RF SN - Spectral SNR of images ||

PURPOSE

Compute the Spectral Signal-to-Noise Ratio (SSNR) of a series of images.

SEE ALSO

RF	[Phase Residual & Fourier ring correlation, 2D ||]
RF 3	[Phase Residual & Fourier shell correlation, 3D ||]
BL	[Create Blank image]

USAGE

.OPERATION: RF SN

.INPUT FILE NAME OR TEMPLATE (E.G. STK@****): IMG***

If file name has '*' the following question appears:

.ENTER FILE NUMBERS OR SELECTION DOC. FILE NAME: 1-700
[Enter file numbers or the name of a document file containing file numbers in the first register column.]

.MASK FILE: MAS999
[Enter the name of mask image used to mask each input image in the set. If you do not want to mask the images, you will have to create a mask image with constant intnsity = 1 using operation 'BL'.]

.RING WIDTH: 0.5
[Enter ring width of each frequency radius for SSNR computation.]

.OUTPUT DOCUMENT FILE: DOC001
[Enter name for resulting document file.]

NOTES

1. Operation calculates the following equations:
   
   FR(I): Sum over Fourier units in each ring of radius I
   FR(I) = N*{SUM(SIG(kX,kY)) / SUM[NOI(kX,kY)/(N-1)]}
   
   SSNR:
   SSNR(I) = FR(I)-1 if FR(I) > 1
   SSNR(I) = 0 if FR(I) <= 1
   
   VAR(I) is the expected variance of SSNR(I):
   VAR(I) = SQRT{2[(N2+N1-2) * (1+2*SSNR(I))+N1*SSNR(I)**2)] / [N1*(N2-4)]}
      --- N1 = NRING(I)/2
      --- N2 = N1*(N-1)
      --- NRING = Number of Fourier units for each ring.
   

2. Document file contents:
   

   KEY = RING RADIUS

   RING RADIUS (NORMALIZED SCALE)

   SSNR(I)

   NRING(I)

   VAR(I)

3. References:
   [1] M. Unser, B.L. Trus & A.C. Steven, Ultramicroscopy 23(1987) 39-52: "A New Resolution Criterion Based on Spectral Signal to-Noise Ratios"
   
   [2] M. Unser, B.L.Trus & A.C. Steven, Ultramicroscopy 30(1989) 429-434: "The Spectral Signal-to-Noise Ratio Resolution Criterion: Computational Efficiency and Statistical Precision"

SUBROUTINES

SSNRB

CALLER

FOUR1