JPH10325931A - Adjusting method for multibeam scanning optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily adjust an actual distance between scanning lines without complicating the structure. SOLUTION: Plural light beams with information carried are emitted from a semiconductor laser light source 11, and simultaneously, the image is formed on a moving surface 18a to be scanned. The moving velocity V of the surface 18a is adjusted in accordance with the distance between plural light beams. In the case of emitting two light beams from the light source 11, the moving velocity V is changed so as to be P1/P2 (Provided that P1 denotes the actual distance between these beams on the surface 18a and P2 denotes a theoretical distance calculated based on the resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an image forming apparatus such as a laser printer or a digital copying machine utilizing an electrophotographic process, and deflects a plurality of light beams from a light source by a deflecting means to form a photosensitive member. The present invention relates to a method for adjusting a multi-beam scanning optical system for simultaneously forming an image on a surface.

[0002]

2. Description of the Related Art In many conventional scanning optical devices, a light beam modulated according to an image signal is emitted from a semiconductor laser light source, and is periodically deflected and rotated by a polygon mirror which is rotated by the driving force of a driving motor. F on the surface of the photosensitive drum
Information is recorded on the surface of the photosensitive drum by forming an image in the form of a spot via an imaging lens having the θ characteristic.

In recent years, as the demand for higher speed and higher definition of this type of scanning optical device has been increased, attempts have been made to increase the rotational speed of a drive motor and the number of polygon mirror surfaces. In addition, since there is a limit to increasing the number of rotations of the drive motor and the number of surfaces of the polygon mirror, it has been proposed that a plurality of light beams be simultaneously emitted from the light source to cope with high speed and high definition. ing.

In a scanning optical device that simultaneously emits a plurality of light beams from a light source, as shown in FIGS.
The two light beams which have been independently modulated from the light beam are converted into parallel light beams by the collimator lens 2 and the light beams
Thus, the outer shape is restricted and the light enters the cylindrical lens 4. In the cylindrical lens 4, the light beam in the main scanning direction is transmitted as it is, and the light beam in the sub-scanning direction is condensed and incident on the polygon mirror 5 a of the deflector 5 as a substantially linear image. The deflector 5 deflects two light beams, and these light beams are condensed by an imaging lens 6 having fθ characteristics, and form an image on a scanning surface 7 a of a photosensitive drum 7. When the polygon mirror 5a rotates in the direction of the arrow, the light beam scans on the surface 7a to be scanned.

At this time, the actual interval P1 of the scanning lines in the sub-scanning direction on the surface 7a to be scanned is the theoretical interval P2 = 2 when interlacing, that is, interlaced scanning is not performed.
5.4 / resolution (dpi) mm. For this reason, when the actual interval P1 is shifted by 1/10 or more of the theoretical interval P2, the pitch unevenness of the scanning lines becomes noticeable.

In order to eliminate the scanning line pitch unevenness, it is necessary to accurately adjust the actual interval P1. The actual interval P1, the interval d between the two light emitting points of the light source 1, the sub-scanning direction, Since the equation of P1 = β × d holds between the horizontal magnification β and the horizontal magnification β, one of the horizontal magnification β and the light emitting point interval d may be adjusted.

A method for adjusting the distance d between the light emitting points is disclosed in, for example, Japanese Patent Publication No. Sho 60-33019. Here, the distance d between the light emitting points is adjusted by rotating the light source 1, and the lateral magnification β is adjusted by moving the cylindrical lens 4.

[0008]

However, in the above-mentioned conventional example, in order to adjust the actual distance P1, it is necessary to rotate the light source 1 or move the cylindrical lens 4, so that the mechanism is complicated. There is a problem that manufacturing costs increase.

In view of these problems, an object of the present invention is to provide
An object of the present invention is to provide a method for adjusting a multi-beam scanning optical system that can easily adjust the actual interval between scanning lines without complicating the structure.

[0010]

According to the present invention, there is provided a method for adjusting a multi-beam scanning optical system, comprising:
A method for adjusting a multi-beam scanning optical system that emits a plurality of light beams carrying information from a light source and simultaneously forms an image on a moving surface to be scanned, comprising: It is characterized in that it is adjusted according to the interval.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a schematic plan view showing a first embodiment together with an optical path in the main scanning direction, and FIG. 2 is a schematic side view also showing an optical path in the sub-scanning direction, for example, a semiconductor emitting two light beams. A laser light source 11 is provided. In the traveling direction of the light beam emitted from the laser light source 11, a collimator lens 12 for converting the light beam into parallel light, an aperture 1 for limiting the outer shape and light amount of the light beam
3. A cylindrical lens 14 having a refractive power only in the sub-scanning direction, and a polygon mirror 15a of a deflector 15 for deflecting the light beam are sequentially arranged. Polygon mirror 1
In the traveling direction of the light beam deflected by 5a, an imaging lens 16 having fθ characteristics, a long cylindrical lens 17 having refractive power only in the sub-scanning direction, and a photosensitive drum 18 on which a spot image is formed by the light beam are formed. Scanned surface 18
a are sequentially arranged.

The laser light source 11 emits light beams modulated individually in accordance with image information, and the polygon mirror 15a is driven to rotate at a constant speed by a drive motor (not shown). The photosensitive drum 18 is driven to rotate in a direction indicated by an arrow at a predetermined rotation speed V by driving means (not shown).

The standard resolution of the scanning line in the sub-scanning direction on the scanned surface 18a is 600 dpi, and the standard rotation speed at this resolution is VO. The actual interval between the scanning lines on the scanned surface 18a in the sub-scanning direction is P1, and the theoretical interval is
When P2, the theoretical interval P2 is 25.4 mm (1 inch) /600=42.3 μm, and the rotation speed V is VO ×
P1 / P2 = VO × P1 / 42.3, and P1 = 42.3 × V /
Become VO.

In the initial adjustment process in the production at the factory, the actual interval P1 is measured. When the actual interval P1 between the scanning lines A and B is smaller than the theoretical interval P2 as shown in FIG. As shown in FIG. 4, the rotation speed V is reduced so that the actual interval P1 between the scanning lines A and B is equalized.

If the actual interval P1 between the scanning lines A and B is wider than the theoretical interval P2 as shown in FIG.
The rotation speed V is increased so that the actual interval P1 between the scanning lines A and B is equalized as shown in FIG.

In the scanning optical device configured as described above,
The two light beams emitted from the laser light source 11 are converted into parallel light by a collimator lens 12 and
The amount of light is limited by the polygon mirror 1 and converged only in the sub-scanning direction by the cylindrical lens 14.
An image is formed on the reflection surface 5a. At this time, the polygon mirror 1
The light beam incident on 5a becomes a line image having a length in the main scanning direction, and this light beam is deflected by the rotation of the polygon mirror 15a.

2 deflected by the polygon mirror 15a
The light beam is transmitted through the fθ lens 16 and transmitted through the long cylindrical lens 17, so that
An image is formed in a spot shape at 8. At this time, the inclination of the reflection surface of the polygon mirror 15a is caused by the cylindrical lens 14 and f
is corrected by the θ lens 16.

The actual interval P1 between the two light beams
Are adjusted at equal intervals by changing the rotation speed V of the photosensitive drum 18, so that the light beam scans the scanning surface 18a at equal intervals and at the same speed by the long cylindrical lens 17.

In the first embodiment, the actual distance P1 between the two light beams can be adjusted only by changing the rotation speed V of the photosensitive drum 18, and the actual distance P1 between the scanning lines can be adjusted without complicating the structure. P1 can be easily adjusted. Therefore, when used in an image forming apparatus, high-quality images with little pitch unevenness can be realized easily and inexpensively.

Since most of the actual displacement of the interval P1 is caused by a manufacturing error in the interval between the light emitting points, the first embodiment uses an image forming relationship in the sub-scanning direction as a reduction system. For this reason, the displacement amount in the sub-scanning direction is about ± 0.5%, which is an acceptable level.

FIG. 7 is a schematic plan view of the second embodiment showing the optical path in the main scanning direction, and FIG. 8 is a schematic side view showing the optical path in the sub-scanning direction. A single lens 19 is provided instead of the lens 16 and the long cylindrical lens 17, and the image forming relationship in the sub-scanning direction is an enlargement system. Further, since the imaging relationship in the sub-scanning direction is an enlarged system, the influence of the manufacturing error of the interval between the light emitting points on the actual interval P1 increases, and the amount of change in the rotational speed V of the photosensitive drum 18 also increases. The expansion and contraction of the image due to the change in the rotation speed V is prevented by companding the image information in the rotation direction. The change in the exposure amount due to the expansion and contraction of the image information is prevented by adjusting the light emission amount of the laser light source 11.

In the first embodiment, the same effects as those of the first embodiment can be obtained, and further, the change in the image density due to the expansion and contraction of the image in the sub-scanning direction and the change in the exposure amount can be eliminated. .

[0023]

As described above, the method for adjusting the multi-beam scanning optical system according to the present invention adjusts the moving speed of the surface to be scanned in accordance with the interval between a plurality of light beams, thereby complicating the structure. And the actual spacing of the scanning lines can be easily adjusted.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a first embodiment showing an optical path in a main scanning direction.

FIG. 2 is a schematic side view showing an optical path in a sub-scanning direction.

FIG. 3 is an explanatory diagram in the case where the interval between scanning lines is narrow.

FIG. 4 is an explanatory diagram showing a state in which the intervals between scanning lines are equal.

FIG. 5 is an explanatory diagram in the case where the interval between scanning lines is wide.

FIG. 6 is an explanatory diagram of a state in which intervals between scanning lines are equal.

FIG. 7 is a schematic plan view of a second embodiment showing an optical path in the main scanning line direction.

FIG. 8 is a schematic side view showing an optical path in the sub-scanning direction.

FIG. 9 is a perspective view of a conventional example.

FIG. 10 is a schematic side view showing a conventional optical path in the sub-scanning direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Semiconductor laser light source 15 Deflector 15a Polygon mirror 16 fθ lens 17, 19 Cylindrical lens 18 Photosensitive drum 18a Scanned surface P1 Actual interval P2 Theoretical interval

Claims (7)

[Claims] 1. A method of adjusting a multi-beam scanning optical system for emitting a plurality of light beams carrying information from a light source and simultaneously forming an image on a moving surface to be scanned. An adjustment method for a multi-beam scanning optical system, wherein the adjustment is performed according to an interval between a plurality of light beams. 2. The method for adjusting a multi-beam scanning optical system according to claim 1, wherein said light source is a multi-beam laser element comprising a single laser chip. 3. The light source emits two light beams,
When the interval between these light beams on the surface to be scanned is P1, and the theoretical interval calculated from the resolution is P2,
2. The moving speed of the scanned surface is changed to P1 / P2.
Or the adjusting method of the multi-beam scanning optical system according to 2. 4. The adjustment method of a multi-beam scanning optical system according to claim 1, wherein the surface to be scanned is a surface of a photosensitive drum coated with a photosensitive substance. 5. The method for adjusting a multi-beam scanning optical system according to claim 1, wherein the surface to be scanned is a surface of a photosensitive belt coated with a photosensitive substance. 6. The method for adjusting a multi-beam scanning optical system according to claim 1, wherein an amount of light emitted from the light source is adjusted according to a moving speed of the surface to be scanned. 7. The multi-beam scanning optical system according to claim 1, wherein information on a moving direction of the surface to be scanned carried by the light source is stretched to adjust a magnification. Adjustment method.