Underwater Optics
Nov. 12, 2024
The light scattering, absorption, and refractive index of the underwater environment are different from that of the ground environment. As the depth of the water increases, the pressure increases, and the light becomes darker and darker. Besides, the chemical elements in the water corrodes the materials of the instruments underwater. To better observe the underwater environment, detect underwater resources, and protect underwater instruments, the use of high-precision optical components is essential.
Optical dome is an optical element often used in underwater instruments. Based on consideration of underwater environment factors, the optical materials of underwater domes are usually BK7, quartz, sapphire, etc. The shape of the glass dome is conducive to the underwater movement of the underwater instruments. It enhances the compressive strength and temperature resistance of the instruments. Meanwhile, it improves the corrosion resistance and mechanical strength of the instruments.
Spherical lenses are often used in underwater observation equipment. They are mostly used in objective lenses, oculars and laser collimation systems. An afocal system consisting of a plano-concave lens (used as a waterproof window) and a positive lens corrects distortion, chromatic aberration, and other aberrations. After the precise optical design, the underwater dedicated optical lenses more effectively correct aberrations and eliminate the influence of water media.
Optical mirrors, optical prisms and optical filters are commonly used for underwater lasers. Optical mirrors and optical prisms change the direction of transmission of the light beam. Optical filters filter stray light.
Commonly used underwater optical applications include underwater robots, underwater cameras, underwater probes and underwater laser systems. They are used in the hydrological survey, minefield search, environmental survey, oil drilling, fishery salvage, etc.
Materials and Design:
Materials: Common materials used for underwater domes include BK7 (borosilicate crown glass), quartz, and sapphire. Each material has distinct properties:
BK7: Offers good optical clarity and is relatively inexpensive, making it suitable for many applications.
Quartz: Provides excellent UV transmission and thermal stability, ideal for high-temperature environments.
Sapphire: Known for its exceptional hardness, scratch resistance, and high compressive strength, making it ideal for deep-sea applications.
Design: The shape of the dome is crucial. A hemispherical or conical shape not only facilitates the movement of underwater instruments but also enhances their compressive strength and temperature resistance. The dome's design also improves the instrument's corrosion resistance and mechanical strength.
Applications and Functionality:
Objective Lenses and Oculars: Spherical lenses are frequently used in objective lenses and oculars of underwater observation equipment. They help focus light and improve image quality.
Laser Collimation Systems: In laser collimation systems, spherical lenses are used to correct various aberrations such as distortion and chromatic aberration. An afocal system consisting of a plano-concave lens (acting as a waterproof window) and a positive lens can effectively correct these aberrations, enhancing the precision and clarity of the optical system.
Optical Mirrors and Prisms
Functions and Uses:
Optical Mirrors: These components are used to change the direction of light beams, which is crucial for directing light paths within complex underwater instruments.
Optical Prisms: Similar to mirrors, prisms are used to alter the path of light. They are particularly useful in systems requiring precise light manipulation, such as in underwater laser systems and imaging devices.
Optical Filters
Role and Importance:
Stray Light Filtering: Optical filters are essential for filtering out stray light, which can interfere with the clarity and accuracy of underwater observations. They help in enhancing the contrast and resolution of images captured by underwater cameras and other optical instruments.
Common Underwater Optical Applications
Underwater Robots:
Usage: Equipped with high-precision optical components, underwater robots are used for various tasks such as hydrological surveys, minefield searches, and environmental monitoring.
Benefits: The use of advanced optical components ensures that these robots can operate effectively in challenging underwater conditions, providing accurate and reliable data.
Underwater Cameras:
Usage: Underwater cameras are used for capturing images and videos in marine environments. They are essential for research, exploration, and documentation.
Benefits: High-precision optical lenses and filters improve image quality, allowing for detailed and clear visual data even in low-light conditions.
Underwater Probes:
Usage: Underwater probes are used for measuring various parameters such as temperature, salinity, and pressure. They often incorporate optical sensors to provide accurate and real-time data.
Benefits: The use of robust optical components ensures that these probes can withstand harsh underwater conditions and deliver reliable measurements.
Underwater Laser Systems:
Usage: Underwater laser systems are used for a variety of applications, including mapping, communication, and object detection.
Benefits: Precise optical components, such as mirrors, prisms, and lenses, ensure that these systems can operate effectively, providing high-resolution and accurate data.
