Using SMART - Help

clanmurderUrban and Civil

Nov 15, 2013 (3 years and 8 months ago)

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Using SMART

A quick guide to using the SMART (
S
canning
M
icroscopy
A
nalysis and
R
esolution
T
esting) Macro in
conjunction with SCION Image or NIH Image to
measure SEM resolution, imaging performance and
drift
.

Problems, questions, suggestions for improvements ?
-

please let me know ……... djoy@utk.edu

Version 6.0 gamma

What does SMART do?


SMART currently provides three options


(1) Manual and Automatic Fourier analysis
resolution testing


(2) An alternative Autocorrelation mode to
measure image resolution


(3) A superposition diffractogram mode for
precision resolution measurement including time
dependent drift and instabilities



An implementation of the Frank and Al Ali
algorithm to measure signal to noise ratios

and please note...


Although the MACRO language of IMAGE is good
there are some things I could not make it do. If
you can help improve the interface and usability
of SMART please let me know how.


This is a work in progress so check back on our
website for periodic improvements


The code is copyright 2001 to the author. Feel
free to use it and modify it as you wish. If you
use it in a publication a citation or an
acknowledgement would be welcome


Go forth and magnify…….

Setting up SCION or NIH Image


Before using SMART you must
set up SCION or NIH Image


Go to the Options menu and
click on Preferences


Edit the “Undo &Clipboard
Buffer Size” to
at least 2000k
,
ideally 4000k, then click OK.
Unless this is done
this macro
may not work properly

and
may even fail completely


Go to File and Exit the Image
program. This saves the
preference setting to disc


Then restart Image

Loading SMART


Go to the Special menu and
click on “Load Macros”


Navigate your way to the
folder where you stored
SMART and click Open in the
dialog box


HINT

-

it is a good idea to
store SMART in the MACRO
folder of Image


HINT
-
all output data
appears in the INFO box. It
is also a good idea to try and
position this box some
where it is always visible.


Ready to go


If you click on the
Special menu item
again then the drop
down menu will now
show the new options
that are offered by the
SMART macro


Clicking on any of
these new entries in
the menu will start
that function

Automeasure resolution


Step1

-

Load the micro
-
graph you wish to analyze
(using the File menu).
Note
NIH and SCION image can use
almost any standard image
file format. The number of
pixels in the image is not
important.


Go to the SPECIAL menu
and select an ROI (128 up
to 512). Position the ROI
by clicking and dragging.

Automeasure Resolution


Go to SPECIAL menu and
click the first option
-

AutoMeasure Resolution.


A dialog box appears and
asks for the width of
image
-

this is is width of
the field of view of the
entire image in microns.
Calculate or measure this
value from the micron
marker


Enter the data and click OK


Total image width (microns)

Calculate width from the scale marker

The FFT display


After some processing the
screen now shows the FFT


Hint

-

if the dialog box
covers the FFT drag it out
of the way, but don’t click
OK until you are ready


The program has
attempted to separate the
signal from the noise. In
many cases the guess that
is made is good but you
can adjust the result to
your own needs...

The threshold toolbar


Click on the Threshold tool


Then put the cursor in the
LUT window and drag the
cursor up and down to
change the threshold level


Too low a value of the
threshold will reveal the
noise in the background,
too high a value may cut
off some of the signal and
give a pessimistic result


When satisfied click OK

Threshold tool

LUT window


Threshold too low

Resolution result


The info box now shows the
computed resolution (in nm)
determined from the average
of the length of the major
and minor axes of the ellipse
fitted to the FFT.


The eccentricity of the FFT is
a measure of the stigmatic
error in the beam. Ideally the
value should be zero
-

anything less than about 0.1
is evidence of good
astigmatism.

Manual Resolution Mode


A manual mode is also
provided.


The initial steps in this are
identical with the automatic
mode


Instead of relying on fitting
an ellipse to the signal region
calibrated rings are
superimposed on the power
transform so the user can
visually determine resolution


In cases where the signal
transform is not circular this
is more accurate

0.35nm resolution

Mode 2
-

Autocorrelation


This mode does an auto
-
correlation of the FFT of
the image to determine the
information cut
-
off. No
user intervention is needed


Load the image then go to
the Special menu and
select your ROI


When the ROI is set then
go to the Special menu
again and select the
AutoCorrelation mode


Autocorrelation
-

step 2


After you answer the
question about the image
width the program will
display the 2
-
D Auto
-
Correlation plot as shown


The macro measures the
width of the correlation
peak at 20% of maximum


This width gives the
spatial
resolution

of the image at
the information cut
-
off
limit.

Line profile across correlation

Mode 3
-

Two Image Analysis


This part of SMART uses
two images to give an
accurate measure of
resolution and drift


The two images should be
recorded one directly after
the other. Do not adjust
the stage, focus, gun etc..


Load the two images then
go to the SPECIAL menu
select and position the ROI
on the top image.
The ROI
must be smaller than the
image size

Image 1

Image 2


Mode 3
-

step 2


After you calibrate the
image size as usual the
Macro copies the image in
the ROI from image 1,
puts the same ROI on
image 2 but shifted
horizontally by 16 pixels,
copies that image area,
then forms a composite
image from these two
fragments. The 2
-
D power
spectrum is then
calculated and displayed

2
-
D power spectrum from
composite image

Resolution analysis


Only
detail

present on a pixel
by pixel basis in both images
appears modulated by the
fringes in the FFT. Noise is
unmodulated and so is
readily distinguished from
image detail


Calibrated rings are
superimposed over the
fringed FFT so that the
resolution can be visually
determined


Here fringes can be seen
extending to below 2.5 nm

Measuring Drift


The fringes should be
vertical because the
images are offset
horizontally by 16 pixels


If drift or instability
occurs the fringes will
rotate through some angle
q
. The actual drift direction
is then in the indicated
direction.

q

fringes

90
-
q/2

Drift
vector

Note that…….


The resolution result given by this mode averages over the
time interval required to record both images and so is a
good test of real world resolution.


This routine has failed to work on some computers,
apparently because of screen driver problems with the
SWITCH command. If the macro fails to work for you, load
both images as usual, position the ROI on image 1, then
manually put the ROI in position on image 2 as well, then
run the Two Image routine.


On small monitor screens, or when using big images, the
INFO box may sometimes be hidden. Try and move it to a
convenient corner of the screen before starting an analysis.

S/N ratio measurement


To use this mode, load the
image of choice then select
S/N mode. The Frank and Al
Ali algorithm is used on
alternate line pairs of data


The computation takes a few
seconds so please be patient


The result appears in the
Info

box


This works best when the
detail in an image is large
compared to the pixel size
(i.e. images with empty
magnification)