Detection head
A reflective sensor is disclosed which prevents divergent light from a light source from being totally reflected by an interface between the package and the outside thereof and entering a light-receiving element without using a light-shield means and which allows an improved S/N ratio and reduced variations in performance. The reflective sensor includes a light-emitting element and a light-receiving element which are provided on a surface, and a light-transmissive member which covers the light-emitting element and the light-receiving element. The light-receiving element includes a light-receiving region which is spaced from the light-emitting element along the surface, and which light-receiving region is closer to the light-emitting element than an area on the surface that would be illuminated by unimpeded light rays which are totally reflected by an interface between the light-transmissive member and the outside thereof and are directed toward the light-receiving element.
1. A detection head comprising:
a light-emitting element and a light-receiving element which are provided on a surface; and
a light-transmissive member which covers the light-emitting element and the light-receiving element,
wherein the light-emitting element includes a light-emitting region, and the light-receiving element includes a light-receiving region which is spaced from the light-emitting region along the surface,
wherein the light-receiving region is closer to the light-emitting region than a region illuminated with light rays which are totally reflected by an interface between the light-transmissive member and the outside thereof and are directed toward the light-receiving element, and
wherein the light-transmissive member is formed of a light-transmissive resin covering over the light-emitting element and the light-receiving element and a light-transmissive glass covering over the light-transmissive resin.
2. A detection head according to claim 1 , wherein the light-emitting element is formed of an LED having a current confinement structure.
3. A detection head according to claim 1 , wherein the light-receiving region has a sector shape or an arc shape.
4. An apparatus comprising a detection head according to claim 1 , wherein the apparatus operates based on information provided by the detection head.
5. A detection head comprising:
a light-emitting element and a light-receiving element which are provided on a surface; and
a light-transmissive member which covers the light-emitting element and the light-receiving element,
wherein the light-receiving element includes a light-receiving region which is provided on the surface within a circle having a radius R from the center of a light-emitting region of the light-emitting element, the radius R being determined as follows:
R=D 1·tan{sin −1 ( No/Ni )}+ D 2·tan{sin −1 ( No/Ni )}
where Ni represents a refractive index of the light-transmissive member having an interface between the light-transmissive member and the outside thereof, No represents a refractive index of a medium outside of the light-transmissive member which is different from Ni, D 1 represents a distance from the light-emitting region of the light-emitting element to the interface, and D 2 represents a distance from the light-receiving region of the light-receiving element to the interface.
6. A detection head according to claim 5 , wherein the light-receiving element is formed of a photo-IC including a light-receiving portion formed of a plurality of photodiodes and a signal processing part formed of a plurality of first-stage amplifiers and a differential amplifier.
7. An apparatus comprising a detection head according to claim 5 , wherein the apparatus operates based on information provided by the detection head.