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Patent

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

TL;DR: In this article, the phase and surface topography measurements by wavefront propagation and refocusing, using virtual wave front propagation based on solutions of Maxwell's equations are described, and applied to Integrated Circuit inspection, to improve overlay measurement techniques, by improving contrast or by 3D imaging, in single shot imaging.
Abstract: 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.
Citations
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Patent
25 Jul 2011
TL;DR: In this article, 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.
Abstract: 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.

56 citations

Patent
Scott McEldowney1
16 Jun 2010
TL;DR: In this paper, a 3D depth camera system is used to track 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.
Abstract: 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.

49 citations

Patent
Yong-Hwa Park1, Jang-woo You1
16 Jul 2010
TL;DR: In this paper, 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 was proposed.
Abstract: 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.

18 citations

Patent
13 Nov 2006
TL;DR: In this paper, an ambiguity interval in which at least one object is located is divided into cells (5) with a defined width, with each cell assigned a counter reading and a distance.
Abstract: 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.

15 citations

Patent
16 Jun 2011
TL;DR: In this paper, 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 the size of a blur developed on the image.
Abstract: 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).

14 citations

References
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Patent
21 Sep 2002
TL;DR: In this article, a wavefront-splitting element splits the combined wavefront into a plurality of sub-wavefronts in such a way that each of the sub wavefronts is substantially contiguous with at least one other subwavefront.
Abstract: Apparatus for splitting, imaging, and measuring wavefronts with a reference wavefront and an object wavefront. A wavefront-combining element receives and combines into a combined wavefront an object wavefront from an object and a reference wavefront. A wavefront-splitting element splits the combined wavefront into a plurality of sub-wavefronts in such a way that each of the sub-wavefronts is substantially contiguous with at least one other sub-wavefront. The wavefront-splitting element may shift the relative phase between the reference wavefront and the object wavefront of the sub-wavefronts to yield a respective plurality of phase-shifted sub-wavefronts. The wavefront-splitting element may then interfering the reference and object wavefronts of the phase-shifted sub-wavefronts to yield a respective plurality of phase-shifted interferograms. An imaging element receives and images the phase-shifted interferograms. A computer connected to the imaging element measures various parameters of the objects based on the phase-shifted interferograms. Examples of measurements include flow parameters such as the concentrations of selected gaseous species, temperature distributions, particle and droplet distributions, density, and so on. In addition to flow parameters, the displacement (e.g., the vibration) and the profile of an object may be measured.

134 citations

Patent
22 Jul 2004
TL;DR: In this paper, an improved system and method for obtaining images of a microscope slide are provided, which includes an optical sensor that is tilted relative to the focal plane of a scanning camera.
Abstract: An improved system and method for obtaining images of a microscope slide are provided. In one embodiment, a focus camera (22) includes an optical sensor that is tilted relative to the focal plane of a scanning camera (32). A scan of a target region (14) are captured from a plurality of X-Y position. Each image contains information associated with multiple focal planes.

62 citations

Patent
21 Dec 2006
TL;DR: In this article, the authors proposed a method for auto-focusing and/or auto-astigmatism-correction, which consists of sequentially projecting a number of subwavefronts around an annular ring of a wavefront to a sub-wavefront focusing lens and a detector, calculating the centroid of focused light spot from each sub wavefront, adjusting the focus and or astigmatism of the optical imaging system before the wavefront sensor.
Abstract: A sequential wavefront sensor comprises a light beam scanning module (212) , a sub-wavef ront focusing lens (220) , a detector (222) with more than one photosensitive area and a processor for calculating the sequentially obtained centroids of a number focused light spots from the sub-wavefront s to determine the aberration of the input wavefront. A sequential wavefront sensing method comprises the steps of ; sequentially projecting a number of sub-wavefronts onto a sub-wavefront focusing lens and a detector with more than one photosensitive areas, calculating the centroid of the focused light spot from each sub-wavefront, and processing the centroid information to determine the aberration of the wavefront. In particular, a method for auto-focusing and/or auto-astigmatism-correction comprises the steps of sequentially projecting a number of sub-wavef ronts around an annular ring of a wavefront to a sub-wavefront focusing lens and a detector, calculating the centroid of focused light spot from each sub-wavefront to figure out the centroid trace and hence the defocus and/or astigmatism, adjusting the focus and/or astigmatism of the optical imaging system before the wavefront sensor so that the measured defocus and/or astigmatism is minimized.

54 citations

Journal ArticleDOI
TL;DR: This work has derived empirically a simple approximation formula for the entropy of images, and was able to utilize an existing TV optical nonlinear component which performed the analogue calculation of the formula at TV speed.
Abstract: The entropy or average information of an image can be determined approximately from the histogram of the image. The histogram shows the different grey level probabilities in the image. The entropy is useful, for example, for automatic image focusing: as the state of focusing of an image varies, so does its entropy. We present a method for measuring the entropy quite quickly and with reasonable accuracy. Our method is fast for two reasons: we have derived empirically a simple approximation formula for the entropy of images, and we were able to utilize an existing TV optical nonlinear component which performed the analogue calculation of our formula at TV speed. Our method can be applied to real-time focusing of two- or three-dimensional images in a TV system, for example in microscopy.

53 citations

Patent
19 Jan 2001
TL;DR: In this paper, a plurality of image detectors is arranged with respect to an objective lense to divide the light travelling through the objective lens to the detectors into channels such that each channel is registered with a respective detector.
Abstract: Volume imaging is supported in an optical apparatus that simultaneously acquires multiple images from multiple focal planes in an image object. A plurality of image detectors is arranged with respect to an objective lense. A plurality of reflective devices are disposed between the objective lense and the plurality of detectors to divide the light travelling through the objective lense to the detectors into channels such that each channel is registered with a respective detector.

49 citations