Table 2.

Summary of existing contactless 2D-imaging modes used for image capturing.

Reference	Image Capture Mode	Features and Constraints
Genovese et al. [128]	Digital camera, green LED illumination	Level-3 features
Sankaran et al. [115]	Smart phone	Unconstrained images, manual image capture
Canrey et al. [121]	Smartphone	Slap hand, on-screen guidance for multi-finger image capture.
Deb et al. [129]	Smart phone	Two fingers such as index and thump fingers, two commercial apps on 3 smartphones
Birajadar et al. [130]	Smart phone	On-screen guidance
Kumar and Zhou [131]	Webcam	Low cost, no spatial illumination
Ravi et al. [118]	Webcam	Semi-mobile, fixed, auto-focus, noisy background
Weissenfeld et al. [132]	Prototypical hardware	Multi-finger capture
Kauba et al. [133]	Smart phone	Contact-contactless comparison
Jannis Priesnitz et al. [25]	Smart phone	Multi-finger capture
Attrish et al. [126]	Prototypic hardware-RaspberryPi No infra red	Single-finger photoMinutiae and CNN features
Akmal-Jahan et al. [2,120,122]	High-resolution Digital Camera	Two fingers: index and middle finger imagesMultiple finger segmentsRidge orientation pattern