Malcolm I. Heywood

UV microstereolithography system that uses spatial light modulator technology

A new stereophotolithography technique utilizing a spatial light modulator (SLM) to create three-dimensional components with a planar, layer-by-layer process of exposure is described. With this procedure it is possible to build components with dimensions in the range of 50 mum-50 mm and feature sizes as small as 5 mum with a resolution of 1 mum. A polysilicon thin-film twisted nematic SVGA SLM is used as the dynamic photolithographic mask. The system consists of eight elements: a UV laser light source, an optical shutter, beam-conditioning optics, a SLM, a multielement reduction lens system, a high-resolution translation stage, a control system, and a computer-aided-design system. Each of these system components is briefly described. In addition, the optical characteristics of commercially available UV curable resins are investigated with nondegenerate four-wave mixing. Holographic gratings were written at a wavelength of 351.1 nm and read at 632.8 nm to compare the reactivity, curing speed, shrinkage, and resolution of the resins. These experiments were carried out to prove the suitability of these photopolymerization systems for microstereolithography.

Implementation and performance considerations of hybrid digital/optical correlator configurations

Two-dimensional correlation between a reference template and an input scene is a powerful pattern recognition technique but is demanding of computational power. Coherent optical correlators, exploiting the Fourier transforming properties of a lens and the capability to impart a phase modulation on a wavefront with an appropriate spatial light modulator (SLM), hold the promise of real-time implementation of two- dimensional correlation for realistic pattern recognition problems. However, their practical use has been delayed in many applications by the lack of availability of suitable SLM devices with the required speed and dynamic range, with different needs for input and frequency plane modulators. It is now possible to compute a two-dimensional Fourier transform at video-rates with various digital signal processing chip sets. Thus a hybrid correlator is proposed in which the input scene is digitally Fourier transformed at video-rate, and multiple templates searched during the next video frame interval by optical mixing and Fourier transformation at a speed at least two orders of magnitude faster than possible with digital methods. In this way, the input SLM is avoided and a precise spectrum is available for subsequent digital or optical mixing with the stored templates. The speed advantage over all-digital processing allows unconstrained pattern recognition problems to be tackled that require many template searches to match the input with a reference function. Different hybrid correlator configurations are considered, together with discussion of the various digital chip sets available to perform the video-rate FFT, as well as the SLM devices currently available that are suitable as frequency domain phase modulators.

Batch process control using QFD matrices and simulation

An intuitive method for providing decision support of production control activities is proposed in which qualitative management information is represented by way of Quality Function Deployment matrices, while quantitative information is collected in the form of a simulation model of the plant. The quantitative-to-qualitative transform is provided by way ofgoal programming and fuzzy decision rules-where the latter naturally complements the symbolic method of representing information.

Systems control for a micro-stereolithography prototype

Abstract The system control of a micro-stereolithographic fabrication system is detailed, with specific attention given to the opto-electronic and electro-mechanical interfaces. The application of the National Instrument LabVEIW© environment is demonstrated to provide a good basis for rapid application development of the necessary control structures. In particular, this provides the basis for a highly flexible control system, typical activities of which include: low-level interface formats; icon-based systems design; and support for good human–computer interfacing. The resulting system has the capability to provide two orders of magnitude improvement above that currently available.

Four-wave mixing studies of UV curable resins for microstereolithography

Abstract The optical characteristics of three commercial UV curable resins are investigated using non-degenerate four-wave mixing. The materials assessed are an acrylate and two epoxy resins. The holographic gratings were written at a wavelength of λ = 351.1 nm for an irradiance range 0.5–3.0 W/cm 2 and read at λ = 632.8 nm in order to compare the reactivity, curing speed, shrinkage and resolution of the resins. These experiments were carried out to prove the suitability of the photopolymerisation systems for microstereolithography.

Application of Stochastic Real-Valued Reinforcement Neural Networks to Batch Production Rescheduling

Abstract This paper details the design and application of a hybrid neural network architecture for the rescheduling problem of batch manufacture. Design issues include the selection of an appropriate neural network paradigm, specification of the network architecture and support for multistep prediction. Application issues include decoupling the network dimension from that of the problem and the definition of suitable rescheduling operators. The ensuing hybrid network is tested against heuristics previously identified as typically representing estimates for best and worst case performance within a cross-section of batch rescheduling problems.

HOLOGRAPHIC CHARACTERIZATION OF EPOXY RESINS AT 351.1 NM

The optical characteristics of two commercially available UV curable epoxy resins are investigated using nondegenerate four-wave mixing. The materials assessed are optimized for use with a UV argonion laser. The holographic gratings were written at a wavelength of ? 5351.1 nm for an irradiance range 0.5 to 3.0 W/cm2 and read at ? 5632.8 nm to compare the reactivity, curing speed, shrinkage, and resolution of the resins. These experiments were carried out to prove the suitability of the photopolymerization systems for microstereolithography.

Real-Time Digital-Optical Correlator Systems Design

The systems design of a real-time hybrid digital-optical correlator is analyzed based on partitioning of the digital and optical systems such that the efficiency of the optical image train is maximized. The parallelization of tasks within the digital sub-system is to maximize throughput. The significance of communication bottlenecks are emphasized in the digital system and the constraints enforces on the initial selection of digital signal processing devices.

Feasibility of a Computer Downtime Recording System

This paper describes the development of a computerised downtime recording system for an automotive assembly plant. It introduces the nature of the recording system environment at a large commercial van assembly plant and describes the system developed in terms of, characteristics and usability. The application analysis focuses on the user-computer interface.

Possibilistic Framework for MFM Modelling and Verification

Abstract A framework for implementing Means-end Flow modelling (MFM) using a possibilistic reasoning paradigm is introduced. The possibilistic context means that the degree of reliability associated with the system state is quantified, and support for tracking temporal evaluation of fault conditions is implicitly available. Specifically two central contributions are made. Firstly, we demonstrate how the MFM methodology in conjunction with a Focusing Expert system framework provides the basis for an intuitive FDI architecture. Secondly, a formal basis is provided for deriving the sub-graphs representing deviation from the normative state such that robust sensor validation is possible.