Active 3D triangulation-based imaging method and device

• US 20070216769A1
• Filed: 03/17/2006
• Published: 09/20/2007
• Est. Priority Date: 03/17/2006
• Status: Active Grant

• Current Assignee: Alpineon D.o.o.
• Original Assignee: Alpineon D.o.o.
• Inventors: Zganec Gros, Jerneja, Zganec, Mario
• Granted Patent: US 7,483,151 B2
• Time in Patent Office: Days
• US Class Current: 348/139
• CPC Class Codes: G01S 17/48 Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating
• CPC Class Codes: H04N 13/254 in combination with electromagnetic radiation sources for illuminating objects

Abstract

Active 3D triangulation-based imaging comprises steps of: temporally modulating a radiant flux of a lighting unit beam by a binary modulation signal (ms); illuminating a scene (S), which is illuminated by an ambient lighting (AL), by said modulated lighting unit beam (mlub); splitting a ray (ir) imaging a scene point (SP) into two separate imaging rays (ir1, ir2); said first separate imaging ray (ir1) forming an image in a first image sensor (is1); temporally modulating a radiant flux of the second separate imaging ray (ir2) by the modulation signal (ms) and said modulated second separate imaging ray (ir2m) forming an image in a second image sensor (is2); normalizing a first scene image being an image of all points of the scene (S) formed in the first sensor (is1) and a second scene image formed in the second sensor (is2); and subtracting the first normalized scene image from the second normalized scene image. The proposed imaging using the random binary modulation signal distinguishes itself by a resistance to intentionally or unintentionally caused interferences. Hence the application is especially advantageous in machine vision appliances provided in an autonomous mobile robot or vehicle. The low radiant flux of the modulated lighting unit beam makes it possible to reduce the input power to a light source of the lighting unit hereby saving the energy and reducing lighting source costs.

Claims

1. Active 3D triangulation-based imaging method comprising steps of:

temporally modulating a radiant flux of a lighting unit beam by a binary modulation signal (ms);

illuminating a scene (S), which is illuminated by an ambient lighting (AL), by said modulated lighting unit beam (mlub);

splitting a ray (ir) imaging a point (SP) of the scene (S) into two separate imaging rays (ir1, ir2);

said first separate imaging ray (ir1) forming an image of the scene point (SP) in a first image sensor (is1);

temporally modulating a radiant flux of the second separate imaging ray (ir2) by the binary modulation signal (ms) and

said modulated second separate imaging ray (ir2m) forming an image of the scene point (SP) in a second image sensor (is2);

normalizing a first scene image being an image of all points of the scene (S) formed in the first sensor (is1) and

a second scene image being an image of all points of the scene (S) formed in the second sensor (is2); and

subtracting the first normalized scene image from the second normalized scene image.

2. The method of claim 1, wherein the binary modulation signal (ms) has active as well as inactive signal states in each active signal state of a frame synchronization signal (fss).

3. The method of claim 2, wherein the cumulative duration of all active signal states and the cumulative duration of all inactive signal states of the modulation signal (ms) in each active signal state of a frame synchronization signal (fss) are approximately equal.

4. The method of claim 3, wherein the binary modulation signal (ms) is a random binary signal.

5. The method of claim 4, wherein the binary modulation signal (ms) is a Manchester encoded sequence of random binary digits.

6. The method of claim 5, wherein the binary modulation signal (ms) is a high-frequency signal.

7. Active 3D triangulation-based imaging method comprising steps of:

temporally modulating a radiant flux of a lighting unit beam by a binary modulation signal (ms);

illuminating a scene (S), which is illuminated by an ambient lighting (AL), by said modulated lighting unit beam (mlub);

forming two separate imaging rays (ir1′

, ir2′

) by deflecting a ray (ir) imaging a point (SP) of the scene (S) in the rhythm of the binary modulation signal (ms);

said first separate imaging ray (ir1′

) during an active signal state of the modulation signal (ms) forming a first image of the scene point (SP) in a first image sensor (is1);

said second separate imaging ray (ir2′

) during an inactive signal state of the modulation signal (ms) forming a second image of the scene point (SP) in a second image sensor (is2);

normalizing a first image being an image of all points of the scene (S) formed in the first sensor (is1) and

a second image being an image of all points of the scene (S) formed in the second sensor (is2); and

subtracting the first normalized scene image from the second normalized scene image.

8. Active 3D triangulation-based imaging method comprising steps of:

temporally modulating a radiant flux of a lighting unit beam by a binary modulation signal (ms);

illuminating a scene (S), which is illuminated by an ambient lighting (AL), by said modulated lighting unit beam (mlub);

a ray (ir) imaging a point (SP) of the scene (S)

during an inactive signal state of the modulation signal (ms) forming a first image of the scene point (SP) and

during an active signal state of the modulation signal (ms) forming a second image of the scene point (SP),

both said images being formed in the same image sensor (is;

sis);

normalizing

a first scene image being an image of all points of the scene (S) formed in the image sensor (is;

sis) during an inactive signal state of the modulation signal (ms) and a second scene image being an image of all points of the scene (S) formed in the same image sensor (is;

isi) during an active signal state of the modulation signal (ms); and

subtracting the first normalized scene image from the second normalized scene image.

9. Active 3D triangulation-based imaging device comprising:

a lighting unit (lu) emitting a modulated lighting unit beam (mlub), which has been temporally modulated by a binary modulation signal (ms) and which together with an ambient lighting (AL) illuminates a scene (S);

a beam splitter (bs) splitting a ray (ir) imaging a point (SP) of the scene (S) into two separate imaging rays (ir1, ir2);

a beam modulator (bm) being controlled by the binary modulation signal (ms) to temporally modulate a radiant flux of the second separate imaging ray (ir2) to produce a modulated second separate imaging ray (ir2m);

a first image sensor (is1) forming an image of the scene point (SP) by means of the first separate imaging ray (ir1);

a second image sensor (is2) forming an image of the scene point (SP) by means of the modulated second separate imaging ray (ir2m);

a processing means (p, sp) for

generating

a signal (lucs) for controlling the lighting unit (lu),

signals (iscs1, iscs2) for controlling the first image sensor (is1) and the second image sensor (is2), respectively,

the binary modulation signal (ms) controlling the lighting unit (lu) and the beam modulator (bm), and

normalizing

a first scene image being an image of all points of the scene (S) formed in the first image sensor (is1) and

a second scene image being an image of all points of the scene (S) formed in the second image sensor (is2), and

subtracting the first normalized scene image from the second normalized scene image to obtain a final scene image.

10. Active 3D triangulation-based imaging device comprising:

a lighting unit (lu) emitting a modulated lighting unit beam (mlub), which has been temporally modulated by a binary modulation signal (ms) and which together with an ambient lighting (AL) illuminates a scene (S);

a micromirror (mm) which is driven by a digital micromirror driver (dmd) controlled by the binary modulation signal (ms) and forms two separate imaging rays (ir1′

, ir2′

) by deflecting a ray (ir) imaging a point (SP) of the scene (S);

a first image sensor (is1) forming an image of the scene point (SP) by means of the first separate imaging ray (ir1′

);

a second image sensor (is2) forming an image of the scene point (SP) by means of the second separate imaging ray (ir2′

);

a processing means (p, sp) for

generating

a signal (lucs) for controlling the lighting unit (lu),

signals (iscs1, iscs2) for controlling the first image sensor (is1) and the second image sensor (is2), respectively,

the binary modulation signal (ms) controlling the lighting unit (lu) and the digital micromirror driver (dmd),

normalizing

a first scene image being an image of all points of the scene (S) formed in the first image sensor (is1), and

a second scene image being an image of all points of the scene (S) formed in the second image sensor (is2), and

subtracting

the first normalized scene image from the second normalized scene image to obtain a final scene image.

11. Active 3D triangulation-based imaging device comprising:

a lighting unit (lu) emitting a modulated lighting unit beam (mlub), which has been temporally modulated by a binary modulation signal (ms) and which together with an ambient lighting (AL) illuminates a scene (S);

an image sensor (is) forming an image of the scene point (SP) by means of a ray (ir) imaging a point (SP) of the scene (S);

a processing means (p, sp) for

generating

a signal (lucs) for controlling the lighting unit (lu),

a signal (iscs′

) for controlling the image sensor (is),

the binary modulation signal (ms) controlling the lighting unit (lu), accumulating

a first scene image being an image of all points of the scene (S) formed in the image sensor (is) during inactive signal states of the binary modulation signal (ms) and

a second scene image being an image of all points of the scene (S) formed in the image sensor (is) during active-signal states of the binary modulation signal (ms),

normalizing the first scene image and the second scene image, and subtracting the first normalized scene image from the second normalized scene image to obtain a final scene image.

12. The device of claim 11, wherein the image sensor is a smart image sensor (sis) accumulating the first scene image and the second scene image.