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RF SN - Spectral SNR of images

(8/25/97)

PURPOSE

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

SEE ALSO

RF [R Factor]
RF 3 [Phase residual in 3D]

USAGE

.OPERATION: RF SN

.ENTER TEMPLATE FOR IMAGE NAME: IMG***

.Selection doc file: SELECT
[Enter selection document file name containing the numbers of the input images in the first column.]

.MASK FILE: MAS999
[Enter the name of mask image for masking each image in the set]

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

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

FR(I) = N*{SUM(SIG(kX,kY))/SUM[NOI(kX,kY)/(N-1)]}
Sum over Fourier units in each ring of radius I

NOTES

  1. If you do not want to mask the images, you still have to create a mask image with constant value 1 by using command 'BL'.

  2. Command calculates the following equations:
    SSNR: SSNR(I) = FR(I)-1 if FR(I).GT.1
    = 0 if FR(I).LE.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.
    DOC file: COLUMN: #1 #2 #3 #4 #5
    RING RADIUS RING RADIUS SSNR(I) NRING(I) VAR(I)
    (NORMALIZED SCALE)

  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

SSNR, SSNRB

CALLER

FOUR1

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