A compensator ( null-corrector ) for testing aspheric optical surfaces is proposed , which enables i ) independent verification of optical elements and assembling of the compensator itself , and ii ) ascertaining the compensator position in a control layout for a specified aspheric surface .
The compensator consists of three spherical lenses made of the same glass .
In this paper , the scope of the compensator expanded to a surface speed \sim f / 2.3 ; a conceptual example for a nominal primary of Hubble Space Telescope is given .
The autocollimating design allows significant reducing difficulties associated with practical use of lens compensators .