A displacement measuring system based on grating double diffraction is proposed in this paper to eliminate the impact of multiple reflections of the zero-order diffraction beam and to reduce the stray light coming from the interference field. The principle of the proposed system is that with the proper interference of the first order beam of second diffraction, a displacement transducer can be obtained via the Doppler frequency shift and phase decoding. Simulation tests are conducted using LightTools model to prove the effectiveness of the proposed system. And experiment results shows that a resolution of 20 nm can be achieved over a range of 25 mm. It is therefore concluded that the proposed system can be used to improve the measurement resolution and accuracy.
A two pendulums driven spherical robot is designed for pipe inspection tasks in this paper and a circular trajectory motion control method is proposed. Compared with the traditional pendulum driven spherical robot, the improved two pendulums drive unit offers novel motion principle of circular trajectory motion which is studied by force analysis. Considering the motion characters, the circular trajectory motion is decomposed into forward roll and lateral roll, and the dynamics model is built based on the theorem of moment of momentum. In order to acquire the controllable velocity and radius of circular trajectory motion, a circular trajectory motion control strategy is proposed, by which the motion of one pendulum is planned according to the sine function to control the angle between the outer shell of the robot and the ground, and the motion of the other pendulum is controlled by position servo control to maintain the forward velocity of the robot. The controller of circular trajectory motion is designed for accurate tracking of the tile angle of the two pendulums, and the control strategy is validated by both numerical simulation and prototype experiment.
Mastering of the middle IR range is attractive for many applications, such as lidar gas analyzers, optoelectronic
countermeasures for suppression of IR detecting, optical communication systems, and scientific and medical instrument.
However, until now this has been held back by the lack of commercial coherent radiation sources with necessary energy
parameters and efficiency. AgGa1-xInxSe2 and Hg1-xCdxGa2S4 are well-known middle IR crystal families introduced in
recent years. The main advantage of them is that their physical properties including refractive indices and birefringence
can be engineered by varying the contents of Ga, In, Cd and Hg. Consequently, the phase matching range can be
extended and the 90° non-critical phase matching in three-wave interaction can be realized within a certain wavelength
band. In consideration of influence of composition ratio, acceptable composition ratio and group velocity mismatch of
ultra-short pulses on nonlinear properties of AgGa1-xInxSe2 and Hg1-xCdxGa2S4 are investigated for the first time. The
corresponding phase-matching diagrams and spectral dependence of the acceptable composition ratio on wavelengths for
second harmonic generation and optical parametric oscillation pumped by the popular Nd3+:YAG (1.06 &mgr;m) and
Ho3+:ILF (2.08 &mgr;m) lasers are estimated and demonstrated with accounting of available Sellmeier coefficients. Group
velocity matching for second harmonic, optical parametric generation under the pump of the two lasers in AgGa1-xInxSe2
and Hg1-xCdxGa2S4 are carried out as well. All relative results are compared and analyzed within a number of sampling
values or continuum of composition ratios. In addition, the utilities of AgGa1-xInxSe2 and Hg1-xCdxGa2S4 for second
harmonic generation are also discussed finally.
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.