Compact 3D scanner with fixed pattern projector and dual band image sensor
View Patent ↗A structured light 3D scanner consisting of a specially designed fixed pattern projector and a camera with a specially designed image sensor is disclosed. A fixed pattern projector has a single fixed pattern mask of sine-like modulated transparency and three infrared LEDs behind the pattern mask; switching between the LEDs shifts the projected patterns. An image sensor has pixels sensitive in the visual band, for acquisition of conventional image and the pixels sensitive in the infrared band, for the depth acquisition.
1. A 3D scanning apparatus, comprising:
a camera with a dual-band image sensor, with some pixels sensitive in the visible optical band and some other pixels sensitive in the invisible optical band;
a fixed pattern projector, having a single fixed mask of varying transparency and two or more infrared light sources behind said single fixed pattern mask having different relative positions, configured to project patterns in the invisible optical band on an object; wherein said camera is configured to acquire a visible light image of the object and an invisible light image of the object and the patterns, said visible and visible light images captured at the same time, and to reconstruct a 3D shape of the object based on said acquired patterns;
wherein said projected pattern varies according to the combination of spatial variance of the single pattern mask and a difference between the different relative positions; and
wherein the pattern mask has a sine-function varying transparency having a period D, and three infrared light emitting diodes placed at distances D/3 so that sequential switching between them results in sequential projection of three sine-modulated patterns, mutually phase shifted by 2π/3.
2. Apparatus according to claim 1 , wherein said pixels sensitive in the visible band are tiled in an interlaced manner with said pixels sensitive in the invisible band.
3. Apparatus according to claim 1 , wherein said camera further comprises three types of color filters and fourth type of filter filtering in the infrared band.
4. Apparatus as in claim 3 , wherein said image sensor comprises a plurality of groups of pixels, each group of pixels having, in a two-by-two quadrangular arrangement, a pixel transmitting in the red, a pixel transmitting in the green, a pixel transmitting in the blue and a pixel transmitting in the infrared.
5. Apparatus as in claim 3 , wherein said image sensor comprises a plurality of groups of pixels, each group of pixels having, in a two-by-two quadrangular arrangement a pixel transmitting in the cyan, a pixel transmitting in the magenta, a pixel transmitting in the yellow and a pixel transmitting in the infrared.
6. Apparatus according to claim 1 , wherein said single pattern mask has a sine-like varying transparency.
7. A method of constructing a three-dimensional shape of an object, comprising:
projecting patterns in the invisible optical band on the object with the scanning apparatus of claim 1 ;
using a dual band image sensor having some pixels sensitive in the visible optical band and some other pixels sensitive in the invisible optical band for acquiring a visible light image of the object and an invisible light image of the object and said patterns with the scanning apparatus of claim 1 ; and
reconstructing the three-dimensional shape of the object based on said acquired patterns.
8. A method according to claim 7 , wherein said projecting said patterns is sequential.
9. A method according to claim 8 , wherein said dual-band image sensor comprises a plurality of groups of pixels, each group of pixels having, in a two-by-two quadrangular arrangement, three pixels respectively transmitting in three different visible bands and one pixel transmitting in the invisible optical band.
10. A method according to claim 9 , wherein said three different visible bands are selected from the group consisting of (i) red, green and blue optical bands, and (ii) cyan, magenta and yellow optical bands.
11. A method according to claim 9 , wherein said invisible optical band comprises an infrared band.