A method to compensate for multi-path in time-of-flight (TOF) three dimensional (3D) cameras applies different modulation frequencies in order to calculate/estimate the error vector. Multi-path in 3D TOF cameras might be caused by one of the two following sources: stray light artifacts in the TOF camera systems and multiple reflections in the scene. The proposed method compensates for the errors caused by both sources by implementing multiple modulation frequencies.

Multi-path compensation using multiple modulation frequencies in time of flight sensor

A 3-D depth camera system, such as in a motion capture system, tracks an object such as a human in a field of view using an illuminator, where the field of view is illuminated using multiple diffracted beams. An image sensing component obtains an image of the object using a phase mask according to a double-helix point spread function, and determines a depth of each portion of the image based on a relative rotation of dots of light of the double-helix point spread function. In another aspect, dual image sensors are used to obtain a reference image and a phase-encoded image. A relative rotation of features in the images can be correlated with a depth. Depth information can be obtained using an optical transfer function of a point spread function of the reference image.

Use of wavefront coding to create a depth image

A method and apparatus for determining a distance between an optical apparatus and an object by considering a measured nonlinear waveform, as opposed to a mathematically ideal waveform. The method and apparatus may accurately calculate distance information without being affected by a type of waveform projected onto the object and may not require an expensive light source or a light modulator for generating a light with little distortion and nonlinearity. Further, since the method may be able to use a general light source, a general light modulator, and a general optical apparatus, additional costs do not arise. Furthermore, a lookup table, in which previously calculated distance information is stored, may be used, and thus the amount of computation required to be performed to calculate the distance is small, thereby allowing for quick calculation of the distance information in real time.

Method and apparatus for calculating a distance between an optical apparatus and an object

In order to derive distance information according to the phase measuring principle, a periodic signal with at least two, in particular modulated, wavelengths λi are transmitted to two or more objects, their reflections are received again and the associated phases φi are determined and decomposed into their individual object phases φij which are assigned to the J objects. In order to resolve phase ambiguities, an ambiguity interval in which at least one object is located is divided into cells (5) with a defined width, with each cell (5) being assigned a counter reading and a distance. The counter reading is incremented for the cells (5) which are assigned to a possible object distance, with the incrementation being carried out for a periodicity sequential variable and for all the phases. An absolute phase or a true object distance Dj from the at least two objects is determined from the distribution of the counter readings.

Method for multi-target-enabled resolution of phase ambiguity

An image processing apparatus (10) includes: an imaging device (20); an optical system (22); and a distance determining unit (16) determining an object distance between the optical system and the object based on a size of a blur developed on the image. The optical system (22) has a characteristic which simultaneously satisfies both of conditions that (i) variation in magnification is equal to or smaller than the predetermined number of pixels in the case where a focused point is set farthest from and closest to the optical system (22) in a range of the distance of the object determined by the distance determining unit (16) and (ii) variation in a PSF due to an image height of the optical system (22) is equal to or smaller than a predetermined degree so as not to affect the determination of the distance of the object by the distance determining unit (16).

Image processing device, and image processing method

Methods and apparatus to perform wavefront analysis, including phase and amplitude information, and 3D measurements in optical systems, and in particular those based on analyzing the output of an intermediate plane, such as an image plane, of an optical system. Measurement of surface topography in the presence of thin film coatings, or of the individual layers of a multilayered structure is described.. Multi-wavelength analysis in combination with phase and amplitude mapping is utilized. Methods of improving phase and surface topography measurements by wavefront propagation and refocusing, using virtual wavefront propagation based on solutions of Maxwell's equations are described. Reduction of coherence noise in optical imaging systems is achieved by such phase manipulation methods, or by methods utilizing a combination of wideband and coherent sources. The methods are applied to Integrated Circuit inspection, to improve overlay measurement techniques, by improving contrast or by 3-D imaging, in single shot imaging.

Methods and apparatus for wavefront manipulations and improved 3-d measurements

PROBLEM TO BE SOLVED: To provide a method and apparatus that performs wavefront analysis including a topology and amplitude information, and 3D measurement, especially the method and apparatus where the analysis is based on an output of an interface such as an imaging plane of an optical system. SOLUTION: The measurement is used for measuring a surface topography where individual layers of thin layer coating or multi-layer structure exist. A multiwavelength analysis is used with a combination with the topology and amplitude mapping. The method is for improving measurement of the topology and the surface topography by wavefront propagation and re-focalizing using hypothetical surface topography based on solution of the maxwell equation. The topology operation method or a method for utilizing a combination of wide-band and coherent light source achieves reduction of coherent noises in an optical imaging system. The method is applied to an analysis an integrated circuit wherein enhanced contrast or 3D imaging in a shot imaging improves an overlay measuring technique. COPYRIGHT: (C)2011,JPO&INPIT

Tal Kuzniz

Papers

Methods and apparatus for wavefront manipulations and improved 3-d measurements

Wavefront operation and improved 3d measuring apparatus