1. It can achieve high luminance resolution. Most computer displays have
8-bit luminance resolution which is too coarse for some vision experiments,
such as contrast threshold measurement. By sacrificing color display, a video
switcher can increase the luminance resolution. This is the same as Pelli-Zhang
video attenuator.
2. It is designed to drive a color monitor. Unlike the Pelli-Zhang's
passive resistor network, video switcher is designed to drive a color monitor
to show grayscale images, although it can
also drive a monochrome monitor.
3. It can be toggled between normal color and high grayscale display. You can switch between grayscale mode (experiment) and color mode (normal use) by program, and/or a button. With this functionality, single monitor setup is enough for most vision experiments.
4.
It can generate
an accurate trigger to synchronize the recording with visual stimulus.
， Bandwidth:
250 MHz
， Input
and output impedance: 75 W
， Input
and output connectors: VGA
， Blue to
red ratio: ~127
， Trigger
output: ~4 V, 100 µs
， Power
supply (box version only):
， Special specifications may be available upon user request
The device can be used on any
computer with 8-bit color video card with analog output
Video switcher does not have special
requirement for software. We recommend free Psychtoolbox
in MatLab,
which implements a convenient and effective way to use the device. We have a demo code showing how to use it in Psychtoolbox.
Video switcher is designed to
connect between computer¨s video card and analog monitor. Connect the input of the
switcher to your computer's video port with the supplied cable, and plug the
monitor¨s cable into the switcher¨s output port. If you need the trigger
pulses, connect the BNC output to your recording device with a cable (not
supplied). You can download the user manual here.
， The color display mode does not have
high luminance resolution, and it is designed for normal use other than visual
stimulus. Remember to switch to the high grayscale mode when displaying visual
stimuli, either by calling a function or by pressing the button for the box
version.
， To ensure accurate trigger timing, you must set on the green value only in the display region. For detail information, check the offprint.
The price is $280 each for
switcher box, plus shipping and handling, which is about $35 for one, and $10 each for additional ones.
If you like to make an order,
have question or suggestion about the video switcher,
please contact us by email xiangrui.li@gmail.com
or zhonglin@usc.edu .
Last updated on 9/22/2011