MicroscopyEducation
Table 1: Specifications of lenses used for comparison of the L-eye mobile and ECLIPSE E100 microscopes. Magnification
Focal length (mm)
CFIBE Plan (Nikon) Compound lense 1.5 mm ball lens (Edmund)
20 5
2.9 1.1
100× (x10b 400× (x40b
) )
180× (x1.03c 500× (x2.73d
) )
NA (numerical aperture)
0.25 0.65
0.25 0.4
Theoretical resolutiona
1.44 0.6
1.44 0.9
(μm)
Working distance (mm)
6.7 0.6
3.8 0.23
a: 0.61λ/NA (λ=589.6 nm (NaD line)). b: Maker’s specification for the objective lens. c: Physical magnification at a Huawei photo-sensor coupled to a lens with a focal length of 3.0mm. It gives a ×180 magnification on the screen of Huawei P10 Plus with ×6 pinch-out.
d: Physical magnification at a Huawei optical sensor coupled to a lens with a focal length of 3.0mm. It gives ×500 magnification on the screen of Huawei P10 Plus with ×6 pinch-out.
e: A lens supplied from a Japanese company that is manufacturing small compound lenses for mobile cameras.
L-eye mobile microscope was adjusted by changing the focal length as shown in Table 1, and magnifications of ×180 and ×500 were used to test resolution. For the ECLIPSE E100 micro- scope, 10× and 40× objectives with a 10× intermediate lens were used for final magnifications of ×100 and ×400. For the resolu- tion comparison for the two microscopes, the Edmund Optics (Barrington, NJ) test target was employed (Figure 2), and for the image quality investigation, tissue sections were imaged (Fig- ures 3 and 4).
Results Prior to the experiments, we tested the three cameras in
the Huawei smartphone for image acquisition and found no obvious difference in image quality among them (data not shown). The performance test with the Edmund test target is
illustrated in Figure 2. The resolution of the ×180 (2.9 mm focal length) mobile microscope is approximately 500 lp/ mm (2.0 µm resolution), and that of the ×500 mobile micro- scope (0.75 mm focal length) is approxi- mately 700 lp/mm (1.4 µm resolution). Resolution of the ×100 ECLIPSE micro- scope (with a 10× objective lens) is about 600 lp/mm (1.8 µm resolution), and that of the ×400 ECLIPSE microscope (with a 40× objective lens) is about 1100 lp/mm (0.9 µm resolution). The reso- lution of the ×180 L-eye microscope is comparable to that of the ×500 L-eye microscope and slightly better than the ×100 ECLIPSE microscope, but the reso- lution of the ×500 L-eye microscope is worse than that of the ×400 ECLIPSE microscope. Two types of sections customarily
used for histology in medical education at Fujita Health University were embed- ded between a glass slide and a cover glass and examined with the L-eye (×180 and ×500) and educational (10× objective lens and 40× objective lens) microscopes. Figure 3 shows skeletal muscle from a monkey where characteristic long muscle fibers are seen with both the L-eye and educational microscopes. Te
stria-
Figure 2: Images of a microscopy test target (Edmund) taken with (a) L-eye mobile microscope with an objective of 2.9mm focal length (×180 magnification on the screen) has a resolution of 500 lp/mm or 2.0 µm; (b) L-eye mobile microscope with an objective of 0.75mm focal length (×500 magnification on the screen) has a resolution of 700 lp/mm or 1.4 µm; (c) the ECLIPSE E100 with a 10× objective lens (×100 magnification) has a resolution of 600 lp/mm or 1.8 µm, and (d) the ECLIPSE E100 with a 40× objective lens (×400 magnifi- cation) has a resolution of 1100 lp/mm or 0.9 µm. Resolution with the L-eye mobile microscope is not quite as good as with the ECLIPSE E100 but sufficient for initial education in histology. Both microscopes were mounted with the same smartphone device (Huawei P10 Plus).
2020 July •
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tions of skeletal muscle fibers are visible with the ×500 L-eye microscope but not resolved with the 180× L-eye microscope (Figure 3a), which are compared with results obtained with the educational microscope (Figure 3b), where they are visible with the 40× objective lens but not resolved with the 10× lens. Figure 4 shows tissue from rat cerebrum where
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