Differential Interference Contrast Microscopy (DIC) - Biomedical Optical Phase Microscopy and Nanoscopy - page 24

Table 2.1: Measured Shear Angles, Computed Shear Distances, and Ratios of Shear Distance to
Airy Disk Radius for Various Combinations of Olympus DIC Prisms and Objective Lenses at
Wavelength 532 nm

DIC Prism
Type

Shear
Angle,

Shear Distance, d in µ m (Ratio d/r Airy )

ε

UplanFl
10

UplanFl
20

UplanSApo
30

UplanFl
40

UplanSApo
60

UplanSApo
60

UplanFl
100 /0.30 /0.50 /1.05

Sil

/0.75 /

1.20 W

/1.30
Sil

/1.30
Oil

3 3 3 3 3 3 3

U-DICTHR 40 μrad 0.72 (0.67) 0.36 (0.55) 0.24 (0.78) 0.18 (0.42) 0.12 (0.44) 0.12 (0.48) 0.072 (0.29)

U-DICT 74 μrad 1.32 (1.23) 0.67 (1.03) 0.44 (1.44) 0.33 (0.77) 0.22 (0.82) 0.22 (0.89) 0.13 (0.53)

U-DICTHC 143 μrad 2.57 (2.38) 1.29 (1.98) 0.86 (2.78) 0.64 (1.49) 0.43 (1.59) 0.43 (1.72) 0.25 (1.03)

mechanical components were purchased from Thorlabs (Newton, NJ, USA, http://www.
thorlabs.com ) .

Table 2.1 summarizes representative results of the shear angle measurements of various
DIC prisms currently manufactured by Olympus (Tokyo, Japan, http://www.olympus.com ).
The high-resolution DIC prism U-DICTHR has the smallest shear angle. The prism enables
observations with high resolution but with less glare even for thick specimens used in
developmental and genetic research, such as finely structured diatoms, embryos, zebrafish
and Caenorhabditis elegans. The general-use prism U-DICT with the intermediate shear
angle is suitable for observing a wide range of general specimens, such as tissue. The
high-contrast DIC prism U-DICTHC has the largest shear angle. Using this prism, high
contrast can be obtained even in high-magnification observations of thin specimens, such
as culture cells.

Table 2.1 shows also the corresponding computed shear distance d in the object plane and
ratio of the shear distance to the Airy disk radius d/r Airy . For the calculation, standardized
reference focal lengths of the tube lenses L t are used for infinity-focused objective lens,
which are adopted by several microscope manufacturers.

L t
M

d 5 ε (2.11)

In Eq. (2.11) , M is the objective lens magnification. In particular, the reference focal length
L t is 180 mm for Olympus, 164.5 mm for Zeiss, and 200 mm for Nikon and Leica
microscopes [9] .

The radius of Airy disk r Airy is determined by the following equation [9] :

r Airy 5 0 : 61 NA (2.12)

where NA is the objective lens numerical aperture.