Optical Filter on Objective Lens for 3D Cameras
An optical bandpass filter for background light suppression in a three-dimensional time of flight camera is added on one of the lens surfaces inside the objective lens system.
1 . A camera comprising:
an objective lens system comprising a plurality of lenses;
a bandpass filter on a non-planar surface of an interior one of the lenses in the lens system, the interior one of the lenses having a range of angles of incidence such that an angle of incidence (AOI) at the bandpass filter is less than 30 degrees; and
a time of flight detector chip for detecting an image formed by the objective lens system.
2 . The camera as claimed in claim 1 , wherein the camera is a time-of-flight camera.
3 . (canceled)
4 . The camera as claimed in claim 1 , wherein the AOI at the bandpass filter is less than 10 degrees.
5 . The camera as claimed in claim 1 , wherein a passband of the bandpass filter is less than 120 nm full-width at half-maximum.
6 . The camera as claimed in claim 1 , wherein a passband of the bandpass filter is less than 100 nm full-width at half-maximum.
7 . The camera as claimed in claim 1 , wherein there are seven lenses in the objective lens system.
8 . The camera as claimed in claim 1 , wherein said bandpass filter is deposited to the posterior side of said lens.
9 . A method for imaging a scene with a time of flight camera, comprising:
illuminating the scene with modulated light;
collecting light from the scene with an objective lens system for forming an image on a time of flight detector chip of the time of flight camera; and
filtering the light from the scene using a bandpass filter on a non-planar surface of an interior lens in the objective lens system that allows the modulated light to reach the time of flight detector chip, the interior lens having a range of angles of incidence such that an angle of incidence (AOI) at the bandpass filter is less than 30 degrees.
10 . The method as claimed in claim 9 , wherein all of the lens surfaces without a bandpass filter are coated with an anti-reflective coating.
11 . The method claimed in claim 9 , wherein the bandpass filter is a posterior side of the lens.
12 . A time of flight camera comprising:
a light emitter that produces modulated light directed onto a scene;
an objective lens system for collecting the modulated light returning from the scene, the lens system comprising a plurality of lenses;
a bandpass filter deposited on a non-planar surface of an interior one of the lenses in the lens system, the bandpass filter being transmissive to the modulated light, the interior one of the lenses having a range of angles of incidence such that an angle of incidence (AOI) at the bandpass filter is less than 30 degrees; and
a time of flight detector chip for detecting an image formed by the objective lens system.
13 . The camera as claimed in claim 12 , wherein the bandpass filter is disposed on a curved surface of the lens.
14 . (canceled)
15 . The camera as claimed in claim 12 , wherein the AOI at the bandpass filter is less than 10 degrees.
16 . The camera as claimed in claim 12 , wherein a passband of the bandpass filter is less than 120 nm full-width at half-maximum.
17 . The camera as claimed in claim 12 , wherein a passband of the bandpass filter is less than 100 nm full-width at half-maximum.
18 . The camera as claimed in claim 12 , wherein said bandpass filter is deposited to the posterior side of said lens.