John L. Schneiter

An automated tactile sensing strategy for planar object recognition and localization

The planning problem associated with tactile exploration for object recognition and localization is addressed. Given that an object has been sensed and is one of a number of modeled objects, and given that the data obtained so far are insufficient for recognition and/or localization, the methods developed determin the paths along which a point contact sensor must be directed in order to obtain further highly diagnostic measurements. Three families of sensor paths are found. The first is the family of paths for which recognition and localization are guaranteed. The second guarantees only that something will be learned. The third represents paths to avoid because nothing new will be learned. The methods are based on a small but powerful set of geometric ideas and are developed for two-dimensional, planar-faced objects. They are conceptually easily generalized to handle three-dimensional objects, including objects with through holes. >

High-speed, high-resolution 3D range camera

There is a large class of machine vision inspection problems which requires detecting and characterizing voids in mostly diffuse materials. Typical examples include surface chips or gouges in ceramic parts, voids in powered metal components prior to sintering, and surface distress in construction and paving materials. There are two interrelated difficulties: achieving lighting which provides enough image contrast for reliable detection; developing image processing algorithms which can distinguish reliably between voids and image artifacts. The problems are particularly acute when inspecting composite materials containing dark inclusions which can be confused for voids, such as the aggregates in cementitious materials. We have examined this problem theoretically to understand the contrast-forming mechanisms. In this paper we present theoretical methods for modeling image contrast in images of small voids. We show how to use these methods to design appropriate illuminating systems and image processing algorithms. We validate the approach by comparing the theoretical results with experimental measurements. The prototype system we will discuss uses machine vision methods to measure air voids in cured and sectioned samples of portland cement concrete. These measurements allow estimation of air entrainment--a material property which, when properly controlled, can enhance the concretes ability to resist microcracking and structural deterioration during repeated cycles or freezing and thawing.

Reconfigurable laser ranging instrument

This paper describes the design and operation of a fast, flexible, non-contact, eye-safe laser ranging instrument useful in a variety of industrial metrology situations, such as in-process machining control and part inspection. The system has variable computer-controlled standoff and depth of field, and can obtain 3-D images of surfaces within a range of from 1.5 ft to almost 10 ft from the final optical element. The minimum depth of field is about 3.5 in. at 1.5 ft and about 26 in. at the far range. The largest depth of field for which useful data are available is about 41 in. Resolution, with appropriate averaging, is about one part in 4000 of the depth of field, which implies a best case resolution for this prototype of 0.00075 in. System flexibility is achieved by computer controlled relative positioning of optical components.