What's the difference between sandwiching the lcd with fresnel lens and just having the fresnels side by side? If they're side by side, which way should the rough sides be pointed?
split vrs non-split
When both fresnels are together (rough sides facing each other) before the LCD, that is called a non-split design. The image will be a bit sharper since the light from the LCD goes directly to the projection lens, but you may see some artifacts in the image from the different angles of the rays far from the center.
When the condensor fresnel is at least 20 mm before the LCD, and the field fresnel about 20 mm after the LCD (rough sides both facing the LCD), that is called a split design. The image will be a bit blurry and distorted by passing through the fresnel, but the nearly parallel rays through the LCD may give you a more evenly lit image with no viewing-angle artifacts. You can also tilt the field fresnel to do some optical keystone correction, if you need to mount your projector on the ceiling.
When both fresnels are together (rough sides facing each other) before the LCD, that is called a non-split design. The image will be a bit sharper since the light from the LCD goes directly to the projection lens, but you may see some artifacts in the image from the different angles of the rays far from the center.
When the condensor fresnel is at least 20 mm before the LCD, and the field fresnel about 20 mm after the LCD (rough sides both facing the LCD), that is called a split design. The image will be a bit blurry and distorted by passing through the fresnel, but the nearly parallel rays through the LCD may give you a more evenly lit image with no viewing-angle artifacts. You can also tilt the field fresnel to do some optical keystone correction, if you need to mount your projector on the ceiling.
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