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Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

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Early Posting

Accepted papers to appear in an upcoming issue

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July


Thermal stresses developed during elevated temperature cleaning of large coated optics

  • Heather Liddell, John Lambropoulos, and Stephen Jacobs
  • received 05/21/2014; accepted 07/29/2014; posted 07/29/2014; Doc. ID 212516
  • [full text: PDF (1781) KB)]
  • Abstract: A thermomechanical model is developed to estimate the stress response of an oxide coating to elevated-temperature chemical cleaning. Using a hafnia–silica multilayer dielectric pulse compressor grating as a case study, we demonstrate that substrate thickness can strongly affect the thermal stress response of the thin-film coating. As a result, coatings on large, thick substrates may be susceptible to modes of stress-induced failure (crazing or delamination) not seen in small parts. We compare the stress response of meter-scale optics to the behavior of small-scale test or “witness” samples, which are expected to be representative of their full-size counterparts. The effects of materials selection, solution temperature, and heating/cooling rates are explored. Extending the model to other situations, thermal stress results are surveyed for various combinations of commonly used materials. Seven oxide coatings (hafnia, silica, tantala, niobia, alumina, and multilayers of hafnia–silica and alumina−silica) and three glass substrates (BK7, borosilicate float glass, and fused silica) are examined to highlight some interesting results.

Keywords (OCIS):

  • (160.4670) Materials : Optical materials
  • (310.6870) Thin films : Thin films, other properties
  • (310.6845) Thin films : Thin film devices and applications

Electrically tunable infrared filter based on the Liquid-Crystal Fabry-Perot structure for spectral imaging detection

  • huai zhang, Afzal Muhammmad, Jun Luo, hongshi sang, xinyu zhang, changsheng xie, tong qing, and yu lei
  • received 05/30/2014; accepted 07/29/2014; posted 07/29/2014; Doc. ID 212977
  • [full text: PDF (2076) KB)]
  • Abstract: An electrically tunable infrared filter based on the key structure of Liquid-Crystal (LC) Fabry-Perot (FP), which works in the wavelength range from 5.5μm to 12μm, is designed and fabricated successfully. Both planar reflective mirrors with a very high reflectivity of ~95%, which are shaped by depositing a layer of aluminum (Al) film over one side of each double-side polished Zinc Selenide (ZnSe) wafer, are coupled into a dual-mirror FP cavity. The LC materials are filled into the FP cavity for construction the LC-FP filter with a LC layer thickness of ~7.5μm, which is a typical sandwich architecture. The top and bottom mirror of the FP cavity are further coated by an alignment layer with a thickness of ~100nm over Al film. The formed alignment layer is thus rubbed strongly to shape relatively deep V-grooves for effectively anchoring LC molecules. Common optical tests show some particular properties, for instance, existing three transmission peaks in measured wavelength range, and the minimum full-width-half-maximum (FWHM) being ~120nm, and then the maximum adjustment extent of imaging wavelength being ~500nm through applying a voltage driving-signal with a root-means-square (RMS) value ranging from 0V to ~19.8V. The experiment results are consistent with the simulation according to the model setup by us. The spectral images obtained in the long-wavelength infrared (LWIR) range through the LC-FP device driven by the voltage signal with different RMS value, demonstrates a prospect of realization smart spectral imaging and further integrating the LC-FP filter with infrared focal plane arrays (FPAs). The developed LC-FP filters show some advantages such as electrically tunable imaging wavelength, very high structural and photoelectronic response stability, small size and low power consumption, and very high filling-factor of more than 95% compared with common MEMS-FP spectral imaging approach.

Keywords (OCIS):

  • (120.2230) Instrumentation, measurement, and metrology : Fabry-Perot
  • (230.3720) Optical devices : Liquid-crystal devices
  • (260.3060) Physical optics : Infrared
  • (110.4234) Imaging systems : Multispectral and hyperspectral imaging

Elastomer-based opto-thermo-mechanical actuation and its application to autonomous, self-powered light-level control

  • Jaeyoun Kim and Rabin Dhakal
  • received 05/30/2014; accepted 07/28/2014; posted 07/29/2014; Doc. ID 213175
  • [full text: PDF (406) KB)]
  • Abstract: We present a new light-level control scheme for total internal reflection (TIR)-based lightguides. As the control mechanism, we exploit the frustrated TIR induced by the approach of another lightguide. To actuate the second lightguide, we utilize the heat-induced volume increase of phase-change materials. By delivering the heat optically and translating the volume change into mechanical actuation through elastomeric encapsulation, we render the whole system completely opto-thermo-mechanical. We configure the actuator to respond to the increase in the control light-level with a matching increase in the degree of frustrated TIR. By utilizing a portion of the input light to the main lightguide as the control light and setting the operation point judiciously, we accomplish an autonomous, self-powered light-level control. Our test unit can suppress the rms-change in the output light-level below 2/3 of that in the input light-level without requiring externally supplied signal or power.

Keywords (OCIS):

  • (230.1150) Optical devices : All-optical devices
  • (350.6050) Other areas of optics : Solar energy
  • (230.4685) Optical devices : Optical microelectromechanical devices

Inverse axial mounting stiffness design for lithographic projection lenses

  • Yuan Wen-quan, Zhang Wei, and Hongbo Shang
  • received 05/26/2014; accepted 07/28/2014; posted 07/29/2014; Doc. ID 212819
  • [full text: PDF (1513) KB)]
  • Abstract: In order to balance axial mounting stiffness of lithographic projection lenses and the image quality under dynamic working conditions, an easy inverse axial mounting stiffness design method is developed in this article. Imaging quality deterioration at wafer under different axial vibration levels are analyzed, and desired image quality can be determined according to industrial requirements. Axial vibrational tolerance of each lens is solved with damped least square method. Based on adaptive interval adjustment, binary search algorithm and finite elements (FE) method, axial mounting stiffness of each lens can be travelled in a large interval, and converges to a moderate value which makes axial vibrational amplitude of the lens converges to its tolerance. Model simulation is carried out to validate effectiveness of the method, and the uncertainties of solving complexity are discussed.

Keywords (OCIS):

  • (110.3000) Imaging systems : Image quality assessment
  • (110.5220) Imaging systems : Photolithography
  • (220.1010) Optical design and fabrication : Aberrations (global)
  • (220.1140) Optical design and fabrication : Alignment
  • (220.3740) Optical design and fabrication : Lithography
  • (220.4880) Optical design and fabrication : Optomechanics

(ODT2014) A Study of Optical Design of Blu-Ray Pickup Head System with a Liquid Crystal Element

  • Yi-Chin Fang, Chih-Ta Yen, and Jui-Hsin Hsu
  • received 04/29/2014; accepted 07/28/2014; posted 07/28/2014; Doc. ID 210937
  • [full text: PDF (596) KB)]
  • Abstract: This paper proposes a newly developed optical design and an active compensation method for a Blu-ray pickup head system with a liquid crystal (LC) element. Different from traditional pick up lens design, this new optical design delivers performance as good as conventional one but have more rooms for tolerance control, which play the role at anti-shaking devices such as portable Blu-ray player. A hole-pattern electrode and LC optics with external voltage input were employed to generate a symmetric nonuniform electrical field in the LC layer that directs LC molecules into the appropriate gradient refractive index distribution, resulting in the convergence or divergence of specific light beams. LC optics delivers fast and, most importantly, active compensation through optical design when errors occur. Simulations and tolerance analysis were conducted using Code V software, including various tolerance analyses, such as defocus, tilt, and decenter, and their related compensations. Two distinct Blu-ray pickup head system designs were examined in this study. In traditional Blu-ray pickup head system designs, the aperture stop is always set on objective lenses. In the study, the aperture stop is on the LC lens as a newly developed lens. The results revealed that an optical design with aperture stop set on LC lens as an active compensation device successfully eliminated up to 57% of coma aberration compared with traditional optical designs so that this pick up head lens design will have more spaces for tolerance control.

Keywords (OCIS):

  • (220.1000) Optical design and fabrication : Aberration compensation
  • (220.3620) Optical design and fabrication : Lens system design

(DH3D) Phase aberration compensation using virtual confocal scheme in digital holographic microscopy

  • Chi-Ching Chang, Min-Tzung Shiu, Je-Chung Wang, and Yang-Kun Chew
  • received 05/01/2014; accepted 07/28/2014; posted 07/29/2014; Doc. ID 211256
  • [full text: PDF (7281) KB)]
  • Abstract: This study proposes a cost-effective, simple arbitrary phase-step digital holographic microscopy (APSDHM) as a basis to efficiently suppress both Zero-Order and Twin-Image Terms. Additionally, a virtual confocal offset lens under in-line configuration is used to compensate the introduced quadratic phase by microscope objective lens. The method proposed not only reduces the difficulties of physical confocal configurations, also greatly enhances the magnification power and achieving the purpose of any optical zoom. In order to reduce the noise interference of high magnification system, we also propose a long focal lens to reduce light detection size, gaining an approximately plane wave light source to illuminate the object within the effective depth of focus. The experimental results show that the high magnification system can be promoted at low noise interference, and image reconstruction without quadratic phase term.

Keywords (OCIS):

  • (090.0090) Holography : Holography
  • (100.5070) Image processing : Phase retrieval
  • (180.0180) Microscopy : Microscopy
  • (090.1995) Holography : Digital holography

Dynamics of CO2-laser pulse filamentation in air influenced by spectrally-selective molecular absorption

  • Yuri Geints and Alexander Zemlyanov
  • received 05/12/2014; accepted 07/28/2014; posted 07/29/2014; Doc. ID 211580
  • [full text: PDF (5356) KB)]
  • Abstract: The theoretical aspects of self-focusing and filamentation of high-power pulsed CO2-laser radiation with the carrier wavelength 10.6 µm in air are considered. The spectrally-selective molecular absorption of realistic atmospheric air is included in the theoretical model. In the conditions of strong pulse self-phase modulation and pulse spectral broadening the supercontinual radiation spectrum is substantially influenced by the selective atmospheric absorption that destabilizes the filamentation process and results in the considerable shortening of the filamentation length.

Keywords (OCIS):

  • (010.1300) Atmospheric and oceanic optics : Atmospheric propagation
  • (190.5330) Nonlinear optics : Photorefractive optics
  • (190.5940) Nonlinear optics : Self-action effects
  • (190.7110) Nonlinear optics : Ultrafast nonlinear optics

Non-null annular subaperture stitching interferometry for steep aspheric measurement

  • Lei Zhang, Dong Liu, Tu Shi, Yongying Yang, Hanshuo Wu, and Yibing Shen
  • received 06/19/2014; accepted 07/28/2014; posted 07/30/2014; Doc. ID 214349
  • [full text: PDF (4200) KB)]
  • Abstract: A non-null annular subaperture stitching interferometry (NASSI), combining the subaperture stitching ideal and non-null test method, is proposed for steep aspheric testing. Compared with standard annular subaperture stitching interferometry (ASSI), a partial null lens (PNL) is employed as an alternative to the transmission sphere, to generate different aspherical wavefronts as the references. The coverage subaperture number would be reduced greatly for the better performance of aspherical wavefronts in matching the local slope of aspheric surfaces. In this way, relatively large overlapping areas can be obtained for adjustment errors correction while the error accumulation would be decreased. With the reverse optimization reconstruction (ROR) method for retrace error correction, the figure error of each subaperture can be retrieved accurately. Therefore, the testing accuracy and efficiency are thus increased. The dynamic test range is extended as well. A numerical simulation exhibits the comparison of the performance of the NASSI and standard ASSI, which demonstrates the high accuracy of the NASSI in testing steep aspheric. Experimental results of NASSI are shown to be in good agreement with those of Zygo interferometer.

Keywords (OCIS):

  • (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
  • (120.3180) Instrumentation, measurement, and metrology : Interferometry
  • (120.4570) Instrumentation, measurement, and metrology : Optical design of instruments
  • (120.6650) Instrumentation, measurement, and metrology : Surface measurements, figure

Confocal Pore Size Measurement Based on Super-Resolution Image Restoration

  • Dali Liu, Yun Wang, Lirong Qiu, and Weiqian Zhao
  • received 02/18/2014; accepted 07/27/2014; posted 07/28/2014; Doc. ID 206722
  • [full text: PDF (2651) KB)]
  • Abstract: A confocal pore size measurement based on the super-resolution image restoration is proposed to obtain a fast and accurate measurement for submicron pore size of nuclear track-etched membranes (NTEMs). This method facilitates the on-line inspection of the pore size evolution during etching. Combining confocal microscopy with super-resolution image restoration significantly improves the lateral resolution of the NTEM image, yields a reasonable circle edge-setting criterion of 0.255, and achieves precise pore edge detection. Theoretical analysis shows that the minimum measuring diameter can reach 0.16 μm, and the root mean square of the residuals is only 5 nm. Edge response simulation and experiment reveal that the edge response of the proposed method is better than 100 nm. The NTEM pore size measurement results obtained by the proposed method agree well with that obtained by scanning electron microscopy.

Keywords (OCIS):

  • (100.3020) Image processing : Image reconstruction-restoration
  • (100.6640) Image processing : Superresolution
  • (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
  • (120.4630) Instrumentation, measurement, and metrology : Optical inspection
  • (120.6650) Instrumentation, measurement, and metrology : Surface measurements, figure
  • (180.1790) Microscopy : Confocal microscopy

A Dictionary Learning Approach for Image Deconvolution with Variance Estimation

  • Hang Yang, Ming Zhu, Xiaotian Wu, Zhongbo Zhang, and Heyan Huang
  • received 04/24/2014; accepted 07/27/2014; posted 07/28/2014; Doc. ID 210786
  • [full text: PDF (1416) KB)]
  • Abstract: In this paper, we propose a new dictionary learning approach for image deconvolution, which effectively integrates the Fourier regularization and dictionary learning technique into the deconvolution framework. Specifically, we propose an efficient iterative algorithm with the decouple of deblurring and denoising steps in the restoration process. In deblurring step, we involve a regularized inversion of the blur in Fourier domain. Then we remove the colored noise using a dictionary learning method in the denoising step. In the denoising step, we propose an approach to update the estimation of noise variance for dictionary learning. We will show that this approach outperforms several state-of-the-art image deconvolution methods in terms of ISNR and visual quality.

Keywords (OCIS):

  • (100.0100) Image processing : Image processing
  • (100.1830) Image processing : Deconvolution
  • (100.3020) Image processing : Image reconstruction-restoration
  • (100.3190) Image processing : Inverse problems

(DH3D) Novel applications of digital holographic microscopy in therapeutic evaluation of Chinese herbal medicines

  • Chung-Hsin Wu, Xin-Ji Lai, Chau-Jern Cheng, Yu-Chen Yu, and Chun-Yen Chang
  • received 04/28/2014; accepted 07/27/2014; posted 07/28/2014; Doc. ID 210822
  • [full text: PDF (1970) KB)]
  • Abstract: The therapeutic use of Chinese herbal medicines (CHMs) is a new approach to treat neurodegenerative diseases, such as Alzheimer’s diseases and Parkinson’s disease. The detection of soma volume and neurite outgrowth of living neurons is a highly relevant biomarker related to various application fields, including therapy efficacy and drug safety evaluation. Through the use of digital holographic microscopy (DHM), we evaluate the therapeutic effect of CHMs in curing neurodegeneration. Panax ginseng has been used in traditional Chinese herbal medicine for centuries. In this study, DHM is applied to monitor the three-dimensional morphology change of retinoic acid-induced human neuroblastoma SH-SY5Y cells during Panax ginseng treatment. We demonstrate the capability of DHM to detect non-invasively SH-SY5Y cell apoptosis and rescue through the measurement of neuronal volume and neurite outgrowth regulation without any labeling reagent. Through DHM, we observe the phase images of the rapidly shrinking cells with decreasing soma volume and shorting neurite outgrowth during glutamate treatments. The shrinkage in glutamate-induced cells is significantly alleviated during Panax ginseng treatment. The results, through DHM, are consistent with the result from MTT assay for assessing cell viability during Panax ginseng treatment. These findings suggest that the novel application of DHM for measuring soma volume and neurite outgrowth of living neurons is appropriate for the therapeutic evaluation of CHMs.

Keywords (OCIS):

  • (170.0170) Medical optics and biotechnology : Medical optics and biotechnology
  • (170.1530) Medical optics and biotechnology : Cell analysis
  • (090.1995) Holography : Digital holography

Bi-photonic holographic grating recordings for different polarization configurations in spirooxazine-doped polymers

  • Meiling Zheng, Xin Xie, Zhiying Zhang, Feng Shi, Xiuli Wang, Shencheng Fu, and Yichun Liu
  • received 04/28/2014; accepted 07/27/2014; posted 07/28/2014; Doc. ID 210968
  • [full text: PDF (1768) KB)]
  • Abstract: Spirooxazine doped polymers exhibited fast photochromism response and high polarization sensitivity after the irradiation in short-wavelength range. Based on such properties, holographic grating recordings accompanying with a linearly polarized blue-violet beam (405 nm) in the photochromic film were performed by two coherent green beams (532 nm) for s-s, p-p, s-p, left to right circular polarization (LCP-RCP) and right to right circular polarization (RCP-RCP). Under the bi-photonic action of 405nm and 532nm, temporal evolution of diffraction efficiency was strongly dependent on polarization configuration of the recording beams. It was found the blue-violet irradiation plays double roles in holographic recordings: generation of merocyanine aggregation and induction of anisotropy. The experimental results were precisely fitted with a phenomenological model, assuming the simultaneous formation of one absorption grating induced by the 532 nm light and two coupled phase gratings generated from the refractive index changes by recording and auxiliary beams. The existences of absorption and phase gratings were proved by observing the florescence emission of holographic gratings and testing the dependence of diffraction efficiency on the reading beam polarization state, respectively. The results provided a good deal of insight into photochromic behavior of spirooxazine in polymers and made a new range of applications in the field of high-density optical storage.

Keywords (OCIS):

  • (050.1950) Diffraction and gratings : Diffraction gratings
  • (090.2900) Holography : Optical storage materials
  • (210.4810) Optical data storage : Optical storage-recording materials
  • (260.1440) Physical optics : Birefringence

(ODT2014) A front view and panoramic side view videoscope lens system design

  • Chen-Hung Lin, Li-Jen Hsiao, Jing-Ting Hsiao, and Hoang Yan Lin
  • received 05/02/2014; accepted 07/27/2014; posted 07/28/2014; Doc. ID 211255
  • [full text: PDF (1197) KB)]
  • Abstract: A novel structure of a rigid panoramic endoscope is designed and presented. The inspected target field is imaged on the sensor by an optical lens with a dynamic mechanical module. A micro gear and motor are used to drive the dynamic lens components, and a compensation element is used in the system to correct the aberrations due to the protective cylindrical endoscope cover. A long depth of field navigator lens is attached, to image the front side. The design detail is presented and result is shown.

Keywords (OCIS):

  • (110.0110) Imaging systems : Imaging systems
  • (170.3660) Medical optics and biotechnology : Light propagation in tissues
  • (110.3010) Imaging systems : Image reconstruction techniques

Estimation of the refractive index structure parameter from single-level daytime routine weather data

  • A. Boer, A. F. Moene, A. Graf, C. Simmer, and A. A. M. Holtslag
  • received 05/12/2014; accepted 07/25/2014; posted 07/29/2014; Doc. ID 211869
  • [full text: PDF (1427) KB)]
  • Abstract: Atmospheric scintillations cause problems for applications where an undistorted propagation of electromagnetic radiation is essential. These scintillations are related to turbulent fluctuations of temperature and humidity that are in turn related to surface heat fluxes. We developed an approach that quantifies these scintillations by estimating Cn2 from surface fluxes that are derived from single-level routine weather data. This approach allows for an efficient evaluation of the performance of e.g. infrared imaging systems, laser geodetic systems, and ground-to-satellite optical communication systems. We tested our approach for two grass fields in central and southern Europe, and for a wheat field in central Europe. Although there are uncertainties in the flux estimates, the impact on Cn2 is shown to be rather small. The Cn2 daytime estimates agree well with values determined from eddy covariance measurements for the application to the three fields. However, some adjustments were needed for the approach for the grass field in southern Europe because of dominant boundary-layer processes instead of surface-layer processes.

Keywords (OCIS):

  • (010.1300) Atmospheric and oceanic optics : Atmospheric propagation
  • (010.1330) Atmospheric and oceanic optics : Atmospheric turbulence
  • (010.3310) Atmospheric and oceanic optics : Laser beam transmission
  • (010.3920) Atmospheric and oceanic optics : Meteorology
  • (010.7295) Atmospheric and oceanic optics : Visibility and imaging
  • (010.0280) Atmospheric and oceanic optics : Remote sensing and sensors

Focal length measurement based on the wavefront difference method by a Fizeau interferometer

  • Zhongming Yang, Zhishan Gao, Jiantai Dou, and Xinxing Wang
  • received 05/21/2014; accepted 07/25/2014; posted 07/25/2014; Doc. ID 212360
  • [full text: PDF (967) KB)]
  • Abstract: A method for measuring the focal length of the lens by a Fizeau interferometer is proposed. Based on the Gaussian imaging equation and the longitudinal displacements of the object point and image point, a precise formula for focal length calculation is deduced. The longitudinal displacement of the object points is determined by the wavefront difference method with subnanometer accuracy. An experimental system for focal length measurements is set up to verify the principle. The sources of uncertainty in measurement are discussed. Both the positive and negative lens experimental results indicate that the measurement accuracy is less than under normal experimental environment.

Keywords (OCIS):

  • (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
  • (120.3180) Instrumentation, measurement, and metrology : Interferometry
  • (120.3930) Instrumentation, measurement, and metrology : Metrological instrumentation
  • (120.3940) Instrumentation, measurement, and metrology : Metrology

A Simple and Efficient Approach for Restoration of Non-Uniformly Warped Images

  • Kalyan Halder, Murat Tahtali, and Sreenatha Anavatti
  • received 05/30/2014; accepted 07/25/2014; posted 07/25/2014; Doc. ID 212786
  • [full text: PDF (5353) KB)]
  • Abstract: A high accuracy image dewarping method is proposed to restore the image from a non-uniformly warped video sequence degraded by atmospheric turbulence. This approach contains three major steps. First, a non-rigid image registration technique is employed to register all the frames in the sequence to a reference frame and estimate the motion fields. Second, an iterative First Register Then Average And Subtract (iFRTAAS) method is applied to correct the geometric deformations of the warped frames. The third step involves applying a non-local means filter for the compensation of noise and improve the Signal-to-Noise Ratio (SNR) of the restored reference frame. Simulations are carried out by applying the method to synthetic and real-life turbulence degraded videos and by determining various quality metrics. A performance comparison is presented between the proposed method and two earlier methods, which verifies that the proposed method provides significant improvement on the image restoration accuracy.

Keywords (OCIS):

  • (010.1330) Atmospheric and oceanic optics : Atmospheric turbulence
  • (100.2000) Image processing : Digital image processing
  • (100.3020) Image processing : Image reconstruction-restoration
  • (110.6770) Imaging systems : Telescopes
  • (350.1270) Other areas of optics : Astronomy and astrophysics

Synthetic aperture ladar imaging demonstrations and information at very low return levels

  • Zeb Barber and Jason Dahl
  • received 05/28/2014; accepted 07/25/2014; posted 07/25/2014; Doc. ID 212966
  • [full text: PDF (632) KB)]
  • Abstract: We present synthetic aperture ladar (SAL) imaging demonstrations where the return signal level from the target is near the single photon level per resolved pixel. Scenes consisting of both specular point targets and diffuse reflection, fully speckled, targets are studied. Artificial retro-reflector based phase references and/or phase gradient autofocus (PGA) algorithms were utilized for compensation of phase errors during the aperture motion. It was found that SAL images could reliably be formed with both methods even when the final max pixel intensity was at the few photon level which means the SNR before azimuth compression is below unity. Mutual information based comparison of SAL images show that average mutual information is reduced when the PGA is utilized for image based phase compensation. The photon information efficiency of SAL and coherent imaging is discussed.

Keywords (OCIS):

  • (030.0030) Coherence and statistical optics : Coherence and statistical optics
  • (110.6880) Imaging systems : Three-dimensional image acquisition
  • (280.3400) Remote sensing and sensors : Laser range finder
  • (280.6730) Remote sensing and sensors : Synthetic aperture radar
  • (110.3055) Imaging systems : Information theoretical analysis

Spiral phase plate based on polymer dispersed liquid crystal for wide visible band applications

  • Shing-Trong Wu and Andy Y.-G. Fuh
  • received 06/20/2014; accepted 07/25/2014; posted 07/25/2014; Doc. ID 213996
  • [full text: PDF (638) KB)]
  • Abstract: This study demonstrates the helical wave fronts via a spiral phase plate (SPP) based on polymer dispersed liquid crystals (PDLCs). Because the PDLC is electric tunable, the plate can be used in a wide visible band. In addition, if the probe beam deviates from the center of the sample, some of the lights propagate out of the sectors. We propose some of the application for the results.

Keywords (OCIS):

  • (160.3710) Materials : Liquid crystals
  • (160.5470) Materials : Polymers
  • (050.4865) Diffraction and gratings : Optical vortices

(ODT2014) Design of freeform lens for LED light with high efficiency and uniform illumination

  • Nguyen Doan Anh, Min-Feng Lai, Hsin-Yi Ma, and Hsiao-Yi Lee
  • received 05/01/2014; accepted 07/25/2014; posted 07/25/2014; Doc. ID 211258
  • [full text: PDF (987) KB)]
  • Abstract: A freeform secondary lens is proposed to optimize a LED light. Based on Snell’s law, energy conservation law and Monte Carlo ray tracing algorithm, the surface contour of the freeform lens can be determined according to the requirements of a LED light. The optical experimental results show that the optical efficiency 95.69% can be achieved by the lens, which illumination uniformity 0.317 is higher than the commercial one 0.259. The lens does not need the help of a white ring holder, so the cost of LED light can become effective.

Keywords (OCIS):

  • (220.0220) Optical design and fabrication : Optical design and fabrication
  • (230.3670) Optical devices : Light-emitting diodes

Scalar wave-optical reconstruction of plenoptic camera images

  • André Junker, Tim Stenau, and Karl-Heinz Brenner
  • received 05/15/2014; accepted 07/24/2014; posted 07/25/2014; Doc. ID 211995
  • [full text: PDF (5823) KB)]
  • Abstract: We investigate the reconstruction of plenoptic camera images in a scalar wave-optical framework. Previous publications relating to this topic numerically simulate light propagation on the basis of ray tracing. However, due to continuing miniaturization of hardware components it can be assumed that in combination with low aperture optical systems this technique may not be generally valid. Therefore, we study the differences between ray- and wave-optical object reconstructions of true plenoptic camera images. For this purpose we present a wave-optical reconstruction algorithm, which can be run on a regular computer. Our findings show that a wave-optical treatment is capable of increasing the detail resolution of reconstructed objects.

Keywords (OCIS):

  • (070.2580) Fourier optics and signal processing : Paraxial wave optics
  • (100.3010) Image processing : Image reconstruction techniques
  • (100.6640) Image processing : Superresolution
  • (150.6910) Machine vision : Three-dimensional sensing
  • (110.1758) Imaging systems : Computational imaging
  • (070.7345) Fourier optics and signal processing : Wave propagation

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