The Imaging Sphere Scatterometer

Imaging Sphere IS-SA Scatterometer

Ultra Fast BRDF & BTDF scatter & appearance analysis of materials

The Imaging Sphere IS-SA is an innovative, ultrafast goniometer for instananeous BRDF (bi-directional reflective distribution function) & BTDF (bi-directional transmissive distribution function) scatter and appearance measurements. With the Imaging Sphere, you measure the scatter distribution for all angles of reflection or transmission for one angle of illumination at a time, which makes it several orders of magnitude faster than traditional goniometric scatter measurement instruments.

BSDF Measurement for Almost Any Material or Surface Finish

The IS-SA (the SA stands for scatter and appearance) 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 characterisation 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 photo-goniometric BSDF measurement devices.

Instantaneous Hemispherical Scatter Data

Accurate modeling of surface appearance 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 millions of simultaneous measurements, the Imaging Sphere captures 2pi steradians (a full hemisphere) of scattered light in a single measurement, dramatically reducing the time required to obtain a BSDF measurement. If the speed of the Imaging Sphere sounds too good to be true, all will be revealed in our technical briefing.

The IS-SA captures an entire hemisphere’s worth of scatter data, including both luminance and colour, in a single measurement for a given angle of illumination. The illumination angle is set through software, from the surface normal up to 80°. The angular resolution of the system is determined by the number of pixels on the camera’s image sensor and is nominally <0.5°.

Multiple Configuration Options Meet Multiple Needs

The standard configuration of the IS-SA provides for measurement of BRDF and it is available with a choice of 16-bit ProMetric imaging photometers. The PM-1603F-1 has a 512 × 512 pixel resolution or a higher sensitivity PM-1613F-1 colorimeter offers 1024 × 1024 pixel resolution.

Illumination of the sample is provided by means of a tungsten halogen or metal halide white light source as standard. An optional tunable light source provides the ability to measure BSDF as a function of wavelength.

For very glossy samples, the IS-SA can be equipped with optional automated port covers for exclusion of the specular component of the reflectance.

Various mechanical extensions are available to increase the range of measurements that can be taken and to increase automation. With the optional Transmission Arm attachment, the illuminator can be positioned to illuminate the material sample for transmissive BTDF measurements. 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 photometric and colorimetric testing needs. Because of its reconfigurable hardware and software design, the IS-SA user also has the option of performing view angle testing of displays (the IS-SA then operates as an IS-VA) or performing luminous intensity measurements on LEDs and other small light sources (per the IS-LI). In addition, the ProMetric Imaging Photometer can be taken off the Imaging Sphere dome and used in stand-alone mode under the control of (optional) ProMetric software.

Software Provides Simple Control & Advanced BSDF Analysis

The IS-SA isoftware is built upon the ProMetric Software Engine and supports automated and customised measurement sequences. Extensive data analysis and display functions are also supported, including isometric plots, cross-section graphs, radar plots, bit maps and colour graphs.

IS-SA software supports a variety of export formats which allow you to share BSDF data directly with your chosen optical design and modelling software. The following formats are currently supported:

Generic ASCII
Light Tools
SPEOS (versions 2 & 3)
TracePro
Zemax
ASAP