KR20000007639A - Laser scanning apparatus - Google Patents

Abstract

PURPOSE: A laser scanning apparatus is to decrease a manufacturing cost of a lens and simplify a layout, and be easy a design of a printer. CONSTITUTION: A laser scanning apparatus comprises: a first scanning lens (11) having an index of refraction in only main scanning direction; a second scanning lens (12) having an index of refraction in sub-scanning direction and the main scanning directions, wherein the second scanning lens (12) has a first surface with a cylinder type in the sub-scanning direction and a second surface with a cylinder type in the main scanning direction; and a first lens (13) having an index of refraction in only sub-scanning direction, wherein the first scanning lens (11) has a material with a low index of refraction and the second scanning lens (12) has a material with a high index of refraction.

Description

Gwangju Yarn Equipment

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light scanning device, and more particularly, to a light scanning device that can simplify the configuration of a scanning optical system, thereby lowering the processing cost of a lens and simplifying the layout of a unit, thereby facilitating the design of a printer.

In general, the optical device is equipped with a laser diode (1) consisting of a light source as shown in FIG. The laser diode 1 emits a beam toward the collimating lens 2 and is parallel in the direction of the horizontal main scanning direction and the vertical sub-scanning direction while passing through the collimating lens 2. Made of beam The parallel beam passes only the central portion of the beam while passing through the slit 3 having a rectangular hole in the main scanning direction, and then converges in the sub-scanning direction in the cylindrical lens 4.

The beam converged in the sub-scanning direction is reflected at a rotation angle mirror 5 which is rotated at a high speed with a constant angle of view and exits to the scanning lens system 6 which is an f-? Lens. The scanning lens system 6 is composed of two scanning lenses 6a and 6b, and converges the incident beam in the main scanning direction and emits it to the photosensitive drum. The emitted beam converges in the main scanning direction in the state of convergence in the sub-scanning direction, thereby forming a focus when incident on the photosensitive drum.

The Gwangju scanning device configured as described above changes the main and sub-injectors into parallel beams while passing through the collimating lens 2 through the collimating lens 2, and then passes through the slit 3 and the cylindrical lens 4. The beam in the scanning direction converges. The beam converged in the sub-scanning direction is scanned into the photosensitive drum with a constant angle of view in the rotating face mirror 5. Before the beam is scanned into the photosensitive drum, the main scanning direction is converged by the scanning lens system 6, and when the beam is incident on the photosensitive drum, a focus is formed and a desired image is obtained.

Conventional scanning lens systems require different imaging characteristics in the sub-scan direction and the main scan direction, and adopt a toric lens surface having different refractive power in the main scanning direction and refractive power in the sub-scan direction. However, the toric lens surface is difficult to manufacture and difficult to process and inspection.

SUMMARY OF THE INVENTION The present invention was developed in view of the conventional problems, and an object of the present invention is to provide a optical scanning device capable of simplifying the scanning lens system constituting the scanning optical system to lower the processing cost of the lens and simplify the layout of the unit.

1 is a plan view of a conventional optical scanning device,

2 is a plan view and a front sectional view of the scanning lens system of the present invention;

Fig. 3 is a diagram showing the top curvature and the f · θ characteristics of the first embodiment of the present invention;

4 is a top view curvature and f θ characteristics of the second embodiment of the present invention,

Fig. 5 is a diagram showing top curvature and f · θ characteristics of a third embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

1: laser diode 2: collimating lens

3: slit 4: cylinder lens

5: Rotating polygon mirror 10: Scanning lens system

11: first scanning lens 12: second scanning lens

13: first mirror

In order to achieve the above object, the present invention makes the light beam emitted from the laser diode into parallel light by the collimating lens, and passes the long rectangular slit in the main scanning direction, and then the long axis in the main scanning direction by the cylindrical lens. The optical scanning device having a long elliptic beam having an incidence / reflection on a rotating polyhedron and then incident on a scanning lens system to form a constant velocity scan, wherein the scanning lens system has a first scanning lens and a sub-scanning having refractive power only in the main scanning direction. And a second scanning lens having refractive power only in each of the direction and the main scanning direction, and a first mirror having refractive power only in the sub-scanning direction.

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

2 is a plan view and a front sectional view of the scanning lens system of the present invention, in which the same components as in FIG. 1 will be described with the same reference numerals. The luminous flux emitted from the light source portion composed of the laser diode 1 or the like becomes a substantially parallel luminous flux by the collimating lens 2, and passes through an elliptical or rectangular slit 3 having a long axis in the main scanning direction, and the sub-scanning. It passes through the cylindrical lens 4 having refractive power in the direction. The light beam passing through the cylindrical lens 4 becomes a long linear image in the main scanning direction and is incident on the rotating multifaceted mirror 5.

The beam reflected by the rotating polygon mirror 5 is incident on the scanning lens system 10. At this time, the angle of incidence of the beam into the multi-facet mirror varies according to the rotation of the multi-facet mirror 5, and the reflected beam scans the scan surface such as the persimmon drum as the rotation of the multi-facet mirror. Reflected beam deflected by the rotation of the multi-facet mirror after reflection from the multi-faceted mirror is incident to the scanning lens system 10 and is imaged through the scanning lens system 10 to form a constant velocity scan image by the action of the scanning lens system.

In addition, in order to reduce the pitch error of the print image in the sub-scanning direction, it is common to design the reflective surface and the scanned surface of the rotating multifaceted mirror 5 in an optical conjugated relationship. Therefore, the action of the lens to form a balanced beam in the main scanning direction reflected from the multi-facet mirror and the action of the lens to form a diverging beam in the sub-scanning direction are different.

In the present invention, in order to achieve the optical conjugated relationship between the multi-facet mirror surface and the target surface in the sub-scanning direction, the first scanning lens 11 having the refractive power only in the main scanning direction, the sub-scanning direction, and the main scanning direction A second scanning lens 12 having refractive power only for each of them and a first mirror 13 having refractive power only for the sub-scanning direction.

Further, the first surface of the first scanning lens is concave toward the rotating polygonal mirror, and the second surface of the first scanning lens is concave toward the rotating polygonal mirror. In addition, the second surface of the first scanning lens may be configured to have a convex shape toward the rotating polygon mirror. In addition, the second scanning lens has a cylindrical shape in the first scanning direction in the sub-scanning direction, the second surface is a cylindrical shape in the main scanning direction, the first scanning lens is composed of a low refractive index material, and the second scanning lens has a high refractive index. It is formed of the material of the upper surface curvature becomes easy.

According to the present invention configured as described above, the surfaces of the scanning lens system are simply configured. The first scanning lens 11 has refractive power only in the main scanning direction, and the second scanning lens 12 has refractive power in each of the sub scanning direction and the main scanning direction. In order to correct the first scanning lens 11, the present invention consists of a first mirror 13 having refractive power in the sub-scanning direction, so that the exemption is easy.

Design data according to the present invention is shown in the following table.

Example 1 Scanning lens shape Wavelength 786.5 nm if R (mm) r (mm) d (mm) n (refractive index) Rotating Polygon Incident Angle (α) 60.0 DEG. One -51.31 - 20 1.511049 Maximum deflection angle (θ) ± 45.3 DEG. 2 -51.31 - 10 - Scanning lens focal length (f) 200.0mm 3 ∞ -55 20.4 1.755 Deflection point shot surface (L) 274.0mm 4 -177.17 ∞ 16 - 5 ∞ -141.16 207.6 First mirror R: radius of curvature in the main scan direction, r: radius of curvature in the main scan direction

Example 2 Scanning lens shape Wavelength 786.5 nm if R (mm) r (mm) d (mm) n (refractive index) Rotating Polygon Incident Angle (α) 60.0 DEG. One -54.77 - 25 1.511049 Maximum deflection angle (θ) ± 45.3 DEG. 2 -54.77 - 10 - Scanning lens focal length (f) 200.0mm 3 ∞ -26.31 23 1.685 Deflection point shot surface (L) 281.0mm 4 -157.27 ∞ 16 - 5 ∞ -135.37 207 First mirror R: radius of curvature in the main scan direction, r: radius of curvature in the main scan direction

Example 3 Scanning lens shape Wavelength 786.5 nm if R (mm) r (mm) d (mm) n (refractive index) Rotating Polygon Incident Angle (α) 60.0 DEG. One -635.59 - 20 1.511049 Maximum deflection angle (θ) ± 45.3 DEG. 2 +635.59 - 6 - Scanning lens focal length (f) 200.0mm 3 ∞ -50 22.6 1.632 Deflection point shot surface (L) 276.2 mm 4 -100.54 ∞ 17.9 - 5 ∞ -146.66 209.7 First mirror R: radius of curvature in the main scan direction, r: radius of curvature in the main scan direction

As described above, according to the present invention, the first scanning lens constituting the scanning lens system has refractive power only in the main scanning direction, and the second scanning lens has refractive power in the scanning and sub-scanning directions, respectively. A first mirror having refractive power in the sub-scanning direction is provided for correction. Therefore, the surface shape of the lens is simplified, so that it is easy to process and can be provided at low cost to laser printers and multi-function printers.

Claims (6)

If the light beam emitted from the laser diode is converted into parallel light by the collimating lens, passed through a long rectangular slit in the main scanning direction, and then rotated by a long elliptic beam having a long axis in the main scanning direction by the cylindrical lens In the optical scanning device which is incident / reflected on the mirror and incident on the scanning lens system to form a constant velocity scan, The scanning lens system may include a first scanning lens having refractive power only in the main scanning direction, A second scanning lens having refractive power only in each of the sub scanning direction and the main scanning direction, and An optical scanning device comprising a first mirror having refractive power only in the sub-scanning direction. The optical scanning device of claim 1, wherein the second scanning lens has a cylindrical shape in a first scanning direction and a cylindrical shape in a second scanning direction. The optical scanning device of claim 1, wherein the first surface of the first scanning lens is concave toward the rotating polygon mirror. The optical scanning device of claim 1, wherein the second surface of the first scanning lens is concave toward the rotating polygon mirror. The optical scanning device of claim 1, wherein the second surface of the first scanning lens is convex toward the rotating polygon mirror. The optical scanning device of claim 1, wherein the first scanning lens is formed of a material having a low refractive index and the second scanning lens is formed of a material having a high refractive index to enable image curvature correction.