Figure 9.6 — Transverse forward scattering and transverse position detection Fig. 9.6 — Transverse forward scattering and transverse position detection. (a) Images of the field at the back focal plane of the condenser for various particle radii a and particle transverse displacement C = [Cx , 0, 0]. The circles delimit the areas of the field that is captured by the condenser lens with NAo = 0.20, 0.65 and 1.20 (solid line) from the centre outwards. Signal from a (b) QPD and (c) PSD as a function of Cx for the case of a = 400 nm (dotted line), a = 600 nm (dashed line) and a = 1000 nm (solid line) for an incident beam with power 1 mW and detection NAc = 1.20.