Figure 5. Spatio-temporal degrees of freedom.

Focal spots obtained when using (a) spatial degrees of freedom only, that is, eight monochromatic sources (at respectively 706 nm, 659 nm and 619 nm), and (b) temporal degrees of freedom only, that is, a single polychromatic source with various angles of incidence (the arrows represent the incident light direction). This underlines the importance of both types of degrees of freedom, as the use of polychromatic and multiple sources gives the thinnest focal spot (Fig. 3c). The color scales are normalized to the focal spot intensity.