Introduction
In watchmaking, every detail matters — and the watch glass is no exception. As it protects and reveals the watch’s inner excellence, its design and optical performance are key to showcasing precision, clarity, and elegance. Whether it’s sapphire, mineral glass, or polycarbonate, the choice of material and shape directly impacts the visual performance and technical behavior of the final product.
At Eclat Digital, we use advanced optical simulation powered by precise optical characterization to help watchmakers and suppliers make the right decisions — faster. Our software, Ocean™, preserves material data quality from input to output, enabling predictive visualizations and accurate optical analysis that reduce the need for physical prototypes.
Choosing the right glass material: Sapphire, mineral glass, or polycarbonate?
Each glass type comes with trade-offs. By simulating optical behavior based on measured refractive indices and other key properties — such as dispersion, transmittance, and surface reflectance — we help you evaluate the visual and technical performance of different materials in real-world conditions.
Impact
By simulating optical behavior using accurate refractive indices, dispersion curves, and surface characteristics, we help identify glare levels, chromatic effects, and reflection intensity. This enables confident selection of the most suitable material before any physical prototyping begins, saving time and reducing iteration costs.
As displayed on these images, sapphire has the higher refractive index. The higher the refractive index, the more intense the reflection and the distortion.
Figure 1: Sapphire simulated with Ocean™
Figure 2: Glass simulated with Ocean™
Figure 3: Polycarbonate simulated with Ocean™
Outcome
In this example, we use different types of materials to better demonstrate the differences. This method can also be used to identify slight variations within the same material type and determine the best candidate between two glass compositions for example. Watchmakers can compare visual clarity, internal reflections, and light transmittance under various lighting conditions. The result is better-informed decisions that reduce aesthetic mismatches, improve perceived quality, and accelerate product development cycles.
Iterating on geometry - Because even slight variations in radius are significant.
Even the slightest variation in glass geometry can affect the way light travels through the watch — and how the final product looks and performs.
We ran simulations on three versions of the same glass material:
- Nominal shape
- Radius -0.3 mm
- Radius +0.3 mm
Figure 4: Cross section of a watch glass
Impact
Variations as small as ±0.3 mm in dome radius impact focal behavior, light diffusion, and internal reflections. Optical simulation run with Ocean™ highlights changes invisible in CAD tools, allowing designers to refine shapes for clarity, legibility, and consistency before investing in physical samples.
Figure 5: Nominal shape simulated with Ocean™
Outcome
Simulation enables simultaneous optimization of technical performance and aesthetics. Design teams can balance branding intent with optical efficiency, avoiding costly trial-and-error with different glass geometries and ensuring better integration with other watch components.
Testing anti-reflective coatings in real-world conditions
Anti-reflective (AR) coatings are key to improve legibility and reduce unwanted glare — but their performance depends on coating design, stack thickness, and material choice.
With Ocean™, we simulate:
- Multi-layer AR stacks
- Coating performance under different lighting conditions
- Interactions with the glass substrate
Impact
Ocean™ simulates multi-layer interference, substrate interactions, and lighting-dependent behavior using physically-true modeling. It reveals how AR coatings perform across angles, lighting environments (daylight, LED, etc.), and glass types, minimizing post-production surprises.
Figure 6: AR coatings simulated with Ocean™
Outcome
Simulation validates design assumptions early. You can optimize coating stack thickness, reduce parasitic reflections, and ensure high legibility—especially in challenging lighting—while cutting down the number of required coating prototypes.
Beyond the basics: Simulating add-ons and decorative effects
Glass isn’t just a transparent dome — it’s a design space. We can also simulate:
- Facets and ovals
- Etched surfaces and metallization
- Index bubbles or decorative layers like TiO₂ coatings
Impact
These added elements introduce local variations in reflectance, scattering, or color shifting. Ocean™ helps anticipate their visual consequences across viewing angles and lighting, ensuring design consistency.
Outcome
Watchmakers can validate creative features without risking trial-and-error in manufacturing. Simulation shortens development timelines and provides photorealistic outputs to support design decisions.
Ocean™ helped us drastically reduce prototyping loops. It identified, through simulation, the material combinations that wouldn’t meet our expectations, so we focused physical prototype production on just the two best-performing solutions.
Conclusion: Optical simulation that reflects reality
Whether you’re selecting the best material, fine-tuning the geometry, or optimizing coatings and decorative features, Ocean™ offers a scientific, data-driven approach to visual and optical challenges in watch glass development.
We don’t just simulate looks — we simulate reality.
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Q&A
Can you simulate decorative and non-functional features?
Yes. Ocean™ simulates a range of surface and volumic effects including etching, coatings, facets, bubbles, and more.
What optical properties are important in watch glass selection?
Refractive index, dispersion, surface reflectance, and transmittance are critical. They determine how light interacts with the glass and how the watch is perceived under various lighting conditions. All these properties can be imported in Ocean™ to generate predictive images and data analysis.
How accurate is your simulation compared to physical prototypes?
Ocean™ uses spectral measurements and optical physics to deliver predictive visualizations and numerical data that correlate closely with physical prototypes — often eliminating several prototyping loops.
Can virtual prototypes replace physical prototypes?
Virtual prototypes don’t aim to fully replace physical ones — they help reduce their number and increase their relevance. By simulating light behavior and appearance with real material data, Ocean™ allows you to identify failing compositions early and focus physical prototyping only on the most promising options. This means fewer trial-and-error loops, faster development, and a higher chance of getting it right the first time.
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