Like the Picometer Ellipsometer, the Imaging Ellipsometer is based on the phase modulation technique which due to its intensity throughput and lack of insensitive regions is especially suited to imaging. Unlike conventional null ellipsometers that are based on rotating polarisers, the Imaging Ellipsometer will retain its high sensitivity even under difficult measuring conditions. This especially important for applications in unstable environments, such as when investigating liquid surfaces.

In the Imaging Ellipsometer, the light from the light source is passed through a fixed polariser and then through a continuously rotating retarder which is phase locked to the camera's frame rate. The rotation speed can be altered to either optimise the signal noise or to achieve a higher imaging frame rate. The system can deliver a full ellipsometry image in up to 0.5 s. If the application does not require true ellipsometric measurements, the retarder can be held at a fixed position and the imaging system can be run at the full frame rate of more than 100 frames/s. The instrument then acts as a Brewster Angle Microscope.

The imaging is done with a high speed CCD camera through a microscope lens. The magnification of the imaging optics is continuously adjustable up to a maximum lateral resolution of 3 µm per CCD pixel.

In the standard version of the instrument, the full CCD area has 256x256 pixels. Within this area, the operator can select a working window of arbitrary size and location. A high speed PCI bus framegrabber allows the rapid transfer of images from the CCD to the computer, which processes the image data to calculate the final ellipsometry image. A full frame ellipsometry image can be obtained with a sensitivity of 10^-3 in Im(r) and Re(r) in about 1 s. Thus for the same observing time the sensitivity is about a factor of 100 less than that of the Picometer Ellipsometer, which is consistent with a variation proportional to the square root of the number of beams (pixels) observed during that time.

As in the Picometer Ellipsometer, the control software for the Imaging Ellipsometer is based on the IgorPro data analysis program. A complete range of image analysis features are available including filters, FFT, and surface plotting. The software is fully compatible with the Picometer Ellipsometer software and even allows the same analysis routines to be applied to both 1- and 2-dimensional data.