CN115220175A - Optical component with high surface shape precision and its sealing method - Google Patents

Abstract

A high surface shape precision optical component and its sealing method, the said high surface shape precision optical component includes the optical lens with high surface shape precision, according to the geometric dimension and material attribute of the optical lens, the metal mirror bracket with through hole in the middle of the different material of adaptation, the said welding method is to adopt the low-melting point metal solder to weld, form a layer of soft metal solder buffer layer between lens and mirror bracket after welding, relieve the thermal stress caused by temperature unevenness between lens and mirror bracket to a great extent, make the lens after welding still can keep higher surface shape precision, the optical component prepared has the lens surface shape precision high, the mirror bracket and the characteristic that the heat conductivity is good between the optical lens, the welding position has high reliability performance indexes such as good vacuum seal and radiation-resistant at the same time, suitable for the precision optical systems such as the space optical pickup, optical resonator, etc.

Description

Optical component with high surface shape precision and its sealing method

technical field

The invention relates to a connection method of an optical component, in particular to an optical component with high surface shape precision and a sealing method thereof.

Background technique

At present, the connection methods of optical lenses and frames with high surface shape accuracy are roughly divided into three types: one is the more traditional connection method fixed by mechanical force, such as the method of screw pressing, that is, the use of internal The threaded pressure ring is screwed into the frame with the external thread matching the pressure ring, and the lens is fixed in the pressure ring and the lens barrel; the second is to use glue, that is, use optical assembly glue to clear the lens surface. The edge area of the lens or the peripheral surface of the lens side and the corresponding area of the frame are glued together to fix the optical lens. Patent CN 114114607 A describes a method for fixing flat optical mirrors by pouring glue, but this method is only suitable for flat mirrors, and has certain limitations for the fixing of transmission optical elements or dichroic mirrors; the third is to use flat welding The way.

Due to the mechanical force, the optical lens fixed by mechanical force may generate a certain amount of stress and strain, resulting in changes in the surface shape of the lens, which will affect the beam quality to a certain extent; Exposure to mechanical vibrations can cause threads to loosen and the long-term reliability of optical components cannot be guaranteed. The optical components prepared by the adhesive method, although the flexible optical assembly adhesive can effectively reduce the influence of temperature changes on the shape when the temperature changes, and the reliability is also high, but the anti-aging ability is insufficient. It will generate a certain amount of heat, and it is difficult for the adhesive layer to effectively transfer the heat accumulated in the lens quickly, and the thermal conductivity is poor, so in the process of long-term use, a large amount of heat in the lens accumulates, which will affect the surface shape and shape of the optical lens. The reliability of optical components presents challenges that affect beam quality. Patents 100364707C and CN 109116504 A introduce a method for connecting an optical window and a window frame by means of plane sealing. The stress on the two light-passing surfaces of the window in the connecting device is unbalanced, which will inevitably affect the surface shape accuracy of the two light-passing surfaces of the optical window.

Patent CN 109926748 B discloses a vacuum observation window sealed by metal solder and a manufacturing method thereof. The vacuum observation window adopts the outer sealing method to seal the lens of non-metal material and the thin-walled transition piece of metal material through medium temperature metal solder Get up and get an air-tight, high-strength sealing window. A thin-walled structure is used to reduce the residual stress of the non-metallic lens and the metal transition piece, and a layer of metal solder is filled between the thin-walled structure and the lens as a stress buffer area. The prepared vacuum observation window is used in vacuum brazing Vacuum equipment such as welding furnaces and coating machines have extremely high requirements on the air tightness and strength of sealing devices. However, limited to the use of the vacuum observation window and its use environment, the sealing temperature is generally above 300°C, and the strength of the metal solder used is relatively high, which is very unfavorable for lenses with high surface shape accuracy or surfaces coated with optical films , therefore, this method is not suitable for the welding of optical components that require surface accuracy.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the deficiencies of the above-mentioned prior art, and to provide a high-surface-precision optical assembly and a sealing method thereof, which have the following technical advantages: First, by metallizing the side circumferential surface of the optical lens, using The low-temperature metal solder enables the frame and the optical lens to be directly and effectively connected. This connection method can form a flexible transition layer between the optical lens and the frame. It does not need the thin-walled transition structure in the patent CN 109926748 B. In the process of connecting and fixing the small optical lens and the frame, the residual stress of the lens due to the external constraints of the frame ensures that the lens still has high surface shape accuracy after welding; The sealing method can maximize the effective clear aperture of the optical lens, or minimize the size of the lens and the frame under the condition of a certain clear aperture required to achieve the purpose of weight reduction, thereby helping the entire optomechanical system. The second is to use the side sealing method, which can maximize the sealing area between the lens and the frame under the condition of a certain geometric size of the lens, so it can improve the shear strength of the sealing part and increase the The pressure resistance performance of optical components; the third is the increase of sealing area, which helps to improve the vacuum airtight performance of optical components.

The technical solution of the present invention is as follows:

An optical component with high surface shape precision, comprising an optical lens and a frame. The reflective surface shape accuracy (or transmission wavefront error accuracy) of the surface S1 or S2, PV ₀ is better than 1/10λ@632.8nm, RMS ₀ is better than 1/20λ; the outer circumferential surface or elliptical circumferential surface S3 of the optical lens is an optical lens welding area;

There is a through hole in the middle of the frame, the diameter of the through hole is matched with the outer diameter of the optical lens, and the optical lens is embedded; one end of the through hole is a solder drainage chamfer, and the other end is provided with a solder drainage groove and a lens. Limit step; the large circumference of the through hole is the welding area of the mirror frame;

The spectacle frame is nested on the outer circumference of the optical lens, so that a certain welding gap is formed between the welding area of the optical lens and the welding area of the spectacle frame and is welded and fixed by low-temperature metal solder.

The material of the optical lens is glass-ceramic, quartz glass, K9 glass, sapphire, calcium fluoride or zinc selenide.

The frame is made of titanium alloy, 4J32, 4J36 and other low-expansion precision alloys, aluminum alloys and aluminum-based composite materials, or other metal materials that match the expansion coefficient of the lens.

Preferably, the structure of the frame includes a through hole in the middle part adapted to the geometric shape and size of the lens, and one end of the through hole is a chamfer for solder drainage to ensure that the solder fully contacts the frame and wets the frame, and flows into the chamfered surface. Solder seam; the other end of the through hole is a solder diversion groove, which can be used to store excess solder and avoid excessive accumulation of solder in the welding seam area and cause stress; the edge of the solder diversion groove at the other end of the through hole is a lens positioning step, which is used as the lens and the lens. The supporting edge when the frame is welded and used to ensure the parallelism of the lens and the frame.

On the other hand, the present invention also provides a sealing method for an optical component with high surface shape precision, which is characterized in that it includes the following steps:

① Prepare optical lenses and frames:

There is a through hole in the middle of the frame, and the aperture of the through hole matches the outer diameter of the optical lens, for the optical lens to be embedded;

One end of the through hole is provided with a solder drainage chamfer, and the solder drainage chamfer is used to make the solder flow into the welding seam along the chamfered surface to ensure that the solder is fully contacted with the frame and wets the frame;

The other end of the through hole is provided with a solder diversion groove and a lens limit step. The solder diversion groove is used to store excess solder and serve as the welding end when the lens and the frame are welded to avoid excessive solder. Accumulation produces stress; the steps are used to limit the position of the optical lens, and serve as the supporting edge when the lens and the frame are welded to ensure the parallelism of the lens and the frame;

②Optimize processing of the optical lenses and frames:

shielding and protecting the light-transmitting surface of the optical lens, and metallizing the outer circumferential surface of the optical lens to form a metallized layer, which is used as the welding area of the optical lens;

Surface modification treatment is performed on the peripheral surface of the through-hole welding end of the mirror frame, the chamfered surface of the solder drainage and the surface of the solder drainage groove;

③ Prepare low melting point metal solder and clean it before soldering;

④ Embed the metallized optical lens into the surface-modified frame, place the solder on the chamfer of the frame, and carry out welding treatment, so that the welding area of the frame is welded with the metallized film layer of the welding area of the optical lens through the metal solder. Combined, the optical component with high surface shape precision is completed.

Preferably, the soldering process is eutectic reflow soldering.

Preferably, the welding process is gas shielded welding, and the shielding gas used may be a reducing gas such as formic acid and hydrogen.

Preferably, the surface modification treatment refers to plating a Ni/Au film layer on the surface of the mirror frame by an electroplating method.

Preferably, the coating method of the metallization treatment adopts one or a combination of two or more of vacuum evaporation coating, sputtering coating, and ion coating, and the film system is generally Ti/Ni/Au.

Preferably, the low melting point metal solder is indium solder.

The thermal expansion coefficient α ₁ of the optical lens and the thermal expansion coefficient of the metal frame are α ₂ . According to the different materials of the optical lens (1), the metal frames of different materials are matched, and the matching principle is α ₁ <α ₂ , in this principle On the basis, the metal material with the expansion coefficient as close as possible to the optical lens is selected as the frame, so as to effectively reduce the residual stress of the optical components after welding.

Compared with the prior art, the beneficial effects of the present invention are:

1. There is a gap fit between the optical lens and the frame using this welding method to prevent the lens from being subjected to mechanical force;

2. After welding, use low-temperature metal solder-indium solder to fill the gap between the optical lens and the metal frame to form a flexible transition layer, so that the optical lens can expand and contract freely in different temperature fields without Constrained, it can effectively alleviate the residual stress problem caused by the difference in thermal expansion coefficient between the lens and the frame during the welding process and use, so as to avoid the large change of the lens surface shape; finally, the melting point of indium solder is only 157 ℃, and the required welding temperature is higher Low, the surface shape of the lens will not be affected due to high temperature, and the lower welding temperature is more friendly to the optical film coated on the surface of the optical lens.

3. The optical assembly prepared by sealing with indium solder has good air tightness and excellent anti-aging performance in the welding area. Compared with the glued optical assembly, the welding strength is higher.

Description of drawings

FIG. 1 is a schematic structural diagram of an embodiment of a high-surface-precision optical component and a metal mirror frame of the present invention.

2 is a schematic diagram of an optical component with high surface precision in the present invention, wherein (a) is an optical lens with high surface precision; (b) is a metal frame with a circular or oval through hole in the middle.

Detailed ways

The present invention will be further described below with reference to the embodiments and accompanying drawings, but the protection scope of the present invention should not be limited by this.

Please refer to FIG. 1 and FIG. 2 respectively. FIG. 1 is a schematic structural diagram of an embodiment of a high-surface-precision optical component and a metal mirror frame of the present invention, and FIG. 2 is a schematic diagram of a high-surface-precision optical component of the present invention. As can be seen from the figure, the structure of the high surface precision optical component includes a lens 1 and a frame 2. The S3 circumferential surface of the lens 1, that is, the welding area a, is metallized, and the welding area b of the frame 2, the solder drainage chamfer surface and the solder The surface of the diversion groove has been surface-modified, and the welding area a of the lens 1 and the welding area b of the lens frame 2 are sealed with low-temperature metal solder. The inner diameter of the through hole is larger than the outer diameter of the lens 1. During the reflow soldering process, after the solder is liquefied, the chamfering of the solder along the frame 2 is filled in the gap between the frame 2 and the lens 1, and the gap between the frame 2 and the lens 1 is filled. A soft metal solder layer is formed in the annular gap between the two, which can relieve the residual stress caused by the mutual restriction after the two are thermally expanded and deformed during the welding process, so that the deformation of the lens 1 after welding is maintained at a minimum value. That is, the lens 1 still has high surface shape accuracy after being assembled and welded.

The concrete operation steps of the present invention are as follows:

First, the lens and frame are processed according to the design drawings, and the surface of the lens can be coated with a certain optical film or uncoated optical film;

Clean the lens and frame separately before plating;

Cover the light-transmitting surface of the lens with polyimide tape or special fixtures, and only expose the S3 circumferential surface, that is, the welding area a (see Figure 2 in the manual: welding area a), and then put it into the magnetron sputtering coating In the machine, magnetron sputtering coating metallization is carried out. The metallized film layer of magnetron sputtering coating has three layers. First, the active material Ti, which can be closely combined with the surface of the lens, is used as the primer layer, which acts as a link between the non-metallic lens and the subsequent metal film layer. The thickness is about 30-50nm; then as a barrier layer for the interaction between the solder and the film layer, in this embodiment, the material of this layer is Ni or Cr, with a thickness of about 500nm, and finally an Au layer is plated, which can be better than the low-temperature metal solder indium Wet, about 1 μm thick. The total thickness of the metallized film layer coated by magnetron sputtering is 1-2 μm;

The frame is cleaned and electroplated, the film is generally Ni/Au, and the total thickness of the film is not less than 2μm;

The indium solder is cleaned before soldering, generally by pickling, and then the solder is prepared into a ring shape that matches the circumference of the frame;

Nest the frame on the outside of the circumference of the lens S3, cover the lens with a thin aluminum sheet whose size matches the outer diameter of the lens, as a protective device for the lens, then place the indium solder ring on the chamfer of the frame, and finally The assembled products to be soldered are placed in a reflow oven, and reflow soldering is performed under the protection of a reducing atmosphere.

Example

The ZYGO interferometer was used to test the original surface shape of the sapphire lens, and the RMS values of the 0° reflective surfaces of the A and B surfaces were 0.078λ and 0.010λ (λ=632.8nm), respectively; then the S1 and S2 clear surfaces of the sapphire lens were measured. Cover it up, put it into a magnetron sputtering coating machine, and perform magnetron sputtering metallization on the S3 circumferential surface, that is, the welding area a. First, the Ti layer is plated for 0.5h, and then the Ni layer is plated for 1h. , and the Au layer was finally plated for 2h; then ZYGO interferometer was used to test the reflective surface shape of the metallized sapphire lens. =632.8nm);

After cleaning the TC4 frame, carry out surface modification treatment on the welding area b, the chamfered surface of the solder drainage and the groove surface of the solder drainage, that is, first remove the oxide layer on the surface of the TC4 frame, and then use electroplating on its surface. The Ni/Au layer is plated, and the total thickness of the film layer is not less than 3 μm; then the indium solder is cleaned with dilute hydrochloric acid, and the volume of the weld is calculated according to the size of the frame and lens. It is prepared into a circular solder ring, and the metallized sapphire lens is assembled in the metallized and modified TC4 titanium alloy frame, and then the solder ring is placed at the chamfer of the frame, and finally the assembled sample to be welded is placed. Into the reflow soldering furnace, soldering is performed under the protection of formic acid gas.

After welding, the welding area a of the sapphire lens and the welding area b of the TC4 frame are connected together by indium solder, and the sapphire-TC4 titanium alloy optical assembly is completed. The optical components formed by indium solder sealing between the sapphire lens and the TC4 frame were again used to test the surface shape of the sapphire lens with a ZYGO interferometer. The RMS values of the 0° reflective surfaces of the A and B surfaces were 0.070λ and 0.012 respectively. λ, that is, the RMS value change of the 0° reflective surface shape of the sapphire lens A and B surfaces caused by the entire process of the optical component prepared by the welding method of the patent of the present invention is 0.008λ and 0.002λ respectively, far less than 1/50λ. That is to say, the optical components prepared by indium solder sealing have very little surface shape change of the optical lens, and can maintain a high surface shape accuracy that is very close to the original surface shape before welding.

The present invention provides an optical component with high surface shape precision and a sealing method thereof. Compared with the original surface shape, the surface shape precision of the prepared optical component has an extremely small amount of change, and undergoes changes in welding temperature and structure after welding. The rear optical elements can still maintain extremely high surface shape accuracy, so the optical components prepared by the high surface shape precision optical component sealing method described in this patent can be applied to optical remote sensors, optical resonators and other precision optical systems.

Claims (11)

1. A high surface shape precision optical component comprises an optical lens (1) and a spectacle frame (2), which is characterized in that,

the optical lens (1) is a circular or elliptical optical element with a certain thickness and high surface shape precision, and the light passing surface S1 or S2 of the optical lens reflectsSurface shape precision PV ₀ Better than 1/10 lambda @632.8nm RMS ₀ Better than 1/20 lambda; the outer circumferential surface or elliptical circumferential surface S3 of the optical lens (1) is an optical lens welding area (a);

the middle part of the spectacle frame (2) is provided with a through hole, and the aperture of the through hole is matched with the outer diameter of the optical lens (1) for the optical lens to be embedded; one end of the through hole is provided with a solder drainage chamfer, the other end of the through hole comprises a solder diversion groove and a lens limiting step, and the large circumferential surface of the through hole is a welding area (b) of the spectacle frame;

the spectacle frame (2) is nested on the outer circumference of the optical lens (1), so that a certain welding gap is formed between the welding area (a) of the optical lens and the welding area (b) of the spectacle frame, and the spectacle frame is welded and fixed through low-temperature metal solder.

2. The optical assembly with high surface shape precision as claimed in claim 1, wherein the material of the optical lens (1) is microcrystalline glass, quartz glass, K9 glass, sapphire, calcium fluoride or zinc selenide.

3. The optical assembly of claim 1, wherein the frame (2) is made of titanium alloy, low expansion precision alloy such as 4J32, 4J36, aluminum alloy and aluminum matrix composite material or other metal material with expansion coefficient matched with that of the lens (1).

4. A high surface profile precision optical assembly as claimed in claim 1, wherein the structure of the frame (2) comprises a through hole with a middle part adapted to the geometry and size of the lens, and one end of the through hole is provided with a solder drainage chamfer to ensure that the solder is fully contacted with the frame and wets the frame, and flows into the welding seam along the chamfer; the other end of the through hole is provided with a solder diversion groove which can be used for storing redundant solder and avoiding stress generated by excessive accumulation of the solder in the welding seam area; the edge of the solder flow guide groove at the other end of the through hole is a lens positioning step which is used as a bearing edge when the lens is welded with the spectacle frame and is used for ensuring the parallelism of the lens and the spectacle frame.

5. A sealing method of a high surface shape precision optical component is characterized by comprising the following steps:

(1) preparation of optical lenses and frames:

the middle part of the spectacle frame is provided with a through hole, and the aperture of the through hole is matched with the outer diameter of the optical lens and is used for the optical lens to be embedded;

one end of the through hole is provided with a solder drainage chamfer angle for enabling solder to flow into a welding seam along the chamfer angle surface, so that the solder is ensured to be fully contacted with the mirror bracket and wet the mirror bracket;

the other end of the through hole is provided with a lens limiting step and a solder diversion groove: the step is used for limiting the optical lens and is used as a bearing edge when the lens is welded with the spectacle frame, so that the parallelism between the lens and the spectacle frame is ensured; the solder diversion groove is used for storing redundant solder to avoid stress caused by excessive accumulation of the solder;

(2) optimizing the optical lens and frame:

shielding and protecting the light passing surface of the optical lens, and carrying out metallization treatment on the outer circumferential surface of the optical lens to form a metallization layer serving as an optical lens welding area;

carrying out surface modification treatment on the circumferential surface of the through hole of the mirror bracket, the solder drainage chamfer surface and the solder diversion groove surface;

(3) preparing low-melting-point metal solder, and cleaning before welding;

(4) and embedding the metallized optical lens into the mirror frame with the modified surface, placing a welding flux at the chamfer of the mirror frame, and performing welding treatment to ensure that the welding area (b) of the mirror frame is welded and combined with the metallized film layer in the welding area (a) of the optical lens through the metal welding flux, thereby completing the manufacture of the optical assembly with high surface shape precision.

6. A method of sealing a highly surface-shaped precision optical module as recited in claim 5, wherein the soldering process is eutectic reflow soldering.

7. A method of sealing an optical assembly with a high surface accuracy as claimed in claim 5 or 6, wherein the soldering process is gas-shielded soldering, and the shielding gas used can be a reducing gas such as formic acid or hydrogen.

8. A method of sealing a high surface precision optical module as claimed in claim 5, wherein the surface modification treatment is plating of Ni/Au film on the surface of the frame by electroplating.

9. A method of sealing a high surface accuracy optical package as claimed in claim 5, wherein the metallization is performed by one or a combination of vacuum evaporation, sputtering, and ion plating, and the film is Ti/Ni/Au.

10. A method of sealing a highly surface-shaped accurate optical package as recited in claim 5, wherein said low melting point metal solder is indium solder.

11. A method of sealing a high surface profile precision optical package as claimed in claim 5, wherein the optical lens has a thermal expansion coefficient α ₁ The frame has a coefficient of thermal expansion of alpha ₂ And α is ₁ ≤α ₂ 。

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