Light receiving device
A light receiving device comprises a condensing lens, a lens holder for mounting the condensing lens, a semiconductor light receiving element, and a lens holder, and the light transmitted through the condensing lens enters the semiconductor light receiving element via the optical path section in the lens holder. The condensing lens is a compound eye lens with a plurality of convex lens surfaces on one side, and the lens holder connects the condensing lens to the semiconductor light receiving element, and has a cylindrical reflective surface facing the optical path section formed in such a way that the diameter and a diameter decreasing rate become smaller as it approaches the semiconductor light receiving element.
1 . A light receiving device comprising a condensing lens, a lens holder that supports the condensing lens, a semiconductor light receiving element, and a base for fixing the semiconductor light receiving element and the lens holder, in which the light transmitted through the condensing lens enters the semiconductor light receiving element through an optical path section in the lens holder; wherein
the condensing lens is a compound eye lens having a plurality of convex lens surface on one side,
the lens holder has a cylindrical reflective surface facing the optical path section having a circular cross section and formed such that a diameter and a diameter decreasing rate becomes smaller as approaches the semiconductor light receiving element from the condensing lens, and
a part of the light transmitted through the condensing lens is reflected by the reflective surface and enters the semiconductor light receiving element.
2 . The light receiving device according to claim 1 , wherein when a distance from the condensing lens is x on a center line of the reflective surface passing through a center of the condensing lens, a coefficient is α, and an aperture radius of the reflective surface on the condensing lens side is A, the reflective surface is formed along a rotational curved surface obtained by rotating a curved line represented by an exponential function A×exp(−αx) about the center line.
3 . The light receiving device according to claim 1 , when a distance from the condensing lens is x on a center line of the reflective surface passing through a center of the condensing lens, a coefficient is α, and an aperture radius of the reflective surface on the condensing lens side is A, the reflective surface is formed along a rotational curved surface obtained by rotating a curved line represented by an approximate polynomial A×(1−αx+a(αx) 2 −b(αx) 3 +c(αx) 4 that is an expansion of an exponential function A×exp(−αx) up to fourth order term about the center line and is formed such that a diameter of the reflective surface on the semiconductor light receiving element side is larger than that is obtained by the exponential function.
4 . The light receiving device according to claim 2 , wherein the coefficient α of the exponential function satisfies 0.1≤α≤0.2.
5 . The light receiving device according to claim 1 , wherein the condensing lens is a compound eye lens comprising a plurality of the convex lens surface having a radius of curvature smaller than that of a partially spherical convex surface that is formed on one side of the condensing lens.
6 . The light receiving device according to claim 1 , wherein the condensing lens is a compound eye lens such that the farther it is from the center line of the reflective surface passing through the center of the condensing lens, the larger an intersection angle between the center line and the optical axis passing through the center of the convex lens surface.
7 . The light receiving device according to claim 1 , wherein the condensing lens is a compound eye lens in which a plurality of convex lens surfaces are integrally formed on a silicon substrate, and the semiconductor light receiving element receives infrared light.