Optical domes are essentially windows with two parallel surfaces that are curved, rather than flat, to produce a hemispherical optical component.
High quality domes can offer both excellent transmission and durability when the right substrate is used. Materials such as BK7, UV fused silica, sapphire and PMMA are ideal substrates:
- N-BK7 (or equivalent) offers a tough, cost effective solution for VIS to NIR applications, it has high transmission between 300-2000nm and is virtually free of bubbles and inclusions. Knight Optical can provide precision BK7 optical domes directly from stock in 25mm to 100mm diameters and between 2 to 5mm thick, you can find these here. We can also supply large custom BK7 domes with diameters of 350+mm.
- Fused silica is ideal for wavelengths below 400nm and UV fused silica can transmit down to 180nm.
- Sapphire is used for its rugged properties and is suitable for harsh environments where a softer material would risk damage. It is often the material of choice for infrared optical domes.
- PMMA is lightweight and cheap to produce in bulk. Modern plastics are increasingly tough and in many cases offer near identical optical properties to glass while saving considerably in weight.
- Other materials include silicon, germanium, zinc selenide, certain ceramics, toughened glass and colour glass.
Precision optical domes are used in a variety of industries including aerospace, military and meteorology. They are most often used as protective windows as their hemispherical shape makes them naturally stronger in high pressure environments and also allows for a wider field of view, when compared to their flat window counterparts, and critically, they do not disrupt the optical path. Below are just a few examples of optical systems that glass domes are used in:
- LiDAR systems where it is important for the dome to be robust and abrasion resistant.
- Pyrometers (0.15-4µm) and Pyrgeometers (4-100µm).
- Underwater cameras such as those on submersible remotely operated vehicles (ROVs)
- Unmanned Automated Vehicles (UAVs)
- CCTV cameras
- Meteorology systems
Optical coatings can also be applied to increase the efficiency and durability of precision optical domes:
- AR coatings can increase the transmission, as well as reduce surface reflection. This can be critical in applications such as LiDAR where laser light is transmitted but also received back to the optical sensor being protected by the dome. It is therefore essential that the dome itself does not interfere with this.
- Hydrophobic and hydrophilic coatings can increase the durability of the dome, as well as keeping them clean.
- Diamond-like carbon coatings can be applied for maximum robustness.
Knight Optical can supply custom optical domes to meet your individual requirements, whether the domes are small or large, or need specialist coatings. All domes are tested in our state-of-the-art metrology department to ensure they meet your requirements.
Contact our multilingual technical sales team and discover how Knight Optical’s high quality domes and service can improve your instrumentation and supply chain experience.