Proc. SPIE. 9685, 8th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems; and Smart Structures and Materials
Optical micro-structure array, including microlens array and pyramid array, has the function of integral imaging or diffraction beam-splitting. Careful measurement of the 3D profile of the array is a basic approach for insuring its quality. However, due to the limited numerical aperture of microscopy, when the surface is too steep, typically larger than 45 degrees, little light will be reflected or scattered back to the measurement equipment. The signal-to-noise-ratio will drop below the measurable threshold and information will be lost during measurement. In our case, the dihedral of the sample surface is 90 degrees. Intuitively, the reflected rays should be parallel to the incident rays after twice reflection and can be picked up by the detector. Nevertheless, the white-light interference microscope still showed no information on the 45- degree-inclined surface. In this paper, we study the twice-reflection of the dihedral angle of 90 degrees. We put it in the test beam of a spherical interferometer to simulate the situation in microscope. Simulation and real experiments suggest that the twice-reflection beam is of low spatial coherence and may act as the background intensity in white-light interferogram. This result cannot lead to a novel testing approach directly but points out the problem. We will sprout new idea based on it.
Micro-structured array is a crucial optical element with wide range of applications. The optical performance of microstructured array is determined by feature sizes of array, such as diameter, depth and the uniformity across the whole array. Those sizes can be directed retrieved from the 3D profile. We propose a 3D profile measurement system based on light field microscope, which is promising in achieving fast data acquisition by one shot. We propose the principle of measurement, develop the algorithm for focus stack calculation and 3D reconstruction. Preliminary experiments suggest the prospects and challenges.
Laser echo signal simulator is one of the most significant components of hardware-in-the-loop (HWIL) simulation systems for LADAR. System model and time series model of laser echo signal simulator are established. Some influential factors which could induce fixed error and random error on the simulated return signals are analyzed, and then these system insertion errors are analyzed quantitatively. Using this theoretical model, the simulation system is investigated experimentally. The results corrected by subtracting fixed error indicate that the range error of the simulated laser return signal is less than 0.25m, and the distance range that the system can simulate is from 50m to 20km.
LADAR echo signal simulator is one of the most significant components of hardware-in-the-loop (HWIL) simulation systems for LADAR, which is designed to simulate the LADAR return signal in laboratory conditions. The device can provide the laser echo signal of target and background for imaging LADAR systems to test whether it is of good performance. Some key technologies are investigated in this paper. Firstly, the 3D model of typical target is built, and transformed to the data of the target echo signal based on ranging equation and targets reflection characteristics. Then, system model and time series model of LADAR echo signal simulator are established. Some influential factors which could induce fixed delay error and random delay error on the simulated return signals are analyzed. In the simulation system, the signal propagating delay of circuits and the response time of pulsed lasers are belong to fixed delay error. The counting error of digital delay generator, the jitter of system clock and the desynchronized between trigger signal and clock signal are a part of random delay error. Furthermore, these system insertion delays are analyzed quantitatively, and the noisy data are obtained. The target echo signals are got by superimposing of the noisy data and the pure target echo signal. In order to overcome these disadvantageous factors, a method of adjusting the timing diagram of the simulation system is proposed. Finally, the simulated echo signals are processed by using a detection algorithm to complete the 3D model reconstruction of object. The simulation results reveal that the range resolution can be better than 8 cm.
The Hardware-in-the-loop simulation can establish the target/interference physical radiation and interception of product flight process in the testing room. In particular, the simulation of environment is more difficult for high radiation energy and complicated interference model. Here the development in IR scene generation produced by a fiber array imaging transducer with circumferential lamp spot sources is introduced. The IR simulation capability includes effective simulation of aircraft signatures and point-source IR countermeasures. Two point-sources as interference can move in two-dimension random directions. For simulation the process of interference release, the radiation and motion characteristic is tested. Through the zero calibration for optical axis of simulator, the radiation can be well projected to the product detector. The test and calibration results show the new type compound simulator can be used in the hardware-in-the-loop simulation trial.
With the development of optical fiber communication, dense wavelength division multiplexing (DWDM) system is important for the rapid management of multi-wavelength in the core node of the optical transmission network. In this paper, a reconfigurable optical add-drop multiplexer (ROADM) based on the tunable Fabry-Perot (F-P) array is proposed. An optical switch with high isolation and low crosstalk is designed by using the characteristics of filtering and tuning for the F-P array. The principle, structure, and function of the tunable F-P array are introduced. The characteristics of filtering and tuning for the F-P filter are also calculated, and the factor for the isolation, crosstalk, response time and insertion loss are analyzed. A single physical channel ROADM with 16 signal channels, which operates in C-band, is designed and optimized by simulation.
LADAR guidance technology is one of the most promising precision guidance technologies. In the aim of simulating the
return waveform of the target, a 3D geometrical model of a target is built and mathematical model of target echo signal
for imaging LADAR target simulator is established by using the coordinate transformation, radar equation and ranging
equation. First, the 3D geometrical data of the object model is obtained by 3D geometrical modeling. Then, target
coordinate system and viewpoint coordinate system are created respectively. 3D geometrical model is built in the target
coordinate system. The 3D geometrical model is transformed to the viewpoint coordinate system based on the derived
relationship between the two coordinate systems. Furthermore, the range information of the target could be obtained
under viewpoint coordinate system. Thus, the data of the target echo signal can be obtained by using radar equation and
ranging equation. Finally, the echo signal can be exported through corresponding data interface. In order to validate the
method proposed in this paper, the echo signal generated by a typical target is computed and compared with the theory
solutions. The signals can be applied to drive target simulator to generate a physical target LADAR image.
Infrared target simulator is an important unit in guidance hardware-in-the-loop simulation systems. It is used to simulate
the radiation and motion characteristics of target, decoy and background. This paper proposed a multi-channel IR target
simulator. It could generate one IR point target, two pairs of IR decoys and background respectively in the same field of
view of the seeker’s optical system simultaneously. An IR imaging fiber bundle as the focal plane of the projection optical
system was used to compound the target, decoys and background. The compound scene was projected to the seeker by the
projection optical system. In IR imaging channel, IR scene was generated by an optical film chip as a visible to thermal
transducer which was placed in a vacuum cell. The simulated temperature range of IR scene could be from room
temperature to 430K.The thin film transducer had 512×512 pixels. Its frame rate could reach to 100Hz. Light sources with
high equivalent black body temperature were adopted in IR target and decoy channels. The size and the radiation intensity
of the IR point target and decoys could be controlled by pin holes and attenuators. The point target and decoys driven by
high precise motors could travel through the whole instantaneous field of view of the seeker’s optical system. Two pairs of
decoys could move away from the center to the edge of the instantaneous field of view. The highest simulated black body
temperature of the point source was 1200K.
An infrared (IR, 3–5 and 8–12 μm)/microwave (MW, 2.7 GHz) micromirror array type of beam combiner was fabricated for test and analysis. A model based on transmission line theory, Snell’s law, and phase monopulse radar theory was built to analyze the boresight angle errors. Three types of boresight angle errors—inherent error, refraction-induced error and combiner inserting error—were calculated. The results indicated that combiner inserting error was the most important error. Using this theoretical model, a beam combiner was optimized, fabricated, and investigated experimentally. Measured by a phase monopulse radar, the boresight angle error introduced by the beam combiner was <0.1 deg , which coincided with the theoretical calculations. Infrared images were reflected by the beam combiner, the angular resolution of the reflected images in azimuth, and elevation directions were 40 and 80 in., respectively.
A novel method is presented for the design and the fabrication of the
Diffractive Optical Elements (DOEs) with arbitrary complex phase profile
based on interference. The DOEs are designed to modulate the complex light
wave by the analytical formulas, and asymmetric holographic DOE with cubic
phase modulation is fabricated by two-step exposure technique on flat plane.
Further it is employed for the modulation of the optical intensity on curved
surfaces (CS) and apply it to fabricate diffractive optical elements (DOEs) with
arbitrary profile and large area on CS. Both a binary pattern and a gray pattern
are reconstructed numerically on the lens surfaces with big curvatures in large
areas, while a binary and nonperiodic pattern is produced experimentally. The
simulations together with the experiment demonstrate the validity of the
method. It is believed that micro- or nano- optical elements with smaller
feature sizes can be fabricated by the proposed method when an optical
microscopy system is used. It will be a very efficient and convenient way to
design and fabricate the DOEs with required complex fine structure.