Abstract

We consider the imaging of line structures in confocal imaging systems and show that some advantages result if we employ a slit pupil function in one of the lenses. As an example it is found that the gradient of the image of a straightedge is 17.8% sharper than in a traditional confocal microscope. Another attraction is that theoretical imaging calculations are often possible in terms of simple analytic functions. Experimental results and images are presented which are compared with traditional confocal systems as well as those employing incoherent slit detectors.

© 1990 Optical Society of America

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References

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  1. M. Minsky, “Microscopy Apparatus,” U.S. Patent3,013,467 (1961).
  2. T. Wilson, C. J. R. Sheppard, Theory and Practice of Scanning Optical Microscopy (Academic, London, 1984).
  3. T. Wilson, S. J. Hewlett, “Coherent Detection in Scanning Microscopes,” Inst. Phys. Conf. Ser. 98, 629–632, (1989).
  4. C. J. R. Sheppard, X. Q. Mao, “Confocal Microscopes with Slit Apertures,” J. Mod. Opt. 35, 1169–1185 (1988).
    [CrossRef]
  5. T. Wilson, S. J. Hewlett, “Imaging in Scanning Microsopes with Slit-Shaped Detectors,” J. Microsc. (In Press) (1990).
    [CrossRef] [PubMed]
  6. M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975).
  7. M. Abramowitz, I. A. Stegun, Eds., Handbook of Mathematical Functions (Dover, New York, 1965).
  8. D. Nyyssonen, “Linewidth Measurement with an Optical Microscope: the Effect of Operating Conditions on the Image Profile,” Appl. Opt. 16, 2223–2230 (1977).
    [CrossRef] [PubMed]
  9. T. Wilson, S. J. Hewlett, “The Use of Annular Pupil Plane Filters to Tune the Imaging Properties in Confocal Microsocpy,” J. Mod. Opt. (1990); in press.
    [CrossRef]
  10. T. Wilson, D. K. Hamilton, “Dynamic Focusing in the Confocal Scanning Microscope,” J. Microsc. Part 2 128, 139–143 (1982).

1989

T. Wilson, S. J. Hewlett, “Coherent Detection in Scanning Microscopes,” Inst. Phys. Conf. Ser. 98, 629–632, (1989).

1988

C. J. R. Sheppard, X. Q. Mao, “Confocal Microscopes with Slit Apertures,” J. Mod. Opt. 35, 1169–1185 (1988).
[CrossRef]

1982

T. Wilson, D. K. Hamilton, “Dynamic Focusing in the Confocal Scanning Microscope,” J. Microsc. Part 2 128, 139–143 (1982).

1977

Born, M.

M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975).

Hamilton, D. K.

T. Wilson, D. K. Hamilton, “Dynamic Focusing in the Confocal Scanning Microscope,” J. Microsc. Part 2 128, 139–143 (1982).

Hewlett, S. J.

T. Wilson, S. J. Hewlett, “Coherent Detection in Scanning Microscopes,” Inst. Phys. Conf. Ser. 98, 629–632, (1989).

T. Wilson, S. J. Hewlett, “Imaging in Scanning Microsopes with Slit-Shaped Detectors,” J. Microsc. (In Press) (1990).
[CrossRef] [PubMed]

T. Wilson, S. J. Hewlett, “The Use of Annular Pupil Plane Filters to Tune the Imaging Properties in Confocal Microsocpy,” J. Mod. Opt. (1990); in press.
[CrossRef]

Mao, X. Q.

C. J. R. Sheppard, X. Q. Mao, “Confocal Microscopes with Slit Apertures,” J. Mod. Opt. 35, 1169–1185 (1988).
[CrossRef]

Minsky, M.

M. Minsky, “Microscopy Apparatus,” U.S. Patent3,013,467 (1961).

Nyyssonen, D.

Sheppard, C. J. R.

C. J. R. Sheppard, X. Q. Mao, “Confocal Microscopes with Slit Apertures,” J. Mod. Opt. 35, 1169–1185 (1988).
[CrossRef]

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

Wilson, T.

T. Wilson, S. J. Hewlett, “Coherent Detection in Scanning Microscopes,” Inst. Phys. Conf. Ser. 98, 629–632, (1989).

T. Wilson, D. K. Hamilton, “Dynamic Focusing in the Confocal Scanning Microscope,” J. Microsc. Part 2 128, 139–143 (1982).

T. Wilson, S. J. Hewlett, “The Use of Annular Pupil Plane Filters to Tune the Imaging Properties in Confocal Microsocpy,” J. Mod. Opt. (1990); in press.
[CrossRef]

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

T. Wilson, S. J. Hewlett, “Imaging in Scanning Microsopes with Slit-Shaped Detectors,” J. Microsc. (In Press) (1990).
[CrossRef] [PubMed]

Wolf, E.

M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975).

Appl. Opt.

Inst. Phys. Conf. Ser.

T. Wilson, S. J. Hewlett, “Coherent Detection in Scanning Microscopes,” Inst. Phys. Conf. Ser. 98, 629–632, (1989).

J. Microsc. Part 2

T. Wilson, D. K. Hamilton, “Dynamic Focusing in the Confocal Scanning Microscope,” J. Microsc. Part 2 128, 139–143 (1982).

J. Mod. Opt.

C. J. R. Sheppard, X. Q. Mao, “Confocal Microscopes with Slit Apertures,” J. Mod. Opt. 35, 1169–1185 (1988).
[CrossRef]

Other

T. Wilson, S. J. Hewlett, “Imaging in Scanning Microsopes with Slit-Shaped Detectors,” J. Microsc. (In Press) (1990).
[CrossRef] [PubMed]

M. Born, E. Wolf, Principles of Optics (Pergamon, Oxford, 1975).

M. Abramowitz, I. A. Stegun, Eds., Handbook of Mathematical Functions (Dover, New York, 1965).

T. Wilson, S. J. Hewlett, “The Use of Annular Pupil Plane Filters to Tune the Imaging Properties in Confocal Microsocpy,” J. Mod. Opt. (1990); in press.
[CrossRef]

M. Minsky, “Microscopy Apparatus,” U.S. Patent3,013,467 (1961).

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

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Figures (17)

Fig. 1
Fig. 1

Schematic diagram of the confocal microscope system.

Fig. 2
Fig. 2

Image of a point object plotted as I(t,0) and I(0,ω) in a system employing one circular lens and one slit lens indicating the superior resolution in the direction parallel to the slit.

Fig. 3
Fig. 3

Transfer functions for the traditional confocal, slit lens, and conventional coherent microscope systems.

Fig. 4
Fig. 4

Edge response in a system employing one circular and one slit lens.

Fig. 5
Fig. 5

Edge responses in the traditional confocal and conventional coherent microscope systems.

Fig. 6
Fig. 6

(a) Real part of the coherent transfer function c(m,0) for detail parallel to the slit for various amounts of defocus. (b) Imaginary part of the coherent transfer function c(m,0) for detail parallel to the slit for various amounts of defocus. (c) Real part of the coherent transfer function c(0,n) for detail perpendicular to the slit for various amounts of defocus. (d) Imaginary part of the coherent transfer function c(0,n) for detail perpendicular to the slit for various amounts of defocus.

Fig. 7
Fig. 7

Theoretical Iplane(u) curves for the traditional confocal, slit lens, and slit detector microscope systems.

Fig. 8
Fig. 8

Schematic of the experimental reflection system used.

Fig. 9
Fig. 9

Experimental line scans across a cleaved edge of a GaAs semiconductor in the traditional confocal, slit lens, and conventional coherent microscope systems: (a) traditional confocal: (b) edge perpendicular to the slit lens: (c) edge parallel to the slit lens; (d) conventional coherent.

Fig. 10
Fig. 10

Experimental Iplane(u) curves obtained by scanning a plane mirror axially through focus in the various microscope systems: (a) traditional confocal; (b) slit lens; (c) slit detector.

Fig. 11
Fig. 11

Image of a portion of an experimental power transistor with each microscope system focused on the central, square pad: (a) traditional confocal; (b) slit lens; (c) slit detector.

Fig. 12
Fig. 12

(a) As in Fig. 11(a) but focused 2 μm further out of the specimen. (b) As in Fig. 11(b) but focused 2 μm further out of the specimen. (c) As in Fig. 11(c) but focused 2 μm further out of the specimen.

Fig. 13
Fig. 13

(a) As in Fig. 11(a) but focused 3 μm further out of the specimen. (b) As in Fig. 11(b) but focused 3 μm further out of the specimen. (c) As in Fig. 11(c) but focused 3 μm further out of the specimen.

Fig. 14
Fig. 14

Autofocus image of a portion of an experimental power transistor taken with each microscope system: (a) traditional confocal; (b) slit lens; (c) slit detector.

Fig. 15
Fig. 15

Montage of extended focus image (top left), height image(top right), and isometric projection of a portion of an experimental power transistor taken with each microscope system: (a) traditional confocal; (b) slit lens; (c) slit detector.

Fig. 16
Fig. 16

Cutoff frequency in m ˜,ñ space for a traditional confocal system (circular) and a system employing one full lens and one slit lens (shaded).

Fig. 17
Fig. 17

Cutoff frequency in m ˜,ñ space for a conventional coherent system (circular) and a system employing two perpendicular slit lenses (square).

Tables (1)

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Table I Relative Gradients of Edge Responses

Equations (33)

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I = h 1 h 2 t 2 ,
h ( t , ω ) = - P ( ξ , η ) exp [ - j ( t ξ + ω η ) ] d ξ d η .
t = 2 π λ x sin α ,
ω = 2 π λ y sin α ,
h ( ν ) = 2 J 1 ( ν ) ν ,
h ( t ) = sin t t .
I ( t , ω ) = [ 2 J 1 ( t 2 + ω 2 ) t 2 + ω 2 · sin t t ] 2 .
T ( m , n ) = - t ( x , y ) exp [ - 2 π j ( m x + n y ) ] dmdn ,
I ( x , y ) = | - c ( m , n ) T ( m , n ) exp [ - 2 π j ( m x + n y ) ] dmdn | 2 ,
c ( m , n ) = ( P 1 P 2 ) ( m ˜ , n ˜ ) .
c ( m , 0 ) = 1 - m ˜ 2 ,             0 m ˜ 2 ,
c ( 0 , n ) = 1 - n ˜ 2 ,             0 n ˜ 1 ,
c ( m , 0 ) = 2 π [ cos - 1 ( m ˜ 2 ) - m ˜ 2 1 - ( m ˜ 2 ) 2 ] ,             0 m ˜ 2 ,
c ( 0 , n ) = 1 ,             0 n ˜ 1 ,
I ( s ) = 1 4 [ 1 - 2 π 0 c ( δ ) δ ˜ sin ( δ ˜ s ) d δ ˜ ] 2 ,
I ( t ) = 1 4 { 1 - 2 π [ cos ( 2 t ) - 1 2 t + Si ( 2 t ) ] } 2 ,
I ( ω ) = 1 4 { 1 + J 1 ( ω ) - ω J 0 ( ω ) - π ω 2 [ H 0 ( ω ) J 1 ( ω ) - H 1 ( ω ) J 0 ( ω ) ] } 2 ,
I ( s ) = 1 4 [ 1 - 2 π Si ( s ) ] 2 ,
d I ( s ) d s | s = 0 ~ 0 c ( δ ) d δ ˜ ,
d I ( t ) d t | t = 0 ~ 0 2 ( 1 - m ˜ 2 ) d m ˜ = 1 ,
d I ( ω ) d ω | ω = 0 ~ 0 1 1 - n ˜ 2 d n ˜ = π 4 = 0.785 .
d I ( s ) d s | s = 0 ~ 8 3 π = 0.849 ,
d I ( s ) d s | s = 0 ~ 1.
P ( ξ , η ) P ( ξ , η ) exp [ - 1 2 j u ( ξ 2 + η 2 ) ] ,
u = 8 π λ z sin 2 ( α 2 ) .
c ( u , m , 0 ) = π 2 u exp ( - j u m ˜ 2 4 ) F [ 2 u π ( 1 - m ˜ 2 ) ] , 0 m ˜ 2 ,
c ( u , 0 , n ) = π 2 u exp ( - j u n ˜ 2 2 ) F [ 2 u π ( 1 - n ˜ 2 ) ] , 0 n ˜ 1 ,
F ( z ) = C ( z ) - j S ( z ) = 0 z exp ( - j π 2 x 2 ) d x .
c ( u , δ ) = exp ( - 1 2 j u δ ˜ 2 ) ,             0 δ ˜ 1 ,
I plane ( u ) = c ( u , 0 , 0 ) 2 ,
I plane ( u ) = π 2 u { C 2 ( 2 u π ) + S 2 ( 2 u π ) } ,
I plane ( u ) = [ sin ( u / 2 ) u / 2 ] 2 .
c ( u , m , n ) = exp [ - 1 2 j u ( m ˜ 2 + n ˜ 2 ) ] ,

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