Introduction to Ocean™'s Measurement Virtual Tools
The Importance of Accurate Input Data in Simulations
Ocean™ is a tool for visual virtual prototyping of products. It is therefore a calculation tool dedicated to the simulation of materials. In any simulation approach, the quality of the input data is intrinsically linked to the quality of the results. Therefore, the best possible compromise should be aimed at for the measurements, input data or virtual material models used.
Beyond Visualization: Validating Virtual Materials
For this purpose, our approach is not only limited to the visualisation of materials in-situ, but also includes a validation phase of the virtual materials. We have therefore implemented standardised measurements, commonly performed in the laboratory with measurement tools (spectrometer, …) in a digital version within Ocean™.
Understanding virtual tools in Ocean™
- How can we be sure that the integration of measurements are correct in Ocean™?
- How can we be sure that measurements treatment for their integration in Ocean™ is correct?
- How can we be sure that our hypothesis while creating the Ocean™ material are correct?
Integrating Sphere, principle and function:
An integrating sphere, shown in figure 1, is an optical component consisting of a spherical cavity with its interior covered with an almost perfect diffuse white paint. Small holes allow the entrance and exit of light. Light rays incident on any point on the inner surface are, by multiple scattering reflections, distributed equally to all other points. Knowing the light properties, and knowing that all the reflected light on a sample is collected, one can extract reflectance spectrum of the measured sample.
Figure 1 - Open Integrating sphere, showing the diffuse white paint inside.
Geometries and Measurement Methods
Several geometry exist. A classic geometry is the ‘d8’ one where light and detector are at 8° of the normal of a sample (see figure 2).
Figure 2 - Integrating sphere principle
With this set-up, two measures are possible :
- Measure Specular Included (SCI) : Total reflectance (Specular port close)
- Measure Specular Excluded (SCE) : Diffuse reflectance only (Specular port open)
Implementing the Integrating Sphere in Ocean™
In Ocean™, the sphere is reproduced with a given design that allow to make SCI and SCE measurement. Thanks to the spectral boxes sensor in Ocean™, the virtual d8 integrating sphere allow the virtual measurement of the reflected spectrum.
A result example is given in figure 3, where we can finds comparison of d8 integrating sphere SCE and SCI measurements for a isotropic orange glossy paint (shown in figure3). You can see that the relative difference between Ocean™ measurement and physical ones is less than 0.5% (green points) for both SCE and SCI measurement, indicating that, the material simulation and the virtual integrating sphere are correctly implemented.
Figure 3- Example of comparison between Ocean™ virtual d8 integrating sphere and real measurements.
45:0 spectrophotometer, principle and application
A 45:0 spectrophotometer, used in the device shown in figure 4, is a device allowing the measurement of the reflected spectrum, in which, the light source is fixed at 45-degrees, and the detectors are set at 0-degrees. A 45:0 is ideal for measuring color on smooth and matte surfaces because it captures the reflection from a sample just as the human eye would see it.
Figure 4 - Example of device using a 45:0 spectrophotometer
Reproducing the 45:0 Spectrophotometer in Ocean™
Figure 5 - 45:0 spectrophotometer principle
In Ocean™, the 45:0 spectrophotometer is reproduced with a given design. Thanks to the spectral boxes sensor in Ocean™, the virtual 45:0 spectrophotometer allows the virtual measurement of the reflected spectrum.
A result example is given in figure 6, where one can finds comparison of 45:0 spectrophotometer measurements for a isotropic black paint. You can see that the relative difference between Ocean™ measurement and real ones is less than 0.5% (green points), indicating that, the material simulation and the virtual integrating sphere are correctly implemented.
Figure 6 - Example of comparison between Ocean™ virtual 0:45 spectrophotometer and real measurements.
Conclusion - The Future of Material Science with Ocean™
Benefits of Virtual Measurement Tools
In this article we have detailed two reference instruments in their digital version in Ocean™. Both instruments have been validated with controlled samples and physical measurements. This virtual measurement approach allows several possibilities:
- a validation phase for the optical models
- a verification of the measurements
- a prototyping phase for new virtual materials within Ocean™.
Implications for Research and Development
Indeed, if a large part of Ocean™’s applications allow the visualisation of materials in-situ, Ocean™ is also used for R&D purposes to create new concepts and materials.
For this purpose, new virtual instruments are being studied, such as: multi-angle spectrometer, brilliance meter, goniospectrophotometer, etc. With these new instruments, the aim is to offer our users a real virtual optical laboratory.
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