JPH0727126B2 - Optical scanning device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device for scanning with a light beam, and more particularly to a suitable optical scanning device used in a laser beam printer or the like.

[Conventional technology]

In an optical scanning device using a light beam, when a deflecting device for deflecting the light beam, such as a rotating polygon mirror, whose deflecting surface can be tilted with respect to a rotation axis is used, the tilting of the deflecting surface (generally called surface tilting) causes light The beam may deviate in a direction perpendicular to the scanning direction, resulting in uneven pitch in the scanning line. Hereinafter, the scanning direction of the light beam is referred to as a main scanning direction, and the direction perpendicular to the scanning direction of the light beam is referred to as a sub scanning direction.

In order to correct such surface tilt, in the plane in the sub-scanning direction, the deflection surface and the surface to be scanned (image surface) have a conjugate relationship (the relationship between the object and the image, that is, the light beam is focused on the deflection surface). If
It is well known, for example, from Japanese Examined Patent Publication No. 52-28666, to use an image forming optical system having characteristics such that the light beam is always focused on the surface to be scanned.

Further, in addition to the above-mentioned image forming optical system, a characteristic for correcting distortion so that a light beam scans the surface to be scanned at a constant speed in a plane in the main scanning direction, and a characteristic on the surface to be scanned. It is required to have a characteristic for correcting the curvature of the image surface so that the size of the spot diameter of the light beam can be uniform regardless of the position on the scanning line.

As described above, the imaging optical system has various characteristics in the main scanning direction (characteristics for correcting distortion and characteristics for correcting field curvature) and characteristics in the sub-scanning direction (correction for surface tilt). In order to have the characteristics), an optical system having different powers in both directions is required, and conventionally, a cylindrical lens and a lens having a toric surface were used in combination.

By the way, in order to make the entire device of the optical scanning device compact, it is desirable to reduce the number of lenses of the above-mentioned imaging optical system and increase the deflection angle of the light beam in the polarization device. As an imaging optical system with a reduced number of lenses, one formed by two cylindrical lenses whose generatrices are orthogonal to each other (Japanese Patent Laid-Open No. 55-15131) or one formed by a spherical lens and a long cylindrical lens (Japanese Patent Laid-open Publication No. JP-A-58-93021) is known.

[Problems to be solved by the invention]

Although the conventional optical scanning device as described above has a simple configuration,
The deflection angle was relatively small, ± 20 to ± 25 °.

Therefore, when an attempt is made to enlarge the deflection angle in order to downsize the device, the conventional configuration as described above has the following problems.

For example, when a cylindrical lens having a power in the sub-scanning direction is used to correct surface tilt, if the deflection angle is increased, the image plane in the sub-scanning direction will be curved at the end of scanning, and this will be an unacceptable amount. Become.

Also in the characteristics in the main scanning direction, for example, when a spherical single lens is used to correct distortion (nonuniformity of scanning speed) and field curvature in the main scanning direction, the deflection angle is increased. However, there is a problem in that high-order aberrations occur, normal correction cannot be performed, and good performance cannot be obtained.

Furthermore, in the conventional optical scanning device as described above, the spot diameter at the focal point of the light beam, that is, the spot diameter on the surface to be scanned (image surface), has a design value within the range of 30 to 100 μm. However, once it is set to a certain value, it is difficult to change it to another value. Moreover, the spot diameter has a one-to-one relationship with the print density, and therefore,
The optical scanning device set to a certain spot diameter can be mounted only on a laser printer designed to have a printing density corresponding to the spot diameter. If, for example, an optical scanning device set to the same spot diameter is used, a laser printer designed so that the print density has a certain value x and a laser printer designed to have a different value y If they are mounted on the printer and the printer, respectively, the laser printers are designed to have different printing densities, but the spot diameters of the mounted optical scanning devices are the same. As a result of printing, both resolutions are the same.

The object of the present invention is to solve the above-mentioned problems of the prior art,
Even if the deflection angle is enlarged, it is possible to correct the field curvature in the main scanning direction and the sub-scanning direction and the distortion aberration within an allowable range.
Moreover, an object of the present invention is to provide an optical scanning device capable of arbitrarily changing the spot diameter of the light beam on the surface to be scanned.

[Means for solving problems]

In order to achieve the above-mentioned object, in the present invention, a light beam generation means for generating a light beam, a deflection means for reflecting the generated light beam by a deflection surface to deflect the light beam, and a surface to be scanned. An image forming optical system having an f.theta. Characteristic for forming an image of the light beam deflected by the deflecting means on the surface to be scanned, and the object to be scanned by the light beam deflected by the deflecting means. In the optical scanning device for scanning on a surface, the imaging optical system includes a spherical single lens, and a cross section along the scanning direction of the light beam has an arc shape with a relatively large radius of curvature and is perpendicular to the scanning direction. The cross section along the vertical direction has an arc shape with a relatively small radius of curvature, and the radius of curvature of the arc with a relatively small radius of curvature gradually decreases from the center position to both ends in the scanning direction. And a reflecting mirror having a reflecting surface forming a toric surface such as a barrel-shaped surface as a whole, and the spherical single lens is configured such that the light beam deflected by the deflecting means passes through the reflecting mirror. When it forms an image by converging on the surface to be scanned, it has a function of correcting the field curvature in the scanning plane direction, and the reflecting mirror corrects distortion aberration in a cross section parallel to the scanning plane, and scans. In a cross section perpendicular to the plane, an optical conjugate relationship is provided between the deflecting surface of the deflecting means and the surface to be scanned to correct the plane tilt of the deflecting surface and to prevent the curvature of the image plane from occurring. Has a function of converging a light beam on the surface to be scanned, the light beam generating means includes a light source section and a light beam emitted from the light source section on a deflection surface of the deflecting means parallel to the scanning direction. System for forming an image in a circular shape, and the optical system A slit arranged before or after to limit the beam diameter of the incident light beam, and the distance along the optical axis between the optical system and the deflection surface of the deflection means is variable, and By changing the slit width of the slit according to the variable distance, the spot diameter of the light beam focused on the surface to be scanned can be changed.

[Action]

The spherical single lens mainly corrects field curvature and distortion mainly in the main scanning direction. Further, the reflecting mirror corrects the residual amount that could not be corrected by the spherical single lens.
At this time, by using the reflecting mirror, curvature of field in the sub-scanning direction hardly occurs under any condition. Also,
Surface tilt correction is also performed by the curvature of the reflecting mirror in the sub-scanning direction.

In this way, in the present invention, since the residual amount that cannot be corrected by the spherical single lens is corrected by the reflecting mirror, even if the deflection angle is enlarged, the field curvature in the main scanning direction and the sub scanning direction and , All distortion correction can be suppressed within the allowable range.

Further, the beam waist diameter of the light beam near the surface to be scanned can be changed by changing the distance along the optical axis direction between the optical system and the deflecting surface of the deflecting means.
However, as it is, the beam waist position is displaced from the surface to be scanned. Therefore, by further changing the slit width of the slit according to the distance, the position of the beam waist is changed so that the beam waist comes on the surface to be scanned.

In this way, according to the present invention, the spot diameter of the light beam focused on the surface to be scanned can be changed.

〔Example〕

 Hereinafter, examples of the present invention will be described in detail.

FIG. 1 is a perspective view showing a first embodiment of the present invention.

First, the overall configuration of this embodiment will be described.

In this embodiment, a laser light source 1, a coupling lens 2, a slit 3, and a cylindrical lens 4 are moved to a support case 5 in the optical axis direction.
A light beam generator fixed at a design value interval, a deflecting device including a rotating polygon mirror 6, a motor 7, a spherical single lens 8, a toric reflector 9, and a photosensitive drum (scanned surface) 10. And, The toric reflector 9 has an arc shape with a relatively large radius of curvature in the cross section in the main scanning direction x and an arc shape with a relatively small radius of curvature in the cross section in the sub scanning direction y. The shape is such that the radius of curvature decreases from the central portion to both ends.

The operation will be described below.

The diverging light emitted from the laser light source 1 is collimated by the coupling lens 2 into a focused beam close to a parallel light beam. Further, the collimated light boom is incident on the cylindrical lens 4 after the light flux is limited by the fixed or variable slit 3 for adjusting the beam waist position described later. The cylindrical lens 4 is a lens having power only in the sub-scanning direction y, and the light beam forms a linear image on the reflecting surface 6a of the rotary polygon mirror 6 (forms a linear image in the main scanning direction).

Here, the rotary polygon mirror 6 is rotated at a constant speed by the motor 7 to change the reflection angle of the light boom reflected by the mirror surface with time,
The light beam is deflected and scanned. The deflection angle in this embodiment is ± 48 degrees.

The light beam polarized by the rotary polygon mirror 6 passes through the spherical single lens 8, is reflected by the toric reflector 9, and is applied to the photosensitive drum (scanned surface) 10.

In FIG. 1, the spherical single lens 8 mainly corrects field curvature and distortion in the main scanning direction x, and the toric reflector 9 corrects the residual. Further, surface tilt correction is also performed by the curvature of the reflecting mirror 9 in the sub-scanning direction y.

The above correction action will be described in more detail.

FIG. 2 is an explanatory diagram showing changes in the field curvature in the sub-scanning direction when the radius of curvature in the main scanning direction of the toric reflector in FIG. 1 is changed.

In FIG. 2, the horizontal axis is the radius of curvature of the toric reflector in the main scanning direction, and the vertical axis is the field curvature in the sub scanning direction.

Conventionally, when a cylindrical lens is used to correct surface tilt, a field curvature in the sub-scanning direction y occurs when the deflection angle is large. However, when the toric reflector 9 is used as in this embodiment. Is, as is clear from FIG.
Even if the radius of curvature in the main scanning direction x is largely changed, the field curvature in the sub scanning direction y hardly occurs.

Therefore, the remaining amount of the spherical single lens 8 (that is, the field curvature and the distortion in the main scanning direction x) is determined by the main scanning direction x.
When the correction is performed with the curvature of, the condition can be determined without considering the field curvature in the sub-scanning direction y as described above. This is one of the important matters that can obtain good performance with a small number of surfaces in the optical system of the present invention.

Based on the results shown in FIG. 2, the operation of correcting the field curvature in the main scanning direction x and the distortion by the spherical single lens 8 and the toric reflector 9 will be described with reference to FIG.

In FIG. 3, the horizontal axis represents the distortion aberration, the vertical axis represents the field curvature in the main scanning direction, and the points connected by the solid line in the figure show the lens shape (bending coefficient) with the lens power of the spherical single lens 8 kept constant. 2) shows how the curvature of field and the distortion aberration change in the main scanning direction x when (4) is changed. Of course, in this case, the toric reflector 9 is removed. Solid lines 35 to 38 show the above-mentioned changes when the lens powers are different, and the powers are increased in the order of 37, 36, and 35 as compared with the solid line 38.

As a result, as can be seen from FIG. 3, the spherical single lens 8 alone cannot bring the field curvature and distortion in the main scanning direction x to zero or near zero.

On the other hand, a point connected by a broken line in the drawing uses a spherical single lens 8 whose curvature of field and distortion aberration in the main scanning direction x is point P, and the spherical single lens 8 and the surface to be scanned (image surface) 10 are used. As shown in FIG. 1, a toric reflector 9 is installed between the two, and when the curvature of the main scanning direction x is changed, the changes in the field curvature and the distortion aberration in the main scanning direction x are shown. It is shown. Third
As is clear from the figure, by adjusting the curvature of the toric reflector 9 in the main scanning direction x, the main scanning direction x
Both the field curvature and the distortion can be corrected to near zero. Also in this case, the deflection angle is ± 48 degrees as described above.

The above is the description of the correction action of the field curvature and the distortion in the main scanning direction x by the spherical single lens 8 and the toric reflector 9.

In the present embodiment, the spherical single lens 8 and the toric reflector 9 are arranged as shown in FIG.

In order to make the light beam after passing through the spherical single lens 8 incident on the photosensitive drum (scanned surface) 10, it is necessary to set the optical axis of the toric reflecting mirror 9 at an angle of θ ₄ . , Which causes the scan line to bend.

In this embodiment, in order to correct the curvature of the scanning line, the light beam after passing through the spherical single lens 8 is preliminarily scanned in the direction opposite to the curvature of the scanning line generated by inclining the toric reflector 9. The line is curving. In the present embodiment, the optical axis of the spherical single lens 8 is tilted by θ ₃ as a means for generating it. In the present embodiment, θ ₃ is 15 degrees,
Setting θ ₄ to 10 degrees minimizes scan line bow.

Further, the spherical single lens 8 and the toric reflecting mirror 9 in the present embodiment have the following shapes and arrangements.

(1) Spherical single lens Deflection device (rotating polygon mirror 6 and motor 7) Side curvature radius
284.85mm Photosensitive drum 10 side surface Curvature radius 64.04mm Distance between both sides 17.00mm Refractive index 1.51118 (wavelength 780mm) (2) Toric reflector radii of curvature in plane in the main scanning direction x 776.00mm Radius of curvature 93.00 mm (3) Distance between spherical single lens 8 and reflecting mirror 9 68.10 mm (4) Distance from reflecting mirror 9 to sensitivity drum (scan surface) 10 68.5 mm (5) Rotating polygon mirror 6 of deflector Distance (deflection angle 0 degree) between the reflecting surface (deflecting surface) 6a and the spherical single lens 8 of 34.0 mm Next, by the slit 3 and the cylindrical lens 4,
The operation of changing the spot diameter of the light beam on the surface to be scanned (image surface) 10 without changing the shape or arrangement of other optical systems will be described.

FIG. 5 is a cross-sectional view schematically showing each component and a light ray on a surface (that is, a surface in the sub-scanning direction y) perpendicular to the scanning surface along the optical axis of the optical scanning device of FIG. is there. The slit 3 is removed in FIG.

As described above, after the light beam emitted from the laser light source 1 is collimated by the coupling lens 2, only the sub-scanning direction y of the light beam is focused by the cylindrical lens 4, and the deflecting device (rotary polygon mirror 6 and motor 7) is used. A line image is formed on the reflection surface (deflection surface) 6a of the solid line (solid line 11).

Furthermore, the light beam reflected on the reflection surface (deflection surface) 6a is
An image is formed on the surface to be scanned (image surface) 10 at a uniform scanning speed by the spherical single lens 8 and the toric reflector 9. Here, the reflecting surface (deflecting surface) 6a of the deflecting device and the surface to be scanned 10 are in a conjugate relationship, and the spherical single lens 8 and the toric reflecting mirror 9 are the same when the rotary polygon mirror 6 is used for the deflecting device. It has an optical facet correction optical system.

Now, in FIG. 5, when the distance between the light beam generating portion composed of the laser light source 1, the coupling lens 2 and the cylindrical lens 4 and the reflecting surface 6a of the deflecting device is shortened, as shown in the figure, The position of the cylindrical lens 4 has moved to the position indicated by the broken line 4 '(the laser light source 1 and the coupling lens 2 have also moved although not shown in the figure).
The rays look like dashed line 12. In this case, since the position of each optical element after the reflecting surface 6a is constant, the beam diameter of the light beam incident on these optical elements becomes smaller than the solid line 11.

As a result, from the approximate formula of the beam waist diameter shown below,
As shown in FIG. 6, the beam waist diameter ω ₀ ′ of the broken line 12 is larger than the beam waist diameter ω ₀ of the solid line 11.

ω ₀ : Beam waist diameter λ: Wavelength θ: Focusing angle FIG. 6 is an enlarged view of the vicinity (A part) of the surface to be scanned 10 in FIG. 5, where the horizontal axis is the image plane position and the vertical axis is the spot diameter. Show.

That is, by changing the distance between the light beam generator and the reflecting surface 6a of the deflecting device, more precisely, by changing the distance between the cylindrical lens 4 and the reflecting surface 6a, the focusing angle θ changes (incident beam diameter changes). ), And the beam waist diameter ω ₀ can be changed.

However, although the position of the beam waist deviates from the surface to be scanned 10, the present inventors, as shown in FIG.
From the above, it was found that the deviation can be corrected by adjusting the beam diameter d incident on the cylindrical lens 4. Therefore, as the means for adjusting the beam diameter d incident on the cylindrical lens 4, the slit 3 having a hole in a flat plate is used in this embodiment.

FIG. 8 is an enlarged view of the vicinity (A portion) of the surface to be scanned 10 when the incident beam diameter d is changed by using the slit 3 in FIG. The distance (however, the one closer to the toric reflector 9 with the surface to be scanned 10 as a boundary is represented by minus and the farther one is represented by plus), and the vertical axis represents the spot diameter in the sub-scanning direction y, and the change thereof is shown. It shows the situation.

The solid lines 13 to 17 in the figure show the case where the beam diameter d is different, and the beam diameter d is increased in the order of 14, 15, 16, 17 as compared with the solid line 13.

As a result, as can be seen from FIG. 8, by adjusting the beam diameter d, the beam ust diameter is not changed,
You can change the position of the beam waist. Therefore,
As a result, it is possible to correct the positional deviation of the beam waist due to the movement of the above-mentioned light beam generator, more precisely, the cylindrical lens 4.

Next, in FIG. 9, as an initial value of the position of the light beam generator in FIG. 1, the distance from the flat surface side of the cylindrical lens 4 to the reflecting surface 6a of the rotary polygon mirror 6 is set to 113.6 mm,
Based on this, the change in beam waist diameter ω ₀ on the photosensitive drum (scanned surface) 10 when the light beam generator is moved back and forth in the optical axis direction and the position where this beam waist occurs are shown in FIG. FIG. 6 is an explanatory diagram showing simultaneously the value of the slit width of the slit 3 when adjusting on the (scanned surface) 10; The moving distance of the light beam generator shown on the horizontal axis is represented by plus in the direction toward the deflecting device and minus in the direction away from the deflecting device.

As is apparent from the figure, in this embodiment, the spot diameter of the light beam on the photosensitive drum (scanned surface) 10 is 50 to 140.
It can be arbitrarily adjusted in the range of μm.

Next, FIG. 10 is a perspective view showing a specific example of a supporting portion that allows the above-mentioned light beam generating portion to be moved and adjusted in the optical axis direction.

As shown in FIG. 10, a substrate 30 of the optical scanning device is provided with a convex rail 31 along the optical axis, and the support case 5 of FIG. It can slide in any direction. Furthermore, two elongated holes 32 are provided in parallel with the rail 31, and the set screw 33 is screwed into the fixing plate 34 on the back side of the substrate 30 through the support case 5 and the elongated hole 32. Therefore,
The support case 5 can be fixed in that position by tightening the set screw 33 after adjusting the movement of the support case.

11 is a sectional view taken along line BB in FIG.

As shown in FIG. 11, inside the support case 5, the laser light source 1, the coupling lens 2, the slit 3, and the cylindrical lens 4 are fixed with a design interval. Where slit 3
The slit width is determined by the amount of movement of the support case 5 as described above. In the present embodiment, the slit 3 is provided from the slit mounting hole 19 provided in the support case 5 according to the amount of movement.
Insert.

FIG. 12 is an explanatory diagram showing the amount of field curvature for each scanning position in the first embodiment of the present invention.

In FIG. 12, the horizontal axis represents the amount of curvature of field and the vertical axis represents the scanning position. In this scanning position, the central position of the scanning line is set to 0, and each position on one side of the scanning line is relatively represented. Further, the solid lines 39 and 40 are the field curvatures in the main scanning direction x, the broken lines 41 and 42 are the field curvatures in the sub scanning direction y, and the solid lines 39 and the broken lines 41 indicate the spot diameter on the photosensitive drum (scanned surface) 10. In the case of 100 μm, the solid line 40 and the broken line 42 indicate the photosensitive drum (scanned surface) 10
This is the case when the upper spot diameter is 50 μm.

As is clear from the figure, the field curvature is within ± 1 mm in each case.

Next, FIG. 13 is an explanatory diagram showing the amount of distortion aberration with respect to each scanning position in the first embodiment of the present invention.

In FIG. 13, the horizontal axis represents the amount of distortion and the vertical axis represents the scanning position.

The solid line 43 indicates that the spot diameter on the photosensitive drum (scanned surface) 10 is 50.
These are the characteristics in the case of μm and 100 μm, respectively, and as is clear from the figure, values within ± 0.2 mm are obtained.

In this embodiment, the movement of the light beam generator and the slit 3
Although the adjustment of the slit width is performed individually, the adjustment can be further facilitated by using a unit in which the movement and the adjustment of the slit width are interlocked.

Further, as described above, in this embodiment, the slit 3
Is arranged between the coupling lens 2 and the cylindrical lens 4, which is between the laser light source 1 and the coupling lens 2.
Alternatively, the structure arranged on the exit side of the cylindrical lens 4 does not matter.

Further, in the present embodiment, the entire light beam generator is moved in the optical axis direction. However, the laser light source 1, the coupling lens 2 and the slit 3 are fixed to the design values, and only the cylindrical lens 4 is moved in the optical axis direction. It does not matter whether the laser light source 1 and the coupling lens 2 are fixed to the design values and the slit 3 and the cylindrical lens 4 are integrally moved in the optical axis direction.

Next, FIG. 14 is a perspective view showing a second embodiment of the present invention.

14, the same components as those in FIG. 1 are designated by the same reference numerals.

As shown in FIG. 14, the present embodiment is different from the first embodiment in that a plane mirror 18 is provided between the spherical single lens 8 and the toric reflector 9.

As a result, in the first embodiment, the light beam is emitted from the photosensitive drum 10.
Since it is incident from above, there was a tendency that the thickness of the entire optical scanning device becomes large, but in this embodiment, since the light beam can be incident from the side of the photosensitive drum 10,
The thickness of the entire optical scanning device can be further reduced.

〔The invention's effect〕

As described above, according to the present invention, even if the deflection angle of the deflecting means is enlarged, it is possible to correct the field curvature in the main scanning direction and the sub scanning direction and the distortion aberration within the allowable range. Therefore, despite the simple optical system configuration, the deflection angle is set to 48
Since the optical path length between the deflecting means and the surface to be scanned can be shortened to half or less of the conventional one, the overall size of the apparatus can be reduced.

Further, according to the present invention, since the spot diameter of the light beam on the surface to be scanned can be arbitrarily changed, the spot diameter is preset so as to match the printing density of the laser printer in which the optical scanning device is to be mounted. With adjustment, a laser printer designed for any print density can be installed. Therefore, it is not necessary to redesign the optical scanning device according to the print density of the laser printer as in the conventional case.

[Brief description of drawings]

FIG. 1 is a perspective view showing the first embodiment of the present invention, and FIG. 2 is a field curvature in the sub-scanning direction when the radius of curvature in the main scanning direction of the toric reflector in FIG. 1 is changed. 4 is an explanatory view showing a change in the above, FIG. 3 is an explanatory view for explaining the correction function of the field curvature and the distortion aberration in the main scanning direction by the spherical single lens and the toric reflector in FIG. 1, FIG. FIG. 5 is a side view of a main part in FIG. 1, FIG. 5 is a cross-sectional view schematically showing each component and light rays in the sub-scanning direction cross section along the optical axis in FIG. 6 is an enlarged view of a portion A in FIG. 5, FIG. 7 is a cross-sectional view schematically showing each component and light ray in a cross section in the sub-scanning direction along the optical axis in FIG. The figure shows an enlarged view of part A when the beam diameter is changed by the slit in FIG. 7, and FIG. Changes in the beam waist diameter in the sub-scanning direction on the scanned surface and changes in the slit width for positioning the beam waist on the scanned surface when the light beam generator in the figure is moved in the optical axis direction. And FIG. 10 is a perspective view showing a specific example of a support portion for moving and adjusting the light beam generating portion in the optical axis direction in FIG. 1, and FIG. 11 is B of FIG. FIG. 12 is a cross-sectional view in the direction B, FIG. 12 is an explanatory view showing the amount of field curvature with respect to each scanning position in the first embodiment of the present invention, and FIG. FIG. 14 is an explanatory view showing the amount of distortion aberration with respect to the scanning position, and FIG. 14 is a perspective view showing a second embodiment of the present invention. Explanation of reference numerals 1 ... Laser light source, 2 ... Coupling lens, 3 ... Slit, 4 ... Cylindrical lens, 5 ... Support case,
6 ... Rotating polygon mirror, 6a ... Reflecting surface, 7 ... Motor, 8 ...
… Spherical single lens, 9… toric reflector, 10…
... Photosensitive drum (scanned surface, image surface), 11, 12 ... Rays, 18
…… Plane mirror, 19 …… Slit mounting hole, 30 …… Board, 31
...... Rail, 32 …… Oval hole, 33 …… Set screw, 34 …… Fixing plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takesuke Maruyama Inventor Takesuke Maruyama 292 Yoshida-cho, Totsuka-ku, Yokohama City, Kanagawa Prefecture Home Appliances Research Laboratory, Hitachi, Ltd. No. 1 Incorporated company Hitachi Ltd. Taga factory (56) Reference JP-A-60-186821 (JP, A) JP-A-58-63915 (JP, A) JP-A-62-65011 (JP, A) JP 61-126528 (JP, A)

Claims (3)

[Claims] 1. A light beam generating means for generating a light beam,
Deflection means for deflecting the generated light beam by the deflection surface to deflect the light beam, a surface to be scanned, and f · θ for forming an image of the light beam deflected by the deflection means on the surface to be scanned. And an imaging optical system having characteristics,
In the optical scanning device that scans the surface to be scanned with the light beam deflected by the deflecting means, the imaging optical system has a spherical single lens and a cross section of the light beam along the scanning direction is relatively large. A circular arc having a radius of curvature is formed, and a cross section along a vertical direction perpendicular to the scanning direction has an arc shape having a relatively small radius of curvature, and the circular arc having a relatively small radius of curvature is a central position in the scanning direction. To the both ends, the radius of curvature tends to become gradually smaller, and a reflecting mirror having a reflecting surface forming a toric surface such as a barrel-shaped surface as a whole, and the spherical single lens is deflected by the deflecting means. When the light beam is focused on the surface to be scanned through the reflecting mirror to form an image, it has a function of correcting the field curvature in the scanning plane direction. Distortion aberration is corrected in a cross section parallel to the plane, and in the cross section perpendicular to the scanning plane, an optical conjugate relationship is provided between the deflection surface of the deflecting means and the surface to be scanned to obtain the deflection surface. Has a function of correcting the surface tilt and converging the light beam on the surface to be scanned without generating the curvature of the image plane, the light beam generating means includes a light source unit and a light beam emitted from the light source unit. An optical system for forming a linear image parallel to the scanning direction on the deflecting surface of the deflecting means, and a slit arranged in a front stage or a rear stage of the optical system for limiting a beam diameter of an incident light beam. By changing the distance along the optical axis between the optical system and the deflecting surface of the deflecting means and changing the slit width of the slit according to the variable distance, the connection on the surface to be scanned is performed. The spot diameter of the imaged light beam can be changed An optical scanning device characterized in that. 2. The optical scanning device according to claim 1, wherein the light beam generating means is supported by a supporting means capable of transporting the light beam generating means along the optical axis direction. An optical scanning device. 3. The optical scanning device according to claim 1, wherein the light source section of the light beam generating means is fixed at a predetermined position, and the optical system and the slit both have the optical axis direction. An optical scanning device, characterized in that the optical scanning device is supported by a supporting means that can be conveyed along the.