Ming Chih Lu

Image-based distance and area measuring systems

In this paper, a novel measuring system using a scan-counter method via a CCD camera is proposed. The proposed measuring system is an easy-to-construct system to measure the distance between a CCD camera and an object, and to measure the projected area of the object. This measuring method needs not store huge amounts of image data nor use any pattern recognition approach. It quickly obtains the distance and the projected area using simple circuits and formulas. For distance measurement, two laser projectors are set on either side of a CCD camera and produce two parallel rays that project two bright spots on the object and, therefore, on the CCD. An external clock, which is generated by an extra oscillator, is used to measure the time interval between the two bright spots as the CCD scans the image. A circuit for counting the number of external clock pulses between the two bright spots is employed to calculate the interval between them in the video image. Due to the parallel setup of the distance measuring system, there is a linear relationship between the actual distance and the interval of the two bright spots. Therefore, the actual distance from the CCD camera to the object can be calculated from a simple formula. For area measurement, circuits count the number of external clock pulses of the horizontal scan lines covering the projected area of the object. Then, the projected area of the object is calculated from simple algebraic formulas. Finally, several experimental results demonstrate the effectiveness of the proposed system.

Distance measurement based on pixel variation of CCD images

This paper presents a distance measurement method based on pixel number variation of CCD images by referencing to two arbitrarily designated points in the image frames. By establishing a relationship between the displacement of the camera movement along the photographing direction and the difference in pixel count between reference points in the images, the distance from an object can be calculated via the proposed method. To integrate the measuring functions into digital cameras, a circuit design implementing the proposed measuring system in selecting reference points, measuring distance, and displaying measurement results on CCD panel of the digital camera is proposed in this paper. In comparison to pattern recognition or image analysis methods, the proposed measuring approach is simple and straightforward for practical implementation into digital cameras. To validate the performance of the proposed method, measurement results using the proposed method and ultrasonic rangefinders are also presented in this paper.

Image-based height measuring systems for liquid or particles in tanks

In this paper, an image-based height measuring system for liquid or particulate material, which does not use pixels to measure distance, is proposed to measure the material height inside of a storage tank. Two laser projectors, fixed on a base, define a vertical plane to produce two projected bright spots on the surface of the material in the tank. A timer, instead of pixel counter, for measuring distance and a circuit for counting the number of clock pulses between the two bright spots are employed to calculate the distance between the two projected bright spots in the video images. Since the two laser projectors form an isosceles triangle, there is a simple relationship between the actual measured height and the distance of the two bright spots. The actual height of liquid in the tank can be calculated from a simple formula. One does not have to use a expensive high speed DSP microprocessor to identify the bright spots, but just use a simple voltage comparator to identify them. Experimental results have demonstrated the effectiveness of the proposed system.

Nighttime Vehicle Distance Measuring Systems

In this brief, a nighttime vehicle distance measuring system using charge-coupled device (CCD) cameras is proposed. The authors use the proportionality of similar triangles to measure the distance between a CCD camera and taillights of a vehicle in front. At night, the taillights form two bright spots in the CCD image, therefore producing two measurable signals. A circuit for counting the number of external clock pulses between the two bright spots is employed to calculate the interval between them in the video image. Due to the proportionality of similar triangles, there is a linear relationship between the actual distance and the interval of the two taillights. Thus, the actual distance from the CCD camera to the vehicle can be calculated from a simple formula. One does not have to use an expensive high-speed digital signal processing microprocessor to identify the taillights of the vehicle or use pixels to measure distance, but just use simple circuits to identify the taillights at night and use a simple formula to measure distance. Experimental results demonstrate the effectiveness of the proposed system

Distance and angle measurement of distant objects on an oblique plane based on pixel variation of CCD image

This paper presents an image-based system for measuring target objects on an oblique plane based on pixel number variation of charge-coupled device images for digital cameras by referencing to two arbitrarily designated points in the image frame. Based on an established relationship between the displacement of the camera movement along the photographing direction and the variation in pixel counts between the reference points in the images, photographic distance and incline angle for objects lying on an oblique plane can be calculated via the proposed method. As a real-case application of the proposed approach, 2-D localization of target objects in robot soccer competitions is also demonstrated to show the effectiveness of the proposed approach. To allow the use of widely available digital zoom cameras for ranging and localization by the proposed method, a parameter equivalent to the displacement due to the camera movement is also investigated and derived in this paper.

A practical nighttime vehicle distance alarm system

This paper presents a practical nighttime vehicle distance measuring method based on a single CCD image. The method combines an image-based distance measuring system. To solve the nighttime feature extraction problem, the proposed method uses two taillights as the feature. Based on the proportionality of similar triangles, distance between a CCD camera and the taillights of the vehicle ahead can be measured. The method focuses on detecting the taillights and differentiating the targeted vehicle from others on the basis of partial image analysis instead of whole image processing. The system is both fast and simple. The accuracy of the proposed method is demonstrated in this paper through experiences.

Image-Based System for Measuring Objects on an Oblique Plane and Its Applications in 2-D Localization

This paper presents an image-based framework for measuring target objects on an oblique plane by using a single charge-coupled device camera and two laser projectors mounted in parallel beside the camera. Because of the alignment of the laser beams, which form in parallel with the optical axis of the camera, laser-projected spots in the image can be processed to establish relationships between distance and pixel counts of the projected spots in the image. Based on simple geometrical derivations without complex image processing, the proposed approach can successfully measure the photographic distance, the distance between two arbitrary points on the oblique surface, and the incline angle of the oblique surface. Thanks to its ranging capability, the proposed image-based measuring system is further applied to localize objects on a ground surface in addition to depth measurement. To demonstrate the feasibility of the proposed approach for practical applications, we propose a surveillance framework under which a pan-tilt-zoom camera tracks objects in an environment according to the 2-D localization results obtained via the proposed method. Experimental results have demonstrated the effectiveness of the proposed approach in distance measurement, as well as localization of objects on an oblique plane.

Optimal path planning incorporating global and local search for mobile robots

This paper proposes an optimal path planning algorithm incorporating a global and local search mechanism for mobile robots. The global path planning is based on Voronoi graph to establish a backbone path for the map with significantly reduced nodes for the original grid map. With the use of the backbone path, the D* algorithm is adopted to determine a shortest path between the starting and end points. Taking advantages of the D* algorithm and Voronoi graph, the proposed optimal path planning algorithm is capable of obtaining a desired path for the mobile robot, overcoming the efficiency problem while maintaining maximum safety distance from the obstacles when the mobile robot navigates in the environment. Simulation results have confirmed the feasibility of the proposed algorithm for practical use in the real-world environment.

Hybrid Path Planning Incorporating Global and Local Search for Mobile Robot

This paper proposes a hybrid path planning algorithm incorporating a global and local search mechanism for mobile robot. The global path planning is based on Voronoi graph to establish a backbone path for the map with significantly reduced nodes for the original grid map. With the use of the backbone path, the D* algorithm is adopted to determine a shortest path between the starting and end points. Taking advantages of the D* algorithm and Voronoi graph, the proposed hybrid path planning algorithm is capable of obtaining a desired path for the mobile robot, overcoming the efficiency problem while maintaining maximum safety distance from the obstacles when the mobile robot navigates in the environment.

An image-based area measurement system

A novel image-based area measurement system is proposed in this paper, we can convert the pixels of object into real area by image processes. No matter the system is vertical to the measuring plane or not and the height of system, it could calculates arbitrary two points on the image convert into the actual distance. This paper proposed a new structure for achieve our goal, there are four laser projects and camera fixed on same base, then generate four laser spots on the object or measurement plant, and assume connect each two laser spots as parallel lines, finally it could simulated a ruler in the image. Without consider photography angle for this system, it can measure area of floor or height of building.