question for vision/display xpertz

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Offline trob

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question for vision/display xpertz
« on: 07/04/2009 14:41:03 »
Greetings to all!

My name is Tom; I'm 25 and I'm a student.

I have a research problem that I would like to share with you and I would really appreciate any constructive comments. Sitaution is somehow case related but (as always) needs some general clarifications to put it into perspective.

1.       Flicker: I was told that eye is very susceptible to flicker; researches like ERGs measure flicker responses of the retina; I was also told that one cannot say that eye has something like unified flicker response, since various types of cells respond differently. Does anyone knows what is the highest frequency (hz) that a healthy eye can detect and why flicker causes something like eye strain? (I got somehow unsatisfaying answers to this point)

2.       Display technologies: my »research« led me into consideration of different types of display technologies that one could take into consideration while dealing with research of what is previously addressed as »flicer«. As mostly of you know, are (especially) CRT monitors famous for their strong flickering discomfort issues. Of course; the electron gun »fires« dot per dot to activate phosphor; the lover the refresh rate, the more noticeable the flicker, the more strain we get. In general this seems logical; but it came to me- why in the first place would this type of image producing system caused eye strain, what acctualy happens in the eye, in the retina? (i belive that this is elementary question but bare with me and help me understand). Now onto LCDs: they are supposed to be flicker free; but they still have something like refresh rate and their baclight CFL(compact fluorescent lamp) also produces flicker albeit at very hight rates (kHZ). The human eye are supposed NOT to percive stimuli of this frequency, BUT it still does. (according to my references there are many people that find LCDs discomfortable) There are of coure LED backlight monitors, but their problem is PWM, a power saving technology that also produces flicker; this short overview is given merely to ask one essential question: What is »in« these popular display techologies that could provoke eye strain and discomfort? And to make this a little bit more precise; what if we say that various incanscendent light sources lack this strainig effect; where could one situate the problem? Is it really the flicker the general issuse that is problematic or we need to address the particularities of each display technology to establish its straining potency?

Thank you for your time.

Best regards;


Offline lightarrow

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question for vision/display xpertz
« Reply #1 on: 07/04/2009 20:02:00 »
Hi Tom!
Your question doesn't seem very simple even if something can be said. I don't think flickering is just a phisiological effect, maybe it's psychological too (don't mean that it's not real but that it's more complex); anyway people more educate in this field can tell you. About incanscendent light sources, I think the reason is their "inertia": when the current drops, the metal can't cool down immediately and so it keeps emitting (in a damped way) light, so the intensity variations of light is less "brutal".