RU2257601C2 - Optical scanning device (variants), device for forming an image (variants) and device for forming a colored image (variants) - Google Patents

Abstract

FIELD: optics.

SUBSTANCE: device has light radiation source, deflecting device and optical image generation circuit, including optical element for forming an image, position so that when aligned to direction of additional scanning main beam of deflected light beam passes portion excepting optical axis. In first variant optical element has surface with alternating grade of sagittal non-sphericity, which changes along direction of main scanning of said optical element. In range of effective scanning of surface value of displacement of position of falling light beam in direction of additional scanning is made the same. In second variant of scanning device optical element is made so that on surface for scanning position of images of two light beams, falling in a slanting manner on surface, perpendicular to rotation axis of said deflecting device, at angles γ and γ' (0≠γ<γ'), almost coinciding with each other.

EFFECT: broader functional capabilities, higher efficiency.

8 cl, 30 dwg

Description

FIELD OF THE INVENTION

The present invention relates to an optical scanning device and to an image forming apparatus using it. In this form, the present invention is intended, for example, for various devices, such as a laser printer, digital copy machine, multifunction printer, etc., in which when using the electrophotographic process, one light beam or a large number of light beams optically modulated and emitted by a source lights are deflected when reflected by a multifaceted mirror (deflecting means) and an optical scan of the surface to be carried out using a scanning optical system canning, as a result of which graphic information is recorded on it.

In another aspect, the present invention relates to an optical scanning device and to an image forming apparatus using it, in which the light beam is projected obliquely (when inclined incidence) onto a plane perpendicular to the axis of rotation of the deflecting means, and in which the curvature of the scanning lines formed on the surface scanning as a result of oblique incidence is corrected so that good images can always be obtained. In addition, the present invention is intended for color image forming apparatuses having one or more optical scanning devices and a large number of image bearing elements corresponding to colors.

Typically, in optical scanning devices used, for example, in laser printers, a light beam optically modulated in accordance with an image signal and emitted by a light source is periodically modulated by an optical deflecting device comprising, for example, a polyhedral mirror. Then, using a scanning optical system having an f-θ characteristic, the light beam is focused to create a spot on the surface of the photosensitive recording medium (photosensitive drum) and for optical scanning of this surface, whereby the image is recorded.

On Fig presents a schematic view of the main part of a known optical scanning device.

As can be seen in the figure, the diverging light beam emerging from the light source 91 is converted by the collimator lens 92 into an almost parallel light beam. Then, the light beam is limited by the aperture 93 and then enters the cylindrical lens 94 having a predetermined refractive power only in the direction of additional scanning. As for the almost parallel light beam incident on the cylindrical lens 94, the light beam leaves it within the plane of the main scan section. On the other hand, within the additional scanning plane, the light beam is assembled so that it forms an image, for example an almost linear image, on the deflecting surface (reflective surface) 95a of the deflecting means (light deflector) 95, which contains a multifaceted mirror.

A light beam deflected by the deflecting surface 95a of the deflecting means 95 is guided to the surface 98 of the photosensitive drum, which is the scanning surface, by means of a scanning optical system 96 having an f-θ characteristic. When the deflecting means 95 rotates in the direction of arrow A, the surface of the photosensitive drum 98 is optically scanned in the direction of arrow B, as a result of which graphic information is recorded on it.

In an optical scanning device, for example, as described above, in order to obtain high-precision recording of graphic information, it is necessary that the field curvature along the entire scanning surface be well corrected so that the distortion characteristic (f-θ characteristic) reflects the proportionality between the display angle (scanning angle), and image height (distance from the center of scanning) Y and that the spot diameter at the corresponding heights in the image plane (on the scanning surface) is the same. Concerning optical scanning devices or scanning optical systems, many solutions have been obtained to ensure such characteristics.

On the other hand, in the case when using a single optical deflecting device, a large number of light beams are scanned, in order to separate the light beams in the direction of additional scanning necessary to satisfy the requirement of the light beams after scanning into corresponding photosensitive elements corresponding to different colors, it is necessary that the incident light beams were projected with an inclination (with an inclined incidence) onto the plane perpendicular to the axis of rotation, I reject his means. If the light beam falls obliquely on the deflecting means, it causes a phenomenon called “curvature of the scan lines”, in which the scan line on the scan surface becomes curved.

In particular, in the case of color imaging devices in which a laser beam is projected from optical scanning devices onto four photosensitive elements (photosensitive drums) to form latent images on them in order to thereby form images from primary colors, Y (yellow), M (magenta), C (light blue and Bk (black), respectively, on the corresponding photosensitive image elements, consisting of four colors Y, M, C and Bk, formed on the corresponding photosensor elements should be superimposed on the transfer material, for example, on a sheet of paper, therefore, if the optical scanning devices corresponding to these photosensitive elements distort the scanning lines, this is manifested in the error in the shape of the scanning lines related to the four colors, which causes a color shift in the image obtained on the translated material.Therefore, the image quality is significantly deteriorated.

In an attempt to solve the problem of curving scan lines, several optical scanning devices have been proposed.

Japanese Patent Application Laid-open No. 7-191272 shows an optical scanning device in which a light beam is projected obliquely onto a plane perpendicular to the axis of rotation of the deflecting means. In this example, one of the scanning optical elements forming the scanning optical system contains an anamorphic lens having an aspherical shape in the plane of the cross section of the main scan, and the radius of curvature in the plane of the cross section of the secondary scan is set independently of the plane of the cross section of the main scan. In addition, the optical axis is eccentric in the direction of additional scanning with respect to the deflecting surface of the deflecting means, whereby a correction of the curvature of the scanning lines is obtained.

Japanese Patent Application Laid-open No. 9-184991 shows an example in which a plane-parallel plate used as a dust-proof glass plate is mounted obliquely, thereby correcting the curvature of the scanning lines.

The basis of these methods related to the correction of the curvature of the scanning lines is an eccentric arrangement of the optical element, for example, the displacement of the scanning optical element (optical element creating an image), such as an anamorphic lens included in the scanning optical system, in the direction of additional scanning; or the inclination of an optical element such as a glass plate that protects against dust, which does not have the function of imaging.

However, if such an optical element is located eccentrically on the light path, then although the curvature of the scan lines can be corrected, other optical characteristics can change. In addition, the magnitude of the eccentricity of the optical element affects the correction of the curvature of the scan lines only in relation to a specific light beam. In the case of a large number of light beams, it is difficult to simultaneously correct the curvature of the scanning lines. Therefore, it is necessary to use one optical element for each one light beam. In the case of using a large number of light beams, it is necessary to use a large number of optical elements corresponding to these light beams. Which leads to an increase in the number of constituent elements.

Japanese Patent Application Laid-open No. 9-90254 shows an example in which the sagittal line of a cylindrical lens follows a non-cylindrical surface so that the wavefront of the light beam passing through the cylindrical lens is delayed at the periphery in the direction of additional scanning with respect to the standard spherical surface.

The basis of this example is a structure configured to prevent degradation of the quality of the draft image in the case when the beam diameter is small in the direction of additional scanning, which arises due to the narrowing of the light beam at a distance from the Gaussian plane of the image, and the change in the beam diameter due to misalignment becomes big. The specified solution is not a structure designed to solve the problem of curving scan lines.

Japanese Patent Applications Laid-Open No. 2002-148542 and No. 2002-162587 discuss an example in which, when a large number of light beams are scanned using one deflecting device, the light beams are different in height with respect to the direction of the additional scan, and after that As light beams are projected onto a plane perpendicular to the axis of rotation of the optical deflecting device, they are separated from each other.

However, the use of a compartment based on the difference in the height of the light beams leads to an increase in the height (thickness) of the optical deflecting device or to the necessity of manufacturing various lenses corresponding to the light beams. In this case, the structure becomes very complex.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an optical scanning device and an imaging device using it, in which the light beam is projected obliquely (when inclined incidence) onto a plane perpendicular to the axis of rotation of the deflecting device, or in which the scanning optical system is eccentric with respect to direction of additional scanning, and on the basis of this, any arising curvature of the scanning lines can be significantly reduced.

Another objective of the present invention is to provide an optical scanning device with a simple structure and an imaging device using it, by which the curvature of the scanning lines can be stably maintained very small, without limitation due to the placement of an optical element such as a curved mirror.

A further object of the present invention is to provide a color image forming apparatus that comprises one or more optical scanning devices configured to stably maintain very small curvature of the scanning lines in order to ensure that a high-quality image is obtained continuously without color shift.

In accordance with a first aspect of the present invention, to solve at least one of the problems discussed above, an optical scanning device is provided comprising: a light source; a deflecting device for deflecting a light beam emerging from said light source; a scanning optical system for scanning a surface to be scanned with a light beam deflected by said deflecting device, wherein said scanning optical system includes a scanning optical element arranged such that, in relation to the direction of additional scanning, the main beam of the deflected light beam passes a section apart from the optical axis , wherein said scanning optical element has a surface with a varying degree of sagittal asphericity, in p Within the limits of which the degree of asphericity of the sagittal surface changes along the direction of the main scan of the specified scanning optical element, and in which along the entire surface to be scanned, the place in the direction of the additional scan onto which the deflected light beam falls is made even.

In one preferred form of this aspect of the present invention, the scanning optical system is configured such that, within the range of effective scanning on the surface to be scanned, the amount of the position shift in the direction of the additional scanning onto which the deflected light beam is incident is kept at no more than 10 μm.

The light beam emitted from the specified light source may fall on a plane perpendicular to the axis of rotation of the specified deflecting device, at a predetermined predetermined angle to it.

In the direction of additional scanning, the place on the surface to be scanned, on which the main beam of the deflected light beam falls, can be located closer to the optical axis of the specified scanning optical system compared to the place where the main beam passes through the surface of the specified scanning optical element, and this surface has the greatest optical power.

The scanning optical system may have one or more surfaces with a changing sagittal radius of curvature, within which the sagittal radius of curvature varies along the main scanning direction of the specified scanning optical system.

A scanning optical system may consist of one scanning optical element.

The scanning optical system may have optical power in the direction of the additional scan, which is equal to or almost equal to the optical power of the indicated surface with a varying degree of sagittal asphericity.

In the case when the optical power of the specified scanning optical system in the direction of the additional scan is ⌀ _so , and the optical power of the indicated surface with a varying degree of sagittal asphericity in the direction of the additional scan is ⌀ _si , the relation

The light source can emit two or more light beams, and within the cross-sectional plane of the additional scan, the main beam of at least one light beam can pass along the upper side relative to the optical axis of the specified scanning optical system, while the main beam of at least one another light beam can pass on the lower side relative to the optical axis of the specified scanning optical system.

The deflecting device can deflect a large number of light beams, while said scanning optical system can include a large number of scanning optical elements for imaging light beams deflected by said deflecting device on a large number of surfaces to be scanned, and these surfaces correspond to light beams, and said deflecting device can be used by a large number of scanning optical systems.

In the case when, within the cross-sectional plane of the main scan, the distance from the indicated deflecting device to the exit surface for light of the specified scanning optical element along the optical axis is P1, the distance from the exit surface for the light of the specified scanning optical element to the surface to be scanned is equal to P2 recalculated to air the distance from the specified deflecting device located outside the axis to the exit surface for the light of the specified scan the irradiating optical element is equal to M1, and the distance from the output surface for the light of the specified scanning optical element to the surface to be scanned is equal to M2, the following relation can be fulfilled:

According to a second aspect of the present invention, there is provided an image forming apparatus comprising: an optical scanning device described with reference to the first aspect; a photosensitive member located in place of the surface to be scanned mentioned above; a developing device for developing an electrostatic latent image formed on said photosensitive member by a light beam scanned by said optical scanning device to obtain a tinted image; a transfer device for transferring the developed tinted image onto the transfer material; a fixing device for fixing the transferred tinted image on the translated material.

According to a third aspect of the present invention, there is provided an image forming apparatus comprising: an optical scanning device described with reference to the first aspect; a printer controller for converting encoded data input from external equipment into an image signal and for supplying an image signal to said optical scanning device.

In accordance with a fourth aspect of the present invention, there is provided a color image forming apparatus comprising: at least one optical scanning device described with reference to the first aspect; a large number of image-bearing elements on which images of various colors should be formed.

In one preferred form of this aspect, the device further comprises a printer controller for converting a color signal input from external equipment into video data of various colors and for supplying video data to respective optical scanning devices.

наклонного падения соответственно, почти совпадают друг с другом.In accordance with a fifth aspect of the present invention, an optical scanning device is provided, comprising: a light source; a deflecting device for deflecting a light beam emerging from said light source; a scanning optical system for scanning a surface to be scanned with a light beam deflected by said deflecting device, wherein said scanning optical system includes a scanning optical element configured such that, on a surface to be scanned, and with respect to the direction of the additional scanning, the image creating site two light beams obliquely incident on a plane perpendicular to the axis of rotation of the specified deflecting device, under the pre by the well defined angles γ and γ '

inclined incidence, respectively, almost coincide with each other.

In one preferred form of this aspect of the invention, the scanning optical element has an optical property by which, within the range of effective scanning on the surface to be scanned, the amount of the position shift in the direction of the additional scanning onto which two light beams can be incident can be kept at a level no greater than than 10 microns.

The scanning optical element can be made so that in the case when the focal length of the specified scanning optical system in the direction of additional scanning is fs, the spherical aberration in the direction of additional scanning will be no more than 0.05 fs throughout the entire region where the angle of inclination of the light beam is not greater than γ.

The scanning optical element can be positioned so that, in relation to the direction of additional scanning, the main beam of the light beam deflected by the deflecting device will pass a section in addition to the optical axis, and the specified scanning optical element may have a surface with a varying degree of sagittal asphericity, within which the degree of asphericity the sagittal surface changes along the direction of the main scan of the specified scanning optical element.

The scanning optical element can be positioned so that, in relation to the direction of additional scanning, the main beam of the light beam deflected when reflected by the deflecting device will pass a section in addition to the optical axis, and the scanning optical element may have a diffraction section having the property of an aspherical surface in the direction of additional scanning .

The scanning optical element may have one or more surfaces with a changing sagittal radius of curvature, within which the sagittal radius of curvature changes along the main scanning direction of the specified scanning optical element.

A scanning optical system may consist of one scanning optical element.

The scanning optical system may have a refractive power in the direction of additional scanning, which is equal to or almost equal to the refractive power of the indicated surface with a varying degree of sagittal asphericity.

In the case when the optical power of the specified scanning optical system in the direction of the additional scan is ⌀ _so , and the optical power of the indicated surface with a varying degree of sagittal asphericity in the direction of the additional scan is ⌀ _si , the relation

The scanning optical element can be located so that in the direction of additional scanning, the main beam of the light beam deflected when reflected by the deflecting device will pass a section in addition to the optical axis, and in which, by curving a large number of surfaces of the specified scanning optical element, spherical aberration in the direction of the additional scanning can be corrected throughout the area where the angle of inclined incidence is not greater than γ.

A light source can emit two or more light beams, and within the cross-sectional plane of the additional scan, the main beam of at least one light beam can pass along the upper side relative to the optical axis of the specified scanning optical element, while the main beam of another light beam can pass through the lower side relative to the optical axis of the specified scanning optical element.

The deflecting device can deflect a large number of light beams, while said scanning optical system can include a large number of scanning optical elements for imaging light beams deflected by said deflecting device on a large number of surfaces to be scanned, and these surfaces correspond to light beams, and said deflecting device can be used by a large number of scanning optical systems.

For an angle γ of inclined incidence, the relation 0 ° <γ <10 ° can be fulfilled.

In the case when, within the cross-sectional plane of the main scan, the distance from the indicated deflecting device to the exit surface for light of the specified scanning optical element along the optical axis is P1, the distance from the exit surface for the light of the specified scanning optical element to the surface to be scanned is equal to P2 recalculated to air the distance from the specified deflecting device located outside the axis to the exit surface for the light of the specified scan the irradiating optical element is equal to M1, and the distance from the output surface for the light of the specified scanning optical element to the surface to be scanned is equal to M2, the following relation can be fulfilled:

According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising: an optical scanning device described with reference to the fifth aspect; a photosensitive member located in place of the surface to be scanned mentioned above; a developing device for developing an electrostatic latent image formed on said photosensitive member by a light beam scanned by said optical scanning device to obtain a tinted image; a transfer device for transferring a developed tinted image onto a transfer material; a fixing device for fixing the transferred tinted image on the translated material.

In accordance with a seventh aspect of the present invention, there is provided an image forming apparatus comprising: an optical scanning device described in relation to the fifth aspect; a printer controller for converting encoded data input from external equipment into an image signal and for supplying an image signal to said optical scanning device.

In accordance with an eighth aspect of the present invention, there is provided a color image forming apparatus comprising: at least one optical scanning device described in relation to the fifth aspect; a plurality of image-bearing elements, each located on a surface to be scanned by said optical scanning device, for supporting images of various colors to be formed on them.

In one preferred form of this aspect of the present invention, the device further comprises a printer controller for converting a color signal input from external equipment into video data of various colors and for supplying video data to respective optical scanning devices.

In accordance with a ninth aspect of the present invention, there is provided an optical scanning device comprising: a light source; deflecting device; an optical scanning means in which a large number of light beams from the specified light source is directed to the specified deflecting device and a plurality of light beams from the specified deflecting device is directed to the corresponding surfaces to be scanned by the specified optical scanning means, and in which the specified optical scanning means includes one a scanning optical element having an anamorphic surface, and wherein said scanning optical element and EET within the main-scan sectional plane of one surface of which is an aspherical surface.

In one preferred form of this aspect of the present invention, in the cross-sectional plane of a further scan, a plurality of light beams incident obliquely onto a deflecting surface of said deflecting device.

At least one surface of the indicated scanning optical element may be characterized by the property of an aspherical surface in relation to the direction of the additional scan.

A scanning optical element may function to direct a plurality of light beams from said deflecting device to surfaces to be scanned, respectively.

One aspherical surface in the plane of the cross section of the main scan of the specified scanning optical element may be a surface located on the side of the entrance for light.

The shape of the aspherical surface of one aspherical surface in the plane of the cross section of the main scan of the specified scanning optical element may not have an inflection point when the curvature changes.

The scanning optical element may be an element formed by plastic molding.

The light source may be a multi-beam laser.

In the case when the optical power of the specified scanning optical element in the direction of the additional scan is ⌀ _so , and the optical power of the output surface for the light of the specified scanning optical element in the direction of the additional scan is ⌀ _si , the relation

In the case where the distance from the specified deflecting device to the air surface converted to air for the light of the specified scanning optical element along the optical axis is P1, the distance from the output surface for the light of the specified scanning optical element to the surface to be scanned is equal to P2, the distance from the air the specified deflecting device located outside the axis to the output surface for the light of the specified optical element is equal to M1, and the distance from the output along surface for the light of the specified scanning optical element to the surface to be scanned is equal to M2, the following relation can be fulfilled:

Within the cross-sectional plane of the additional scan, the input surface for light of said scanning optical element may have a flat shape.

In accordance with a tenth aspect of the present invention, there is provided an image forming apparatus comprising: an optical scanning device described with reference to the ninth aspect; a photosensitive member located in place of the surface to be scanned mentioned above; a developing device for developing an electrostatic latent image formed on said photosensitive member by a light beam scanned by said optical scanning device to obtain a tinted image; a transfer device for transferring a developed tinted image onto a transfer material; a fixing device for fixing the transferred tinted image on the translated material.

According to an eleventh aspect of the present invention, there is provided an image forming apparatus comprising: an optical scanning device described with reference to the ninth aspect; a printer controller for converting encoded data input from external equipment into an image signal and for supplying an image signal to said optical scanning device.

In accordance with a twelfth aspect of the present invention, there is provided a color image forming apparatus comprising: at least one optical scanning device described in relation to the ninth aspect, in which this or each optical scanning device operates to record graphic information in relation to a respective one of the photosensitive elements corresponding to different colors respectively.

These and other objects, features and advantages of the present invention will become more apparent upon consideration of the following description of preferred embodiments of the present invention, made in conjunction with the accompanying drawings.

Brief Description of the Drawings

FIG. 1A is a cross-sectional view of a main scanning process according to a first embodiment of the present invention.

FIG. 1B is a cross-sectional view of an additional scanning process according to a first embodiment of the present invention.

Figure 2 presents a schematic view of the main part along the direction of additional scanning according to the first embodiment of the present invention.

Figure 3 presents a table of the degree of sagittal asphericity according to the first embodiment of the present invention.

4 is an illustration of a degree of sagittal asphericity according to a first embodiment of the present invention.

5 is an illustration of a degree of sagittal asphericity according to a first embodiment of the present invention.

6 is a schematic view for explaining in detail the surface according to the first embodiment of the present invention.

7 is a schematic view for explaining a change in the degree of sagittal asphericity of a surface according to a first embodiment of the present invention.

FIG. 8 is a schematic view for explaining changes in the degree of sagittal asphericity according to the first embodiment of the present invention.

9A and 9B are graphs for explaining aberrations according to a first embodiment of the present invention.

10A and 10B are graphs for explaining, respectively, an illuminated spot and curving scan lines according to a first embodiment of the present invention.

11 is a schematic view for explaining a shape of a meridional surface according to a first embodiment of the present invention.

On figa presents a schematic view of the main part along the direction of additional scanning according to the second variant implementation of the present invention.

On figv presents a schematic view of the main part along the direction of the additional scan according to the second variant implementation of the present invention.

13 is an illustration of a degree of sagittal asphericity according to a second embodiment of the present invention.

14 is an illustration of a degree of sagittal asphericity according to a second embodiment of the present invention.

15 is an illustration of a degree of sagittal asphericity according to a second embodiment of the present invention.

16A and 16B are graphs for explaining, respectively, an illuminated spot and curving scan lines according to a second embodiment of the present invention.

17A is a cross-sectional view of a main scanning process according to a third embodiment of the present invention.

FIG. 17B is a cross-sectional view of an additional scanning process according to a third embodiment of the present invention.

On Fig presents a schematic view of the main part of the image forming apparatus according to the present image.

19 is a schematic view of a main part of a color image forming apparatus according to the present invention.

On Fig presents a perspective image of a traditional optical scanning device.

21A and 21B are graphs for explaining spherical aberration according to a second embodiment of the present invention with respect to a comparative example.

22A and 22B are graphs for explaining aberrations according to a second embodiment of the present invention.

Description of Preferred Embodiments

Now, with reference to the accompanying drawings, preferred embodiments of the present invention will be described.

[First embodiment of the invention]

On figa in the direction of the main scan presents a sectional view (cross section of the main scan) of the main part of the optical scanning device according to the first embodiment of the present invention. FIG. 1B is a sectional view (cross-section of an additional scan) of the main part of the optical scanning device in the first embodiment.

As used herein, the term “main scan direction” refers to a direction perpendicular to the axis of rotation of the deflecting device and to the optical axis of the scanning optical element (that is, the direction in which the light beam is deflected when reflected (scanned when deflected) by the deflector. The term “additional scanning ”refers to a direction parallel to the axis of rotation of the deflecting device. The term“ cross-sectional plane of the main scan ”refers to a plane that contains t is the optical axis of the scanning optical system. The term “additional scan sectional plane” refers to a sectional plane perpendicular to the sectional plane of the main scan.

On figa and 1B, the number 1 denotes a semiconductor laser, which is used as a radiation source.

One or more diverging light beams of the semiconductor laser 1 is converted by a collimator lens 2 into parallel light beams or into almost parallel light beams, which may be converging beams or diverging beams. Following this, the diaphragm 3 limits the diameter of the beam to obtain the desired diameter of the spot. Number 4 denotes a cylindrical lens having a refractive power only in the direction of additional scanning. Its purpose is to form an image of the light incident on the deflecting surface 5a of the deflecting device 5 (described below), while the linear image is elongated in a direction parallel to the plane of the main scan section. Number 5 denotes the specified deflecting device, which contains a multifaceted mirror (rotating multifaceted mirror) having, for example, four faces (it can have more than four faces). The multifaceted mirror 5 rotates at a constant speed in the direction of arrow A.

Number 6 denotes a scanning optical system, which consists of a single scanning optical element (f-θ lens) having f-θ characteristic. Its function is to form an image of a light beam deflected when reflected by the deflecting device 5 on the surface of the photosensitive drum (photosensitive element) 8, which is a scanned surface. In addition, it is used to correct for the inclination of the deflecting surface 5a of the deflecting device 5. Hereinafter, the scanning optical system 6 will also be called the scanning optical element. More specifically, the light beam deflected when reflected by the deflecting surface 5a of the deflecting device 5 is directed through the scanning optical system 6 to the surface 8 of the photosensitive drum. When the multi-faceted mirror 5 is rotated in the direction of arrow A, the surface of the photosensitive drum 8 is optically scanned in the direction of arrow B. Thus, scanning lines are indicated on the surface of the photosensitive drum, as a result of which the image is recorded.

As shown in FIG. 1B, in the first embodiment, the light beam exiting from the light source 1 is projected onto the deflecting surface 5a obliquely from below at an angle γ with respect to the direction of the additional scanning, and light is incident on the scanning optical element 6, which is a single an element made of glass or synthetic polymer. The scanning optical element 6 is used to form an image of the deflected light beam in the form of a spot on the scanning surface 8.

Table 1 below shows the position of the optical surfaces of the optical elements in the first embodiment.

Table 1 Surface Arrangement Position Polyhedral deflecting surface 51.45 mm 0.00 mm Entrance surface of the f-θ lens 17.90 mm 51.45 mm The output surface of the f-θ lens 147.28 mm 69.35 mm Scanned surface 216.63 mm

Table 2 below shows the shapes of the input surface and output surface of the scanning optical element 6 in the first embodiment.

Figure 2 presents a cross-section of an additional scan, which shows the optical path for part of the elements of the optical system of the optical scanning device according to the first embodiment.

As shown in FIGS. 1B and 2, in the first embodiment, the light beam exiting from the light source 1 is projected onto the deflecting surface 5a obliquely from below at an angle γ with respect to the direction of additional scanning, and light is incident on the scanning optical element 6, which represents a single element made of glass or synthetic polymer. The scanning optical element 6 has an anamorphic surface and is used to form an image of the deflected light beam as a spot or essentially as a spot on the scanning surface 8.

FIG. 6 shows an embodiment of a scanning optical element 6 according to a first embodiment.

The shape of the meridional line of the input surface 6a for light and the output surface 6b for light of the scanning optical element 6 is determined by the aspherical shape of the surface, which can be expressed by a function up to the 10th order. For example, as shown in Fig.6, it is assumed that the intersection point of the scanning optical element 6 and the optical axis La is taken as the origin O1, the direction of the optical axis is used as the X axis, the axis perpendicular to the optical axis La, within the plane (plane XY) of the main scan section is used as the Y axis, and the direction perpendicular to the XY plane is used as the Z axis. In this case, the shape of the meridional line Xa in the meridional direction corresponding to the direction of the main scan (direction along the Y axis) can be expressed by the following equation:

where R is the radius of curvature of the meridional line, and k, B4, B6, B8, B10, B12, B14 and B16 are the asphericity coefficients.

In addition, the shape of the sagittal line S in the sagittal direction corresponding to the direction of the additional scan can be expressed by the following equation:

where S is the shape of the sagittal line defined within the plane that contains the normal to the meridional line for each position Y in the meridional direction and which is perpendicular to the plane of the main scan section (to the X-Y plane).

In this case, the radius of curvature (sagittal radius of curvature) Rs * in the scanning direction at a point Y that is Y from the optical axis and in the main scanning direction can be expressed by the following equation:

Rs * = Rs × (1 + D2 × Y ² + D4 × Y ⁴ + D6 × Y ⁶ + D8 × Y ⁸ + D10 × Y ¹⁰ ),

where Rs is the sagittal radius of curvature on the optical axis La, and D2, D4, D6, D8, and D10 are the sagittal increment indices. There is a surface for which the following value of X is added to equation (a) above as an aspherical component in the sagittal direction

X = (Cl + C2Y ² + C3Y ⁴ ) Z ⁴ .

Although in the first embodiment, the surface shape is determined by the equations mentioned above, the present invention is not limited to the use of the above equations, and any other equation that can describe aspherical components in the sagittal direction can be used.

In addition, in the first embodiment, each surface of the scanning optical element 6 does not create a shift or tilt in the direction of additional scanning. The location 5a1 from which the light beam directed to the end portion of the scanning surface 8 is deflected by the deflecting surface 5a of the polyhedral mirror 5 is at the same height as the optical axis La of the scanning optical element 6.

As shown in table 2, the input surface 6a of the scanning optical system 6 is a cylindrical surface having optical power only in the main scanning direction, while the shape of the meridional surface corresponds to the shape of the aspherical surface (not an arcuate shape), while the shape of the sagittal surface corresponds to the plane ( straight line). The output plane 6b of the scanning optical system 6 contains a surface with a varying sagittal radius of curvature, while the shape of the meridional line is arched, while the shape of the sagittal line is expressed so that along the meridional direction, the radius of curvature continuously varies with distance from the optical axis. In addition, the output surface is defined by a surface with a varying sagittal radius of curvature, while it has an arched shape on the optical axis, but has the shape of an aspherical surface (not an arched shape) on a part outside the optical axis, and the degree of asphericity varies along the meridional direction distance from the optical axis.

In addition, with regard to the shape of the aspherical surface of the scanning optical element 6 within the section plane of the main scan, it is determined by the shape that does not have an inflection point when the curvature changes.

Next, a schematic view of an optical scanning device according to a first embodiment shown in FIG. 2 will be explained with reference to the direction of additional scanning.

In the first embodiment, the light beam Li emerging from the light source 1 falls on the deflecting surface 5a of the deflecting device 5 in the direction of the additional scan at an angle γ = 3 ° with respect to the plane of the main scan section. In addition, the light beam Ld reflected by the deflecting surface 5a is incident on the scanning optical element 6 in the direction of additional scanning at an angle γ = 3 ° with respect to the plane of the main scan section. For this reason, the place from which the main beam (dash-dot line) of the deflected light beam Ld comes and passes the input surface 6a and output surface 6b is far from the sagittal optical axis (or meridional) La. The locations Za and Zb of the passage of the lens surfaces and the distance Z of the _lens from the optical axis La are located above the meridional line (Z _lens = 0) and therefore, this means that the Z _lens >> 0.

In the first embodiment, the distance Z of the _lens from the location Za in the direction of additional scanning, where the deflected light beam Ld falls on the input surface 6a of the scanning optical element 6, is equal to Z _lens = 2.73 mm, while the distance Z of the _lens from the place Zb where the light reaches the exit surface 6b, equal to Z _lens = 3.34 mm.

The deflected light beam Ld transmitted through the scanning optical element 6 is displayed as a spot on the scanning surface 8 due to the light-collecting property of the scanning optical element 6.

As described, when the main beam of the deflected light beam Ld passes a location located at a distance from the meridional (or sagittal) optical axis La, the light beam passing through the scanning optical element 6 is deflected down due to the optical power (refractive power) of the lens.

In this case, if the alignment of the scanning optical system 6 is not performed appropriately, the light crosses the optical axis La before it reaches the scanning surface 8, so that it falls on the scanning surface 8 to a location below the sectional plane of the main scan. The location in the secondary scan direction, where the deflected light beam Ld falls on the scanning surface 8, will be called “illuminated spot Zo”, while the distance from the optical axis La will be called “ _image Z”.

The incident location of the deflected light beam Ld in the direction of additional scanning on the input surface 6a and the output surface 6b of the scanning optical system 6, as well as its optical power (refractive power), affect the downward deflection of the deflected light beam Ld depending on the image height. As a result of this, the problem arises that the distance Z of the _{image of the} illuminated spot Zo ceases to be the same, resulting in an effect called “curvature of the scan lines”.

To solve this problem in the optical scanning device according to the first embodiment, the output surface 6b of the scanning optical element 6, which is the only element forming the scanning optical system, is provided with a surface with a varying degree of sagittal asphericity defined by the form S of the sagittal line in the above equation (b ) and numerical values in Fig.6. In this description, the term “surface with a varying degree of sagittal asphericity” refers to a surface for which along the meridional direction of the lens surface, the degree of sagittal asphericity Xz changes with distance from the optical axis La of the lens surface.

In this description, the term “degree of ΔXz of sagittal asphericity” refers to the degree of Xz indicated in FIG. 6, due to which at a certain point Z _lenses (Z _lens ≠ 0 mm) in the direction of additional scanning, excluding the meridional line (excluding the sagittal optical axis), the lens surface deviates from the base sagittal radius Rs * of curvature. The phrase “the degree ΔXz of sagittal asphericity changes” means that the degree ΔXz of sagittal asphericity at the same location of the Z _lens (Z _lens ≠ 0 mm) in the direction of additional scanning varies depending on the location along the Y axis in the meridional direction. That is, it means the state dΔXz / dY.

Figure 3 shows how the degree of sagittal asphericity Δ Xz of the output surface 6b of the scanning optical element 6 according to the first embodiment is changed. Figure 4 shows how the degree ΔXz of sagittal asphericity at a distance Z from the sagittal optical axis varies along the meridional direction (depending on the value of Y), i.e., the degree Xz of sagittal asphericity at ZRa in Fig. 7. FIG. 5 shows how the degree of sagittal asphericity ΔXz at a distance Y along the meridional direction from the optical axis La of the output surface 6b changes in the additional scanning direction (in the Z axis direction), that is, the sagittal asphericity degree ΔXz in the YRa location in FIG. .8.

In the first embodiment, the sagittal shape of the output surface 6b on the optical axis La is made arcuate, and on the part remote from the optical axis La in the meridional direction, the sagittal shape is not arched (aspherical). Moreover, as shown in FIG. 4, the exit surface 6b is defined as the indicated aspherical surface with a varying degree of sagittal asphericity, which in the meridional direction, the degree Δ Xz of sagittal asphericity gradually increases from zero with increasing distance from the optical axis La, and after passing the peak value it gradually decreases.

In addition, as shown in FIG. 5, the degree of sagittal asphericity is added so that on a portion of the exit surface 6b outside the optical axis La, it gradually increases with distance from the sagittal optical axis La in the direction of the additional scan. In this case, a positive sign means a deviation from the main arcuate shape towards the scan surface.

The surface with a varying degree of sagittal asphericity is such that, as the distance from the optical axis La on the exit surface 6b in the meridional direction, the degree of sagittal asphericity gradually decreases from zero, and on the part of the output surface 6b outside the optical axis La, the degree of sagittal asphericity gradually decreases with distance from the sagittal optical axis La in the direction of the additional scan.

In addition, the degree of sagittal asphericity is added in a very small amount, approximately 1/100 of the main arcuate shape, and the sagittal aspherical surface is effective only for correcting the curvature of the scan lines without making a significant contribution to the curvature of the field in the direction of additional scanning.

On figa and 9B depict aberrations in the first embodiment of the invention.

The curvature of the field in the direction of the main scan is within the range of ± 0.6 mm, and the curvature of the field in the direction of the secondary scan is within the range of ± 0.3 mm. Thus, they are well fixed. In addition, the distortion (f-θ characteristic) is within the range of ± 0.3%, and the shift in image height is within the range of ± 0.08 mm, and they are well adjusted.

Thus, apart from correcting the curvature of the field in the direction of additional scanning, based on the light-collecting property, which is ensured by the main arc-shaped shape, due to the asphericity effect, it is possible to control the illuminated location on the scanning surface. Due to the action of the aspherical surface, the illuminated Zoa location resulting from the deflected light directed to different points of the image in height can be made exactly aligned with the illuminated Zo location in the middle of the image height. That is, the curvature of the field in the direction of the additional scan and the curvature of the scan lines can be corrected independently of each other. More specifically with regard to alignment, it is carried out with the achievement of a positional shift in the direction of the additional scan, not exceeding 10 microns, preferably not exceeding 5 microns.

The position of the illuminated spot and the curvature of the scan lines in the optical scanning device according to the first embodiment are shown in FIGS. 10A and 10B in comparison with the position of the illuminated location and the curvature of the scan lines from the comparative example. The optical scanning device of the comparative example had a scanning optical system without an aspherical surface effect from the first embodiment. The curvature of the scan lines was determined by the shift in the position of the illuminated location between the middle of the image height and other image points in height.

As can be seen from FIGS. 10A and 10B, the illuminated location in the middle of the image height corresponding to the optical axis of the scanning optical system 6, both in the case of the first embodiment and in the comparative example, is at the _image distance Z = 0.1819 mm, and this the spot is above the sagittal optical axis.

In a comparative example, in comparison with the middle of the image height, the illuminated location at the end portion of the image height is shifted down, and a curvature of the scan line of 11 μm is created. Compared to this, in the first embodiment, the illuminated locations at different image heights are aligned, and the curvature of the scan line is corrected to a sufficiently small value of 5.0 μm.

From the foregoing, it can be seen that by varying the degree of Xz of sagittal asphericity with increasing distance from the optical axis La in the meridional direction, the position of the illuminated spot at each image height can be aligned, and the curvature of the scan line can be noticeably reduced.

Furthermore, since in the optical scanning device according to the first embodiment, the illuminated location Zo on the scanning surface 8 is closer to the sagittal optical axis La compared to the location Za or Zb in the secondary scanning direction when the deflected light beam Ld reaches the input surface 6a or the output surface 6b of the scanning optical system 6, then the curvature of the scanning line can be corrected more satisfactorily.

Next will be described a single scanning optical element 6, which forms a scanning optical system according to the first embodiment of the invention. The input surface 6a is a cylindrical surface having optical power only in the main scanning direction. The output surface 6b is a surface with a varying sagittal radius of curvature, while the meridional line has an arcuate shape, while the sagittal line is convex, and the absolute value of the radius of curvature gradually increases with distance from the optical axis in the meridional direction. In addition, on the left and right side of the main scan direction with the optical axis of the scanning optical system 6 lying in the middle, the sagittal radius of curvature changes asymmetrically. As described above, the total optical power (refractive power) of the scanning optical system 6 in the direction of additional scanning is concentrated on the output surface 6b.

More precisely, 90% or more of the total optical power is concentrated. That is, in the case where the optical power of the scanning optical system 6 in the direction of the additional scan is ⌀ _so , and the optical power of the surface with a varying degree of sagittal asphericity in the direction of the additional scan is ⌀ _si , the structure is such that the following relation holds:

11 is a schematic view of the main part of the first embodiment in the main scanning direction.

The meridional shape of the output surface 6b shown in FIG. 11 is arcuate and is shaped so that if the distance along the optical axis of the scanning optical system 6 is from a location in the main scanning direction, where the light beam is deflected using the deflecting surface 5a, to where the deflected light beam reaches the exit surface 6b is equal to P1, and the distance from the location where the deflected light beam reaches the exit surface 6b to the location where it hits the surface If 8 scans is equal to P2, then for the light paths of deflected light beams directed to all points of the image in height on the scanning surface 8, the ratio P2 / P1 becomes approximately constant (P2 / P1 = constant value) or, alternatively, it is within ± 10% of a certain value. For example, with regard to the case of the light path for the deflected light beam Ld directed to the end portion Ip of the image height, then if the distance from the location where the deflected light beam Ld is reflected by the deflecting surface 5a to the location where the deflected light beam Ld reaches the output surface 6b, is equal to M1, and the distance from the location where the deflected light beam Ld reaches the exit surface 6b to the location where it reaches the scanning surface 8 is equal to M2, the meridional shape is set such that M2 / M1 ratio is approximately equal to P2 / P1 (M2 / M1≈ P2 / P1, rather equality observed within ± 10%). That is, it is set so that the relation holds:

Although in the first embodiment, the total optical power (refractive power) of the scanning optical system 6 in the direction of additional scanning is concentrated on the output surface 6b, but nevertheless, as described above, it is possible to consistently create field curvature in the direction of additional scanning due to the meridional shape and obtain a transverse increase (increase with additional scanning) β s in the direction of additional scanning, even having an almost constant value. The increase during additional scanning by the scanning optical system 6 in the first embodiment is β s = -2.31x.

With this arrangement, even if the scanning optical element 6 is biased or tilted in the direction of the additional scan due to an error made during the production of an assembly error, for example, with the formation of an eccentricity in the direction of the additional scan, the calculated (initial) characteristics related to the curvature of the scan lines can be preserved .

Namely, according to the first embodiment of the optical scanning device, the curvature of the scanning lines can be satisfactorily corrected on the scanning surface 8 within the entire image height, and furthermore, even if there is any eccentricity of the scanning optical element 6 in the direction of the additional scanning, a very small curvature scan lines may remain unchanged. Therefore, in accordance with the first embodiment, an optical scanning device is proposed with which it is possible to stably correct the curvature of the scanning lines and constantly obtain high-quality images.

In the first embodiment, an example is considered in which the light beam emitted from the radiation source 1 is projected onto the deflector at an angle γ of inclined incidence with respect to the plane of the main scan section and in which the location is where the deflected light beam is directed toward the end of the surface 8 scan, deviates when reflected by the deflecting surface 5a of the polyhedral mirror 5, is at the same level as the optical axis of the scanning optical system 6. However, the invention This is not limited to this example. In an alternative example, the location where the light beam directed to all points of the image in height is deflected when reflected by the deflecting surface 5a may be above the optical axis. In this case, useful results of the present invention can still be obtained.

Furthermore, although the first embodiment relates to an optical scanning device in which a single light beam is optically scanned, the invention is not limited to this case. Essentially the same beneficial effects can be obtained in a multi-beam type optical scanning device in which two, three, four or more light beams are scanned simultaneously.

Further, although the first embodiment relates to an example in which a scanning optical system is constituted by a single scanning optical element, the invention is not limited to this case. A scanning optical system may comprise several optical devices, such as scanning optical elements or imaging mirrors. At least one surface of such scanning optical elements can be made in the form of a surface with a varying degree of sagittal asphericity, due to which it is possible to satisfactorily correct the curvature of the scanning lines.

It should be noted that in the first embodiment, the input surface and / or output surface of the scanning optical element can be formed together with diffraction means in order to obtain the same aspherical surface property described above.

[Second embodiment of the invention]

12A and 12B are schematic views along a sectional plane of an additional scan of an optical scanning device according to a second embodiment of the present invention.

The second embodiment differs from the first embodiment in that the degree of sagittal asphericity of the output surface 6b of the scanning optical element 6 is made variable.

Table 3 below shows the shapes of the inlet surface 6a and the outlet surface 6b of the scanning optical element 6 according to the second embodiment.

Next, a schematic view of an optical scanning device in the direction of additional scanning according to a second embodiment of the invention shown in FIG. 12A will be considered.

In a second embodiment of the invention, the light beam Li1 emitted from the radiation source 1 is incident on the deflecting surface 5a of the deflecting device 5 at an angle γ = 3 ° in the direction of the additional scan with respect to the plane of the cross-section of the main scan. In addition, the deflected light beam Ld1 reflected by the deflecting surface 5a falls on the scanning optical element 6 at an angle γ = 3 ° in the direction of the additional scan with respect to the plane of the cross section of the main scan. Therefore, the location where the main beam (dash-dot line) of the deflected light beam Ld1 arrives at the input surface 6a and output surface 6b, passes these surfaces, is at a great distance from the sagittal optical axis (or meridional) La. The locations Za and Zb of passage on the lens surfaces and the point Z of the _lens away from the optical axis La are above the position of the meridional line (Z _lens = 0) and, therefore, this means that the Z _lens >> 0.

In the second embodiment, the distance Z of the _lens from the location Za in the direction of additional scanning, where the deflected light beam Ld1 hits the input surface 6a of the scanning optical element 6, is Z _lens = 2.73 mm, while the distance Z of the _lens from the location Zb, where the light hits the exit surface 6b, equal to Z _lens = 3.34 mm.

In addition, with regard to the light beam Li2 incident obliquely at an angle γ = 1.5 °, the distance Z of the _lens from the location Zc in the direction of the additional scan, where the light beam falls on the input surface 6a of the scanning optical element 6, is equal to Z _lens = 1 , 36 mm, while the distance Z of the _lens from the location Zd, where light enters the exit surface 6d, is equal to Z of the _lens = 1.67 mm.

The deflected light beam Ld (Ld1 or Ld2) passing through the scanning optical element 6 forms a spot image on the scanning surface 8 due to the light-collecting property of the scanning optical element 6. In the second embodiment, both deflected light beams, Ld1 and Ld2, reach the surface 8 scanning, being within the plane of the cross section of the main scan (on the optical axis La of the scanning optical element 6). To ensure that light beams having different angles of inclined incidence, such as those described above, arrive at the same location (on the optical axis) on the scanning surface 8, the spherical aberration in the direction of the additional scanning should be well corrected within the region (shaded area in FIG. .12B) containing deflected light beams Ld1 and Ld2. This will be described in more detail below.

In this description, the location in the direction of the additional scan, where the deflected light beam Ld falls on the scanning surface 8, will be called “illuminated spot Zo”, while the distance from the optical axis La will be called “ _image Z”.

The location in the direction of the additional scan, where the deflected light beam Ld hits the input surface 6a and the output surface 6b of the scanning optical system 6, as well as the optical power (refractive power), which is crucial for deflecting the deflected light beam Ld down, depends on image heights. As a result, a problem arises in that the _image distance Z for the illuminated location Zo does not remain the same, resulting in the so-called “curvature of the scan lines”.

To solve this problem in the optical scanning device according to the second embodiment, the output surface 6b of the scanning optical element 6, which is the only optical element forming the scanning optical system, is provided with a surface with a varying degree of sagittal asphericity defined by the sagittal shape S in the above equation (b) and numerical values in FIG. Here, the term “surface with a varying degree of sagittal asphericity” refers to a surface for which along the meridional direction of the lens surface the degree of Δ Xz of the asphericity of the sagittal surface changes with distance from the optical surface La of the lens surface.

Here, the term “degree of ΔXz of sagittal asphericity” refers to the degree of ΔXz shown in FIG. 6, with the help of which in a certain place Z _lenses (Z _lens ≠ 0 mm) in the direction of additional scanning, except on the meridional (except on the sagittal optical axis), the lens surface deviates from the base sagittal radius of curvature Rs *. The term “sagittal asphericity degree ΔXz changes” means that the sagittal asphericity ΔXz degree at the same location of the Z _lens (Z _lens ≠ 0) in the secondary scanning direction varies depending on the Y coordinate in the meridional direction. That is, this means the state dΔXz / dY ≠ 0.

13 shows how the degree of sagittal asphericity ΔXz of the output surface 6b of the scanning optical element 6 according to the second embodiment is changed. On Fig shows how the degree ΔXz of sagittal asphericity at a distance Z from the sagittal optical axis changes along the meridional direction (values along the Y axis), that is, the degree ΔXz of sagittal asphericity at the location ZRa in Fig.7. FIG. 15 shows how the degree of sagittal asphericity ΔXz at a distance Y along the meridional direction from the optical axis La of the output surface 6b changes in the additional scanning direction (in the Z axis direction), that is, the degree of sagittal asphericity ΔXz at YRa in FIG. 8.

In a second embodiment, the sagittal shape of the exit surface 6b is not arched (aspherical). Moreover, as shown in FIG. 14, the exit surface 6b is defined as such a surface with a varying degree of sagittal asphericity such that in the meridional direction, the degree of asphericity of the sagittal surface gradually decreases with distance from the optical axis. In addition, as shown in FIG. 15, the degree of sagittal asphericity is added so that it gradually increases with distance from the sagittal optical axis in the direction of the additional scan. In this case, a positive sign means the transition from the main arcuate shape towards the scanning surface.

The surface with a varying degree of sagittal asphericity is such that, as the distance from the optical axis La on the exit surface 6b in the meridional direction, the degree of sagittal asphericity gradually decreases from zero, and on the part of the output surface 6b outside the optical axis La, the degree of sagittal asphericity gradually decreases with distance from the sagittal optical axis La in the direction of the additional scan.

In addition, the degree of sagittal asphericity is added in a very small amount, approximately 1/100 of the main arcuate shape, and the sagittal aspherical surface is effective only for correcting the curvature of the scan lines without making a significant contribution to the curvature of the field in the direction of additional scanning.

On figa and 21B shows the spherical aberration in the direction of additional scanning at the middle of the height of the expanded image and at the end of the height of the expanded image in accordance with the second embodiment. Although the real light beam is limited to the narrow region shown in FIG. 12A, the region shaded in FIG. 12B was used to evaluate the spherical aberration of the lens used in the second embodiment. As for the comparative example, it used a lens without an aspherical surface in the sagittal direction. The ordinate axis represents the position of the light beam in the direction of the additional scan passing through the input surface 6a of the scanning optical element 6. As shown in these graphs, in the entire region including the deflected light beams Ld1 and Ld2, the spherical aberration in the direction of the additional scan is satisfactorily corrected.

More precisely, when the focal length of the scanning optical system is fs, and the scanning optical element 6 is made so that the angle of incidence of the light beam is not greater than γ in the entire region, the spherical aberration in the direction of additional scanning is kept at no more than 0.05 fs.

In the case of spherical aberration corrected as described above, a light beam inclined incidently on the area where the spherical aberration is corrected can certainly be displayed on the optical axis of the scanning optical element 6. This provides the following two useful results.

Firstly, even if the angle of inclined incidence γ changes, for example, due to an error in the placement of the light source or the collimator lens, there can be no doubt that the light can be displayed in the same illuminated spot on the photosensitive drum and therefore the adjustment of the illuminated spot in the direction of the additional scan can be simplified. In addition, even if the inclined incidence angle γ fluctuates due to any vibration of the device, this does not lead to severe irregularity and, therefore, a stable image quality can be maintained.

A second advantage can be obtained by using a scanning optical element in various image forming devices. More precisely, if you place a mirror or similar optical part after the scanning optical element, then when you change the angle γ of the inclined incidence due to any spatial restrictions in the main node or in any part, you can use the same scanning optical element. In oblique incidence optical systems known from the prior art, the scanning optical element is eccentric to correct the curvature of the scanning lines. Although this setup provides the ability to correct the curvature of the scan lines in the case of an inclined incidence angle γ, it does not satisfy the requirements for a different inclined incidence angle γ '. Therefore, if the angle of inclined incidence is different, the scanning optical element must be redesigned in relation to such an angle.

In comparison, after correcting spherical aberration in the direction of additional scanning within the area that is actually intended to be used, as, for example, in the considered embodiment of the invention, it is possible to obtain a scanning optical element that meets the requirements for any inclined incidence angle in this area.

In addition, to correct spherical aberration, instead of the sagittal aspherical surface used in the second embodiment, the surface of a diffractive optical element having the property of an aspherical surface can be used. As a further alternative, spherical aberration can be corrected by bending multiple surfaces.

FIGS. 22A and 22B show aberrations according to a second embodiment of the invention (with an inclined incidence angle of 3 °).

The curvature of the field in the direction of the main scan is within ± 0.6 mm, and the curvature of the field in the direction of the secondary scan is within ± 0.3 mm. Therefore, they are well fixed. In addition, the distortion (f-θ -characteristic) is within ± 0.3%, and the shift in image height is within ± 0.08 mm, that is, they are well adjusted.

Thus, apart from correcting the field curvature in the direction of the additional scan based on the light-collecting property, which is due to the main arc-shaped shape, it is possible to control the position of the illuminated location on the scan surface using the asphericity effect. Due to the influence of the aspherical surface, the Zoa location illuminated by deflected light directed to various points along the image height can be brought into exact alignment with the illuminated Zo location in the middle of the image height. That is, the curvature of the field in the direction of the additional scan and the curvature of the scan lines can be corrected independently of each other. More specifically with respect to alignment, it is realized with a positional shift in the direction of additional scanning not exceeding 10 microns, preferably not exceeding 5 microns.

The position of the illuminated spot and the curvature of the scan line in the optical scanning device according to the second embodiment are shown in FIGS. 16A and 16B (for oblique incidence angles of 3 and 1.5 °) in comparison with the position of the illuminated spot and the curvature of the scan line according to the comparative example. An optical scanning device according to a comparative example has a scanning optical system without an aspherical surface effect according to a second embodiment of the invention. The curvature of the scan lines was determined by the shifts of the positions of the illuminated locations between the middle of the image height and other image points in height.

As can be seen from figa and 16B, for the illuminated location in the middle of the image height corresponding to the optical axis of the scanning optical system 6, the _image Z = 0 mm in the second embodiment, while the _image Z = -0.0997 mm in the comparative example without sagittal spherical surface.

In a comparative example, compared to the middle of the image height, the illuminated location at the end portion of the image height is shifted down, and a curvature of the scan line of 11 μm is created. In comparison with this, in the second embodiment, the illuminated spots at different image heights are aligned, and the curvature of the scan line is corrected to a sufficiently small value of 4.7 μm in the case of an inclined incidence angle of 3 °, and to 2.3 μm in the case of an inclined incidence angle of 1.5 °.

From the foregoing, it can be seen that by changing the degree of Δ Xz of sagittal asphericity with increasing distance from the optical axis La in the meridional direction, the position of the illuminated spot at each image height can be aligned, and the curvature of the scan lines can be significantly reduced.

Furthermore, since in the optical scanning device according to the second embodiment, the illuminated location Zo on the scanning surface 8 is closer to the sagittal optical axis La compared to the location in the secondary scanning direction, where the deflected light beam Ld reaches the input surface 6a or the output surface 6b of the scanning optical system 6, then the curvature of the scan lines can be corrected more satisfactorily.

Next, a single scanning optical element 6 that forms a scanning optical system according to a second embodiment of the invention will be described. The input surface 6a is a cylindrical surface having optical power only in the main scanning direction. The output surface 6b is a surface with a varying sagittal radius of curvature, while the meridional line has an arched shape, while the sagittal line is convex, and the absolute value of the radius of curvature gradually increases with distance from the optical axis in the meridional direction. In addition, on the left and right side of the main scan direction with the optical axis of the scanning optical system 6 lying in the middle, the sagittal radius of curvature changes asymmetrically. As described above, the total optical power (refractive power) of the scanning optical system 6 in the direction of additional scanning is concentrated on the output plane 6b.

More precisely, it is preferable that 90% or more of the total optical power is concentrated. That is, in the case where the optical power of the scanning optical system 6 in the direction of the additional scan is ⌀ _so , and the optical power of the surface with a varying degree of sagittal asphericity in the direction of the additional scan is ⌀ _si , the structure is such that the following relation holds:

11 is a schematic view of a main part according to a second embodiment of the invention in the main scanning direction.

The meridional shape of the exit surface 6b shown in FIG. 11 is arched and such that if the distance along the optical axis of the scanning optical system 6 is from a location in the main scanning direction where the light beam is deflected by the deflecting surface 5a to a location where the deflected light the beam reaches the exit surface 6b, equal to P1, and the distance from the location where the deflected light beam reaches the exit surface 6b, to the location where it falls on the surface 8 of the scan equal to P2, then for the light paths of deflected light beams directed to all points of the image in height on the scanning surface 8, the ratio P2 / P1 becomes almost constant (P2 / P1 = constant value) or, alternatively, it is within ± 10 % of a specific value. For example, with regard to the case of the light path for the deflected light beam Ld directed at the end portion Ip of the image height, then if the distance from the location where the deflected light beam Ld is reflected by the deflecting surface 5a, to the location where the deflected light beam Ld reaches the output surface 6b is equal to M1, and the distance from the location where the deflected light beam Ld reaches the exit surface 6b to the location where it reaches the scanning surface 8 is M2, the meridional shape is set so that the ratio M2 / M1 is approximately equal to P2 / P1 (M2 / M1≈ P2 / P1, more precisely, that the equality is observed within ± 10%). That is, the indicated meridional form is set so that the relation

Although in the second embodiment, the total optical power (refractive power) of the scanning optical system 6 in the direction of the additional scan is concentrated on the output surface 6b, it is possible to consistently form the field curvature in the direction of the additional scan using the meridional shape, as described above, and obtain a transverse increase ( increase with additional scanning) β s in the direction of the additional scanning, while even having an almost constant value. The increase in the direction of additional scanning of the scanning optical system 6 in the second embodiment is β s = -2.31x.

With this arrangement, even if the scanning optical element 6 is biased or tilted in the direction of the additional scan due to production error or assembly error, for example, with the formation of an eccentricity in the direction of the additional scan, the calculated (initial) characteristics related to the curvature of the scan lines can be preserved.

Namely, according to the second embodiment of the optical scanning device, the curvature of the scanning lines can be satisfactorily corrected on the scanning surface 8 within the entire height of the image, and in addition, even if there is any eccentricity of the scanning optical element 6 in the direction of the additional scanning, a very small curvature scan lines may remain unchanged. Therefore, in accordance with the second embodiment, an optical scanning device is proposed with which it is possible to stably correct the curvature of the scanning lines and constantly obtain high-quality images.

In a second embodiment, an example is considered in which the light beam emitted from the radiation source 1 is projected at an inclined incidence angle γ with respect to the plane of the main scan section and in which the location where the deflected light beam directed toward the end of the scanning surface 8 is deflected when reflected by the deflecting surface 5a of the polyhedral mirror 5, it is at the same level as the optical axis of the scanning optical system 6. However, the invention is not limited to this mer. In an alternative example, the location where the deflected light beam directed to all points of the image in height is deflected when reflected by the deflecting surface 5a may be above the optical axis. In this case, useful results of the present invention can still be obtained.

Furthermore, although the second embodiment relates to an optical scanning device in which one light beam is optically scanned, the invention is not limited to this. Essentially the same beneficial effects can be obtained in a multi-beam type optical scanning device in which two, three, four or more light beams are scanned simultaneously.

Further, although the second embodiment relates to an example in which the scanning optical system is formed by one scanning optical element, the invention is not limited to this solution. A scanning optical system may comprise several optical components, such as scanning optical elements or imaging mirrors. At least one surface of such scanning optical elements can be made in the form of a surface with a varying degree of sagittal asphericity, due to which it is possible to satisfactorily correct the curvature of the scanning lines.

It should be noted that in the second embodiment, the input surface and / or output surface of the scanning optical element can be formed together with the diffraction element to obtain a similar property of the aspherical surface described above.

In the second embodiment, an example of an optical scanning device with only one surface with a varying degree of sagittal asphericity is considered, in which only the output surface 6b of the scanning optical element 6 is formed as a surface with a varying degree of sagittal asphericity. However, the invention is not limited to this case. Essentially the same useful results as in the second embodiment can be obtained using an optical scanning device with several surfaces with a change in the degree of sagittal asphericity, in which the input surface 6a of the scanning optical system 6 is also made in the form of a surface with a varying degree of sagittal asphericity for the purpose of sharing the asphericity of two surfaces.

Further, although in the second embodiment, the meridional shape of the exit surface 6b of the scanning optical system 6 is arcuate, the invention is not limited to this case.

If you use a non-arched shape (aspherical shape), then you can well correct the aberrations in the direction of the main scan, and therefore, in this case, you can get essentially the same useful results or better results.

In addition, although in the second embodiment two coefficients, Z ⁴ and Z ⁴ Y ^{2 were used} to describe the sagittal aspherical surface, the invention is not limited to this case. To describe the sagittal aspherical surface, a polynomial can be used in which the number of orders for Y associated with Z ⁴ increases as Z ⁴ Y ⁴ , Z ⁴ Y ⁶ , Z ² Y ⁸ , etc. or a polynomial in which the number of orders for Z associated with each order Y, in addition to the above, increases as Z ⁶ , Z ⁶ Y ² , Z ⁶ Y ⁴ , Z ⁶ Y ⁶ , Z ⁶ Y ⁸ , etc. . and Z ⁸ , Z ⁸ Y ² , Z ⁸ Y ⁴ , Z ⁸ Y ⁶ , Z ⁸ Y ⁸ , etc. In this case, the beneficial effects of the present invention can be further enhanced.

[Third Embodiment]

On figa in the cross section of the main scan presents an optical scanning device according to the third variant of implementation, and on figv presents a view of the same device in cross section of an additional scan.

In the third embodiment, two optical scanning devices according to the first or second embodiment are included, but only one deflecting device is shared between the devices. More specifically, the third embodiment relates to an optical scanning device for use in a color image forming apparatus in which two light beams are introduced into each scanning optical system 6 and, therefore, four light beams are simultaneously projected onto one deflecting device 5, so that four light beams are deflected by one deflecting device 5 for optical scanning of photosensitive drums 8a-8d corresponding four light beams.

17A and 17B, the number 1 designates a radiation source (multi-beam laser), which includes four semiconductor lasers 1a, 1b, 1c and 1d, each configured to emit one light beam. Each of the four diverging light beams emitted from the four semiconductor lasers 1a-1d is converted by the corresponding one of the collimator lenses (first optical element) 2a, 2b, 2c and 2d into an almost parallel light beam (it can be a converging light beam or a diverging light beam ) Further, the aperture diaphragms 3a, 3b, 3c and 3d limit the width of the respective light beams. Of these light beams, two almost parallel light beams passing through the aperture diaphragms 3a and 3b form images using the first cylindrical lens (second optical element) having optical power only in the direction of the additional scan adjacent to the deflecting surface 5a of the deflecting device (to be described) for example, a linear image elongated along the plane of the cross section of the main scan. In addition, two almost parallel light beams passing through the aperture diaphragms 3c and 3d form images with a second cylindrical lens 4b having optical power only in the direction of additional scanning adjacent to the deflecting surface 5b of the deflecting device 5 (will be described), for example a linear image elongated along the section plane of the main scan.

Number 5 denotes a deflecting device, which is a multifaceted mirror (rotating multifaceted mirror), for example, made with four surfaces. Using a drive, such as a motor, it rotates at a constant speed in the direction of arrow A.

Number 61 designates the first scanning optical system, which consists of one scanning optical element (f-θ lens) made by plastic molding and having f-θ characteristic. Number 62 designates the second scanning optical system, which consists of one scanning optical element (f-θ lens) made by plastic molding and having f-θ characteristic. Each scanning optical element is used to image two deflected light beams BMa and BMb (BMc and BMd), respectively deflected by the deflecting device 5, on the surfaces 8a and 8b (8c and 8d) of the photosensitive drum that are being scanned. In addition, they are used to correct the inclination of the deflecting surface 5a (5b) of the deflecting device 5. In this case, four light beams BMA-BMd deflected by the deflecting surfaces 5a and 5b of the deflecting device 5 are guided through the first scanning optical system 61 or the second scanning an optical system 62 on four surfaces 8a, 8b, 8c, and 8d of the photosensitive drum (light blue, magenta, yellow, and black, respectively) corresponding to four light beams. When the deflecting device 5 is rotated in the direction of arrow A, the surfaces of the photosensitive drum 8a-8d are optically scanned in the direction of arrow B. Thus, one scan line is indicated on each of the four surfaces 8a-8d of the photosensitive drum, whereby an image is recorded.

Each scanning optical system 61 (62) uses a common scanning optical element for two light beams BMa and BMb (BMc and BMd), through which one scanning line is indicated on each of the four surfaces 8a-8d of the photosensitive drum and the image is recorded.

Hereinafter, for simplicity of consideration, the scanning optical systems 61 and 62 will also be referred to as the scanning optical system 6, and the collimator lenses 2a, 2b, 2c and 2d will also be referred to as the collimator lens 2. In addition, the aperture apertures 3a, 3b, 3c and 3d will also be be referred to as aperture diaphragm 3, and cylindrical lenses 4a and 4b will also be referred to as cylindrical lens 4. Scanning surfaces 8a, 8b, 8c and 8d will also be referred to as scanning surface 8.

A third embodiment relates to an example in which the invention is intended for use in a color image forming apparatus having four photosensitive drums, respectively light blue, magenta, yellow and black. A color image is formed by superimposing four colors, and if there is a spread in the print locations of the scan lines corresponding to these colors, the result is a mismatch in colors, which causes a deterioration in image quality. Therefore, it is necessary to ensure that the print locations of the scan lines that match the colors match.

A third embodiment relates to an optical scanning device for simultaneously scanning four light beams by using two scanning optical systems 61 and 62 optically coupled to one polyhedral mirror 5, as shown in FIG. 17B. More precisely, the deflected light beams VMA and VMC incident on the scanning optical systems 61 and 62, respectively, in the region above the sagittal optical axis, are returned back and down by the first and second return mirrors 7a and 7d, respectively, each of which is located near the scanning optical element 61 or 62, and then the light beams are reflected by the third and fourth return mirrors 7c and 7f, respectively, towards the surfaces 8a and 8c, respectively of the photosensitive drum. On the other hand, the deflected light beams BMb and BMd incident on the scanning optical elements 61 and 62 in the region below the sagittal optical axis are reflected towards the photosensitive surfaces 8b and 8d of the fifth and sixth return mirrors 7b and 7e, respectively, each of which located at a distance from the scanning optical element 61 or 62.

As shown, the return mirrors are approximately linearly symmetrical with respect to the axis of rotation of the polyhedral mirror and therefore the optical scanning device has a simple and compact design.

Typically, when the return mirrors are linearly symmetrical with respect to the axis of rotation of the multi-faceted mirror 5, as in the third embodiment, there is the possibility that the direction of curvature of the scan lines during optical scanning of the surfaces of the photosensitive drum is reversed and, if optical a scanning device that creates a large curvature of the scanning lines, the problem of color mismatch becomes very significant. Furthermore, if the arrangement of the return mirrors is changed relative to this embodiment, so that the deflected light incident on the second scanning optical system 62 at a location below the sagittal optical axis is directed to the surface of the photosensitive drum 8 by an even number of return mirrors, while the deflected a light beam incident above the sagittal optical axis is directed to the surface 8 of the photosensitive drum by an odd number of return x mirrors, the direction of curvature of the scan lines can be made the same. However, the light paths become very complex, and this leads to an increase in the volume of the optical scanning device or to an increase in the number of return mirrors, which makes the design very complicated.

In view of the specified in the third embodiment of the invention, the sagittal shape of the output surface 6b of each of the first and second scanning optical systems 61 and 62 is not arched (aspherical). In addition, a surface with a varying degree of sagittal asphericity is used, and the degree of sagittal asphericity changes as the output surface 6b moves away from the optical axis La along the meridional direction, whereby the curvature of the scanning lines decreases to a very small value. Using this arrangement, an optical scanning device of the third embodiment is obtained, by which even in the case of planning optical paths (or arranging return mirrors), in which the direction of curvature of the scanning lines is reversed, a color image can be stably formed without causing a color mismatch problem.

It should be noted that in the third embodiment of the invention, in order to obtain a similar property of the aspherical surface described above, the input surface and / or output surface of the scanning optical system can be formed in combination with a diffractive element.

Although in the third embodiment, the scanning optical system forms one scanning optical element, the invention is not limited to this solution. To achieve satisfactory useful results of the present invention, several optical elements can be used. It goes without saying that a scanning optical element having optical power only in the direction of additional scanning can be formed with a surface with a varying degree of sagittal asphericity.

In addition, in the third embodiment, one light beam is optically scanned along one of the surfaces of the photosensitive drum corresponding to different colors, but the invention is not limited to this case. For example, with a multifaceted mirror, eight light beams can be simultaneously deflected during reflection and, on the other hand, four light beams can be projected onto each of the two scanning optical systems, whereby two light beams can be directed onto each surface of the photosensitive drum to provide optical scanning. In the case of an optical scanning device of this design, substantially the same useful results of the present invention can be provided.

[Imaging Device]

On Fig in the direction of the additional scan presents a section of the main part of the image forming apparatus according to a variant implementation of the present invention. 18, the number 104 denotes an image forming apparatus. In this image forming apparatus 104, encoded Dc data is input from external equipment 117, for example, from a personal computer. The encoded data Dc is converted in the device by the printer controller 111 into video data (dot data) Di. Then, the video data Di is supplied to the optical scanning unit 100 having the structure described with reference to the first or second embodiments of the present invention. A light beam 103, modulated in accordance with the video data Di, is formed in the optical scanning unit 100, and the photosensitive surface of the photosensitive drum 101 is optically scanned in the direction of the main scan 103 with the light beam 103. The photosensitive drum 101, which is an electrostatic latent image carrier (photosensitive) element) rotates clockwise by the motor 115. With this rotation, the photosensitive surface of the drum 101 moves I relative to the light beam 103 in the direction of the additional scan, perpendicular to the direction of the main scan. Above the photosensitive drum 101 is located a charging roller 102 in contact with the surface of the drum, designed to uniformly charge the surface of the photosensitive drum 101. The light beam 103 scanned by the optical scanning unit 100 is projected onto the surface of the photosensitive drum 101, electrically charged by the charging roller 102.

As described above, the light beam 103 is modulated by the video data Di, and when illuminated with this light beam 103, an electrostatic latent image is formed on the surface of the photosensitive drum 101. The electrostatic latent image thus obtained is then developed to form a tinted image with a developing device 107, which is located lower in the direction of rotational movement of the photosensitive drum 101 relative to the location of illumination by the light beam 103 and is in contact with the photosensitive drum.

A tinting image developed by the developing device 107 is transferred onto a sheet of paper (transfer material) 112 by means of an image transfer roller 108, which is located below the photosensitive drum 101 and placed opposite the photosensitive drum. The paper sheets 112 are in the paper cassette 109 (on the right side of FIG. 18) in front of the photosensitive drum, but the paper sheets can be fed by hand. At the end of the sheet cassette 109, there are sheet feeding rollers 110 for guiding sheets 112 of paper located in the cassette 109 onto a path.

Then, a sheet of paper 112 having an unsecured tinted image deposited thereon is transmitted to the fixing device (on the left side of FIG. 18) located after the photosensitive drum 101. The fixing device includes a fixing roller 113 having a fixing heating element (not shown) and a pinch roller 114 arranged to form a pressure contact with the pin roller 113. The sheet of paper 112 moved from the image applying apparatus is heated by the pressure pin snovenii between the fixing roller 113 and pressing roller 114, whereby the unfixed tonirujushchim image on the sheet of paper 112 is fixed thereon. After the fixing roller 113, there are rollers 116 for outputting paper, and their function is to bring the sheet of paper 112 with the fixed image out from the image forming apparatus.

Although not shown in FIG. 18, not only the data conversion function described above is entrusted to the printer controller 111, but also a node control function, for example, an engine 115 inside the image forming apparatus and a multi-faceted mirror engine inside the optical scanning device, which will be described below.

[Color Imaging Device]

FIG. 19 is a schematic view of a main part of a color image forming apparatus according to an embodiment of the present invention. This embodiment relates to a tandem-type color image forming apparatus in which four optical scanning devices are arranged parallel to each other to record graphic information on photosensitive drums (image-bearing elements). In Fig. 19, the number 60 indicates a color image forming apparatus. Numbers 11, 12, 13, and 14 denote optical scanning devices having the structure as described with reference to the first or second embodiment of the present invention. Numbers 21, 22, 23 and 24 indicate photosensitive drums or image-bearing elements, and developing numbers are indicated by numbers 31, 32, 33 and 34. Number 51 indicates a conveyor belt.

19, color input signals 60, R (red), G (green), and B (blue), are received from external equipment 52, for example, from a personal computer or similar device. These color signals in the color image forming apparatus are converted by the printer controller 53 into video data (dot data) corresponding to C (light blue), M (magenta), Y (yellow), and B (black) colors. Then this video data is supplied to the optical scanning devices 11, 12, 13 and 14, respectively. After that, light beams 41, 42, 43 and 44 are formed in the optical scanning devices, modulated by the corresponding video data, as a result of which the photosensitive drums 21, 22, 23 and 24 are optically scanned by these light beams in the main scanning direction.

The color image forming apparatus of the indicated embodiment has four optical scanning devices 11-14 for parallel recording of image signals (graphic information) on the surface of the photosensitive drums 21, 22, 23 and 24 in accordance with four colors, C (light blue), M (magenta), Y (yellow), and B (black). Therefore, a color image can be printed at high speed.

As described above, the color image forming apparatus according to this embodiment of the invention includes four optical scanning devices 11-14 for generating latent images of corresponding colors on the surfaces of the respective photosensitive drums 21-24 by using light beams that are based on the corresponding video data. After that, these images are superimposed onto the recording material, resulting in a single multi-color image.

As for the external equipment 52, it is possible to use, for example, a color image reader having a sensing element based on a charge-coupled device. In this case, the color image reader and the color image forming apparatus in combination form a digital color copy machine.

According to the embodiments of the invention described above, at least one surface of the scanning optical element constituting the scanning optical system is formed as a surface with a varying degree of sagittal asphericity, with the degree of sagittal asphericity changing in the meridional direction. This ensures that the characteristics of the optical scanning device and the image forming device coincide, as a result of which the curvature of the scanning lines can be significantly reduced.

In addition, when the color image forming apparatus comprises a plurality of optical scanning devices described above, due to improved light path planning or changing the location of the return mirrors, it is possible to obtain a color image forming device with a reduced number of return mirrors or with a simpler and more compact design.

The present invention implements an optical scanning device or an imaging device using it, the structure of which is described above, while in the scanning optical system, the light incident obliquely on a plane perpendicular to the axis of rotation of the deflecting device, and by correcting spherical aberration in the direction of additional scanning in within a certain area in the direction of additional scanning, light can certainly be displayed on the optical axis of the scanning opt element, regardless of the angle of inclined incidence, since it is in the area of corrected spherical aberration; by correcting spherical aberration in the secondary scanning direction within the effective scanning range in the main scanning direction, the curvature of the scanning lines can be reduced.

In addition, the present invention implements an optical scanning device with a simple structure and an imaging device using it, whereby the optical scanning element is interchangeable in various forming devices of the invention.

The present invention provides an optical scanning device with a simple structure and an image forming device using it, in which the scanning optical system is provided with one scanning optical element having an anamorphic surface, and in which one surface of the scanning optical element is provided with an aspherical surface in the plane of the cross section of the main scan, as a result, the curvature of the scan lines can be reduced.

Although the invention has been described with reference to the structures disclosed in this application, it is not limited to the details set forth, and it is intended that this application covers modifications or changes that may be made with a view to improvements, or are within the scope of the following claims.

Claims (33)

1. An optical scanning device comprising a light emitting source; a deflecting device for deflecting a light beam emitted from said radiation source; an optical imaging system for scanning a surface to be scanned by a light beam deflected by said deflecting device, wherein said optical imaging system includes an optical imaging element arranged such that, as applied to the direction of additional scanning, the main beam of the deflected light beam passes a portion in addition to the optical axis in which said optical imaging element has a surface varying degrees of sagittal asphericity, within which the degree of asphericity sagittal surface changes along the main scanning direction of said optical member of the imaging and over the entire surface in the range of the effective scanning the offset location on which falls the deflected light beam in the sub-scan performed evenly. 2. The device according to claim 1, in which the specified optical imaging system is configured so that within the effective scanning range on the surface to be scanned, the magnitude of the location shift in the direction of the additional scan, onto which the deflected light beam is incident, is maintained at a level no greater than 10 microns. 3. The device according to claim 1, in which the light beam emitted from the specified radiation source of light falls on a plane perpendicular to the axis of rotation of the specified deflecting device, at a predetermined angle to it. 4. The device according to claim 1, in which in the direction of additional scanning, the location on the surface to be scanned, on which the main beam of the deflected light beam falls, is located closer to the optical axis of the specified optical imaging system compared to the location where the main beam passes through the surface of the specified optical image forming element and this surface has the greatest optical power. 5. The device according to claim 1, wherein said optical imaging system has one or more surfaces with a changing sagittal radius of curvature, within which the sagittal radius of curvature changes along the main scan direction of the specified optical imaging system. 6. The device according to claim 1, wherein said optical image forming system consists of one optical image forming element. 7. The device according to claim 1, in which the specified optical imaging system has optical power in the direction of additional scanning, which is equal to or almost equal to the optical power of the specified surface with a varying degree of sagittal asphericity. 8. The device according to claim 7, in which in the case when the optical power of the indicated optical imaging system in the direction of additional scanning is а _so , and the optical power of the indicated surface with a varying degree of sagittal asphericity in the direction of additional scanning is ⌀ _si , and the relation

9. The device according to claim 1, in which the specified radiation source of light emits two or more light beams and in which within the plane of the cross-section of the additional scan, the main beam of at least one light beam passes along the upper side relative to the optical axis of the specified optical formation system image, while the main beam of at least one other light beam passes along the lower side relative to the optical axis of the specified optical imaging system. 10. The device according to one of claims 1 to 8, in which said light source additionally emits two or more light beams, wherein said deflecting device deflects said two or more light beams to a surface to be scanned. 11. The device according to claim 1, in which, when within the plane of the cross section of the main scan, the distance from the specified deflecting device to the output surface for radiation from the specified optical imaging element along the optical axis is equal to P1, the distance from the output surface for radiation of said optical imaging element to the surface to be scanned is equal to P2, the distance calculated from the said deflecting device to the air to the place Assumption situated outside the exit surface for the radiation axis of said imaging optical element is equal to M1, and the distance from the radiation exit surface of said optical element to the surface to be scanned is equal to M2, the following relation holds:

12. An image forming apparatus comprising an optical scanning device according to claim 1, a photosensitive element located at a location of a surface to be scanned mentioned above, a developing device for developing an electrostatic latent image formed on said photosensitive element by a light beam scanned by said optical scanning device , to obtain a tinted image, a transfer device designed to transfer the developed tinting th image on a transfer material, a fixing device for fixing the transferred toner image on the transfer material. 13. An image forming apparatus comprising an optical scanning device according to claim 1, a printer controller for converting encoded data input from external equipment into an image signal and for supplying an image signal to said optical scanning device. 14. A color image forming apparatus, comprising at least one optical scanning device according to claim 1, a plurality of image-bearing elements on which images of various colors are to be formed. 15. The device according to 14, further comprising a printer controller for converting a color signal input from external equipment into video data of various colors and for supplying video data to respective optical scanning devices. 16. An optical scanning device comprising a light emitting source, a deflecting device for deflecting a light beam emitted from said light emitting source, an optical imaging system for scanning a surface to be scanned with a light beam deflected by said deflecting device in which said optical forming system image includes an optical image forming element, configured so that on the surface to be scanned, with respect to the direction of sub-scan imaging locations of two light beams obliquely incident on a plane perpendicular to the rotational axis of said deflecting device at certain angles γ and γ '(0

γ <γ ') of inclined incidence, respectively, almost coincide with each other. 17. The device according to clause 16, in which the specified optical image forming element has an optical property with which, within the range of effective scanning on the surface to be scanned, the magnitude of the location shift in the direction of the additional scan, into which two light beams fall, can be stored at no more than 10 microns. 18. The device according to clause 16, in which the optical imaging element is made so that in the case when the focal length of the specified optical imaging system in the direction of the additional scan is fs, the spherical aberration in the direction of the additional scan is not more than 0.05fs throughout areas where the angle of inclination of the light beam is not greater than γ. 19. The device according to clause 16, in which the specified optical image forming element is located so that in relation to the direction of additional scanning, the main beam of the light beam rejected by the deflecting device passes a section in addition to the optical axis and said optical image forming element has a surface with a varying degree sagittal asphericity, within which the degree of asphericity of the sagittal surface changes along the direction of the main scan of the indicated The imaging optical element. 20. The device according to clause 16, in which the specified optical image forming element is located so that in relation to the direction of additional scanning, the main beam of the light beam deflected when reflected by the deflecting device passes a section in addition to the optical axis and said optical image forming element has a diffraction section having the property of an aspherical surface in the direction of additional scanning. 21. The device according to clause 16, in which the specified optical image forming element has one or more surfaces with a changing sagittal radius of curvature, within which the sagittal radius of curvature varies along the main scan direction of the specified optical image forming element. 22. The device according to clause 16, in which the specified optical imaging system consists of a single optical image forming element. 23. The device according to claim 19, in which the specified optical imaging system has a refractive power in the direction of additional scanning, which is equal to or almost equal to the refractive power of the specified surface with a varying degree of sagittal asphericity. 24. The device according to item 23, in which when the optical power of the specified optical imaging system in the direction of additional scanning is ⌀ _so , and the optical power of the specified surface with a varying degree of sagittal asphericity in the direction of additional scanning is ⌀ _si , and the relation

25. The device according to clause 16, in which the specified optical image forming element is located so that in the direction of additional scanning, the main beam of the light beam deflected when reflected by the deflecting device passes a section in addition to the optical axis and by curving a large number of surfaces of the specified optical element imaging spherical aberration in the direction of additional scanning is adjusted throughout the area where the angle of inclined incidence is not longer than γ. 26. The device according to clause 16, in which the specified light source emits two or more light beams and in which, within the cross-sectional plane of the additional scan, the main beam of at least one light beam passes along the upper side relative to the optical axis of the specified optical forming element image, while the main beam of another light beam passes along the lower side relative to the optical axis of the specified optical image forming element. 27. The device according to clause 16, in which the specified radiation source of light additionally emits two or more light beams, while the specified deflecting device deflects these two or more light beams to the surface to be scanned. 28. The device according to clause 16, in which for the angle γ of inclined incidence the relation 0 ° <γ <10 ° is satisfied. 29. The device according to clause 16, in which, when within the cross-sectional plane of the main scan recalculated to air the distance from the specified deflecting device to the output surface for light of the specified optical image forming element along the optical axis is P1, the distance from the output surface for light of said optical imaging element to the surface to be scanned is P2, the distance calculated from the said deflecting device to the air to the location I, which is outside the axis of the output surface for light of the specified optical image forming element is M1, and the distance from the output surface for light of the specified optical image forming element to the surface to be scanned is M2, the following relation holds:

30. An image forming apparatus comprising an optical scanning device according to claim 15, a photosensitive member located at a location of a surface to be scanned mentioned above, a developing device for developing an electrostatic latent image formed on said photosensitive member by a light beam scanned by said optical scanning device , to obtain a tinted image, a transfer device designed to transfer the developed tinted image on the translated material, and a fixing device for fixing the transferred tinted image on the translated material. 31. The image forming apparatus containing the optical scanning device according to clause 16 and a printer controller for converting encoded data input from external equipment into a signal characterizing the image, and for supplying a signal characterizing the image to the specified optical scanning device. 32. A color image forming apparatus comprising at least one optical scanning device according to clause 16 and a plurality of image bearing elements, each element being located at a surface location to be scanned by said optical scanning device for supporting images of various colors to be formed on them. 33. The device according to p, which further comprises a printer controller for converting a color signal input from external equipment into video data of various colors and for supplying video data to respective optical scanning devices.

Images