Barry A. Watzman wrote:
When looking at a square wave, it is normal for the
horizontal tops and bottoms to be brighter/thicker than the vertical segments. The linear
speed of the beam when drawing the vertical lines is MANY times (sometimes hundreds or
thousands of times) faster (in mm/second of beam travel) than when drawing the horizontal
tops and bottoms, which results in a difference in the nature of the display.
Unless it's extreme, which may be harmonics or other noise distortion. Florescent
lighting is great for this by adding a nice thick top that sometimes dances or is haloed.