Abstract
The 270-degree field-of-view three-lens diving mask represents a significant innovation in modern diving equipment. Through a three-lens configuration consisting of a primary lens and two side lenses, it achieves a wide-angle observation capability approaching the natural field of view of the human eye. This paper systematically elaborates on the design philosophy and manufacturing processes of the 270° three-lens diving mask from the perspectives of optical design principles, structural layout, material systems, core manufacturing processes, and performance verification. Key technical aspects such as PC lens injection molding, liquid silicone rubber (LSR) overmolding, and anti-fog coating treatments are analyzed in detail, providing a technical reference for the engineering design and manufacture of diving masks.
1. Introduction
The diving mask is a core piece of equipment for divers to observe the underwater environment. Its basic function is to form an air space between the face and the water, allowing the eyes to focus properly and see clearly. Although traditional single-lens masks offer a relatively wide field of view, they are limited by the single-lens structure, resulting in noticeable blind spots in the peripheral vision. Three-panel masks effectively improve peripheral vision by adding auxiliary lenses on both sides. The 270° three-lens diving mask further optimizes this concept, achieving a near-panoramic observation range with its three-lens optical structure, making it a preferred choice for both recreational and professional diving.
2. Optical Design Principles and Structural Layout
2.1 Three-Lens Optical Structure
The 270° three-lens diving mask adopts a “one primary lens + two side lenses” optical configuration. The primary lens is positioned at the front center, providing the main forward field of view; side lenses are placed on the left and right sides, covering the peripheral vision in each direction. This structure forms a composite visual field system featuring “physical separation + visual continuity,” which effectively reduces underwater field distortion and enhances independent focusing capability for each eye.
The side lenses are not coplanar with the primary lens; the angle between them is typically designed to be between 95 and 140 degrees. This angle parameter is precisely calculated to ensure that the side lenses effectively capture peripheral light while avoiding optical distortion or visual jumps caused by excessive angles. The combined action of the three lenses allows the diver to observe the lateral environment without frequent head turns, significantly improving underwater observation range and safety.
2.2 Mechanism for Achieving 270° Field of View
The natural field of view of the human eye in air is approximately 200–220 degrees horizontally. Underwater, due to the constraints of the mask frame and lens structure, the field of view of traditional masks is typically compressed to 120–150 degrees. The 270° three-lens design achieves a significant expansion of the field of view through the following approaches:
First, the primary lens adopts a large-size, low-curvature wide-angle design to maximize forward coverage; second, the two side lenses are tilted outward, incorporating the peripheral areas normally blocked by the traditional mask frame into the visible range; third, the junctions between the three lenses are optimized to minimize visual blind spots. The three-lens design also increases light intake through the side windows, creating an open and transparent visual experience, which is especially beneficial for divers sensitive to confined spaces.
2.3 Close-Fit Face Design and Field Optimization
The 270° three-lens diving mask is typically combined with a close-fit face design—the nose area protrudes independently from the lens plane, bringing the lenses closer to the face. Shortening the distance between the lenses and the eyes significantly increases the effective field-of-view ratio while reducing the internal air volume of the mask, making pressure equalization easier. This design also reduces optical distortion—the closer the lens is to the eye, the shorter the path of light refraction through the lens, resulting in less imaging distortion.
3. Material System Selection
3.1 Lens Materials
Two main technical approaches are available for the lens materials of the 270° three-lens diving mask:
Tempered glass is the traditional choice for high-end diving masks. It offers high light transmittance, stable optical performance, high surface hardness, and scratch resistance, typically with a thickness of 3–4 mm. However, it has a high specific gravity, is difficult to process, and has relatively limited impact resistance.
Polycarbonate (PC) is a new lens material that has gained rapid popularity in recent years. PC has a light transmittance exceeding 92%, extremely high impact strength, low specific gravity, thin lens profiles, and effective UV absorption. PC can be injection molded, offering high production efficiency, low cost, and ease of overmolding with silicone and other materials. For the 270° three-lens structure, the advantages of PC injection molding are particularly prominent—the three lenses can be precisely molded in the same mold system, ensuring dimensional consistency and assembly accuracy.
3.2 Skirt and Sealing Materials
Liquid silicone rubber (LSR) is currently the mainstream material for diving mask skirts. Food-grade LSR is odorless, free of fluorescent agents, and non-allergenic to facial skin. LSR injection molding can precisely replicate the complex curved surfaces of the mold cavity, achieving a high degree of conformity to facial contours and ensuring waterproof sealing performance.
3.3 Frame Materials
Traditional three-lens diving masks typically use rigid engineering plastics such as ABS or nylon for the frame. However, with the popularization of integrated molding technology, independent rigid frames are gradually being replaced by frameless designs where the skirt itself serves as the frame.
4. Core Manufacturing Processes
4.1 Lens Forming Processes
PC Lens Injection Molding: PC pellets are dried and fed into the hopper of an injection molding machine, where they are melted by electric heating, then injected into a precision mold cavity, held under pressure, cooled, and finally ejected after mold opening. Key process parameters include injection temperature, injection pressure, holding pressure time, and cooling time. For the three-lens structure, a multi-cavity mold is required to simultaneously mold the primary and side lenses, ensuring consistent optical parameters across all three lenses.
Tempered Glass Lens Processing: Glass lenses are manufactured through optical cold-working processes, including cutting, grinding, polishing, and tempering. Tempered glass lenses offer high precision and excellent optical performance, but the processing cycle is long, the cost is high, and complex curved shapes are difficult to achieve.
4.2 Integrated Molding of Lenses and Skirt
Integrated molding (also known as co-injection molding or overmolding) is the core process in manufacturing the 270° three-lens diving mask. The process flow is as follows:
Step 1 – Lens Positioning: The pre-molded PC lenses (primary and side lenses) are precisely placed into the designated cavities of the soft mask mold. The positioning accuracy of the lenses directly determines the optical axis alignment and sealing quality of the final product.
Step 2 – Silicone Injection: The injection molding machine injects liquid silicone rubber into the mold cavity, with injection temperature controlled at 200–250°C and injection pressure at 40–50 T/cm2. Under high temperature, the LSR undergoes vulcanization cross-linking, transitioning from a liquid to an elastic solid state.
Step 3 – Integrated Bonding: During curing, the silicone “embraces” the outer edges of the lenses, forming a chemical-level bond—a “chemical weld” is achieved between the skirt edges and the lenses. The lenses cannot be detached, structurally ensuring the sealing integrity of the mask.
Integrated molding completely eliminates the separate plastic frame, simplifying the traditional three-part structure of “lens–frame–skirt” into a single integrated “lens–skirt” unit. This process removes the physical seam between the frame and the skirt, fundamentally solving leakage problems caused by adhesive aging or buckle loosening.
4.3 Anti-Fog Treatment Processes
Fogging on the inner surface of the lenses due to temperature differences in the underwater environment is one of the main challenges faced by diving masks. The anti-fog treatment for the 270° three-lens diving mask primarily employs the following processes:
Anti-Fog Coating Technology: A hydrophilic anti-fog coating is applied to the inner surface of the lenses, causing water vapor to form a uniform film rather than discrete droplets on the lens surface, thereby maintaining transparency. Some high-end products adopt nano anti-fog coating processes, with anti-fog effectiveness lasting for dozens of dives.
Lens Pre-treatment: The integrated three-lens structure facilitates comprehensive anti-fog treatment of all lenses before assembly, covering the inner surfaces of the primary and both side lenses. In the integrated molding process, the anti-fog coating must be applied before the lenses are placed into the mold, and it must withstand the high temperatures during injection molding without being damaged.
4.4 Assembly and Inspection
The integrated molding process greatly simplifies subsequent assembly steps. The molded lens-skirt integrated unit is directly fitted with head strap buckles, nose pads, and other accessories. Quality inspection procedures include:
Air Tightness Test: Simulating underwater pressure conditions to check the sealing performance of the lens-skirt junctions and the overall mask.
Optical Performance Test: Using interferometers, spectrometers, and other equipment to measure transmittance, distortion, chromatic aberration, and other indicators.
Field-of-View Angle Test: Mounting the mask on a standard head form and using wide-angle imaging sensors and image analysis software to calculate the maximum visible angles in both horizontal and vertical directions.
5. Process Challenges and Technical Difficulties
5.1 Positioning Accuracy of Three Lenses
The relative positional accuracy of the three lenses within the mold directly affects the optical axis consistency of the final product. Any angular deviation between the primary lens and the side lenses can result in misalignment or blind spots at the visual junctions. Solutions include employing high-precision mold positioning systems, optimizing gate locations through mold flow analysis, and implementing in-line vision inspection for real-time monitoring.
5.2 Interface Bonding of Dissimilar Materials
PC lenses and LSR skirts are dissimilar materials, differing in chemical composition, thermal expansion coefficients, and surface energy. Ensuring a strong chemical bond at the interface between the two materials during injection molding is the core technical challenge of integrated molding. Process parameters such as injection temperature, pressure, and mold temperature must be precisely controlled, and surface pretreatment of the lens edges may be necessary to enhance adhesion.
5.3 Deep-Water Pressure Resistance
The 270° three-lens structure, with its multiple lenses and extensive joint surfaces, faces greater challenges to structural integrity under high-pressure deep-water environments. Lens thickness, frame rib reinforcement design, and sealing structure redundancy must all undergo rigorous hydrostatic pressure testing and verification.
6. Conclusion
The 270° field-of-view three-lens diving mask, through its three-lens optical configuration consisting of a primary lens and two side lenses, combined with a close-fit face design and integrated molding technology, achieves a near-panoramic underwater observation field. The integrated manufacturing process centered on PC lens injection molding and LSR overmolding not only eliminates the sealing risks associated with traditional assembly methods but also significantly improves production efficiency and product consistency. With continued advances in mold flow analysis, precision injection molding techniques, and anti-fog coating materials, the 270° three-lens diving mask still holds broad potential for improvement in field breadth, optical quality, and wearing comfort.
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