ATP(Acquisition, pointing and tracking)technology is one of the key technologies and an important guarantee for establishing reliable links in the field of space laser communication. Liquid crystal phased array( LCOPA)is generally used as the core phase shifter for laser beam precise deflection. The classical precise deflection control method can only realize sparse and uneven concentric circle distribution in the deflection range, and the diffraction efficiency decreases seriously with the increase of deflection angles. Therefore, we propose a liquid crystal beam control method based on planar phased array radar model. The beam direction is controlled by changing phase difference between the electrodes. This method can realize two dimensional continuous beam deflection and uniform distribution. The deflection precision are analyzed and the theoretical simulation and experimental analysis are carried out. The results show that the precision is less than 14 μrad of x direction and 12 μrad of y direction within the range of 2.1 mrad beam deflection. Finally, the effect of rotation angle on two-dimensional deflection precision is analyzed.
Photoelectric shaft encoder is a kind of high-precision angle measuring device ,its core angle measuring component is encoder disc. In this paper, a single-ring absolute coding method combining Huffman coding is proposed. The Huffman coding algorithm commonly used for teletext compression transmission is applied to the single-ring photoelectric axis encoder to realize the new single-ring coding method of the coder disc. The method constructs a special Huffman binary tree and designs a special traversal sequence, which is traversed from top to bottom in this order. The code obtained at the leaf node is the shift sequence code required by the code disc, which can be used to engrave a single-circle absolute code disc. This method can improve the coding speed and reduce the complexity of the algorithm under the premise of high-order coding. It provides technical support for the research of small high-resolution photoelectric shaft encoder and accelerates its development speed.
In the liquid crystal spatial light modulator, creating overdriving look-up table is a cumbersome process. A large number of experiments are needed to measure the driving time between different target phases and the final phase, and the overdrive look-up table occupies excessive memory space that slow down the response speed of the liquid crystal. Aiming at the problems above, an establishment method of overdriving look-up table is put forward. The method uses PWM driving and curve fitting, only two response time curves measured will complete the calculation of the entire drive table, which solves the problem of the complicated experiment of overdriving table construction. Finally, choosing the appropriate quantization wavelength to optimize the overdriving table, effectively improving the accuracy of the drive table and the maintainability and scalability of the system, and it is more suitable for engineering applications.
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.