Abstract: A power supply system includes a RF power source configured to generate an output signal at an output frequency, a signal source configured to generate a perturbation signal, an extremum seeking frequency controller configured to generate a frequency control signal based on the perturbation signal, and a frequency selector configured to select a perturbation frequency of the perturbation signal that is isolated from at least one frequency tone associated with the power supply system. The frequency control signal varies the output frequency of the RF power source. Other example power supply system, methods for controlling a RF generator, and control systems for controlling a RF generator are also disclosed.

Abstract: A RF generator includes a RF power source configured to generate an output signal at an output frequency, and an extremum-seeking frequency controller configured to generate a frequency control signal. The frequency control signal varies the output frequency of the RF power source, and the frequency control signal is formed from a gradient signal. The RF generator further includes a gradient estimator configured to generate the gradient signal. A frequency of the frequency control signal is adjusted based on the gradient signal. The gradient estimator is configured to receive frequency values of the frequency control signal and corresponding output response values, and the gradient signal is generated based on the frequency values and the output response values. Other example RF generators, methods for extremum-seeking frequency control of a RF generator, and control systems for controlling a RF generator are also disclosed.

Abstract: A detection-based segmentation-free method and system for license plate recognition. An image of a vehicle is initially captured utilizing an image-capturing unit. A license plate region is located in the image of the vehicle. A set of characters can then be detected in the license plate region and a geometry correction performed based on a location of the set of characters detected in the license plate region. An operation for sweeping an OCR across the license plate region can be performed to infer characters with respect to the set of characters and locations of the characters utilizing a hidden Markov model and leveraging anchored digit/character locations.

Abstract: A method, system, and apparatus for license plate relighting comprises collecting an image of a license plate, performing license plate recognition on the image of the license plate; calculating a confidence metric for the license plate recognition; and performing a shadow detection and relighting method if the confidence metric is below a predetermined threshold, comprising identifying a shaded region of said license plate, determining if the shaded region is actually shaded, and relighting the actually shaded region.

Abstract: Methods and systems for localizing numbers and characters in captured images. A side image of a vehicle captured by one or more cameras can be preprocessed to determine a region of interest. A confidence value of series of windows within regions of interest of different sizes and aspect ratios containing a structure of interest can be calculated. Highest confidence candidate regions can then be identified with respect to the regions of interest and at least one region adjacent to the highest confidence candidate regions. An OCR operation can then be performed in the adjacent region. An identifier can then be returned from the adjacent region in order to localize numbers and characters in the side image of the vehicle.

Abstract: Methods, systems, and processor-readable media for the detection and classification of license plates. In an example embodiment, an image of a vehicle can be captured with an image-capturing unit. A license plate region can then be located in the captured image of the vehicle by extracting a set of candidate regions from the image utilizing a weak classifier. A set of candidate regions can be ranked utilizing a secondary strong classifier. The captured image can then be classified according to a confidence driven classification based on classification criteria determined by the weak classifier and the secondary strong classifier.

Abstract: A method and system for camera calibration comprises configuring a calibration target comprising calibration reflectors on a test vehicle. Video of a test scene is collected. Next the test vehicle is identified as it enters the test scene and recorded as it passes through the test scene. The position of the calibration target in each frame of the video is determined and the corresponding individual position of each calibration reflector for each frame of the recorded frames is used to construct a camera calibration map to calibrate the video camera.

Abstract: A method, system, and apparatus for license plate relighting comprises collecting an image of a license plate, performing license plate recognition on the image of the license plate; calculating a confidence metric for the license plate recognition; and performing a shadow detection and relighting method if the confidence metric is below a predetermined threshold, comprising identifying a shaded region of said license plate, determining if the shaded region is actually shaded, and relighting the actually shaded region.

Abstract: Methods and systems for exploiting color for object recognition. A color gradient for each pixel in a gradient image of an object can be calculated. The gradient image can be binarized to produce an image having white walls around characters and other structures. A connected component analysis operation can be performed with respect to black regions in the image to determine bounding boxes for characters and other pictorial elements in the image and thereafter identify character candidates from the image utilizing character metrics. Non-character colors can then be eliminated from the image utilizing an outlier rejection.

Abstract: Methods, systems, and processor-readable media for the detection and classification of license plates. In an example embodiment, an image of a vehicle can be captured with an image-capturing unit. A license plate region can then be located in the captured image of the vehicle by extracting a set of candidate regions from the image utilizing a weak classifier. A set of candidate regions can be ranked utilizing a secondary strong classifier. The captured image can then be classified according to a confidence driven classification based on classification criteria determined by the weak classifier and the secondary strong classifier.

Abstract: A method, system, and computer-usable tangible storage device for robustly cropping and accurately recognizing license plates to account for noise sources and interfering artifacts are disclosed. License plate images and sub-images can be tightly cropped utilizing an image-based classifier and gradient-based cropping. An image-based classifier can identify the location of valid characters within the image. Because of a number of noise sources, such as, for example, residual plate rotation and shear in the characters within the image, the image-based classifier performs a “rough” identification of the image boundaries. An additional processing step utilizing gradient-based cropping is performed to fine-tune the license plate image boundaries. Gradient-based cropping eliminates unwanted border artifacts that could substantially impact the segmentation and license plate character recognition results.

Abstract: A detection-based segmentation-free method and system for license plate recognition. An image of a vehicle is initially captured utilizing an image-capturing unit. A license plate region is located in the image of the vehicle. A set of characters can then be detected in the license plate region and a geometry correction performed based on a location of the set of characters detected in the license plate region. An operation for sweeping an OCR across the license plate region can be performed to infer characters with respect to the set of characters and locations of the characters utilizing a hidden Markov model and leveraging anchored digit/character locations.

Abstract: Methods and systems for exploiting color for object recognition. A color gradient for each pixel in a gradient image of an object can be calculated. The gradient image can be binarized to produce an image having white walls around characters and other structures. A connected component analysis operation can be performed with respect to black regions in the image to determine bounding boxes for characters and other pictorial elements in the image and thereafter identify character candidates from the image utilizing character metrics. Non-character colors can then be eliminated from the image utilizing an outlier rejection.

Abstract: Methods and systems for recognizing a license plate character. Synthetic license plate character images are generated for a target jurisdiction. A limited set of license plate images can be captured for a target jurisdiction utilizing an image-capturing unit. The license plate images are then segmented into license plate character images for the target jurisdiction. The license plate character images collected for the target jurisdiction can be manually labeled. A domain adaptation technique can be utilized to reduce the divergence between synthetically generated and manually labeled target jurisdiction image sets. Additionally, OCR classifiers are trained utilizing the images after the domain adaptation method has been applied. One or more input license plate character images can then be received from the target jurisdiction. Finally, the trained OCR classifier can be employed to determine the most likely labeling for the character image and a confidence associated with the label.

Abstract: Methods and systems for bootstrapping an OCR engine for license plate recognition. One or more OCR engines can be trained utilizing purely synthetically generated characters. A subset of classifiers, which require augmentation with real examples, along how many real examples are required for each, can be identified. The OCR engine can then be deployed to the field with constraints on automation based on this analysis to operate in a “bootstrapping” period wherein some characters are automatically recognized while others are sent for human review. The previously determined number of real examples required for augmenting the subset of classifiers can be collected. Each subset of identified classifiers can then be retrained as the number of real examples required becomes available.

Abstract: Methods and systems for bootstrapping an OCR engine for license plate recognition. One or more OCR engines can be trained utilizing purely synthetically generated characters. A subset of classifiers, which require augmentation with real examples, along how many real examples are required for each, can be identified. The OCR engine can then be deployed to the field with constraints on automation based on this analysis to operate in a “bootstrapping” period wherein some characters are automatically recognized while others are sent for human review. The previously determined number of real examples required for augmenting the subset of classifiers can be collected. Each subset of identified classifiers can then be retrained as the number of real examples required becomes available.

Abstract: Systems and methods for automating an image rejection process. Features including texture, spatial structure, and image quality characteristics can be extracted from one or more images to train a classifier. Features can be calculated with respect to a test image for submission of the features to the classifier, given an operating point corresponding to a desired false positive rate. One or more inputs can be generated from the classifier as a confidence value corresponding to a likelihood of, for example: a license plate being absent in the image, the license plate being unreadable, or the license plate being obstructed. The confidence value can be compared against a threshold to determine if the image(s) should be removed from a human review pipeline, thereby reducing images requiring human review.

Abstract: A segmentation free method and system for automatic license plate recognition. An OCR classifier can be swept across an image of a license plate. Characters and their locations can be inferred with respect to the image of the license plate using probabilistic inference based on a Hidden Markov Model (HMM). A language model can be combined with a license plate candidate from the HMM to infer the optimal or best license plate code. The language model can be configured by employing a corpus of license plate codes, wherein the corpus includes a distribution representative of training sets and tests sets.

Abstract: Methods and systems for enhancing the accuracy of license plate state identification in an ALPR (Automated License Plate Recognition) system. This is accomplished through use of individual character-by-character image-based classifiers that are trained to distinguish between the fonts for different states. At runtime, the OCR result for the license plate code can be used to determine which character in the plate would provide the highest discriminatory power for arbitrating between candidate state results. This classifier is then applied to the individual character image to provide a final selection of the estimated state/jurisdiction for the plate.

Abstract: Methods and systems for tag recognition in captured images. A candidate region can be localized from regions of interest with respect to a tag and a tag number shown in the regions of interest within a side image of a vehicle. A number of confidence levels can then be calculated with respect to each digit recognized as a result of an optical character recognition operation performed with respect to the tag number. Optimal candidates within the candidate region can be determined for the tag number based on individual character confidence levels among the confidence levels. Optimal candidates from a pool of valid tag numbers can then be validated using prior appearance probabilities and data returned, which is indicative of the most probable tag to be detected to improve image recognition accuracy.