Last Updated
  20th Oct 2006 

Pattern Stimulator

[Ordering Information], [Features], [ISCEV Compatibility],
[Software Control], [Calibration], [Stand-alone Option]

 

Pattern Stimulator

The powerful Pattern stimulator option brings monochrome and color VEP and PERG capabilities to the Espion diagnostic suite. Stimulus pattern, size, frequency, contrast and color are all computer controlled and all displays are fully gamma corrected for accurate stimulation. Diagnosys offer two different pattern stimulators; one aimed primarily at the clinical market (PSG) and the other at the research market (VSG), although both are more than capable of providing the full ISCEV set of stimuli.

Ordering Information

Part No

Description

D143-VSG

Pattern Stimulator (VSG) including 19" monitor >100cd/m2

D143-PSG

Pattern Stimulator (PSG) including 19" monitor >100cd/m2

D175

Stand alone controller box (PSG only)

VSG Features (Research)
 

PSG Features (Clinical)
 

  • Checkerboards, bars, gratings as standard with single pixel resolution
  • No partial checkerboard squares
  • Full field, half field, quarter field patches, arbitrary patch size/position
  • Variable size/color/type fixation spot
  • Gratings in any orientation
  • Full control of reversal rate and onset/offset with frame accuracy up to half frame rate
  • Adjustable trigger timing
  • 15 bit luminance/contrast control
  • Calibrated luminance and color
  • Configurable monitor timing
  • Resolutions up to 2048*1024
  • Frame rates >250Hz (monitor dependent)
  • Full support for different monitors
  • Ability to custom program
  • Based on framestore memory
  • Arbitrary stimuli shapes
  • Internal PC card fitted in the console
  • Must be ordered with console
  • Checkerboards, bars, gratings as standard with two or five pixel resolution
  • No partial checkerboard squares
  • Full field, half field, quarter field patches only
  • Variable size/color/type fixation spot
  • Gratings in one orientation only
  • Full control of reversal rate and onset/offset with frame accuracy up to half frame rate
  • Adjustable trigger timing
  • 8 bit luminance/contrast control
  • Calibrated luminance and color
  • Preset monitor timing
  • Fixed resolution 800*600
  • Fixed frame rates of 90/100Hz
  • Restricted support for different monitors
  • No custom programming
  • No framestore memory
  • No arbitrary stimuli shapes
  • External stimulator box
  • Can be ordered at anytime
ISCEV Compatibility

ISCEV Test

Compatibility

Pattern Reversal

The Pattern Stimulator can not only produce the ISCEV standard size checks of 1, 30 minute and 15 minute subtended at the eye, but also at virtually any size in a far wider range depending on the viewing distance.

It produces square or sine wave gratings at any angle (VSG only) at the ISCEV standard sizes of 0.5, 1.0 and 2.0 cycles per degree, and also any size check in a far wider range depending on the viewing distance.

The viewing distance is adjustable to ensure that at least 15 of visual field is stimulated, and the pattern reversal rate is selectable up to 30Hz or more. The stimulus is arranged with equal areas of black and white or color to ensure constant luminance on reversal.

Pattern Onset/Offset

The same patterns are produced for onset/offset stimuli. Onset/offset times are adjustable, and include the ISCEV standard of 200ms on, 400ms off. A mean luminance background is automatically created.

Software Control

The software can control all aspects of the stimulus, including type, size, contrast, color, temporal frequency, and patch size. Checkerboards can be made to reverse at any frequency that is a multiple of the frame rate (100Hz = 10ms resolution) to a limit of half the frame frequency. Stimuli can also be made to appear and disappear on a mean luminance background for performing PERG type tests. The fixation points can not be selected from the standard cross and square shapes, but also provide feedback to the patient about the remaining time left to run.

Calibration

Calibration of the monitor for color and luminance accuracy is fully supported. In the case of the PSG, the system has an integrated calibration routine which when interfaced to the recommended Diagnosys photometer will automatically create the gamma correct curves for all three phosphors. The VSG requires external 3rd party software (supplied) which can be coupled to either the recommended photometer or one supplied by the manufacturer of the board. Color calibration requires a colorimeter or similar to read the three phosphor CIE coordinates which can then be entered into the system. Finally the screen size must be calibrated by measuring a known size area of pixels to make spatial size and viewing distance calculations correct.

Stand-alone Option

The PSG pattern stimulator can be provided as a stand-alone stimulator with RS232 control for connection to existing 3rd party acquisition systems. The system allows the reversals to be be triggered by an external device, or can provide an external trigger synchronized with the reversal or pattern onset. Contact Diagnosys for more details.


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