The FS-250A LED Ganzfeld is a research and development tool, recommended for University departments and research institutes studying the fundamentals of vision. The FS-250A LED Ganzfeld, available from Photometric Solutions International , consists of a 200mm diameter sphere internally coated with a high-reflectance diffuse white paint and illumination is provided by internal arrays of white LEDs.
The sphere has a port in one side which is used as the location of the test subject’s visual plane. The subject’s field of view is then limited to the far wall of the sphere. If small animals are being used, the system comes with a platform for the animal to lie on which can be temperature controlled by circulating warm water through the platform.
The LED module in the Ganzfeld has three separate banks of LEDs to provide illumination. A PCI interface card uses analogue outputs to drive the LEDs at different programmable voltages and pulse durations, and digital I/O to switch relays to set different ranges (brightness levels) for the LED banks.
Software provided with the system enables the operator to provide a continuous background luminance to set adaptation level and also programme in the required pulse stimulus pattern with a variety of options and programming functions.
There is a continuous dynamic range of around 9 orders of magnitude, from the peak output of the high intensity pulse bank to the lowest stimulus from the low intensity pulse bank. At the start of the pulse sequence a digital trigger output can be used to initiate data acquisition on EEG reading equipment such as the ADI PowerLab.