Focal lenghths in a projector

[50joe]

Ok, This should be simple question, i know little about optics
when trying to make compact projector and dealing with the focal length of the fresnel, does a mirror setup effectivley increase the focal length of the light source??

like:


fresnel
^
|
|2cm
| 3cm
\ <-------------- ) light source
mirror


does this make the total distance from fresnel to light 5cm??
I only assumed this is how it works, because projectors are so compact with mirrors, and most fresnel's i find have like a 14in focal length. thanks!

 

[Lifter]

The focal length will be the distance to the light, so if you use a mirror, yes, it will be longer.

 

[bigtinker]

Ok, This should be simple question, i know little about optics
when trying to make compact projector and dealing with the focal length of the fresnel, does a mirror setup effectivley increase the focal length of the light source??

The focal length is static, so if you use a mirror it will not change. The mirror allows you to modify the shape of the case into a shorter and wider design, rather than having a tall rectangular box.

BT