Projecting zoom lens system and projector apparatus
First Claim
1. A projecting zoom lens system having a telecentric incidence side comprising a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power and a fourth lens group having a positive refractive power, arranged in this order from a screen side, whereby zooming is carried out by fixing said first and fourth lens groups and moving said second and third lens groups, wherein said third lens group comprises a forward group disposed toward the screen side and a rearward group disposed toward the incidence side, and a distance between said forward and rearward groups is controlled during zooming.
1 Assignment
0 Petitions
Accused Products
Abstract
A projecting zoom lens system whose incidence side is telecentric of this invention is formed by the first to fourth lens groups arranged sequentially from the screen side and having negative, positive, negative and positive refractive powers, respectively. The employment of the negative refractive power lens group on the screen side allows a wider angle and a smaller lens aperture of the first lens group, thereby realizing a compact lens with a larger aperture as a whole. Furthermore, if a positive lens is employed on the screen side in the first lens group of the projecting zoom lens, the balance of refractive power can be improved.
-
Citations
10 Claims
- 1. A projecting zoom lens system having a telecentric incidence side comprising a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power and a fourth lens group having a positive refractive power, arranged in this order from a screen side, whereby zooming is carried out by fixing said first and fourth lens groups and moving said second and third lens groups, wherein said third lens group comprises a forward group disposed toward the screen side and a rearward group disposed toward the incidence side, and a distance between said forward and rearward groups is controlled during zooming.
- 4. A projecting zoom lens system having a telecentric incidence side comprising a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power and a fourth lens group having a positive refractive power, arranged in this order from a screen side, whereby zooming is carried out by fixing said first and fourth lens groups and moving said second and third lens groups, wherein said third lens group or fourth lens group comprises at least one lens component whose incidence side surface is an aspherical convex surface.
-
7. A projecting zoom lens system having a telecentric incidence side comprising a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power and a fourth lens group having a positive refractive power, arranged in this order from a screen side, whereby zooming is carried out by fixing said first and fourth lens groups and moving said second and third lens groups, wherein a resultant focal length of said first and second lens groups at a wide-angle extremity fw12 and a resultant focal length of said third and fourth lens groups at the wide-angle extremity fw34 satisfy the following condition:
space="preserve" listing-type="equation">0.3<
(fw.sub.12 /fW.sub.34)<
1.5.- View Dependent Claims (8, 9)
Specification