Color ranging method for high speed low-cost three dimensional surface profile measurement

• US 5,675,407 A
• Filed: 03/02/1995
• Issued: 10/07/1997
• Est. Priority Date: 03/02/1995
• Status: Expired due to Fees

• Current Assignee: Genex Technologies Incorporated (AccelPath, Inc.)
• Original Assignee: Zheng Jason Geng
• Inventors: Geng, Zheng Jason
• Primary Examiner(s): Gonzalez, Frank
• Assistant Examiner(s): Ratliff, Reginald A.
• Application Number:
  US08/397,766
• Time in Patent Office: 950 Days
• Field of Search: 356/375, 356/376, 356/121, 356/122, 356/123, 356/138, 356/147
• US Class Current: 356/147
• CPC Class Codes: G01B 11/2509 Color coding
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: H04N 13/214 using spectral multiplexing
• CPC Class Codes: H04N 13/25 using two or more image sensors with different characteristics other than in their location or field of view, e.g. having different resolutions or colour pickup characteristics; using image signals from one sensor to control the characteristics of another sensor
• CPC Class Codes: H04N 2013/0081 Depth or disparity estimation from stereoscopic image signals

Abstract

The target of the present invention is to provide an automatic high speed, low-cost, multi-mode three-dimensional(3D) surface profile measurement method. This method exploits the projected energy with a known spatially distributed wavelength spectrum on the surface of objects in the scene. The unique wavelength is encoded with geometry information of a unique projection ray of the radiation energy in 3D space. This wavelength of the projected energy is detected by a 2D image sensor array that is able to uniquely distinguish the wavelength of the radiation energy at the points of interest on the scene. The projection geometry information is recovered by using a color match scheme and the range values associated with every pixel of the 2D image sensor will be calculated through a straightforward triangulation algorithm. Full frames of 3D range images can then be obtained directly at the frame acquisition rate of the 2D image sensor array. The color ranging method eliminates the time consuming corresponding feature finding problem of normal binocular 3D imaging systems. Therefore, it is suitable for high speed, real-time measurement automation. Since there are no mechanical moving parts in our color ranging method, the mechanical design can be very simple and reliable. All components in this system are available off-the-shelf which leads to low cost. With the active light source being turned on or off, the same color camera can provide normal intensity images as well as 3D range data. This multi-mode capability greatly simplifies the problems of multiple sensor integration and sensor data fusion. Depending on the applications, the scope of the color spectrum of the energy projector can be selected from UV, visible, or IR light region. The Color Ranging method is not based on a laser therefore there is no "eyes safe" problem. This is certainly a desirable feature enable this system to be used for other commercial applications, such as medical applications like the facial plastic reconstruction surgery evaluation.

Claims

1. An apparatus for determining projection angles of light rays based on values of the wavelength of the projected individual light ray, comprising

(a) a light projection means for generating a bundle of light rays with spatially varying wavelengths to illuminate surface of objects in the scene such that light rays projected from different projection angles (θ

) have different spectral wavelengths (λ

), and

(b) a sensor means for detecting the wavelengths (λ

) of light rays reflected from objects'"'"' surface that is illuminated by said light projection means, and

(c) a calibration means for relating the wavelengths (λ

) detected by said sensor to the light ray projection angles (θ

),

whereby projection angles (θ

) of light rays can be determined based on the wavelengths (λ

) of the light rays detected by the sensor.

2. An apparatus as recited in claim 1, wherein the structured illumination is generated by using a light source and a variable wavelength filter for producing simultaneously a bundle of light rays spreading more than one dimensions and with spatially varying wavelengths.

3. An apparatus as recited in claim 1, wherein the structured illumination is generated by using a light source and a prism for producing simultaneously a bundle of light rays spreading more than one dimensions and with spatially varying wavelengths.

4. An apparatus as recited in claim 1, wherein the structured illumination is generated by using a light source and a diffraction grating for producing simultaneously a bundle of light rays spreading more than one dimensions and with spatially varying wavelengths.

5. An apparatus for determining 3D coordinates of surface points of objects in the scene, comprising

(a) a light projection means for generating a bundle of light rays with spatially varying wavelengths to illuminate surface of objects in the scene such that light rays projected from different projection angles (θ

) have different spectral wavelengths (λ

), and

(b) a sensor array means for detecting the wavelengths (λ

) of light rays reflected from objects'"'"' surface that is illuminated by said light projection means, and for determining the viewing angle (α

) of the surface point corresponding to each pixel of the image sensor array based on image sensor'"'"'s geometric and optical parameters, and

(c) a calibration means for relating the wavelengths (λ

) detected by each pixel of said sensor array to light ray projection angles (θ

) for surface points viewed by all pixels of the sensor means, and

(d) an data extraction means for computing distances in the 3D space between the focal point of the image sensor array and surface points in the scene (and therefore determining 3D coordinates of surface points of objects in the scene), based on (i) values of light projection angles (θ

) determined by said sensor array and said calibration means, (ii) viewing angles (α

) of pixels in said sensor array determined by its geometric and optical parameters, and (iii) distance between said image sensor and said light projector in the 3D space.

whereby full frames of 3D images, in which each pixel value represents a 3D distance between the focal point of the image sensor array and a surface point in the scene corresponding to the pixel, can be obtained at sensor array'"'"'s frame rate.

6. An apparatus as recited in claim 5, wherein the structured illumination is generated by using a light source and a variable wavelength filter for producing simultaneously a bundle of light rays spreading more than one dimensions and with spatially varying wavelengths.

7. An apparatus as recited in claim 5, wherein the structured illumination is generated by using a light source and a prism for producing simultaneously a bundle of light rays spreading more than one dimensions and with spatially varying wavelengths.

8. An apparatus as recited in claim 5, wherein the structured illumination is generated by using a light source and a diffraction grating for producing simultaneously a bundle of light rays spreading more than one dimensions and with spatially varying wavelengths.