Short focal length Petzval-type optical system

An optical system of relatively short focal length and large aperture having substantially the following specification:

• EFL = 7.38mm 1/2 Angle of Field = 2.58.degree. LENS RADII (IN.) THICKNESS (IN.) SPACING (IN.) ______________________________________ L.sub.1 R.sub.1 = .8013 D.sub.1 = .0890 R.sub.2 = 1.7049 S.sub.1 = .0163 L.sub.2 R.sub.3 = - .4552 D.sub.2 = .0400 R.sub.4 = .8970 S.sub.2 = .3381 L.sub.3 R.sub.5 = .5318 D.sub.3 = .0852 R.sub.6 = 1.4273 S.sub.3 = .0050 L.sub.4 R.sub.7 = .1864 D.sub.4 = .0861 R.sub.8 = - .2589 S.sub.4 = .1320 BFL ALL ELEMENTS:
• V = 25.8, N.sub.D = 1.785 ______________________________________
• wherein the first column lists the lens elements numerically starting at the ray entrance side of the system which elements each have the same dispersive index and refractive index;
• the second column lists the respective base radii R.sub.1 to R.sub.8 ;
• the third column lists the thickness D.sub.1 to D.sub.4 of the respective elements;
• and the fourth column lists the axial spacings S.sub.1 to S.sub.4 between the respective elements, and the image plane.