The Atzema spiral, also known as the Pritch-Atzema spiral, is the curve whose catacaustic for a radiant point at the origin is a circle, as illustrated above.
It has parametric equations
 |  |  |
(1)
|
 |  |  |
(2)
|
where 
,
which generates a circle of radius 
.
The sequence of rays generating the circle catacaustic as 
is varied from 
to 
is shown above.
