JPS58153907A - Lens for scanning - Google Patents

Abstract

PURPOSE:To surely hold lenses in an optical scanning system, by changing the external shape of each of the lenses from the circular shape to a flat shape and by converting the lens surfaces of both edges into plane surfaces. CONSTITUTION:In a scanning lens system, only the hatched parts of the lenses shown by a figure 1 are utilized, so the lenses are made flat in directions perpendicular to the direction of the optical axes and the direction of scanning, and the lens surfaces of both edges in the direction of scanning are converted into plane surfaces P1, P2 shown by a figure 2 to easily attach the lenses to a lens barrel and to eliminate a shift in the axes.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scanning lens used in a scanning optical meter system such as a laser beam printer.

BACKGROUND OF THE INVENTION FIG. 1 shows a conventional example of a scanning optical system for a laser beam printer. In this figure, a laser beam generated by a semiconductor laser generator (1) is reflected by a rotating polygon mirror (2), passes through a scanning lens (3), and reaches a photosensitive drum (4). Then, the deflection angle is changed by the rotation of the rotating polygon mirror (2), and the arrow a appears on the photosensitive drum (4).
Perform direction scanning and repeat this. Here, the scanning lens (3) is a lens with distortion according to the rotational characteristics of the rotating polygon mirror (2). If the deflector is a rotating polygon mirror, the ideal image height y is f・θ. If the f/θ lens and deflector are sinusoidal oscillating mirrors, then the imaginary height y is f-arcsi
It is an arcsine lens with nθ. These distortion aberrations Dis are expressed by setting the image height of the actual gap as y'.

As shown in FIG. 1, a conventional scanning lens is composed of a circular lens when viewed from the optical axis direction, and has a conical or cylindrical shape as a whole. However, as the batting average increases as other elements of the scanning optical system, such as the use of semiconductor lasers, become more compact, it has been desired to make the scanning lens more compact.

The light beam actually passes through the scanning lens made of a circular lens only through the rectangular part parallel to the scanning direction of the light beam, which is indicated by hatching in Figure A of fj2, and the other parts are This is an unnecessary part of the lens. Therefore, as shown in Fig. 3, it is conceivable to flatten the three scanning lenses in the optical axis direction and the direction orthogonal to the scanning direction. In other words, the scanning lenses are shown by solid lines in Fig. 2A. However, if this flattening is simply carried out, the following problems will arise.

In other words, the conventional positioning and fixing of the scanning lens was performed by making circumferential line contact with the inner surface of the lens barrel, as shown in Figure 2B, but this was flattened into a dosimetric line and the conventional positioning and fixing was done. When attempting to do this, as shown in Figure 2C, the arc-shaped abutting surface P must be machined to an accurate position and shape with respect to the center of the lens when viewed from the optical axis direction, and such processing is extremely difficult. This increases the number of difficult processes. Further, even if processing can be performed with a certain degree of accuracy, the contact surface is small, so each lens of the assembled scanning lens will be decentered, making it impossible to obtain sufficient performance. The second diagram shows a case in which the lens barrel is subjected to 7-rice processing, but in this case, it is supported at several points, and as with the above, sufficient performance cannot be obtained.

Purpose/Summary The present invention has been made in view of the above, and an object of the present invention is to provide a flat scanning lens that can be easily manufactured and that allows the lens to be held securely.

The above object is achieved by forming flat parts at both ends in the scanning direction of at least one of the lenses constituting the scanning lens to serve for holding.

Embodiment 1 FIGS. 4 and 5 are views of examples of various lenses constituting the scanning lens of the present invention, viewed from above.

Figure 4 shows flat parts Pi at both ends of both lens surfaces in the scanning direction.
P2 is formed, and FIG.
), meniscus lens (BL), biconvex lens (C1), plano-convex lens (DL), and plano-concave lens (e) are shown, respectively.

Figures 6 and 7 show the biconvex lenses (C1 and 5) of Figure 4, respectively.
The figure shows a front view and a side view of the meniscus lens (bl) in the figure. Both side portions Q are also flat, and on the other hand, in FIG.
1 is formed, and both sides are arcuate. Note that the flat portion formed on the lens surface does not need to be parallel to the plane orthogonal to the optical axis.

As a method for processing such a lens, a number of methods can be employed, such as a method of cutting a circular lens, a method of processing a surface of a rectangular parallelepiped into a lens surface, or a method of plastic molding.

By forming a flat part on at least one of the lens surfaces, this flat part can be brought into surface contact with the holding member as a contact surface, so when the lens is placed at the position of the lens and held against the contact surface, the lens is held. Eccentricity around the optical axis can be prevented.

Whether the flat portion is formed on both sides of the lens surface or only on one side may be determined as appropriate depending on the method of holding the lens. An example of how to hold the lens will be explained below.

Figure 8 shows the holding of a flat lens with flat parts on both lens surfaces, with the holding member (6) and the holding member (7) holding both the flat parts.
) to position and fix it. still,
In FIG. 8 and FIGS. 9 to 13 described below, (A) is a front view and (0) is a side view.

Figures 9, 10, 11, and 12 show a flat lens having a flat surface on only one lens surface, which is fixed by a holding member (6) and a spring-like pressing member (7). Here, in Fig. 9, the holding member (7a) is screwed to the holding member (6) from the optical axis direction and presses the lens surface at one point, and in Fig. 10, it is screwed in the same way and holds the lens surface. It is held down at two points by a concave holding member (7b) along the convex surface. FIGS. 11 and 12 show examples in which the screwing direction of the presser member in FIGS. 9 and 10 is changed.

13 and 14 show a suitable positioning and fixing method when a flat lens is molded into a plastic film. That is, in FIG. 13, a through hole is formed in the flat surface of a plastic-molded lens, and the lens is fixed to a holding member (6) by a screw (8) passing through this through hole. On the other hand, in Fig. 14, the threaded part (8
a) is formed, and this threaded portion (8a) is secured with a nut by sandwiching the holding member (6).

Figure 415 shows an example of assembling a traveling lens using three flat lenses of the present invention. In FIG. 15, the scanning lens is a plano-concave lens (Ll) from the incident side.

Consisting of a meniscus lens (L2) and a biconvex lens (L3), these lenses are held by holding members (10) (11),
Spring holding member (12a) (12b) (13a)
(13b) (14a) (14b) and are positioned and held by upper and lower lid members (not shown). That is, the lens (
Ll) CL, > (L3) The incident side lens surface is (
Lla) (Lza) (Lzb), and the exit side L/7 lens surface is (Lxb) (Lzb) (Lsb), then the lens surface (
The flat parts formed in Llb) (Lza) (L3a) are the contact surfaces (10-1) (11-1) (10-1) of the holding member, respectively.
2) (11-2), (10-3), and (11-3), respectively, and the lens surfaces (Lta), (Lzb, and Lsb) are pressed against the holding members (12a), (12b), (13a), (13b), 14
a) Fixed at (14b). Although the presser member is shown in a simplified manner in FIG. 13, the above-described holding method can be used as appropriate.

The scanning lens constructed in this manner is very easy to assemble and can provide sufficient accuracy.

Effects As described above, in the present invention, the lenses constituting the scanning lens have a flat shape in the direction perpendicular to the optical axis direction and the scanning direction, and at least one lens surface of the constituent lenses has a flattened shape at both ends in the scanning direction. This has the advantage that it is easy to assemble the lens by forming a flat part.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a scanning optical system of a conventional laser beam printer, Fig. 2 is a diagram showing a scanning optical system with a flat scanning lens, and Figs. Figures 8, 9, 10, 11, 12, 13, and 13 are diagrams explaining the process. 1----Laser beam generator 4°...Photosensitive drum 6.10.11...Holding member 7.12, 13.14...Press member 8.8a...Screw, screw part Applicant: Minolta Camera Co., Ltd. Figure 1 Go to Figure 2 1114 (a) C8) (Q) (d
(e) Figure 5 (d) <e) Figure 6 Figure 8 Figure 11 Figure 12 Procedural amendments Showa sr=+Ji! L1/S Date Kazuo Wakasugi, Commissioner of the Japan Patent Office1, Indication of the case, Patent Application No. 37390 of 1982, Name of the invention, Scanning lens 3, Person making the correction Relationship to the case Applicant Address Azuchi-cho, Higashi-ku, Osaka City 2-80 Osaka Kokusai Building name (607) Minolta Camera Co., Ltd. 1982
June 11, 2016 (Shipping date: June 29, 1982) 5. Column for a brief explanation of drawings in the specification subject to amendment and drawings 6. Contents of the amendment (1) Brief explanation of drawings in the specification Column page 9, line 11 “
It is a diagram. Insert the following text after ``. ``In addition, in Figures 2, 6, and 7, the left side is a front view viewed from the optical axis direction, and the right side is a side view viewed from a direction parallel to the scanning direction.'' (2) Figure 2 of the drawings, Figures 6 and 7 are corrected as shown in the attached sheet. Above 1g2 figure A 16 figure

Claims (1)

[Claims] 1. In a scanning lens for uniformly scanning a beam from a light source on an image forming plane by a deflector, the lens constituting the scanning lens is flattened in a direction perpendicular to the optical axis direction and the scanning direction. What is claimed is: 1. A scanning lens characterized in that the scanning lens has a shape, and flat portions are formed at both ends in the scanning direction of at least one lens surface of the constituent lens.