JPH1172732A - Optical scanning device - Google Patents

Abstract

(57) Abstract: An object of the present invention is to reduce an image height error due to a manufacturing error or an arrangement error of a lens, that is, to reduce and correct printing distortion. SOLUTION: In the optical scanning device, a two-element Fθ lens composed of a first lens having a negative refractive power and a second lens having a positive refractive power, wherein the second lens is used for adjustment. It can rotate around an axis perpendicular to the light scanning plane,
A lens adjusting device for fixing the position of the second lens after the adjustment is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device used for a laser beam printer, a copying device, and the like, and more particularly to an optical scanning device having a function of correcting a scanning position shift in an optical scanning direction.

[0002]

2. Description of the Related Art FIG. 2 shows a schematic view of a conventional laser beam printer. Light is generated from a light source 1, and the light is collimated by a collimator lens 2. Thereafter, the light passes through a cylinder lens 3 inserted for correcting surface tilt, and is deflected and scanned by a rotating polygon mirror 4. After that, it is narrowed down on the photoreceptor 8 by the Fθ lens including the first lens 5 and the second lens 6. Between the second lens 6 and the photoreceptor 8, a folding mirror 7 for folding light is provided.

Conventionally, the second lens 6 is fixed,
The placement accuracy depends on the processing accuracy of the base on which the second lens 6 is mounted. Further, a processing error of the second lens 6 directly leads to an arrangement error of the second lens. Second lens 6
If these arrangement errors are present, defective printing results will occur. Since a lens having an arrangement error exceeding a predetermined size is unusable, the yield is deteriorated and the cost of the lens is increased. This is related to the price of the entire apparatus, which is a problem.

[0004]

A description will now be given of the phenomenon of a defective printing result due to the above arrangement error.

As shown in FIG. 3, a case is considered in which a square grid-like printing pattern 14 is written on the printing paper 12 having the paper transport holes 13. A, B, C, and D in FIG. 3 are positions where the vertical lines of the grid are written. If the print data is a correct square grid pattern, it matches the square grid pattern 14 printed correctly as shown in FIG.
The displacement of C and D becomes zero. The amount of displacement from the reference position is called an image height error. Actually, an optical scanning device using an Fθ lens having an image height error as shown in FIG. 4 due to the aberration of the Fθ lens or the like has been commercialized, but ± 0.15 m
If the image height error is suppressed within m, there is no problem in practical use.
This Fθ lens is shown in FIGS. FIG. 5 is a diagram of the scanning surface viewed from above, and FIG. 6 is a diagram of the scanning surface viewed from the side. The Fθ lens has a configuration of a first lens 5 and a second lens 6. However, errors due to lens arrangement errors and lens manufacturing errors occur, making it difficult to arrange lenses according to ideal design values as shown in FIGS. For example, as shown in FIG. 7, the correct second lens 6 has a manufacturing error even though the intersection of the parallel line 16 with the flat surface and the perpendicular 17 extending from the contact point of the curved surface and the flat surface is perpendicular. As a result, the angle 18 may not be a right angle as shown in FIG. In addition, as shown in FIG. 9, when the plane portion of the lens is arranged by the pins 19, 20, and 21, and when the optical axis 22 is centered, it is assumed that FIG.
As shown by 0, due to the placement error of the pins 19, 20, and 21,
In some cases, the optical axis 22 and the second lens 6 are arranged at an angle.

FIG. 11 shows the image height error at this time. FIG.
In FIG. 1, calculation is shown for a case where the second lens 6 is inclined by 0.3 degrees about an axis perpendicular to the optical scanning surface. At minus scanning angle of view, it is within ± 0.15,
At a plus scanning angle of view, a point of ± 0.3 is coming out. In other words, at this time, as shown in FIG.
On the printing paper 12 with a square grid pattern 1
When 4 is printed, the result is as shown in FIG. In this case, the abnormal interval becomes narrow and printing is distorted. The Fθ lens that performs such printing has been discarded as defective.
For this reason, the lens manufacturing price has risen, which has been a problem.

[0007]

According to the present invention, at least one light beam generating means capable of modulating light intensity and a light beam emitted from the light generating means are deflected and scanned. An optical scanning device having a rotating polygonal mirror and a two-element Fθ lens including a first lens having a negative refractive power and a second lens having a positive refractive power.
A lens adjusting device for rotating the lens about an axis perpendicular to the optical scanning surface for adjustment, and fixing the position of the second lens after the adjustment is provided, and the second lens is mounted on the lens adjusting device.

[0008]

FIG. 1 shows an embodiment of the present invention. Light is generated from a light source 1, and the light is collimated by a collimator lens 2. Thereafter, the light passes through a cylinder lens 3 inserted for correcting surface tilt, and is deflected and scanned by a rotating polygon mirror 4. After that, it is narrowed down on the photoreceptor 8 by the Fθ lens including the first lens 5 and the second lens 6. In the figure, only the center light is shown for simplicity. At this time, the second lens 6 is mounted on a lens adjusting device comprising a rotatable table 9 and can be rotated and adjusted to an arbitrary position on a scanning plane by a gear 10 rotated by a motor 11. .

For this reason, a manufacturing error of the second lens 6 and
8 or 10 due to the arrangement error of the second lens 6.
And the printing is as shown in FIG. 12,
Printing can be performed as shown in FIG. 3 by adjusting the rotation of the turntable 9 while observing the printing result and fixing the same. The image height error at this time is initially as shown in FIG. 11, but is appropriately corrected as shown in FIG. Details of the Fθ lens system used in this study are shown in FIGS. This adjustment may be performed manually without using a motor and fixed after adjustment.

As another embodiment of the lens adjusting device for the second lens 6, in addition to the example shown in FIG.
The inclination of the second lens 6 may be adjusted using the cams 23 and 24 as described above. In addition, as shown in FIGS. 15 and 16, the second lens 6 may be adjusted using the screws 27 and 30 using the supporting parts 25 and 28 having the elongated holes 26 and 29, and then fixed by a fixing device (not shown). .

[0011]

As described above, according to the present invention, it is possible to correct an image height error defect due to a manufacturing error of the Fθ lens, that is, a distortion of printing, which has been defective until now. The defective rate of the lens can be reduced. Therefore, the cost of the optical scanning device can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of the present invention.

FIG. 2 is a schematic diagram of a conventional optical scanning device.

FIG. 3 is a diagram showing a printing example of a lattice pattern.

FIG. 4 is a diagram showing a normal image height error.

FIG. 5 is a schematic diagram showing an Fθ lens system.

FIG. 6 is a schematic diagram showing an Fθ lens system.

FIG. 7 is a schematic diagram of an ideal second lens.

FIG. 8 is a schematic diagram of a second lens having a manufacturing error.

FIG. 9 is a schematic diagram showing an ideal arrangement of a second lens.

FIG. 10 is a schematic diagram showing an arrangement of a second lens having an arrangement error.

FIG. 11 is a diagram showing an image height error when there is an arrangement error in the second lens.

FIG. 12 is a diagram illustrating a printing example of a lattice pattern when there is an arrangement error in the second lens.

FIG. 13 is a schematic view showing an embodiment of the present invention.

FIG. 14 is a schematic view showing an embodiment of the present invention.

FIG. 15 is a schematic view showing an embodiment of the present invention.

FIG. 16 is a schematic diagram showing an example of the present invention.

[Explanation of symbols]

1. Light source such as laser 2. Collimator lens
3 ... Cylinder lens, 4 ... Rotating polygon mirror, 5 ... First
No., 6 ... Second lens, 7 ... Folded mirror, 8 ... Photoconductor, 9 ... Turntable, 10 ... Gear, 11
... Motor, 12 ... Printing paper, 13 ... Paper transport hole, 14 ... Square grid printing pattern, 15 ... Long cylindrical lens, 16 ... Tangent, 17
... perpendicular to the curved surface, 18 ... angle, 19, 20, 21 ...
Pin, 22 ... Optical axis, 23, 24 ... Cam, 25, 28
... Supporting parts, 26, 29 ... Long holes, 27, 30 ... Screws.

Claims (1)

[Claims] At least one light beam generating means capable of modulating light intensity, a rotary polygon mirror for deflecting and scanning the light beam emitted from the light generating means, and a first light beam having a negative refractive power
In an optical scanning device having a two-element Fθ lens composed of a lens having a positive refractive power and a second lens having a positive refractive power, the second lens is rotated in a scanning plane about an axis perpendicular to the optical scanning surface. An optical scanning device provided with a lens adjusting device for fixing the lens at an arbitrary position after adjustment.