A sensor assembly comprising: a housing having an aperture; a diffusing element positioned across said aperture and having an upper surface and a lower surface for diffusing light approximately equally in every direction; and a sensor device comprising: a support structure, wherein said support structure is a portion of a lead frame; a sensing element mounted on said support substrate for sensing optical radiation and generating an electrical output signal in response thereto, wherein said portion of the lead frame includes at least two leads (95a-95d) electrically coupled to said sensing element; the sensor assembly being characterised in that the diffuser upper surface contains parallel grooves, in that the diffuser lower surface is an irregular surface, and in that the sensor assembly comprises an encapsulant encapsulating said sensing element on said support structure, said encapsulant being configured to define an integral lens portion for focusing optical radiation that is brought to alignment by the diffusing element and that is incident on the integral lens portion onto an active surface of said sensing element, and an optical radiation collector portion surrounding the lens portion for collecting and redirecting optical radiation that is brought to alignment by the diffusing element and that is not incident on the lens portion onto the active surface of said sensing element, wherein the optical radiation collector portion includes an annular optical radiation receiving surface that lies in a plane perpendicular to the axis of the lens portion and is disposed around the lens portion. a housing having an aperture; a diffusing element positioned across said aperture and having an upper surface and a lower surface for diffusing light approximately equally in every direction; and a sensor device comprising: a support structure, wherein said support structure is a portion of a lead frame; a sensing element mounted on said support substrate for sensing optical radiation and generating an electrical output signal in response thereto, wherein said portion of the lead frame includes at least two leads (95a-95d) electrically coupled to said sensing element; the sensor assembly being characterised in that the diffuser upper surface contains parallel grooves, in that the diffuser lower surface is an irregular surface, and in that the sensor assembly comprises an encapsulant encapsulating said sensing element on said support structure, said encapsulant being configured to define an integral lens portion for focusing optical radiation that is brought to alignment by the diffusing element and that is incident on the integral lens portion onto an active surface of said sensing element, and an optical radiation collector portion surrounding the lens portion for collecting and redirecting optical radiation that is brought to alignment by the diffusing element and that is not incident on the lens portion onto the active surface of said sensing element, wherein the optical radiation collector portion includes an annular optical radiation receiving surface that lies in a plane perpendicular to the axis of the lens portion and is disposed around the lens portion. a support structure, wherein said support structure is a portion of a lead frame; a sensing element mounted on said support substrate for sensing optical radiation and generating an electrical output signal in response thereto, wherein said portion of the lead frame includes at least two leads (95a-95d) electrically coupled to said sensing element; the sensor assembly being characterised in that the diffuser upper surface contains parallel grooves, in that the diffuser lower surface is an irregular surface, and in that the sensor assembly comprises an encapsulant encapsulating said sensing element on said support structure, said encapsulant being configured to define an integral lens portion for focusing optical radiation that is brought to alignment by the diffusing element and that is incident on the integral lens portion onto an active surface of said sensing element, and an optical radiation collector portion surrounding the lens portion for collecting and redirecting optical radiation that is brought to alignment by the diffusing element and that is not incident on the lens portion onto the active surface of said sensing element, wherein the optical radiation collector portion includes an annular optical radiation receiving surface that lies in a plane perpendicular to the axis of the lens portion and is disposed around the lens portion.