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Divergence ratio distance mapping camera

Divergence ratio distance mapping camera description/claims

The present invention relates to a method and system for detecting and mapping three-dimensional information pertaining to an object. In particular, the invention relates to a method and system that makes use of the divergence of light over distance as a means of determining distance.

Distance mapping or depth mapping cameras have become ubiquitous in numerous fields such as robotics, machine vision for acquiring three-dimensional (3D) information about objects, intelligent transport systems for assisting driver safety and navigation, bioscience for detecting 3D laparoscopic images of internal organs, non-contact fingerprinting, and image manipulation in movie or television studios.

To achieve the goal of distance mapping an object in order to acquire its 3D information, numerous methods have been developed. The triangulation method uses two or more images taken by strategically placed cameras to calculate the position of the target object. The 3D information is obtained by synchronizing the movement of the light projection spot with the direction of the return path of the light scattered to the detector. This triangulation method is limited in that it is too slow and generally can not provide for the real-time operation of a television camera.

The time of flight method makes use of the time required for a round trip of a laser beam using a phase or frequency modulated probe light. A heterodyne detection converts the phase or frequency information into the distance to the target object. While depth resolution can be within micrometers, time of flight methods can be limited to the order of minutes in providing a depth map of a target object.

Projection methods determine depth information from the patterns of configured light projected onto a target object. The best known projection method is the moiré technique. The moiré technique incorporates two grid patterns projected before and after the surface distortion to generate a moiré pattern of the deformed surface. While a moiré pattern can be readily generated, not so are the corresponding distance calculations. This distance is calculated in a manner similar to applying triangulation at every intersection of the pattern.

The AXI-VISION CAMERA™ method as described in U.S. Pat. No. 7,0165,519 B1 is based on a hybrid of the projection and time of flight methods. The projecting light is temporally rather than spatially modulated. To acquire the depth pattern, an instantaneous time of flight pattern is captured using an ultra-fast shutter. Distance is then calculated at every pixel providing a picture quality to that of High Definition Television (HDTV). To achieve its results, the AXI-VISION CAMERA™ method requires a large number of fast response time LEDs, a photomultiplier based shutter that are all secured to the AXI-VISION CAMERA™.

The object of the present invention is to provide a method and device for detecting and mapping three-dimensional information pertaining to one or more target objects while further addressing the limitations of the prior art.

A method of obtaining three-dimensional information of one or more target objects is provided, including the steps of: (1) selecting one or more target objects; (2) illuminating the one or more target objects using a first light source at a distance X1 from the target(s) and capturing an image I1 of the one or more target objects; (3) illuminating the one or more target objects using a second light source at a distance X2 from the target(s) and capturing an image I2 of the same one or more target objects; (4) calculating the distance X between the two light sources and the one or more target objects based on the decay of intensities of light sources over distances X1 and X2 using the ratio of the image intensities between images I1 and I2.

In accordance with an aspect of the method of the invention, the first image I1 and the second image I2 are stored on a storage medium known by individuals skilled in the art; the distance X at the midpoint between the two light sources and the one or more target objects is calculated by analyzing images I1 and I2 on a pixel by pixel basis; the calculated pixel distance information is stored using a known coordinate storage medium. In accordance with the method of the invention, the distance between the center of the two light sources and one or more target objects can be calculated based on the principle that the intensity of a light source decays with the inverse square of the distance traveled. A pair of light sources whose divergence factor is 1/rn where n can be either a positive or negative number (including non-integers) may be used. So long as the divergence attenuation over distance is known beforehand, a pair of sources may be used.

In accordance with the method of the invention, the one or more objects are illuminated using another pair of additional light sources for reduction of the impact of shadow on the measurement of light intensity.

In another aspect of the invention a distance mapping system is provided comprising: one or more target objects; at least one camera device and at least two light sources, and at least one computer device linked to the camera that is operable to (a) capture digital frame information, and (b) calculate distance X between the center of the light sources and one or more target objects based on the method of the present invention.

In another aspect of the invention, a distance mapping system is provided further comprising: a video microcontroller, which is operable to signal the front light source to illuminate when the camera device is in the even field and an image I1 is captured and stored. The microcontroller is operable to signal the back light source to illuminate when the camera device is in the odd field and an image I2 is captured and stored.

In yet another aspect of the present invention, a distance mapping system is provided wherein for the purposes of real time 3D information gathering, the sources are of the same type (i.e. acoustic sources or light sources).

In yet another aspect of the present invention, a distance mapping system is provided wherein to minimize the effect of light source shadowing the system further comprises an additional pair of light sources.

A detailed description of the preferred embodiment(s) is (are) provided herein below by way of example only and with reference to the following drawings, in which:

FIG. 1a illustrates the distance mapping apparatus capturing an image I1 of a target object using the first illuminating device as a light source.

• Provisional Patent
• Utility Patent

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