Matthew Sandy

Single- and three-axis geophone: footstep detection with bearing estimation, localization, and tracking

Tactical capabilities of single and three axis geophones for seismic detection and bearing estimation for homeland security and defense applications are described. It is shown that typically three axis geophones yield a high bearing estimation error. An alternate bearing estimation approach is based on using the time delay in footstep signal detection from three triangulated single axis vertical geophones. In this approach the standard deviation of the bearing estimation error is less than 12 degrees for a walking person distance of 10 to 70m and geophone distances of 8 to 9 m. We find that using the three-axis geophone approach makes it harder for path tracking and bearing estimation within the tactical zone area. We report that a single-axis geophone approach for riangulation of walking person is more effective. In addition, road monitoring is also more efficient using a single-axis geophone approach. We compare the relative and absolute improvement of bearing estimation probability for road monitoring using three single-axis geophones versus 1, 2 and 3 three-axis geophones. We will also discuss the use of single axis vertical geophone sets for monitoring various zone sizes.

Seismic footstep signal characterization

Seismic footstep detection based systems for homeland security applications are an important additional layer to perimeter protection and other security systems. This article reports seismic footstep signal characterization for different signal to noise ratios. Various footstep signal spectra are analyzed for different distances between a walking person and a seismic sensor. We also investigated kurtosis of the real footstep signals under various environmental and modeled noises. We also report on the results of seismic signal summation from separate geophones. A seismic signal sum spectrum obtained was broader than that obtained from a single sensor. The peak of the seismic signal sum was broader than that from the footstep signal of the single sensor. The signal and noise spectra have a greater overlap for a seismic signal sum than that from a single sensor. Generally, it is more difficult to filter out the noise from the sum of the seismic signals. We show that the use of the traditional approach of spectrum technology and/or the statistical characteristics of signal to noise of reliable footstep detection systems is not practical.

Designing a reference for CD-SEM magnification calibration

In order to design a reference suitable for performing CD-SEM magnification calibration with high precision and accuracy it is necessary to first identify the relevant critical issues. We will discuss why the magnification calibration reference is a key challenge; why CD-SEM magnification calibration is not trivial; and why a suitable magnification calibration reference does not currently exist. We will identify the criticalities for the above issues. We will present a novel solution leading to design criteria for a universal CD-SEM magnification calibration reference.

Scan linearity: a hidden factor in SEM magnification calibration

Scan linearity of a review (cross-section) Scanning Electron Microscope (SEM) has been studied using Nanometrology’s proprietary software and reference samples. Nonlinearity across the field of view was measured at greater than 6.5% before and under 1% after correction by the SEM company’s engineer. The scan non-linearity was measured with precision better than 0.2% across the field of view. This is in spite of the nonuniformity of the reference sample which was measured at greater than 2.5%. The precision of the non-uniformity measurement of the reference sample was better than 0.1%.

Factors influencing CD-SEM metrology

Nanometrology LLC has developed a unique set of solutions for optimizing CD-SEM metrology by improving signal to noise ratio and quantifying scan non-linearity. Examples of Nanometrologys solutions for improved CD-SEM magnification calibration are demonstrated using CD-SEMs from a variety of user sites. To our knowledge, this is the first time that a method to quantify CD-SEM scan non-linearity with precision 0.1 percent has been reported. Calibration precision of 0.1 percent or better can be achieved on both cross-section and CD-SEMs to enable them to meet or exceed the requirements of the ITRS roadmap beyond 2014.

Mobile, portable lightweight wireless video recording solutions for homeland security, defense, and law enforcement applications

It is desirable for executive officers of law enforcement agencies and other executive officers in homeland security and defense, as well as first responders, to have some basic information about the latest trend on mobile, portable lightweight wireless video recording solutions available on the market. This paper reviews and discusses a number of studies on the use and effectiveness of wireless video recording solutions. It provides insights into the features of wearable video recording devices that offer excellent applications for the category of security agencies listed in this paper. It also provides answers to key questions such as: how to determine the type of video recording solutions most suitable for the needs of your agency, the essential features to look for when selecting a device for your video needs, and the privacy issues involved with wearable video recording devices.

Quantifying drift in SEM

A novel approach for determining the drift behavior of an SEM with high precision in 2D space is presented. David Joy described an indirect proceudre for qualitatively detecting image drift in the time domain using FFTs of sequential images. SEM metrology is based on first acquiring an image representation of an object. In this paper, we present a direct approach for quantifying SEM image drift. The next step is applying various algorithms which attempt to determine feature boundaries. The above sequence is based on a stable SEM performance during teh image acquisition interval. If movement of the feature within the imaged field occurs during the acquisition interval, a distorted stability is a critical precursor for precision SEM metrology. We will describe a novel approach for quantifying SEM drift with a precision greeater than 0.2nm within an image field.

Matching and monitoring a CD-SEM tool cluster

Nanometrologys unique solution to CD-SEM magnification calibration and matching. This utilizes a novel magnification calibration reference material (MCRM) designed and fabricated on an 8 inch wafer. When used with the proprietary software, it allows one to calibrate and match individual CD-SEMs. CD-SEM behavior can now be quantified in terms of its parameters such as the average magnification in the field of view (FOV), magnification non-linearity and magnification stability. It is essential to quantify these parameters with a precision of 0.1 percent or better in order to meet requirements for sub-100nm metrology.