JPH0248630A - optical scanning device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (4! Field of Industrial Application) The present invention relates to an optical scanning device, and particularly to an optical scanning device that uses a plurality of laser beams to optically scan a surface to be scanned, which is each image carrier. For example, the present invention relates to an optical scanning device suitable for devices such as color laser beam printers and multicolor laser beam printers having an electrophotographic process.

(Conventional technology) Color laser beam printers (color LB)
In an optical scanning device such as P), a plurality of laser beams are used to optically scan the surface of an image carrier to read and read images.

Figure 3 is a schematic diagram of the main parts of a conventional optical scanning device, and Figure 4 is a w4
3 is a partially enlarged view, and FIG. 5 is a @ side view of FIG. 4.

In Figures 3 to 5, the two laser beams emitted from the two light emitting III m+ and at are collimated by the collimator lens 5 with a focal length f5, and after passing through the aperture 2, the refractive power is adjusted in the direction perpendicular to the plane of the paper. The cylindrical lens 6 focuses the light onto one reflecting surface 4a of the rotating polygon mirror 4 so as to form a focal line. The two laser beams from the reflecting surface 4a are then passed through two lenses 7.8 having t-e characteristics.
The light is guided onto the surface to be scanned 9 by a scanning lens 31 consisting of the following. The surface to be scanned 9 is optically scanned by rotating the rotating polygon mirror 4 in the direction of the arrow around the rotation axis 4a.

In the optical scanning device shown in the figure, two laser beams emitted from the semiconductor laser emitted i1 a I ) a t exit the aperture 2 at an angle of 0 with respect to the optical axis.

The distance el from the main plane H° of the collimator lens 5 on the optical deflector side to the second lens surface 6b of the cylindrical lens 6, and the reflective surface 4a of the rotating polygon mirror 4 from the second lens surface 6b.
Letting the distance to 82 be given by the principal ray interval clc on the reflecting surface 4a of the rotating polygon mirror 4.

In general, in view of the bending of each scanning line of a plurality of laser beams on the scanned surface 9, the curvature of field, etc., it is better that the principal ray interval on the reflective surface be as narrow as possible.

For example, it is recommended that the spacing be approximately 173 mm compared to the conventional spacing.

(I!!1 Problem to be Solved by the Invention) The present invention guides a plurality of laser beams onto the reflecting surface of a rotating polygon mirror using optical means consisting of a collimator lens, a cylindrical lens, etc. When optically scanning a surface to be scanned with a laser beam of An object of the present invention is to provide an optical scanning device which has good optical performance by reducing the beam interval of a plurality of laser beams in order to reduce the size of the entire device and reduce the bending of the scanning line and the curvature of the document on the surface to be scanned. purpose.

(Means for solving the problem) A plurality of laser beams emitted from a plurality of light emitting parts are guided to an optical deflector consisting of a rotating polygon mirror through an optical means, and the reflected beam from the optical deflector 1 is - When light is guided onto the surface to be scanned and scanned by a scanning lens having characteristics, the optical means reduces the distance between the light emitting part and the optical deflector, and/or reduces the reflection of the optical deflector. 1I of the plurality of light emitting points on the surface
It has an optical function of reducing the fI interval.

Particularly, in the present invention, the optical means includes a collimator lens and a cylindrical lens in order from the plurality of light emitting parts, and the collimator lens has a main plane H' on the optical deflector side that emits the light of the collimator lens. The cylindrical lens is configured to be located closer to the optical deflector than the lens surface on the deflector side, and the cylindrical lens is characterized in that both surfaces are configured with surfaces with refractive power directed in the same direction.

(Embodiment) FIG. 1 is a schematic diagram of a main part of an embodiment of the present invention, and FIG. 17 is a sectional view of FIG. 1.

In this example, two light emissions ma+ of the semiconductor laser,
The two laser beams emitted from a* are turned into two parallel beams mI+m# by the collimator lens l, and after passing through the aperture 2, are incident on the cylindrical lens 3 whose both surfaces have their refractive powers directed in the same direction.

Note that the collimator lens 1 and the cylindrical lens 3 constitute a part of the optical means. Then, the two laser beams are focused by a cylindrical lens 3 onto a reflecting surface 4a of a rotating polygon mirror 4 serving as an optical deflector so as to form a focal line in a direction perpendicular to the rotational axis direction. The two reflected laser beams are guided to the surface to be scanned by a scanning lens having f-0 characteristics as shown in FIG. 3, and the surface to be scanned is scanned by rotating the rotating polygon mirror 4. ing.

The collimator lens l in this embodiment is a light deflector 'a4
Optical quality values such as the radius of curvature, thickness, and shape of the lens surface are set so that the side 1t plane H° is located closer to the optical deflector 4 than the second lens 1b of the collimator lens l. .

This narrows the interval between the plurality of laser beams on the reflecting surface 4a.

In addition, both lens surfaces of the cylindrical lens 3 are shaped so that their refractive powers are directed in the same direction, thereby reducing the distance between the cylindrical lens 3 and the rotating polygon mirror 4, the lens back, and downsizing the entire device. The interval between the laser beams on the reflecting surface 4a is narrowed.

Now, the distance between the light emitting parts at and am of the semiconductor laser is set to al
+ a t , the focal length of the collimator lens l is f
1. Assuming that the principal plane H° of the collimator lens 1 is extended by Δe1 toward the optical deflector side from the position of the principal plane H' located inside the lens of the conventional collimator lens 5 shown in FIG. Also, by adding curvature to both lens surfaces of the cylindrical lens 3, the lens back (light deflection of the cylindrical lens 3! From the lens surface 3b on the 14 side to the reflective surface 4 of the optical deflector 4
If the distance to a) is made shorter than the lens back of the conventional cylindrical lens 6 with refractive power on only one side by Δe, the principal ray interval d of the two laser beams on the reflective surface 4a of the rotating polygon 114 is d.

is d+dx=(r(+!+-Δ ei)+(e,-Δ e
2) Reflection surface 4 of the conventional optical deflector 4 with lLanθ
a, principal ray spacing of two laser beams at Jz C, C
Calculating the difference ΔL from equation (1) showing 2 is ΔL-C+C*-d+d*-2(Δe, +Δe,)
tanθ−・−・(3), that is, Δ shown in equation (3)
The principal ray interval can be reduced by a certain amount.

For example, f 1=f5=4.78.8t 32=0.1m
m, ei = 20 mm, ex = 40 mm and Δe, = 1
5. When configured so that Δet = 20, the spacing in this embodiment is d+ dt = 0.423, compared to the conventional spacing C+ C* = 1.155, which is approximately l/ of the principal ray spacing obtained in the conventional system. It becomes 3.

In this embodiment, one step in narrowing the principal ray interval of the light beam on the reflecting surface of the optical deflector 4 is to provide a curvature on both sides of the cylindrical lens and to specify the lens shape of the collimator lens. At least one of these methods may be used.

Further, in order to satisfactorily correct the spherical aberration caused by both lens surfaces of the cylindrical lens, it is preferable that at least one lens surface of the cylindrical lens is formed of an aspheric surface along the cylindrical surface.

(Effects of the Invention) According to the present invention, by specifying the lens configuration of the optical means consisting of a collimator lens and a cylindrical lens as described above, when scanning a surface to be scanned using a plurality of laser beams, a scanned image can be 1! An optical scanning device with a simple configuration that reduces the bending of the scanning line and the front curvature of the image plane while reducing the overall size of the 92! can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main parts of one embodiment of the present invention, and FIG.
Fig. 3 is a schematic diagram of a conventional optical scanning device d;
L2I is an enlarged view of a portion of FIG. 1, and FIG. 5 is a sectional view of FIG. 4. In the figure, a, a is a light emitting part of a laser beam, 15 is a collimator lens, 2 is an aperture, 3.6 is a cylindrical lens, 4 is an optical deflector, 31 is a scanning lens, 9 is a surface to be scanned,
ml, m2. e,,e. is the laser beam.

Claims (3)

[Claims] (1) A plurality of laser beams emitted from a plurality of light emitting parts are guided to an optical deflector consisting of a rotating polygon mirror via an optical means, and the reflected beam from the optical deflector is directed to a scanning lens having f-θ characteristics. When guiding light onto the surface to be scanned and performing light scanning, the optical means reduces the distance between the light emitting section and the light deflector, and/or reduces the distance between the plurality of light emissions on the reflective surface of the light deflector. An optical scanning device characterized by having an optical function of reducing the distance between points. (2) The optical means includes a collimator lens and a cylindrical lens in order from the plurality of light emitting parts, and the collimator lens has a main plane H' on the optical deflector side that emits the light of the collimator lens. 2. The optical scanning device according to claim 1, wherein the optical scanning device is configured to be located closer to the optical deflector than a lens surface on the deflector side. (3) The optical scanning device according to claim 1, wherein the optical means includes, in order from the plurality of light emitting units, a collimator lens and a cylindrical lens whose refractive powers are directed in the same direction on both surfaces. .