LS, 
on 
1) 
(2) 
3S 
le 
Figure 1 illustrates the mechanical, optical and elec- 
tronic schemes of the measurement equipment: 
Via a well-corrected collimator lens (f = 2340 mm) and 
the test piece an incoherently illuminated object slit 
is depicted in the image plane of the test piece. A 
microlens (32x/0.65/00/0) projects the slit image formed 
there on to the fixed analyzer slit, behind which a 
secondary electron multiplier is located for recording 
the slit-spread function. 
The slit-spread function is measured by slow, linear 
movement of the object slit led by a moving coil system. 
That way, the slit image moves over the analyzer slit 
and is scanned. 
On the object side the space coordinate of the slit- 
spread function is measured with an inductive precision 
indicator. 
Associated intensity and spatial values are digitized 
simultaneously and subsequently fed into the computer 
which with the aid of a clock generator ensures a 
temporally equidistant interrogation of the measured 
data pairs. After measurement has been performed, MTF 
is calculated according to equation (2). Measuring accu- 
racy AM — 0.015 with spatial frequencies decisive for 
the image. 
For adjusting and focussing processes the object slit 
can be set into vibration so that the slit-spread func- 
tion can be represented on an oscilloscope, which, for 
instance, renders possible focussing on to the maximum 
peak value of the slit-spread function. 
For measuring the off-axis MTF curves test piece (lens) 
holder whose construction resembles that of the camera 
and y'-displacement are rotated about the vertical axis 
running through the centre of the entrance pupil, and the 
image analyzer is set to the corresponding image height. 
The radial and tangential positions of the object slit 
are realized by an image rotation system. 
With the equipment described MTF was measured on the 
"Pinatar 4/125" lenses for the MKF-6 Multispectral Can- 
era and on the aerial camera lens "Lamegon PI 4.5/450".