After 20 years, production of Skalar IRIS IR Light Eye Tracker for oculomotor will come to an end this year.

It’s built up quite a reputation over the years for it’s robust and reliable performance having been used in countless studies worldwide. CRS have been exclusive distributors of the device for many years and will be taking new orders until the end of 2007 and spare part orders until the end of 2008.

Contact us straight away if you are looking to get hold of the Skalar IRIS contact us straight away, or why not take a look at some of our other options for eyetracking?

Skalar IRIS

The Skalar IRIS uses differential infrared light reflection to convert eye position into an analog voltage. It allows simultaneous horizontal or vertical eye movement recording of both eyes, or horizontal eye movement recording of one eye and vertical eye movement recording of the other eye. The measurement technique is based on the reflection of infrared (IR) light by the area on both sides of the edge between the white sclera and the darker iris. In this technique, IR light emitting diodes and IR light sensitive phototransistors are positioned respectively above and below the eye. IR light is projected onto the eye, both on the nasal and temporal side. A phototransistor transforms the reflected IR light into a voltage. The voltage of the nasally located phototransistors is subtracted from the voltage of the temporally located phototransistors. The voltage difference is demodulated and ampliflied, and the result is a signal which is proportional to the angular deviation of the eye. One of the features of the IRIS system is that the IR light emission is chopped. This permits eye movement recording with minimised interference from ambient light. And in combination with synchronous signal detection, it also improves the signal-to-noise ratio.

IRIS head-mounted measuring device

The head-mounted measuring device accommodates two IR light transducers (ILT). Each ILT consists of an array of nine IR light emitting diodes (LED) and nine IR light sensitive phototransistors. The detector array, which has the same dimensions as the LED array, is positioned below this LED array. The IR light is projected on the eye. Each detector corresponds with a particular part of the sclera or iris. The ILTs are coupled to a light weight adjustable helmet, which fits firmly around the head. For optimal alignment of the ILTs, each transducer can be adjusted independently in three perpendicular directions using rotative mechanisms. In addition, both transducers can be rotated around the horizontal axis. The transducers can be fixed to the helmet in two ways, enabling the recording of either horizontal or vertical eye movements.

IRIS electronic control module

The electronic control module incorporates an IR light generator part and a signal processing part. The chopped IR light emitters, with a chopping frequency of 2.5 kHz, are current driven. The eye movement modulated signal is band-pass filtered, demodulated and low-pass filtered (DC-100 Hz -3dB), resulting in the eye movement signal. An analog differentiator creates the velocity signal. Various indicator lights are located on the front panel, including two green LED bar arrays, indicating momentary eye position. With the aid of three markers, which are located at equally spaced intervals in the array, calibration is easy to perform. Calibration and adjustment are facilitated with the zero- and gain adjustments.

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