CN212515109U

CN212515109U - C-lens

Info

Publication number: CN212515109U
Application number: CN202021210716.1U
Authority: CN
Inventors: 金新刚
Original assignee: Jiaxing Xurui Electronic Technology Co ltd
Current assignee: Jiaxing Xurui Electronic Technology Co ltd
Priority date: 2020-06-28
Filing date: 2020-06-28
Publication date: 2021-02-09
Anticipated expiration: 2030-06-28

Abstract

The utility model provides a C-lens, the middle section is the cylindricality, and both ends are for being located the convex sphere of same geometry sphere, and wherein one end has a plane after cutting part or whole sphere, forms the plain end face of C-lens, and the plain end face passes through the optical axis of C-lens, and C-lens length is less than the diameter of the sphere of saying. The C-lens of the utility model adopts the glass ball as raw material, processes the spherical surface in the middle section of the glass ball into the cylindrical surface, so that the cylindrical surface becomes a cylindrical body with spherical surfaces at both ends, and then grinds one of the spherical surfaces into a plane, thus completing the manufacture of the C-lens. The processing of the glass ball has mature technology, high processing precision, stable and reliable spherical surface quality and low cost. The utility model discloses broken through the processing thinking limitation of conventional C-lens, utilized the glass ball as the raw materials, avoided the spherical surface processing problem that the most difficult, constitute the technical bottleneck in the processing technology of current C-lens. Only simple edging and grinding angles are needed.

Description

C-lens

Technical Field

The utility model belongs to the technical field of optical lens, especially, relate to a C-lens.

Background

C-lens is a commonly used collimating lens in fiber optic communication devices, and is often used to collimate light exiting from an optical fiber or to couple a collimated beam into an optical fiber. Particularly, in an optical passive device, the C-lens has extremely wide application, and the demand of one year is tens of millions. The conventional manufacturing process of the C-lens comprises the steps of firstly cutting a glass material into long rods, then rounding the long rods to form cylinders, wherein the outer diameters of the cylinders are generally 1.8mm, 1.0 mm and the like, then cutting the cylinders into a certain length, grinding a spherical surface at one end by using a classical biaxial ball lens grinder, and processing an inclined plane with a certain angle at the other end, wherein the common angle is 8 degrees.

In order to explain the manufacturing method of the existing C-lens in principle and to explain the feasibility and advantages of the present invention later, it is necessary to introduce and analyze the optical principle of the C-lens applied to the collimator.

The C-lens is actually a plano-convex lens, however, in order to meet the requirement of high return loss of the optical fiber device for optical communication, and for convenience of installation, the C-lens increases the lens thickness on the basis of the plano-convex lens to become a cylindrical lens. The cylindrical lens is convenient to mount and has higher structural stability, and meanwhile, the plane is ground into an inclined plane with a certain angle, so that the return loss of a light path can be greatly improved. As shown in FIG. 1, the schematic diagram of C-lens is as follows:

h is the main surface of the C-lens, FS is the back focal length of the C-lens, L2 is the focal length of the C-lens, the size of FS can be changed by the length of L, and assuming that the refractive index of the C-lens material is n, the spherical radius is R, the transparent center length is L, the focal length is: f = R/(n-1); the front focal length is: l2= f; the back focal length is: FS = L1= f- (L/n).

For example, one of the most commonly used C-lens materials in the industry is NSF11, at a wavelength of 1550nm, a refractive index of 1.7449, an outer diameter of 1.8mm, a spherical radius of 1.419mm, a length of 2.98, and an inclined plane angle of 8 degrees, from which we can calculate the lens: focal length f =1.905mm, back focal length L1=0.197 mm.

As shown in the schematic diagram of the conventional collimator in fig. 2, a is an optical fiber head, B is an optical fiber end face, and C is a C-lens:

in the application of a conventional optical fiber collimator, the end face of an optical fiber is positioned at the position of a back focal plane, so that a light beam emitted by the optical fiber forms a collimated light beam through a C-lens, the distance between the end face of the optical fiber and an inclined plane of a lens is FS, the conventional method is to polish the head of the optical fiber by an angle of 8 degrees, and the lens is polished by an angle of 8 degrees in the same way to enable the head of the optical fiber and the lens to be parallel. Thus, when light coming out of the optical fiber exits from the end face of the optical fiber and enters from the end face of the lens, reflected light can be greatly reduced, the distance between the end face of the optical fiber and the inclined plane of the lens is FS, namely L1, which is about 0.197mm, the diameter of a fiber core of the conventional single-mode optical fiber is about 9 mu m, the diameter of an emergent light spot is about 10 mu m, and the size of a light spot reaching the inclined plane of the lens is about 20 mu m after transmission in 0.197mm air. That is, the light beam exiting from the end face of the optical fiber still has a small spot size of about 0.02 mm when it reaches the C-lens inclined plane.

Still taking NSF11 material as an example, the conventional C-lens processing technique is:

a. cutting a large block of NSF11 billet into an elongated billet; b. rounding the square bar stock into a long round bar with the diameter of 1.8 mm; c. cutting the long round rod into short round rods (the specific length is determined according to the processing allowance); d. one end of the short round bar is ground and polished to form a spherical surface by a biaxial spherical surface grinding machine; e. the other end was ground and polished at an angle of 8 degrees while controlling the center length of the lens at this step to 2.98 mm.

The most critical step is spherical grinding. FIG. 3 is a schematic view of a spherical surface grinding process of a biaxial ball lens grinder, in which the upper part of the drawing is a hemispherical grinding swing shaft which swings around the center of the spherical surface in the lower end thereof; the lower part of the figure is a C-lens bar, which rotates around its axis.

Each lens sphere grinding takes over ten minutes, and for mass production, tens of lenses are often ground simultaneously by using a multi-axis machine, such as a 20-axis sphere grinding machine commonly used in the market. In addition to the low processing efficiency, the more serious problem is that the spherical grinding and polishing process has defects and cannot process the lens with a large or small curvature radius. Due to the limitation, the curvature radius of the conventional C-lens is generally about 1 mm-2 mm, and the ideal qualified rate can be obtained in the range. When the curvature radius is too small, the swing shaft is easy to be blocked, so that the bar stock is broken; if the curvature radius is too large, the swing shaft is easy to jump, the spherical surface can be damaged, meanwhile, the quality of the spherical surface cannot be guaranteed, and large phase difference is easy to occur. Both of these conditions severely affect yield. In practice, the yield rate is remarkably reduced when the curvature radius is less than 0.7mm or more than 3mm, and the cost is remarkably increased. Therefore, conventional C-lens is limited in the choice of materials and radii of curvature.

In order to overcome the defects of the prior art, the utility model provides a brand-new C-lens. Greatly reduces the manufacturing cost of the C-lens and has more excellent optical performance than the traditional C-lens manufacturing process.

Disclosure of Invention

The utility model discloses a C-lens. The middle section is cylindrical, two ends are convex spherical surfaces positioned on the same geometric spherical surface, one end is provided with a plane with part or all of the spherical surface cut off to form a flat end surface of the C-lens, the flat end surface passes through the optical axis of the C-lens, and the length of the C-lens is smaller than the diameter of the spherical surface. The shape is described herein for convenience only and is not intended to limit the processing method, and any method such as cutting, grinding, engraving, etching, etc. may be used for the specific processing.

Furthermore, the flat end surfaces are all intersected with the spherical surface to form a circular plane. Or the plane part is intersected with the spherical surface, and the part is intersected with the cylindrical surface.

Preferably, the flat end surface is an inclined plane having an angle of 5 to 10 degrees with the vertical plane of the optical axis.

The manufacturing method of the C-lens of the utility model is as follows: the method is characterized in that glass balls are used as raw materials, the spherical surface of the middle section of each glass ball is processed into a cylindrical surface, the cylindrical surface is made into a cylindrical body with two spherical ends, and then one spherical surface is ground into a plane, so that the C-lens manufacturing is completed.

At present, the processing of the glass ball has a mature process, high processing precision, stable and reliable spherical surface quality and low cost. The utility model discloses broken through the processing thinking limitation of conventional C-lens, utilized the glass ball as the raw materials, avoided the spherical surface processing problem that the most difficult, constitute the technical bottleneck in the processing technology of current C-lens. Only simple edging and grinding angles are needed.

Because the novel C-lens processing method is based on the glass ball, the limitation of the spherical curvature radius of the biaxial spherical grinder is avoided, and the curvature radius of the glass ball is the curvature radius of the C-lens spherical surface. The utility model discloses a method can process various limit lens, for example the C-lens of curvature radius great, long focal length or the C-lens that curvature radius is minimum, the focus is ultrashort, can guarantee good spherical quality and aberration again simultaneously, can guarantee that various different C-lenses all have same technology and comparatively cheap cost. The method is also easy to realize for the C-lens with the curvature radius less than 0.7mm or more than 3mm which is difficult to realize in the prior art. Therefore, the processing efficiency of the C-lens is greatly improved, the manufacturing cost is reduced, and the quality stability of the C-lens is also improved.

In the aspect of plane processing at the other end of the C-lens, the whole spherical surface can be ground into a plane; it is also possible to machine only the plane of the size required for spot transmission, which of course must necessarily pass through the optical axis.

The following three methods can be used for grinding the glass ball into the cylindrical surface: one method is characterized in that a lathe is utilized, two coaxial lathe top columns clamp two ends of a glass ball to rotate, and a grinding cutter parallel to a glass ball rotating shaft grinds the glass ball until a cylindrical surface with a preset size is ground; the second is another grinding by a centerless grinder or an edge grinder; the third is engraving with a high precision engraving machine.

Drawings

FIG. 1 is a schematic view of a C-lens;

FIG. 2 is a schematic diagram of a conventional collimator;

FIG. 3 is a schematic view of a spherical grinding process;

FIG. 4 is a schematic view of the shape of the C-lens of the present invention;

FIG. 5 is a flow chart of the manufacturing process of the C-lens of the present invention.

Detailed Description

The following describes embodiments of the present invention with reference to the drawings.

As shown in fig. 4. The outer circle of the drawing shows a raw material glass sphere, wherein the dotted line shows a portion removed after processing; the dotted line in the figure is the optical axis of the C-lens. The middle section is processed to form a cylinder with two convex spherical surfaces at two ends. The left side S1, S2, and S3 respectively show three cross-sectional positions, all at an angle to the perpendicular to the optical axis (i.e., a plane perpendicular to the optical axis): s1 is completely on the spherical surface, and the end plane of the formed C-lens is a circular plane; s2 is partially truncated on the cylindrical surface; s3 is completely truncated on the cylindrical surface, i.e. the spherical surface of the end is completely truncated. All three sections pass through the optical axis.

The manufacturing process of the C-lens of the utility model is shown in FIG. 5, wherein the upper part of the figure mainly shows the size change of the workpiece (from the glass ball to the C-lens) in each step, and the lower part of the figure mainly shows the shape change.

The conventional C-lens of NSF11 material is still used as an example.

a. Selecting NSF11 glass spheres with the diameter of 1.419mm (curvature radius) multiplied by 2=2.838 mm;

b. ball-milling the glass into cylindrical lenses with the diameter of 1.8 mm;

c. a flat surface is ground at a spherical position.

In fig. 5, the last step: if the chamfer is 8 degrees and the entire 1.8mm outer diameter is chamfered, the lens length is about 2.4 mm, much shorter than the conventional 2.98C-lens length, which increases the back focal length to 0.5 mm. However, as mentioned above, since the lens is a thick lens, when the light beam emitted from the optical fiber reaches the inclined plane of the lens, the spot size is still small, and the whole 1.8mm is not required to be used as the light-passing surface. In fact, only one spherical surface needs to be ground to form a small plane for light passing. For example, by grinding an inclined plane of about 0.3 mm on a spherical basis, the total lens length can be increased to 2.8 mm. The back focal length is then 0.3 mm, very close to the convention of using a lens conventionally. At this time, as a result of the calculation, when the light beam emitted from the optical fiber reaches the inclined plane, the size of the light spot is about 0.02 mm, and the light-passing surface of 0.3 mm can completely meet the light-passing requirement of the lens.

The manufacture of conventional C-lenses is exemplified above in order to compare more intuitively with the prior art. In fact, the present invention is advantageous in manufacturing various extreme lenses, such as C-lenses having a large radius of curvature, a long focal length, or C-lenses having a very small radius of curvature and a very short focal length. Such as C-lens with a radius of curvature of less than 0.7mm or greater than 3 mm.

The utility model discloses a C-lens can be with the lathe processing cylinder on the glass ball, also can use centerless grinder or edging machine tooling, can also utilize the high accuracy engraver to carve into the column with the side of glass ball.

Claims

1. A C-lens, characterized in that: the middle section is cylindrical, two ends are convex spherical surfaces positioned on the same geometric spherical surface, one end is provided with a plane with part or all of the spherical surface cut off to form a flat end surface of the C-lens, the flat end surface passes through the optical axis of the C-lens, and the length of the C-lens is smaller than the diameter of the spherical surface.

2. A C-lens according to claim 1, wherein: the flat end surface is completely intersected with the spherical surface to form a circular flat end surface.

3. A C-lens according to claim 1, wherein: the flat end surface is partially intersected with the spherical surface and partially intersected with the cylindrical surface.

4. A C-lens according to claim 1, wherein: the flat end surface is an inclined plane, and an included angle of 5 to 10 degrees is formed between the flat end surface and the vertical surface of the optical axis.