Peter. But that's unimportant. Thanks for the great explanation folks. I
appreciate it.
-----Original Message-----
From: Eric L. Strobel [mailto:fyzycyst_at_comcast.net]
Sent: Thursday, May 30, 2002 1:29 PM
To: newtontalk_at_newtontalk.net
Subject: Re: [NTLK] Oily swirly looking pattern on screen?
on 5/30/02 4:19 PM, Humphreys, David (URB) at david.humphreys_at_honeywell.com
wrote:
> Ah ha! Good old Newton's Rings.
>
> This is very easy to explain.
>
> Newton's Rings are formed by the constructive and destructive
> interference of light rays as they pass through a medium that
> refracts to various degrees.
>
> On the Newton, the LCD glass has a plastic touch screen on top.
> The touch screen is separated by a tiny amount from the glass.
> When the screen is pressed, that part moves closer to the LCD
> glass.
> A ray of light can reflect off the bottom surface of the touch
> screen or reflect of the top surface of the LCD glass.
> Due to the fact that the ray travels a wee bit further to the
> LCD then the touch screen, it will be slightly out of phase
> with the touch screen reflected one.
>
> Now for the magic...
>
> If two signals are 180deg out of phase, they cancel.
>
> If they are in phase, they add.
>
> If they are anything in-between then they add or cancel a little bit
> depending on their relative phase difference.
>
> So, the upshot of all this is that you get dark patches where there
> is cancellation, light patches where there is addition and Grey
> patches in-between. (actually, the in-between will be colored but
> lets keep things simple).
>
> On certain peoples Newton's, the space between the touch screen and the
LCD
> will vary and can change with time/temperature/pressure/humidity so
> these rings will manifest themselves from time to time.
>
> Annoying but no harm, these rings cannot be washed away as they are not
> a physical but a visual phenomenon.
>
> And there are definitely no liquids involved here but the same kind
> of phenomenon can be observed when oil and water mix.
>
> PCBman
>
>> If it's like my ump2000, it is caused by contact between the
>> actual LCD
>> glass and the protective writing surface that 'floats' above
>> it. I'm not
>> sure if there is some sort of fluid in between the two, but
>> that's the look
>> of it, oily and rainbowy (is that a word?).
>>
>> Cleaning my screen does nothing to counteract this, and the better the
>> lighting in the room, the less noticeable the phenomenon...
>>
>> --
>> Joe Anthenat ><>
Good explanation (although, IIRC, the colors are due to the gap's thickness
being the amount needed to cause constructive reinforcement of that
wavelength of light). A year & a half of Newt-ing and that's the first I
recall hearing of this. Fascinating... *lifts eyebrow in Spock-like
manner*
I suppose that means this Joe's screen has the touch membrane deformed
slightly for whatever reason...
- Eric.
--Eric Strobel (fyzycyst_at_NOSPAM^mailaps.org)
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