Theoretical Resolution Limit for Optical System Figure 3 Airy Discs Intensity Distributions Theoretical Resolution Limit: is determined by the wavelength of light used for imaging >N2 Wavelength of“ light” Optical microscope(visible light: A=400-600 nm SEM (1-10 kV accelerating voltage): A=1.1 m(11 pm) TEM(100-200 kV accelerating voltage): A=3.6X 10-12 m( 3.6 pm
11 Theoretical Resolution Limit for Optical System • Theoretical Resolution Limit: is determined by the wavelength of light used for imaging → λ/2 • Wavelength of “light”: – Optical microscope (visible light): λ = 400—600 nm – SEM (1—10 kV accelerating voltage): λ = 1.1 × 10-11 m (11 pm) – TEM (100—200 kV accelerating voltage): λ = 3.6 × 10-12 m (3.6 pm)
Aberrations Spherica| Aberration(球差) due to the focus power difference between lens center and edges ··O· 100% Sph Aberation 100% Sph, Aberration -100% sph Aberation 100%Sph Abg% Curv Sph. Aberrant 12
12 Aberrations • Spherical Aberration（球差）: – due to the focus power difference between lens center and edges
Aberrations Chromatic aberration(色差): due to the difference refractive indices for different wavelengths (colors),(recall n=C/M) Axial Chromatic Aberration Blur = 0.30 mm 「 450nm Single Lens 550nm Blur=0.01 mm Doublet 13
13 Aberrations • Chromatic Aberration（色差）: – due to the difference refractive indices for different wavelengths (colors), (recall n = c / λ)
Aberrations Stigmatism Aberration(像散) due to the asymmetry of a lens in the X- and y- directions Astigmatism causes blur along one direction Diffraction 小 Focal Plane Astigmatism Aberration ABCD Vertical lines may be more blurred Tangential Plane Sagittal Optica Diffraction Axis Pattern of Least Confusion o ABCD Sagittal Plane Horizontal lines can be more blurred Objective Object Point Figure 2 Analysis Caustic 14
14 Aberrations • Stigmatism Aberration（像散）: – due to the asymmetry of a lens in the x- and ydirections
Practical resolution Wavelength of"light (recall =h/P) Optical microscope(visible light: A=400-600 nm SEM(1-10 kV accelerating voltage): A=1.1 X10-11 m(11 pm) TEM(100-200 kV accelerating voltage) A=3.6X 10-12 m (3.6 pm) Practical resolution Optical microscope: 300--600 nm SEM(1—10 kV accelerating voltage):λ=2-10nm TEM(100-200 kV accelerating voltage): =0.1-1 nm 15
15 Practical Resolution • Wavelength of “light”: (recall λ = h / P) – Optical microscope (visible light): λ = 400—600 nm – SEM (1—10 kV accelerating voltage): λ = 1.1 × 10-11 m (11 pm) – TEM (100—200 kV accelerating voltage): λ = 3.6 × 10-12 m (3.6 pm) • Practical resolution – Optical microscope: λ = 300—600 nm – SEM (1—10 kV accelerating voltage): λ = 2—10 nm – TEM (100—200 kV accelerating voltage): λ = 0.1—1 nm