JPH07168112A - Optical scanner - Google Patents

Abstract

PURPOSE:To correct the asymmetry of optical scanning and to obtain a highly accurate output image by turnably providing a scanning lens system within a surface where the main light beam of luminous flux generated in accordance with the optical scanning passes through and adjusting the optical scanning state of the surface to be scanned by turning the scanning lens system. CONSTITUTION:The luminous flux made incident on a deflecting and reflecting surface 5a is reflected and deflected, made incident on the scanning lens system 6 having an (f-theta) characteristic and condensed, thus to form a light spot on the surface 7a to be scanned of a photoreceptor drum 7. Besides, the optical scanning of the surface to be scanned 7a is executed in a direction shown by an arrow Q by rotating an optical deflector 5 in a direction shown by an arrow S with a rotary shaft P as an axis. When the assembling error or the parts error in a collimator lens 2, a cylindrical lens 3, a scanning lens 6, the optical deflector 5 or the like is caused, the asymmetry is caused at an optical scanning time and the formed image is deteriorated. In order to correct the asymmetry, the lens system 6 is turned without the main scanning cross section and adjusted so that the luminous flux from the lens system 6 is equally condensed on the surface 7a 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, and more particularly to forming an image by optically scanning a surface to be scanned, which is an image bearing member such as a photosensitive member or an electrostatic recording member, with a light beam modulated. The present invention also relates to an optical scanning device suitable for a device such as a laser beam printer, a color laser beam printer, or a multi-color laser beam printer having an electrophotographic process.

[0002]

2. Description of the Related Art FIG. 6 is a main scanning sectional view of a conventional optical scanning device. In the figure, reference numeral 61 denotes a laser unit having a light source such as a semiconductor laser and a collimator lens for collimating a light beam from the light source.

Reference numeral 62 is a cylindrical lens having a refractive power only in the sub-scanning direction, and 63 is the cylindrical lens 6.
It is an optical deflector (scanning mirror) that deflects the light flux from 2 and comprises a rotating polygon mirror or the like.

Reference numeral 64 is a spherical lens, and 65 is a toric lens. The spherical lens 64 and the toric lens 65 constitute one element of a scanning lens system 67 having an f-θ characteristic.

Reference numeral 66 denotes a photosensitive drum, which is a scanning lens system 6
The laser light flux from the laser beam 7 is guided on the surface (scanned surface) 66a of the photosensitive drum 66 to form a light spot.

In the figure, a laser unit 61 emits a light beam which is optically modulated based on a drive signal from a drive circuit (not shown). The laser light beam from the laser unit 61 is condensed by the cylindrical lens 62 only in the sub-scanning direction and is incident on the reflecting surface 63a of the scanning mirror 63.

Here, the scanning mirror 63 rotates in the direction of arrow 63b at a constant speed in the main scanning section,
The light beam incident on the reflecting surface is reflected and deflected, and is incident on the scanning lens 67 having the f-θ characteristic.

The light beam incident on the scanning lens 67 is condensed to form a light spot on the surface 66a to be scanned, and the surface is optically scanned with a substantially constant linear motion.

Further, the photosensitive drum 66 rotates about a rotary shaft 66b in synchronization with the drive signal, and relatively moves the irradiation position of the laser beam and the surface 66a to be scanned.

As a result, the laser beam two-dimensionally optically scans the surface 66a to be scanned, and an electrostatic latent image based on the drive signal is formed on the surface 66a to be scanned.

Then, an image is printed on the paper from the electrostatic latent image by using an electrophotographic process.

In such an optical scanning device, the focusing position of the laser light beam with respect to the rotation angle of the scanning mirror 63 during the optical scanning (hereinafter simply referred to as the focusing position of the laser light beam) due to an assembly error of each element or a component error. The surface to be scanned 66a may be misaligned and the formed image may be distorted.

That is, when the surface to be scanned 66a, which is the surface of the photosensitive drum 66, and the condensing position of the laser beam for optically scanning the surface to be scanned 66a are not parallel to each other due to an assembly error or a component error of each element. There is. For example, as shown by the dotted line in FIG. 7, the converging position 66a 'of the laser beam is on the scanned surface 66a.
When there is a tilt with respect to the laser beam that reaches the image center y ₀ on the surface to be scanned 66a when there is a displacement that intersects near the image center, the image is deflected to the left and right of the image at an equal angle, with reference to the laser beam. Position y of arrival of the laser beam on the surface to be scanned 66a
_- , Y ₊ have different distances from the image center y ₀ .

Therefore, if such a deviation becomes too large, the formed image becomes a distorted image which is asymmetric with respect to the center of the image.

In particular, in the case where a full-color image is formed by carrying out multi-color development, one pixel is 63.5 μ for one-hundredth of the number of pixels forming the image, for example, 400 dpi.
Even a misalignment of a fraction of m appears as a color misregistration or a change in tint, which significantly deteriorates the image quality.

Therefore, in the conventional optical scanning device, when performing multicolor development (in the case of full color, the optical scanning is performed three to four times), the same scanning lens system is used, that is, the optical scanning is performed with the same optical characteristics. However, the distortion of the superimposed images is made equal to alleviate the deterioration of the images.

[0017]

However, in the case of obtaining a color image, the means for repeating the optical scanning by the same optical scanning device is not a fundamental means for eliminating the distortion of the image, and a multiple image or a full-color image can be obtained. There was a problem that it took time to output. In particular, it is unsuitable for an optical scanning device that outputs a full-color image at high speed by using a method of recording an image on a single image carrier with a plurality of optical scanning beams or a method of recording an image on a single image carrier. There was a point.

According to the present invention, the scanning lens system is rotatably provided in the plane through which the principal ray of the light beam accompanying the optical scanning passes, and the scanning lens system is rotatably operated to adjust the optical scanning state on the surface to be scanned. Accordingly, it is an object of the present invention to provide an optical scanning device in which the asymmetry of optical scanning is corrected and a highly accurate output image can be obtained.

[0019]

The optical scanning device of the present invention comprises:
In an optical scanning device in which a light beam from a light source is deflected by an optical deflector and then is guided to a surface to be scanned through a scanning lens system to perform optical scanning, Is rotatably provided in a plane through which the principal ray of light passes, and the scanning state on the surface to be scanned is adjusted by rotating the scanning lens system.

Further, in the optical scanning device having a plurality of scanning units for deflecting the light beam from the light source by the optical deflector and then guiding the light beam onto the surface to be scanned through the scanning lens system to perform optical scanning,
The scanning lens system is rotatably provided in a plane through which the principal ray of the light flux passes along with optical scanning, and the scanning state on the surface to be scanned is adjusted by rotating the scanning lens system. There is.

In addition, in the optical scanning device of the present invention, a plurality of light beams emitted from a plurality of light sources are deflected by an optical deflector, and then guided to the surface to be scanned through different scanning lens systems to perform optical scanning. In the optical scanning device configured as described above, the scanning lens system is provided so as to be rotatable within a plane through which the principal ray of the light beam passes as the optical scanning is performed, and the scanning lens system is rotated to operate on the surface to be scanned. The feature is that the scanning state is adjusted.

[0022]

1 is a schematic view of a main part of a first embodiment of the present invention, FIG. 1 (A) is a cross-sectional view in the main scanning direction, and FIG. 1 (B) is A-A (of FIG. 1A). It is a sub-scanning direction) sectional drawing.

FIG. 2 is a perspective view of an essential part of the scanning lens system of FIG.
FIG. 3 is an explanatory diagram of an optical scanning state on the surface to be scanned,
The light beam shown by the solid line in the figure is the optical scanning state when the image is formed correctly, the light beam shown by the broken line is before the optical scanning state adjustment, and the light beam shown by the solid line is after the optical scanning state adjustment. It is in a state.

In the figure, 1 is a light source such as a semiconductor laser, and 2 is a collimator lens for collimating a light beam from the light source.

Reference numeral 3 denotes a cylindrical lens having a refracting power only in the sub-scanning direction, and reference numeral 5 denotes an optical deflector (scanning mirror) for deflecting the light beam from the cylindrical lens 3, which comprises a rotating polygon mirror or the like.

Reference numerals 6a and 6b are spherical lenses, and 6c is a toric lens. The spherical lenses 6a and 6b and the toric lens 6c constitute one element of the scanning lens system 6 having the f-θ characteristic.

Reference numeral 7 denotes a photosensitive drum, and a laser beam from the scanning lens system 6 is guided on the surface (scanned surface) 7a of the photosensitive drum 7 to form a light spot.

In this embodiment, the divergent light beam emitted from the light source unit 1 is collimated by the collimator lens 2 and is incident on the cylindrical lens 3 having a refractive power only in the sub-scanning direction.

The light beam is condensed by the cylindrical lens 3 only in the sub-scanning direction, and an optical deflector 5 composed of a rotating polygon mirror or the like is provided through a cover glass 4 for dust prevention.
It is incident on the deflective reflection surface 5a as a linear light beam.

The light beam incident on the deflecting / reflecting surface 5a is reflected and deflected and enters the scanning lens system 6 having the f-θ characteristic,
The surface to be scanned 7 of the photosensitive drum 7 is condensed by the scanning lens system 6.
Form a light spot on a.

Then, the optical deflector 5 is rotated by the arrow S about the rotation axis P.
By rotating in the direction of arrow Q on the surface 7a to be scanned.
Optical scanning in the direction.

The deflective reflection surface 5a of the optical deflector 5 and the surface 7a to be scanned are provided so as to be conjugate to the scanning lens system 6, and the deflection reflective surface 5a is precessed as the optical deflector 5 rotates. Even if a motion is caused, or even if there is a relative inclination with respect to the adjacent deflecting / reflecting surface due to the processing accuracy of the deflecting / reflecting surface 5a, optical scanning is performed on a fixed line on the optical scanning surface.

In these configurations, if there is an assembly error or a component error in the collimator lens 2, the cylindrical lens 3, the scanning lens 6, the optical deflector 5 and the like, asymmetry will occur during optical scanning, and they will be formed. The image deteriorates.

Therefore, in this embodiment, in order to correct this asymmetry, the scanning lens system 6 is rotated within the main scanning cross section so that the light beams from the scanning lens system 6 are equally focused on the surface 7a to be scanned. It is adjusted to shine.

Next, the adjustment of the optical scanning state will be specifically described with reference to FIG. In the figure, due to an assembly error, a production error, etc., the light-condensing position of the light beam to be optically scanned (hereinafter simply referred to as an image plane) has an inclination with respect to the scan surface 7a as indicated by a broken line 7a '. .

Here, when the rotation angle of the optical deflector that is reflected and deflected so as to be a designed on-axis light beam is 0, and the arrival position (that is, the image center) of the light beam deflected at the angle 0 is y _0. The light beam arrival positions when the light deflector 5 is rotated by the angles + θ and −θ are y ₊ and y ₋ , respectively. At this time reaching position y
_+, Y _- distance between the image center _{y 0 yl +, yl - (} y 0
= 0, yl ₊ is a positive value, and yl ₋ is a negative value), the deviation amount Δy is Δy = yl ₊ + yl ₋ ∴Δy ≠ 0.

From this shift amount Δy, the tilt direction of the image plane 7a 'and the tilt amount Δ can be obtained. Then, the correction angle Δθ is obtained based on the deviation amount Δy, the inclination direction of the image surface 7a ′ and the inclination amount Δ, and the scanning optical system 6 is inclined by the correction angle Δθ about the axis t as shown in FIG. Thus, the inclination of the image plane 7a 'can be corrected.

As a result, the distances yl ₊ and yl ₋ are set to the same value to prevent asymmetry.

In the present embodiment, the rotation axis of the scanning optical system 6 is shown as being rotated about the axis t, but the present invention is not limited to this, and it is applicable if it is rotated in the main scanning plane. The rotation shaft may be provided at another position depending on the displacement.

FIG. 4 is a schematic view of the essential portions of Embodiment 2 in which the present invention is applied to a full-color image forming apparatus.

In the figure, 101a, 101b, 101c, 1
Reference numeral 01d is a scanning unit having substantially the same configuration.

In the scanning units 101a to 101d, light sources 112a, 112b, 112 such as semiconductor lasers are provided.
The luminous fluxes emitted from c and 112d are formed by the imaging optical system 106a,
It is incident on 106b, 106c and 106d. Then, the optical deflectors 105a, 105b, 105, which are linearly condensed by the image forming optical systems 106a to 106d and are composed of a rotating polygon mirror or the like, are used.
It is incident on the deflecting and reflecting surfaces of c and 105d as a linear light beam.

The light beam incident on the deflecting / reflecting surface is reflected and deflected, and the scanning lens systems 103a and 103 having the f-θ characteristic.
It is incident on b, 103c and 103d. The scanning lens system 1
Reference numerals 03a to 103d denote optical deflectors 105a associated with optical scanning.
It is configured to be rotatable within a plane (hereinafter simply referred to as the main scanning plane in the present embodiment) through which the principal ray of the light flux from 105 d to 105 d passes.

The light beams incident on the scanning lens systems 103a to 103d are condensed and reflected by the mirror units 102a, 102b,
On the photosensitive drum (scanned surface) via 102c and 102d
A light spot is formed on each of 100a, 100b, 100c and 100d.

The surfaces to be scanned 100a to 100d are optically scanned by rotating the optical deflectors 105a to 105d. A conveying belt 104 conveys a recording material (not shown).

In this embodiment, each scanning unit 101a-10a is used.
1d forms latent images on the surfaces to be scanned 100a to 100d by using light fluxes based on the respective modulation signals. For example, latent images for yellow, magenta, cyan, black or red, green, blue and black are to be scanned surface 100a.
To 100d and then multiple-transferred to recording material
Forming a full-color image.

In each of these configurations, each optical scanning unit 1
The scanning lens systems 103a to 103d of 01a to 101d are respectively rotated in the main scanning plane, and each image plane is corrected in parallel with the surface to be scanned in the same manner as in the first embodiment. During multi-color development, pixels forming an image are superposed with high accuracy, thereby obtaining a high-quality full-color image with less color misregistration and tint change.

FIG. 5 is a schematic view of the essential portions of Embodiment 3 in which the present invention is applied to a full-color image forming apparatus. 212 in the figure
Reference numerals a, 212b, 212c, and 212d denote light source units such as semiconductor lasers, and the divergent light beams emitted from the light sources 212a to 212d are imaging optical systems 213a, 213b, and 213.
It is incident on c, 213d. The image forming optical systems 213a to 213
3d has a collimator lens, a cylindrical lens, etc., and makes the divergent light fluxes from the light sources 212a to 212d incident on the deflection reflection surfaces 202-1 and 202-4 of the light deflector 202 as linear light fluxes.

The light beams incident on the deflecting / reflecting surfaces 202-1 and 202-4 are reflected and deflected and enter the scanning lens systems 220a, 220b, 220c and 220d having the f-θ characteristic. The scanning lens systems 220a to 220d are composed of an anamorphic lens system, and the toric lens 205
a, 205b, 205c, 205d. Each of the scanning lens systems 220a to 220d is configured to be rotatable within a plane (hereinafter simply referred to as a main scanning plane in the present embodiment) through which the principal ray of the light beam from the optical deflector 202 passes along with the optical scanning.

The light beams incident on the scanning lens systems 220a to 220d are condensed and scanned surfaces 200a, 200 on the photosensitive drum.
Light spots are formed at 00b, 200c, and 200d, respectively.

Then, the optical deflector 202 is rotated by the motor 201 about the rotation axis P, so that the surface to be scanned 200a.
Optical scanning is performed on 200d.

In the present embodiment, the scanning lens systems 220a-22a
By adjusting the rotation of 0d in the main scanning plane, the asymmetry generated due to the eccentricity of the optical member and the variation of the incident angle to the optical deflector based on the mounting accuracy of the imaging optical systems 213a to 213d is corrected. , It is possible to superimpose pixels with high accuracy.

[0053]

According to the present invention, a scanning lens system is rotatably provided in a plane through which a principal ray of a light beam accompanying optical scanning passes, and the scanning lens system is rotatably operated to perform optical scanning on a surface to be scanned. By adjusting the state, it is possible to achieve an optical scanning device in which the asymmetry of optical scanning is corrected and a highly accurate output image is obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is a perspective view of a main part of the scanning lens system according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of an optical scanning state according to the first embodiment of the present invention.

FIG. 4 is a schematic view of the essential portions of Embodiment 2 of the present invention.

FIG. 5 is a schematic view of the essential portions of Embodiment 3 of the present invention.

FIG. 6 is a schematic view of a main part of a conventional optical scanning device.

FIG. 7 is an explanatory diagram of an optical scanning state of a conventional optical scanning device.

[Explanation of symbols]

1, 112a to 112d, 212a to 212d Light source 2 Collimator lens 3 Cylindrical lens 4 Cover glass 5, 105a to 105d, 202 Optical deflector 6, 103a to 103d, 220a to 220d Scanning lens system 7, 100a to 100d, 200a to 200d Scanned surface 106a-106d, 213a-213d Imaging optical system

Claims (3)

[Claims] 1. An optical scanning device in which a light beam from a light source is deflected by an optical deflector and then guided onto a surface to be scanned through a scanning lens system for optical scanning. An optical scanning device, wherein the optical scanning device is provided so as to be rotatable in a plane through which a principal ray of the light flux passes during scanning, and a scanning state on a surface to be scanned is adjusted by rotating the scanning lens system. 2. An optical scanning device having a plurality of scanning units for guiding a light beam from a light source by an optical deflector and then guiding the light beam onto a surface to be scanned through the scanning lens system to perform optical scanning. Is provided so as to be rotatable within a plane through which the principal ray of the light beam passes along with optical scanning, and the scanning state on the surface to be scanned is adjusted by rotating the scanning lens system. . 3. An optical scanning device in which a plurality of light beams emitted from a plurality of light sources are deflected by an optical deflector and then guided onto a surface to be scanned through different scanning lens systems to perform optical scanning. The scanning lens system is rotatably provided in a plane through which the principal ray of the light flux passes along with optical scanning, and the scanning state on the surface to be scanned is adjusted by rotating the scanning lens system. Optical scanning device.