A device (2,40,50) for detecting presence of an object at the device (2,40,50), the device (2,40,50) comprising a light source, a first redirecting structure comprising a first primary redirecting structure, a second redirecting structure comprising a second primary redirecting structure, and a light detector device, wherein the light source is adapted to emit light towards the first primary redirecting structure, the first primary redirecting structure is adapted to redirect light from the light source towards the second primary redirecting structure, the second primary redirecting structure is adapted to return light from the first primary redirecting structure back towards the first primary redirecting structure, and the first primary redirecting structure is adapted to redirect light from the second primary redirecting structure towards the light detector device, and wherein the device has a sensing zone comprising a first sensing zone formed by light propagating between the first primary redirecting structure and the second primary redirecting structure, a planar waveguide comprising a first surface and a second surface and adapted for guiding light propagating from the light source towards the first redirecting structure, and for guiding light propagating from the first redirecting structure towards the light detector device, characterized in that the planar waveguide further comprising a concave surface for receiving light from the light source,, wherein the light source is facing the concave surface such that light from the light source is emitted directly into said concave surface such that diverging light is spread within the waveguide towards the first redirecting structure. a light source, a first redirecting structure comprising a first primary redirecting structure, a second redirecting structure comprising a second primary redirecting structure, and a light detector device, wherein the light source is adapted to emit light towards the first primary redirecting structure, the first primary redirecting structure is adapted to redirect light from the light source towards the second primary redirecting structure, the second primary redirecting structure is adapted to return light from the first primary redirecting structure back towards the first primary redirecting structure, and the first primary redirecting structure is adapted to redirect light from the second primary redirecting structure towards the light detector device, and wherein the device has a sensing zone comprising a first sensing zone formed by light propagating between the first primary redirecting structure and the second primary redirecting structure, a planar waveguide comprising a first surface and a second surface and adapted for guiding light propagating from the light source towards the first redirecting structure, and for guiding light propagating from the first redirecting structure towards the light detector device, characterized in that the planar waveguide further comprising a concave surface for receiving light from the light source,, wherein the light source is facing the concave surface such that light from the light source is emitted directly into said concave surface such that diverging light is spread within the waveguide towards the first redirecting structure. a first redirecting structure comprising a first primary redirecting structure, a second redirecting structure comprising a second primary redirecting structure, and a light detector device, wherein the light source is adapted to emit light towards the first primary redirecting structure, the first primary redirecting structure is adapted to redirect light from the light source towards the second primary redirecting structure, the second primary redirecting structure is adapted to return light from the first primary redirecting structure back towards the first primary redirecting structure, and the first primary redirecting structure is adapted to redirect light from the second primary redirecting structure towards the light detector device, and wherein the device has a sensing zone comprising a first sensing zone formed by light propagating between the first primary redirecting structure and the second primary redirecting structure, a planar waveguide comprising a first surface and a second surface and adapted for guiding light propagating from the light source towards the first redirecting structure, and for guiding light propagating from the first redirecting structure towards the light detector device, characterized in that the planar waveguide further comprising a concave surface for receiving light from the light source,, wherein the light source is facing the concave surface such that light from the light source is emitted directly into said concave surface such that diverging light is spread within the waveguide towards the first redirecting structure.