A bio-detection device, comprising: a plurality of pixel units (100A-100E), wherein each of the pixel units (100A-100E comprises: a substrate; a plurality of pairs of reflective sub-polarizing units disposed on the substrate, wherein a difference of the absolute value between respective polarizing angles of the reflective sub-polarizing units in each pair of reflective sub-polarizing units is 90°; and a plurality of reaction sites defined above the plurality of pairs of reflective sub-polarizing units, wherein the reaction sites and the reflective sub-polarizing units are in one-to-one correspondence; wherein the reaction sites are defined by openings formed in a sample isolation layer formed on the reflective sub-polarizing units such that a bottom surface of the reaction site is a bottom surface of the opening formed in the sample isolation layer; and wherein the reaction sites corresponding to the reflective sub-polarizing units in a same pair of reflective sub-polarizing units have a same height that is measured from top surfaces of the reflective sub-polarizing units to the bottom surfaces of the reaction sites, and wherein the reaction sites corresponding to the reflective sub-polarizing units in different pairs of reflective sub-polarizing units have different heights that are measured from the top surfaces of the reflective sub-polarizing units to the bottom surfaces of the reaction sites. a plurality of pixel units (100A-100E), wherein each of the pixel units (100A-100E comprises: a substrate; a plurality of pairs of reflective sub-polarizing units disposed on the substrate, wherein a difference of the absolute value between respective polarizing angles of the reflective sub-polarizing units in each pair of reflective sub-polarizing units is 90°; and a plurality of reaction sites defined above the plurality of pairs of reflective sub-polarizing units, wherein the reaction sites and the reflective sub-polarizing units are in one-to-one correspondence; a substrate; a plurality of pairs of reflective sub-polarizing units disposed on the substrate, wherein a difference of the absolute value between respective polarizing angles of the reflective sub-polarizing units in each pair of reflective sub-polarizing units is 90°; and a plurality of reaction sites defined above the plurality of pairs of reflective sub-polarizing units, wherein the reaction sites and the reflective sub-polarizing units are in one-to-one correspondence; wherein the reaction sites are defined by openings formed in a sample isolation layer formed on the reflective sub-polarizing units such that a bottom surface of the reaction site is a bottom surface of the opening formed in the sample isolation layer; and wherein the reaction sites corresponding to the reflective sub-polarizing units in a same pair of reflective sub-polarizing units have a same height that is measured from top surfaces of the reflective sub-polarizing units to the bottom surfaces of the reaction sites, and wherein the reaction sites corresponding to the reflective sub-polarizing units in different pairs of reflective sub-polarizing units have different heights that are measured from the top surfaces of the reflective sub-polarizing units to the bottom surfaces of the reaction sites.