JPS6218516A - Cylinder compressor lens in light scan optical system - Google Patents

Abstract

PURPOSE:To realize a cylinder compressor lens having an excellent light transmission efficiency at an extremely low cost and to compact it easily by constructing said lens with a plane convex and concave cylindrical lenses. CONSTITUTION:The plane convex cylindrical lens 13 and the plane concave cylindrical lens 15 compose of a cylinder compressor lens. Where the focus distance of the plane convex cylindrical lens 13 and that of the plane concave cylindrical lens 15 are f1L and f2L, respectively, the synthesized focus distance F of the cylinder compressor lens in the direction corresponding to a subscan direction is expressed by equation (1) with the inter-main point distance of each cylindrical lens (d). The f1L, f2L and (d) are appropriately selected, whereby the synthesized focus distance F can be set to the same one as a conventional cylindrical lens. When f1L.f2L<0, the cylindrical compressor lens can be compacted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a cylinder combination lens in an optical scanning optical system.

(Prior Art) A light scanning optical system as shown in FIG. 2 is conventionally known. Hereinafter, the outline of optical scanning will be explained based on the beam scanning optical system shown in FIG. 2, and the problems to be solved by the present invention will also be explained.

In FIG. 2, a laser light source 10 (for example,
The light emitted from the semiconductor laser is collimated by the collimator lens 12 , the diameter of the beam is compressed by the beam compressor lens 14 , and the light is incident on the cylindrical lens 16 .

After that, the light beam is transferred to the polygon mirror 18A of the scanner 18.
The light is reflected by the fθ lens 20 and is imaged onto a photosensitive recording medium 22 (for example, a photoconductive photoreceptor). When the motor 18B of the scanner 18 rotates the polygon mirror 18A in the direction of the arrow, the imaging point of the light beam is focused on the recording medium 2.
2 in the direction of the arrow. This scanning direction is referred to as a main scanning direction, and is referred to as an optical scanning position and an optical scanning section. By rotating the recording medium 22, the surface of the recording medium is sequentially scanned with light. Therefore, in the optical scanning section, a plane that is in contact with the surface of the recording medium is considered, and a direction on this tangential plane that is orthogonal to the main scanning direction is referred to as a sub-scanning direction.

Now, the generatrix direction of the cylindrical lens 16 corresponds to the main scanning direction, so the light incident on the polygon mirror 18A is a parallel light beam in the direction corresponding to the main scanning direction, but in the direction corresponding to the sub scanning direction, In order to obtain the necessary beam spot at the optical scanning section (the imaging section for the light flux), the light is convergent or divergent. In the optical scanning optical system shown in FIG. 2, the beam compressor lens 14 only serves to compress the light emitted from the collimating lens 12 and improve the light transmission efficiency.

By the way, beam compressor lenses generally require a large number of lenses and are expensive.

(Objective) The present invention has been made in view of the above-mentioned circumstances, and its object is to provide a novel cylinder that can be realized at low cost, is compact, and has good light transmission efficiency. Provided by compressor lenses.

(composition) The present invention will be explained below.

The cylinder compressor lens of the present invention is.

It is composed of two cylindrical lenses.

That is, one is a plano-convex cylindrical lens and the other is a plano-concave cylindrical lens.

This cylinder compressor lens receives a parallel beam of light in the light scanning optical system, and converts the incident parallel beam of light into
It is used to convert the light beam into a parallel light beam in a direction corresponding to the main scanning direction, and a convergent light beam or a diverging light beam in a direction corresponding to the sub-scanning direction. In other words, this cylinder compressor lens has the same function as the optical system constituted by the beam compressor lens 14 and the cylindrical lens 16 in FIG. 2. Of course, the purpose of converging or diverging the light beam in the direction corresponding to the sub-scanning direction is to obtain a necessary beam spot in the optical scanning section.

A specific embodiment will be described below with reference to one drawing.

In FIG. 1, the reference numerals 10 and 12 indicate a laser light source and a collimating lens, respectively, as in FIG. The laser light emitted from the laser light source 10 is
The collimating lens 12 converts the light into a parallel beam. In FIG. 1, reference numeral 13 indicates a plano-convex cylindrical lens, and reference numeral 15 indicates a plano-concave cylindrical lens. These plano-convex cylindrical lenses 13 and plano-concave cylindrical lenses 1
5 constitutes the cylinder compressor lens of the present invention.

FIG. 1(1) is a view seen from a direction corresponding to the sub-scanning direction. Therefore, in FIG. 1(1), the up-down direction is a direction corresponding to the main-scanning direction, and each cylindrical lens 13. The generatrix direction 15 corresponds to this scanning direction. In this way, the cylinder compressor lens does not have power in the direction corresponding to the main scanning direction, so in this direction, the parallel light flux entering from the collimating lens 12 side maintains its parallelism.
Transmits through the cylinder compressor lens.

FIG. 1(n) is a diagram viewed from a direction corresponding to the main scanning direction, and the vertical direction of the diagram corresponds to the sub-scanning direction. In this direction, each cylindrical lens 13.15 has positive and negative power, respectively. Therefore, the focal length of each cylindrical lens is fLL l for the plano-convex cylindrical lens 13.
5 on b, gtJ In the direction corresponding to the scanning direction, the composite focal length F of the cylinder compressor lens is the distance between the principal points of each cylindrical lens d
As, it is.

Therefore, by appropriately selecting f, L, f2 and d, the composite focal length F can be made the same as the focal length of the cylindrical lens 16 in FIG.

The composite focal length F is f, L, f21. By the relationship of d.

It can be positive or negative; if it is positive, it will be cylinder conjunction, and if it is negative, it will be divergent light.

Also.

By setting flL−hL<O(2), the cylinder compressor lens becomes compact.

(Effects) As described above, according to the present invention, novel effects in a light scanning optical system are achieved.
cylinder compressor. We can provide lenses. Since this cylinder compressor lens is composed of two cylindrical lenses, it has good light transmission efficiency, can be realized at extremely low cost, and can be easily made compact. Also.

Even if the cylinder compressor lens has a long focal length, the five individual cylindrical lenses can have short focal lengths, making it easy to inspect the lenses.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, and FIG. 2 is a diagram for explaining the prior art. 10... Laser light source, 12... Collimating lens, 13... Plano-convex cylindrical lens, 15...
...Plano-concave cylindrical lens. '! , 1 +'b so 21st

Claims (1)

[Claims] In a light scanning optical system, a parallel light beam is incident, and the incident parallel light beam is a parallel light beam in a direction corresponding to the main scanning direction, and is a parallel light beam in a direction corresponding to the sub-scanning direction.
A cylinder compressor lens is a lens for converting a convergent or diverging light beam into a light beam, and is composed of a plano-convex cylindrical lens and a plano-concave cylindrical lens.