JPS6350650Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a method for fixing a lens group of a tilt correction optical system used for optical scanning of a laser beam printer.

"Problems to be solved by prior art and invention" Conventional laser beam printers convert the light beam emitted from a semiconductor laser into a parallel light beam using a collimator lens, reflect it using a rotating polygon mirror, and convert it into an f-theta (F-theta) lens. Therefore, it was configured to scan the imaging beam on the photoreceptor at a constant speed.

However, with this method, if the rotating polygon mirror is mounted at an angle with respect to the rotation axis, or if each mirror part of the rotating polygon mirror is machined to be tilted at different angles with respect to the rotation axis, the scanning beam on the photoreceptor may become unstable. It appears as uneven scanning line pitch without scanning a fixed area.

In recent years, a tilt correction optical system for eliminating such defects has been proposed in Japanese Patent Application Laid-Open No. 144514/1983.

FIG. 1 shows an example of the above-mentioned tilt correction optical system. 1
1 is a semiconductor laser device attached to the outer surface of the optical box 6, and the inside thereof consists of a semiconductor laser package and a collimator lens. A cylindrical lens 2 forms an image of a laser beam on the mirror surface of a rotating polygon mirror 3 mounted in an optical box 6 and rotating in the direction of arrow A. 4 is a spherical lens and is a concave lens.
Reference numeral 5 denotes a Torytsu lens, which is a convex aspherical lens. These cylindrical lens 2, spherical lens 4, and torlic lens 5 are fixed in an optical box 6 to form a tilt correction optical system. Reference numeral 6 denotes an integrated optical box, which is sealed with a lid (not shown) fixed to the top. The photoreceptor 7 is provided outside the optical box 6 and parallel to the front surface of the optical box 6.

FIG. 2 is a longitudinal cross-sectional view showing a conventional method of fixing the Tory lens 5 among the above lens groups. A Torytsu lens 5 is mounted on pedestals 8a and 8b fixed to a base 8 fixed to the lower surface of an optical box 6 (FIG. 1), not shown, and one end is supported by a support member 9 fixed to the optical box 6. It is provided so as to be positioned in the direction orthogonal to the optical axis by the other end of the supported pressing plate spring 10. 11 is a stopper in the optical axis direction of the Tory lens 5;
It is in contact with the back part near both ends of. An L-shaped pressing leaf spring 12 fixed to the base 8 pushes the lower part of the curved surface of the front surface of the torrick lens 5, and the back surface of the torrick lens 5 is pressed against the stopper 11.

However, the pressing leaf spring 12 is
Since the curved surface of the base 8 is pressed in a nearly horizontal direction, a force is generated that pushes the Tory lens 5 upward, making it unstable. When the impact is applied to the entire base 8, the Tory lens 5 is pushed upward and the light is This causes axis misalignment. Furthermore, in order to prevent such lifting of the lens, it is possible to increase the pressing force of the pressing plate spring 10, but if an excessive pressing force is applied to the lens, the Toritsu lens 5 will be distorted and the lens performance will be significantly reduced. It turns out. As described above, conventional lens fixing methods cannot be said to sufficiently withstand shocks during transportation.

Further, in Japanese Patent Application Laid-Open No. 153907/1983, it is considered to form flat portions at both ends of a scanning lens and to fix the lens using these flat portions.

However, in this Japanese Patent Application Laid-Open No. 58-153907, it is necessary to form the two plane parts parallel to each other with high accuracy.
Furthermore, since the lens is fixed at two locations on both ends of the lens, the stability of the lens is poor, and in order to obtain high stability, it is necessary to form a large flat portion.

Furthermore, since the position is fixed only outside the laser beam scanning range, it is difficult to obtain accuracy within the laser beam scanning range.

"Means for Solving the Problems" This invention solves the above problems, and uses a light source that emits a laser beam, a rotating polygon mirror that deflects the laser beam emitted from this light source, and this rotating polygon mirror. In an optical scanning device comprising an inclination correction lens having a flat shape elongated in the direction of deflection by a rotating polygon mirror into which a deflected laser beam is incident, a flat surface provided on a convex curved surface in the center of the inclination correction lens. The lens is characterized in that lens fixing members are provided on the flat part, and on both end sides of the back surface of the lens.

"Example" Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a longitudinal sectional view showing an embodiment of the present invention. Components with the same reference numerals as those in FIG. 2 have the same configuration and function, and therefore their explanation will be omitted.

A flat Tory lens 5' with a long deflection direction formed by a rotating polygon mirror has a recessed portion at the lower end of the approximately central portion of the curved surface portion on the front surface, and a flat portion 5'a perpendicular to the optical axis on the bottom surface of the recessed portion. There is. Reference numeral 12' denotes a Z-shaped pressing leaf spring whose lower flange is fixed to the base plate 8, and the corner 12'a between the upper flange and the web of the pressing leaf spring 12' is the flat part 5'a of the front surface of the Tory lens 5'. is in pressure contact with.

Since the corner 12'a of the pressing leaf spring 12' presses the flat portion 5'a of the Tory lens 5', no force is generated to lift the Tory lens 5', and the Tory lens 5' is stably supported.

FIG. 4 is a perspective view of the above-mentioned Tory lens 5'. For example, a concave portion having a flat surface 5'a on the bottom may be formed by molding a glass mold into a Tory lens 5'.
When polishing the toric surface 5'b, the toric surface 5'b and its opposing surface may be polished after forming the concave portion in advance during glass molding.

Furthermore, although the flat portion 5'a is disposed below the toric surface 5'b of the toric lens 5', it can also be disposed above the toric surface 5'b.

Furthermore, it is also possible to apply to all the lens groups used in the present invention.

The present invention is also applicable to a scanning optical device having a correction optical system using a toroidal lens.

[Effect of idea]

According to the present invention explained above, it is possible to prevent the lifting of the lens for correcting distortion, and it is possible to hold it stably even against impact, and the plane part only needs to be formed in one place, and the plane part and the back surface of the lens can be formed in one place. Stable three-point support is possible.

Furthermore, since a flat portion is formed in the center of the tilt correction lens that serves as a reference within the laser beam scanning range, high positional accuracy of the tilt correction lens within the laser beam scanning range can be easily obtained.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing a conventional example, Fig. 2 is a vertical cross-sectional view of a conventional toric lens holding means, Fig. 3 is a longitudinal cross-sectional view showing an embodiment of the present invention, and Fig. 4 is a perspective view of the toric lens. It is a diagram. 1... Semiconductor laser device, 5, 5'... Toritz lens, 8... Base, 8a, 8b... Pedestal,
9... Support member, 10, 12, 12'... Pressing plate spring, 11... Stopper.

Claims (1)

[Claims for Utility Model Registration] A light source that emits a laser beam, a rotating polygon mirror that deflects the laser beam emitted from the light source, and deflection by the rotating polygon mirror that receives the laser beam deflected by the rotating polygon mirror. An optical scanning device having a tilt correction lens having a flat shape long in the direction, a flat part provided on a convex curved surface at the center of the tilt correction lens, and this flat part and both ends of the back surface of the lens. An optical scanning device characterized in that a lens fixing member is provided on both sides.