WO2008098759A1 - Three-dimensional image acquisition method - Google Patents

Three-dimensional image acquisition method Download PDF

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Publication number
WO2008098759A1
WO2008098759A1 PCT/EP2008/001121 EP2008001121W WO2008098759A1 WO 2008098759 A1 WO2008098759 A1 WO 2008098759A1 EP 2008001121 W EP2008001121 W EP 2008001121W WO 2008098759 A1 WO2008098759 A1 WO 2008098759A1
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WO
WIPO (PCT)
Prior art keywords
space
corresponding pixels
camera
depicted
areas
Prior art date
Application number
PCT/EP2008/001121
Other languages
French (fr)
Inventor
Mirko Schmidt
Original Assignee
Sws Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sws Gmbh filed Critical Sws Gmbh
Publication of WO2008098759A1 publication Critical patent/WO2008098759A1/en

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B35/00—Stereoscopic photography
    • G03B35/08—Stereoscopic photography by simultaneous recording
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S11/00—Systems for determining distance or velocity not using reflection or reradiation
    • G01S11/12—Systems for determining distance or velocity not using reflection or reradiation using electromagnetic waves other than radio waves
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/50—Depth or shape recovery
    • G06T7/55—Depth or shape recovery from multiple images
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/20—Image signal generators
    • H04N13/204—Image signal generators using stereoscopic image cameras
    • H04N13/207—Image signal generators using stereoscopic image cameras using a single 2D image sensor
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10004—Still image; Photographic image

Definitions

  • the invention relates to a method of three-dimensional image acquisition (depth image acquisition) of two-dimensional image data, as it is produced by digital cameras.
  • triangulation-based methods are known, wherin active and passive methods can be distinguished.
  • the active methods employ the projecting of patterns, e.g. fringes, onto the sample.
  • a camera images the reflected light and a computer analyzes the deformation of the pattern.
  • Ambiguities in the interpretation of images can be avoided by usage of different patterns and analysing the appropriate images.
  • Passive triangulation-based methods use images, which were taken from different perspectives.
  • a software searches for corresponding regions and analyzes their location. This search of corresponding pixels is very time-consuming and in some cases extremely hard or even impossible, e.g. when the measuring object contains periodic structures that cause ambiguities. Furthermore, there may occur an occlusion problem, when parts of the object are occluded by others: the calculation of the depth of points which are seen from only one camera is not possible. Intention
  • the intention of the invention is to propose a method for triangulation-based acquisition of depth images where no correspondence problem occurs.
  • the rejection of the search for corresponding pixels enables the generation of three-dimensional data in (to the number of pixels) proportional time, which enables the possibility of real time depth image acquisition with manageable effort.
  • the two-dimensional images, used for generating the three-dimensional images are still available and can be used e.g. as a texture for the generated 3D-Object.
  • the mentioned occlusion problems of known triangulation-based methods basically do not occur, because the recorded images are almost identical.
  • Fig.l shows a setup according to claim 2, where one camera (1) is shifted orthogonally to its optical axis (4) towards (7).
  • the area between the straight lines (3) and (4) is depicted on a recognized pixel, before the camera is moved. After the motion, the area between (5) and (6) corresponds to the fixed pixel.
  • a computation of their distance is not possible.
  • An farther away located object causes, if its surface features a sufficient contrast, the measurement of different intensities of the fixed pixel.
  • the relative change of measured intensity is inversely proportional to the width of the area, which is depcited on an pixel in a given distance. Because this width is proportional to the distance between depicted object and camera, the relative change of measured intensity is inversely proportional to the distance.
  • the precision of the shown method may be further improved.
  • the attainable depth-resolution is in the same order as the resolution of intensity of the used camera or cameras respectively, while the computational effort only scales linear with the number of pixels.

Abstract

The acquisition of three-dimensional images (depth-images) of two-dimensional digital image data is done by arranging the optical system in such a way, that their optical axes are located so closely, that areas of the measured space, which are depicted by corresponding pixels, partly overlap in the entire measuring space. The depth-information is gained by analysing the differences of intensities of corresponding pixels. Hence it is possible to produce depth- information in to the number of pixels linear time, which enables real-time applications. Solving the correspondency problem, which is typical for stereoscopic methods, is not necessary and occlusion problems do not occur.

Description

Three-dimensional image acquisition method
Description of the invention
Field of the Invention
The invention relates to a method of three-dimensional image acquisition (depth image acquisition) of two-dimensional image data, as it is produced by digital cameras.
Description of the Prior Art
The generation of three-dimensional image data by analysing the time of flight which the light needs to cover the distance from a light source to the sample and back to the camera is known. There exist methods, which use pulses of light i.e. switch a light source on and off, and phase- based methods, which utilise a modulation of the amplitude of a light source. Both methods measure the time difference between the signal at the source and the changing lens at the camera; this time divided by two and multiplicated with the speed of light gives the distance between the point of the object and the camera.
Furthermore, triangulation-based methods are known, wherin active and passive methods can be distinguished. The active methods employ the projecting of patterns, e.g. fringes, onto the sample. A camera images the reflected light and a computer analyzes the deformation of the pattern. Ambiguities in the interpretation of images can be avoided by usage of different patterns and analysing the appropriate images.
Passive triangulation-based methods use images, which were taken from different perspectives. A software searches for corresponding regions and analyzes their location. This search of corresponding pixels is very time-consuming and in some cases extremely hard or even impossible, e.g. when the measuring object contains periodic structures that cause ambiguities. Furthermore, there may occur an occlusion problem, when parts of the object are occluded by others: the calculation of the depth of points which are seen from only one camera is not possible. Intention
Based on the known state of art, the intention of the invention is to propose a method for triangulation-based acquisition of depth images where no correspondence problem occurs. The rejection of the search for corresponding pixels enables the generation of three-dimensional data in (to the number of pixels) proportional time, which enables the possibility of real time depth image acquisition with manageable effort. Furthermore, the two-dimensional images, used for generating the three-dimensional images, are still available and can be used e.g. as a texture for the generated 3D-Object. The mentioned occlusion problems of known triangulation-based methods basically do not occur, because the recorded images are almost identical.
Execution examples
Execution examples are explained using the following figures.
Fig.l shows a setup according to claim 2, where one camera (1) is shifted orthogonally to its optical axis (4) towards (7). The area between the straight lines (3) and (4) is depicted on a recognized pixel, before the camera is moved. After the motion, the area between (5) and (6) corresponds to the fixed pixel. For objects being located between (8) and the camera, a computation of their distance is not possible. An farther away located object causes, if its surface features a sufficient contrast, the measurement of different intensities of the fixed pixel. The relative change of measured intensity is inversely proportional to the width of the area, which is depcited on an pixel in a given distance. Because this width is proportional to the distance between depicted object and camera, the relative change of measured intensity is inversely proportional to the distance.
If you eye a pixel and its adjacent pixels (in the direction of the shift of the camera) of the first image and the pixel with the same coordinates of the second image with the intensities p left, p mid, p_right and p mid two, you find the quantity (p_mid - p mid two) / (pjeft - p right) in inverse proportion to the distance between the object imaged by the pixel p mid and the camera.
With the setup shown in Fig.2, which combines the fields of vision of two cameras (1) and (2) by using beamsplitters (7) and (8), the same measurement can be done in less time, because no parts need to be moved and both images can be acquired at the same time.
By using more efficient mathematical methods for estimating the distance of pixels, e.g. quadratical instead of mentioned linear fit of intensities of adjacent pixels, the precision of the shown method may be further improved.
The attainable depth-resolution is in the same order as the resolution of intensity of the used camera or cameras respectively, while the computational effort only scales linear with the number of pixels.

Claims

Claims
1. Method of depth image acquisition based on digital image data of two or more perspectives,
characterized by the fact, that the optical axes of the optical systems are located so closely, that areas of the measured space, which are depicted by corresponding pixels, partly overlap in the entire measuring space.
2. A method as claimed in claim 1,
characterized by the fact, that one camera is used, which after acquiring one first image is shifted orthogonal and/or parallel to its optical axis and acquires at least one more image, in such a way, that areas of the measured space, which are depicted by corresponding pixels, partly overlap in the entire measuring space.
3. A method as claimed in claim 1,
characterized by the fact, that a beamsplitter is used to arrange the optical axes of at least two cameras in space, so that areas of the measured space, which are depicted by corresponding pixels, partly overlap in the entire measuring space.
4. A method as claimed in claim 1,
characterized by the fact, that between at least one camera and the sample an appropriate optical element, e.g. a slice of glass, which can be rotated on an axis which is perpendicular to the optical axis/axes of the camera(s), is positioned, and manipulates the extension of the optical axis/axes into the measuring volume in that way, that areas of the measured space, which are depicted by corresponding pixels, partly overlap in the entire measuring space.
PCT/EP2008/001121 2007-02-12 2008-02-09 Three-dimensional image acquisition method WO2008098759A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102007007775.2 2007-02-12
DE102007007775A DE102007007775A1 (en) 2007-02-12 2007-02-12 Method for three-dimensional image data acquisition

Publications (1)

Publication Number Publication Date
WO2008098759A1 true WO2008098759A1 (en) 2008-08-21

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DE (1) DE102007007775A1 (en)
WO (1) WO2008098759A1 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5907434A (en) * 1995-03-20 1999-05-25 Canon Kabushiki Kaisha Image pickup apparatus
US20020008757A1 (en) * 2000-05-17 2002-01-24 Seiji Sato Stereoscopic picture image forming apparatus

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5907434A (en) * 1995-03-20 1999-05-25 Canon Kabushiki Kaisha Image pickup apparatus
US20020008757A1 (en) * 2000-05-17 2002-01-24 Seiji Sato Stereoscopic picture image forming apparatus

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