Mr. William Walker Profile

William Walker

Embedded Systems Engineer at BlueHalo

SPIE Involvement:

Author

Publications (2)

This will count as one of your downloads.

You will have access to both the presentation and article (if available).

DOWNLOAD NOW

This content is available for download via your institution's subscription. To access this item, please sign in to your personal account.

Email or Username Forgot your username?

Password Forgot your password?

Show

Keep me signed in

No SPIE account? Create an account

Proceedings Article | 15 February 2018 Presentation + Paper

Design and qualification of a small customizable fast steering mirror (FSM) for FSOC stabilization and scanning applications

N. Jacka, W. Walker, M. Roybal, J. McNally

Proceedings Volume 10524, 1052407 (2018) https://doi.org/10.1117/12.2291121

KEYWORDS: Optical tracking, Calibration, Laser systems engineering, Sensors, Actuators, Telecommunications, Control systems, Data communications, Mirrors, Laser communications

Read Abstract +

Numerous Free Space Optical Communications (FSOC) applications use fine tracking to achieve precise jitter stabilization necessary for high data rate communications. In addition, precision pointing mechanism are often required for point-ahead of the transmit laser. Prior systems have used either fast steering mirrors (FSMs), piezoelectric fiber optic positioners, or inertially stabilized platforms each of which has its own advantages and disadvantages for different applications.

We developed a small form-factor, high performance FSM capable of meeting both high bandwidth stabilization requirements as well as high precision pointing necessary for the point-ahead function. The current design achieves a 2.5 kHz closed-loop optical track bandwidth, <5 μrad/mrad accuracy, and better than 15 nm rms surface figure error. Because there is no single approach to FSOC architecture, we designed the FSM to be easily scaled and customized for various applications ranging from FSOC, image stabilization, and scanning. Simple choices and customization of the FSM components including the mirror substrate, flexure, feedback sensors, and actuator design can provide custom designs for various applications. Analysis tools were developed to quickly trade the multitude of design parameters that influence performance. This paper reviews the FSM design, performance, and qualification test results, and trade space available to customize the FSM. We present analysis and test data from a couple of design variations to show how our design and analysis approach allows the FSM to be quickly adapted to various performance and environmental requirements.

Proceedings Article | 21 May 2015 Paper

Multi-pass encoding of hyperspectral imagery with spectral quality control

Steven Wasson, William Walker

Proceedings Volume 9472, 947208 (2015) https://doi.org/10.1117/12.2086630

KEYWORDS: Image compression, Hyperspectral imaging, Computer programming, Signal to noise ratio, Distortion, Quantization, Video coding, Video, Algorithm development, Target detection

Read Abstract +

Multi-pass encoding is a technique employed in the field of video compression that maximizes the quality of an encoded video sequence within the constraints of a specified bit rate. This paper presents research where multi-pass encoding is extended to the field of hyperspectral image compression. Unlike video, which is primarily intended to be viewed by a human observer, hyperspectral imagery is processed by computational algorithms that generally attempt to classify the pixel spectra within the imagery. As such, these algorithms are more sensitive to distortion in the spectral dimension of the image than they are to perceptual distortion in the spatial dimension. The compression algorithm developed for this research, which uses the Karhunen-Loeve transform for spectral decorrelation followed by a modified H.264/Advanced Video Coding (AVC) encoder, maintains a user-specified spectral quality level while maximizing the compression ratio throughout the encoding process. The compression performance may be considered near-lossless in certain scenarios. For qualitative purposes, this paper presents the performance of the compression algorithm for several Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and Hyperion datasets using spectral angle as the spectral quality assessment function. Specifically, the compression performance is illustrated in the form of rate-distortion curves that plot spectral angle versus bits per pixel per band (bpppb).

My Library

You currently do not have any folders to save your paper to! Create a new folder below.

Folder Name

Folder Description

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks. You are receiving this notice because your organization may not have SPIE eBooks access.*

*Shibboleth/Open Athens users─please sign in to access your institution's subscriptions.

To obtain this item, you may purchase the complete book in print or electronic format on SPIE.org.

ORGANIZATIONAL
Sign in with credentials provided by your organization.

Organizational Username

Organizational Password

Show/Hide Password

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available

Members:

Non-members: ADD TO CART

Keywords/Phrases

Search In:

Publication Years