A support designed for observing between intersecting polarizers an object located in its vicinity in a medium (3) of index n.sub.0 with incident convergent incoherent illumination under an angle .theta..sub.0 at a wavelength .lamda.. The support includes a substrate (1) with complex refractive index n.sub.2 and a layer (2) of refractive index n.sub.1 and thickness e.sub.1. The value of the thickness e.sub.1 of the layer (2) is at .+-.2% such that d.sub.2 /de.sup.2.sub.1 lnIoI.sup.2=0 with O=O.sub.01+O.sub.12 (1+.pi..sub.01)e(-.sup.2j.beta..sub.1)+O.sub.01 .pi..sub.12e (-4.sup.j.beta..sub.1)/1+r.sub.01(p)+r.sub.12(p)e(.sup.-2j.beta..sub.1.su- p.))(1+r.sub.01(s).sup.r.sub.12(s).sup.e(-2.sup.j.beta..sub.1.sup.)). Observation devices incorporating such a support are also disclosed.