JP2000180763A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve uniformity of the beam diameter of a scanning line, without inviting complication in constitution or deteriorating the correction of inclination by providing an optical system between a light source and a scanning means, with a means for correcting the beam diameter of a light beam at a scanning position other than a scanning center position. SOLUTION: An optical unit 10A is provided with a laser diode array (LD) 12, having plural light emitting points respectively emitting the light beams. Also, a collimator lens 14 for making the incident light beams into the almost parallel light beams, an aperture 16 and a cylinder lens 18 which is a correction means forming an image at a polygon mirror 24, only in a non-scanning direction and correcting the beam diameter of the light beam are arranged at the downstream side of the emitting direction of the light beams emitted from the light-emitting points of the array 12. Since the light beam emitted from the light-emitting point outside the optical axis of the lens 14 is distorted, by making the bus of the lens 18 slanted in the direction opposite to that of the twisting. Thus, twisting of the light beam can be corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device, and more particularly, to a light scanning device that scans a surface to be scanned by using a light beam emitted from a light source having a plurality of light emitting units each emitting a light beam. It relates to a scanning device.

[0002]

2. Description of the Related Art Conventionally, a light source having a plurality of laser diodes in an array (laser diode array;
An optical scanning device using a D array is known.

The distance between the light emitting points of each laser diode is 10
LD arrays of about 0 μm are easier to manufacture than those of about 15 μm and are therefore less expensive. As described above, as a technique for realizing a high-resolution scanning pitch using an inexpensive LD array in which the distance between each light emitting point is relatively large,
Japanese Patent Laid-Open No. 6-1 for performing interlaced scanning
There is a technique described in JP-A-09-994, and a technique described in Japanese Patent Publication No. 64-10806 in which an LD array is tilted.

In the technique described in Japanese Patent Application Laid-Open No. Hei 6-109994, as shown in FIG. 23, four light beams 52A, 52B, 52C and 52D emitted from an LD array 52 are used.
Is used to form an image on the reflection surface of the polygon mirror 60 only in a direction (hereinafter, referred to as a non-scanning direction) intersecting the scanning direction of the light beam (hereinafter, referred to as a non-scanning direction). Cylinder lens 58
Are sequentially reflected by the reflection surface of the polygon mirror 60 that scans the light beam, pass through the scanning lens 62 that condenses the light beam on the photoconductor 64 and scans the light beam at a constant speed, and reaches the photoconductor 64.

As shown in FIG. 24, the light emitting points 1A, 1B, 1C and 1D of the LD array 52 are arranged perpendicularly to the scanning direction, and the scanning pitch on the photoreceptor 64 is equal to the target resolution. Interlaced scanning is performed so as to be an integral multiple. FIG. 25 is a schematic diagram showing the state of interlaced scanning. In FIG. 25, the light beams to be written simultaneously are shown as A, B, C, and D arranged in the vertical direction in FIG. The scanning pitch is doubled. By performing the interlaced scanning in this manner, even if an LD array having a relatively large light emitting point interval is used, a scanning line with a smaller interval than the interval corresponding to the light emitting point interval can be formed on the photosensitive member, and thus the scanning can be simplified. An optical scanning device can be manufactured with the configuration.

[0006] However, Japanese Patent Application Laid-Open No.
In the technique described in Japanese Patent Application Laid-Open No. 4 (1999) -1995, there is a problem that a color difference occurs between the scanning end portion and the center portion. This will be specifically described as follows.

For example, if the intervals between the light emitting points are 100 μm and the number of light emitting points is 5, when the light emitting point located at the center is aligned with the optical axis of the collimator lens, the light emitting points located at both ends are Each will be 200 μm away from the center.

As described above, when the light emitting point is separated from the optical axis of the collimator lens, the beam diameter becomes large at the end of the scanning line on the photosensitive member. On the other hand, since the beam diameter does not increase at the center of the scanning line, uniformity of the beam diameter within one scanning line cannot be maintained.

Table 1 shows the scanning direction (TA) of the center and the end of the scanning line by each light emitting point when the number of light emitting points is five.
FIG. 26 shows an example of a beam diameter in a non-scanning direction (expressed as SAG) and a beam diameter in a non-scanning direction (expressed as SAG). FIG. Is illustrated. In Table 1 and FIG. 26, the light emitting points with an offset of 0 are arranged so as to substantially coincide with the optical axis of the collimator lens. For example, the light emitting points with an offset of -0.2 mm are described above. 0.2 mm from the light emitting point where the offset is set to 0 to one end side
(200 μm) The light emitting point with an offset of 0.2 mm is arranged at a distance of 0.2 mm to the other end from the light emitting point with the offset of 0. It is.

[0010]

[Table 1]

As shown in Table 1 and FIG. 26, the beam diameter of the scanning line by the light emitting point arranged so as to substantially coincide with the optical axis of the collimator lens depends on the scanning position in both the non-scanning direction and the scanning direction. However, the beam diameter of the scanning line at the light emitting point offset from the optical axis of the collimator lens becomes larger as the offset amount increases, as the beam diameter at the end of the scanning line increases.

Due to the difference in beam diameter, a color difference occurs between the end and the center of the scanning line.

As a technique that can be applied to solve this problem, there is a technique described in Japanese Patent Application Laid-Open No. 9-96773.

In this technique, as shown in FIG. 27, a light beam emitted from a light source 70 is provided with a collimator lens 72 for making divergent light from the light source 70 substantially parallel, and an aperture 74.
And a cylinder lens 76 that forms an image on the polygon mirror 82 only in the non-scanning direction, and further passes through a scanning lens 80 that is reflected by a return mirror 78, condenses a light beam on a photoconductor 88, and scans at a constant speed. After that, the light beam is reflected by the polygon mirror 82 that scans the light beam, passes through the scanning lens 80 again, is reflected by the turning mirror 84 and the cylinder mirror 86 in order, and reaches the photosensitive member 88.

In this configuration, as shown in FIG. 28, the uniformity of the beam diameter on the scanning line is intended to be enhanced by tilting the lenses 80A and 80B constituting the scanning lens 80 in the non-scanning direction.

On the other hand, in the technique described in Japanese Patent Publication No. 64-10806, as shown in FIG. 29, the LD array 52 'is inclined with respect to the scanning direction so that the scanning pitch matches the target resolution.

[0017]

However, the technique disclosed in Japanese Patent Application Laid-Open No. 9-96773 has a problem that when the scanning lens is greatly inclined, the tilt correction of the optical unit is deteriorated (banding occurs). there were.
This will be specifically described as follows.

FIG. 30A shows a scanning lens (F in FIG. 30).
30 is a graph showing when the inclination angle of the (θ lens) is optimum, and the tilt correction error amount (expressed as wobble in FIG. 30) at that time is 0. 0 on the photoconductor when the polygon mirror is 120 seconds. 3 μm, and 4 μm even when the conjugate point position (expressed as DOF (defocus amount)) fluctuates ± 1 mm.
m or less. Also, the amount of tilt correction error at the center (expressed as COS) and at the end (expressed as SOS) of the scan line is substantially the same.

FIG. 30B shows a case where the scanning lens is further inclined by 4 ° with respect to the inclination angle of the scanning lens in FIG.
On the photoreceptor, the tilt correction error amount is 1.4 to 2.6 μ.
m, and when the conjugate point position fluctuates ± 1 mm, about 5.
7 μm.

FIG. 30C shows a case where the scanning lens is further tilted by 4 °. The inclination correction error amount becomes large, and the inclination of the inclination correction error amount changes between the center and the end of the scanning line, so that the lens cannot be used.

In general, in order to obtain good image quality, the amount of tilt correction error is 4 including the time when the conjugate point position fluctuates ± 1 mm.
μm or less is required. If the uniformity of the beam diameter of the scanning line is to be increased by tilting the scanning lens as in the technique described in Japanese Patent Application Laid-Open No. 9-96773, FIG. B) and a tilt correction error amount as shown in FIG. 30 (C) occurs, and the image quality of the resulting image deteriorates.

On the other hand, in the technique described in Japanese Patent Publication No. 64-10806, the detection timing of the light beam by the SOS (Start Of Scan) sensor for detecting the timing of the start of scanning on the surface to be scanned is different for each light beam. However, there is a problem in that a means for correcting the timing is required, and the configuration of the apparatus becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an optical scanning method capable of improving the uniformity of the beam diameter of a scanning line without causing a complicated structure and deterioration of tilt correction. It is intended to provide a device.

[0024]

According to another aspect of the present invention, there is provided an optical scanning device, comprising: a light source having a plurality of light emitting units for emitting light beams; and a light beam emitted from the light source. From a first optical system including a first lens having substantially parallel light and a second lens having power only in a direction intersecting the scanning direction of the light beam; and Scanning means for scanning the emitted light beam;
Correction means disposed on an optical system between the light source and the scanning means and for correcting the beam diameter of the light beam at a scanning position other than the scanning center position; and the light beam at a substantially constant speed on the surface to be scanned. And a second optical system for scanning the light beam and condensing the light beam on the surface to be scanned.

According to the optical scanning device of the first aspect, a plurality of light beams are emitted from the light source, and the plurality of light beams are emitted from the first light source.
After being made into substantially parallel light by the lens, the light beam passes through a second lens having power only in a direction intersecting the scanning direction of the light beam, and then scanned by the scanning means. Note that a collimator lens or the like can be applied as the first lens, a cylinder lens or the like can be applied as the second lens, and a polygon mirror or the like can be applied as the scanning unit.

Here, in the optical scanning device according to the first aspect, the correction unit disposed on the optical system between the light source and the scanning unit causes the beam of the light beam at a scanning position other than the scanning center position. The diameter is corrected.

The light beam scanned by the scanning means as described above is scanned on the surface to be scanned by the second optical system at a substantially constant speed and is focused on the surface to be scanned.

As described above, according to the optical scanning device of the first aspect, the beam diameter of the light beam at the scanning position other than the scanning center position is corrected on the optical system between the light source and the scanning means. Since the correction means is arranged, the beam diameter of the scanning line does not incline the light source with respect to the scanning direction or incline the scanning lens in the non-scanning direction, that is, without complicating the configuration and deteriorating the tilt correction. Can be improved.

According to a second aspect of the present invention, in the first aspect of the present invention, the correction means includes a cylinder lens whose generating line has a curvature or an inclination in a direction intersecting a scanning direction of the light beam. It is preferred that

According to a third aspect of the present invention, in the first or second aspect, a direction intersecting the optical path of the light beam with the optical axis between the light source and the correction means. It is preferable to further comprise a deflecting means for deflecting the light to a predetermined angle.

According to a fourth aspect of the present invention, in the third aspect of the present invention, there is provided a separating means for changing a traveling direction of a light beam emitted from each of the plurality of light emitting portions of the light source. It is preferable to further provide.

Further, like the invention according to claim 5, in the invention according to any one of claims 2 to 4,
It is preferable that the cylinder lens includes a plurality of lenses, and that a generating line has a curvature or an inclination in a direction in which at least one lens intersects a scanning direction of the light beam.

Further, as in the sixth aspect of the present invention, the optical system according to any one of the first to fifth aspects can be an overfilled optical system.

According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the light beam crosses substantially in front of the second optical system, in a double path, and in the scanning direction of the light beam. It is preferable that the light is incident at an angle in the direction in which the light beam travels.

Further, like the invention according to claim 8, in the invention according to any one of claims 2 to 7,
It is preferable that the cylinder lens is made of a resin or glass mold part.

Also, as in the ninth aspect, in the eighth aspect, it is preferable that the cylinder lens has a plurality of generatrix.

According to a tenth aspect of the present invention, there is provided an optical scanning device, comprising: a light source having a plurality of light emitting portions arranged linearly and each emitting a light beam; and a light emitting portion on one end side of the plurality of light emitting portions of the light source. A second lens having a power only in a direction intersecting a scanning direction of the light beam and a first lens which is disposed so that the axes thereof substantially coincide with each other and makes the light beam emitted from the light source substantially parallel light;
A first optical system including a lens, and an adjusting unit that adjusts a generating line of the second lens so as to have a curvature or an inclination in a direction intersecting a scanning direction of the light beam; and Scanning means for scanning a light beam emitted from the first optical system; and second optical means for scanning the light beam on the surface to be scanned at a substantially constant speed and condensing the light beam on the surface to be scanned. System.

According to the optical scanning device of the tenth aspect,
A plurality of light beams are emitted from a light source having a plurality of light emitting portions that are linearly arranged and each emit a light beam, and are arranged such that an optical axis substantially coincides with a light emitting portion on one end side of the plurality of light emitting portions of the light source. After being converted into substantially parallel light by the first lens,
After passing through the second lens having power only in a direction intersecting the scanning direction of the light beam, scanning is performed by the scanning unit. Note that a collimator lens or the like can be applied as the first lens, a cylinder lens or the like can be applied as the second lens, and a polygon mirror or the like can be applied as the scanning unit.

Here, the second lens is adjusted by the adjusting means so that the generatrix has a curvature or an inclination in a direction intersecting the scanning direction of the light beam, thereby correcting the beam diameter of the light beam. Can be.

The light beam scanned by the scanning means as described above is scanned at substantially the same speed on the surface to be scanned by the second optical system and is focused on the surface to be scanned.

As described above, according to the optical scanning device of the tenth aspect, the first lens is arranged such that the optical axis substantially coincides with the light emitting portion on one end side of the plurality of light emitting portions of the light source. Since the generatrix of the second lens is adjusted to have a curvature or inclination in a direction intersecting the scanning direction of the light beam, the light source may be inclined with respect to the scanning direction or the scanning lens may be inclined with respect to the non-scanning direction. In other words, it is possible to improve the uniformity of the beam diameter of the scanning line without causing a complicated configuration and deterioration of the tilt correction.

Incidentally, as in the invention according to claim 11,
In the invention according to claim 10, the adjusting means includes a member to be installed on which the second lens is installed, and a pressing member for pressing the second lens against the member to be installed, and It is preferable that at least one of the installation surface of the member and the pressing surface of the pressing member has a curvature.

Further, as in the invention according to claim 12,
In the invention according to claim 10 or 11, it is preferable that the second lens is subjected to chemical processing.

Further, according to the invention of claim 13,
In the invention according to any one of claims 10 to 12, it is preferable that the second lens is made of a resin or a glass mold part.

[0045]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] First, referring to FIG.
The configuration of the optical unit 10A according to the first embodiment will be described. FIG. 1 is a schematic configuration diagram showing the configuration of an optical unit when the optical scanning device of the present invention is applied to an underfilled optical system. Here, in the underfilled optical system, the beam diameter in the scanning direction of the light beam reaching the polygon mirror is smaller than the rotation direction width of the reflection surface of the polygon mirror, and the rotation angle when the light beam reaches the end of the scanning line. This also refers to an optical system in which the light beam hardly deviates from the reflecting surface in the rotation direction of the polygon mirror. On the other hand, an overfilled optical system described later refers to an optical system in which a light beam larger than the rotation width of the reflection surface of the polygon mirror is made incident on the polygon mirror and scanned by the polygon mirror.

As shown in FIG. 1, the optical unit 10A according to the first embodiment is provided with an LD array 12 having a plurality of light emitting points for emitting light beams.
On the downstream side in the emission direction of the light beam from the light emitting point of the D array 12, the collimator lens 14, the aperture 16, which makes the incident light beam (divergent light) substantially parallel light, and the polygon mirror 24 described later only in the non-scanning direction. A cylinder lens 18 for forming an image and a folding mirror 20 are sequentially provided.

The polygon mirror 24 which scans the light beam in the direction of reflection of the light beam by the folding mirror 20 is used.
In the direction of reflection of the light beam by the polygon mirror 24, a scanning lens 26 and a return mirror 28 constituted by an Fθ lens for condensing and scanning the light beam at a constant speed with a photoreceptor 34 described later are sequentially arranged. A cylinder mirror 30 is provided in the direction in which the turning mirror 28 reflects the light beam, and a photoreceptor 34 is provided in the direction in which the cylinder mirror 30 reflects the light beam.

Incidentally, the polygon mirror 24 is covered with a polygon mirror cover 22 to prevent dust and the like, and the components of the optical unit 10A other than the photoreceptor 34 are covered with a cover (not shown). Accordingly, the light beam enters and exits the polygon mirror 24 via the polygon mirror cover 22, and is emitted from the polygon mirror 24.
The light beam reflected by the cylinder mirror 30 reaches the photosensitive member 34 via the window 32 provided on the cover (not shown).

In FIG. 1, for convenience, the folding mirror 2 is used.
0, polygon mirror 24, return mirror 28, and cylinder mirror 30 each show only the reflection surface, only the surface as photoconductor 34, and only one scanning position. In addition, -148.5 mm and 1 in FIG.
48.5 mm represents the position of both ends of the scanning range on the photoconductor 34 in the first embodiment as a distance from the center of the scanning range.

Here, as shown in FIG. 2A, the cylinder lens 18 in the first embodiment has a bus 18A.
Is a shape (hereinafter, referred to as an R type) having a downwardly convex curvature with the center in the scanning direction as an inflection point. The direction (arrangement direction) of each light emitting point of the LD array 12 is arranged to be perpendicular to the scanning direction.

The folding mirrors 20 and 28 are unnecessary if the arrangement of the optical unit 10A permits. Also,
If there is no problem in optical performance, the polygon mirror cover 22
And the window 32 is unnecessary.

The LD array 12 is the light source of the present invention, the collimator lens 14 is the first lens of the present invention, the cylinder lens 18 is the second lens and the correcting means of the present invention, and the polygon mirror 24 is the scanning of the present invention. Means, scanning lens 2
Reference numeral 6 corresponds to the second optical system of the present invention.

The optical unit 10 configured as described above
In A, the light beam emitted from the LD array 12 sequentially passes through the collimator lens 14, the aperture 16, and the cylinder lens 18, is reflected by the return mirror 20, and is reflected by the polygon mirror 24 via the polygon mirror cover 22. , Passes through the scanning lens 26 and returns to the return mirror 28, the cylinder mirror 30 and the window 32.
, Sequentially arrive at the photoreceptor 34.

As described above, the LD array 12 is arranged so that each light emitting point is in a direction (for example, vertical) crossing the scanning direction. (See JP-A-6-1099).
No. 94, etc.).

Here, it is assumed that the cylinder lens 18 is in a normal state (the bus is straight and the bus is arranged so as to be substantially parallel to the scanning direction of the light beam). In this case, when the light emitting point of the LD array 12 passes through the optical axis of the collimator lens 14, the light beam passes horizontally through the optical axis of the scanning lens 26, but the light emitting point of the LD array 12 is When the light beam is separated from the axis (offset), the light beam travels at an angle in the non-scanning direction after passing through the collimator lens 14, and does not pass through the optical axis with respect to the scanning lens 26 and has an angle. pass.

This phenomenon becomes more remarkable as the light emitting point of the LD array 12 becomes farther from the optical axis of the collimator lens 14.

If there is a light emitting point outside the optical axis of the collimator lens 14, the light beam is twisted and
6 is incident.

For this purpose, a light beam off the optical axis is applied to the photosensitive member 34.
When scanning above, the beam diameter gradually increases as approaching the end of the scanning line. At this time, the beam waist diameter increases without changing the focal position of the light beam.

The light beam starts to be twisted when the LD array 12
And a polygon mirror 24 (hereinafter, referred to as a pre-polygon), so that a member for correcting the light beam is arranged in the optical path of the pre-polygon in a direction to correct the twist of the light beam. Is valid. The correction of the torsion of the light beam will be described with reference to FIG.

FIG. 3 shows an overfilled optical system shown in FIGS. 15 and 16 which will be described later, in which a normal cylinder line (generating line is used) is applied as the cylinder lens 18 and the generating line of the cylinder lens is This shows simulation results when the optical axis is tilted about the optical axis. The horizontal axis shows the tilt angle of the generatrix of the cylinder lens 18, and the vertical axis shows the beam diameter. In the same figure, 148.5 s and -148.5 s are the non-scanning direction (SAG direction) at one end and the other end of the scanning line, respectively.
Are 148.5t and -148.5t in the scanning direction (TA) at one end and the other end of the scanning line, respectively.
Ns), 0s represents the beam diameter in the non-scanning direction at the center of the scanning line, and 0t represents the beam diameter in the scanning direction at the center of the scanning line. Further, 148.5 and -148.5 are the positions of one end and the other end, respectively, when the center of the scanning line is 0 (148.5 mm and -148.5 m from the center, respectively).
m position).

FIG. 3C is a graph in the case where the light emitting point position is offset to the negative side with respect to the optical axis of the collimator lens. (A design in which is 0 °), the beam diameter of the light beam at both ends is larger than the center of the scanning line.

Here, when the correction is performed in the + direction (when the generatrix angle of the cylinder lens 18 is made larger than 0 °), the beam diameter of the light beam becomes small at the negative end of the scanning position, and becomes slightly large at the center. And significantly increased at the + side end.

On the other hand, when the correction is performed in the minus direction (when the generatrix angle of the cylinder lens 18 is made smaller than 0 °), the beam diameter of the light beam becomes smaller at the + side end of the scanning position and becomes slightly larger at the center. ,-Side end portion is significantly large.

That is, the uniformity of the beam diameter is improved by inserting an optical member into the pre-polygon which reverses the direction of correction on the + side and-side of the scanning direction with respect to the center of the scanning position as a boundary. Can be.

Therefore, in the first embodiment, as described above, in order to correct the torsion of the light beam generated in the pre-polygon, the bus 18A serves as an optical member for correcting the beam diameter. A cylindrical lens 18 (see FIG. 2A) having a downward convex R shape is applied. Therefore, the cylinder lens 18 corresponds to the correcting means according to the first aspect of the present invention.

Although the light beam is not twisted by the cylinder lens when the bus is substantially parallel to the scanning direction, the light beam is twisted when the bus is inclined with respect to the scanning direction. On the other hand, since the light beam emitted from the emission point outside the optical axis of the collimator lens is twisted as described above, it is possible to correct the twist of the light beam by inclining the generating line of the cylinder lens in a direction opposite to the twist. it can.

Next, the steps of manufacturing the cylinder lens 18 will be described.

The cylinder lens 1 according to the first embodiment
Reference numeral 8 denotes a power having a focal point on the polygon mirror 24 in the non-scanning direction and no power in the scanning direction.
The bus has a shape (R) having a curvature in a direction perpendicular to the scanning direction.
Type).

FIG. 4 shows a toric shape. When a light beam (a light beam of a predetermined size) is incident in the direction of arrow A, the shape is similar to that of a scanning lens generally used in a printer or the like. In this embodiment, a cylinder lens having an R in the generatrix is configured by applying a light beam to the toric shape in the direction of arrow B. That is, the shape of the cylinder lens 18 according to the first embodiment is a shape of only the upper half of the rotation center axis in the toric shape of FIG.

Therefore, when a light beam is incident in the direction of arrow A, different powers are generated in both the non-scanning direction and the scanning direction. It has virtually no power in the direction. Then, only the generatrix has a curved shape.

In the first embodiment, this shape is manufactured using a metal mold, and the cylinder lens 18 is manufactured using a glass mold.
To produce

X, Y, Z constituting the toric shape
Can be obtained by the following equations.

Assuming that Φm = (2πm) / 20 θn = (2πn) / 20, Xm, n = (R + r · cos (θn)) · cos (Φ
m) Ym, n = (R + r · cos (θn)) · sin (Φ
m) Zm, n = r · sin (θn) where Φm is an arc range in the scanning direction (a parameter for determining the size), θn is an arc range in the non-scanning direction (a parameter for determining the size), and r is The radius of curvature in the non-scanning direction is
R indicates the radius of curvature in the scanning direction.

FIG. 4 used in the above description shows the shape when m and n are values from 0 to 20, and FIG.
Indicates a shape when m is a value from 13 to 17 and n is a value from 3 to 7. 4 and 5 both show that the value of r is 55.5 mm and the value of R is 286.
mm. In practice, the shape shown in FIG. 5 is applied.

As described in detail above, in the optical scanning device according to the first embodiment, the pre-polygon optical system
The insertion of the R-shaped cylinder lens whose bus line has an inflection point at the center in the scanning direction allows the uniformity of the beam diameter to be improved.

Further, in the optical scanning device according to the first embodiment, since the cylinder lens is formed of a glass mold, the cylinder lens can be easily manufactured as compared with the case where it is manufactured by an existing lens polishing process. Can be.

In the first embodiment, the case where the cylinder lens 18 is as shown in FIG. 2A has been described. However, the present invention is not limited to this, and the generatrix is formed in the non-scanning direction. What is necessary is just to have a curvature or an inclination, for example, as shown in FIG.
A may be an R-shape having an upwardly convex shape with an inflection point at the center in the scanning direction, or as shown in FIGS.
(B), that is, each of the generatrixes 18A may have an inverted V-shape and a V-shape with the inflection point at the center in the scanning direction.

Here, the cylinder lens having an R-shaped bus shape is easier to mount on a device than a V-shaped cylinder lens, and the change near the inflection point is small. Is superior to a V-shaped cylinder lens.

In the first embodiment, the case where a conventionally used cylinder lens is applied as the correcting means of the present invention has been described. However, the present invention is not limited to this. Another optical member functioning as a correction unit may be inserted into the pre-polygon.

Further, in the first embodiment, the case where the cylinder lens 18 is formed of a glass mold has been described, but the present invention is not limited to this, and may be formed of a resin.

[Second Embodiment] First, referring to FIG.
The configuration of the optical unit 10B according to the second embodiment will be described. The same parts as those in FIG. 1 of FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted.

The optical unit 10B according to the second embodiment
Is an acousto-optic modulator that deflects a traveling direction of an incident light beam between a collimator lens 14 and a cylinder lens 18 in accordance with an input signal, as compared with the optical unit 10A according to the first embodiment. The only difference is that an element (hereinafter, referred to as an AOM element) 36 is provided.

In the cylinder lens 18 for beam diameter correction arranged in the pre-polygon, the inclination of the generatrix is opposite on both sides with respect to the center part, so that the beam diameter on the photosensitive member 34 is made uniform. Has a cylinder lens 18
It is necessary to make the center and both ends correspond to the center and both ends of the scanning position on the photosensitive member 34, respectively.

On the other hand, since the optical unit 10B is an under-filled optical system, the light beam in the pre-polygon passes through the same part of each optical component.

Therefore, in the optical unit 10B according to the second embodiment, the AOM element 36 is arranged on the front side of the cylinder lens 18 so as to move the light beam in a direction perpendicular to the optical axis. 13, the light path of the light beam corresponding to the movement from one end of the scanning position on the photoconductor 34 to the other end via the center is changed. As a result, the light beam passes through the cylinder lens 18 in such a manner that the center and the end of the cylinder lens 18 correspond to the center and the end of the scanning position on the photosensitive member 34, and thus the twist of the light beam is corrected. And a light beam having a uniform beam diameter can be obtained.

FIG. 8 is a detailed view from the LD array 12 to the turning mirror 20, and shows how the optical path changes in the AOM element 36. As shown in FIG.
The OM element 36 moves the optical path M of the light beam incident on the cylinder lens 18 in a direction intersecting the optical axis L (for example, in a vertical direction).

As described in detail above, in the optical scanning device according to the second embodiment, the A
An OM element is provided, and the AOM element changes the optical path of the light beam corresponding to the movement of the scanning position from one end to the other end of the scanning position on the photosensitive member, so that the twist of the light beam in the underfilled optical system is corrected. And the uniformity of the beam diameter on the photosensitive member can be improved.

In the second embodiment, the case where the AOM element is applied as the deflecting means of the present invention has been described. However, the present invention is not limited to this.
An EOM element (electro-optic modulation element) or the like may be applied.

[Third Embodiment] First, referring to FIG.
The configuration of the optical unit 10C according to the third embodiment will be described. The optical unit 10C according to the third embodiment is an underfilled optical system.

As shown in FIG. 9, the optical unit 10C according to the third embodiment is provided with an LD array 12 'having four light emitting points for emitting light beams, respectively.
On the downstream side in the emission direction of the light beam from the light emitting point of the LD array 12 ', the collimator lens 14, the aperture 16, which makes the incident light beam (divergent light) substantially parallel light, and the scanning direction in which the light beam in the scanning direction is expanded. , An AOM element 98 for deflecting the traveling direction of the incident light beam, and a power only in the non-scanning direction for condensing the light beam in the non-scanning direction on a reflecting surface of a polygon mirror 24 described later. A cylinder lens 92 having a power and a turning mirror 20 are provided in order. The reflecting direction of the light beam by the turning mirror 20 is a cylinder lens having power only in the scanning direction that makes the light beam substantially parallel in the scanning direction. 94 and a polygon mirror 24 for scanning the light beam are provided in order. The cylinder lens 92 is configured to function also as a beam diameter correcting lens.

In the direction of reflection of the light beam by the polygon mirror 24, the scanning lens 2 constituted by an Fθ lens for condensing the light beam on the photosensitive member and scanning at a constant speed is used.
6, and separation mirrors 96 as separation means for reflecting the four incident light beams in different directions so as to separate the light beams from each other. Is provided,
A window 32 and a photoconductor 34 are provided in the direction in which the light beam is reflected by the cylinder mirror 30.

Note that the folding mirror 20 is unnecessary if the arrangement of the optical unit 10C permits. The window 32 between the cylinder mirror 30 and the photoconductor 34 is
You can delete it if you don't need it.

The optical unit 10 configured as described above
In C, the light beam emitted from the LD array 12 ′ is collimated by the collimator lens 14, aperture 16, cylinder lens 90, AOM element 98, and cylinder lens 92.
Are sequentially reflected by the turning mirror 20.

The light beam reflected by the turning mirror 20 passes through the cylinder lens 94 and passes through the polygon mirror 2.
4, passes through the scanning lens 26 and passes through the separation mirror 9.
After being separated for each light beam by 6, it is reflected by the cylinder mirror 30 and reaches the photoconductor 34 via the window 32.

With such a configuration, as shown in FIG.
Light beam 1 horizontally and parallel to polygon mirror 24
When 2A, 12B, 12C, and 12D are incident, it is necessary to increase the thickness (length in the direction perpendicular to the scanning direction) of the polygon mirror 24.
4 becomes large, the load of the motor for rotating and driving the polygon mirror 24 becomes large, and high-speed rotation becomes impossible.

Therefore, in the optical unit 10C according to the third embodiment, as shown in FIG. 11, a light beam is incident on the polygon mirror 24 at an angle in the horizontal direction. With this configuration, the light beams emitted from the scanning lens 26 are largely separated, so that the distance between the four light beams on the polygon mirror 24 can be reduced, and the thickness of the polygon mirror 24 and the scanning lens 26 can be reduced. Can be reduced. FIG. 11 shows the polygon mirror 24 and the cylinder mirror 30.
2 shows only the light beam and the cylinder mirror 30 located at both ends.

However, by giving an angle to the direction of incidence of the light beam on the polygon mirror 24, a problem arises in that the uniformity of the beam diameter in the scanning direction cannot be maintained.

In order to solve this problem, in the optical unit 10C according to the third embodiment, the cylinder lens 9
2 is a cylinder lens for correcting the beam diameter with an R added to the generatrix, and an AOM element 98 is arranged between the cylinder lens 90 and the cylinder lens 92 to reduce the beam diameter similarly to the second embodiment. It is uniform.

With this configuration, the LD array 1
The present invention can also be applied to a mode in which each light beam 2 ′ is separated by an optical system and the light beams are incident on different photoconductors.

If a motor for rotating the polygon mirror 24 can be used at a low rotation speed, there is no problem even if the light beam enters the polygon mirror 24 horizontally and in parallel. No lens is required.

As described in detail above, in the optical scanning device according to the third embodiment, the cylinder lens for correcting the beam diameter and the AO for changing the traveling direction of the light beam are used.
Since the M element is applied and the light beams emitted from the respective light emitting points of the LD array are configured to be separated from each other, scanning is performed on a plurality of photoconductors with the light beam having a uniform beam diameter. be able to.

[Fourth Embodiment] The optical unit according to the fourth embodiment is different from the optical unit 10B (see FIG. 7) shown in the second embodiment in that the cylinder lens 18
Is a cylinder lens 1 composed of two lenses (a negative lens 18a and a positive lens 18b) shown in FIG.
Only the point 8 'is different. Therefore, the description of the configuration of the optical unit according to the fourth embodiment other than the cylinder lens will be omitted.

The positive lens 18b is the same as the beam diameter correcting cylinder lens 18 described above.

In the second embodiment, it is assumed that the target resolution is realized by interlaced scanning using the inexpensive LD array 12 having a relatively large distance between the light emitting points. In order to reduce the number, it is necessary to reduce the optical magnification of the pre-polygon in the non-scanning direction so that the distance between the polygon mirror and the cylinder lens does not pose a mounting problem.

In order to reduce the optical magnification of the pre-polygon, when the cylinder lens is composed of one lens, as shown in FIG.
It is necessary to increase the power of the polygon mirror 24 so as to approach the polygon mirror 24.
If 8 approaches too much, the polygon mirror 24 scans the light beam, so that the light beam interferes with the cylinder lens.

Therefore, in this case, the limit for reducing the optical magnification is determined by the arrangement of each optical member.

Therefore, in the optical unit according to the fourth embodiment, in order to make the above-described arrangement advantageous,
As shown in FIG.
By configuring with a combination of lenses,
Compared to a case where a single cylinder lens is used, the cylinder lens can be arranged away from the polygon mirror 24. That is, as shown in FIG. 12 (B), when the cylinder lens is composed of one lens, the back focus of the cylinder lens B.I. f
2 is almost the same as the focus f, but as shown in FIG. 12A, the back focus B.2 when the cylinder lens is composed of two lenses. f1 is much larger than the focus f.

As described in detail above, in the optical scanning device according to the fourth embodiment, the cylinder lens is set to the negative and the positive two.
Since it is composed of a single lens and one of the lenses is a lens for correcting the beam diameter, it is possible to make the constraints on the arrangement of the optical components of the pre-polygon advantageous, and to reduce the beam diameter on the photosensitive member. Can be improved.

Although the fourth embodiment has described the case where the positive lens 18b of the cylinder lens 18 'is a lens for correcting the beam diameter, the present invention is not limited to this. At least one of the lenses 18a and 18b may be configured as a beam diameter correcting lens. For example, only the lens 18a may be configured as a beam diameter correcting lens.

However, the lens used as a lens for correcting the beam diameter is a positive lens 18b disposed downstream of the optical path.
Is preferred. That is, if the upstream negative lens 18a is a lens for correcting the beam diameter, the torsion is corrected by the positive lens 18b. Therefore, it is necessary to increase the inclination angle of the generatrix of the lens for correcting the beam diameter. .

Further, in the fourth embodiment, the case where the cylinder lens 18 'is constituted by two lenses has been described, but the present invention is not limited to this, and is constituted by three or more lenses. It is good also as a form. in this case,
As the lens for correcting the beam diameter, any of the above three or more lenses may be used, but for the reasons described above,
It is preferable to target the lens located on the most downstream side of the optical path.

[Fifth Embodiment] First, the configuration of an optical unit 10D according to the fifth embodiment will be described with reference to FIG. FIG. 13 is a schematic configuration diagram showing the configuration of an optical unit when the optical scanning device of the present invention is applied to an overfilled optical system.

As shown in FIG. 13, the optical unit 10D according to the fifth embodiment is provided with an LD array 12 having a plurality of light emitting points for emitting light beams.
The incident light beam (divergent light) is transmitted to the LD array 1 on the downstream side in the emission direction of the light beam from the light emitting point of the LD array 12.
Collimator lens 14 ′, aperture 16, polygon mirror 24 diverging light smaller than the light beam from
A cylinder lens 18 for forming an image only in the non-scanning direction and correcting the beam diameter of the light beam on the photoreceptor 34, and a folding mirror 20 are sequentially provided.

In the reflection direction of the light beam by the folding mirror 20, the cylinder lens 44 having power only in the scanning direction of the light beam, the light amount correction filter 46 for equalizing the light amount in the scanning line, and the light A polygon mirror 24 for scanning the beam is provided in order, and a scanning lens 26 constituted by an Fθ lens for condensing the light beam by the photoreceptor 34 and scanning at a constant speed is provided in the reflection direction of the light beam by the polygon mirror 24. And mirror 2
The cylinder mirror 30 is provided in the direction of reflection of the light beam by the return mirror 28, and the photosensitive member 34 is provided in the direction of reflection of the light beam of the cylinder mirror 30.

In FIG. 13, for convenience, the folding mirror 20, the polygon mirror 24, the folding mirror 28, and the cylinder mirror 30 each show only the reflecting surface, only the surface as the photosensitive member 34, and only one position as the scanning position. Is shown.

Here, the direction (arrangement direction) of each light emitting point of the LD array 12 is arranged so as to be perpendicular to the scanning direction of the light beam.

Note that if the arrangement of the optical unit 10D permits, the folding mirrors 20 and 28 are unnecessary. Also,
It goes without saying that a window may be arranged between the cylinder mirror 30 and the photoconductor 34 as necessary.

The LD array 12 serves as the light source of the present invention, the collimator lens 14 'serves as the first lens of the present invention, the cylinder lens 18 serves as the second lens and the correcting means of the present invention, and
The polygon mirror 24 corresponds to the scanning means of the present invention, and the scanning lens 26 corresponds to the second optical system of the present invention.

The optical unit 10 configured as described above
In D, the light beam emitted from the LD array 12 sequentially passes through the collimator lens 14 ′, the aperture 16 and the cylinder lens 18, is reflected by the return mirror 20, and then is reflected by the cylinder lens 44 and the light amount correction filter 4.
6, the light is reflected by the polygon mirror 24, passes through the scanning lens 26, and reaches the photosensitive member 34 after being reflected by the return mirror 28 and the cylinder mirror 30.

As described above, the LD array 12 is arranged so that each light emitting point is perpendicular to the scanning direction. In this embodiment, the scanning pitch on the photosensitive member 34 is an integral multiple of the target resolution. (See JP-A-6-109994, etc.).

Optical unit 10D according to the fifth embodiment
Is an overfilled optical system, the light beam to be scanned is used by taking out a necessary amount of the pre-polygon light beam on the reflection surface of the polygon mirror 24, and is used as shown in FIGS. As shown in C),
In all optical components including the cylinder lens 18, a light beam passes through a position corresponding to a scanning position on the photoconductor 34.

In the underfilled optical system, as shown in the second embodiment, an AOM element as a deflecting means is inserted in front of a cylinder lens for correcting a beam diameter, and a light beam is emitted in accordance with a scanning position. Was biased. However, in the overfilled optical system, as described above,
Since the light beam is inevitably configured to pass through the position corresponding to the scanning position on the photosensitive member 34 in the cylinder lens 18, the deflection means such as the AOM element becomes unnecessary, and the cost is reduced.

In FIG. 14A, the scanning position on the photosensitive member 34 is 148.5 mm in the + direction from the center of the scanning line.
The light width when the light beam reaches a distant position is shown in FIG.
14B shows the light width when the light beam reaches the center of the scanning line, and FIG. 14C shows 148.5 in the negative direction from the center.
The light width when the light beam reaches a position separated by mm is shown. In each case, a part of the entire light width shown in FIG. 13 is used at each scanning position.

As described in detail above, in the optical scanning device according to the fifth embodiment, since the cylinder lens for correcting the beam diameter is used in the overfilled optical system, the light beam of the light beam is also used in the overfilled optical system. The torsion can be corrected, the uniformity of the beam diameter can be improved, and the cost can be reduced because there is no need to use a deflection unit such as an AOM element.

Further, the cylinder lens 44 of the optical unit according to the fifth embodiment may be a spherical lens that makes the light beam in the scanning direction substantially parallel.

[Sixth Embodiment] First, FIGS.
Referring to, the optical unit 10E according to the sixth embodiment
Will be described. 15 and FIG.
FIG. 15 is a schematic configuration diagram showing a configuration of an optical unit when the optical scanning device of the present invention is applied to an overfilled optical system. FIG. 15 is a plan view and FIG. 16 is a side view.

As shown in FIG. 15, the optical unit 10E according to the sixth embodiment is provided with an LD array 12 having a plurality of light emitting points for emitting light beams.
On the downstream side in the light beam emission direction from the light emitting point of the LD array 12, the collimator lens 14, the aperture 16, which makes the incident light beam (divergent light) substantially parallel, and the expanding lens 38 which expands the light beam in the scanning direction. , And a turning mirror 17 are provided in order. In the direction of reflection of the light beam by the turning mirror 17, a cylinder lens 18 that forms an image only in a non-scanning direction on a polygon mirror 24 described later and corrects the beam diameter of the light beam, And a folding mirror 20 are provided in order.

In the direction of reflection of the light beam by the folding mirror 20, a scanning lens 26 constituted by an Fθ lens for scanning the light beam at a constant speed, and a polygon mirror 24 for scanning the light beam are provided in this order. The scanning lens 26 is provided so as to be positioned also in the direction in which the polygon mirror 24 reflects the light beam.
Therefore, the scanning lens 26 is arranged so that both the light beam incident on the polygon mirror 24 and the light beam reflected from the polygon mirror 24 pass (so-called double pass).

Further, a reflection mirror 28 is provided downstream of the scanning lens 26 in the direction of reflection of the light beam by the polygon mirror 24, and a cylinder mirror 30 is provided in the direction of reflection of the light beam by the reflection mirror 28. In the reflection direction of the light beam of the cylinder mirror 30,
As shown in FIG. 16, a window 32 and a photoreceptor 34 are provided in order.

A folding mirror 47 is provided at a position in the direction in which the light beam is reflected by the cylinder mirror 30 and does not affect the scanning area on the photosensitive member 34, and an SOS is provided in the direction in which the reflecting mirror 47 reflects the light beam. A lens 48 and an SOS sensor 49 are provided in order.

Here, the direction (arrangement direction) of each light emitting point of the LD array 12 is arranged so as to be perpendicular to the scanning direction of the light beam. The optical system of the optical unit 10E is a scanning lens (fθ lens) front incidence double pass as described above. Further, the light beam is configured to be incident on the scanning lens 26 at an angle in the non-scanning direction.

If the arrangement of the optical unit 10E permits, the folding mirrors 17, 20 and 28 are unnecessary.
Further, the window 32 between the cylinder mirror 30 and the photoconductor 34 can be deleted if not necessary.

The LD array 12 is the light source of the present invention, the collimator lens 14 is the first lens of the present invention, the cylinder lens 18 is the second lens of the present invention and the correcting means, and the polygon mirror 24 is the scanning of the present invention. Means, scanning lens 2
Reference numeral 6 corresponds to the second optical system of the present invention.

The optical unit 10 configured as described above
In E, the light beam emitted from the LD array 12 sequentially passes through the collimator lens 14, the aperture 16, and the expanding lens 38, is reflected by the folding mirror 17, passes through the cylinder lens 18, and is reflected by the folding mirror 20. You.

The light beam reflected by the turning mirror 20 is reflected by the polygon mirror 24 after passing through the scanning lens 26, passes through the scanning lens 26 again, is reflected by the turning mirror 28 and the cylinder mirror 30, and is reflected by the window 32. And reaches the photoreceptor 34 via.

As described above, the LD array 12 is arranged so that each light emitting point is perpendicular to the scanning direction. In the present embodiment, the scanning pitch on the photosensitive member 34 is an integral multiple of the target resolution. (See JP-A-6-109994, etc.).

The scanning of the photosensitive member 34 is started based on the timing at which the light beam is detected by the SOS sensor 49.

As described in detail above, in the optical scanning device according to the sixth embodiment, A
It is not necessary to use a deflecting means such as an OM element or the like, and since the angle of deflection of the polygon mirror is small due to the front incidence, a filter for maintaining uniformity of the light amount on the photoconductor (light amount correction filter 46, see FIG. 13) And the cost can be reduced, and the focal length becomes the combined focal length of the collimator lens, the expanding lens, and the scanning lens, so the optical magnification in the scanning direction of the pre-polygon becomes small, and heat, vibration, etc. It can also be made strong against alignment variations.

[Seventh Embodiment] The optical unit according to the seventh embodiment is the same as the optical unit 1 according to the sixth embodiment.
17, the cylinder lens is a normal cylinder lens 19 (a cylinder lens having a generatrix line) as shown in FIG. 17, and the cylinder lens of the housing 40 in which the cylinder lens 19 is installed. A concave portion 40A having a U-shape in cross section with a smaller diameter than the length of the cylinder lens 19 in the scanning direction is formed in the mounting surface of the cylinder 19, and the cylinder lens 19 is placed on the concave portion 40A of the mounting surface of the housing 40. State (state in FIG. 17)
Pressing member 5 for applying force to the upper part of cylinder lens 19 with
The only difference is that 0 is provided and that the light emitting point located at the upper end of the LD array 12 is arranged so as to substantially coincide with the optical axis of the collimator lens 14. Other configurations are the same as in the sixth embodiment,
The description here is omitted. The bus 19A of the cylinder lens 19 in FIG.
Shows a shape when a force is applied by the pressing member 50.

The housing 40 and the pressing member 50 correspond to the adjusting means of the present invention.
It corresponds to the installation member of the described invention. Further, the cylinder lens 19 corresponds to a second lens according to claim 10.

As described above, FIG. 3 corresponds to FIGS.
In the overfilled optical system shown in (1), the cylinder lens 18 is a normal one (the bus is straight).
Is applied, shows the simulation results when the bus of the cylinder lens is tilted about the optical axis, the horizontal axis represents the tilt angle of the bus of the cylinder lens,
The vertical axis indicates the beam diameter.

As described above with reference to FIG.
In order to improve the uniformity of the beam diameter, it is necessary to reverse the direction in which the cylinder lens is tilted at positive and negative positions with respect to the center in the scanning direction on the photoconductor.

The difference between FIG. 3A and FIG. 3C is the direction in which the light emitting point of the LD array is offset with respect to the optical axis of the collimator lens.

That is, FIG. 3 (C) shows an offset to the lower side, and FIG. 3 (A) shows an offset to the upper side in FIG.
17 shows a simulation result when applied to the optical systems of FIGS. 5 and 16.

As shown in FIG. 3 (C), the beam diameter in the non-scanning direction (14
8.5s), the bus of the cylinder lens is -0.4
° It becomes smaller when tilted, and the scanning direction position is -14
The beam diameter in the non-scanning direction at 8.5 mm (−148.
5s) becomes smaller when the generating line of the cylinder lens is inclined by 0.4 °.

On the other hand, as shown in FIG. 3A, the beam diameter in the non-scanning direction at a scanning direction position of 148.5 mm is:
The beam diameter in the non-scanning direction at a scanning direction position of -148.5 mm is smaller when the bus line of the cylinder lens is tilted by 0.4 °, and the beam diameter in the non-scanning direction at −148.5 mm is −0.1 mm.
It is smaller when tilted 4 °.

Similar results are obtained for the beam diameter in the scanning direction. Therefore, in order to make the beam diameter uniform, L
It turns out that it is necessary to consider the light emitting point position of the D array. Therefore, it is preferable to align one of both ends of the light emitting point of the LD array with the optical axis of the collimator lens.

Here, when the light emitting point at the upper end of the LD array is aligned with the optical axis of the collimator lens, it is offset downward, so that it is necessary that the generatrix of the cylinder lens has a downward convex R. This is effective for improving the uniformity of the diameter. In this case, as described above, a V shape having an inflection point at the center of the cylinder lens may be used.

Therefore, in the seventh embodiment, as shown in FIG. 17, only the two ends of the cylinder lens 19 are held on the installation surface of the housing 40 on which the ordinary cylinder lens 19 is installed, and the inside is not held. A force is applied from above the cylinder lens 19 to deform the generatrix so as to form a downwardly convex R-shape.

The load (force) W at this time can be obtained by the following equation (1).

W = 48 · σ · I · E / L^Three (1) Here, σ is the amount of deflection, and I is the second moment of area (=
Length in the non-scanning direction ^Three・ Thickness / 12), E is Young
And L indicates the length of the lens in the scanning direction.

For example, when the length of the cylinder lens 19 in the scanning direction is 80 mm, the length in the non-scanning direction is 7.5 mm, and the thickness is 5 mm, the Young's modulus of the lens is 7.
Since it is 3 × 10 ³ kg / mm ² , in order to incline the bus bar by 0.4 °, the force applied from above is 32 kg. In this case, the displacement amount (bending amount σ) of the central portion of the cylinder lens 18 is 0.27 mm.

The cylinder lens 19 shown in FIG. 17 is manufactured so that the generatrix position is 0.5 mm or less from the lower part of the lens. For example, when used in the optical system shown in FIGS. 15 and 16, the beam interval in the non-scanning direction at the cylinder lens 19 is 2 mm and the beam diameter is 0.8 mm. If the number of light emitting points is four, the required minimum dimension in the non-scanning direction is 6.8 mm (= (number of light emitting points−1) × 2 + 0.8). Therefore, the dimension of the lens in the non-scanning direction can be 7.3 mm. In this embodiment, since the cylinder lens 19 is mechanically deflected by applying a force, it is necessary to reduce the dimension as much as possible.

However, as can be seen from the above equation (1), if the length in the scanning direction is large, the cylinder lens can be bent with a small load even if the length in the non-scanning direction is large. If there are no restrictions on cost and space, the position of the bus may be at the center in the non-scanning direction.

By adopting such a configuration, the same effect as when using the special lens can be obtained without using a special cylinder lens for correcting the beam diameter.

By the way, the cylinder lens 19 according to the seventh embodiment is apt to be broken because a force is applied from above to make the bus bar inclined to make the beam diameter uniform.

Therefore, the cylinder lens 19 according to the seventh embodiment has been subjected to a chemical treatment to increase the toughness. The chemical processing applied in the present embodiment is as follows.
This is a process for replacing K ions and Na ions, and is performed to strengthen fragile glass.

FIG. 18A shows a state before ion exchange (before chemical treatment). Many small gaps are observed inside the glass, but after ion exchange (chemical treatment) shown in FIG. 18B. In the state of (post), it can be seen that K ions enter the glass and reduce the gap.

Therefore, the glass is strengthened by this ion exchange, partial stress concentration is reduced, and the glass is hardly broken.

As described in detail above, in the optical scanning device according to the seventh embodiment, since the bus is inclined by applying a force from above to the cylinder lens, the optical scanning device can be operated without using a special cylinder lens. The uniformity of the beam diameter can be improved at a low cost.

Further, in the optical scanning device according to the seventh embodiment, since the chemical processing is applied to the cylinder lens which is pressed and used for the purpose of equalizing the beam diameter, partial stress concentration is reduced. It is possible to reduce the number, and to avoid damage to the cylinder lens.

Although the seventh embodiment has been described with reference to the case where the cylinder lens 19 is subjected to chemical processing in order to strengthen the cylinder lens 19, the present invention is not limited to this. An embodiment in which the air cooling enhancement method is applied to the cylinder lens 19 may be adopted.

[Eighth Embodiment] In the cylinder lens correcting mechanism (see FIG. 17) described in the seventh embodiment, the force applied from the upper portion of the cylinder lens is given to the cylinder lens by changing from the concentrated weight to the distribution weight. It is desirable to reduce the brewing force to avoid breaking or partial deformation.

Accordingly, in the cylinder lens correcting mechanism according to the eighth embodiment, as shown in FIG. 19, the installation surface of the housing 40 'for installing the cylinder lens 19 is formed into an R-shape such that the generatrix of the cylinder lens 19 fits in. age,
In addition, as a pressing member disposed above the cylinder lens 19, a pressing member 50 ′ whose surface facing the upper surface of the cylinder lens 19 has a downwardly convex R shape is applied, and the pressing member 50 ′ is used to form the cylinder lens 19. The upper part is pressed to deform the cylinder lens 19.

FIG. 19 shows a state where the pressing by the pressing member 50 'is not performed. At this time, the generatrix 19A of the cylinder lens 19 is substantially horizontal to the bottom surface of the housing 40'.

The housing 40 'and the pressing member 50' correspond to the adjusting means of the present invention. In particular, the housing 40 'corresponds to the member to be installed according to the present invention.

As described in detail above, in the optical scanning device according to the eighth embodiment, the cylinder is positioned on the installation surface of the housing on which the cylinder lens is installed and on the pressing surface of the pressing member that presses the cylinder lens from above. Since the lens has a curvature corresponding to a desired generatrix shape, the shearing force applied to the cylinder lens can be reduced, and the destruction of the cylinder lens or partial deformation of the cylinder lens can be prevented.

In the eighth embodiment, the housing 4
Although the case where both the installation surface of 0 ′ and the bottom surface (pressing surface) of the pressing member 50 ′ are R-shaped has been described, the present invention is not limited to this, and one of the installation surface and the bottom surface is not limited thereto. Only the R shape may be used, and in this case, a certain effect can be expected.

[Ninth Embodiment] In the eighth embodiment,
Assuming that the cylinder lens is a normal one whose bus is not inclined, a force is applied to the cylinder lens from one side so that the bus has a downwardly convex R shape. In this case, a relatively strong force is applied to the cylinder lens. It needs to be added, and for example, even if the cylinder lens is subjected to the chemical treatment as described above, the cylinder lens may be damaged.

Therefore, in the ninth embodiment, as shown in FIG. 20, as a cylinder lens for correcting the beam diameter, a bus line 18A is formed in a downwardly convex R shape and a cylinder lens 18 made of glass mold. And the cylinder lens 18 is arranged at a predetermined position on the housing 40 'of the optical unit, and is finely adjusted so as to be substantially uniform with a desired beam diameter by pressing it with a pressing member 50'. . Therefore, it is preferable that the generating line of the cylinder lens 18 before applying a force is in the vicinity of the optimum R shape.

As described in detail above, in the optical scanning device according to the ninth embodiment, the cylinder lens used for uniformizing the beam diameter on the photosensitive member is manufactured by using a glass mold so that the generating line is inclined. In addition, since the beam is pressed by the pressing member, the beam diameter can be finely adjusted, and an error (error) in manufacturing the cylinder lens for correcting the beam diameter can be absorbed.

[Tenth Embodiment] The optical unit according to the tenth embodiment is different from the optical unit 10E according to the sixth embodiment (see FIGS. 15 and 16) in that the cylinder lens 18 for correcting the beam diameter is different. , A cylinder lens 18 ″ having two generatrixes (see FIG. 21). Therefore, the description of the configuration other than the beam diameter correcting cylinder lens is omitted.

As shown in FIG. 21A, the cylinder lens 18 ″ according to the tenth embodiment has two busbars 18A and 18B each having an inverted R shape.
The portion between the bus 18A and the bus 18B does not have a cylindrical lens shape.

In the optical system of this embodiment (see FIGS. 15 and 16), the beam diameter is 0.8 mm and the beam interval is 2 mm at the position of the cylinder lens 18 (in this embodiment, the cylinder lens 18 ″). . Therefore, the adjacent distance including the thickness of the light beam is 1.2 mm.

On the other hand, the amount of deflection of each bus (vertical from A1 to B) at the end of the area where the light beam actually passes through the cylinder lens 18 '' (expressed as "the actual use area" in FIG. 21A). Direction distance and the vertical distance from A2 to C) are 0.05 mm for both the buses 18A and 18B.
It is.

Therefore, if, for example, A1 and A2 are opened by 0.5 mm so that the center portions of the bus lines do not touch each other, the interval between B and C is 0.6 mm.

By opening the space between the generatrixes 18A and 18B in this way, it is possible to configure the optical system so that the light beam does not enter the portion of the cylinder lens 18 '' surrounded by the generatrixes 18A and 18B. .

That is, in the optical unit according to the tenth embodiment, by disposing any light emitting points of the LD array 12 so as not to pass through the optical axis of the collimator lens 14,
The beam is prevented from entering the portion of the cylinder lens surrounded by the generatrix.

Specifically, when the number of light emitting points is an even number, if the optical axis of the collimator lens 14 is aligned with the center of both ends, the optical axis and the light emitting point inevitably do not coincide with each other. The light emitting points will be placed at equal positions.

On the other hand, when the number of light emitting points is an odd number, the light emitting points located at the center are arranged upward or downward by offsetting a half of the light emitting point interval of the LD array 12.

By arranging in this way, the light beam passing through the cylinder lens 18 ″ can be separated by 0.3 mm from the portion surrounded by each bus bar.
This distance is the margin.

Table 2 shows actual measurements of the beam diameter in the scanning direction (expressed as TAN) and the beam diameter in the non-scanning direction (expressed as SAG) at the center and the end of the scanning line in the optical unit according to the tenth embodiment. It shows an example of the result,
FIG. 22 illustrates the actual measurement results shown in Table 2. As shown in Table 2 and FIG. 22, the optical unit according to the tenth embodiment can significantly improve the uniformity of the beam diameter.

[0184]

[Table 2]

With such a configuration, it is possible to cope with an LD array having more light emitting points than an optical system in which the ends of the light emitting points are aligned with the optical axis and the generatrix of the cylinder lens is bent. .

The specifications of the components constituting the optical unit according to the tenth embodiment are shown in Table 3 as an example.

[0187]

[Table 3]

In Table 3, the presence of the symbol of S or T in the item representing the radius of curvature (R) means that S means R only in the non-scanning direction and T means R only in the scanning direction.

Further, in Table 3, the cylinder lens 1
Reference numeral 8 describes only the R in the non-scanning direction, but a cylinder lens for beam diameter correction whose R is 286 mm in the scanning direction and whose R is upside down.

As described in detail above, the optical scanning device according to the tenth embodiment has two bus bars which are used for uniformizing the beam diameter on the photosensitive member. The beam diameter can be made uniform with high accuracy.

[0191]

According to the present invention, the correcting means for correcting the beam diameter of the light beam at the scanning position other than the scanning center position is arranged on the optical system between the light source and the scanning means. The uniformity of the beam diameter of the scanning line can be improved without inclining the light source with respect to the scanning direction or inclining the scanning lens in the non-scanning direction, that is, without complicating the configuration and deteriorating tilt correction. Is obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a schematic configuration of an optical unit according to a first embodiment.

FIG. 2 is an external view showing a shape of a cylinder lens for correcting a beam diameter. FIG. 2 (A) is a cylinder in which a generating line has a downwardly convex curvature with a center in the scanning direction as an inflection point. FIG. 3B is an external view showing a lens, and FIG. 4B is a cylinder lens in which the generatrix has an upwardly convex curvature having a curvature at the center in the scanning direction.

FIG. 3 is a graph showing a simulation result when a normal cylinder lens is applied to the overfilled optical system shown in FIGS. 15 and 16 and the generatrix of the cylinder lens is inclined about the optical axis; (A) shows the case where the light emitting point position is offset to the + side with respect to the optical axis of the collimator lens, and (B) shows the case where the light emitting point position is shifted to the + side with respect to the optical axis of the collimator lens (A) Offset by half the distance of
(C) shows a case where the light emitting point position is offset to the negative side with respect to the optical axis of the collimator lens, and (D) shows a case where the light emitting point position is shifted to the negative side with respect to the optical axis of the collimator lens. Are graphs each showing a case where the distance is offset by a distance of.

FIG. 4 is a diagram provided for explaining a cylinder lens according to the first embodiment, and is a schematic diagram showing a toric shape.

FIG. 5 is a schematic diagram showing the shape of an actual cylinder lens.

6A is an external view showing the shape of a cylinder lens for beam diameter correction. FIG. 6A shows a cylinder lens in which the generatrix has an inverted V-shape with the inflection point at the center in the scanning direction, and FIG. () Is an external view showing a cylinder lens having a V-shaped bus line whose inflection point is at the center in the scanning direction.

FIG. 7 is a configuration diagram illustrating a schematic configuration of an optical unit according to a second embodiment.

FIG. 8 is a schematic diagram showing how an optical path changes in the AOM element.

FIG. 9 is a configuration diagram illustrating a schematic configuration of an optical unit according to a third embodiment.

FIG. 10 is a configuration diagram illustrating a state in which a light beam is incident horizontally and parallel to a polygon mirror in the optical unit according to the third embodiment.

FIG. 11 is a configuration diagram showing a schematic configuration from a polygon mirror 24 to a cylinder mirror 30 of the optical unit according to the third embodiment.

FIG. 12 is a diagram provided for description of a fourth embodiment;
FIG. 9A is a configuration diagram illustrating a configuration of a cylinder lens of an optical unit according to a fourth embodiment, and FIG. 9B is a configuration diagram illustrating a configuration in a case where a single lens forms a cylinder lens.

FIG. 13 is a configuration diagram illustrating a schematic configuration of an optical unit according to a fifth embodiment.

FIG. 14 is a schematic diagram showing a change in a scanning position in the optical unit according to the fifth embodiment. FIG.
The light width when the light beam reaches a position 5 mm away,
(B) is the light width when the light beam reaches the center of the scanning line, and (C) is the light width when the light beam reaches 148.5 mm in the negative direction from the center. FIG.

FIG. 15 is a plan view showing a schematic configuration of an optical unit according to a sixth embodiment.

16 is a side view of the optical unit shown in FIG.

FIG. 17 is a schematic diagram illustrating a configuration around a cylinder lens according to a seventh embodiment.

FIG. 18 is a diagram provided for describing chemical processing in a seventh embodiment, in which (A) shows a state before the chemical processing;
(B) is a schematic diagram showing a state after the chemical treatment.

FIG. 19 is a schematic diagram showing a configuration around a cylinder lens according to an eighth embodiment.

FIG. 20 is a schematic diagram showing a configuration around a cylinder lens according to a ninth embodiment.

FIG. 21A is an external view showing the shape of a cylinder lens and the position of each part according to a tenth embodiment;
(B) is an enlarged view of a region A in (A).

FIG. 22 is a schematic diagram showing a state of a beam diameter on a scanning line in the tenth embodiment.

FIG. 23 is a configuration diagram showing a schematic configuration of a conventional optical unit.

24 is a schematic diagram showing an arrangement state of the LD array in FIG.

FIG. 25 is a schematic diagram showing a state of interlaced scanning of the optical unit of FIG. 23;

26 is a schematic view showing an example of a state of a beam diameter of a scanning line at each light emitting point of the LD array in the optical unit of FIG. 23.

FIG. 27 is a configuration diagram showing a schematic configuration of another conventional optical unit.

28 is a side view of the optical unit shown in FIG.

FIG. 29 is a diagram for explaining another conventional technique;
FIG. 3 is a schematic diagram illustrating an arrangement state of an LD array.

30A and 30B are diagrams for explaining a problem of the optical unit shown in FIG. 27. FIG.
(B) is the tilt correction error amount when the scan lens tilt angle is set to 8 °.
(C) is a graph showing the amount of tilt correction error when the tilt angle of the scanning lens is 12 °.

[Explanation of symbols]

 Reference Signs List 10 optical unit (optical scanning device) 12 laser diode array (light source) 14 collimator lens (first lens) 18 cylinder lens (second lens, correction means) 19 cylinder lens (second lens) 24 polygon mirror (scanning) Means) 26 scanning lens (second optical system) 34 photoreceptor 36 acousto-optic modulator (deflecting means) 38 expandable lens 40 housing (adjusting means, member to be installed) 44 cylinder lens 46 light quantity correction filter 50 pressing member (adjusting means) 90 cylinder lens (second lens) 92 cylinder lens (second lens, correction means) 94 cylinder lens (second lens) 96 separation mirror (separation means) 98 acousto-optic modulation element (deflection means)

Continued on the front page F-term (reference) 2C362 AA13 BA04 BA58 BA60 BA84 BA86 2H045 BA23 BA32 BA41 CA04 CA65 CB15 2H087 KA19 LA22 PA02 PA17 PB02 QA03 QA07 QA18 QA21 QA33 QA42 5C072 AA03 BA02 DA02 HA02 HA06 HA08 HA09 HA09 HA09 HA09

Claims (13)

[Claims] 1. A light source having a plurality of light emitting units each emitting a light beam, and a first light beam emitted from the light source is converted into substantially parallel light.
A first optical system including a first lens and a second lens having power only in a direction intersecting the scanning direction of the light beam; and scanning the light beam emitted from the first optical system. A scanning unit, a correction unit disposed on an optical system between the light source and the scanning unit, and for correcting a beam diameter of the light beam at a scanning position other than the scanning center position; A second optical system that scans the light beam with the light beam and focuses the light beam on the surface to be scanned. 2. The optical scanning device according to claim 1, wherein the correction unit is a cylinder lens whose generating line has a curvature or an inclination in a direction intersecting a scanning direction of the light beam. 3. The apparatus according to claim 1, further comprising a deflecting unit between the light source and the correcting unit, the deflecting unit deflecting an optical path of the light beam in a direction crossing an optical axis. Optical scanning device. 4. The optical scanning device according to claim 3, further comprising a separating unit configured to change a traveling direction of a light beam emitted from each of the plurality of light emitting units of the light source. 5. The cylinder lens is composed of a plurality of lenses, and at least one lens has a curvature or an inclination in a direction intersecting a scanning direction of the light beam. Claims 2 to 4
The optical scanning device according to claim 1. 6. The optical scanning device according to claim 1, wherein the optical system is an overfilled optical system. 7. The optical system according to claim 1, wherein the light beam is incident on the second optical system at substantially an angle, in a double path and in a direction intersecting the scanning direction of the light beam. Item 7. The optical scanning device according to Item 6. 8. The optical scanning device according to claim 2, wherein the cylinder lens is made of a resin or a glass mold part. 9. The optical scanning device according to claim 8, wherein the cylinder lens has a plurality of generating lines. 10. A light source having a plurality of light-emitting portions that are linearly arranged and emit light beams, respectively, and a light-emitting portion on one end side of the plurality of light-emitting portions of the light source is disposed so that an optical axis thereof substantially coincides with the light source. A first optical system including a first lens that converts the light beam emitted from the light source into substantially parallel light, and a second lens that has power only in a direction intersecting the scanning direction of the light beam; Adjusting means for adjusting the generatrix of the second lens so as to have a curvature or inclination in a direction intersecting the scanning direction of the light beam; and scanning for scanning the light beam emitted from the first optical system. An optical scanning device comprising: means; and a second optical system that scans the light beam on the surface to be scanned at a substantially constant speed and condenses the light beam on the surface to be scanned. 11. The adjusting means includes a member on which the second lens is installed and a pressing member for pressing the second lens against the member to be installed. The at least one of a surface and a pressing surface of the pressing member has a curvature.
The optical scanning device according to claim 1. 12. The optical scanning device according to claim 10, wherein the second lens has been subjected to chemical processing. 13. The apparatus according to claim 1, wherein the second lens is made of a resin or glass mold part.
The optical scanning device according to any one of claims 0 to 12.