Hello,
I have a optics related question for those of you that have already build a projector and removed the backlighting from the panel.
The question is: when the LCD cell is turned on ( light passes through the RGB filters) a straight ray of light will pass though keeping the same direction, like passing a colored glass, or there is a diffusion of the ray?
In other words, if you connect a video signal to the panel showing a white screen ( blank MS Word document for example) and you look behind the LCD (may be its better to have the lamp off 🙂 can you see the box, lamp and the other stuff behind the LCD like through a glass window?
How much blurred is the image?
Thank you,
best regards,
Mark
I have a optics related question for those of you that have already build a projector and removed the backlighting from the panel.
The question is: when the LCD cell is turned on ( light passes through the RGB filters) a straight ray of light will pass though keeping the same direction, like passing a colored glass, or there is a diffusion of the ray?
In other words, if you connect a video signal to the panel showing a white screen ( blank MS Word document for example) and you look behind the LCD (may be its better to have the lamp off 🙂 can you see the box, lamp and the other stuff behind the LCD like through a glass window?
How much blurred is the image?
Thank you,
best regards,
Mark
It seems to be diffused a bit. It is possible to make out a few shapes but it's not like looking through a window.
Thanks a lot.
Now I understand why some people are adding a fresnel lens also after the panel. If the panel was completely transparent you could keep all the fresnels behind the lcd and adjust the focus of the light to the lens, and then put the panel onto the path.
If we have diffusion we must recollect the colored light after the panel to refocus it to the main lens.
Thanks again,
ciao,
Mark
Now I understand why some people are adding a fresnel lens also after the panel. If the panel was completely transparent you could keep all the fresnels behind the lcd and adjust the focus of the light to the lens, and then put the panel onto the path.
If we have diffusion we must recollect the colored light after the panel to refocus it to the main lens.
Thanks again,
ciao,
Mark
Many people do put both lenses behind the screen, and focus to the screen (not the fresnels). It suffers a little bit as far as brightness and uniformity are concerned, because an LCD transmits the most light at 90 degrees to the plane of the LCD. However this method results in a sharper picture because focusing through a fresnel adds a little blurriness. Though the blurriness is minimal with good fresnels and most people don't notice.
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