ABSTRACT
To reduce the f-number, the front element is often split into two positive lenses. Another modification involves the splitting of the rear element into a cemented negative–positive lens. The Tessar lens is a modification in which both front and rear elements are split into cemented negative–positive assemblies. The Heliar lens is still another modification and is shown in Figure 4.1; details are given in Table 4.1. The lens in the figure is f/5 with a 20° field of view (FOV), and has a focal length of 10. Visual region. Figure 4.2 shows a 4-inch focal length,f/4.5 Tessar lens. It covers an image field of 3.0 in diameter; details are given in Table 4.2. A Heliar <italic>f</italic>/5 les. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315222295/bd2ad0d9-a48e-40ac-8986-c51474069cbd/content/fig4_1.tif"/> A Tessar lens, 4-in., <italic>f</italic>/4.5. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315222295/bd2ad0d9-a48e-40ac-8986-c51474069cbd/content/fig4_2.tif"/> Heliar Lens, <italic>f</italic>/5
Surface
Radius
Thickness
Material
Diameter
1
4.2103
0.9004
N-SK16
2.860
2
−3.6208
0.2999
N-LLF6
2.860
3
29.1869
0.7587
2.320
4
−3.1715
0.2000
N-LLF6
1.780
5
3.2083
0.1264
1.660
6
Stop
0.2629
1.555
7
43.0710
0.2500
N-LLF6
2.240
8
2.4494
0.8308
N-SK16
2.240
9
−3.2576
8.5066
2.240
Distance of front lens surface to image = 12.136, distortion = 0.12%. An <italic>f</italic>/4.5 Tessar LensSurface
Radius
Thickness
Material
Diameter
1
1.3329
0.2791
N-SK15
1.400
2
−9.9754
0.2054
1.400
3
−2.0917
0.0900
F2
0.940
4
1.2123
0.0709
0.820
5
Stop
0.1534
0.715
6
−7.5205
0.0900
K10
1.260
7
1.3010
0.3389
N-SK15
1.260
8
−1.5218
3.4025
1.260
Distance of first lens surface to image = 4.630, distortion = 0.34%.