Fabrication of a diffractive optical element by the precision diamond micro-turning method
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-05-18 |
| Journal | Interexpo GEO-Siberia |
| Authors | Nikita A. Gurin |
| Institutions | Institute of Automation and Electrometry |
| Analysis | Full AI Review Included |
Technical Analysis & Documentation: Precision Diamond Micro-Turning
Section titled âTechnical Analysis & Documentation: Precision Diamond Micro-TurningâExecutive Summary
Section titled âExecutive SummaryâThis document analyzes the research on fabricating diffractive optical elements (DOEs) using Precision Diamond Micro-Turning (PDM). The core finding validates PDM as a superior manufacturing technology for complex optical surfaces, relying critically on ultra-high-quality diamond cutting tools.
- Core Achievement: Successful fabrication of a 52-zone Fresnel diffractive lens structure on a polymer (PMMA) substrate using PDM.
- Precision Requirement: The PDM process necessitates specialized single-crystal diamond (SCD) cutters with precisely calculated geometry (e.g., 60° included angle, 0.01 mm radius) to achieve the required microstructure.
- Surface Quality: PDM significantly outperforms conventional machining, achieving surface roughness (Ra) as low as 0.012 nm, essential for high-performance optics and IR applications.
- Application Scope: The technology is applicable to metal optics (Al, Cu mirrors), complex aspheres (up to 250 mm diameter), and kinoform elements for infrared (IR) systems (Ge, Si, ZnSe).
- 6CCVD Value Proposition: 6CCVD supplies the necessary high-purity, low-defect Single Crystal Diamond (SCD) material required to manufacture these ultra-precision cutting tools, ensuring maximum edge retention and tool life.
- Technological Advantage: PDM allows for the simultaneous creation of flat, spherical, aspherical, and diffractive structures in a single, continuous process, minimizing alignment errors.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the analysis of the PDM process and resulting optical element requirements:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Achievable Surface Roughness (PDM) | 0.012 | nm | Best-case scenario for ultra-precision turning. |
| Target Surface Roughness (Metal Optics) | < 2 | nm | Required for metallic mirrors (Al, Cu). |
| Diffractive Lens Zones (N) | 52 | - | Total number of Fresnel zones fabricated. |
| Maximum Step Height | 425.64 | Âľm | Total depth of the diffractive structure. |
| Zone Width (Minimum) | 0.5 | mm | Width of the Fresnel zones. |
| Tool Radius (R) | 0.01 | mm | Critical parameter for the specialized diamond cutter. |
| Tool Included Angle | 60 | ° | Geometry of the diamond cutting edge. |
| Conic Clearance Angle | 20 | ° | Clearance angle set for the diamond tool. |
| Maximum Part Diameter | 250 | mm | Capability of the PDM equipment for aspheric parts. |
Key Methodologies
Section titled âKey MethodologiesâThe fabrication of the diffractive optical element relies on a highly controlled, multi-stage process utilizing specialized equipment and high-precision diamond tooling:
- Preparatory Stage: Tool Selection and Fixturing:
- Selection of a specialized diamond cutter (tool) with a precise offset angle relative to the calculated sawtooth microstructure of the diffractive element.
- Preparation of necessary fixturing (e.g., vacuum chuck made of D16 aluminum alloy) and fasteners.
- The vacuum chuck is first machined using a classical tool to match the radius of the PMMA optical blank.
- Tool Replacement and Alignment:
- The classical tool is replaced with the specialized diamond cutter.
- The diamond tool performs three passes on the vacuum holder to eliminate surface roughness.
- The PMMA blank is secured via vacuum clamping and positioned using a micron indicator head to minimize runout.
- Software Input and Simulation:
- Parameters for the Fresnel lens zones (e.g., 52 zones, 0.5 mm width, 425.64 Âľm max step) are entered into the computer software.
- Parameters of the diamond cutter (e.g., 0.01 mm radius, 60° included angle) are input from the manufacturerâs documentation.
- The machine calculates the path and depth for each zone pass.
- Surface Preparation and Machining:
- The optical blank surface is flattened (âkosinaâ) by the diamond tool to ensure planarity meets design specifications.
- The final diffractive lens structure is machined using the âfinishingâ (вŃŃ Đ°ĐśĐ¸Đ˛Đ°Đ˝Đ¸Ń) method.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe success of Precision Diamond Micro-Turning hinges entirely on the quality and geometric stability of the diamond cutting tool. 6CCVD specializes in the production of high-purity MPCVD diamond, which is the ideal material for manufacturing these critical tools.
Applicable Materials for Tool Manufacturing
Section titled âApplicable Materials for Tool ManufacturingâTo replicate or extend this research, particularly for achieving the required Ra < 0.012 nm surface finish and maintaining the sharp edge required for sawtooth structures, Optical Grade Single Crystal Diamond (SCD) is essential.
| 6CCVD Material | Application in PDM Research | Key Benefit |
|---|---|---|
| Optical Grade SCD | Manufacturing the ultra-precision cutting tool (cutter). | Highest purity, maximum hardness, superior wear resistance, and ability to hold an atomically sharp edge (critical for Ra < 0.012 nm). |
| SCD Substrates | High-stability mounting platforms or heat sinks for PDM equipment. | Excellent thermal conductivity and mechanical stability, minimizing vibration and thermal drift during machining. |
| PCD Plates | Potential for lower-cost, high-wear inserts for roughing passes (if applicable). | High toughness and large area availability (up to 125 mm). |
Customization Potential
Section titled âCustomization PotentialâThe paper highlights the necessity of using specialized diamond cutters with unique geometries (e.g., 60° included angle, specific radius). 6CCVD provides the foundational material and engineering services to support the creation of these custom tools and integrated systems:
- Custom Dimensions: 6CCVD can supply SCD plates up to 500 Âľm thick, suitable for grinding into custom tool inserts, or thicker substrates (up to 10 mm) for mounting blocks.
- Ultra-Low Roughness: Our internal polishing capability achieves Ra < 1 nm on SCD, providing an ideal starting material for tool manufacturers who require the highest possible surface quality before final edge grinding.
- Custom Metalization: For integrating the diamond tool into specialized holders or for thermal management, 6CCVD offers in-house metalization services (Au, Pt, Pd, Ti, W, Cu) to ensure robust bonding and electrical contact.
- Large Area PCD: For future scaling of PDM to larger components (the paper mentions up to 250 mm diameter), 6CCVD can supply large-area PCD wafers up to 125 mm.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team possesses deep expertise in diamond material science and its application in high-precision manufacturing. We can assist engineers and researchers with:
- Material Selection: Consulting on the optimal SCD grade (Type IIa) required for achieving maximum tool life and edge quality in ultra-precision machining of materials like PMMA, Ge, Si, and metal alloys.
- Integration Support: Advising on metalization schemes for mounting diamond inserts into tool holders, ensuring thermal stability and mechanical rigidity during the high-speed turning process.
- Extension of Research: Supporting projects focused on extending PDM technology to new materials, such as direct machining of diamond substrates for advanced X-ray or UV optics.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. Global shipping (DDU default, DDP available) ensures rapid delivery of critical materials worldwide.
View Original Abstract
The paper considers the manufacturing process of a diffractive optical element by precision diamond micro-turning using a diffractive lens as an example. The process consists of a preparatory stage and the stage of manufacturing a given diffractive element on specialized equipment with computer program control. The preparatory stage includes selection of a special diamond cutter with a response offset of the cutter angle relative to the calculated microstructure of the diffractive element, the preparation and manufacture of the necessary equipment, including fasteners, with the help of which the optical part is installed and adjusted, on the surface of which a diffractive lens is formed. After that, the specified values of the parameters of the lens zones, the values of the parameters of the diamond cutter are entered into the computer software, and the process of manufacturing a diffractive lens is started.