A display device comprising: a substrate ; two pixel circuits (PC) over the substrate spaced apart from each other with a transmission area (TA) therebetween, each of the two pixel circuits (PC) including a transistor (TFT) and a storage capacitor (Cst); two display elements (OLED) respectively electrically coupled to the two pixel circuits (PC); a bottom metal layer (BML) between the substrate and the two pixel circuits (PC) and including a through hole (BML-TH) corresponding to the transmission area (TA); an encapsulation member over the two display elements (OLED); and an optical functional layer over the encapsulation member , wherein the optical functional layer includes: a first layer including a first opening (510OP1), second openings (510P2), and a first slope portion , the first opening (510OP1) corresponding to the transmission area (TA) , the second openings (510P2) corresponding to each of the two display elements (OLED), and the first slope portion being around the transmission area (TA); and a second layer on the first layer and having a refractive index greater than a refractive index of the first layer , wherein the first opening (510OP1) and the second opening (510OP2) have the shape of a through hole through the first layer (510OP1), or have the shape of a blind hole such that a thickness of the first layer in the first opening (510OP1) and the second opening (510OP2) is less than a thickness of a remainder of the first layer . a substrate ; two pixel circuits (PC) over the substrate spaced apart from each other with a transmission area (TA) therebetween, each of the two pixel circuits (PC) including a transistor (TFT) and a storage capacitor (Cst); two display elements (OLED) respectively electrically coupled to the two pixel circuits (PC); a bottom metal layer (BML) between the substrate and the two pixel circuits (PC) and including a through hole (BML-TH) corresponding to the transmission area (TA); an encapsulation member over the two display elements (OLED); and an optical functional layer over the encapsulation member , wherein the optical functional layer includes: a first layer including a first opening (510OP1), second openings (510P2), and a first slope portion , the first opening (510OP1) corresponding to the transmission area (TA) , the second openings (510P2) corresponding to each of the two display elements (OLED), and the first slope portion being around the transmission area (TA); and a second layer on the first layer and having a refractive index greater than a refractive index of the first layer , wherein the first opening (510OP1) and the second opening (510OP2) have the shape of a through hole through the first layer (510OP1), or have the shape of a blind hole such that a thickness of the first layer in the first opening (510OP1) and the second opening (510OP2) is less than a thickness of a remainder of the first layer . a first layer including a first opening (510OP1), second openings (510P2), and a first slope portion , the first opening (510OP1) corresponding to the transmission area (TA) , the second openings (510P2) corresponding to each of the two display elements (OLED), and the first slope portion being around the transmission area (TA); and a second layer on the first layer and having a refractive index greater than a refractive index of the first layer , wherein the first opening (510OP1) and the second opening (510OP2) have the shape of a through hole through the first layer (510OP1), or have the shape of a blind hole such that a thickness of the first layer in the first opening (510OP1) and the second opening (510OP2) is less than a thickness of a remainder of the first layer . <EOS>