How to simulate and design Light Shaping Diffuser

“Hotspots” and uneven light distribution are common problems with filament, arc, LED, CCFL, fiberoptic and laser light sources. LSDs greatly smooth and homogenize sources while providing uniform light in critical applications such as LCD backlights, Light Shaping Diffuser can convert discrete light point sources into one uniform light source, making it the ideal LED strip light diffuser. 

Luminit Light Shaping Diffusers® (LSDs) help lighting designers and optical engineers optimize illumination or optical hardware performance. However, determining the optimal diffusion angle can be challenging given the number of options. 

The Light Shaping Diffuser® (LSD) is used to scatter incoming light which strikes the surface. Luminit uses its holographic diffuser technology to create pseudo-random micro-lens structures. Since it uses the principle of surface scatter instead of volume (bulk) scatter, it tends to have a much higher transmission efficiency. The LSDs are designed to reduce the effects of diffraction, which eliminates zero order and chromatic variation (rainbow appearance). Hence, the scatter appears white to the eyes (in white light condition).

There are many types of scatter models and each one has a particular purpose to which they are simulating. Like the product, the LSD model takes the rays which strike the surface of a volume object, and scatters the direction of the light. Since this a random statistical model, each ray which strikes the surface will take a different path to exit, even if it has the same exact path in. This LSD model scatters the rays in such a way as to emulate the shape of statistical distribution of the Luminit LSD product. The shape will change from Gaussian in smaller angles to trapezoidal in larger angles. The amount of angular spread will depend on the LSD angles entered by the user. These angles will be limited to catalog values (given at the end of this article).

Depending on the angle of distribution, LSDs will achieve between 85% and 92% transmission efficiency. The low back-scatter of LSD structures are anti-reflective in nature and utilize light that would otherwise be wasted due to Fresnel loss. A clear piece of polycarbonate substrate is 89% transmissive. With LSD, transmission improves to 92%. Note: Luminit measures transmission utilizing an integrated sphere with the LSD structure facing the light source.

Listed are the transmission efficiencies of a 10° LSD measured at the following wavelengths: 532nm-90%, 632nm-90%, 850nm-89%, 980nm89%, 1064nm-89%, 1550nm-88% .


1. All LSD angles are specified in FWHM.

2. Large angle LSDs, when placed at the image plane, make excellent high resolution viewing screens. 3. Small angle LSDs can be combined with polarizers to reduce moiré and improve uniformity.

4. LSDs can be combined with other optical components such as lenses, Fresnels, and prismatic structures.

Let’s take an circular 60 degree as an example,

Material is PMMA and thickness is 0.1mm

Before scattering:

After scattering;

Intensity profile:

Perfect meet the specs!

The LSD scatter model will enable you to efficiently select the best LSD angle for your illumination or optical design project.

Common missing steps Please make sure these steps are followed. Otherwise the program will not work as you intended.

  • All source parameters are filled out properly. Wavelength, spectral range, direction, etc..
  • The number of ‘analysis rays’ has to be set to a very high number (1e5 to 1e8) at your discretion for resolution and trace time.
  • Check to make sure you applied the scatter model to the appropriate ‘Face’ of the object.
  • Check that the ‘Scatter Fraction’ for the LSD surface is set to 1.
  • 5 Check to make sure you press ‘Enter’ on the keyboard after entering the numbers.
  • Make sure the object is a ‘volume’ type object such as rectangular volume, cylindrical volume, standard lens, etc..
  • Check that your object has a ‘Material’ associated with it, such as ‘PMMA’ or ‘BK7’.
  • Make sure that the boxes for ‘Ignore Errors’ and ‘NSC Scatter Rays’ is checked in the ‘Ray Trace’ controls. Make sure the boxes for ‘Use Polarization’ and ‘Split NSC Rays’ are Unchecked.
  • Tracing the rays backwards does not work (example: surface 2 to 1 on cylindrical volume).
  • The settings for the resolutions on the Detector should be optimize for the LSD and output distribution of the rays

Reference :


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