A method for processing a curved blazed grating

Abstract

The application discloses a kind of processing methods of curved surface blazed grating, the method of the present application comprises: the workpiece to be processed is installed on the fixture of machine tool, the fixture is arranged on the side of main shaft C of machine tool, and main shaft C is arranged on the X-axis slide plate of machine tool, and adjust main shaft C to dynamic balance;The rotary motion of workpiece is used as main cutting motion, combined with the linkage deflection angle of tool, and the R-shaped diamond tool with larger tool tip arc radius is used to process curved surface base on workpiece;The rotary motion of workpiece is used as main cutting motion, combined with the linkage deflection angle of tool, and the V-shaped diamond tool with smaller tool tip arc radius is used to process curved surface grating on curved surface base, to obtain curved surface blazed grating.The present application has the advantages of high processing efficiency, high dimensional accuracy and good structural uniformity, and can effectively enhance the reflection and diffraction function of optical elements.

Description

Technical Field

[0001] The present invention relates to microstructure processing technology, and in particular to a processing method of a curved blazed grating. Background Art

[0002] Microstructured functional surfaces are widely used in advanced science and industry due to their excellent performance, but their performance is limited by the surface quality of their manufacturing methods. Structured surfaces are categorized as continuous and discontinuous. Continuous structures are those without sharp edges (e.g., wavy and sinusoidal structures), while others are discontinuous (e.g., V-groove arrays and blazed gratings). These optical elements can be used to improve optical performance, such as beam shaping, light guiding, and focusing, while also increasing reflectivity and enhancing diffraction effects.

[0003] At present, there are mainly the following methods for preparing blazed gratings: mechanical ruling method, electron beam direct writing method and holographic ion beam etching method. Holographic ion beam etching method is the most mature and widely used method for preparing blazed gratings. For example, Chinese patent document with application number 201010169360.6 discloses a reactive ion beam etching method for blazed convex gratings; for another example, Chinese patent document with application number 201210035381.8 discloses a convex blazed grating ion beam etching method; for another example, Chinese patent document with application number 202011186785.8 discloses a convex double blazed grating preparation method, device and convex double blazed grating, also using ion beam etching; for another example, US patent document US10338285B2 uses ion beam etching to prepare planar blazed diffraction gratings. However, the ion beam etching method has no advantages in the production of blazed gratings with low line density. At the same time, the axial limitations and the need for beam modulation in the ion beam etching device limit its ability to produce blazed gratings on freer structures. At present, the only international laboratory that can use electron beam direct writing to produce convex blazed gratings with high diffraction efficiency is the Jet Propulsion Laboratory (JPL) in the United States. The production of blazed gratings using electron beam direct writing technology is technically complex and requires professional and expensive hardware and software equipment. It has obvious advantages in the production of blazed gratings with ultra-high line density, as described in U.S. Patent Document US8331027B2. However, this technology is generally limited to the production of convex gratings with a large radius of curvature or close to a plane, and still lacks flexibility for non-planar features. Mechanical scribing is often used for planar blazed gratings, and is a discontinuous structured surface. For example, U.S. Patent Documents US9233512B2 and US9678253B2 use mechanical scribing machines to produce planar blazed diffraction gratings.

[0004] In summary, for curved blazed gratings with low line density, high precision requirements and low cost, it is necessary to seek a new processing method to solve the above problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: In response to the above-mentioned problems of the prior art, a method for processing a curved blazed grating is provided, which has high processing efficiency, high dimensional accuracy, good structural uniformity, and can effectively enhance the reflection and diffraction functions of optical elements.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for processing a curved blazed grating, comprising:

[0008] S1. Mount the workpiece to be processed on the fixture of the machine tool. The fixture is arranged on the side of the main spindle C of the machine tool. The main spindle C is arranged on the X-axis slide of the machine tool, and the main spindle C is adjusted to dynamic balance;

[0009] S2, using the workpiece's rotational motion as the main cutting motion, combined with the tool's linkage deflection angle, and using an R-shaped diamond tool with a large tool tip radius to machine the curved surface base on the workpiece;

[0010] S3. The workpiece's rotational motion is used as the main cutting motion. Combined with the tool's linkage deflection angle, a V-shaped diamond tool with a small tool tip radius is used to machine a curved grating on a curved substrate, thereby obtaining a curved blazed grating.

[0011] Optionally, the dynamic balancing in step S1 means that when the rotation speed of the spindle C is 500-1500 rpm, the radial runout peak-to-valley value PV is stable between 2-10 nm.

[0012] Optionally, adjusting the main shaft C to be dynamically balanced in step S1 refers to adjusting the main shaft C to be dynamically balanced by replacing the number of balancing screws.

[0013] Optionally, the R-shaped diamond tool with a larger tool tip arc radius in step S2 has a tool tip arc radius of 0.2 to 0.5 mm, and a tool tip angle of 90° to 110°; and in the process of processing the curved surface base: the tool angle does not deflect, the tool tip follows the curved surface contour and feeds along the Z-axis direction, and is linked with the workpiece in the X-axis direction, the spindle speed is 500 to 1500 rpm, the feed amount along the Z-axis is 1 to 2 μm, non-aqueous coolant is used for cooling, the cutting environment temperature is maintained within ±0.1°C, and the curved surface base is processed by three-axis linkage; wherein the Z-axis direction is the axial direction of the spindle C.

[0014] Optionally, step S2 includes:

[0015] S2.1, based on the surface equation of the curved blazed grating and the tool tip radius of an R-shaped diamond tool with a larger tool tip radius, calculate the tool tip position coordinates and tool deflection angle value, perform path planning based on the calculated tool tip position coordinates and tool deflection angle value, and generate CNC machining code for the curved surface substrate;

[0016] S2.2, using the curved base CNC machining code to control an R-shaped diamond tool with a large tool tip radius to perform rough machining of the curved base on the workpiece, while retaining a cutting allowance and a rough machining cutting depth of 5 to 10 μm;

[0017] S2.3, using CNC machining code to control an R-shaped diamond tool with a large tool tip arc radius to perform fine machining of the curved surface base on the workpiece, and the fine machining cutting depth is 1 to 2 μm.

[0018] Optionally, the tip arc radius of the V-shaped diamond tool with a smaller tip arc radius in step S3 is 0.1~0.2μm, the tip angle is 90°~110°, and in the process of processing the curved surface grating: the tool angle is always deflected along the B-axis direction, and at the same time follows the surface contour to feed along the Z-axis direction, and is linked with the workpiece in the X-axis direction. The cutting depth is the grating height calculated according to the grating equation, the spindle speed is 500~1500rmp, the feed amount along the Z-axis is based on the grating period calculated according to the grating equation, non-aqueous coolant is used for cooling, and the cutting environment temperature is maintained within ±0.1℃, and the curved surface grating processing is completed by four-axis linkage.

[0019] Optionally, step S3 includes:

[0020] S3.1, calculating the tool tip position coordinates and tool deflection angle value based on the surface equation and grating equation of the curved blazed grating, performing path planning based on the calculated tool tip position coordinates and tool deflection angle value, and generating the curved blazed grating CNC machining code;

[0021] S3.2, through the CNC machining code of the curved blazed grating, a V-shaped diamond tool with a small tool tip arc radius is controlled to form and machine the curved grating in one step.

[0022] Optionally, the surface equation of the curved blazed grating is a surface equation with rotational symmetry, and the function expression of the grating equation is:

[0023] d(sinθ i +sinθ k )=kλ,

[0024]

[0025] In the above formula, d is the grating period, θ i is the angle of incidence, θ kis the diffraction angle, k is the diffraction order, λ is the grating wavelength, h is the grating height, θ a is the grating apex angle, θ b The shining angle.

[0026] Optionally, step S3 also includes detecting the surface accuracy of the curved grating on the curved blazed grating. If the surface accuracy of the curved grating does not meet the requirements, jump to step S1) or step S2 to continue processing; otherwise, it is determined that the surface accuracy of the curved grating is processed, and the process ends and exits.

[0027] Optionally, the condition for jumping to step S1 is that when detecting the surface accuracy of the curved grating, the curved blazed grating is removed from the fixture for non-in-situ detection, and the condition for jumping to step S2 is that when detecting the surface accuracy of the curved grating, the curved blazed grating is kept on the fixture for in-situ detection.

[0028] Compared with existing technologies, the present invention has the following major advantages: Electron beam lithography and holographic ion beam etching are common processing technologies for currently common planar gratings and convex spherical gratings. However, for curved blazed gratings, these two methods lack flexibility and, when the grating density is relatively small, they suffer from limited precision and low processing efficiency. Based on this, the present invention utilizes single-point diamond technology and a specialized fixture. By utilizing workpiece rotation and tool deflection, the curved substrate and curved grating are processed sequentially, improving processing efficiency, controlling processing precision, and achieving improved structural uniformity. The present invention offers the advantages of high processing efficiency, high dimensional accuracy, and good structural uniformity, effectively enhancing the reflection and diffraction functions of optical components. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart of the method for processing a curved blazed grating according to an example of the present invention.

[0030] Figure 2 Schematic diagram of curved substrate processing in an example of the present invention.

[0031] Figure 3 Schematic diagram of tool position for initial processing of curved surface grating in an example of the present invention.

[0032] Figure 4 Schematic diagram of tool position for completing the processing of curved surface grating in an example of the present invention.

[0033] Figure 5 This is the local contour map of the curved grating finally obtained in the example of the present invention.

[0034] Figure 6 This is the surface quality result of the curved grating finally obtained in the example of the present invention.

[0035] Figure 7 This is the final curved grating surface result obtained in the example of the present invention. DETAILED DESCRIPTION

[0036] The following will take a curved grating with a diameter of 14 mm as an example of a processing workpiece to further explain in detail the processing method of the curved blazed grating of the present invention.

[0037] like Figure 1 As shown, the processing method of the curved blazed grating in this embodiment includes:

[0038] S1. Mount the workpiece to be processed on the fixture of the machine tool. The fixture is arranged on the side of the main spindle C of the machine tool. The main spindle C is arranged on the X-axis slide of the machine tool, and the main spindle C is adjusted to dynamic balance;

[0039] S2, using the workpiece's rotational motion as the main cutting motion, combined with the tool's linkage deflection angle, and using an R-shaped diamond tool with a large tool tip radius to machine the curved surface base on the workpiece;

[0040] S3. The workpiece's rotational motion is used as the main cutting motion. Combined with the tool's linkage deflection angle, a V-shaped diamond tool with a small tool tip radius is used to machine a curved grating on a curved substrate, thereby obtaining a curved blazed grating.

[0041] The processing processes mentioned in the processing method of the curved blazed grating in this embodiment are all based on single-point diamond turning technology (Single Point Diamond Tool, SPDT), which utilizes the synchronous movement of multiple axes of ultra-precision machine tools to accurately control the position of the tool-workpiece interaction according to the geometric requirements of the curved grating, and can flexibly manufacture a curved blazed grating structure on a curved substrate.

[0042] In this embodiment, dynamic balancing in step S1 means that when the rotation speed of the spindle C is 500-1500 rpm, the radial runout peak-to-valley value PV is stabilized between 2 and 10 nm. In step S1, the spindle C is adjusted to dynamic balance by a feasible adjustment method as needed. For example, as an optional implementation method, in step S1 of this embodiment, the spindle C is adjusted to dynamic balance by replacing the number of balancing screws to adjust the spindle C to dynamic balance. Moreover, adjusting the spindle C is a closed-loop process. When the rotation speed of the spindle C is 500-1500 rpm, it is necessary to adjust and test the radial runout peak-to-valley value PV at the same time until the condition that the radial runout peak-to-valley value PV is stabilized between 2 and 10 nm is met, and it can be determined that dynamic balance is achieved.

[0043] In this embodiment, the radius of the R-shaped diamond tool with a larger tool tip arc radius in step S2 is 0.2-0.5 mm, and the tool tip angle is 90°-110°; and in the process of machining the curved surface base: Figure 2 As shown, the tool angle remains unchanged, the tool tip follows the surface contour along the Z-axis, and is linked to the workpiece in the X-axis direction. The spindle speed is 500-1500 rpm, the feed along the Z-axis is 1-2 μm, and non-aqueous coolant is used for cooling. The cutting environment temperature is maintained within ±0.1°C. The curved base is machined through the linkage of the X, Z, and C axes; the Z-axis direction is the axis direction of the spindle C. Non-aqueous coolants can be oil mist, alcohol mist, IPA mist, etc., and the cutting environment temperature is maintained within ±0.1°C through the air conditioning cooling system.

[0044] In this embodiment, step S2 includes:

[0045] S2.1. Calculate the tool tip position coordinates and tool deflection angle based on the surface equation of the curved blazed grating and the tool tip radius of an R-shaped diamond tool with a larger tool tip radius. Path planning is performed based on the calculated tool tip position coordinates and tool deflection angle values, and the NC machining code for the curved surface base is generated. The function expressions for the tool tip position coordinates and tool deflection angle values ​​are:

[0046] Z n =(n-1)*z,

[0047] X n =sqrt(R 2 -(Z n -ZO) 2 )+XO+r,

[0048] B n =0,

[0049] Among them, (Z n ,X n ) is the tool tip position coordinate of the nth blazed grating, B n is the tool deflection angle value of the nth blazed grating, z is the Z-axis feed, sqrt is the square root function, (ZO, XO) is the coordinate of the center of the circle corresponding to the curvature radius R of the surface base, R is the curvature radius of the surface base, and r is the radius of the tool tip arc.

[0050] S2.2, using the curved base CNC machining code to control an R-shaped diamond tool with a large tool tip radius to perform rough machining of the curved base on the workpiece, while retaining a cutting allowance and a rough machining cutting depth of 5 to 10 μm;

[0051] S2.3, using CNC machining code to control an R-shaped diamond tool with a large tool tip arc radius to perform fine machining of the curved surface base on the workpiece, and the fine machining cutting depth is 1 to 2 μm.

[0052] In this embodiment, the V-shaped diamond tool with a smaller tool tip radius in step S3 has a tool tip radius of 0.1 to 0.2 μm, a tool tip angle of 90° to 110°, and in the process of processing the curved surface grating: Figure 3 and Figure 4 As shown, the tool angle is always deflected along the B-axis, while feeding along the Z-axis following the surface contour, and cooperating with the workpiece in the X-axis direction. The cutting depth is the grating height calculated according to the grating equation. The spindle speed is 500-1500 rpm, and the feed rate along the Z-axis is based on the grating period calculated by the grating equation. Non-aqueous coolant is used for cooling, and the cutting environment temperature is maintained within ±0.1°C. The surface grating is processed by the linkage of the X-axis, Z-axis, C-axis, and B-axis. Similarly, non-aqueous coolant can be oil mist, alcohol, IPA mist, etc., and the cutting environment temperature is maintained within ±0.1°C by the air conditioning cooling system.

[0053] In this embodiment, step S3 includes:

[0054] S3.1. Calculate the tool tip position coordinates and tool deflection angle based on the surface equation and grating equation of the curved blazed grating. Perform path planning based on the calculated tool tip position coordinates and tool deflection angle values ​​and generate the curved grating CNC machining code. The function expressions for the tool tip position coordinates and tool deflection angle values ​​are:

[0055] Z n =(n-1)d,

[0056] (Z n -ZO) 2 +(X n -XO) 2 =(Rh) 2 ,

[0057]

[0058] Among them, (Z n ,X n ) is the tool tip position coordinate of the nth blazed grating, B n is the tool deflection angle value of the nth blazed grating, d is the grating period, (ZO, XO) is the coordinate of the center of the circle corresponding to the radius of curvature R of the curved surface base, R is the radius of curvature of the curved surface base, h is the grating height, β is the tool tip angle, (Z n+1 ,X n+1 ) is the tool tip position coordinate of the n+1th blazed grating, θ b The shining angle.

[0059] S3.2, through the CNC machining code of the curved blazed grating, a V-shaped diamond tool with a small tool tip arc radius is controlled to form and machine the curved grating in one step.

[0060] In this embodiment, the surface equation of the curved blazed grating can be an ellipsoidal surface equation, a spherical surface equation, or other surface equations with rotational symmetry. The function expression of the ellipsoidal surface equation is:

[0061]

[0062] The functional expression of the spherical equation is:

[0063] (xa) 2 +(yb) 2 +(zc) 2 =1

[0064] Among them, (x, y, z) are the coordinate points on the surface, and a, b, and c are all related parameters that affect the shape of the surface.

[0065] In this embodiment, the function expression of the grating equation is:

[0066] d(sinθ i +sinθ k )=kλ,

[0067]

[0068] In the above formula, d is the grating period, θ i is the angle of incidence, θ k is the diffraction angle, k is the diffraction order, λ is the grating wavelength, h is the grating height, θ a is the grating apex angle, θ b The shining angle.

[0069] Considering that steps S1 to S3 may not necessarily be able to produce a curved blazed grating that meets the requirements, as a further improvement to the above steps S1 to S3, this embodiment further includes detecting the surface accuracy of the curved grating on the curved blazed grating after step S3. If the surface accuracy of the curved grating does not meet the requirements, then jump to step S1) or step S2 to continue processing, otherwise it is determined that the surface accuracy of the curved grating has been processed, and the process ends and exits. Among them, the surface accuracy of the curved grating can be part or all of the surface accuracy indicators such as surface error, shape accuracy and surface quality. Through iteration, a curved blazed grating that meets the requirements can be processed. In this embodiment, the condition for jumping to step S1 is that when detecting the surface accuracy of the curved grating, the curved blazed grating is removed from the fixture for non-in-situ detection, and the condition for jumping to step S2 is that when detecting the surface accuracy of the curved grating, the curved blazed grating is kept on the fixture for in-situ detection. Finally, the local contour diagram of the curved grating obtained in this embodiment is as shown below. Figure 5 As shown, the surface quality results of the curved grating are as follows Figure 6 As shown, the surface grating shape result is as follows Figure 7 shown.

[0070] In summary, the processing method of the curved blazed grating in this embodiment adopts single-point diamond technology, designs a special fixture, and utilizes workpiece rotation and tool deflection to sequentially realize the processing of the curved substrate and the curved grating, thereby improving the processing efficiency, and the processing accuracy is controllable, and the structural uniformity is better. It has the advantages of high processing efficiency, high dimensional accuracy, and good structural uniformity, and can effectively enhance the reflection and diffraction functions of optical elements.

[0071] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for processing a curved blazed grating, characterized in that: include: S1. Mount the workpiece to be processed on the fixture of the machine tool. The fixture is arranged on the side of the main spindle C of the machine tool. The main spindle C is arranged on the X-axis slide of the machine tool, and the main spindle C is adjusted to dynamic balance; S2, using the workpiece's rotational motion as the main cutting motion, combined with the tool's linkage deflection angle, and using an R-shaped diamond tool with a large tool tip radius to machine the curved surface base on the workpiece; S3, using the rotation of the workpiece as the main cutting motion, combined with the linkage deflection angle of the tool, and using a V-shaped diamond tool with a small tool tip arc radius to machine a curved grating on a curved substrate, thereby obtaining a curved blazed grating; Step S2 includes: S2.

1. Calculate the tool tip position coordinates and tool deflection angle based on the surface equation of the curved blazed grating and the tool tip radius of an R-shaped diamond tool with a larger tool tip radius. Path planning is performed based on the calculated tool tip position coordinates and tool deflection angle values, and the NC machining code for the curved surface base is generated. The function expressions for the tool tip position coordinates and tool deflection angle values ​​are: ， ， ， in,( Z n , X n ) is the n The tool tip position coordinates of the blazed grating, B n For the n The tool deflection angle value of the blazed grating, z is the Z-axis feed, sqrt is the square root function, ( ZO , XO ) is the radius of curvature of the surface base R Corresponding to the center coordinates, R is the radius of curvature of the surface base, r is the tool tip arc radius; S2.2, using the CNC machining code for the curved base, controls an R-shaped diamond tool with a large tool tip radius to perform rough machining of the curved base on the workpiece, retaining the cutting allowance and with a rough machining cutting depth of 5-10 μm; S2.3, using CNC machining code to control an R-shaped diamond tool with a large tool tip radius to perform fine machining of the curved surface base on the workpiece, with a fine machining cutting depth of 1-2 μm; Step S3 includes: S3.

1. Calculate the tool tip position coordinates and tool deflection angle based on the surface equation and grating equation of the curved blazed grating. Perform path planning based on the calculated tool tip position coordinates and tool deflection angle values ​​and generate the curved grating CNC machining code. The function expressions for the tool tip position coordinates and tool deflection angle values ​​are: ， ， ， in,( Z n , X n ) is the n The tool tip position coordinates of the blazed grating, B n For the n The tool deflection angle value of the blazed grating, d is the grating period, ( ZO , XO ) is the radius of curvature of the surface base R Corresponding to the center coordinates, R is the radius of curvature of the surface base, h is the grating height, β is the tool tip angle, ( Z n+1 , X n+1 ) is the n+ The tool tip position coordinates of a blazed grating, θ b For the shining angle; S3.2, through the CNC machining code of the curved blazed grating, a V-shaped diamond tool with a small tool tip arc radius is controlled to form and machine the curved grating in one step.

2. The method for processing a curved blazed grating according to claim 1, wherein: The dynamic balancing in step S1 means that when the spindle C speed is 500-1500 rpm, the radial runout peak-to-valley value PV is stable between 2-10 nm.

3. The method for processing a curved blazed grating according to claim 1, wherein: Adjusting the spindle C to dynamic balance in step S1 refers to adjusting the spindle C to dynamic balance by replacing the number of balancing screws.

4. The method for processing a curved blazed grating according to claim 1, wherein: In step S2, the R-shaped diamond tool with a larger tool tip arc radius has a tool tip arc radius of 0.2~0.5mm, and a tool tip angle of 90°~110°; and in the process of processing the curved surface base: the tool angle does not deflect, the tool tip follows the curved surface contour and feeds along the Z-axis direction, and is linked with the workpiece in the X-axis direction, the spindle speed is 500~1500rpm, the feed amount along the Z-axis is 1~2μm, non-aqueous coolant is used for cooling, the cutting environment temperature is maintained within ±0.1℃, and the curved surface base is processed by three-axis linkage; the Z-axis direction is the axial direction of the spindle C.

5. The method for processing a curved blazed grating according to claim 1, wherein: In step S3, the tool tip arc radius of the V-shaped diamond tool with a smaller tool tip arc radius is 0.1~0.2μm, the tool tip angle is 90°~110°, and in the process of processing the curved surface grating: the tool angle is always deflected along the B-axis direction, and at the same time follows the surface contour. It feeds along the Z-axis direction and is linked with the workpiece in the X-axis direction. The cutting depth is the grating height calculated according to the grating equation, the spindle speed is 500~1500rmp, the feed amount along the Z-axis is based on the grating period calculated according to the grating equation, non-aqueous coolant is used for cooling, and the cutting environment temperature is maintained within ±0.1℃. The curved surface grating processing is completed through four-axis linkage.

6. The method for processing a curved blazed grating according to claim 1, wherein: The surface equation of the curved blazed grating is a surface equation with rotational symmetry. The function expression of the grating equation is: ， ， In the above formula, d is the grating period, θ i is the angle of incidence, θ k is the diffraction angle, k is the diffraction order, λ is the grating wavelength, h is the grating height, θ a is the grating apex angle, θ b The shining angle.

7. The method for processing a curved blazed grating according to claim 1, wherein: After step S3, the process also includes detecting the surface accuracy of the curved grating on the curved blazed grating. If the surface accuracy of the curved grating does not meet the requirements, the process jumps to step S1 or step S2 to continue processing. Otherwise, the process determines that the surface accuracy of the curved grating has been processed, ends, and exits.

8. The method for processing a curved blazed grating according to claim 7, wherein: The condition for jumping to step S1 is that when detecting the surface accuracy of the curved grating, the curved blazed grating is removed from the fixture for non-in-situ detection, and the condition for jumping to step S2 is that when detecting the surface accuracy of the curved grating, the curved blazed grating is kept on the fixture for in-situ detection.

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