Fig. 1. Smartphone-based optical interface design spectrum^[8]

Fig. 2. Smartphone with a dermatoscope adapter^[16]

Fig. 3. Two dermatoscope implementations^[19]. (a) Handheld imaging module; (b) imaging module paired with the smartphone camera; (c) smartphone-based system; (d) system with the imaging annulus; (e) smartphone with dermatoscope

Fig. 4. Same junctional nevus imaged by the smartphone and USB dermatoscopes^[19]. (a) Junctional nevus imaged by smartphone dermatoscope; (b) junctional nevus imaged by USB dermatoscope

Fig. 5. Schematic of scanning^[27]. (a) Schematic of point scanning; (b) spectrally-encoded line scanning; (c) smartphone confocal microscope

Fig. 6. Smartphone-based fundus cameras in the market^[31]. (a) iExaminer; (b) D-Eye; (c) Peek Retina; (d) iNview

Fig. 7. Retinal images^[30]. (a)‒(c) Three representative single-shot images taken at three different angles of a 41-year-old subject without eye disease; (d) montage of three single-shot images; (e) representative fundus image from the same subject collected by a clinical fundus camera; (f) overlap of Fig.7(c) and Fig. 7(e)

Fig. 8. Photo of the smartphone slit lamp and schematic of the optical path of smartphone slit lamp^[38]

Fig. 9. Smartphone-based corneal topographer^[41]

Fig. 10. Intraoral probe system view showing the handheld probe^[45].^{(a) Overall system size; (b) (c) two sides of the flexible head; (d) imaging and LED illumination apertures; (e) smartphone running the custom Android application; (f) installed electronic equipment}

Fig. 11. Developed add-on gadget and its usage for data acquisition^[47]. (a) Add-on gadget designed and manufactured by 3D printing; (b) image acquisition using the iPhone X with the add-on gadget

Fig. 12. Lens simulation of smartphone-based endoscope system^[48]. (a) Ray-tracing of optics for smartphone-based endoscope system; (b) schematic of assembled lens system in smartphone-based endoscope system

Fig. 13. Enhanced visual assessment system^[49]

Fig. 14. Tethered capsule endoscopic platform^[56]. (a) Picture of the endoscope along with a smartphone; (b) image of the WLI capsule; (c) spectrum of the integrated white light LED; (d) schematic of the NBI module; (e) attachable smartphone capsule unit; (f) schematic of the FI/AFI module; (g) a portable imaging system in a 28 cm×16 cm box