head> Clinical Grating & Gabor Generator - Dr Grant Hannaford

AAOO / Dr Grant Hannaford – Clinical Grating & Gabor Generator

Full-field pattern gratings and cogsci-style Gabor patches, calibrated in cycles/degree for a given screen and viewing distance.

Screen width (mm)

Measure with a ruler (visible display area).

Screen width (pixels)

Horizontal resolution from display settings.

Viewing distance (mm)

e.g. 400 mm = 40 cm (typical near distance).

Spatial frequency (cycles/degree)

2–8 c/deg: typical “pattern glare” range.

Orientation (degrees)

Angle of bars; 90° ≈ vertical bars.

Phase (cycles; 0–1)

Shifts pattern along its axis.

Contrast (0–1, Michelson)

1 = full Colour 1/2; 0 = uniform mid-tone.

Waveform type

Gabor uses the cogsci.nl generator logic with a chosen patch diameter.

Envelope type

For Gabor, any of these envelopes can be used (Gaussian standard deviation below).

Gaussian σ (degrees)

σ for Gaussian envelope, used in both full-field and Gabor modes when envelope = Gaussian.

Canvas size units

Values below are interpreted as pixels. Select millimetres to specify physical size.

Canvas size

Width

Height

Lock aspect ratio (unlocked)

Currently treated as pixels. Change units using “Canvas size units”.

Field of view (degrees)

Horizontal FOV

Vertical FOV

Lock field of view in degrees

When FOV is locked, canvas width/height are derived from these degrees and your px/deg calibration, overriding the size inputs.

Colours

Background R

Colour 1 R

Colour 2 R

Contrast scales the difference between Colour 1 and 2 around their mid-tone; background is unaffected.

Gabor patch diameter

Used only when waveform = Gabor. Patch is drawn centred in the canvas.

Pattern glare presets (Wilkins-style)

Presets set: square-wave, contrast = 1.0, vertical bars (90°), and the specified spatial frequency.

Export settings (for clinical notes / research logs)

Settings update automatically every time you draw a new stimulus. The PNG download captures the current canvas.

Clinical note: ensure the subject sits at the specified viewing distance with no browser zoom or OS scaling changes. For pattern glare, mid spatial frequencies (~3 c/deg) and large field size are typically the most provocative.