THE EVOLUTION OF SPDT: FROM MILITARY ORIGINS TO MODERN OPTICAL PRECISION
Single Point Diamond Turning (SPDT) is a ultra-precision machining technology used to create optical-grade surfaces with nanometer-level smoothness. Originating from advanced military infrared programs, SPDT has evolved into a core process for manufacturing high-precision molds, freeform optics, infrared lenses, and polymer optical components. It remains one of the most important technologies for turning advanced optical designs into reliable, scalable products.
Single Point Diamond Turning (SPDT) is one of the most influential precision-manufacturing technologies in modern optics. From its secretive military beginnings to its central role in today’s freeform and nano-optical era, SPDT has shaped how the world fabricates lenses, molds, and ultra-smooth optical surfaces.
1. Origins: A Technology Born in the Cold War (1960s–1980s)
SPDT first appeared in U.S. defense laboratories during the 1960s. Traditional polishing methods could no longer achieve the accuracy required for infrared guidance systems, satellite sensors, and early night-vision optics. Engineers turned to single-crystal diamond tools to machine metal substrates directly, producing mirror-grade surfaces without any polishing.
This breakthrough enabled:
Mirror-like surfaces cut directly into metal
Sub-micron form accuracy
Surface roughness in the nanometer range
In its earliest years, SPDT was a classified technology used only for strategic military optics.
2. Expansion: From Laboratory Innovation to Industrial Use (1990s–2000s)
By the 1990s, advances in CNC control brought SPDT into commercial optical manufacturing. It quickly became the preferred method for producing plastic lens molds, infrared Fresnel lenses, optical disc masters, and high-precision injection-molding tooling.
This era established SPDT as the foundation of optical-grade polymer manufacturing, achieving:
Form accuracy ≤ 0.3 μm PV
Surface roughness ≤ 10 nm Ra
For the first time, large-scale, high-quality plastic optics became possible.
3. Transformation: Freeform Optics and the New Generation of Optical Design (2010s–present)
As AR/VR systems, automotive sensors, HUD displays, LiDAR modules, and medical imaging devices became more complex, optical design moved beyond simple spherical shapes. Freeform surfaces—non-rotational, highly optimized geometries—became essential.
Traditional polishing could not produce these surfaces. SPDT could.
With multi-axis control and Fast Tool Servo (FTS) technology, modern SPDT machines can sculpt complex 3D optical surfaces in a single continuous cut. Today’s top systems achieve:
Form error ≤ 0.02 μm PV
Surface roughness ≤ 1 nm Ra
Hybrid surfaces combining freeform shapes and micro-structured features
SPDT is no longer just a machining method—it is a platform that enables next-generation optical creativity.
4. Convergence: SPDT in the Era of Meta-Optics
As metalenses and metasurfaces emerged, SPDT found a new mission. While meta-optical devices rely on nanoscale patterns, the master molds used for nano-imprint processes require extremely smooth, precise foundations.
SPDT provides these foundations.
Today, SPDT plays a crucial role in:
Nano-imprint lithography masters
Hybrid freeform + meta-optical tooling
High-precision polymer wavefront optics
In this way, SPDT forms the bridge between classical geometric optics and modern wavefront-engineered meta-optics.
5. The Future: When Precision Becomes Philosophy
At Aubor, SPDT is more than a manufacturing capability—it is a philosophy of precision. It reflects the belief that every surface matters, and that the quality of light begins with the quality of the tools that shape it.
From optical design to mold engineering, from ultra-precision machining to injection molding and coating, we pursue accuracy that honors both physics and craftsmanship.
Because in optics, the surface is the soul.
