Costco Optical ABO cht 5 Base Curves With
Correct Solutions
what is a Geneva clock - ANSWER tool used to measure base curves
2 outside pins are stationary. middle moves
how would you use a geneva clock? - ANSWER The lens clock has three pointed probes
that make contact with the surface of the lens. The outer two probes are fixed while the
center one moves, retracting as the instrument is pressed down on the lens's surface.
As the probe retracts, the hand on the face of the dial turns by an amount proportional
to the distance
Convex lens is a _____ lens - ANSWER plus
make sure to use the plus measurements on the geneva clock
Concave lens is a ____ lens - ANSWER minus lens
A lens that is thinner in the center than at the edges
make sure to use the minus measuments
if lens is a sepherical base curve and you measure at 180 and 90 they should be the -
ANSWER same
ansi tolerance is ? - ANSWER +- .75d
Correct Solutions
what is a Geneva clock - ANSWER tool used to measure base curves
2 outside pins are stationary. middle moves
how would you use a geneva clock? - ANSWER The lens clock has three pointed probes
that make contact with the surface of the lens. The outer two probes are fixed while the
center one moves, retracting as the instrument is pressed down on the lens's surface.
As the probe retracts, the hand on the face of the dial turns by an amount proportional
to the distance
Convex lens is a _____ lens - ANSWER plus
make sure to use the plus measurements on the geneva clock
Concave lens is a ____ lens - ANSWER minus lens
A lens that is thinner in the center than at the edges
make sure to use the minus measuments
if lens is a sepherical base curve and you measure at 180 and 90 they should be the -
ANSWER same
ansi tolerance is ? - ANSWER +- .75d
