What are ball lenses and what are they used for?

[0207]

any idea what these ball lenses are.. ? any specific application?

 

[negitron]

http://www.edmundoptics.com/TechSupport/DisplayArticle.cfm?Articleid=245

 

[Andy Resnick]

Ball lenses are commonly used to couple light into a fiber, but they can be used in other applications. An interesting one is a weather recorder-

http://en.wikipedia.org/wiki/Campbell-Stokes_recorder