On 27/08/2019 21:51, Harry Bloomfield wrote:
dennis@home wrote on 27/08/2019 :
IIRC they showed something similar on tomorrows world a long time ago.

I remember those!


They have also been suggested for third world countries too, using
cheap syringes for the fluid.

Do these use a liquid lens?


No, they have two rather complex lenses that slide over each other. The
final picture on the website shows how they work. Quite clever, but I'd
have thought there's a lot of distortion.