• Journal of the Korean Society for Precision Engineering
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• v.12 no.4
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• pp.78-87
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• 1995

Specular reflection appears with metals, plastics, glasses and many other solid objects which are required to be inspected, assembled, moved, or processed automatically. Recongnizing such shiny objects with specular reflections is a hard problem for computer vision, since specular reflections appear, disappear, or change their shapes abruptly, due to tiny movements of the view. Traditionally, such specular reflections are discarded as annoying noise for recongnition purposes. In this paper a technique is represented for obtaining shapes of specular objects. The ring illumin- ation system employes a ring source which is positioned on the axis of the camera. The concept of the proposed method is that if specular objects are illuminated by the ring they show their own dis- tinctive specularity features in surface from which we can infer the shape of the object. A series of experiments are performed to evaluate the performance of this system.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.379-382
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• 1997

This paper introduces a new vision technique for extracting roof edges of polyhedra having specularly reflecting surfaces. There have been many previous works on object recognition using edge information. But they can not be applied to specular objects since it is hard to acquire reliable camera images of specular objects. If there is a method which can extract the edges of specular objects, it is possible to apply edge-based recognition algorithms to specular objects. To acquire the reliable edge images of specular objects, scanned double pass retroreflection method is proposed, whose main physical characteristic is curvature-sensitive. This utility of the physical characteristic is motivated by the idea that roof edges can be characterized as local surfaces of high curvature. In this paper, the optical characteristics of double pass retroreflection are discussed and a series of simulation studies are performed to verify and analyze the sensor characteristics. The results from a series of simulations show the effectiveness of the proposed method.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.11
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• pp.64-72
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• 1996

This paper is aimed to develop an optical method for measuring 3-dimensional shapes of specular objects having curved surfaces. The existing methods measuring the shapes of specular objects have several common disadvantages: they may not work properly if the surface is highly specular like mirror surface or if the reflectance property is not uniform over the surface. And, they often require the a priori knowledege about the surface reflectance. To overcome these disadvantages, the measurement using double pass retroreflection method is proposed in this paper. For this measurement principle, an experimental measuring system is designed and prepared which is composed of a galvanometer scanner, a beam splitter, a laser source, a CCD camera, and a reflector made of retroreflective material. To verify the effectiveness of the measurement system a series of experiments are performaed for various specular objects. The results observed from the experiments show that the developed optical sensing system can be an effective mean of measuring the 3-D shapes of specular objects.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1758-1763
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• 1991

This paper describes a new method to determine the 3D-shape of objects consisting of specular planar surfaces. This method exploits a light source which is made of a diffuse plane with a grid pattern encoded in an M-sequence and uses a single image of the light source reflected by the objects to acquiring orientations and positions of the surfaces of the objects. When grid lines of the light source are reflected by a specular planar surface and perspectively projected on an image plane, a set of lines vanishing at a point are obtained on the image plane. The orientation of the specular planar surface is determined by using the vanishing point, and the position is determined by using the correspondence between lines on the image and lines on the light source, which is obtained by employing a characteristic regularity of the M-sequence. Before the vanishing points are calculated, the lines on the image are classified and correlated with the surfaces of objects by using slopes and positions of the lines and the regularity of the M-sequence. This method requires only a single image.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.93-96
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• 1996

Structured laser light is a widely used method for obtaining 3D range information in Machine Vision. However, The structured laser light method is based on assumption that the surface of objects is Lambertian. When the observed surfaces are highly specularly reflective, the laser light can be detected in various parts on the image due to a specular reflection and secondary reflection. This makes wrong range data and the image sensor unusable for the specular objects. To discriminate wrong range data from obtained image data, we have proposed a new algorithm by using the cross section of image block. To show the performance of the proposed method, a series of experiments was, carried out on: the simple geometric shaped objects. The proposed method shows a dramatic improvement of 3D range data better than the typical structured laser light method.

• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.107-108
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• 2008

• The Transactions of the Korea Information Processing Society
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• v.4 no.4
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• pp.1132-1140
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• 1997

In many vision tasks of the major obstacles is the specular highkight of smoth objects, which causes a misinterpretation of objects.This paper presents an dffcient algorithm for highight detection and object reconstruction, blsed on the theory of photometric stereo in which the location of highilight changes as the position of illumination source changes.Two images, referred to as base image and reference image.are sequentially taken with two different positionhs of the two images.The difference image is thresholded to detct the specular spike of the highlight.Then the specu-lar lobe around the specular spike is detected to reconstruct the object.The proposed algorithm can be applied to metals and dielectrics, regardlless of the surface chracteristics.This method can also be aplied to the case when the background is brighter than the object.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.106-112
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• 1993

A new model for the construction of a sonar map in a specular environment has been developed ad implemented. In a real world where most of the object surfaces are specular ones, a sonar sensor suffers from a multipath effect which results in a wrong interpretation of an objects's location. To reduce this effect and hence to construct a reliable map of a robot's surroundings, a probabilistic approach based on Bayesian reasoning is adopted to both evaluation of object orientations and estimation of an occupancy probability of a cell by an object. The usefulness of this approach is illustrated with the results produced by our mobile robot equipped with ultrasonic sensors.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.600-602
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• 2005

Recently image display devices have become large and high quality. To control the qualities of the component, measurements of the shape and thickness of a plate glass has been required. In order to measure the shape of the specular objects, Non-Contact Optical Sensor using Hologram laser unit was proposed. The sensor has a optical system that is composed of a Hologram laser and objective lens used for CD Player, and the sensor showed high performance for measuring the shape and thickness of transparent plates. In the sensor, the temperature of the sensor body is controlled by TEC(Thermoelectric Cooler). In this paper, we proposed the measuring method to make better performance of sensor using focus error signal of a hologram laser unit. It can measure the shape and the thickness of transparent objects with the s-type focus error signal which is generated by the sensor while it goes to the object.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.675-683
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• 1992

Mapping and navigation system based on certainty grids for an autonomous mobile robt operating in unknown and unstructured environment is described. The system uses sonar range data to build a map of robot's surroundings. The range data from sonar sensor are integrated into a probability map that is composed of two dimensional grids which contain the probabilities of being occupied by the objects in the environment. A Bayesian model is used to estimate the uncertainty of the sensor information and to update the existing probability map with new range data. The resulting two dimensional map is used for path planning and navigation. In this paper, the Bayesian updating model which was successfully simulated in our earlier work is implemented on a mobile robot and is shown to be valid in the real world through experiment. This paper also proposes a technique for reducing for reducing specular reflection problem of sonar system which seriousely deteriorates the map quality, and a new path planning method based on weighted distance, which enables the robot to efficiently navigate in an unknown area.