Alan P. Pritchard

Design and fabrication progress in BAe's high-complexity resistor-array IR scene projector devices

Developments are described in the design and manufacture of full 512 X 512 infra-red scene projector (IRSP) systems, as well as in a high complexity demonstrator program to realize 1024 X 1024 complexity. Design aspects include choice of drive circuit, the suspended resistor pixel design factors, the choice of busbar configurations, and the optimization of emissivity coatings. Design of the peripheral drive systems for the 512 system is outlined, and progress on manufacture reported. Development plans for the provision of suitable high complexity computer scene generation is outlined.

Practical application of a 1:1 mapped NUC system for IRSP arrays

The 1:1 projector:NUC sensor mapping system reported in 1999 showed that small sub-arrays of projector pixels could be corrected to a fine degree. This system has been developed to join together sub-arrays and complete the NUC operation on a whole resistor array in service. Outline detail is given of the general principle of the correction, the methods involved, covering merging of sub-arrays, strategies for dead pixels and the application of corrections in real time, together with comment on the measurement time and performance against specification.

Output accuracy and resolution limitations in resistor array infrared scene projection systems

There is a growing demand for high complexity infra-red scene projector devices with improved output accuracy and resolution. Sources of inaccuracies and limitations to resolution are discussed for both projector-alone and projector-in-simulation situations. Using experience of existing system design and performance, an attempt has been made to assign realistic percentage inaccuracy figures to the various relevant effects so that a perspective can be gained of their relative importance. Schemes for improving the accuracy and resolution performance are considered, both in terms of system techniques and array device design. A revised order of relative importance is presented to assess the residual accuracy perspective after application of practicable corrective measures. We conclude that the absolute accuracy to which a unit- under-tests collected input can be relied upon under all conditions is only 90 - 95%. However, it is essential to cater for a much finer output resolution than would be deciduate by the absolute accuracy figure, although it seems doubtful that the requirements of 12 bit resolution could be obtained except in very restricted simulation/scene conditions.

Performance characteristics of a 256 x 256 suspended resistor infrared scene generator system

A 256 X 256 suspended resistor infrared scene generator system is being constructed. The system consists of a high technology core device which generates the infrared radiation and three conventional technology peripheral subsystems. At the time of writing, measurements have been made of the critical core device component parts, i.e., the transistor drive backplane and the suspended resistor superstructure separately, measurements of the complete integrated system have yet to be completed. Measurements of performance are presented and brief subsystem descriptions are included to aid in understanding of the overall system.

Bragg gratings interrogating system using MEMS and optical circuits

It is well documented that optical sensors offer many advantages over conventional electronic devices for some applications because they are more versatile,lighter,smaller,immune to electrical interference and can be densely multiplexed. However, to date, many optical sensor instrument systems have been insufficiently robust for use in harsh environments and relatively expensive due to the use of discrete optical components. Hence the primary aim of this work is to develop a physically robust and cost effective interrogation system for fibre Bragg grating strain sensors by integrating a system on a silicon chip. Therefore it will be possible to replace many of the costly discrete components. Related improvements will be the reduction of size and weight,an increase in robustness, and performance in relatively harsh environments. This work will focus on the development of a Micro Electro Mechanical System (MEMS) tunable Fabry-Perot optical filter, together with integrated optical circuit fabricated on silicon-on-insulator (SOI) to deliver the signal to the Bragg gratings and to detectors based in the same optical circuit. In this paper we discuss the requirements for integration, as well as reviewing the principles of strain measurement using fibre Bragg gratings. The latter will include a brief discussion of the merits of multiplexing via single or multiple fibres.

Refinements in practical accuracy factors for resistor-array IR scene projectors

We describe incremental improvements in measurement, understanding and control of sensor-perceived scene accuracy factors for BAe resistor-array IR scene projector devices by means of system and device design, analysis and measurement methodology. Progress has been made in the areas of fill- factor measurement, aliasing effects, dead pixel statistics, image spreading, the design of non-uniformity correction (NUC) systems, busbar robbing, heatsink effects and noise sources.

Practical accuracy factors in resistor-array infrared scene projector systems

This is the second in a series of papers describing an on- going investigation into the detailed performance of our resistor array infra-red scene projector devices and systems. The purpose is to extract understanding and information which will enable validation of simulations involving the systems, and design compromises to be resolved. Following last years conclusions, the importance of Non Uniformity Correction is reinforced and the concept of Local Step Error and its importance is developed and investigated practically. A test methodology is developed, and the first steps in practical measurements are reported.

Developments in the use and design of a suspended resistor IR scene projector technology

This paper describes two aspects of work carried out at British Aerospace on a family of suspended resistor infrared scene generators intended as sources for exercising infrared seeker systems in simulation environments. In the first aspect, a 256 X 256 system has matured and entered service with hardware-in-the-loop (HWIL) simulation facilities. This system, designated TPS4 (for thermal picture synthesizer) has performance suitable for air target tracking studies, and certain aspects of its characteristics in use are described. In the second aspect, research work has been carried out on the extension of the system performance to enable the representation of higher temperature targets, such as are required for countermeasures work. These improved devices are designated TPS5, and aspects of their rationale, design, and evaluation are described. Prototype arrays suitable for eventual systems of complexity 512 X 512 and beyond have been tested.

Design and fabrication concepts for a 1024 x 1024-pixel IR scene projector array

We are currently undertaking a design and development phase for the 1024 X 1024 complexity level of infra-red scene projectors based on the emitter resistor array principle. Our approach is based as for previous complexities, on commercially available CMOS with the addition of a custom suspended resistor pixel technology applied monolithically in our own facility. We have adopted the philosophy of continuing to develop the emitter pixel technology, whilst investigating CMOS design concepts, but delaying the detail- design and procurement of the CMOS until a firm commitment to build emerges, so as to allow maximum progress in the CMOS technologies available.

Developments in the design and performance of IR scene projector devices at BAE Systems

The status of development of resistor-array infra-red scene projector devices at BAE SYSTEMS is that two variants of a 512 X 512 array have each been brought to a second development stage, whilst work on higher complexity arrays is slow but purposeful. In this paper we describe the latest features of the 512 arrays, exhibiting on the one hand high fidelity performance through a ballast-load configuration, and on the other hand very high apparent temperature output, coupled with high speed performance. For higher complexity arrays we describe some of the system philosophy and preliminary design work.