| Hezz |
After having spent several days at an optical comparator measuring parts I have observed a few things that I hadn't really thought of before that might be exploited to build better quality LCD projectors
How many of these principles carry over into the world of LCD projection I don't know but two things I have observed are apperant. I have also observed some of these things in photographic pictures.
Opaque objects that are lite from the rear only have lower image detail around the edges than do front or side lite objects. They also have lower contrast.
I wonder if we can exploit this principle in LCD's by using the new high brightness transreflective LCD's and light the LCD somewhat from the front in addition to the rear light engine.
This might improve overall contrast and image detail if done correctly.
Hezz |
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| bobharry |
| Sounds like it could be good, but how would you get the lamp for the front in the right pace? As the right place would be in the light-path. |
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| Hezz |
The front lights would be bounced off from the LCD at an angle from four directions. They are not completely direct lights and can be small diffuse lights mounted on each side of the lens internally.
They will work best if they are at an angle anyway as most of the LCD brightness will come from the rear light engine. The front lights help to better illuminate the LCD. The LCD needs to be of the Transreflective variety.
Hezz |
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| bulldog5046 |
is this what you ment? i have seen some OHPs that work in this way.
Thanks,
Ryan Edge |
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| Hezz |
Bulldog,
My idea was somewhat different but I think yours would work also. I will post a sketch shortly.
Hezz |
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| Hezz |
Here's the idea. The light engine from the rear is the standard variation that most are using.
The LCD is a transreflective LCD instead of the standard transmissive type which most are using.
The area in front of the LCD is lined with a highly diffusive and reflective material like frosted glass backed by a reflective coating.
Some kind of daylight wavelength moderate brightness light source is placed inside the diffusive area to produce an even high ly diffused light area inside the lining of the box.
All objects are kept out of the way of the primary rear light engine light cone.
The transreflective nature of the LCD reflects the diffusive light off from the front of the LCD in many paths which bounce around inside of the light box thus evenly illuminating the LCD from all side and all angles. The lens will eventuall capture much of this light and with the primary light cone will create a better more defined and illuminated image of the LCD. So long as hot spots and direct reflections can be avoided.
Hezz |
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| bulldog5046 |
ehhh...............ooook i think i understand, i think the way i suggested may make it slightly briter and by the way the fresnal goes between the lcd and the glass.
Thanks,
Ryan Edge |
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| Hezz |
Bulldog,
What glass are you talking about? There is no glass in this sketch other than the lens representations. The LCD must not be between the fresnels but the system can work both ways. In this example the fresnels are doubles back to back which is the more common orientation.
Your design would reflect more light but it does not use any of the light from the back. My point was to illuminate the LCD from both sides and use a transreflective LCD.
Hezz |
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| bulldog5046 |
i ment on my design the fresnal would be placed between the lcd and the bottom mirror.
Cheers,
Ryan Edge |
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