Papers by Author: Qun Hao

Abstract: In this paper, we investigate the two-photon recording system in a 50-layer structure with each recording layer contains 4.7GB of data, similar to the capacity of a single layer Digital Versatile Disc, as the total capacity is 235GB/disc. We present a single-laser system to realize recording and reading and propose a new multilayer disc structure in which the groove structure is set on the substrate for servo control, the laser is separated by a PBS to two parts, one for recording and the other for servo in the optical system. Our research shows the feasibility of high density optical data storage using a single laser in a multilayer structure.

Abstract: Faster and more accurate optical aspheric testing methods are required in many technical fields. A digital moiré phase shifting interferometer (DMPSI) with partial compensation lens (PCL) is proposed. With digital phase shifting technique, only one shot of interferogram is required, so the system structure is simpler with lower sensitivity to the environmental vibration. PCL is designed to enlarge the measurement range of asphericity. A DMPSI prototype in Fizeau configuration has been developed. After calibration, spherical surface is tested with accuracy comparable to Zygo interferometer.

Abstract: A variety of specialized wavefront detection technologies have been widely used, generally need specialized sensor or device. In this contribution, we proposed an algorithm to calculate the wavefront aberration with two-dimensional modulation transfer function data. The relationship between the wavefront aberration and the modulation transfer function is built based on the optical transfer function and simplified by applying the Newton-cotes quadrature. Thus the wavefront aberration can be numerically calculated by use of the results of the system performance in frequency domain. Numerical calculation result is provided for validating the proposed algorithm.

Abstract: The mathematical simulations of the galvanic coupling intra-body communication (IBC) with different signal transmission paths have been introduced. Firstly, a galvanic coupling IBC circuit model was developed and the transfer function was derived. Secondly, the corresponding parameters were discussed. Finally, the signal attenuation characteristics of the galvanic coupling IBC were measured along the different signal transmission paths of the actual human bodies, while the corresponding mathematical simulations based on the proposed transfer function were carried out. A close agreement between the simulation results and measurement results has been demonstrated.

Abstract: Null compensator method is a popular aspheric surface testing method. However null compensator has the characteristics of complex structure, high price and poor universal property. This paper proposed to test aspheric surface by a partial compensation lens (PCL) to overcome the defect. This novel PCL method is designed to partially compensate the wave aberration caused by the aspheric surface, which allow some residual wave aberration exists. Research was conducted on measurement principle, design method of PCL. The experiment results show the feasibility and validity of this method.

Abstract: As aspheric surfaces are more often used in optical systems, suitable error evaluation methods and suitable accuracy calibration methods for related test instruments are urgently required. The two unsolved but important issues are addressed. For evaluation of aspheric surfaces, a scheme is proposed to separate the surface errors into radius error and local error. The effects of the two errors on image quality are discussed. For test instrument calibration, a practical method using a defocused spherical surface is described and verified with an absolute testing instrument based on laser deflectometry, which was developed at Beijing Institute of Technology. The feasibility of the schemes is shown and experimental results are presented.