Documentation

Here you can find documentation and technical details for the miniaturized stand alone open Near InfraRed Spectroscopy (NIRS) hardware.

For the most compact, revised and up to date (Jan. 2015) documentation of the openNIRS system, please see and refer to the following publication:

von Lühmann, Herff, Heger and Schultz (2015), „Towards a wireless open source instrument: functional Near-Infrared Spectroscopy in mobile neuroergonomics and BCI applications„, frontiers in Human Neuroscience, doi:10.3389/fnhum.2015.00617

For a next generation hybrid EEG-fNIRS-Accelerometer architecture that is built on top of the openNIRS technology and significantly increases hardware performance, miniaturization and functionality, please see the following new open access M3BA publication. However, if you want to use this commercially, please note that the M3BA design is patented. Feel free to contact us on the M3BA page on this website for questions regarding licensing options.

von Lühmann, Wabnitz, Sander and Müller (2016), „M3BA: A Mobile, Modular, Multimodal Biosignal Acquisition architecture for miniaturized EEG-NIRS based hybrid BCI and monitoring„, IEEE Transactions on Biomedical Engineering, doi:10.1109/TBME.2016.2594127

Both the openNIRS and M3BA architectures are part of the following PhD thesis, where you can also find applications and experiments, and novel multimodal signal processing methods based on machine learning:

von Lühmann, Alexander (2018), „Multimodal instrumentation and methods for neurotechnology out of the lab „, Berlin Institute of Technology, doi:10.14279/depositonce-7445

A far more detailed documentation of the openNIRS hardware that is however less up to date than the openNIRS publication in frontiers can be found here:

1	Introduction			1
	1.1	Motivation		1
	1.2	Objective		2
2	State of the Technology			3
	2.1	Brief Overview of History		3
	2.2	NIRS Principle and Signals		4
	2.3	NIRS Interrogation Approaches		8
		2.3.1	Continuous Wave NIRS	8
		2.3.2	Frequency Domain NIRS	8
		2.3.3	Time Division NIRS	9
	2.4	Theoretical Background		10
	2.5	Review of existing fNIRS Technology		12
		2.5.1	NIR Light Emitters	13
		2.5.2	NIR Light Detectors	14
		2.5.3	Optical Conduction	16
		2.5.4	Signal Amplification	16
		2.5.5	Probe Designs	16
	2.6	Fields of Application		17
3	System Design			19
	3.1	Preliminary Remakrs		19
	3.2	Noise, Crosstalk and Error Sources		20
		3.2.1	Noise Errors	20
		3.2.2	Crosstalk	22
		3.2.3	Other Error Sources	22
	3.3	System Concept		23
	3.4	Hardware Design NIRS Module		26
		3.4.1	NIR Light Emitter	26
		3.4.2	NIR Light Sensor	28
		3.4.3	Amplification, Lock-In Modulation and Demodulation	30
		3.4.4	Current Regulators	34
		3.4.5	Microcontroller Unit	38
		3.4.6	General Remarks on Layout and Design	39
	3.5	Hardware Design NIRS Mainboard		40
		3.5.1	Power Supply	40
		3.5.2	Analog-to-Digital Conversion	41
		3.5.3	Communication/Bluetooth Transmission	42
		3.5.4	Microcontroller Unit	45
		3.5.5	General Remarks on Layout and Design	46
	3.6	Safety Aspects		47
	3.7	Software Design		48
		3.7.1	NIRS Module	48
		3.7.2	NIRS Mainboard	51
		3.7.3	Console Userface and Control Commands	56
		3.7.4	LabView User Interface	56
	3.8	Mechanical Design		61
		3.8.1	NIRS Module Attachment	61
		3.8.2	Mainboard and Batteries	64
4	Evaluation and Analysis			67
	4.1	Evaluation of Hardware and Design		67
		4.1.1	PWM Signal	67
		4.1.2	Power Supply	68
		4.1.3	Current Regulators	69
		4.1.4	Lock-In Detection	70
		4.1.5	System Drift	73
	4.2	Physiological Verification of the System		74
		4.2.1	Qualitative Physiological Signals: Pulse and local Blood Pressure	74
		4.2.2	BCI Trials: Mental Arithmetics	75
5	Results and Discussion			79
	5.1	System Overview		79
	5.2	Scope and Limitations		81
6	Summary and Outlook			83
A	Appendix A			87
	List of Figures			103
	List of Tables			105
	References			107