Abstract

A differential amplitude scanning system for ophthalmoscopy is described theoretically. The differential scanning ophthalmoscope (DSO) samples the retina with two laterally displaced spots. The signal measured is the difference between the irradiance from these two locations. The theoretical analysis of the DSO shows it offers increased contrast at high spatial frequencies and only weak contributions from the low frequencies. This enables high-gain, low-noise detection that maximizes contrast.

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References

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  1. C. W. See and M. Vaez-Iravani, Appl. Opt. 27, 2786 (1988).
    [CrossRef] [PubMed]
  2. T.Wilson, ed., Confocal Microscopy (Academic, 1990).
  3. R. H. Webb, G. W. Hughes, and F. C. Delori, Appl. Opt. 26, 1492 (1987).
    [CrossRef] [PubMed]
  4. R. N. Bracewell, The Fourier Transform and its Applications, 3rd ed. (McGraw-Hill, 2000).
  5. T.Wilson and C.Sheppard, eds., Theory and Practice of Scanning Optical Microscopy (Academic, 1984).

1988

1987

Appl. Opt.

Other

R. N. Bracewell, The Fourier Transform and its Applications, 3rd ed. (McGraw-Hill, 2000).

T.Wilson and C.Sheppard, eds., Theory and Practice of Scanning Optical Microscopy (Academic, 1984).

T.Wilson, ed., Confocal Microscopy (Academic, 1990).

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Figures (4)

Fig. 1
Fig. 1

Magnitude of the general transfer function C SLO ( m ; p ) for the standard confocal microscope (SLO). Top, amplitude plot (normalized); bottom, contour plot with the outermost square contour showing the frequency cutoff, and the thicker contour representing the 0.5 level. m and p axes in units of v (see text).

Fig. 2
Fig. 2

Magnitude of the general transfer function C DSO ( m ; p ) for the differential system (DSO). Plots and axes as in Fig. 1. The plots show that the DSO has no dc term and weak low- frequency contributions. Although the cutoff is the same as the SLO, higher frequencies contribute more in the DSO.

Fig. 3
Fig. 3

Pixel values along a horizontal line of an SLO image and their numerical derivative.

Fig. 4
Fig. 4

Plots of parameters S, L, and G against a.

Equations (11)

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I DSO ( x , y ) = | h e , 1 r | 2 | h e , 2 r | 2 ,
h e , 1 ( x , y ) = h e , 2 ( x a , y )
I DSO ( x , y ) = | F 1 { H e , 1 R } | 2 | F 1 { H e , 2 R } | 2 .
I DSO ( x , y ) = H e , 1 ( m , n ) H e , 1 * ( p , q ) R ( m , n ) × R * ( p , q ) exp { i 2 π [ ( m p ) x ( n q ) y ] } × d m d n d p d q H e , 2 ( m , n ) H e , 2 * ( p , q ) × R ( m , n ) R * ( p , q ) exp { i 2 π [ ( m p ) × x ( n q ) y ] } d m d n d p d q ,
H e , 2 ( m , n ) = exp ( i 2 π a m ) H e , 1 ( m , n ) ,
H e , 2 * ( p , q ) = exp ( i 2 π a p ) H e , 1 * ( p , q ) .
I DSO ( x , y ) = { 1 exp [ i 2 π a ( m p ) ] } × H e , 1 ( m , n ) H e , 1 * ( p , q ) R ( m , n ) R * ( p , q ) × exp { i 2 π [ ( m p ) x ( n q ) y ] } d m d n d p d q .
C DSO ( m , n ; p , q ) = { 1 exp [ i 2 π a ( m p ) ] } H e , 1 ( m , n ) H e , 1 * ( p , q ) ,
C DSO ( m , n ; p , q ) = i 2 π a ( m p ) H e , 1 ( m , n ) H e , 1 * ( p , q ) .
C SLO ( m , n ; p , q ) = H e , 1 ( m , n ) H e , 1 * ( p , q ) .
I 0 ( v ) = | h 1 2 ( v ) | 2 | h 2 2 ( v ) | 2 ,

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