Fundamentals of Digital Image Processing - Control of Color Imaging Systems: Analysis and Design - page 90

FIGURE 2.63 (See color insert following page 428.) Halftone LENA image.

PROBLEMS
2.1 Consider a digital camera with a focal length of 50 mm, an f number of 5.6,
and a CCD sensor pixel dimension of 16 . Consider two objects

at distances of 1 and 3 m from the camera, respectively. We wish to take a
picture of these two objects and keep both of them in focus as much as
possible.
a. Find the distance at which the camera should be focused so that the PSF
resulting from the defocus of both of these objects have the same radius. Is
this distance halfway in between the two objects?
b. Find the radius of blur in terms of the number of pixels of the CCD sensor
for the above set of parameters.
c. Repeat part (b) for an f number of 2 and an f number of 16.

mm 16 mm

2.2 Consider an out-of-focus camera with a blur radius of R. Assume that the
object moves horizontally with uniform motion during the exposure period
such that the resulting PSF on the

film has a width of a. Find the horizontal

pro le of the resulting cascaded PSF for a given vertical distance of y on

the film.

2.3 Find the DFT of the checkerboard image de ned by

n þ m

n, m ¼

...

, N

f ( n, m ) ¼ 0 : 5 þ 0 : 5 ( 1 ) 0, 1, 1

2.4 A circularly symmetric imaging system has a PSF given by

h ( r ) ¼ e j r j

a. Derive an expression for the OTF and MTF of this imaging system.
b. At what spatial radial frequency does the system MTF fall to

p ?

1