Seung-Hae Baek

An Error Correcting 3D Scanning Technique Using Dual Pseudorandom Arrays

Designing a low cost structured light system which can acquire 3D data in real time with great accuracy is still an ongoing topic among computer vision community as it is hard to achieve all these features together. Among various structured light systems, pseudorandom array is the most suitable technique for real time 3D reconstruction as it tends to concentrate the entire coding scheme in a single pattern. But it has the difficulty of decoding the pattern when it loses few pattern symbols. In this paper, we address this problem by introducing an error correcting 3D scanning technique. This technique consists of a two way decoding method which can decode a dual pseudorandom array and a hole-filling algorithm. In the experimental results, we show that our 3D scanning technique largely improves the reconstruction compared to the conventional methods.

A 3-D tube scanning technique based on axis and center alignment of multi-laser triangulation

This paper presents a novel 3D tube scanning technique based on a multi-laser triangulation. A multi-laser and camera module, which will be mounted in front of a mobile robot, captures a sequence of 360 degree shapes of the inner surface of a cylindrical tube. In each scan of the sequence, a circular shape, which is composed of four partial ellipses, is reconstructed from a multilaser triangulation technique. To reconstruct a complete shape of the tube, the center and axis of the circular shape in each scan are aligned to a common tube model. To overcome inherent alignment noises due to off-axis robot motion, sensor vibration, and etc., we derive and apply a 3D Euclidean transformation matrix in each scan. In experimental results, we show that the proposed technique reconstructs very accurate 3D shapes of a tube even though there is motion vibration.

An Efficient Calibration Method for a Stereo Camera System with Heterogeneous Lenses Using an Embedded Checkerboard Pattern

We present two simple approaches to calibrate a stereo camera setup with heterogeneous lenses: a wide-angle fish-eye lens and a narrow-angle lens in left and right sides, respectively. Instead of using a conventional black-white checkerboard pattern, we design an embedded checkerboard pattern by combining two differently colored patterns. In both approaches, we split the captured stereo images into RGB channels and extract R and inverted G channels from left and right camera images, respectively. In our first approach, we consider the checkerboard pattern as the world coordinate system and calculate left and right transformation matrices corresponding to it. We use these two transformation matrices to estimate the relative pose of the right camera by multiplying the inversed left transformation with the right. In the second approach, we calculate a planar homography transformation to identify common object points in left-right image pairs and treat them with the well-known Zhangs camera calibration method. We analyze the robustness of these two approaches by comparing reprojection errors and image rectification results. Experimental results show that the second method is more accurate than the first one.

Calibration of a Stereo Radiation Detection Camera Using Planar Homography

This paper proposes a calibration technique of a stereo gamma detection camera. Calibration of the internal and external parameters of a stereo vision camera is a well-known research problem in the computer vision society. However, few or no stereo calibration has been investigated in the radiation measurement research. Since no visual information can be obtained from a stereo radiation camera, it is impossible to use a general stereo calibration algorithm directly. In this paper, we develop a hybrid-type stereo system which is equipped with both radiation and vision cameras. To calibrate the stereo radiation cameras, stereo images of a calibration pattern captured from the vision cameras are transformed in the view of the radiation cameras. The homography transformation is calibrated based on the geometric relationship between visual and radiation camera coordinates. The accuracy of the stereo parameters of the radiation camera is analyzed by distance measurements to both visual light and gamma sources. The experimental results show that the measurement error is about 3%.

A Novel Stereo-radiation Detection Device Calibration Method using Planar Homography

A radiation detection device, also known as a particle detector, is a device used to detect, track and identify the presence of radiation sources within a given area or environment. In general, a stereo-radiation detection device consists with two radiation detection devices and used to estimate 3D distances to radiation sources accurately. In computer vision, device calibration is more important and to obtain accurate results using such devices, they have to be calibrated first. Many stereo camera calibration methods have been introduced throughout the last few decades but a proper stereo radiation device calibration method has not yet been introduced. In this work, we propose a new stereo-radiation detector calibration method using planar Homography. The calibrated devices are used to estimate 3D distances to radiation sources and we obtained very accurate results with an error of less than 6%.

Curved lane detection using robust feature extraction

In this paper, we propose a robust curved lane marking detection method by first detecting a straight lane and applying a geometric model of that detected straight lane. In our proposed method, we first detect the straight line and generate 13 candidates of the curved lane by applying a geometric model. We then vote those candidates on the feature image and consider the candidate which acquires the highest number of votes as the final curved lane. The performance and the efficiency of the proposed algorithm are confirmed by the experimental results.

A 3-D Tube Reconstruction based on Axis Alignment of Multiple Laser Scanning

A novel 3D tube scanning technique is proposed. The proposed tube scanning technique is developed for a special tube inspection module which consists of four line-lasers and one camera. Using the scanning module, we can reconstruct the 360 degree shapes of the inner surfaces of a cylindrical tube. From an image frame captured by the camera, we reconstruct a partial tube model based on four laser triangulations. Then by aligning such partial models with respect to a reference tube axis, a complete 3D shape of the tube is reconstructed. The tube axis in each reconstructed frame is aligned with a 3D Euclidean transformation to the reference axis. Several experiments show that the proposed method can align multiple tube axes very accurately and reconstruct 3D shapes of a tube with very low shape distortion.

Robust road line color recognition based on 2-dimensional S-color space

In this paper, we propose an illumination invariant lane color recognition method. Most of the conventional lane color recognition methods suffer from various illumination changes. In the past, the HSV color space has been commonly used to tell white and the yellow road lines, because the HSV color space is a range of specific colors. However, it is known that accurate road line recognition is difficult using the HSV space, because the road illumination is not static but always dynamic. In this paper, we propose a robust road line color recognition method by introducing a 2-dimensional S-color space. The white and yellow color features are clustered in the 2-D S-color space. The centroid of the feature samples in S-space is tracked continuously for real-time lane tracking.

Calibration of a Different Field-of-view Stereo Camera System using an Embedded Checkerboard Pattern.

Knowing the correct relative pose between cameras is considered as the first and foremost important step in a stereo camera system. It has been of the interest in many computer vision related experiments. Much work has been introduced for stereo systems with relatively common field-of-views; where a few number of advanced feature points-based methods have been presented for partially overlapping field-of-view systems. In this paper, we propose a new, yet simplified, method to calibrate a partially overlapping field-of-view heterogeneous stereo camera system using a specially designed embedded planar checkerboard pattern. The embedded pattern is a combination of two differently colored planar patterns with different checker sizes. The heterogeneous camera system comprises a lower focal length wide-angle camera and a higher focal length conventional narrow-angle camera. Relative pose between the cameras is calculated by multiplying transformation matrices. Our proposed method becomes a decent alternative to many advanced feature-based techniques. We show the robustness of our method through re-projection error and comparing point difference values in ’Y’ axis in image rectification results.

3D Visualization of Radioactive Sources by Combining Depth Maps Generated from a Stereo Radiation Detection Device

This paper proposes a simple, yet efficient, idea to visualize the shape and complete spatial distribution of radioactive sources. We used our previously studied gamma radiation detection device to capture stereo images of radioactive sources (using gamma camera) and 2D vision scanning environment (using vision camera). To generate a complete 3D model of radioactive sources and to see their distribution in the scanning area, we captured stereo images at different locations by freely moving the detector. We used the well-known Semi-global Block Matching algorithm to create both radiation and vision disparity images at each location and generated corresponding 3D reconstruction results by calculating depth values. Color ICP-based registration is performed on each individual reconstruction result to generate integrated 3D models for spatial area and radioactive sources, separately. These two integrated models are merged with each other to visualize the complete shape of radioactive sources and its distribution in the scanning environment. A graphical example is presented to show that the proposed method is capable of generating neat 3D models in real-time.