艺术
美容与健康
工艺
文化与历史
娱乐
环境
食品与饮料
逆向工程
科学
体育
技术
可穿戴设备
Cooke Triplet Lens
Nineteenth-century lens makers flattened the image with a stop placed in front of or behind the lens, at the cost of astigmatism at the edges. Harold Dennis Taylor, optical manager at T. Cooke & Sons of York, dropped that trick entirely. He showed that a negative lens images a flat object onto a surface curved exactly as much as a positive lens of equal power, but the other way - so one can cancel the other.
**US 540,122**, "Lens", Taylor, filed 5. February 1894, granted 28. May 1895, puts "a negative lens … between two positive lenses, the focal power of the negative lens being approximately equal to the combined focal powers of the two positive lenses". Three separated elements: the Cooke triplet, still the simplest well-corrected camera lens.
**You build one from stock lenses**, and compare how flat its image is with a single lens.
中级
2 hours
说明
1
1
Choose three lenses
Choose three lenses
Two convex lenses of about 100 mm focal length (check each on a distant window) and one concave of about -50 mm. Powers: +10 and +10 dioptres against -20.
此步骤所需材料：
凸透镜套装1 套
凹透镜1 个所需工具：
钢直尺2
2
Mount the triplet
Mount the triplet
On the bench: convex, 20 mm gap, concave, 20 mm gap, convex. Centre all three on the same height.
所需工具：
光学导轨与滑轨
透镜支架套装3
3
Light a grid
Light a grid
Tape graph paper to a window or light it from behind with a torch, 1.5 m from the lens. Put a tracing-paper screen behind the triplet and focus the centre of the grid sharply.
此步骤所需材料：
坐标纸1 张
裁剪拓样纸卷1 张
美纹纸胶带1 卷所需工具：
LED 检查手电
卷尺4
4
Measure the edge refocus
Measure the edge refocus
Without touching the lenses, move the screen until the grid 15 mm from the image centre is sharpest. Note how far it moved. Replace the triplet with one convex lens, refocus the centre, and measure the refocus again at the same 15 mm image height.
所需工具：
钢直尺5
5
Petzval sum and design
Petzval sum and design
正在加载 Jupyter 笔记本…
6
6
History & Context
History & Context
**What the patent specifies:** a negative lens between two positive lenses, its power about equal to theirs combined, each element free of diaphragm corrections, flattening the field and removing marginal astigmatism. **Modern build (derived):** three stock singlets on a bench.
Taylor's employer declined to make it; Taylor, Taylor & Hobson did, as the Cooke lens. Tessar and many later designs grew from it. Its limits: with only three elements the aperture and angle of view are modest before aberrations return.
CC0 公共领域
此蓝图以 CC0 协议发布。你可以自由复制、修改、分发和使用此作品，无需征得许可。
通过购买蓝图中的产品支持创客，他们将获得 创客佣金 （由供应商设定），或创建此蓝图的新版本并将其作为连接包含在你自己的蓝图中以分享收入。