Display 2D Spectrum

Use the 2D Filtering > Display 2D Spectrum option (FFT2PSPC GX) to calculate the power spectrum of an FFT2 Transform image.

Display 2D Spectrum dialog options

Input transform grid

Select the name of the input transform file.

Script Parameter: FFT2PSPC.TRN

Output 2D spectrum grid

Specify the name of the output power spectrum file.

Script Parameter: FFT2PSPC.SPC

Application Notes

NX= original X dimension

NY= original Y dimension

DX= X element separation

DY= Y element separation

WX= 1/(NX*DX), wavenumber increment in X

WY= 1/(NY*DY), wavenumber increment in Y

QX= 1/(2*DX) , Nyquist in X

QY= 1/(2*DY) , Nyquist in Y

0 +WX +QX  

r i r i r i  

v NY-1 . . . . . . . . . . -WY  

e . . . . . . . . . . -WY*2  

c . . . . . . . . . .  

t . . . . . . . . . .  

o . . . . . . . . . .  

r . . . . . . . . . .  

. . . . . . . . . . -(QY-WY)  

^ . . . . . . . . . . QY  

| . . . . . . . . . . QY-WY  

. . . . . . . . . .  

. . . . . . . . . .  

. . . . . . . . . .  

. . . . . . . . . .  

2 . . . . . . . . . . WY*2  

1 . . . . . . . . . . WY  

0 . . . . . . . . . . 0  

0 1 2 (NX+1) -> element  

(The X(-)Y(+) portion will be complex conjugate of the X(+)Y(-) portion)

(The X(-)Y(-) portion will be complex conjugate of the X(+)Y(+) portion)

The power spectrum storage in file .SPC will be:

(The power spectrum is (r*r+i*i))

 

0 +WX +QX  

NY-1 . . . . . QY  

. . . . . QY-WY  

. . . . .  

. . . . .  

. . . . .  

. . . . .  

. . . . . WY*2  

. . . . . WY  

. . . . . 0  

. . . . . -WY  

. . . . . -WY*2  

. . . . .  

. . . . .  

2 . . . . .  

1 . . . . .  

0 . . . . . -(QY-WY)  

 

0 NX/2  

(The X(-)Y(+) portion will be the same as the X(+)Y(-) portion)

(The X(-)Y(-) portion will be the same as the X(+)Y(+) portion)

See Also: