Fig. 2.

(a) Theoretical axial response (zd) to a point reflector for a dual-axes and single-axis confocal with equivalent −3-dB (FWHM) axial resolutions of 4.15 μm. Gaussian beams are assumed, truncated to allow 99% power transmission. Dual-axes specifications: n=1.4; α=0.21 rad, θ =30°, λ=1.3 μm. The single-axis NA=0.58. The main lobe of the single-axis response falls off as 1/z2, whereas the dual-axes response falls off as exp(−kz2), as expressed in Eq. (13), offering superior scattering rejection and dynamic range. (b) Theoretical transverse response (xd and yd) to a point reflector for a dual-axes confocal. Dual-axes specifications are identical to the system analyzed in part (a) (using truncated Gaussian beams). Simulated −3-dB (FWHM) resolutions are 2.41 and 2.10 μm, for the xd and yd directions, respectively.