what fresnel for my focal length- noob

killerofangels · 20th May 2006, 05:47 PM

I am using a projection lens with a 22mm focal length. I can get an image by just placing my lcd about that far away but at that distance I can only see the center of the lcd's image. Can I use a fresnel lens to be able to move the lcd further away or do i just have to use a smaller lcd?

milihpen · 20th May 2006, 07:12 PM

You're going to either need a much smaller LCD panel or a lens with a longer focal length.

Zanteeh · 22nd May 2006, 06:26 AM

220mm o 22mm?

22mm it's quite little

Your fresnel must have, accordin to people says, a similar focal length

The distance fresnel-projection lens should be almost the same Focal length.

Focal length is the distance from where the lens focus light to a simple point, so you have to aim this point inside the projection lens

The fresnel lens, put in front of the lcd, would make the image a cone facing the projection lens, so it will 'enter' into it

20th May 2006, 05:47 PM	#1
killerofangels diyAudio Member Join Date: Feb 2006 Location: east coast	what fresnel for my focal length- noob I am using a projection lens with a 22mm focal length. I can get an image by just placing my lcd about that far away but at that distance I can only see the center of the lcd's image. Can I use a fresnel lens to be able to move the lcd further away or do i just have to use a smaller lcd?

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20th May 2006, 07:12 PM	#2
milihpen diyAudio Member Join Date: Dec 2005 Location: USA	You're going to either need a much smaller LCD panel or a lens with a longer focal length.

22nd May 2006, 06:26 AM	#3
Zanteeh diyAudio Member Join Date: Apr 2006 Location: Argentina, Rosario	220mm o 22mm? 22mm it's quite little Your fresnel must have, accordin to people says, a similar focal length The distance fresnel-projection lens should be almost the same Focal length. Focal length is the distance from where the lens focus light to a simple point, so you have to aim this point inside the projection lens The fresnel lens, put in front of the lcd, would make the image a cone facing the projection lens, so it will 'enter' into it

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