Engineering topics

Fisher, Timothy E.

Publications and source records attributed to Fisher, Timothy E..

13 records

NASA NTRS2011

Human Rating the Orion Parachute System

Human rating begins with design. Converging on the requirements and identifying the risks as early as possible in the design process is essential. Understanding of the interaction between the recovery system and the spacecraft will in large part dictate the achievable reliability of the final design. Component and complete system full-scale flight testing is critical to assure a realistic evaluation of the performance and reliability of the parachute system. However, because testing is so often difficult and expensive, comprehensive analysis of test results and correlation to accurate modeling completes the human rating process. The National Aeronautics and Space Administration (NASA) Orion program uses parachutes to stabilize and decelerate the Crew Exploration Vehicle (CEV) spacecraft during subsonic flight in order to deliver a safe water landing. This paper describes the approach that CEV Parachute Assembly System (CPAS) will take to human rate the parachute recovery system for the CEV.

Machin, Ricardo A.↗

NASA NTRS1993

Programmable Remapper with Single Flow Architecture

An apparatus for image processing comprising a camera for receiving an original visual image and transforming the original visual image into an analog image, a first converter for transforming the analog image of the camera to a digital image, a processor having a single flow architecture for receiving the digital image and producing, with a single algorithm, an output image, a second converter for transforming the digital image of the processor to an analog image, and a viewer for receiving the analog image, transforming the analog image into a transformed visual image for observing the transformations applied to the original visual image. The processor comprises one or more subprocessors for the parallel reception of a digital image for producing an output matrix of the transformed visual image. More particularly, the processor comprises a plurality of subprocessors for receiving in parallel and transforming the digital image for producing a matrix of the transformed visual image, and an output interface means for receiving the respective portions of the transformed visual image from the respective subprocessor for producing an output matrix of the transformed visual image.

Fisher, Timothy E.↗

NASA NTRS1992

Fast Pixel Buffer For Processing With Lookup Tables

Proposed scheme for buffering data on intensities of picture elements (pixels) of image increases rate or processing beyond that attainable when data read, one pixel at time, from main image memory. Scheme applied in design of specialized image-processing circuitry. Intended to optimize performance of processor in which electronic equivalent of address-lookup table used to address those pixels in main image memory required for processing.

Fisher, Timothy E.↗

NASA NTRS1992

A hybrid six degree-of-freedom tracking system

An optical/digital/mechanical six degree of freedom tracking system using an optical correlator for image processing is being constructed at NASA's Johnson Space Center. The degrees of freedom are expressed in sensor coordinates as azimuth, elevation, range, line-of-sight rotation, and the two out-of-plane object rotation angles. Hardware for an initial configuration has been assembled and various tracking algorithms and filtering techniques are being implemented and evaluated. The current correlator hardware is based on LCTV SLMs from a commercial television projector. Correlation peak detection and measurement are made using commercially available digital image processing boards. Out-of-plane object rotation, range, and line-of-sight rotation are tracked by various correlation filter techniques. Performance of the current system is presented, as are plans for future configurations.

Monroe, Stanley E., Jr.↗

NASA NTRS1991

Improved Remapping Processor For Digital Imagery

Proposed digital image processor improved version of Programmable Remapper, which performs geometric and radiometric transformations on digital images. Features include overlapping and variably sized preimages. Overcomes some of limitations of image-warping circuit boards implementing only those geometric tranformations expressible in terms of polynomials of limited order. Also overcomes limitations of existing Programmable Remapper and made to perform transformations at video rate.

Fisher, Timothy E.↗

NASA NTRS1991

A binocular stereo approach to AR/C at the Johnson Space Center

Automated Rendezvous and Capture requires the determination of the 6 DOF relating two free bodies. Sensor systems that can provide such information have varying sizes, weights, power requirements, complexities, and accuracies. One type of sensor system that can provide several key advantages is a binocular stereo vision system.

Fisher, Timothy E.↗

NASA NTRS1991

Image based tracking approaches to AR/C at the Johnson Space Center

Automated Rendezvous and Capture (AR&C) requires the determination of the six degrees of freedom relating two free bodies. Sensor systems that can provide such information have varying sizes, weights, power requirements, complexities and accuracies. One type of sensor system which can provide several key advantages is an image based tracking system, or better known as a machine vision system. By image based tracking we mean that the sensor is some imaging device such as one or more video cameras, from which the tracking parameters necessary to support the rendezvous and capture operations (range, attitude, etc.) can be derived. Image based tracking offers many advantages such as relative hardware simplicity and reprogrammability. These advantages must be weighed against the disadvantages of these systems, such as limited operational range, poorer accuracy at greater distances and sensitivity to lighting conditions. However, with properly designed algorithms and targets these disadvantages can be minimized for many important applications. Rigorous testing in realistic environments can further increase the robustness and reliability of these systems. This presentation describes the facilities used at JSC to support AR&C image based tracking development and the details of our binocular stereo approach to image based tracking.

Fisher, Timothy E.↗

NASA NTRS1990

Programmable Remapper

Input image remapped rapidly and accurately onto different coordinate grid. Analog/digital electronic image-processing system developed to warp input images onto arbitrary coordinate grids at video rates. Advantages of system include antialiasing effect of many-to-one data path and speed of lookup-table operation. Lookup tables reprogrammed easily with help of computer that generates table values from mathematical description of desired transformation. Applications include real-time corrections of distortions in input optics of image sensors, corrections for repeatable nonlinear scanning, and aiding persons of impaired vision by deliberately distorting images onto remaining functional portions of retinas.

Juday, Richard D.↗

NASA NTRS1990

Programmable remapper with single flow architecture

The invention relates to image processing systems and methods and in particular to a machine which accepts a real time video image in the form of a matrix of picture elements (pixels) and remaps such image according to a selectable one of a plurality of mapping functions to create an output matrix of pixels. Such mapping functions, or transformations, may be any one of a number of different transformations depending on the objective of the user of the system. The system remaps input images from one coordinate system to another using a set of look-up tables for the data necessary for the transform. The transforms, which are operator selectable, are precomputed and loaded into massive look-up tables. Input pixels, via the look-up tables of any particular transform selected, are mapped into output pixels with the radiance information of the input pixels being appropriately weighted. An earlier embodiment of the system included two parallel processors: a collective processor which mapped multiple input pixels into a single output pixel and an interpolative processor. The interpolative processor performed an interpolation among pixels in the input image where a given input pixel may affect the value of many output pixels. Several advantages are provided over previous embodiments in that the two distinct processors are replaced by a single processor capable of performing both types of operations (collective and interpolative) with no more complexity. Previously, there has existed no image processor or 'remapper' that can operate with sufficient speed and flexibility to permit investigating different transformation patterns in real time.

Fisher, Timothy E.↗

NASA NTRS1990

Orthogonal subspaces for correlation masking

A digital correlation mask that induces orthogonality among a prescribed set of reference imagery is described. In this particular implementation, the resulting correlation is undersampled and shift-variant, though if it is applied to optical correlators, those limitations are removed. A method of introducing orthogonality among the weights among the training set from which filter values are obtained is derived, so that the correlation value from a given filter is representative of the unique nature of the reference object as compared against the other objects in the training class.

Juday, Richard D.↗

NASA NTRS1989

Geometric transformations for video compression and human teleoperator display

A method for bandwidth-efficient processing of video imagery to be viewed by the teleoperator of a remotely-operated vehicle on which the camera is mounted is described. The method comprises image coding, transmission, and reconstruction. It is assumed that the transmission bandpass is the limiting factor rather than encoding/decoding schemata; that image coding and reconstruction will be done within the general abilities of the NASA/TI Programmable Remapper; and that the ratio of retained local detail to the operator's visual resolution is held constant throughout the large-field image that is seen. Novel features include that the compression and reconstruction address certain characteristics of the human visual system, that two-way communication controls a moving 'fovea' in the transformation, and that resolution varies over the image. Conventional motivations accommodated include the Cartesian raster-scan nature of available imagers and display devices and a need for low bandwidth in the image transmission. Unique image processing hardware, NASA's Programmable Remapper, allows demonstration of the method. Once refined, the technology could be adapted to special purpose imagers and display devices, or otherwise to dedicated image processing hardware.

Juday, Richard D.↗

NASA NTRS1989

An improved architecture for video rate image transformations

Geometric image transformations are of interest to pattern recognition algorithms for their use in simplifying some aspects of the pattern recognition process. Examples include reducing sensitivity to rotation, scale, and perspective of the object being recognized. The NASA Programmable Remapper can perform a wide variety of geometric transforms at full video rate. An architecture is proposed that extends its abilities and alleviates many of the first version's shortcomings. The need for the improvements are discussed in the context of the initial Programmable Remapper and the benefits and limitations it has delivered. The implementation and capabilities of the proposed architecture are discussed.

Fisher, Timothy E.↗

NASA NTRS1988

A programmable video image remapper

NASA's Johnson Space Center (JSC) has created the specifications for a new kind of image processing machine, a video-rate coordinate remapper. Previous image-processing machines for machine vision typically have done point operations without changing the geometry of the image. The JSC Programmable Remapper offers complete flexibility in changing the coordinates of an input image at video rates. Presented here are the main capabilities and some of the applications of such a device.

Fisher, Timothy E.↗