Browsing by Author "So, Stephen"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Development of Digital Signal Processor controlled Quantum Cascade Laser based Trace Gas Sensor Technology
    (2006-08-01) So, Stephen; Wysocki, Gerard; Frantz, Patrick; Tittel, Frank K.; Center for Multimedia Communications (http://cmc.rice.edu/); Digital Signal Processing (http://dsp.rice.edu/)
    This work reports the design and integration of a custom digital signal processor (DSP) system into a pulsed quantum cascade laser (QCL) based trace gas sensor to improve its portability, robustness and operating performance. Specifically, this work describes the implementation of a custom prototype DSP data acquisition/system controller based on the Texas Instruments TMS320F2812 for embedded control and processing. In addition, the sensor incorporates oversampling by taking advantage of the high speed conversion capabilities of the analog-to-digital converter (ADC) which is embedded in the DSP. A carbon monoxide (CO) sensor employing a thermoelectrically (TE) cooled, pulsed 4.6 µm distributed feedback (DFB) QCL as a mid-infrared radiation source is used to evaluate the performance characteristics of such a DSP controlled spectroscopic gas sensor.
  • Thumbnail Image
    Item
    Integrated embedded processor based laser spectroscopic sensor
    (2012-12-18) So, Stephen; Wysocki, Gerard; Frantz, Patrick J.; Tittel, Frank K.; Rice University; United States Patent and Trademark Office
    A novel low-power and compact laser spectroscopic sensor is described herein. Embodiments of the disclosed sensor utilize state-of-the-art microprocessors and digital processing techniques to reduce power consumption and integrate functions into a small device. In particular, novel software methods are disclosed which allow the use of low-power microprocessors which draw no more than about 0.02 W of power. Such low-power enables long battery life and allows embodiments of the sensor to be used in portable applications. In addition, the system architecture and methods described in this disclosure allow a single integrated embedded processor to control all the subsystems necessary for a laser spectroscopic sensor further reducing sensor size and power consumption. In addition, a power efficient method of calibrating a photoacoustic laser spectroscopic sensor is disclosed.
  • Thumbnail Image
    Item
    Integrated embedded processor based laser spectroscopic sensor
    (2012-01-17) So, Stephen; Wysocki, Gerard; Frantz, Patrick J.; Tittel, Frank K.; Rice University; United States Patent and Trademark Office
    A novel low-power and compact laser spectroscopic sensor is described herein. Embodiments of the disclosed sensor utilize state-of-the-art microprocessors and digital processing techniques to reduce power consumption and integrate functions into a small device. In particular, novel software methods are disclosed which allow the use of low-power microprocessors which draw no more than about 0.02 W of power. Such low-power enables long battery life and allows embodiments of the sensor to be used in portable applications. In addition, the system architecture and methods described in this disclosure allow a single integrated embedded processor to control all the subsystems necessary for a laser spectroscopic sensor further reducing sensor size and power consumption. In addition, a power efficient method of calibrating a photoacoustic laser spectroscopic sensor is disclosed.
  • Thumbnail Image
    Item
    Ppb-level formaldehyde detection using a CW room-temperature interband cascade laser and a miniature dense pattern multipass gas cell
    (The Optical Society, 2015) Dong, Lei; Yu, Yajun; Li, Chunguang; So, Stephen; Tittel, Frank K.
    A ppb-level formaldehyde (H2CO) sensor was developed using a thermoelectrically cooled (TEC), continuous-wave (CW) room temperature interband cascade laser (ICL) emitting at 3.59 μm and a miniature dense pattern multipass gas cell with >50 m optical path length. Performance of the sensor was investigated with two measurement schemes: direct absorption (DAS) and wavelength modulation spectroscopy (WMS). With an integration time of less than 1.5 second, a detection limit of ~3 ppbv for H2CO measurement with precision of 1.25 ppbv for DAS and 0.58 ppbv for WMS, respectively, was achieved without zero air based background subtraction. An Allan-Werle variance analysis indicated that the precisions can be further improved to 0.26 ppbv @ 300s for DAS and 69 pptv @ 90 s for WMS, respectively. A side-by-side comparison between two measurement schemes is also discussed in detail.
  • Thumbnail Image
    Item
    Quantum Cascade Laser Spectrometer for Trace-Gas Detection of Exhaled Carbonyl Sulfide
    (2004-05-01) Wysocki, Gerard; So, Stephen; McCurdy, Matthew; Roller, Chad; Weidman, Daniel; Frantz, Patrick; Curl, Robert; Tittel, Frank K.; Center for Multimedia Communications (http://cmc.rice.edu/)
    Simultaneous concentration measurements of echaled carbonyl sulfide and carbon dioxide were demonstrated using a pulsed quantum cascade laser based gas sensor. This sensor has potential applications in biomedical diagnostics such as in lung transplant rejection.