452
S. Perrin et al.
Fig. 17.4 Experimental demonstration of the super-resolution phenomenon through silica microspheres using white light illumination. The 5 µm-diameter microsphere is placed on the sample to
be measured. The experimental results were performed in the transmission mode using a 490-nmperiod grating and 100-nm-period pores (on the left), and also in the reflection configuration using
a 300-nm-period Blu-ray disc and a star having corners of 90 nm. Scale bars represent 500 nm
(SEM) and 5 µm (ON). Reproduced with permission from [94]. ©2018 Nature
by considering the whispering- gallery mode resonance within the microsphere [104–
106]. Furthermore, the influence of both the excitation of the electromagnetic modes
and the coherence of the light on the imaging contrast has also been highlighted [105,
107–109].
17.2.2 Performance
A theoretical expression of the super-resolution limit in microsphereassisted microscopy is thus currently not fully defined. Only experimental and numerical results allow an evaluation of the performance of this imaging technique, showing
a resolution limit of around λ/4 through simulations [105, 109, 110] and λ/6 through
experiments [103, 111] in air and in immersion. However, the quantitative evaluation of lateral resolution is often overestimated, ranging from λ/7 to λ/17 since it is
based on the measurement of the object size or the grating groove size (e.g., feature
size or inter-distance between two features) [94, 112, 113]. The limit in resolving
power of a linear imaging system is usually defined as the period of an object feature having a contrast depending on a criterion (typically, a contrast of 0 being the
cut-off frequency of the system) [114]. See, for example, the work of Duocastella et
al. with the optical frequency response characterization of a microbead coupled to a
bright-field microscope [115]. Figure 17.5 demonstrates the super-resolving power
in microsphere-assisted microscopy through an experimental measurement of the
contrast transfer function [116].
S. Perrin et al.
Fig. 17.4 Experimental demonstration of the super-resolution phenomenon through silica microspheres using white light illumination. The 5 µm-diameter microsphere is placed on the sample to
be measured. The experimental results were performed in the transmission mode using a 490-nmperiod grating and 100-nm-period pores (on the left), and also in the reflection configuration using
a 300-nm-period Blu-ray disc and a star having corners of 90 nm. Scale bars represent 500 nm
(SEM) and 5 µm (ON). Reproduced with permission from [94]. ©2018 Nature
by considering the whispering- gallery mode resonance within the microsphere [104–
106]. Furthermore, the influence of both the excitation of the electromagnetic modes
and the coherence of the light on the imaging contrast has also been highlighted [105,
107–109].
17.2.2 Performance
A theoretical expression of the super-resolution limit in microsphereassisted microscopy is thus currently not fully defined. Only experimental and numerical results allow an evaluation of the performance of this imaging technique, showing
a resolution limit of around λ/4 through simulations [105, 109, 110] and λ/6 through
experiments [103, 111] in air and in immersion. However, the quantitative evaluation of lateral resolution is often overestimated, ranging from λ/7 to λ/17 since it is
based on the measurement of the object size or the grating groove size (e.g., feature
size or inter-distance between two features) [94, 112, 113]. The limit in resolving
power of a linear imaging system is usually defined as the period of an object feature having a contrast depending on a criterion (typically, a contrast of 0 being the
cut-off frequency of the system) [114]. See, for example, the work of Duocastella et
al. with the optical frequency response characterization of a microbead coupled to a
bright-field microscope [115]. Figure 17.5 demonstrates the super-resolving power
in microsphere-assisted microscopy through an experimental measurement of the
contrast transfer function [116].