Compact projection lens
AssigneeU.S. Precision Lens Incorporated
InventorEllis I. Betensky
Life of this patent
Estimating the term…
Abstract
A compact projection lens for a cathode ray tube comprises from the image end, a first group of positive power which corrects aperture dependent aberrations, a second positive group and a third group which corrects for field curvature and distortion. A mirror is inserted between the first and second groups to fold the optical axis.
Claims27
A projection lens for a cathode ray tube display, said lens consisting of three groups from the image end to the object end, as follows:
- a first group comprising an element of relatively weak optical power having at last one aspheric surface;
- a second positive group air spaced from said first group providing substantially all the positive power of said lens;
- a third group air spaced from said second group and comprising a negative element having a surface concave to the image end and serving as a field flattener essentially correcting the Petzval curvature of the first and second groups;
- wherein said three groups have optical powers K1, K2, and K3, the overall lens has an optical power of 1.0, and
- 0. 25<K1<0.50,
- 0.85<K2<1.20,
- -1.4<K3<-0.9
A projection lens for a cathode ray tube display, said lens consisting of three groups from the image end to the object end, as follows:
- a first group comprising an element of relatively weak optical power having an aspheric surface and serving to correct aperture dependent aberrations;
- a second positive group air spaced from said first group and providing substantially all the positive power of said lens and comprising a biconvex element;
- a third group air spaced from said second group and comprising a negative element having an image side surface concave to the image end of strong negative power and a substantially plano object side surface, said third group essentially correcting the Petzval curvature of said first and second groups;
- said three groups have optical powers K1, K2, and K3, the overall lens has an optical power of 1.0, and
- 0.25<K1<0.50,
- 0.85<K2<1.20,
- -1.40<K3<-0.9
A projection lens for a cathode ray tube display consisting from the image end of three groups as follows:
- a first group of relatively weak optical power comprising an element having at least one aspheric surface and serving primarily to correct aperture dependent aberrations,
- a second positive group air spaced from said first group providing substantially all of the positive power of said lens, and
- a third negative group air spaced from said second group comprising an element having a concave image side surface and serving as a field flattener essentially correcting the Petzval curvature of the elements of said first and second groups,
- said lens having an optical power of 1.0 and
- 0.85<K.sub.2 <1.20
- -1.4<K.sub.3 <-0.9
- where K.sub.2 and K.sub.3 are the optical powers of said second and third groups, respectively.
A projection lens for a cathode ray tube display consisting of three optical groups, said groups from the image end comprising a first group serving to correct aperture dependent aberrations, said first group having at least one aspheric surface, a second group of strong positive power air spaced from said first group and having biconvex object and image side surfaces, and a third group of negative optical power having an aspheric surface concave to the image end and air spaced from said second group, said third group serving as a field flattener and essentially correcting the Petzval curvature of the elements of said first and second groups, said lens having an optical power of 1.0 and
- 0.85<K.sub.2 <1.20
- -1.4<K.sub.3 <-0.9
- where K.sub.2 and K.sub.3 are the optical powers of said second and third groups, respectively.
A projection lens for a cathode ray tube display consisting of three optical groups, said groups from the image end comprising a first group serving to correct aperture dependent aberrations, said first group consisting of a single element having at least one aspheric surface, a second group of strong positive power air spaced from said first group and a third group of negative optical power having an aspheric surface concave to the image end and air spaced from said second group, said third group serving as a field flattener and essentially correcting the Petzval curvature of the elements of said first and second groups, said lens having an optical power of 1.0 and
- 0.85<K.sub.2 <1.20
- -1.4<K.sub.3 <-0.9
- where K.sub.2 and K.sub.3 are the optical powers of said second and third groups, respectively.
A projection lens for a cathode ray tube display consisting of three optical groups, said groups from the image end comprising a first group serving to correct aperture dependent aberrations, said first group consisting of a single element, a second group of strong positive power air spaced from said first group and having biconvex object and image side surfaces, said second group being of substantially greater optical power than said first group, and a third group of negative optical power having a surface concave to the image end and air spaced from said second group and serving as a field flattener and essentially correcting the Petzval curvature of the elements of said first and second groups, said lens having an optical power of 1.0 and
- 0.85<K.sub.2 <1.20
- -1.4<K.sub.3 <-0.9
- where K.sub.2 and K.sub.3 are the optical powers of said second and third groups, respectively.
Dependencies are inferred from the claim text.