In this work, a two-dimensional ($n=2$) rectangular domain $\Omega $, with coordinates spanning $[\u22122.5\u2009\u2009mm,2.5\u2009\u2009mm]\xd7[\u22125\u2009\u2009mm,5\u2009\u2009mm]$, is investigated. Two types of light illumination patterns are studied: the single-direction and the multidirection illuminations. For both illumination types, two different spatial modulations of light are used. In the single-direction illumination patterns, light is set to enter the target only from one side of it. In the multidirection illuminations, light enters the target from various sides. The two different inward radiances of the single-direction illuminations are defined as Display Formula
$\varphi 0,1(r,s)={\u2212(s\xb7\nu )[1\u2212cos(2\pi 5\u2009\u2009mmy)]2,r\u2208\u2202\Omega L,s\xb7\nu \u226400,r\u2208\u2202\Omega R\u222a\u2202\Omega B\u222a\u2202\Omega T,s\xb7\nu \u22640\varphi 0,2(r,s)={\u2212(s\xb7\nu )[1+cos(3\pi 5\u2009\u2009mmy)]2,r\u2208\u2202\Omega L,s\xb7\nu \u226400,r\u2208\u2202\Omega R\u222a\u2202\Omega B\u222a\u2202\Omega T,s\xb7\nu \u22640,$(6)
where $\nu $ is the outward normal at the boundary, $\u2202\Omega L$, $\u2202\Omega R$, $\u2202\Omega T$, and $\u2202\Omega B$ correspond to left, right, top, and bottom boundaries of the rectangular domain $\Omega $, and $y\u2208[\u22125\u2009\u2009mm,5\u2009\u2009mm]$ is the vertical coordinate. The factors $[1\u2212cos(2\pi y/5\u2009\u2009mm)]2$ and $[1+cos(3\pi y/5\u2009\u2009mm)]2$ produce a positive inward radiance with sinusoidal spatial modulation on the left side of the rectangular domain. For the multidirection illuminations, the inward radiances are defined as Display Formula$\varphi 0,1(r,s)={\u2212s\xb7\nu ,r\u2208\u2202\Omega L\u222a\u2202\Omega T,s\xb7\nu \u226400,r\u2208\u2202\Omega R\u222a\u2202\Omega B,s\xb7\nu \u22640\varphi 0,2(r,s)={0,r\u2208\u2202\Omega L\u222a\u2202\Omega T,s\xb7\nu \u22640\u2212s\xb7\nu ,r\u2208\u2202\Omega R\u222a\u2202\Omega B,s\xb7\nu \u22640.$(7)