SENI
KECANTIKAN & KESEJAHTERAAN
KRAFTANGAN
BUDAYA & SEJARAH
HIBURAN
ALAM SEKITAR
MAKANAN & MINUMAN
KEJURUTERAAN TERBALIK
SAINS
SUKAN
TEKNOLOGI
BOLEH PAKAI
Varifocal Projection Objective
A lantern-slide projector threw one fixed picture size at a given distance; to fill a different screen, the lantern had to be carried closer or further. Clile C. Allen of Chicago put three lenses in one tube, fixed the first and last, and made the middle one slide on a spiral track as the tube was turned - changing the focal length, and so the picture size, from the same spot. A rack and pinion moved the whole tube to refocus.
**US 696,788**, "Optical objective", Allen, filed 25. February 1901, granted 1. April 1902: "three lens elements, the first and third of which are permanently fixed … while the second is movable and capable of being placed in any intermediate position". It is one of the earliest variable-focal-length objectives - the idea behind every zoom lens.
**You build it on a bench as a projector**, and measure picture size against the middle lens's position.
Pertengahan
2 hours
Arahan
1
1
Draw a slide
Draw a slide
Draw a 24 mm square grid with a marker on transparency film. Tape it over the torch lens: this is the lantern.
Bahan untuk langkah ini:
Filem lut sinar pancutan dakwat1 helaian
Pita pelekat kertas1 gulungAlatan diperlukan:
Penanda Kekal
Lampu suluh LED pemeriksaan
Pembaris Keluli2
2
Mount three lenses
Mount three lenses
Wall side: convex ~100 mm. Slide side: convex ~50 mm, 80 mm from the first. Between them: concave ~-50 mm on a holder that slides. Aim the bench at a wall 2 m away with the lit slide behind the 50 mm lens.
Bahan untuk langkah ini:
Set kanta cembung1 set
Kanta cekung1 kepingAlatan diperlukan:
Bangku dan rel optik
Set pemegang kanta3
3
Slide, refocus, measure
Slide, refocus, measure
Set the middle lens 10 mm from the wall-side lens. Move the slide (or the whole lens group) until the grid is sharp on the wall; measure its width. Repeat at 30 and 60 mm.
Alatan diperlukan:
Pita Ukur4
4
Focal length vs position
Focal length vs position
Memuatkan buku nota Jupyter…
5
5
History & Context
History & Context
**What the patent specifies:** a three-element objective with fixed outer elements and a movable middle element carried by a spiral track, plus a rack and pinion to move the whole tube. **Modern build (derived):** stock lenses on an optical bench.
Allen's lens must be refocused after each change - a varifocal. A true zoom keeps focus while zooming by moving two groups together, which came later with cam-driven designs. Its limits: the picture dims as it grows, and aberrations change across the range.
Bahan
4- 1 helaianPemegang Tempat
- 1 gulungPemegang Tempat
- 1 setPemegang Tempat
- 1 kepingPemegang Tempat
Alatan Diperlukan
6- Pemegang Tempat
- Pemegang Tempat
- Pemegang Tempat
- Bangku dan rel optik10% komisenPemegang Tempat
- Set pemegang kanta10% komisenPemegang Tempat
- 1 vendor sell this, none ship to you yetPemegang Tempat
Blueprint berkaitan
Blueprint ini berkongsi pengetahuan — teknik, bahan atau prinsip
CC0 Domain Awam
Blueprint ini dikeluarkan di bawah CC0. Anda bebas menyalin, mengubah, mengedar, dan menggunakan karya ini untuk sebarang tujuan, tanpa meminta kebenaran.
Sokong Pembuat dengan membeli produk melalui Blueprint mereka di mana mereka memperoleh Komisen Pembuat ditetapkan oleh Penjual, atau cipta iterasi baru Blueprint ini dan sertakan ia sebagai sambungan dalam Blueprint anda sendiri untuk berkongsi hasil.