Design Considerations for a Portable Raman Probe Spectrometer for Field Forensics

Table 1

Comparison of available NIR macro lenses as a function of F/# and their corresponding NA, collection solid angle Ω and, efficiency (assuming isotropic Raman scatter).

F/#	NA^a	Θ𝟏/2^b (deg.)	Ω (sr)	Ω/4𝜋 (%)
2.8	0.1758	10.12	2𝜋(0.015574)	0.78
			0.09785
1.8	0.2676	15.52	2𝜋(0.03647)	1.8
			0.2291
1.4	0.3363	19.65	2𝜋(0.05825)	2.9
			0.366
1.14	0.4017	23.68	2𝜋(0.08423)	4.2
			0.5292
1	0.4472	26.57	2𝜋(0.1056)	5.3
			0.6633

^aNA = sin{tan⁻¹[1/(2⋅F/#)]}.
^bΘ_1/2= tan⁻¹[1/(2⋅F/#)].