Patent Publication Number: US-2019180150-A1

Title: Color Haar Classifier for Retail Shelf Label Detection

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     The present disclosure is part of a continuation of U.S. Patent Application No. 62/598,263, filed on Dec. 13, 2017, the content of which is incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to a multiple camera sensor suite capable of accurately monitoring retail or warehouse product. In certain embodiments, the multiple camera sensor suite can be mounted on an autonomous robot able to detect and recognize shelf labels using color Haar classifiers. 
     BACKGROUND 
     Retail stores or warehouses can have thousands of distinct products that are often sold, removed, added, or repositioned. Even with frequent restocking schedules, products assumed to be in stock may be out of stock, decreasing both sales and customer satisfaction. Point of sales data can be used to roughly estimate product availability, but does not help with identifying misplaced, stolen, or damaged products, all of which can reduce product availability. However, manually monitoring product inventory and tracking product position is expensive and time consuming. 
     Development of automatic systems to identify products and related information can be difficult. Often, only limited memory and processing power is available to detect and recognize products or associated product indicators such as shelf labels. Machine learning methods for shelf label identification need to be fast, typically on the order of seconds, and reliable enough for accurate reading of hundreds of different shelf label types. In addition, machine learning systems should be quick to train using a limited number of training examples, increasing usability and reducing training times in environments with new shelf label types or variations. 
     SUMMARY 
     A low cost, accurate, and scalable camera system for product or other inventory monitoring can include a movable base. Multiple cameras supported by the movable base are directable toward shelves or other systems for holding products or inventory. A processing module is connected to the multiple cameras and able to construct from the camera derived images an updateable map of product or inventory position. 
     In some embodiments, the described camera system for inventory monitoring can be used for detecting shelf labels; optionally comparing shelf labels to a depth map; defining a product bounding box; associating the bounding box to a shelf label to build a training data set; and using the training data set to train a product classifier. 
     In other embodiments, a system for building a product library can include an image capture unit operated to provide images of items. The system also includes a shelf label detector (which can be a high-resolution zoomable camera) and optionally depth map creation unit (which can be provided by laser scanning, time-of-flight range sensing, or stereo imaging), a processing module to optionally compare detected shelf labels to a depth map, define a product bounding box, and associate the bounding box with a shelf label to build a training data set or learn image descriptors. Both the image capture unit and processing module can be mounted on an autonomous robot. 
     Because it represents reality on the shelf, an inventory map such as disclosed herein can be known as a “realogram” to distinguish from conventional planograms. Realograms can be locally stored with a data storage module connected to the processing module. A communication module can be connected to the processing module to transfer realogram data to remote locations, including servers or other supported camera systems, and optionally receive inventory information including planograms to aid in realogram construction. In addition to realogram mapping, this system can be used to detect out of stock products, estimate depleted products, estimate amount of products including in stacked piles, estimate products heights, lengths and widths, build 3D models of products, determine products&#39; positions and orientations, determine whether one or more products are in disorganized on-shelf presentation that requires corrective action such as facing or zoning operations, estimate freshness of products such as produce, estimate quality of products including packaging integrity, locate products, including at home locations, secondary locations, top stock, bottom stock, and in the backroom, detect a misplaced product event (also known as a plug), identify misplaced products, estimate or count the number of product facings, compare the number of product facings to the planogram, locate labels, determine sequence of labels, detect label type, read label content, including product name, barcode, UPC code and pricing, detect missing labels, compare label locations to the planogram, compare product locations to the planogram, determine the expiration date of products, determine freshness of products including produce, measure shelf height, shelf depth, shelf width and section width, recognize signage, detect promotional material, including displays, signage, and features and measure their bring up and down times, detect and recognize seasonal and promotional products and displays such as product islands and features, capture images of individual products and groups of products and fixtures such as entire aisles, shelf sections, specific products on an aisle, and product displays and islands, capture 360-deg and spherical views of the environment to be visualized in a virtual tour application allowing for virtual walk throughs, capture 3D images of the environment to be viewed in augmented or virtual reality, capture environmental conditions including ambient light levels, capture information about the environment including measuring space compliance with disability and safety standards and determining if light bulbs are off, provide a real-time video feed of the space to remote monitors, provide on-demand images and videos of specific locations, including in live or scheduled settings, and build a library of product images. 
     In one embodiment, the movable base can be a manually pushed or guidable cart. Alternatively, the movable base can be a tele-operated robot, or in preferred embodiments, an autonomous robot capable of guiding itself through a store or warehouse. Depending on size of the store or warehouse, multiple autonomous robots can be used. Aisles can be regularly inspected to identify out of stocks or create realograms, with aisles having high product movement or high value being inspected more often. 
     In another embodiment, an inventory monitoring method includes the steps of allowing an autonomous robot to move along an aisle that is lined with shelves capable of holding inventory or products, with the autonomous robot acting as a movable base for multiple cameras. Multiple cameras are directed toward inventory on the shelf lined aisle, with data derived at least in part from these cameras being used to construct a realogram of inventory or a panoramic image using a processing module contained in the autonomous robot. Realogram data or panoramic images created by the processing module can be transferred to remote locations using a communication module, and inventory information received via the communication module can be used to aid in realogram construction. 
     In yet another embodiment, an inventory monitoring method, includes the steps of allowing an autonomous robot to move along a shelf lined aisle holding inventory, with the autonomous robot acting as a movable base for multiple cameras. The autonomous robot can maintain a substantially constant or tightly controlled distance from the shelf lined aisle holding inventory while moving in a forward or reverse direction. Using the multiple cameras directed toward inventory on the shelf lined aisle, at least part of a realogram of inventory positioned along a shelf lined aisle holding inventory can be constructed. 
     Typically, the realogram is created and updated with a locally sited data storage and a processing module contained in the autonomous robot. To ensure complete or near complete camera coverage of shelf lined aisles, the autonomous robot can pause, reverse, or mark for further multiple camera inspection if data capture for a portion of the shelf lined aisle is incomplete. 
     To improve data handling speed and efficiency, use of various image processing techniques for handling product related data are possible. For example, an autonomous robot can be directed or allowed to move along the aisle comprising product, product labels, and shelf associated stock labels, with the autonomous robot acting as a movable base having multiple cameras for image capture, and depth sensors useful for detecting shelf edges. A first set of high-resolution images of an aisle comprising product, product labels, and shelf associated stock labels is captured. A second set of images derived from the first set of images and having a lower resolution than the first set of images is then created. Resolution is selected so that product images are viewable, and have sufficient details to allow for automated or manual identification of the products. A third set of images that are a subset of the first set of images is also preserved. This third set of images has a higher resolution than the second set of images, and resolution is selected so that product labels and shelf associated stock labels are readable by automated or manual systems. 
     Advantageously, the foregoing described method and various embodiments allows for greatly reduced data storage requirements. Instead of having to process high-resolution images, a lower resolution panorama can be analyzed. Human or machines can identify position of labels, and via a reverse mapping, the corresponding position of a label on the high-resolution image can be identified. Except for those portions of the high-resolution image showing a label, most of the high-resolution image can be discarded. Further processing on the limited image subset can be used to read the labels. Typically, this provides a ten-fold or greater data reduction for the high-resolution image. 
     In some embodiments, specialized cameras or procedures can be used to detect shelf labels, which often have bright bold colors designed to attract shoppers&#39; attention. For example, in one method a color Haar feature consistent with a shelf label and having a defined scale and location across at least some channels of a chosen color space can be evaluated. A feature vector having a feature value is assigned to the color Haar feature, and a color Haar classifier is generated to identify shelf labels using feature values of feature vectors. The color Haar classifier can be a boosted Haar cascade classifier. 
     Advantageously, the shelf label and the color Haar feature can both be rectangular, providing simple and fast label identification. In one embodiment, the chosen color space is selected to be device independent LAB, with an assigned feature value at a location equal to a sum of squares length of the feature vector with a sign given by a luminance (L) channel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a camera system mounted on a movable base to track product changes in aisle shelves or other suitable targets; 
         FIG. 2  is a cartoon illustrating two autonomous robots inspecting opposite shelves in an aisle; 
         FIG. 3  is an illustration of various systems and electronic modules connected to inventory cameras; 
         FIG. 4  is an illustration of steps in one embodiment of operation; 
         FIGS. 5A  and B are respectively examples in side view and cross section of an autonomous robot capable of acting as a mobile base for a camera system; and 
         FIG. 6  is a flowchart  600  illustrating in more detail how a product space for a realogram can be created without requiring an initial planogram; 
         FIG. 7  is a flow chart  700  illustrating a method for data efficient processing; 
         FIG. 8  is a flow chart  800  illustrating another method for data efficient processing; 
         FIG. 9  is a flow chart  900  illustrating another method for data efficient processing using shelf edge detection with depth sensors; 
         FIG. 10  is a flow chart  1000  illustrating a method for reading bar codes; 
         FIG. 11  is a cartoon illustrating various store aisle product images; 
         FIG. 12  is a cartoon illustrating a shelf edge having an attached shelf label; 
         FIG. 13  is a flowchart for training a color Haar classifier suitable for identifying shelf labels; and 
         FIG. 14  is a flow chart illustrating use of a trained Haar classifier. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is an illustration of an inventory monitoring camera system  100  mounted on a movable base  110  (with drive wheels  114 ) to track product changes in aisle shelves or other targets  102  without requiring an initial planogram. 
     The movable base  110  can be an autonomous robot having a navigation and object detection sensor suite  130  that is capable of independently navigating and moving throughout a building. The autonomous robot has multiple cameras  140  attached to movable base  110  by a vertically extending camera support  140 . Lights  150  are positioned to direct light toward target  102 . The object sensing suite includes forward ( 133 ), side ( 134  and  135 ), top ( 132 ) and/or rear (not shown) image and depth sensors to aid in object detection, localization, and navigation. Additional sensors such as laser ranging units  136  and  138  (and respective laser scanning beams  137  and  139 ) also form a part of the sensor suite that is useful for accurate distance determination. In certain embodiments, image sensors can be depth sensors that infer depth from radar, stereo images, project an infrared mesh overlay that allows rough determination of object distance in an image, or that infer depth from the time of flight of light reflecting off the target. In other embodiments, simple cameras and various image processing algorithms for identifying object position and location can be used. For selected applications, ultrasonic sensors, radar systems, magnetometers or the like can be used to aid in navigation. In still other embodiments, sensors capable of detecting electromagnetic, light, or other location beacons can be useful for precise positioning of the autonomous robot. 
     As seen in  FIG. 1 , various representative camera types useful for constructing an updatable realogram are shown. As previously noted, a realogram can use camera derived images to produce an updateable map of product or inventory position. Typically, one or more shelf units (e.g. target  102 ) would be imaged by a diverse set of camera types, including downwardly ( 142  and  144 ) or upwardly ( 143  and  148 ) fixed focal length cameras that cover a defined field less than the whole of a target shelf unit; a variable focus camera that adapts its focus to the distance from the imaged target; a wide field camera  145  to provide greater photographic coverage than the fixed focal length cameras; and a narrow field, zoomable telephoto  146  to capture bar codes, product identification numbers, and shelf labels. Alternatively, a high-resolution, tilt controllable, height adjustable camera can be used to identify shelf labels. These camera  140  derived images can be stitched together, with products in the images identified, and position determined. 
     To simplify image processing and provide accurate results, the multiple cameras are typically positioned a set distance from the shelves during the inspection process. The shelves can be illuminated with LED or other directable lights  150  positioned on or near the cameras. The multiple cameras can be linearly mounted in vertical, horizontal, or other suitable orientation on a camera support. In some embodiments, to reduce costs, multiple cameras are fixedly mounted on a camera support. Such cameras can be arranged to point upward, downward, or level with respect to the camera support and the shelves. This advantageously permits a reduction in glare from products having highly reflective surfaces, since multiple cameras pointed in slightly different directions can result in at least one image with little or no glare. 
     Electronic control unit  120  contains an autonomous robot sensing and navigation control module  124  that manages robot responses. Robot position localization may utilize external markers and fiducials, or rely solely on localization information provided by robot-mounted sensors. Sensors for position determination include previously noted imaging, optical, ultrasonic sonar, radar, Lidar, Time of Flight, structured light, or other means of measuring distance between the robot and the environment, or incremental distance traveled by the mobile base, using techniques that include but are not limited to triangulation, visual flow, visual odometry and wheel odometry. 
     Electronic control unit  120  also provides image processing using a camera control and data processing module  122 . Autonomous robot sensing and navigation control module  124  manages robot responses, and communication module  126  manages data input and output. The camera control and data processing module  122  can include a separate data storage module  123  (e.g. solid state hard drives) connected to a processing module  125 . The communication module  126  is connected to the processing module  125  to transfer realogram data or panoramic images to remote locations, including store servers or other supported camera systems, and additionally receive inventory information to aid in realogram construction. In certain embodiments, realogram data is primarily stored and images are processed within the autonomous robot. Advantageously, this reduces data transfer requirements, and permits operation even when local or cloud servers are not available. 
       FIG. 2  is a cartoon  200  illustrating two autonomous robots  230  and  232 , similar to that discussed with respect to  FIG. 1 , inspecting opposite shelves  202  in an aisle. As shown each robot follows path  205  along the length of an aisle, with multiple cameras capturing images of the shelves  202 . 
     In some embodiments, the robots  230  and  232  support at least one range finding sensor to measure distance between the multiple cameras and the shelves and products on shelves, with an accuracy of less than 5 cm, and with a typical accuracy range between about 5 cm and 1 mm. As will be appreciated, LIDAR or other range sensing instruments with similar accuracy can also be used in selected applications. Using absolute location sensors, relative distance measurements to the shelves, triangulation to a known landmark, conventional simultaneous localization and mapping (SLAM) methodologies, or relying on beacons positioned at known locations in a blueprint or a previously built map, the robots  230  and  232  can move along a path generally parallel to shelves  202 . As the robots move, vertically positioned cameras are synchronized to simultaneously capture images of the shelves  202 . In certain embodiments, a depth map of the shelves and products is created by measuring distances from the shelf cameras to the shelves and products over the length of the shelving unit using depth sensors and or laser ranging instrumentation. The depth map is registered onto the images captured by the shelf cameras, so as the location of each pixel on target can be estimated in 3D. Using available information, consecutive images can be stitched together to create panoramic images that spans an entire shelving unit. The consecutive images can be first stitched vertically among all the cameras, and then horizontally and incrementally stitched with each new consecutive set of vertical images as the robots  230  and  232  move along an aisle. 
       FIG. 3  is an illustration of various systems and electronic modules  300  supported by an autonomous robot having robot navigation and sensing  310 . Inventory cameras  340  are moved into a desired position with the aid of robot navigation and sensing module  310 . Lights  350  are directed toward product inventory and inventory camera control and image reconstruction  312  takes a series of inventory photos (and optional depth measurements) that can be stitched together to help form or update a realogram. Panoramic images, realogram data, or other inventory related information is handled by an inventory data and local update module  314 , which can transmit or receive relevant information via communication system  316 . Data can be communicated to a server local to the store, or transmitted by suitable internet or networking devices to remote servers or cloud accessible data sites. 
     Inventory cameras  340  can include one or more movable cameras, zoom cameras, focusable cameras, wide-field cameras, infrared cameras, ultra-violet cameras, or other specialty cameras to aid in product identification or image construction. For example, a wide-field camera can be used to create an image organizing template into which data from higher resolution cameras with a narrow field of view are mapped or registered. As another example, a tilt controllable, high-resolution camera positioned on the camera support roughly at a height of a shelf lip can be used to read shelf attached bar codes, identifying numbers, or labels. In certain embodiments, conventional RGB CMOS or CCD sensors can be used, alone or in combination with spectral filters that may include narrowband, wideband, or polarization filters. Embodiments can also include sensors capable of detecting infrared, ultraviolet, or other wavelengths to allow for hyperspectral image processing. This can allow, for example, monitoring and tracking of markers, labels or guides that are not visible to people, or using flashing light in the invisible spectrum that do not induce discomfort or health risk while reducing energy consumption and motion blur. 
     Lights can be mounted along with, or separately from, the sensors, and can include monochromatic or near monochromatic light sources such as lasers, light emitting diodes (LEDs), or organic light emitting diodes (OLEDs). Broadband light sources may be provided by multiple LEDs of varying wavelength (including infrared or ultraviolet LEDs), halogen lamps or other suitable conventional light source. Various spectral filters that may include narrowband, wideband, or polarization filters and light shields, lenses, mirrors, reflective surfaces, diffusers, concentrators, or other optics can provide wide light beams for area illumination or tightly focused beams for improved local illumination intensity. 
     According to some embodiments, both cameras  340  and lights  350  can be movably mounted. For example, hinged, rail, electromagnetic piston, or other suitable actuating mechanisms used to programmatically rotate, elevate, depress, oscillate, or laterally or vertically reposition cameras or lights. 
     In still other embodiments, one or more of the cameras can be mounted in such a way as to take advantage of the rolling shutter effects and direction of travel of the autonomous robot. Aligning a camera in such a way as to take advantage of the “rasterized” delay of the rolling shutter can reduce artifacts (elongation/shortening) that can occur while the robot is traveling in its path. 
     Inventory data  314  can include but is not limited to an inventory database capable of storing data on a plurality of products, each product associated with a product type, product dimensions, a product 3D model, one or more product images and a current product price, shelf location, shelf inventory count and number of facings. Realograms captured and created at different times can be stored, and data analysis used to improve estimates of product availability. In certain embodiments, frequency of realogram creation can be increased or reduced. 
     The communication system  316  can include connections to either a wired or wireless connect subsystem for interaction with devices such as servers, desktop computers, laptops, tablets, or smart phones. Data and control signals can be received, generated, or transported between varieties of external data sources, including wireless networks, personal area networks, cellular networks, the Internet, or cloud mediated data sources. In addition, sources of local data (e.g. a hard drive, solid state drive, flash memory, or any other suitable memory, including dynamic memory, such as SRAM or DRAM) that can allow for local data storage of user-specified preferences or protocols. In one particular embodiment, multiple communication systems can be provided. For example, a direct Wi-Fi connection (802.11b/g/n) can be used as well as a separate 4G cellular connection. 
     Remote server  318  can include, but is not limited to servers, desktop computers, laptops, tablets, or smart phones. Remote server embodiments may also be implemented in cloud computing environments. Cloud computing may be defined as a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned via virtualization and released with minimal management effort or service provider interaction, and then scaled accordingly. A cloud model can be composed of various characteristics (e.g., on-demand self-service, broad network access, resource pooling, rapid elasticity, measured service, etc.), service models (e.g., Software as a Service (“SaaS”), Platform as a Service (“PaaS”), Infrastructure as a Service (“IaaS”), and deployment models (e.g., private cloud, community cloud, public cloud, hybrid cloud, etc.). 
       FIG. 4  is an illustration of realogram or panorama updating steps in one embodiment of operation. As seen in flow chart  400 , a robot moves to an identified position and proceeds along an aisle path at a predetermined distance (step  410 ). If the path is blocked by people or objects, the robot can wait till the path is unobstructed, begin movement and slow down, wait as it nears the obstruction, move along the path until required to divert around the object before reacquiring the path, or simply select an alternative aisle. 
     In step  412 , multiple images are captured and stitched together to define an image panorama. Optionally, in certain embodiments a panoramic or widefield camera can capture a single large image. These images, along with optional depth information created by a laser ranging system, an infrared depth sensor, or similar system capable of distinguishing depth at a decimeter or less scale, are used to create either panorama or a realogram (step  414 ). This information is communicated to a cloud or remote server (step  416 ) to create, change, or update a panorama and/or realogram with data derived from shelf labels, bar codes, and product identification databases to identify products. A realogram is created using panorama images and data, and can be used by, for example, store managers, stocking employees, or customer assistant representatives to localize product and label placement, estimate product count, count the number of product facings, or even identify or locate missing products. Additionally, in some embodiments, realogram or other information received from other robots, from updated product databases, or from other stores can be used to update or assist in the creation of subsequent realograms (step  418 ). 
       FIGS. 5A  and B are respectively examples in side view and cross section of an autonomous robot  500  capable of acting as a mobile base for a camera system in accordance with this disclosure. The robot navigation and sensing unit includes a top mount sensor module  510  with a number of forward, side, rear, and top mounted cameras. A vertically aligned array of lights  520  is sited next to a vertically arranged line of cameras  530 , and both are supported by a drive base  540  that includes control electronics, power, and docking interconnects. Mobility is provided by drive wheels  560 , and stability is improved by caster wheels  550 . 
     Inventory monitoring can rely on use of autonomous robot camera system images. Typically, multiple images are processed, combined, and segmented for further analysis. Segmented images can assist in defining a product bounding box that putatively identifies a product facing. This information is often necessary to develop a product library. A segmented image can include multiple product bounding boxes, typically ranging from dozens to hundreds of outlined or distinct image areas. The bounding boxes can surround either product facings, groups of products, or gaps between products. Products within product bounding boxes can be manually identified, identified using crowd source or paid reviewer image identification systems, identified with or without the aid of an initial planogram, or automatically identified using various image classifiers discussed herein. Gaps between products are useful for identifying shelf spacings, product separation, or missing/absent inventory. 
     Automatic identification can be performed using an autonomous robot, alone or in combination with an external image classifier system. In certain embodiments, a product bounding box can be defined as the horizontal space on the shelf occupied by one or more copies (facings) of the same product, along with the vertical space spanning the distance between a current shelf and the shelf above it. When the current shelf is the top shelf, the vertical space is a number generally corresponding to the distance to top of the fixture. The vertical space can alternatively be top of the product as sensed by depth sensors. 
     Image segmentation to automatically assist in creation of product bounding boxes and product identification can rely on use of image templates in some embodiments. Typically, each image template is compared with the image captured by a camera system mounted on an autonomous robot. If a match is positive, the matched section of the image is used as the image segmentation for that product 
     Segmentation can be improved by training classifiers on annotated training data sets, where bounding boxes are manually drawn around products. Training can be performed with supervised or unsupervised machine learning, deep learning, or hybrid machine and deep learning techniques, including but not limited to convolutional neural networks. 
     When a segmented product is identified, the real dimensions of the product are compared to the apparent dimensions of the product in the image to extract a distance estimate between the imaging sensor and the product. Additionally, the apparent position of the product in the image combined with the distance estimate enable the computation of the three-dimensional position and orientation between the imaging sensor and the product. 
     In yet another embodiment, methods that extract topological shelf positions for each product from the planogram can be utilized. 
     In other embodiments, RFID tags, wireless beacons, locators, or trackers can be used alone or in combination to assist in defining a product bounding box. For example, in some embodiments, an autonomous robot can be additionally equipped with one or more RFID readers. Performing an inventory count of products equipped with RFID tags can proceed in one embodiment as follows:
         The total number of tags for each product is communicated by an inventory management software to an RFID reader mounted on or associated with an autonomous robot;   The RFID reader collects RFID tags while the autonomous robot is either stationary or moving;   If the RFID reader does not collect all the tags for a given product, and:
           i) If the autonomous robot is moving, then the autonomous robot stops in an attempt to collect the remaining tags, or   ii) If the autonomous robot is stopped, move the autonomous robot in a predetermined search path in an attempt to collect the remaining tags.
 
With suitable changes, Bluetooth, Near Field Communication, or other conventional wireless system can be used in place of RFID systems.
   
               

     In some embodiments, visual images based on numeric, alphabetic, one or two-dimensional bar codes, or similar image based shelf or product labels can be used alone or in combination with various image features to segment images and assist in defining a product bounding box. Each shelf image can be analyzed and segmented to detect individual price tags or product labels on the shelf. Alternatively, or in addition, each image can be used to detect identifying indicia of individual products and product packages. Segmentation can use techniques that include but are not limited to:
         Edge detection;   Depth estimation using depth estimation techniques that include but are not limited to:
           1. Stereo camera   2. Structure from motion   3. Structure from focus   4. Depth camera using time of flight   5. Depth camera using triangulation   6. Planar or 3D laser/lidar scanner   
           Color segmentation;   Product features including but not limited to product shapes, colors, texts, and aspect ratios;   Product shapes identified and learned using machine learning techniques such as convolutional neural networks and deep learning   Association of individual product images to identifiers based on a location heuristic. The heuristic may locate the identifier below a product image or in another proximal location.       

     The heuristic may be informed from the planogram by correlating the planned location of labels to the measured location of labels, and the number of facings for each facing group with the measured distance between consecutive labels divided by the width of the product corresponding to the left label. These correlations can be optimized, for example by using graph theory approaches, to generate a maximum likelihood correspondence between a facing group and a label. 
     Association may also be informed by mapping the left most label on a shelf with the left most group of self-similar facings, the right most label on the same shelf with the right most label facing group, and working inward until every facing group has an associated label. 
     Further, association may be informed by classifiers trained on hand-annotated associations from training data sets and using heuristics similar to the ones described above. Some methods further include inferring the position of each identifier on the shelf by comparing the location of the identifier to the location of the beginning or end of the shelf on which the identifier is placed. Alternatively, methods can be based on inferring the position of each product on the shelf by comparing the location of the product to the location of the beginning or end of the shelf on which the product is placed. 
     In some methods, an identifier&#39;s shelf location and/or product location are expressed in metric terms, i.e. measured distance from the beginning or end of a specific shelf. In other methods, an identifier&#39;s shelf location and/or product location are expressed topologically, e.g. as a sequence of identifiers from the start or the end of a specific shelf, and from the bottom of a shelf to the top, or from top to bottom. For example, a specific identifier may be third from the start of the fourth shelf. 
     If a product library or classifier is created or made available, the products within the library can be indexed for improved searching performance and/or reduced storage requirements. Indexing methods include but are not limited to: hashing techniques, tree representations, and bag-of-words encodings. Alternatively, planogram information or product location information from the product library can be used to reduce the number of products that must be searched or use a classifier scoped to just those products contained within the imaged shelf. In still other variations, identified products can be verified by segmenting and decoding the price tag or product label located proximally to each identified product. 
       FIG. 6  is a flowchart  600  illustrating in more detail one example of how a product bounding box such as previously discussed can be created from information captured by sensor and camera system supported by an autonomous robot. Turning to  FIG. 6 , in a first step  610 , shelf labels are detected either in individual shelf images, or in a stitched panorama. Classification algorithms such as convolution neural networks or other deep learning methods, template matching or HAAR cascades can be used to aid in detection of each shelf label. Each shelf label is analyzed to obtain one or more product identifiers. Analysis may include but is not limited to optical character recognition, bar code scanning, QR code scanning, AR code scanning, or hologram code scanning. Product identifiers may be UPC code, the product name, or a coded collection of letters, numbers, or other symbols. If more than one identifier is available, a preferred identifier such as the UPC code can be selected. In certain embodiments, infrared or ultraviolet detectable product identifiers embedded on product packaging or shelf labels can be used, as well as any other suitable tag, marker, or detectable identifying indicia such as a visible UPC code or serial number on the product packaging. 
     In optional step  612 , an image location of the shelf label is registered or compared to a depth map to recover its 3D location in space. The depth map can be created by use of one or more depth sensors that infer depth from stereo images, project an infrared mesh overlay that allows rough determination of object distance in an image, infer depth from the time of flight of scanning lasers or LEDs reflecting off the target, a radar, or any other suitable method for building a depth map typically having sub-millimeter to sub-centimeter resolution. 
     In step  614  a bounding box is defined as a perimeter enclosing one or multiple facings of the same product, or any space on the shelf including but not limited a gap between products. The bounding box can be manually defined, or automatically defined using training classifiers, deep learning, image segmentation, or any other suitable technique or combination of techniques. A bounding box can be created with reference to labels grouped by height, with a horizontal distance between adjacent labels used to define the width of the bounding box for single facing products. For multiple facing products, the bounding box width is subdivided in sections equal to the product width. 
     The height of the bounding box can be derived from the detection of shelf heights. Shelf heights can be detected by analyzing the depth map to identify horizontal indentations corresponding to the distance between the bottom of a shelf and products stacked below it. These horizontal indentations correspond to shelf lips and measure shelf height. 
     Alternatively, label groups can be filtered by horizontal span (defined as the horizontal distance between the first and last label of the group) according the following criteria: 
     i) A label group passes the filter if its horizontal span overlaps with the current label group span. 
     ii) A label group passes the filter if its horizontal span is distant from the current label group span by no more than a number representing a bay width. Generally, bay widths are standard three or four-foot-wide shelves used throughout a store. 
     iii) Order filtered label groups by height and select the label group that is next highest after the current label group. 
     Alternatively, shelf heights can also be detected by deep learning classifiers trained on manually annotated color and depth images (if available) of the shelves. 
     The height of the bounding box can be fully defined once the height difference between the selected label group and the current label group is determined. 
     For vertically stacked products, the height of the bounding box is subdivided in sections equal to the height of the product. 
     In certain embodiments, the previous method for determining the bounding box can be probabilistically combined through estimating a confidence measure for each method and adding their results. 
     Next, in step  616 , each bounding box is consistently associated with an identifier based on a label location heuristic. The identifier can be selected to originate from either the left or the right shelf label. The association of bounding boxes and identifier can further be refined through optimization across an entire shelf section or aisle. The bounding box, with identifiers, can be registered to a simple or panoramic stitched image of the shelf, and image descriptors extracted for the portion of the image contained in the bounding box. Methods for generating image descriptors include but are not limited to: image templates, Histogram of Gradients, Histogram of Colors, the Scale Invariant Feature Transform, Binary Robust Independent Elementary Features, Maximally Stable Extremal Regions, Binary Robust Invariant Scalable Keypoints, Fast Retina Keypoints, Kaze features, and variations thereof. 
     An alternative to extracting product descriptors is to use the bounding boxes as labeled categories and train classifiers on the images contained in the bounding boxes. Classifiers may include those based on deep structured learning, hierarchical learning, deep machine learning, or other suitable deep learning algorithms associated with convolutional, feedforward, recurrent, or other suitable neural network. A deep learning based classifier can automatically learn image descriptors based on an annotated training data. For example, deep learning based image descriptors can be hierarchical, corresponding to multiple layers in deep convolutional neural networks. The final layer of a convolutional layer network outputs the confidence values of the product being in one of the designated image categories. The image descriptor generator part and the classification part get integrated in a convolutional neural network and these two parts are trained together using a training set. 
     Alternatively, or in addition, embodiments that use both deep learning based image descriptors and conventional image descriptors can be combined in a hybrid system. 
     In step  618 , the image descriptors can be classified and labelled with the identifier. Classification algorithms that can include but are not limited to support vector machine. This process can be repeated for every image of the bounding box associated to the same identifier, whether the image is captured in the same store at different times, or in different stores. In time, this allows automatically building a product library (i.e. the “Library of Products”), without requiring an initial planogram or storage of specific product databases. 
     For those embodiments utilizing deep learning based image descriptors, the neural network classifier can be part of the same trained convolutional neural network. The automatically learned features, which are extracted from different layers of the convolutional neural network, can be used in a larger product recognition system. These features can be used in conjunction with other classifiers or with conventional image descriptors in a hybrid system. 
     For many applications, product and product label identification require more sophisticated processing steps to meet conditions related to available time, limited local memory, and data transfer to cloud limitations. For example, in a typical store aisle product monitoring application, a single aisle may require 4000 high-resolution pictures to be combined into one or more panoramas. Each panorama must be created in the space of seconds, and can require the processing of gigabytes of information at a time. Hundreds or thousands of products need identification, and critical data must be transmitted to local or cloud servers in a matter of minutes. Methods are needed to improve data handling efficiency by reducing gigabytes of raw image data to megabytes of useful data, using onboard RAM and a limited number of costly solid state flash memory systems. 
       FIG. 7  illustrates one embodiment of data efficient, inventory monitoring method  700  useful in conjunction with the previously described autonomous robots. Typically, an autonomous robot is directed or allowed to move along the aisle comprising product, product labels, and shelf associated stock labels, with the autonomous robot acting as a movable base having multiple cameras for image capture, and depth sensors useful for detecting shelf edges. In step  710 , a first set of images of an aisle comprising product, product labels, and shelf associated stock labels is captured. In step  714 , a second set of images derived from the first set of images and having a lower resolution than the first set of images is created. Resolution is selected so that product images are viewable, and have sufficient details to allow for automated or manual identification of the products. In step  716 , a third set of images that are a subset of the first set of images is preserved. This third set of images has a higher resolution than the second set of images, and resolution is selected so that product labels and shelf associated stock labels are readable by automated or manual systems. 
     In some embodiments, position of product labels and shelf associated stock labels can be detected from the second set of images, while content of product labels and shelf associated stock labels is read using the third set of images. Advantageously, memory requirements can be greatly reduced by discarding the first set of images after creating the second and third set of images. In other embodiments, memory and processing requirements can be reduced by creating a panoramic image from the resolution reduced second set of images, rather than the original high-resolution images. In still other embodiments, either or both of the second and third set of images can be sent to cloud storage for automated or manual analysis. In yet another embodiment, stitching the second image set, detecting product labels and reading their content in RAM memory can be completed before an image is discarded, saved to solid state disk, or communicated to an external cloud server. 
     Local (on the autonomous robot) or remote (e.g. external cloud) analysis can include automated or manual definition of one or more bounding boxes around product labels and shelf associated stock labels to identify respective position in the second and first set of images. Bounding boxes can be associated to products as previously discussed with respect to  FIG. 6 . 
     In other embodiments of the method described with respect to  FIG. 7 , product labels and shelf associated stock labels can be automatically or manually detected and read. In some embodiments, position and content of shelf associated stock labels can be maintained in a data history to improve future identification efforts. Labels can include, but are not limited to one or two-dimensional bar codes or watermarks. 
     Accurate detection of shelf associated stock labels is necessary for utilizing the described method of  FIG. 7 . In one embodiment, position of shelf associated stock labels can be identified through characteristic color discontinuity between the labels and the shelf edges. Alternatively, or in addition, position of shelf associated stock labels can be detected by background subtraction or edge discontinuity. More sophisticated position identifying methods using machine intelligence or neural network methods can involve detection with classifiers trained on shelf associated stock labels, or use of Haar classifiers trained on shelf associated stock labels. These detection efforts can optionally include a data history of label position and content. 
     For some applications, shelf associated stock labels may not be available. This is particularly true for inventory stored on a top shelf, or temporary displays or product positioned away from the shelf on endcaps or in standalone displays. In this situation, high-resolution images of shelf inventory not having shelf associated stock labels is captured, and product identification occurs using only the product image. Typically, high-resolution images can capture bar codes, product names, or other identifiers printed and visible on the product box or container. 
       FIG. 8  illustrates another embodiment of an inventory monitoring method  800  useful in conjunction with the previously described autonomous robots. High-resolution source images of an aisle comprising product, product labels, and shelf associated stock labels are captured in a first step  810 . In step  814  a low-resolution panoramic image is created from the high-resolution source images. In step  816 , shelf associated stock labels in the low-resolution panoramic image are detected. In step  818 , position of product labels or shelf associated stock labels in the panoramic image is mapped to corresponding position in the high-resolution source images. This permits, in step  820 , reading product labels or shelf associated stock labels directly using the high-resolution source images, or from images derived from the high-resolution source images. In some embodiments, the step of creating a low-resolution panoramic image from the high-resolution source images further includes combining at least multiple adjacent pixels (e.g. two pixels) into a single pixel, allowing reverse addressing to map position of product labels or shelf associated stock labels. 
     Speedy identification of shelf edges that support shelf labels is useful. As disclosed with respect to  FIG. 9 , an alternative inventory monitoring method  900  can include a step  910  of capturing high-resolution source images of an aisle comprising product, product labels, and shelf associated stock labels. In step  912 , a low-resolution panoramic image from the high-resolution source images is created. In step  914 , location of shelf edges having attached shelf associated stock labels is detected, and least in part using depth sensors. In step  916 , shelf associated stock labels are detected using at least one of depth sensors and the low-resolution panoramic image. Finally, in step  918  the shelf associated stock labels are read using at least one of high-resolution source images or intermediate resolution images derived from the high-resolution source images and having a resolution greater than the low-resolution panoramic image. In some embodiments, location of shelf edges having attached shelf associated stock labels can be determined at least in part using previously detected location history. In other embodiments, location of shelf edges having attached shelf associated stock labels is determined using previously detected location history, with areas marked for subsequent detection if shelf edge location is not confirmed. 
     In some embodiments, both the image processing steps of capturing high-resolution source images of an aisle comprising product, product labels, and shelf associated stock labels; and creating a low-resolution panoramic image from the high-resolution source images; are performed in memory before an image is saved to disk or external cloud. In other embodiments, the step of reading shelf associated stock labels is performed in memory before an image is saved to disk, external cloud, or discarded. 
       FIG. 10  is a flowchart  1000  relating to an inventory monitoring method. In step  1010 , an autonomous robot having a camera system and a separate data analysis system is provided. In step  1012 , images are captured with a camera having associated data processing capability. In step  1014 , one or two dimensional bar codes are detected in the captured images. In step  1016   m  bar code identity, bar code location, and compressed images are transferred to the separate data analysis system. In some embodiments, the data analysis system provides the camera having associated data processing capability with shelf edge location information. This allows the camera to transfer uncompressed images corresponding to shelf edge location back to the separate data analysis system. In other embodiments, the camera can take a first image having a region of interest corresponding to shelf edge location, with the region of interest being transferred in uncompressed form back to the separate data analysis system. This allows the camera to take a second image that is compressed before transfer to the separate data analysis system. 
       FIG. 11  is a cartoon illustrating image compression techniques in accordance with the previously described methods. Images  1100  can include product, product labels, and shelf associated stock labels. A series of high-resolution images  1110  can be combined into a low-resolution panorama  1112 . Resolution of the panorama is selected to be sufficient for various product or label identification tasks, including human or machine identification of labels with bounding boxes. By reverse mapping, identified labels (for example) in the panorama can be mapped to the originating high-resolution image  1110 , and stored for further processing as image  1114 . The high-resolution images  1110  can then be deleted, with further human or machine processing using only the reduce data from panorama  1112  and label images  1114 . 
       FIG. 12  is a cartoon  1200  illustrating a shelf edge  1202  having an attached shelf label  1204 . Typically, the shelf label  1204  is positioned below, above or near identified products, and can provide a buyer with product identification, product information including name, weight or volume, and pricing information. One-dimensional (as shown), two-dimensional, three-dimensional or watermark bar codes can be used to provide electronically accessible information in conjunction with a smartphone or dedicated bar code reader. The shelf label is commonly rectangular in shape, can be colored or shaded to contrast with the shelf edge, and can also be associated with transparent shelf label holders (not shown) that have a distinctive appearance. During a detection phase, a camera, optionally supported by an autonomous robot, and moving in direction  1206  is used to photograph the shelf label. Using techniques described below, the shelf label  1204  is detected, and optionally marked with a bounding box  1208  for additional processing/reading or manual review. 
     In one embodiment, detection of shelf labels is done using Haar classifiers that identify Haar features. A simple rectangular Haar feature can be defined as the difference of the sum of pixels of areas inside the rectangle, which can be at any position and scale within the original image. This modified feature set is typically a 2-, 3-, or 4-rectangle feature. Detected values indicate characteristics of a subset of the image. Each feature type can indicate the existence (or absence) of certain characteristics in the image, such as edges or changes in color. For example, a 2-rectangle feature can indicate where the border lies between a dark region and a light region. In a detection phase, a window of a target size is moved over the input image, and for each subsection of the image the Haar feature is calculated. This difference is then compared to a learned threshold that separates non-shelf labels from shelf labels. Advantageously, Haar feature identification supports a high calculation speed. Due to the use of integral images, a Haar-like feature of any size can be calculated in constant time (typically less than 100 microprocessor instructions for a 2-rectangle feature). 
     In one embodiment a Haar feature value can be calculated using the sums of squares of the components of the feature vector. Even though this operation can result in loss of information since multiple feature vectors can result in same feature value, the training time is significantly lower and allows for faster deployment of label detectors. In other embodiments, a chosen color space is LAB and an assigned feature value at a location is a sum of squares length of the feature vector with a sign given by a luminance (L) channel. Alternatively, the feature vectors can be kept as-is and boosting could directly be done in the higher dimensional (equal to that of the color space) feature vector space as described with respect to the following disclosure. 
     To improve performance, the Haar shelf label detector can be organized into a classifier cascade to form a strong learner or classifier. This classifier cascade can include several simpler classifiers (stages) that are applied to a region of interest until at some stage the candidate is rejected, or all the stages are passed. Additional techniques such as “boosted” classifiers built out of basic classifiers using different boosting techniques (i.e. weighted voting) can also be used. Well known boosting procedures include Discrete Adaboost, Real Adaboost, Gentle Adaboost and Logitboost. 
     To train a single Haar classifier or a cascade of boosted Haar classifiers working together, a few hundred positive examples of a shelf labels scaled to the same size are provided, along with a lesser number of arbitrary images of the same size to act as negative examples. After a classifier is trained, it can be applied to a region of interest in an input image. The classifier outputs a “1” if the region is likely to show the shelf label, and “0” otherwise. To search for the shelf label in the whole image, a search window is moved across the image and checked with the Haar classifier. 
       FIG. 13  is a flowchart  1300  for training a color Haar classifier suitable for identifying shelf labels. Initially, in step  1310  one or more color Haar features consistent with a shelf label and having a defined scale and location across at least some channels of a chosen color space are determined. A color space can be LAB, RGB, or any other suitable color space. A feature vector having a feature value is assigned to the color Haar feature in step  1312 . A color Haar classifier, classifier cascade, or boosted classifier cascade can be used to identify shelf labels using feature values of the feature vectors in step  1314 . 
       FIG. 14  is a flowchart  1400  illustrating use of a trained Haar classifier such as discussed with respect to  FIG. 13 . In In step  1410 , an autonomous robot having a camera system and a separate data analysis system is provided. In step  1412 , images are captured with a camera having associated data processing capability. In step  1416 , using a generated color Haar classifier, shelf labels are identified using feature values of feature vectors. Optionally, in step  1416 , a bounding box can be defined around identified shelf labels to simplify machine reading or manual review. For example, machine review could involve reading a bar code, or reading textual information including product name or number or price. If the image is not sufficiently clear, the bounding box can be flagged. The autonomous robot can be tasked to take another image, or manual intervention can be requested to identify the shelf label by inspection of the image or in-store review. 
     Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims. It is also understood that other embodiments of this invention may be practiced in the absence of an element/step not specifically disclosed herein.