Working glossary of the terms used across the site.

Dispersion descriptor for an optical material: the ratio of refractive power at the d-line to chromatic dispersion across the F-to-C band. Higher vd means lower chromatic spread; polymers cluster between 20 (high-index flints) and 57 (PMMA-class crowns).

See also: Refractive index (nd) , Chromatic aberration

Multilayer thin-film stack deposited on an optical surface to suppress Fresnel reflection across a target band. On polymer substrates it is typically PVD-deposited at low substrate temperature to keep the surface form intact.

See also: Evaporative coating , Transmission band

Opto-mechanical design strategy that holds image quality across a specified thermal range by balancing CTE mismatch and refractive-index drift with compensating geometry or material pairing.

See also: CTE (coefficient of thermal expansion)

Direction-dependent refractive index caused by molecular orientation or residual stress in the part. In molded polymer optics it shows up as contrast loss in imaging paths and as polarization rotation in coherent or polarized-light systems; gating and pack/hold strategy are the primary process levers.

See also: Pack and hold , Stress-optic coefficient

An un-finished optical part — typically a molded or turned piece staged for downstream operations (coating, edging, assembly). The blank's surface form and dimensional state are released before downstream value is added.

Wavelength-dependent focal shift in an imaging system. Controlled by pairing high-Abbe (crown) and low-Abbe (flint) materials, sometimes with a diffractive element to share the burden.

See also: Abbe number (vd) , DOE (diffractive optical element)

Low-birefringence, low-water-uptake amorphous polymer family with Tg tunable by grade. Common in medical and diagnostic optics and in moisture-sensitive imaging.

See also: COP (cyclic olefin polymer, e.g. Zeonex) , Tg (glass transition temperature)

Single-monomer cousin of COC with similar low birefringence and very low water uptake. Workhorse for DMS/OMS imaging in automotive and for low-stress aspheres.

See also: COC (cyclic olefin copolymer, e.g. TOPAS)

Fractional length change per kelvin. Polymer CTE is an order of magnitude larger than glass or aluminum, so athermal designs need to budget for housing-to-lens differential growth across the operating envelope.

See also: Athermal design

Iterative review of an optical design against the realities of tooling, molding, coating, and assembly. The DFM conversation surfaces gate geometry, draft, fillets, alignment features, and tolerancing trades before the tool is cut.

Optics whose function comes from precisely controlled surface relief that diffracts light. Includes single-order DOEs, multi-order kinoforms, and hybrid refractive-diffractive lenses used to compress chromatic aberration into a thin element.

See also: DOE (diffractive optical element)

Surface relief structure that splits, shapes, or steers light by diffraction rather than refraction. On polymer optics, DOEs are typically lithographically mastered and replicated in the molding tool surface.

See also: Diffractive optics , MTF (modulation transfer function)

Near-field optical wave that decays exponentially away from a guiding interface. Relevant to waveguide design, biosensors, and certain illumination geometries built on polymer substrates.

Thin-film deposition technique — typically electron-beam or thermal PVD — in which source material is vaporized in a vacuum chamber and condenses onto the optic. Sandia's polymer-friendly coating window keeps substrate temperatures inside Tg margins.

See also: AR coating (anti-reflection) , Tg (glass transition temperature)

Angular extent over which an imaging system collects light at the focal plane. Wide-FOV polymer lenses (DMS/OMS, surveillance, AR) drive aggressive asphere and free-form surfaces that polymer molding handles natively.

The opening through which molten polymer enters the cavity. Gate location, geometry (edge, fan, submarine), and size set how flow lines, stress, and birefringence distribute through the molded part.

See also: Birefringence , Pack and hold

Heated manifold/nozzle system that keeps polymer molten between machine and cavity, eliminating cold-runner regrind and reducing shot-to-shot thermal swing. Useful for cycle stability on multi-cavity optical tools.

Removable tool element that carries the optical surface or a feature within the cavity. Inserts let one tool serve multiple optical designs and isolate wear or damage to a replaceable component.

Diffractive element whose surface depth is an integer multiple of a single-order kinoform's depth, trading bandwidth for higher diffraction efficiency at the design wavelengths.

See also: DOE (diffractive optical element)

Frequency-domain measure of how an imaging system reproduces contrast at increasing spatial frequencies. Polymer lens MTF is bench-verified against the program's release criteria, not against a glass surrogate.

Phases of the molding cycle that follow injection — pressure is applied to compensate for shrink as the cavity cools. Pack and hold profile is the dominant lever on optical-grade dimensional and birefringence outcomes.

See also: Birefringence , Gate

The crown-class optical polymer: high transmission across the visible, moderate Abbe, low cost. Workhorse for cost-driven imaging and illumination optics.

See also: Polycarbonate (PC) , COC (cyclic olefin copolymer, e.g. TOPAS)

High-index, impact-resistant amorphous polymer. Wins for impact protection and thermal headroom but birefringence is significant — process discipline matters.

See also: Birefringence , PMMA (poly(methyl methacrylate))

Documentation package that releases a part for production. For molded optics it bundles scientific-molding evidence (viscosity, gate-seal, cavity-pressure), tool design, capability studies on the optical release criteria, and metrology-lab release evidence.

See also: Scientific molding

Disk-shaped polymer blank used as the starting workpiece for single point diamond turning of prototype or low-volume optics.

See also: SPDT (single point diamond turning)

Ratio of the speed of light in vacuum to the speed in the material, evaluated at the d-line (587.6 nm) by convention. Optical polymers cluster between 1.49 (PMMA) and 1.65 (high-index flint grades).

See also: Abbe number (vd)

Process-development discipline that characterizes a molding cycle by the polymer's response — viscosity curve, gate-seal time, cavity-pressure map — rather than by machine-set values. The foundation under optical PPAP.

See also: PPAP (production part approval process)

Ultra-precision lathe process that cuts an optical surface directly into a polymer or non-ferrous metal blank with a monocrystalline diamond tool. The right path for polymer-optics prototypes and short runs before a mold is justified.

See also: Puck

The first channel that delivers melt from the machine nozzle to the runner system in a cold-runner tool. Cut off and recycled as regrind where the part chemistry allows.

Material constant relating mechanical stress to induced birefringence. Polycarbonate's is large; cyclic olefins' is small — the reason COP/COC dominate low-birefringence imaging.

See also: Birefringence

Temperature at which an amorphous polymer transitions from a glassy to a rubbery state. Coating, sterilization, and operating-temperature envelopes are bounded relative to Tg.

Trade name (TOPAS Advanced Polymers) for a family of COC grades — see COC for properties and typical use.

See also: COC (cyclic olefin copolymer, e.g. TOPAS)

Wavelength range over which a polymer or coating passes light usefully. Polymer-optic transmission bands typically span the visible into the NIR, with grade-specific roll-offs at the UV and SWIR edges.

Coupon coated alongside production parts in the same vacuum run. Used to verify the deposition recipe against transmission, reflectance, and adhesion specs without sacrificing the part.

See also: Evaporative coating

Trade name (Zeon Corp.) for a family of COP grades; see COP for properties and typical use.

See also: COP (cyclic olefin polymer, e.g. Zeonex)