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Optical Domes

Author: the photonics expert (RP)

Definition: strongly curved optical windows

Category: article belongs to category general optics general optics

DOI: 10.61835/wsl   Cite the article: BibTex plain textHTML   Link to this page   LinkedIn

Optical domes are a special kind of optical windows that are strongly curved. For example, they can have the shape of a half-sphere, but domes with custom shapes are also available. Their function is generally to transmit light while protecting some optics by physically separating some environments: one prevents the penetration of materials (e.g. air flow or water, dust and humidity) and provides thermal and acoustic insulation. Domes with a wide range of sizes are available, sometimes with diameters well above 100 mm.

Plane optical windows would be simpler to manufacture than domes, having a substantial curvature. However, domes are often substantially more suitable for operation with a wide range of angles of entering light is required and typical side effects of that, for example optical aberrations and parasitic reflections, need to be minimized. The dome geometry may also help to achieve a superior structural strength. Aerodynamic considerations play a role in some applications.

Same optical domes need to transmit only visible light, for example for use with camera systems. They may be made of same high-quality optical glass like BK7 or fused silica. Glass domes are also available for the ultraviolet range, e.g. with UV-grade fused silica. For some applications, plastic optics (e.g. acrylic domes) are appropriate.

Other domes are operated in the infrared (→ infrared optics); for example, such devices are applied in heat-seeking missiles or for thermal imaging. A particularly robust infrared material is sapphire. Other possible choices, partly allowing for much longer wavelengths, are zinc selenide, germanium, silicon and certain ceramics.

A wide range of viewing directions is often important. The design of a half-sphere with the detector at its center may then be particularly appropriate because all light getting to these settings are will then have appropriately normal incidence on the dome surface. Under such conditions, there is no beam deflection, and anti-reflection coatings can reach a higher performance than for wide angular ranges.

Anti-reflection coatings are often needed, but in some cases one also tries to minimize the refractive index contrast between the dome material and the surrounding medium, for example water.

Robust Protective Domes

Optical domes are mostly used for protecting sensitive systems. For example, optical sensors for LIDAR built into airplanes must be protected with quite robust domes, withstanding the impact of sand or even birds at high velocities. Similarly, domes for submarines and underwater camera and video systems must withstand high pressures.

Due to the priority of protective features, some compromises may need to be made concerning optical performance. The sometimes harsh operating conditions may anyway not make it possible to preserve a very high optical quality of the exterior surface as dirt may be deposited to the outer surface during operation. Any optical coatings used there also need to be robust against external influences including cleaning operations. For maximum robustness, some optical domes are equipped with diamond-like hard carbon coatings. There are also other coatings for optical domes, e.g. anti-reflection coatings with particularly high durability, infrared filter coatings and metalized coatings.

Some domes have special mechanical features for precise mounting and sealing.

More to Learn

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Suppliers

The RP Photonics Buyer's Guide contains 25 suppliers for optical domes. Among them:

Artifex Engineering

optical domes

Artifex Engineerings offers custom optical domes from glass, quartz and sapphire. These provide high resistance to temperature, shock and scratches. We offer low cost molded domes as well as high quality polished domes for distortion free vision applications. We look forward to your inquiry.

Avantier

optical domes

Avantier produces optical domes in various substrates that are compatible with visible, infrared, or ultraviolet light. We offer personalized domes ranging in diameter from 5 mm to more than 200 mm, and we can also accommodate custom sizes upon request.

Manufacturing Capabilities:

  • material: BK7, CaF2, Cleartran, fused silica, MgF2, etc
  • diameter: 2~500 mm
  • thickness: >1 mm
  • coating: AR coating for VIS, SWIR, NIR, MWIR, LWIR, broadband
  • surface accuracy: 1/10–1 lambda
  • dimensional tolerance: ±0.1 mm
  • surface quality: 20/10-60/40
  • clear aperture: 90%
  • environmental testing: extreme cold-heat cycle, sand blasting, salt water, adhesive test
  • specification testing: qualification test, optimization test, dimensional test, according to DIN, ISO and MIL standards

Knight Optical

optical domes

Knight Optical offers a range of optical domes manufactured from BK7 or UV fused silica. We can also provide custom domes in a variety of different substrates including optical glass, sapphire, acrylic, filter glass, infrared materials, and more. Domes are Ideal optics for protecting systems from the environment due to their durability and shape. Coatings can also be applied.

Ecoptik

optical domes

ECOPTIK offers optical domes for applications in defense, weather tracking and optical imaging e.g. with underwater cameras. They are available for the visible region, the UV or for the infrared. Dimensions from 10 mm to 350 mm and thickness values between 1 mm and 10 mm are available. The domes can be equipped with reflecting or anti-reflection coatings.

Shanghai Optics

optical domes

Shanghai Optics manufactures optical domes in a wide variety of substrates, suitable for visible, IR or UV light. Our custom domes are available in sizes from 5 mm to over 200 mm diameter, with custom sizes on request.

Sinoptix

optical domes

We offer custom optical domes. Precision optical machining or molding. The material can be optical glass, sapphire, fused silica or even optical plastic (blowing or injection).

Shalom EO

optical domes

Hangzhou Shalom EO offers optical domes manufactured using various substrate materials: sapphire, BK7, hot-pressed MgF2, CVD and multispectral ZnS, ZnSe and germanium for operations both in the UV and IR spectra range.

While sapphire domes offer unrivaled hardness and good transmission in the MWIR region, hot-pressed MgF2 domes are excellent for the MWIR band with the additional benefit of thermal stability and decent mechanical hardness, and ZnSe domes and germanium domes are good choices for 3 μm to 12 μm covering the MWIR and LWIR region. CVD and multispectral ZnS domes provide superior thermo-mechanical properties and fracture strength, contributing to high endurance in hostile environments. The dimensions of the domes also come in a rich selection. The domes could be furnished with anti-reflection coatings or DLC (Diamond Like Carbon) coatings.

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