Nvidia Corporation

Nethra Imaging Inc

Imagination Technologies Limited

Other

Hewlett-packard Development Company, L.P.

Hewlett-packard Company

Hugh Phu Nguyen

Ping Wah Wong

Yining Deng

Paul Kalapathy

Daniel R Tretter

Qian Lin

Patrick Shehane

Michael Lin

Guanghua Gary Zhang

Thomas D Kite

Eric Francois Xavier Dujardin

Abhinav Sinha

Optical center is determined on a column-by-column and row-by-row basis by identifying brightest pixels in respective columns and rows. The brightest pixels in each column are identified and a line is fit to those pixels. Similarly, brightest pixels in each row are identified and a second line is fit to those pixels. The intersection of the two lines is the optical center.

Determining optical center in an image

Alternating Current (AC) light sources can cause images captured using a rolling shutter to include alternating darker and brighter regions&#x2014;known as flicker bands&#x2014;due to some sensor rows being exposed to different intensities of light than others. Flicker bands may be compensated for by extracting them from images that are captured using exposures that at least partially overlap in time. Due to the overlap, the images may be subtracted from each other so that scene content substantially cancels out, leaving behind flicker bands. The images may be for a same frame captured by at least one sensor, such as different exposures for a frame. For example, the images used to extract flicker bands may be captured using different exposure times that share a common start time, such as using a multi-exposure sensor where light values are read out at different times during light integration. Two or more images captured for a frame may be used for flicker band extraction, such as the two images that include flicker bands with the greatest phase difference.

Detecting flicker bands using multi-exposure sensors

An efficient method and system for estimating an optimal focus position for capturing an image are presented. Embodiments of the present invention initially determine an initial lens position dataset. Then, scores are calculated for each value of the initial lens position dataset producing a plurality of scores. Embodiments of the present invention then determine an optimum focus position through interpolation and extrapolation by relating the initial lens position dataset to the score dataset, in which the score dataset comprises of the plurality of scores.

Method and system of curve fitting for common focus measures

Disclosed is a method for processing sensor data in an image processor that implements at least one image enhancement process, the method comprising: a) performing a skin tone detection operation to identify skin tone areas in the sensor data; b) selectively modifying at least one image enhancement process for the identified skin tone areas; and c) applying the at least one modified image enhancement process to the identified skin tone areas.

Skin tone detection in a digital camera

A system and method for enhanced automatic monoimaging. Embodiments of the present invention are operable for configuring a first camera based on a configuration determination by a second camera. The method includes capturing a first image with the first camera and determining an optical configuration based on an optical measurement performed by a second camera. In one embodiment, the second camera comprises a lower resolution sensor than a sensor of the first camera. The method further includes sending the optical configuration from the second camera to the first camera and adjusting a configuration of the first camera based on the optical configuration. The method further includes capturing a second image with the first camera. The first image and the second image may be preview images.

System and method for enhanced monoimaging

One embodiment of the present invention sets forth a technique for reducing flicker in image frames captured with a rolling shutter. A flicker detection and correction engine selects a first channel from a first image frame for processing. The flicker detection and correction engine subtracts each pixel value in the first channel from a corresponding pixel value in a prior image frame to generate a difference image frame. The flicker detection and correction engine identifies a first alternating current (AC) component based on a discrete cosine transform (DCT) associated with the difference image frame. The flicker detection and correction engine reduces flicker that is present in the first image frame based on the first AC component. One advantage of the disclosed techniques is that the flicker resulting from fluctuating light sources is correctly detected and reduced or eliminated irrespective of the frequency of the fluctuating light source.

DCT based flicker detection

Embodiments of the present invention initially calculate a confidence score for the image environment surrounding the subject matter in order to determine the initial number of lens positions. Once the initial lens positions are determined, a sharpness score is calculated for each determined initial lens position. Using these sharpness scores, embodiments of the present invention generate a projection used to locate an estimated optimum focus position as well as to determine an estimated sharpness score at this lens position. Embodiments of the present invention then position the lens of the camera to calculate the actual sharpness score at the estimated optimum focus position, which is then compared to the estimated optimum sharpness score previously calculated. Based on this comparison, embodiments of the present invention dynamically determine whether it has a sufficient number of lens positions to determine the optimum focus position or if additional sample lens positions are needed.

Method and system for intelligent dynamic autofocus search

In one embodiment of the invention, there is provided a method of correcting a captured image for lens shading artifacts, comprising for a given lens determining a function L(x,y) being a lens shading correction function to be applied to images captured by the lens in order to correct for lens shading artifacts; applying a sampling technique to sample the function L(x,y) at selected points; and storing the sampled function L(x,y) in memory.

Two-dimensional lens shading correction

In one embodiment of the invention, there is provided a method of correcting a captured image for lens shading artifacts, the captured image being captured by an image capture system, the method comprising: determining a function L(x, y) being a lens shading correction function to be applied to images captured by a lens of the image capture system in order to correct for lens shading artifacts; if a focal length associated with the captured image is less than a focal length associated with, the function L(x, y) then cropping the function L(x, y) based on the focal length associated with the captured image; and scaling the cropped function L(x, y) to a size of the tin-cropped Junction L(x, y).

Lens shading correction for autofocus and zoom lenses

In one embodiment, a method for controlling artifacts in an image due to a presence of flicker in ambient light is provided. The method comprises determining a power frequency for the ambient light; determining a magnitude and phase of flicker fluctuation in the image due to the flicker; and adjusting the image for the flicker fluctuation based on the power frequency, magnitude, and phase.

Method and system to reduce flicker artifacts in captured images

In one embodiment, a method for correcting image data for a captured image for lens shading artifacts is provided. The method comprises determining a plurality of one dimensional correction curves that can be applied to the image data to correct for lens shading artifacts therein; and correcting the image data for lens shading artifacts based on the one dimensional curves.

One-dimensional lens shading correction

An Internet-based printing system allows for the distribution and printing of documents and images in a secure, controlled manner. The system includes a secure printer that receives, decrypts and prints documents supplied by a document server. Security of the system is realized by an aggregate of a secure communication protocol, smart card technology and the computational infeasibility of breaking a public key cryptographic system. The system may be used for electronic commerce, in which copies are made on a 'pay-per-print' basis.

Secure network-based system for the distributed printing of documents

A process and apparatus is described to improve error diffusion halftone imaging by reducing the amount of time necessary to perform the halftoning process. This processing time reduction is produced without sacrificing the quality of the output binary images by achieving parallelism of error diffusion within an image row. The method works by cutting each image row into a number of segments and error diffusing these segments in parallel. It utilizes two different error diffusion filters: the cut filter for the pixel just before the cuts and the normal filter for the rest of the pixels. Dependencies among the segments is eliminated by ensuring that the cut filter has zero weight for the right neighboring pixel. The normal filter can be any filters that can show excellent quality of the output binary images. Banding artifacts along the cuts are minimized through careful design of the cut filter. The artifacts can also be subdued by using different positions of the cuts for different image rows, by using different cut filters for different rows, or by adding noise to the two pixels on both sides of the cuts. Alternately, a cut filter is employed that can eliminate the banding effects completely, in the majority of cases. In this design, many possible filters are evaluated and the best ones are chosen systematically. Furthermore, in the new method, the data are within an image row, and hence can be quickly rearranged to a form that will speed up parallel processing in a Single Instruction Multiple Data architecture such as the Intel MMX architecture.

Parallelized error diffusion

An improved multi-dot halftoning method to print a non-text halftone image from a non-text gray-scale image by comparing the gray-scale image to a transformed dither matrix to generate and to print the halftone image. The transformed dither matrix is tuned to reduce undesirable artifacts in the printed image. In one set of process steps to generate the transformed dither matrix, an original dither matrix with a number of original levels is picked. A selected number of the original matrix is tiled to build the large dither matrix. The large dither matrix is then transformed by operating on every original level in the large dither matrix. Each original level is split to create a group of finer levels that are in sequence and are all different from each other. A processor then replaces that original level in each of the tiled matrices by one of the finer levels such that the sequence of finer levels follows a pattern in the large dither matrix. This step of replacement is repeated for all the possible patterns; and the pattern that creates the most visually-pleasing image is selected for that original level. After the step of selecting all the patterns comes the step of incorporating all the selected patterns into the large dither matrix to form the transformed dither matrix for printing the non-text image.

Growing community of inventors

San Jose, CA, United States of America

Hugh Phu Nguyen