Fig. 3.

Examples of modular devices. (a) The spring-loaded modular fNIRS device described by von Lühmann et al. The subfigure on the left demonstrates the mechanical spring-loaded concept; the subfigure on the right shows a single fNIRS module and the base station: N represents the fNIRS module, B indicates the Bluetooth module, BAT indicates the battery, R1/R2 are the rotatory joints, and M indicates the main aboard. This figure is taken with permission from Ref. 32. (b) The SiPM-based modular fNIRS device from Zimmermann et al., constructed on two stacked PCBs. The upper PCB houses the optoelectronics, while the lower board acts as a control unit. This figure is taken with permission from Ref. 34. (c) An IC-based modular fNIRS device described by Choi et al., consisting of a head-based subassembly and an external MCU. This figure is taken with permission from Ref. 35.