadoma Matsushita Electric Industrial Co., Ltd. (72) Inventor Hajime Yamamoto 1006 Kadoma Kadoma, Osaka Pref. Within Sangyo Co., Ltd. LA22 RA08 RA13 RA41 RA45 TA01 TA03 TA06 5C072 AA03 BA01 BA03 BA16 DA04 DA06 DA10 HA02 HA06 HA13 XA05

Claims (20)

[Claims] 1. A light source unit having at least two different wavelengths, a light deflector for scanning each light beam from the light source unit, and a light deflector disposed between the light source unit and the light deflector. A first imaging optical system for guiding each light beam onto a deflection surface of the light deflector, and a first imaging optical system disposed between the light deflector and the surface to be scanned;
A second imaging optical system including one curved mirror; and a light separating unit that is also disposed between the optical deflector and the surface to be scanned and separates a light beam and generates a scanning line curve. An optical scanning device, wherein the light source unit, the optical deflector, the first imaging optical system, and the second imaging optical system are configured such that a light flux from the first imaging optical system The light is obliquely incident on a plane including the normal of the deflecting surface and parallel to the main scanning direction, and the light flux from the optical deflector includes a normal (YZ) including the normal at the vertex of the curved mirror and parallel to the main scanning direction. An optical scanning device, which is disposed so as to be obliquely incident on a surface, and forms an image of each light beam separated by the light separating means at a different position in the sub-scanning direction on the surface to be scanned. 2. The optical scanning device according to claim 1, wherein the second imaging optical system generates a scanning line curvature in a direction in which the scanning line curvature generated by the light separating unit is corrected. 3. The optical scanning device according to claim 1, further comprising a light combining unit between the light source units having different wavelengths and the optical deflector. 4. The optical scanning device according to claim 3, wherein said light combining means is a dichroic mirror. 5. The optical scanning device according to claim 1, wherein reflection positions of the respective light beams from the light source units having different wavelengths on the curved mirror are different in the sub-scanning direction. 6. A change in a sub-scanning direction interval between image forming positions of respective light beams in the entire effective scanning area on the surface to be scanned, where a reflection position of each light beam on the curved mirror is changed (relative scanning line curvature).
The optical scanning device according to claim 5, wherein the optical scanning device is shifted in a direction in which is smaller. 7. The method according to claim 5, wherein the reflection position of each light beam on the curved mirror is shifted in a direction in which an interval between image forming positions of each light beam in the sub-scanning direction in the entire effective scanning area on the surface to be scanned increases. The optical scanning device according to claim 1. 8. The optical scanning device according to claim 1, wherein incident angles of the light beams from the light source units having different wavelengths to the curved mirror are different in the sub-scanning direction. 9. An angle of incidence of each light beam on the curved mirror,
The optical scanning device according to claim 8, wherein a change in an interval (relative scanning line curvature) of an image forming position of each light beam in the sub-scanning direction in the entire effective scanning area on the surface to be scanned is shifted. 10. The method according to claim 8, wherein the angle of incidence of each light beam on the curved mirror is shifted in a direction in which the distance between the image forming positions of each light beam in the sub-scanning direction in the entire effective scanning area on the surface to be scanned increases. The optical scanning device according to claim 1. 11. The optical scanning device according to claim 1, wherein said light separating means is a prism. 12. The different wavelengths are λA and λB, the angle between the entrance surface and the exit surface of the prism is θpz, and the wavelength λA
D is the distance between the exit surface of the prism and the surface to be scanned in the optical path, and the wavelength λA of the material forming the prism.
Is the refractive index at nA, and the refractive index at wavelength λB is nB.
Where xd is the distance in the sub-scanning direction between the image forming positions of the light beams of each wavelength at the scanning center, the following (Equation 1) to (Equation 3)
The optical scanning device according to claim 11, wherein the following conditional expression is satisfied. (Equation 1) (Equation 2) (Equation 3) 13. At least two light source units, an optical deflector for scanning each light beam from the light source unit, and disposed between the light source unit and the optical deflector, on a deflection surface of the optical deflector. A first image forming optical system for forming a linear image on the surface, a second image forming optical system disposed between the optical deflector and the surface to be scanned, and including one curved mirror, An optical scanning device comprising: a sub-scanning direction controller for changing a tilt or a height in a scanning direction, wherein the light source unit, the optical deflector, the first imaging optical system, and the second imaging optical system are provided. A light beam from the first imaging optical system is obliquely incident on a plane parallel to the main scanning direction including a normal to the deflection surface of the light deflector, and the light beam from the light deflector is Incident obliquely to a plane (YZ plane) that includes the normal line at the vertex of the curved mirror and that is parallel to the main scanning direction An optical scanning device characterized by being arranged as follows. 14. The sub-scanning direction control means controls the sub-scanning direction in a direction in which the change in the interval in the sub-scanning direction of the image forming position of the light beam from each of the light source units is reduced over the entire effective scanning area on the surface to be scanned. The inclination or height of the direction is controlled.
4. The optical scanning device according to 3. 15. The optical scanning device according to claim 13, wherein the sub-scanning direction control means is arranged between the light source unit and the optical deflector. 16. The optical scanning device according to claim 13, wherein a prism is used as the sub-scanning direction control means. 17. The optical scanning device according to claim 13, wherein a galvanomirror is used as said sub-scanning direction control means. 18. An image reading apparatus using the optical scanning device according to claim 1. 19. An image forming apparatus using the optical scanning device according to claim 1. 20. A plurality of image forming units which are held so as to form a cylinder and correspond to a plurality of colors including a developing device and a photoreceptor, and simultaneously rotate the plurality of image forming units around the axis of the cylinder. The image forming unit is moved between an image forming position and a standby position, and a transfer member is brought into contact with the photoreceptor of the image forming unit located at the image forming position. With the switching of the image forming unit located at the position, the toner images of each color formed on each photoconductor are sequentially transferred to the transfer body, and the toner images of each color are superimposed to form a color toner image on the transfer body. A color image forming apparatus including a transfer unit formed thereon and an optical scanning device that exposes the photoconductor,
18. A color image forming apparatus using the optical scanning device according to claim 1 as the optical scanning device.