In order to overcome the difficulty in imaging detection of high-speed moving targets under complex environments, and to get more comprehensive image information of the target, there is a urgent need to develop new high-performance optical imaging components. Compared to traditional lenses which have fixed shapes and immutable focal length, liquid-crystal microlens (LCMs) can not only adjust the focal length without changing the external shape, but also realize many practical functions such as swinging focus, spectral selection, depth of field adjustment, etc. The physical properties of spatial electric fields constructed between electrode plates of the LCMs are directly related to the light-field adjusting performances of LCMs, such as the polarity of electric field, the frequency and amplitude of applied voltage signal. In other words, the optical behaviors of LCMs will be affected remarkably by the parameters of driving voltage signal mentioned above. To implement these important functions flexibly and effectively, the driving voltage signal must be powerful and flexible. It had better to have multiple channels to control the direction of swinging focus, with relatively wide variance range to spread spectrum selection range, and with high precision to ensure accurately controlling LCMs. In addition, special waveforms may be required to support special functions of LCMs. Therefore a digital control device, which meet the requirements mentioned above, is designed, and then LCMs with it can realize imaging detection of targets in complex environment.
We present the results of numerical simulations and preliminary experiments to investigate the nano-focusing effect of incident light based on the surface plasmon polaritons (SPPs) on the nano-metallic-planar-apex metamaterials (NMPAM). The NMPAM are prepared by Focused Ion Beam lithography (FIB), a nanoscale fabrication tool. The NMPAM can be used to remarkably enhance the strength of the surface evanescent and lead to the excitation of several SPP modes on the metal surface. The interaction of different SPPs result in unique near-field optical properties for imaging and optical storage, so as to focus light into a nano-size point and thus enhance the light power greatly. The energy flow and electromagnetic field distribution is calculated by finite-difference time-domain (FDTD) method. The nano-spot position and intensity is experimentally shown to be controlled by the array of the apex. In our experiments, we fabricate a 10×10 array by FIB, and then the scanning near-field optical microscopy (SNOM) is used to observe the optical power distribution in nano-scale at the air-metal interface in the infrared region. we find that the light can be focus into ~100nm-scale and consequently enhance the light power up to several times than before common focusing method. The principle of nano-focusing based on nano-planar-apex is theoretically explained. The NMPAM can be utilized for coupling with infrared pixels to enhance the incident light converging so as to improve signal to noise ratio of infrared detection.
Polarization-independent microlens array based on liquid crystal (PI-LCMLA) has been an interesting and important topic in optoelectronic application. In this study, a polarization-independent microlens array using double layered nematic liquid crystals (LC) with orthogonal alignment is proposed and demonstrated. Two orthogonal LC layers are separated by a double-sided indium-tin oxide silica. Further optical experiments and investigations reveals that the PILCMLA can work in polarization and polarization-insensitive mode by operating the driving voltages. The normalized focusing intensity is no polarization dependence on the incident light. Several raw images at different working modes are obtained through by utilizing this novel configuration with low applied voltages. With advantages in high optical efficiency, simple manufacture, electrically tunable focal length, low power consumption, polarization independence and multi operation modes, this device can not only be used for imaging application but also has many potential applications in optical systems.
Hybrid recording is one of the most promising candidates to breaking down the technical barrels of the extremely high density recording. To acquire the goal, the recording grains must get much smaller than ever before, and at the same time, the track pitch must also decrease from ~200nm to ~70nm. Thus the design margin for the tracking servo shrinks dramatically.
This paper tries to answer questions like these: is the existing scheme still work on the conditions of the hybrid recording? If not, what are the key elements of the novel one? How to design such a fine servo system? The main concern of designing a servo system is relevant to several key factors, such as recording density; mechanics; signal to noise ratio. Some parameters should be assumed. This paper anticipates the requirements of the hybrid recording, and some assumptions (including recording density, mechanical characteristics, SNR, etc) have been made. Then, the requirements that the servo system should be met can be calculated. Results show that a novel tracking servo system should be designed. Finally a novel servo scheme is presented.
Multilevel recording has been demonstrated to significantly increase the linear densities achieved with standard methods of binary encoding in optical data storage systems. In this paper we introduce the theoretical concepts and practical coding aspects behind multilevel optical recording system. We show that there are three-stage coding flow and explain how to design and implement the encoder. As an example we give a 5th-power finite state transition diagram of q=8 RLL (2, 10) encoder and compute its adjacent matrix. Especially we discuss the implement method to quickly search decoding table of slider decoder by way of computing the least Hamming distance.
A calorific equilibrium equation is used to derive the relativities of optimum recording power and pulse waveform parameters in various disc scanning velocities. Based on the model, a new recording parameters calibrating flow is given as a referenced process. A number of optical recording examples have been examined in detail, and the results have been compared with those calculated data by use of a general summation approach.
Evanescent energy can be used to get extremely small optical spots. For the data storage applications, optical near field is defined in terms of Evanescent coupling between the system used to read or write data and recording layer. Near-field techniques can be applied to optical data storage systems to greatly increase recording density. So near-field recording technique has great potential in optical disc recording system and hybrid recording system. The characteristic of near-field recording spot is of vital importance in the data storage system basing the near-field theory, so it is absolutely necessary to be analyzed and measured. This paper analyses characteristic of near-field spots. The heat response time of the near field to overcome super paramagnetic effect is calculated basing the heat transfer theory. A novel measuring method for the diameter of near-field recording spot is also presented. Since the grain of the recording media is tiny enough, with the aid of atomic force microscope (AFM), near-field optical lithography can be accomplished. The diameter of near-field recording spot can be obtained by specifically designed computer either. So the relationship between the near-field recording spot diameter and the probe size of near-field recording system, the near field recording distance coupling between head and disc can be got.
This paper clarified the relationship between the radial dynamical characteristic of optical drivers and disks firstly. Then the specific parts comprising the radial dynamical characteristic of optical drivers (or disks) were identified. The statistical expectation and variance of the error due to specific clamping processes were studied thoroughly. At the end of the paper, the schematic of a practical measuring system was shown.
Measuring mechanical characteristics of optical disk is very significant. This paper compares the existing measuring methods and gives a novel method we adopted in details. Some measuring results are also shown.