Knight Optical, a supplier of high-performance precision optics for underwater imaging and subsea equipment, provides a guide on optical prisms, explaining how they work, when to use each type, and applications in challenging underwater environments. Read more >>
Optical prisms are transparent components with flat, polished surfaces that alter light with their geometric form. They manipulate light through refraction, which bends light and can disperse wavelengths, and through total internal reflection (TIR), which redirects beams, inverts images, and controls optical paths.
Prisms are manufactured from materials like N-BK7, UV-fused silica, and specialised substrates such as Zinc Selenide (ZnSe) and Germanium (Ge).
These two mechanisms enable distinct prism capabilities, with some designs leveraging refraction and others TIR.
In subsea exploration specifically, prisms are critical inside AUVs and ROVs, inside underwater cameras, laser line scanners, and spectroscopic sensors to enhance imaging and water-quality analysis.
Importance of Prism Accuracy
When selecting the most appropriate prism for a project, specifiers must understand which mechanism best suits their application. High-precision alongside accurate manufacturing and testing are also essential when choosing an optical component supplier.
Underwater systems frequently operate in environments where calibration and accuracy are crucial, with even a few arcseconds of prism misalignment potentially degrading spectral analysis, distorting images, or reducing communication efficiency.
Knight Optical’s metrology laboratory equipment can perform 3-arcsecond testing to identify the smallest inaccuracies and ensure every prism meets exacting performance standards, critical for AUVs, and ROVs in harsh operational settings.
Prism Types & Purposes in Underwater Applications
Dispersive prisms separate light into spectral bands, since different wavelengths of light bend by varying amounts as they pass through. Knight Optical supplies different dispersive prisms, including Equilateral prisms for maximum wavelength separation, Pellin-Broca prisms for selective output at 90°, and Wedge prisms for controlled beam deviation with minimal dispersion.
Alternatively reflecting prisms use TIR to redirect beams and control image orientation. Common designs by Knight Optical include Porro prisms for beam inversion, Penta prisms for constant 90° deviation, Dove prisms for image rotation, and Rhomboid prisms for lateral displacement.
Dispersive prisms enable fluorescence and absorption spectroscopy to study plankton, dissolved matter, and seabed composition, while reflecting prisms maintain accurate optical alignment in cameras and laser instruments under high pressure and corrosive subsea conditions.
Prisms also support navigation and communication, with Dove and Penta prisms specifically used in underwater optical systems for precise beam steering, key for short-range high-bandwidth links between submersibles or sensor nodes.
