Raj K Gupta

US Patent:

6542829, Apr 1, 2003

Filed:

Sep 21, 2000

Appl. No.:

09/668013

Inventors:

Raj K. Gupta - San Francisco CA

Assignee:

Coventor, Inc. - Cary NC

International Classification:

G01B 300

US Classification:

702 33, 7351421, 257415, 700 97, 703 2, 716 5

Abstract:

Accurate characterization of microelectromechanical systems (MEMS) geometry is critical for device design and simulation, for material property extraction, and for post-fabrication trimming. According to the present embodiment, a method for characterizing parameters describing MEMS structures resulting from the fabrication process or process variations is presented. According to the prefered embodiment, experimentally obtained natural frequencies are compared with numerical simulations to identify unknown values of structural parameters or parameter variations. Further, the prefered embodiment teaches how electrostatically-driven laterally resonant comb-drive MEMS test structures with prescribed changes in spring width are used to characterize systematic variations in process offsets and sidewall angles. The disclosed technique is both in-situ and non-destructive.

US Patent:

59556595, Sep 21, 1999

Filed:

Jan 13, 1998

Appl. No.:

9/005919

Inventors:

Raj K. Gupta - San Francisco CA
Stephen D. Senturia - Brookline MA

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

G01F 138
H01L 2984
G01N 2700
G01N 1100

US Classification:

73 5401

Abstract:

A fluid property sensor includes a substrate having a first electrode thereon, and a flexible member adjacent the substrate and the first electrode wherein the flexible member includes a second electrode. A signal generator generates a predetermined electrical signal across the first and second electrodes so that an electrostatic force is generated between the first and second electrodes and so that said flexible member deflects a predetermined distance. A measuring circuit measures an interval of time between the generation of the predetermined electrical signal and the deflection of the flexible member to the predetermined distance and determines a property of a fluid adjacent the flexible member based on the interval of time. For example, the sensor can be used to determine a viscosity of the fluid. Alternately, the fluid can be a compressible gas, and the sensor can be used to determine a pressure of the gas.

US Patent:

20160341668, Nov 24, 2016

Filed:

Jan 15, 2015

Appl. No.:

15/111894

Inventors:

Raj Gupta - San Francisco CA, US
Steven Francis Nagle - Cambridge MA, US
Gajendra P. Singh - Allston MA, US
Owen R. Falk - San Francisco CA, US

International Classification:

G01N 21/65
G01J 3/02
G01J 3/44

Abstract:

Disclosed herein are systems and methods for performing angled confocal spectroscopy. Angled confocal spectroscopy permits sensitive, non-invasive investigation of numerous analytes in a wide variety of samples, including tissues and bodily fluids. The methods and systems disclosed herein can be used to measure spectroscopic signatures of analytes within well-defined and very small regions of samples, while at the same time achieving superior rejection of signal contributions from analytes within the sample that do not fall within a volume of interest. Accordingly, measurements can be performed at comparatively high signal-to-noise ratios, and can provide information such as concentrations and distributions of sample analytes at high spatial resolution. By using cylindrically-focused illumination light, samples can be excited by a “sheet” of light, allowing spatial signal averaging and enhancing the stability and reproducibility of the measurements.