Remote distance estimation system and method

[0001] This application claims the benefit of the provisional patent application Ser. No. 62/208,791 filed Aug. 23, 2015 by the present inventors.

[0002] This disclosure relates to remote distance estimation systems.

[0003] Mobile robotic devices are being used more and more frequently in a variety of industries for executing different tasks with minimal or no human interactions. Such devices rely on various sensors to navigate through their environment and avoid driving into obstacles.

[0004] Infrared sensors, sonar and laser range finders are some of the sensors used in mobile robotic devices. Infrared sensors typically have a low resolution and are very sensitive to sunlight. Infrared sensors that use a binary output can determine whether an object is within a certain range, but are unable to accurately determine the distance to the object. Sonar systems rely on ultrasonic waves instead of light. Under optimal conditions, sonar systems can be very accurate, however, sonar systems have limited coverage areas; if used in an array, they can produce cross-talk and false readings; if they are installed too close to the ground, signals can bounce off the ground, degrading accuracy; and sound-absorbing materials in the area can produce erroneous readings.

[0005] Laser Distance Sensors (LDS) are a very accurate method for measuring distance that can be used on robotic devices, but, due to their complexity and cost, these sensors are typically not a suitable option for robotic devices intended for day-to-day home use. These systems generally use two types of measurement methods: Time-of-Flight (ToF) and Triangulation. In ToF methods, the distance of an object is calculated based on the round trip of the emission and reception of a signal. In Triangulation methods, there is a source and a sensor on the device with a fixed baseline. The emitting source emits the laser beam at a certain angle. When the sensor receives the beam, the sensor calculates the degree at which the beam entered the sensor. Using those variables, the distance traveled by the laser beam may be calculated with triangulation.

[0006] A need exists for a more accurate and reliable, yet affordable method for automatic remote distance measuring.

[0007] The following presents a simplified summary of some embodiments of the invention in order to provide a basic understanding of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some embodiments of the invention in a simplified form as a prelude to the more detailed description that is presented below.

[0008] The present invention introduces new method and system for distance estimation. This invention presents a distance estimation system comprising a laser light emitter disposed on a baseplate emitting a collimated laser beam which projects a light point onto surfaces opposite the emitter; two image sensors disposed symmetrically on the baseplate on either side of the laser light emitter at a slight inward angle towards the laser light emitter so that their fields of view overlap while capturing the projections made by the laser light emitter; an image processor to determine an estimated distance from the baseplate to the surface on which the laser light beam is projected using the images captured simultaneously and iteratively by the two image sensors. Each image taken by the two image sensors shows the field of view including the point illuminated by the collimated laser beam. At each discrete time interval, the image pairs are overlaid and the distance between the light points is analyzed by the image processor. This distance is then compared to a preconfigured table that relates distances between light points with distances from the baseplate to the projection surface to find the actual distance to the projection surface.

[0009] In some embodiments the assembly may be mounted on a rotatable base so that distances to surfaces may be analyzed in any direction. In some embodiments, the image sensors capture the images of the projected laser light emissions and processes the image. Using computer vision technology, the distances between light points is extracted and the distances may be analyzed.

[0016] The present invention will now be described in detail with reference to a few embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention.

[0017] Various embodiments are described hereinbelow, including methods and techniques. It should be kept in mind that the invention might also cover articles of manufacture that includes a computer readable medium on which computer-readable instructions for carrying out embodiments of the inventive technique are stored. The computer readable medium may include, for example, semiconductor, magnetic, opto-magnetic, optical, or other forms of computer readable medium for storing computer readable code. Further, the invention may also cover apparatuses for practicing embodiments of the invention. Such apparatus may include circuits, dedicated and/or programmable, to carry out tasks pertaining to embodiments of the invention. Examples of such apparatus include a general-purpose computer and/or a dedicated computing device when appropriately programmed and may include a combination of a computer/computing device and dedicated/programmable circuits adapted for the various tasks pertaining to embodiments of the invention. The disclosure described herein is directed generally to one or more processor-automated methods and/or systems that estimate distance of a device with an object also known as distance estimation systems.

[0018] This invention presents a distance estimation system comprising: a laser light emitter disposed on a baseplate emitting a collimated laser beam creating an illuminated area hereinafter referred to as a light point or projected light point on surfaces that are substantially opposite the emitter; two image sensors disposed on the baseplate, positioned at a slight inward angle with respect to the laser light emitter so that the fields of view of the two image sensors overlap and capture the projected light point within a predetermined range of distances, the image sensors simultaneously and iteratively capturing images; an image processor overlaying the images taken by the two image sensors to produce a superimposed image showing the light points from both images in a single image; extracting a distance between the light points in the superimposed image; and, comparing the distance to figures in a preconfigured table that relates distances between light points with distances between the baseplate and surfaces upon which the light point is projection (which may be referred to as ‘projection surfaces’ herein) to find an estimated distance between the baseplate and the projection surface at the time the images of the light point were captured.

[0019] The preconfigured table is constructed from actual measurements of distances between the light points in superimposed images at increments in a predetermined range of distances between the baseplate and the projection surface.

[0020] Each image taken by the two image sensors shows the field of view including the light point created by the collimated laser beam. At each discrete time interval, the image pairs are overlaid creating a superimposed image showing the light point as it is viewed by each image sensor. Because the image sensors are at different locations, the light point will appear at a different spot within the image frame in the two images. Thus, when the images are overlaid, the resulting superimposed image will show two light points until such a time as the light points coincide. The distance between the light points is extracted by the image processor using computer vision technology, or any other type of technology known in the art. This distance is then compared to figures in a preconfigured table that relates distances between light points with distances between the baseplate and projection surfaces to find an estimated distance between the baseplate and the projection surface at the time that the images were captured.

[0021] Referring to FIG. 1A, a front elevation view of distance estimation system 100 is illustrated. Distance estimation system 100 is comprised of baseplate 101, left image sensor 102, right image sensor 103, laser light emitter 104, and image processor 105. The image sensors are positioned with a slight inward angle with respect to the laser light emitter. This angle causes the fields of view of the image sensors to overlap. The positioning of the image sensors is also such that the fields of view of both image sensors will capture laser projections of the laser light emitter within a predetermined range of distances. Referring to FIG. 1B, an overhead view of remote estimation device 100 is illustrated. Remote estimation device 100 is comprised of baseplate 101, image sensors 102 103, laser light emitter 104, and image processor 105.

[0022] Referring to FIG. 2, an overhead view of the remote estimation device and fields of view of the image sensors is illustrated. Laser light emitter 104 is disposed on baseplate 101 and emits collimated laser light beam 200. Image processor 105 is located within baseplate 101. Area 201 and 202 together represent the field of view of image sensor 102. Dashed line 205 represents the outer limit of the field of view of image sensor 102. (It should be noted that this outer limit would continue on linearly, but has been cropped to fit on the drawing page.) Area 203 and 202 together represent the field of view of image sensor 103. Dashed line 206 represents the outer limit of the field of view of image sensor 103. (It should be noted that this outer limit would continue on linearly, but has been cropped to fit on the drawing page.) Area 202 is the area where the fields of view of both image sensors overlap. Line 204 represents the projection surface. That is, the surface onto which the laser light beam is projected.

[0023] The image sensors simultaneously and iteratively capture images at discrete time intervals. Referring to FIG. 3A, the image captured by left image sensor 102 (in FIG. 2) is illustrated. Rectangle 300 represents the field of view of image sensor 102. Point 301 represents the light point projected by laser beam emitter 104 as viewed by image sensor 102. Referring to FIG. 3B, the image captured by right image sensor 103 (in FIG. 2) is illustrated. Rectangle 302 represents the field of view of image sensor 103. Point 303 represents the light point projected by laser beam emitter 104 as viewed by image sensor 102. As the distance of the baseplate to projection surfaces increases, light points 301 and 303 in each field of view will appear further and further toward the outer limits of each field of view, shown respectively in FIG. 2 as dashed lines 205 and 206. Thus, when two images captured at the same time are overlaid, the distance between the two points will increase as distance to the projection surface increases.

[0024] Referring to FIG. 4, the two images from FIG. 3A and FIG. 3B are shown overlaid. Point 301 is located a distance 304 from point 303. The image processor 105 (in FIG. 1A) extracts this distance. The distance 304 is then compared to figures in a preconfigured table that co-relates distances between light points in the system with distances between the baseplate and projection surfaces to find an estimate of the actual distance from the baseplate to the projection surface upon which the images of the laser light projection were captured.

[0025] In some embodiments, the distance estimation device further includes a band-pass filter to limit the allowable light.

[0026] In some embodiments, the baseplate and components thereof are mounted on a rotatable base so that distances may be estimated in 360 degrees of a plane.