title: How to use a Hamming window in the frequency domain?
body: <p>In "Principles of computerized tomographic imaging" by Kak &amp; Slaney it is written that superior reconstructions are obtained by multiplying the transform of the image projections: </p>
  
  <pre><code>S(m * 2W/N) 
  </code></pre>
  
  <p>( where N is the number of the samples, m is the index of the   samples: m=-N/2,...,0,...,N/2  and 1/(2W) is the sampling interval in the spacial domain ) </p>
  
  <p>by a Hamming window: H(m*2W/N).</p>
  
  <p>But the analytic expression of the Hamming window is not written there. </p>
  
  <p>I saw in matlab documentation that the expression of a Hamming window is :</p>
  
  <pre><code>w(n)=0.54-0.46*cos(2*pi*n/N)   for  0&lt;=n&lt;=N
  </code></pre>
  
  <p>But is this in the spacial domain or in the frequency domain (in the later case should I fft this expression before multiplying it with the transform of the image projections)?</p>
  
  <p>In "The measurement of power spectra" by Blackman &amp; Tukey the Hamming window is given by:</p>
  
  <pre><code>D(tau)=0.54+0.46*cos(pi*tau/T)  for abs(tau)&lt;T
  </code></pre>
  
  <p>This is given in the special domain.</p>
  
  <p>The bottom line is that I do not know what expression should I use for the Hamming window:</p>
  
  <pre><code> H(m*2W/N) 
  </code></pre>
  
  <p>That is needed to be multiplied by the fourier transform of the image projection: </p>
  
  <pre><code>S(m * 2W/N).
  </code></pre>
  
  <p>Can someone help me please ?</p>