JPS635217B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a spherical surface of a bar lens for forming spherical surfaces at both ends of a bar lens used in a compound eye projection device such as a compact copying machine.

Conventionally, the manufacturing of glass lenses generally involves four steps: roughing, sanding, polishing, and centering, but the processing time is 5 to 10 minutes per side. Among these, the polishing process accounts for the majority.

Conventional polished lenses have a processed surface roughness of 0.01μ
m or less, and a surface rougher than this would cause more flare, lower illuminance, and poor resolution, making it difficult to put it into practical use.

The present invention realizes a significant reduction in processing time when forming a bar lens having a longer length in the optical axis direction than its effective diameter from a glass fiber rod by reducing the spherical surface processing step to only grinding. This guarantees a predetermined surface accuracy required for a lens used in a copying machine, especially a compound lens consisting of a bar lens that projects a partial area of a document onto a predetermined partial area of a photoreceptor.

The bar lens formed according to the present invention has a surface roughness of 0.05 to 0.1 μm, can be processed in a short time only by grinding, and does not require centering.

Hereinafter, the present invention will be described in detail using the accompanying drawings.

A first embodiment of the invention is shown in FIG.

First, a glass fiber rod 1 that has been precisely machined to have an outer diameter of approximately ±5 μm is fitted into a collect chuck 3 that is received by a high-precision bearing 2. Here, the outer circumference of the glass fiber rod 1 may be coated with black paint or the like to block light.
Since the bar lens to be finally obtained has a long length in the optical axis direction, it can be easily held with a collector chuck or the like. By the way, glass fiber rod 1
A processing grindstone 4 is supported by a high-precision bearing 5 and installed in the opposite direction. Note that 6 and 7 are both motors. The processing grindstone 4 has a cylindrical shape, and its inner surface is a grinding surface, and its rotation center axis is installed obliquely to the center axis of the glass fiber rod 1.

The glass fiber rod 1 is rotated by the motor 6 at low speed without deflection, while the processing grindstone 4 is rotated by the motor 7 at high speed.

The machining grindstone 4, together with the high-precision bearing 5 and the motor 7, is sent in the direction of arrow A from the state shown in FIG. 1, and after machining has been completed to a predetermined position, returns to the position shown in FIG. At this point, the machining of one spherical surface is completed. Similarly, the other end is spherically processed. With this machining method, the machining time for one surface is as short as about 3 seconds, and since eccentricity is determined by machine precision, there is no need for centering work in the post-process.

In addition, if the spherical curvature is large and the cutting allowance is small, only a finishing whetstone may be used, but a rough whetstone (#400 to #600) may be used.
A spherical surface with higher surface precision can be obtained by using two types of grinding wheels (#2000 to #3000) in two steps. Next, a second embodiment of the present invention is shown in FIG.
This will be explained with reference to FIG.

The processing grindstone 8 has grooves 9 formed in a predetermined circular arc on its surface. As shown in FIG. 3, the grooves 9 are machined on a circumference equidistant from the central axis with high accuracy. Glass fiber rod 1
is rotated at high speed by the motor 6 without any deflection, while the processing grindstone 8 is rotated relatively slowly around the central axis of rotation. Note that the glass fiber rod 1 is placed precisely over the center of the groove. The rotating glass fiber rod 1 is then fed a predetermined amount in the direction of arrow B from the state shown in FIG. 2, and its surface is processed into a spherical lens.

All of the processing methods described above process a spherical surface in a short time and provide a bar lens with a predetermined surface accuracy at a low cost.

Furthermore, the present invention can be said to be a processing method that is very suitable for automatic processing.

Note that after this processing, the lens surface may be baked with a strong acid such as nitric acid to generate an oxide film to increase the transparency effect.

Mechanically, rubbing the lens surface for a short time with an elastic grindstone or elastic belt made of sponge, rubber, etc. is effective in reducing surface roughness, increasing illumination, reducing flare, and increasing resolution.

Note that the present invention is effective not only for spherical processing of bar lenses made of glass, but also for spherical processing of bar lenses made of other lens materials, such as plastic, and can be finished to a predetermined surface accuracy. .

As described above, according to the present invention, it is possible to process the spherical surface of a bar lens used in a compound eye projection device, particularly a compound eye projection device suitable for a compact copying machine, etc., in a short time and at low cost, and to finish the surface with a surface precision that satisfies a predetermined image performance. .

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the first embodiment of the present invention;
3 and 3 are explanatory diagrams of a second embodiment of the present invention. In the figure, 1...Glass fiber rod, 2,5
...High precision bearing, 3...Collection chuck, 4,
8... Processing grindstone, 6, 7... Motor, 9... Groove.

Claims (1)

[Scope of Claims] 1. A fiber rod is held and rotated by a holding member, a cylindrical processing grindstone is rotated at a higher speed than the fiber rod, and the center axis of rotation of the processing grindstone is set relative to the center axis of the fiber rod. A method for forming a spherical surface of a bar lens, characterized in that the fiber rod is installed obliquely and a spherical surface is formed at the end of the fiber rod using the processing grindstone. 2. The method for forming a spherical bar lens according to claim 1, wherein the outer peripheral portion of the fiber rod is subjected to a light shielding treatment.