Measuring MTF
PixelScope's MTF wizard computes the Modulation
Transfer Function of a lens with a few mouse clicks.
The calculation is based on the profile of an
edge in the image. The MTF wizard performs the
calculation automatically and displays the results
in real time.
Preliminary setup
Use the PixelScope's Hardware dialog to enter
these values.
- Collimator focal length
- Filter
- F-number
- Nominal focal length
- Microscope calibration value
The Optical Layout window provides
a concise graphic summary of the values you have
entered:
 The
astute reader may question why so many values
are required. After all, the MTF calculation does
not require all this information--the focal length
of the collimator and lens under test are not
actually needed. Nevertheless, we suggest entering
the correct values anyway. If you do this the
Optical Layout window provides concise documentation
of the setup.
Pick a target
The MTF wizard operates on a section of the image
with a sharp, well defined edge. The photo below
shows a suitable edge.
Note that the intensity has
reached a stable value at both ends of the selection
area. However the selection below is not satisfactory.
Do you see why?
At the left edge of the selection
rectangle the blue intensity line has not returned
to the background value of zero. Dragging a wider
selection rectangle would not help either--the
neighboring feature is too close.
Operator
care is required when using a crowded target like
USAF.
Making the actual measurement
Drag a selection rectangle around the target
The MTF is automatically computed
and displayed:
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