The design and analysis method of a MOEMS accelerometer consisting of a grating interferometry cavity and a micromachined sensing chip is presented in this paper. The grating interferometeric cavity is composed of a frequency-stabilized laser source, a diffraction grating, and a mirror ,to realize a subnanometer resolution. With an ultrasensitive micromachined chip, the MOEMS accelerometer can finally achieve a few ug resolution. This paper combines the geometrical optics and nano optics design methods to simulate the whole system, analyses how the divergence angle, grating constant and the length of the interferometeric cavity influence the ultimate sensitivity. A new set of MOEMS accelerometer is proposed, the theoretical analysis shows that the acceleration sensitivity can achieve 1200 v/g, and the resolution remains 1.3ug.
Infrared spectral imaging has been used in many fields, such as gas identification, environmental monitoring and target detection. In practical application, it is difficult to classify the spectrum between target and background due to cluster background and instrument noise. This article introduces the design of a modular FTIR imaging spectrometer based on interference optics and accurate control module. Based on this instrument, a spectral feature analysis and gas identification method is proposed and verified via experiment. The exact steps and algorithms include radiometric calibration, spectral pre-process, and spectral matching. First, multiple-points linear radiometric calibration is indicated to improve the calibration accuracy. Secondly, the spectral pre-processing methods are realized to decrease the noise and enhance the spectral difference between target and background. Thirdly, spectral matching based on similarity calculation is introduced to realize gas identification. Three methods, Euclidean distance (ED), spectral angle mapping (SAM) and spectral information divergence (SID), are derived. Finally, an experimental test is designed to verify the method proposed in this article, where SF6 is taken as the target. According to the results, various algorithms have different performance in time consumption and accuracy, and the proposed method is verified to be reliable and accurate in practical field test.
Due to the development of IR FPAs resolution and the transmission speed of the images, the requirement for the
high speed IR images transmission becomes a significant part in the whole IR imaging system. The fiber based
transmission method is proved to be a promising technique which can replace the traditional methods based on the
electrical signals. This paper introduces the design of digital IR images transmission technique based on fiber,
according to the characteristics of IR imaging data. This long wire transmission is accomplished utilizing the FPGA
which is designed to control the data cushion synthesis process, receive the high speed imaging data and send out
the real time VGA images. FPGA provides the reference clock signals to help the encoder convert the 16 bits
parallel imaging data into the serial LVDS signals. Then the MAX9376 chip is introduced to convert the LVDS
signals into the LVPECL signals, for only the LVPECL signals can be received by the laser diode. The receiving
process is just opposite, where the LVPECL signals are finally converted into the parallel data. To verify this design,
the VGA controller function is achieved by Verilog HDL programming in FPGA, so that the parallel IR imaging
data can be converted into the high resolution images. The experiment images show that the effective resolution of
the image in 64Mhz is 1024×800, and the transmission rate reaches 1.125Gb/s which is much higher than the
traditional methods and fully satisfies the requirement for the long distance IR imaging data transmission.
Infrared camera has more and more application in military, judicature, rescue, industry, hospital and science. Nowadays
the NETD (Noise Equivalent Temperature Difference) of high-sensitivity cooled infrared camera is less than 10 mK. If
we test the NETD from the analog video output port of infrared camera using 8-bit and 10-bit ADC frame grabber, the
NETD accuracy is 7.81 mK and 2.76 mK which correspond to relative error 78.7% and 27.6% for a 10 mK NETD
infrared camera. Such kind of accuracy is obviously not proper for the performance evaluation of high-sensitivity
infrared camera with NETD less than 10 mK. The NETD test accuracy can be improved by increasing the effective bit
number of the ADC of frame grabber. The quantization error of ADC of frame grabber has become the main factor
which contributes most to the NETD error of the high-sensitivity infrared camera. It is difficult to evaluate the electrooptical
performance of the high-sensitivity infrared camera through its analog video.
Although the NETD test accuracy can be improved by reducing the linear temperature range or increasing the effective
bits of the ADC of frame grabber under analog video interface test condition, it is difficult to meet the test needs. But
under the 14 bits digital video interface test condition and 1 K linear range, the NETD test accuracy of 0.24 mK can be
achieved. The NETD accuracy can be also improved by reducing the linear temperature range. The NETD test accuracy
can be 0.488 mK through 14-bit digital video under 2 K linear temperature range and its relative error equals 4.9% for a
10 mK NETD high-sensitivity infrared camera which meets the requirement. The test result through the digital video
port of an infrared camera shows that the test result through digital video port matches with its nominal value. This
necessitates the need of digital video interface of high-sensitivity infrared camera in NETD test in order to evaluate its performance accuracy.