another weird brain trick

[inhumandecency]

A little while back, I noticed that when I'm looking at a white part of an LCD projection -- either at the screen or (sidelong) at the light coming out of the projector -- something odd happens: If I move my head, I get tracers that very clearly decompose the image into red, green, and blue copies

Comments

[leifbrown]

Perfectly normal.

Just a persistence-of-vision effect with a low-refresh light source.

(three of them, in different colors)

[inhumandecency]

But it's sending all three colors at the same time, isn't it? How could I possibly dissociate them after they've hit the screen?

[inhumandecency]

Okay, per tanjent's comment, that's exactly what it's not doing. So now it makes sense. Thank you!

[tanjent]

To clarify Leif's comment, DLP projectors display each color component in the image separately - the projector shines white light through a spinning transparent wheel that is divided into red, green, and blue segments. The wheel causes blue light to shine on the DLP chip for N milliseconds, then red light, then green light. Normally the intervals between colors are so small that your eye blends them together, but if your eye moves quickly the separate colors end up projected onto different portions of your retina, producing the rainbow effect.

LCD projectors, 3-chip DLP projectors, and LED-based DLP projectors don't produce this effect (the latter because the duration of the light pulses can be 10x faster than using a color wheel).

[inhumandecency]

Okay, that really does explain everything. I assumed it was projecting three monochrome images at once, so I couldn't see how they could be separated after they've bounced off the screen. Thanks!

[memeatron]

"a) Does this happen to other people?"

All the time.