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Target Indicator Joysck Arrows
wider the pulse, the brighter the flash from the LEDs appears to be. There is
however, a downside to the wider pulses. All strobes work by giving short
bursts of light (the pulse width) at a rapid repetition rate (the flash rate).
Strobes rely on the persistence of the human eye (the ability to remember
and image) and its response to bright light to give an apparent stop motion
image. Imagine a shaft rotating at 6000 RPM or one rotation every 1/100 of
a second (10 msec). If the strobe flashes once every 10 msec for a brief
moment, the user sees the flash at the same spot in the rotation of the shaft
and the persistence of the eye remembers this until the next flash making
the shaft appeared to be stopped. As the target is rotating there is some
movement evident during the strobe flash. The longer the flash duration,
the more obvious the rotation is and this increases the blur.
6.1
Calculang Blur
Blur can be calculated–
if the sha7 is turning
at 6000 RPM, it takes 10 msec to complete
one revoluon. If the strobe flash duraon
is 100 µsec (1/100 of a millisecond), the
sha7 will turn: (flash duraon/me per
rotaon) x 360°, which is (.0001/.01) x 360 =
3.6°. So you will see the sha7 appear to
move 3.6°.
As the flash pulse widens you will see greater
degrees of rotaon which results in more
blur and a brighter perceived illuminaon
(the LEDs are on longer so the average light
the eyes see is greater). The trade off is blur
versus brightness. The further away the rotating point is from the
center axis the faster the tangenal velocity and the worse the blur
appears to be.
17
1°degree of
movement
5°degrees of
movement
