Laser Rayleigh-Brillouin scattering is a powerful diagnostic tool for the study of gas flow properties. It provides an effective method for non-intrusive measurement of density, temperature and velocity in the gas flow. The received scattered laser light power is proportional to the gas density, the linewidth of the Rayleigh-Brillouin scattering spectrum is related to the gas temperature, and the Doppler frequency shift of the peak of the Rayleigh-Brillouin scattering spectrum is related to the gas velocity. The Rayleigh-Brillouin scattering spectrum can be measured by a Fabry-Perot interferometer operated in the imaging mode where an intensified CCD camera is frequently used to record the interference patterns of the Fabry-Perot interferometer. The Rayleigh-Brillouin scattering spectrum is then reconstructed from the measured data deconvolved with the Fabry-Perot instrument function. In this paper, the analysis and design of an imaging Fabry-Perot interferometer for the measurement of the Rayleigh-Brillouin scattering spectrum in the gas flow is presented. Some factors that limit the performance of the imaging Fabry-Perot interferometer are analyzed and discussed.
In this paper, the zoom theory of IR dual field-of-view zoom optical lens (FOVs) is introduced. The process of
how to solve the focal length and spaces of every group element by using performance parameters of infrared dual FOV
optical system is described and the solving method for initial structure of single lens and double separate lens used as
group is presented in detail. Particularly, great emphasis is give to discuss how to solve the initial structure for every
group with PW method. Finally, the design results for 8μm~12μm dual field-of-view zoom infrared systems using the
method mentioned above is presented and evaluated for each field by diffraction modulation transfer function(MTF),
which shows that the design makes a good system with high image quality.
High-power lasers are widely used in various scientific, industrial and military applications. There is currently a desire
for precision measurement the beam quality of high-power lasers in order to evaluate the performance of the laser
systems and the operational effectiveness of chemical and solid-state high-power laser weapons. There are many
methods of beam quality determination, such as beam parameter product, encircled energy ratio BQ, Strehi ratio,
diffraction limit factor β and beam propagation factor M<sup>2</sup>. In this paper, a beam quality measurement device is developed
for high-power lasers. This device consists of a beam attenuator with large reflective ratio and minimal wavefront
distortion, an off-axis parabolic mirror, an imaging lens and an infrared focal plane array detector. The laser beam
intensity distribution, beam width, beam divergence and beam pointing stability can be obtained in real-time and the
beam quality can be evaluated by the various determinations through imaging process. Advantages and disadvantages of
these beam quality determination for evaluation the performance of the high-power lasers are analyzed and discussed.
The measurement uncertainties of relative parameters are also analyzed and discussed.