fNIRS Mechanical Parts
An fNIRS system is built from a relatively small set of components compared to imaging methods like MRI or CT — a reflection of how portable and lightweight the technology is.
| Component | Purpose |
|---|---|
| Laser diodes / LEDs | Emit near-infrared light, typically in the 650–950 nm range, into the scalp |
| Photodetectors (APD, SiPM, or photodiodes) | Detect the light that scatters back out of the tissue after traveling through the scalp and cortex |
| Optical fibers | Carry light between the recording instrument and the head cap, in systems that use fiber-based delivery |
| Head cap / headset | Holds the optodes in place against the scalp in a consistent, grid-like arrangement |
| Optodes (source/detector housings) | Serve as the physical interface between the scalp and the optical system, housing either a light source or a detector |
| Batteries (wireless systems) | Provide portable power for wearable or wireless fNIRS setups |
| Data acquisition electronics | Amplify and digitize the raw signal coming from the detectors |
| Cooling fans | Keep lasers and electronics within a safe operating temperature |
| Computer / workstation | Runs the acquisition software and processes the incoming data |
Why this matters for fNIRS design
Because fNIRS relies on LEDs or laser diodes rather than the heavy magnets, X-ray tubes, or radioactive tracers used in other imaging methods, the hardware can be made small, light, and low-power enough to wear. That's a big part of what makes it possible to record brain activity during real-world movement — walking, balancing, or even riding a bike — rather than requiring the patient to lie still inside a large, fixed machine.
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