focusing Lens for TO-18

[polishedball]

Could anyone recommend a cheap lens to use on a TO-18 phototransitor? Looking for something perhaps a inch in size? Acrylic would be OK as this will be low power.

Thanks

[LaNeK779]

any sort of cheap magnifying lens held at the right distance maybe?

[mixedgas]

scrap the phototransistor, and get a photodiode. Reverse bias it with about 9 volts. Much faster and less choosy of where the beam hits it.

The simple lens equation (Google it) decides your spot size and lens needed.

Steve