Table 1.

The summary of different modulation modes based on different light sources. PLDs, pulsed laser diodes; CW-LDs, continuous laser diodes.

Light Source	Modulation Mode	Advantages	Disadvantages	Application Example
PLDs	Single pulse	Simple excitation technique	Low SNR	Portable imaging device [31]
	Code	High speed and high SNR	Complicated code sequence	Multi-wavelength imaging [76]
	Quasi-CW	Provides another image contrast	Too much heating dose	Nonlinear PA imaging [71]
LEDs	Single pulse	Lower cost	Low fiber couple efficient	Portable imaging device [68]
	Code	High speed and high SNR		Multi-wavelength imaging [27]
CW-LDs	Chirp	High speed and high SNR	Complicated data processing	Dual modality imaging [94]
	Sinusoidal	High speed and higher SNR	No depth information	Viscoelasticity imaging [96]
	Hybrid	Real-time PA sensing	Extra equipment to modulate the light	PA sensing [100]
	Single pulse	Simple excitation technique	Low SNR	Human skin imaging [34]