1S. 
@ 
Optical arrangement to obtain a line spread function is 
illustrated in Figure 1. A slit illuminated by light source and 
optical fiber assembly is projected by the lens under test through 
a variable light bender Which locates the projected slit image on 
a scanner when one changes image height and also through collimator 
lens which makes line images on the scanner. The herical scanning 
slit is rotated by a synchronous motor and spatial distribution 
of the line spread function is converted to a periodic time signal. 
This signal is put into a mini-computer through an interface 
and the Fourier transformation shown by Eq(4) is processed digitally. 
Figure 2 shows the processor and teletype. The processor has a display 
capability for line spread function and MTFs on CRT and also for 
X-Y recorder as shown in Figure 3. 
Typical X-Y recorder outputs are shown in Figure 4. 
4. MEASUREMENT 
4.1 Parameters for Measurement 
Since photogrammetric cameras are usually used for infinite 
conjugate, MTF measurements must be done at a fixed focus plane 
one which film should be located. Therefore, the following procedures 
are needed to achieve the above conditions. 
4.1.1 Image Plane 
Slits are made on a flat glass surface of which flatness is 
kept within Spm. This surface is put in contact with the mechanical 
surface of a camera as a replacement for the pressure plate. The scanner 
is placed exactly at the focus of the collimator lens. 
4.1.2 “Light Quantity 
We are measuring MTF for white light in a combination of 
a halogen lamp of 3300?K and a photomultiplier (R372) instead of 
for monochromatic light. 
Choice of suitable light quality has to be considered in 
the future to take into account many different conditions such as 
atmospheric spectral transmission, average spectal reflectance of 
earth surface etc. : 
4.1.3 Image Height (H) 
Since optical systems have rotational symmetry, imaging 
performances have the same symmetric characteristics. Locations of 
measured points on a film plane are expressed by distances from 
the center of the film and are called image height.