Date: Fri, 12 Oct 2001 08:47:21 +0800 From: Raymond <[EMAIL PROTECTED]> Subject: Re: [LIB] Re: [LIBRETTO] Re: Nuts and bolts of impoving LCD
>>>Looking over how the light originates from the rear, I wouldn't >think that even >using a mirror back there should cause image >doubling, as what comes from the back >is only white light. >> >>Problem is if light is coming in the FRONT then the light passes through the image >layer TWICE. Just look at your wristwatch from the side under a relatively direct >source of light to see this. > >Okay... so light entering from the front may be able to do this to some extent... but >I would think that mirror in the rear would strengthen >the fluorescent bulb's light output through the front of the panel to a greater >degree than a diffusion backing. Umm ... the 'backlight' has to diffuse off SOMETHING otherwise all you'd get is light at the bottom of the screen. That diffusion layer has had more thought put into it than one would think at first. For instance, getting something that'll give the impression of a constant, even backlight from the very top of the screen to the very bottom of the screen where your only illumination is a lamp at the bottom of the screen is a non-trivial matter. > Mirrors HAVE been used in other LCD constructions from what I've read (albeit the >ones I read about were primitive). Yep, such as wristwatches, pocket calculators and palm devices. The only reflective screens that have had any measure of success however have been those in the GameBoy Advance and on some Casio graphic calculators (although the clarity and color of those screens is debateable - ref my speal about silvered backings earlier on). I've not seen the screen of a Sony Clie however which also uses a reflective color screen ... presumably its better though ... unfortunately it doesn't exist in Australia so I've never seen it :-/ > If a filter was applied to the front of the panel that blocked light entering from >any angle except from straight ahead, say at about an 7 degree spread... do you think >that the screen image created by brighter fluorescence and a mirror backing might >overpower any doubling of the image from light entering from the outside? Umm ... sunlight is pretty damn bright. You go get a torch (or even your car headlights on full beam) which, at night would probably blind you, and turn it on in full sunlight. You would be hard pressed to even see the beam. Now I very much doubt you'll be able to get a lappy backlight to even go a quarter of the intensity of such a beam. >I'm assuming that whatever the material is on the back side of the illumination layer >does NOT have a reflective layer of any kind behind it, and that some light being >generated by the fluorescent bulb(s?) is lost through the back side of the >illumination/diffusion layer. Light isn't lost through the diffusion layer, its diffused. If any reasonable amount of light was getting lost through the diffusion layer you'd feel a considerable amount of heat generation from the center of the panel (the panel top, bottom and left may get hot in normal use but remember there are heat vents under the hinges and there is an inverter on the far right of the panel). >>>Increasing the source fluorescent lamp(s) output is obviously a must. >> >>Is it? Wouldn't it be better to use reflected light so the 'intensity' of light >coming off the panel is proportional to ambient light? > >Wouldn't it be good to set things up so that the light output from the LCD is greater >than the ambient light? I kind of thought that the ambient light being brighter than >the LCD light output was what the problem was. Wouldn't pumping up the lamp output >help there? Like I said, making a backlight bright enough for this is a non-trivial matter. Just look at the handheld PCs such as the Compaq iPaq - its got a backlight several times brighter than the libby yet it still has problems in bright sunlight. >>> But I wonder if increasing the voltage to the TFTs would rotate > the LCs more >and get the light angle more aligned with the front > polarizing filter. >> >>Its not power that rotates the LCs, its electric field. And the intensity of that >field effectively determines how far on or off each pixel is in terms of blocking >light. > >That's what I was struggling to say. I'm a bit new top all this. Not fully >understanding how things work, I thought that more voltage to the TFTs may create a >stronger field, and thus rotate the LCs to better align their light angle to the >polarizing layer. Though if Toshiba already has set things up so that the two angles >coincide, rotating any further would begin to dim the display, right? Yep -- Raymond ************************************************************** http://libretto.basiclink.com - Libretto mailing list http://libretto.basiclink.com/archive - Archives http://www.picante.com/~gtaylor/portable/faq.html - FAQ -------TO UNSUBSCRIBE------- Reply to any of the list messages. 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