Imaging Sphere

IS-SA™ for Scatter and
Appearance Measurement

IS-SA               Scatter andAppearance Measurement

High-speed, highly-flexible system for comprehensive BRDF, BTDF, and TIS measurement

The IS-SA (Imaging Sphere for Scatter and Appearance Measurement) provides rapid measurement of scatter distribution functions for almost any material, including films, metals, plastics, papers, textiles, and surface treatments such as cleaners, polishes, coatings, and paints. The IS-SA system is designed for use in both R&D and production quality control applications for material characterization and quality assessment. It also provides the fastest, most comprehensive means available for building libraries of BSDF measurements for computer modeling and rendering. Overall, the IS-SA is a faster, more cost-effective alternative to traditional photogoniometric BSDF measurement devices and delivers excellent accuracy, adaptability, and reliability.

Novel optical configuration measures a full hemisphere of scatter data at once

Accurate modeling of surface appearance for arbitrary materials requires either complex simulations to account for subtle surface variations, or the use of measured BSDF (bi-directional scatter distribution function) data. Traditionally BSDF measurements are performed using goniometric systems, but these instruments are relatively slow, potentially requiring hours to measure a sample under a full range of illumination and observation angles. By taking advantage of a novel optical configuration and the ability of an imaging system to capture up to millions of simultaneous measurements, Imaging Sphere technology captures 2π steradians (a full hemisphere) of scattered light in a single measurement, dramatically reducing the time required to obtain a BSDF measurement.

The IS-SA system is comprised of a ProMetric Imaging Colorimeter (used to capture information on luminance and color coefficients), a light source (which can be positioned at any illumination angle), and a hemispherical measurement chamber designed so that the imaging colorimeter "sees" the full inner surface of the measurement chamber with the aid of a convex mirror. The surface of the material to be measured is positioned at the aperture of the IS-SA and then illuminated at a user-selected angle. Specular and diffuse reflection from, or transmission through, the material strikes the inner surface of the Imaging Sphere dome, allowing it to be measured by the imaging colorimeter.

The IS-SA captures an entire hemisphere's worth of scatter data, including both luminance and color, in a single measurement. The angular resolution of the system is determined by the number of pixels on the camera's image sensor and is typically less than 0.5°.

Multiple configuration options meet multiple needs

The standard configuration of the IS-SA provides measurement of BRDF (bi-directional reflectance distribution function) and is available with a choice of a PM03 Imaging Colorimeter with 512 x 512 pixel resolution or a high-sensitivity PM13 Imaging Colorimeter with 1024 x 1024 pixel resolution.

Various mechanical extensions are available to increase the range of measurements that can be taken and to increase automation. With an optional Transmission Arm attachment the illuminator can also be positioned to illuminate the material sample so that the transmitted light is captured by the IS-SA, so providing measurement of BTDF (bi-directional transmission distribution function). An optional goniometric positioning system can also be added to automatically move and rotate the material sample at the measurement aperture.

Many IS-SA users also have other colorimetric testing needs. Because of its reconfigurable hardware and software design, the IS-SA user also has the option of performing either view performance measurement (like the IS-VA™) or luminous intensity distribution measurement (like the IS-LI™). In addition, the ProMetric Imaging Colorimeter can be dismounted from the IS-SA system and be used in stand-alone mode under the control of ProMetric® Software.

Extensive control and analysis capabilities make measurement easy

The IS-SA is provided with Radiant Zemax' sophisticated Imaging Sphere control and analysis software. This software is built on the ProMetric Software engine, and supports measurement set-up plus automated and customized measurement sequences. Extensive data analysis and display functions are also supported, including isometric plots, cross-section graphs, radar plots, bit maps and color graphs.


Typical Applications

  • BRDF (bi-directional reflectance distribution function) measurement
  • BTDF (bi-directional transmission distribution function) measurement
  • Material characterization and classification based on scatter for metals, plastics, paper, textiles and more
  • Surface treatment characterization and classification based on scatter for cleaners, polishes, paints, coatings, and more
  • Quality control sampling
  • Generation of accurate and complete appearance models for optical design and rendering applications

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