A novel biochemical sensor based on planar optical waveguide is presented in this paper. The features of the sensor are as follows, the planar optical waveguide is made of SOI (Silicon-On-Insulator) material, a Mach Zehnder (M-Z) Interferometer structure is adopted as the sensing part, the sensor chip is fabricated using CMOS compatible technology and the size of the sensor chip is on the micron scale. Compared with the traditional biochemical sensors, this new type of sensor has such notable advantages as miniaturization, integration, high sensitivity and strong anti-interference capability, which provide the sensor with potential applications where traditional biochemical sensors cannot be used. At first, the benefits of SOI material comparing to other optical waveguide materials were analyzed in this paper. Then, according to the optical waveguide mode theory, M-Z interferometer waveguide was designed for the single mode behavior. By theoretical analysis of the radiation loss in the Y-junction of the planar waveguide interferometer, the relationship between the branch angle and the radiation loss was obtained. The power transfer function and the parametric equation of sensitivity of the M-Z interferometer were obtained through analysis of the waveguide structure. At last, the resolution of the effective refractive index and the characteristics of sensitivity of the sensor based on SOI M-Z Interferometer waveguide were simulated and analyzed by utilizing MATLAB software. As a result, the sensitivity of SOI M-Z Interferometer sensor can reach the order of 10-7 magnitude.
Star trackers based on charge-coupled device (CCD) or complementary metal-oxide semiconductor (CMOS) sensors, use a brightness independent star identification strategy that requires highly accurate measurements of star spot position. Therefore, precise calibration of the measurement model is crucial. Generally, ground-based real night sky observation is a specific and costly approach. In this work, an optical laboratory method for star tracker calibration is proposed. This method is based on ordinary instruments, laser autocollimation adjustment, and image processing techniques. The calibration issues of the star tracker with a brightness independent star identification strategy are analyzed. A new laboratory calibration method is introduced, and its results on an active pixel sensor (APS) star tracker are discussed. This method proves to be practical and adequate in the development of a star tracker with wide field of view.
Resonating cantilever-based microbiochemical sensors usually consist of a vibration actuating system and a vibration detecting system, which complicates the sensor design and fabrication. We present a new idea for testing the cantilever's vibration without an exclusive detector. The amplitude of vibration can be detected by measuring the third harmonic of the actuating current, and the cantilever's resonance frequency can be consequently obtained. The change of the resonance frequency provides information about the biochemical reaction, which alters the mass of the cantilever and its natural frequency. A system model based on the idea is established and an approximate solution is given. The relation between the vibration state and the third harmonic is discussed, and a corresponding simulation is performed. The system sensitivity is evaluated. Both theoretical and simulation results show that the amplitude of the third harmonic of the actuating current can be used as a criterion to determine the cantilever's vibration state. The idea promises a simpler mechanical structure, thus a cheaper sensor. Sensors based on this idea would also be robust to atrocious environments because the material of the cantilever can be chosen from a wide range.
CMOS APS based star tracker is a new generation of attitude sensor. An APS based autonomous star tracker has been proposed. This paper gives a primary demonstration of the software performance of the proposed star tracker, through laboratory and real night sky experiments. The star pattern recognition algorithm in the software protocol uses a quick search and robust match strategy and can perform independent star identification without prior attitude knowledge. The laboratory experiments validated the whole sky independent star pattern recognition algorithm and showed a comprehensive influence of errors and noise on the software performance. The real night sky experiments tested the sensitivity of the APS star sensor and validated the feasibility of the star identification and attitude estimation algorithm. In this paper, the structure and procedure of the software is described. The experiment system setup is introduced and the results of the laboratory and real sky experiments are presented and discussed.
This paper proposes an APS based Autonomous Star Tracker (AAST). The image sensor used in the star tracker is CMOS Active Pixel Sensor (APS). APS has many advantages to construct small, light weight, power saving and inexpensive star tracker for microsatellite application where power consumption and mass are critical. With the special design of optics, electronics and software, the proposed AAST can performance image sensing and process, star identification and attitude estimation all by itself and can output attitude data directly. The design concept of lower sensitivity with wider field of view enables the star tracker to perform whole sky independent star pattern recognition in the lost-in-space circumstance. These autonomous and independent features provide great convenience for the proposed star tracker to be applied in the future space mission. The total mass and power consumption of the AAST prototype are less than 1000g and 5W. The estimated accuracy is about 5" in the cross boresight direction and about 30" in the boresight direction.
In this paper we present an experimental system of miniature imaging spectrometer based on Acousto-Optic Tunable Filter (AOTF). The operating principle of AOTF and the properties of imaging spectrometer based on AOTF are introduced. The configuration of the AOTF device incorporated to the imaging spectrometer is described and the measured performance of the filter is summarized. The single beam configuration of the AOTF device and the utilization of a CMOS imaging IC as the focal plane sensor make the optics of the system very small, simple and compact. The power compensating circuit design of the RF driver of the acousto-optic cell ensures relatively high and consistent diffraction efficiencies over the whole tuning range of the filter. Qualitative experiments are carried out in laboratory. Results of the experiments preliminarily illustrate the capability of the miniature AOTF imaging spectrometer in hyperspectral remote sensing application.
In this paper we present a noncollinear TeO2 Acousto-Optic Tunable Filter (AOTF) device for a hyperspectral remote sensing system with moderate spatial and spectral resolution. The single beam configuration of the device will make the imaging optics behind it very simple and thus will make the whole system more compact. The power compensated circuit design of the RF driver of the acousto-optic filter gives relatively high and consistent diffraction efficiency over the whole tuning range in visible. The device can provide about 4° viewfield angle and 5 mm active aperture. The preliminary results have illustrated the capability of the device to be used for spectral imaging. The operation principle of AOTF will be introduced and its optical properties will be analyzed in this paper. The configuration of the AOTF device we developed for spectral imaging will be described and the measured performance of the filter will be summarized.
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.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
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.