“Hotspots” and uneven light distribution are common challenges when working with filament, arc, LED, CCFL, fiber-optic, and laser light sources. Light Shaping Diffusers (LSDs) are specifically designed to smooth and homogenize these sources, producing highly uniform illumination in demanding applications such as LCD backlights, LED strip lighting, projection, and machine vision.
LSDs can transform multiple discrete light points into a single, uniform output, making them especially effective as LED strip light diffusers.
What Is a Light Shaping Diffuser (LSD)?
Light Shaping Diffusers® (LSDs) from Luminitco are engineered using holographic diffuser technology. Rather than relying on bulk (volume) scattering, LSDs use pseudo-random micro-lens structures on the surface to scatter light.
Key advantages of surface-scatter technology:
- Higher transmission efficiency than bulk diffusers
- Reduced diffraction artifacts
- Elimination of zero-order and chromatic (rainbow) effects
- White, color-neutral scatter under broadband illumination
How LSDs Work
LSDs scatter incident light when it strikes the diffuser surface. The micro-lens array redistributes ray directions according to a controlled statistical angular profile.
Important characteristics:
- Light is scattered at the surface, not through the material volume
- Each ray exits in a statistically random direction, even if incoming rays are identical
- The angular output distribution depends on the selected LSD diffusion angle
As the specified diffusion angle increases:
- Small angles → approximately Gaussian distribution
- Large angles → trapezoidal or flattened distributions
All LSD diffusion angles are specified in FWHM (Full Width at Half Maximum).
Transmission Efficiency
Depending on the diffusion angle, LSDs typically achieve 85%–92% transmission efficiency. Notably:
- A clear polycarbonate substrate alone transmits ~89%
- With LSD surface structures, transmission can improve to ~92%
- Low back-scatter behavior makes LSDs anti-reflective in nature, recycling light that would otherwise be lost to Fresnel reflections
Measured transmission of a 10° LSD:
- 532 nm → 90%
- 632 nm → 90%
- 850 nm → 89%
- 980 nm → 89%
- 1064 nm → 89%
- 1550 nm → 88%
(Measured using an integrating sphere with the LSD structure facing the light source.)
Design Notes and Practical Use
- LSD diffusion angles are specified in FWHM
- Large-angle LSDs placed at the image plane make excellent high-resolution viewing screens
- Small-angle LSDs can be combined with polarizers to reduce moiré and improve uniformity
- LSDs integrate well with lenses, Fresnels, prisms, and other optical elements
Simulation Example: 60° Circular LSD
Example parameters
- Diffusion angle: 60° (circular)
- Material: PMMA
- Thickness: 0.1 mm
Before Scattering
The incident rays show clear spatial non-uniformity and hotspots.
After Scattering
The LSD redistributes rays into a smooth angular distribution.
Intensity Profile
The simulated intensity profile closely matches the target specification, confirming correct diffuser selection and setup.
Result: The LSD scatter model enables rapid validation of diffuser angle and performance before prototyping.
LSD Scatter Model in Optical Simulation
The LSD scatter model applies a statistical surface scatter to rays striking the selected object face. This closely emulates the real Luminit LSD product behavior and allows designers to evaluate diffuser performance accurately.
Common Setup Errors (Important Checklist)
To ensure correct simulation results, verify the following:
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All source parameters are correctly defined (wavelength, spectrum, direction, power)
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The number of analysis rays is sufficiently high (typically 1e5–1e8)
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The scatter model is applied to the correct face of the object
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Scatter Fraction = 1 on the LSD surface
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Press Enter after entering numerical values
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The object is a volume type (rectangular volume, cylindrical volume, standard lens, etc.)
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A valid material (e.g., PMMA, BK7) is assigned
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In Ray Trace controls:
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No Ignore Errors
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No NSC Scatter Rays
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Don’t Use Polarization
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No Split NSC Rays
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Do not trace rays backward through the object (e.g., surface 2 → 1 on a volume)
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Optimize detector resolution to match the LSD output distribution
Failure to follow these steps can lead to incorrect or misleading results.
Conclusion
Light Shaping Diffusers provide an efficient and elegant solution for eliminating hotspots and achieving uniform illumination. When accurately modeled using an LSD scatter model, designers can quickly determine the optimal diffusion angle, reduce design iterations, and improve overall optical system performance.
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