5 Ways to Enhance the Accuracy of Automotive Optical Simulations

When designing automotive optical systems, it’s important to know as precisely as possible the optical characteristics of the materials that will be used inside and outside the vehicle. This will give you accurate data to simulate and evaluate the optical systems and how they interact with the materials. You will be able to create an accurate prototype more quickly and have confidence in the simulation results.

Specific examples of how light scattering measurements can improve your optical product development include:

• Quantified product appearance qualities
• Access to nano-scale surface roughness data for more accurate optical product simulations
• Access to real-world volume scattering data in optical design evaluations

Synopsys provides high-precision measurement instruments that allow you to obtain the optical properties of materials and export them for use in design software. In this blog post, we will outline five ways to measure optical characteristics of surfaces and materials for your automotive design project.

1. Dashboard Measurement with the Synopsys REFLET 180S

The Synopsys REFLET 180S is a 109 dynamic goniophotometer that provides high resolution and flexibility because all axes can move with a small step. The spot size can be easily adjusted to focus on a specific area of interest.

In this example, we have used the Synopsys REFLET 180S to measure the optical properties of a grained dashboard surface manufactured by Mold-Tech. The measurements of this surface can be used to evaluate the desired grain size, for example. It’s used in R&D to compare different grains to see which one reflects the least and scatter the most. The goal is to have the most diffusing surface possible in order to decrease reflection in the windshield for driver safety.

The following figure shows a measurement of the 3D bidirectional reflectance distribution function (BRDF) of a dashboard sample with a 5° angle of incidence.

2. Car Exterior Finish Measurement with the Synopsys Mini-Diff V2

The Synopsys Mini-Diff V2 is a portable device that is fast and easy to use. This camera-based scatterometer allows you to obtain 3D bi-directional scattering distribution function (BSDF) in one shot, thanks to a patented optical system developed and assembled by Synopsys. Among other options, it can provide detailed data about a surface’s color properties. This can be helpful for rendering purposes of the car visual appearance.

In the following example, we measured a car’s solid paint finish using the Synopsys Mini-Diff V2, shown in the picture on the left (a).

In figure (b), the 3D perspective view of the BRDF is represented. Thanks to a cross-section tool in the software, you can easily focus on an area of interest, such as the specular peak.

In addition, the Synopsys Mini-Diff V2 software provides an RGB tool that provides color information with an RGB representation, as well as the CIE color space (L*a*b) coordinates, which can be very important for this application. You can then extract red, green, and blue curves in one plane (shown in figure (c) above) to study the color. Notice, for example, that the red curve presents a lower level of scattering than the blue or green curves, which is expected.

3. Anti-Glare Screen Measurement with the Synopsys Mini-Diff VPro

The Synopsys Mini-Diff VPro enables you to quickly obtain a dynamic, high-resolution measurement of a material’s 3D BSDF properties. It is a camera-based system that can also provide color information.

In this example, we used the Synopsys Mini-Diff VPro to qualify the performance of an anti-glare material (thin diffuser) on a car interior display screen. The material decreases reflections and glare to allow you to easily see and focus on the content being displayed.

As shown in the following figures, we used measurement data to compare the performance of two displays: one using a low anti-glare material and the other using a high anti-glare material.

The Synopsys Mini-Diff VPro measurements allow you to quickly understand which display will be the easiest to read in bright light.

4. Volume Scattering Measurement for an Automotive Light Guide with the Synopsys REFLET 180S

Diffuse plastics are commonly used in automotive light guides because they provide an effective way to spatially redistribute light. To accurately simulate light guide performance, you need to model the scattering introduced by tiny particles suspended in the plastic. Volumetric scattering – which is a bulk property of an optical medium that scatters light within the volume of a material – is one way to model light redistribution in plastic.

To obtain volume scattering data, we used the Synopsys REFLET 180S to measure the 2D BTDF of a diffuse plastic sample in four different thicknesses: 1 mm, 2 mm, 3 mm, and 4 mm.

Once we have the four measurements, we can import the data into LightTools illumination design software and model the light guide using various methods, including Gegenbauer and Mie particles. Our LightTools white paper on modeling diffuse plastics describes this process in more detail.

By modeling the light guide in LightTools using volume scattering data, you can accurately simulate its effectiveness in uniformly distributing light.

5. Synopsys Measurement Services

At Synopsys, we also offer scattering measurement services that are performed in a light- and temperature-controlled laboratory. This ensures that the measurement process does not skew product simulations by introducing new material defects. Read our scattering measurements guide for more details.

To Learn More

Read our datasheets and application notes to learn more about Synopsys optical scattering measurement solutions.