Optical design and testing: introduction Chao-Wen Liang,1 John Koshel,2 Jose Sasian,2 Robert Breault,3 Yongtian Wang,4 and Yi Chin Fang5,* 1
Department of Optics and Photonics, National Central University, Jhongli City 32001, Taiwan 2
College of Optical Science, Arizona University, Tucson, Arizona 85721, USA 3
4 5
Breault Research, Tucson, Arizona 85717, USA
School of Optoelectronics Beijing Institute of Technology, Beijing 100081, China
National Kaohsiung First University of Science and Technology, Kaohsiung 811, Taiwan *Corresponding author: [email protected] Received 1 October 2014; posted 1 October 2014 (Doc. ID 224286); published 9 October 2014
Optical design and testing has numerous applications in industrial, military, consumer, and medical settings. Assembling a complete imaging or nonimage optical system may require the integration of optics, mechatronics, lighting technology, optimization, ray tracing, aberration analysis, image processing, tolerance compensation, and display rendering. This issue features original research ranging from the optical design of image and nonimage optical stimuli for human perception, optics applications, bio-optics applications, 3D display, solar energy system, opto-mechatronics to novel imaging or nonimage modalities in visible and infrared spectral imaging, modulation transfer function measurement, and innovative interferometry. © 2014 Optical Society of America OCIS codes: (220.4840) Testing; (000.1200) Announcements, awards, news, and organizational activities; (220.0220) Optical design and fabrication. http://dx.doi.org/10.1364/AO.53.00ODT1
Optical design and testing has numerous applications in industrial, military, consumer, and medical settings. Basically, there are two different types of optical design: large optics and micro-optics. From the standpoint of system output, image optics and nonimage optics can be distinguished. Assembling a complete micro-optical system, even nonimage optics or image optics, requires the integration of optics, mechatronics, fast Fourier optics transformation, optimization, aberration simulation, image processing, tolerance compensation, and light source and display rendering. From the other standpoint, large optics requires optics, materials, polarization analysis, ray tracing, and tolerance analysis and mechanisms. This feature issue is aimed at scientists, engineers, and practitioners interested in understanding how 1559-128X/14/29ODT1-04$15.00/0 © 2014 Optical Society of America
different materials and components can combine with optimization to determine and influence image or nonimage system performance. The design of optical systems must factor in the system as an integrated unit and optimize the performance for a given application. In addition, Optics Next, which furthers optical design and testing, or, we could say, the optics of the next generation, with its new concepts, might be first revealed in this special issue. Numerous disciplines are required for the design and advancement of optical systems in the next generation. These disciplines include discrete mathematics, fractured pupil, MEMS, digital signal processing, discrete optical detection, computational, adaptives, and compressive imaging, 3D displays, new optimization and algorithmic methods, and advanced interferometry; they all contribute to defining Optics Next, the coming generation of optics. At Optics and Photonics Taiwan 2013, scientists and engineers from commercial, 10 October 2014 / Vol. 53, No. 29 / APPLIED OPTICS
ODT1
academic, and military disciplines came together to share advances in imaging and nonimage systems. This issue contains a subset of the high-quality work presented at this meeting as well as some contributions from the wider imaging, nonimage, and optical testing systems community. These papers cover a broad spectrum of theoretical and experimental investigations in optical systems design, testing, and applications. In this collection of papers, you will find research on a computational modulation transfer function for Nyquist sampled imaging sensors; micro-optics integrated with MEMs and free-form optical arrays applied to a nonimage solar energy system; fundamental aberration theory of optical design for zoom optics; adaptive optical solutions for human vision models with genetic algorithms; tolerance analysis via Taguchi models; the secondary optical design of LED and its application to automotive lighting, tunnel lighting and projectors; pupillometers applied to diabetics; an introduction to a newly developed laser acupuncture system; the optical design of smart phone cameras and panoramic videoscope cameras; and a liquid crystal element applied to an optical storage system; in addition, some innovative interferometry and LED measurement are introduced in this special issue. Ching-Cherng Sun et al. present a tunnel lighting design consisting of a cluster light-emitting diode and a free-form lens. Compared with traditional fluorescent lamps, the proposed luminaire, of which the optical utilization factor, optical efficiency, and uniformity are, respectively, 44%, 92.5%, and 0.72, exhibits favorable performance in energy saving, glare reduction, and traffic safety. Pin Han et al. demonstrate a design strategy for refractive lenses that offers high uniformity illumination and good directivity. The simulation results show that the uniformity of the illumination can reach over 80%, and the diverging angle can be less than 3° for an appropriate partition number. Jyh-Cheng Yu et al. investigate the optical design of planar curved LED end-lit light bars using v cuts as light-diverting structures. This study addresses the design of planar curved LED end-lit light bars and the optimization scheme for illuminance uniformity. V cuts are used as the optical coupling features, and the lead angles of the v cuts are varied to achieve optimum axial luminous intensity. Shang pin Ying et al. introduce a phosphorconverted light-emitting diode with a curved remote phosphor layer; by changing the geometry of the flat remote phosphor layer in a conventional remote phosphor structure, the package extraction efficiency and luminous efficacy of the curved remote phosphor structure were improved. Hsiao-Yi Lee et al. propose a free-form secondary lens to be optimized as an LED. The surface contour of the free-form lens can be determined according to the requirements of an LED. Optical experimental results show that an optical efficiency of 95.69% can be achieved by the lens, of which the illumination uniformity is 0.317. ODT2
APPLIED OPTICS / Vol. 53, No. 29 / 10 October 2014
Wen-Shing Sun et al. simulate and compare the illuminance, uniformity, and efficiency of metal-halide lamps, white LED light sources, and hybrid light box designs combining sunlight and white LED lighting used for indoor basketball court illumination. Mang Ou Yang et al. present a novel wearable pupillometer design, without external light artifacts, and an embedded algorithm with blinking elimination, which investigates autonomic neuropathy through recording pupil dynamics triggered by an external sensitive invisible light source. These parameters obtain over 85% sensitivity, 83% specificity, and 88% accuracy. The pupillometer is proven reliable, effective, portable, and inexpensive for diagnosing diabetes in an early stage. This paper was the subject of an OSA press release. Ou-Yang et al. use the highfrequency component of the spectral power of accommodative microfluctuations as a major objective indicator for analyzing the effects of visual fatigue based on various displays, such as colorformation and 3D displays. Chih-Yu Wang et al. develop a novel laser-acupuncture system that can be used to implement the manipulation methods of traditional acupuncture, such as lifting and thrusting. A 780 nm laser diode with a maximum power of 90 mW was used as the light source. The result is consistent with traditional acupuncture in that acupuncture incorporating lift and thrust is more effective than that without lift and thrust. Bo-Wen Wu presents research that applied the eye model and Taguchi experiment method, combined with design optimization for a hyperbolic-aspherical lens, to significantly reduce the lens thickness by more than 30%, outperforming the average thickness reduction in a general aspherical lens. Jose Sasian et al. present an accurate method to determine smartphone camera lens distortion to an estimated average error of 0.09%. Yongtian Wang et al. design and develop such a holographic HUD system with a large asymmetric field of view (FOV) while maintaining good image quality. Experimental results demonstrate that this prototype achieves a total FOV of 30°horizontal × 24°vertical, a resolution of 1280 × 1024, and a 5% distortion. Wen-Shing Sun et al. propose an optical design of a compact LED projector. By using a new TIR prism and projection lens, the whole optical engine is smaller in size and has a higher contrast ratio for image quality. In this design, the uniformity of the screen reaches more than 82%, and the efficiency increases by more than 44%. Hoang Yan Lin et al. present a novel structure of a rigid panoramic endoscope. The inspected target field is imaged on the sensor by an optical lens with a dynamic mechanical module. A microgear 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. Guo-Dung Su et al. used a deformable mirror (DM) as a reflecting element in an optical zoom system and
polydimethylsiloxane as a deformable membrane that can achieve a large stroke. The optical zoom module consists of a pair of micromachined deformable mirrors. The thickness of this module is 10 mm in optical design to achieve 2× optical zoom; the f -number is 6.4. Su et al. propose a wide-angle and thin camera module integrating the principles of an insect’s compound eye and the human eye, mimicking them with a curved hexagonal microlens array and a hemispherical lens, respectively. Victor V. Belyaev et al. suggest a liquid crystal (LC) director configuration for its application in optical compensators. Design and fabrication methods of hybrid aligned nematic (HAN) cells with an arbitrary LC pretilt angle are described. The LC pretilt angle is measured in the HAN cells with a given planar or vertical LC alignment on one of the substrates. Chaohsien Chen proposed algebraic algorithms provide a more efficient and complete method than do earlier algorithms adopting scanning procedures for complete solutions of zoom curves of three-component zoom lenses with the second component fixed. Chen proposed methods of solving aspheric singlets and cemented doublets with given primary aberrations. Rung-Sheng Chen develops a straightforward rigorous and flexible computational method to determine the coordinate points on an aspheric surface. An extension of the basic SPMbased method is used to generalize the development of the catadioptric collimator surfaces to illustrate this general algorithm for aspheric surface design for an extended LED light source. Jung-Hung Sun demonstrated a method of tolerance reallocation for an optical zoom lens design based on the indicated specifications and correspondent tolerances by the optical design software. In his paper, the investigation of applying the Taguchi method of focusing on MTF, DST, and RI was successfully adopted to reallocate tolerance; the process could be suitable for focusing on other image quality selection. Chih-Ta Yen et al. propose 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 pickup lens design, this new optical design delivers performance as good as the conventional one but has more room for tolerance control, which plays a role in antishaking devices, such as portable Blu-ray players. Allen Jong-Woei Whang et al. simulate a multicurvature lens to collimate rays propagated from different angles and describes a method based on a free-form microlens array, which increases transmission efficiency. Results show that with the free-form microlens array collimator, the light propagates at least 50.26% parallel, and the efficiency increases by 24.76%, enhancing the core values of the daylighting system in building illumination. Allen Jong-Woei Whang et al. investigate the design of a heliostat that reflects sunlight vertically onto a daylighting system. This study proposes a 3 × 3 mirror matrix heliostat, which is different from the traditional heliostat with one single mirror. With the
heliostat, the system efficiency increases as high as 3.32 times. Chao-Wen Liang et al. propose a newly developed high overlapping density stitching interferometer, which is also proved to effectively reduce measurement uncertainty and improve measurement quality. Liang et al. discuss the use of high overlapping density subaperture stitching interferometry to reduce the impact of reference optics errors on the stitched phase. The tested optics surface deformation phase is determined by averaging the multiple subaperture measurements taken at different rotational angles. The simulation shows that the high overlapping density subaperture stitching interferometry can effectively reduce the stitched phase errors that are due to either the static or dynamic reference optics errors. Sivan Isaacs et al. propose a simplified analytic expression for the propagation matrix, which is derived for the case of nematic liquid crystal in the homogeneous geometry for LC Fabry–Perot tunable filters. The effects of dephasing originating from wedge or noncollimated light beams are investigated. Finally, more detailed experimental results of our polarization-independent configuration are given, which uses polarization diversity with a Wollaston prism. King Ung Hii et al. demonstrate a quadruple-pass lateral shearing interferometer by introducing a single mirror into the conventional double-pass system for collimation-based applications. The proposed system can be utilized for refraction-based and reflectionbased applications that depend on a test arm with a convergent beam. Mohammad Solaiman et al. discuss various dispersion compensation methods including design and evaluation, seeking a cost-effective technique with remarkable dispersion compensation percentage and pulse shape. The joint technique achieved the optimum dispersion compensation percentage among all evaluated techniques to reach 96.36%, remarkable pulse shape, and relatively lower cost compared with DCF but still more expensive than chirped Tanh FBG. Wenjiang Guo et al. propose and develop a new reference-free beam-sampling (RFBS) methodology and system for this particular application. It is shown that a ten of nanometers measurement accuracy is achieved, even for surfaces with a peak valley value of more than 1 mm. The feasibility and effectiveness of the RFBS methodology are proven. Chun-Liu Zhao et al. propose a reflective long-period grating-based sensor with a Sagnac fiber loop mirror (SFLM) for simultaneous measurement of refractive index (RI) and temperature. The application for 40 km long-distance RI and temperature measurement shows that the sensor has potential application in long-distance sensing. Shang-Ping Ying et al. propose the output power measurement of bare-wafer/chip light-emitting diodes (LED) using a large-area silicon (Si) photodiode with a simple structure and high accuracy relative to the conventional partial flux measurement using an integrating sphere. As a result, the large-area Si photodiode 10 October 2014 / Vol. 53, No. 29 / APPLIED OPTICS
ODT3
method practically reduces the output power measurement deviations of the bare-wafer/chip LED, so that high-accuracy measurement can be achieved in the mass production of the bare-wafer/chip LED without the complicated integrating sphere structure. Chuen-Lin Tien et al. propose a hybrid and flexible interference microscope combined with different phase algorithms to measure the surface roughness
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APPLIED OPTICS / Vol. 53, No. 29 / 10 October 2014
of thin films. The experimental results show that the proposed approach is feasible in determining the 3D deformation and surface roughness of thin films. HoLin Tsay et al. propose a newly developed fast measurement of a modulation transfer function (MTF) optical system inclusive of on- and off-axis measurement and then suggest there is nothing different for off- and on-axis measurement during microscanning.
Department of Optics and Photonics, National Central University, Jhongli City 32001, Taiwan 2
College of Optical Science, Arizona University, Tucson, Arizona 85721, USA 3
4 5
Breault Research, Tucson, Arizona 85717, USA
School of Optoelectronics Beijing Institute of Technology, Beijing 100081, China
National Kaohsiung First University of Science and Technology, Kaohsiung 811, Taiwan *Corresponding author: [email protected] Received 1 October 2014; posted 1 October 2014 (Doc. ID 224286); published 9 October 2014
Optical design and testing has numerous applications in industrial, military, consumer, and medical settings. Assembling a complete imaging or nonimage optical system may require the integration of optics, mechatronics, lighting technology, optimization, ray tracing, aberration analysis, image processing, tolerance compensation, and display rendering. This issue features original research ranging from the optical design of image and nonimage optical stimuli for human perception, optics applications, bio-optics applications, 3D display, solar energy system, opto-mechatronics to novel imaging or nonimage modalities in visible and infrared spectral imaging, modulation transfer function measurement, and innovative interferometry. © 2014 Optical Society of America OCIS codes: (220.4840) Testing; (000.1200) Announcements, awards, news, and organizational activities; (220.0220) Optical design and fabrication. http://dx.doi.org/10.1364/AO.53.00ODT1
Optical design and testing has numerous applications in industrial, military, consumer, and medical settings. Basically, there are two different types of optical design: large optics and micro-optics. From the standpoint of system output, image optics and nonimage optics can be distinguished. Assembling a complete micro-optical system, even nonimage optics or image optics, requires the integration of optics, mechatronics, fast Fourier optics transformation, optimization, aberration simulation, image processing, tolerance compensation, and light source and display rendering. From the other standpoint, large optics requires optics, materials, polarization analysis, ray tracing, and tolerance analysis and mechanisms. This feature issue is aimed at scientists, engineers, and practitioners interested in understanding how 1559-128X/14/29ODT1-04$15.00/0 © 2014 Optical Society of America
different materials and components can combine with optimization to determine and influence image or nonimage system performance. The design of optical systems must factor in the system as an integrated unit and optimize the performance for a given application. In addition, Optics Next, which furthers optical design and testing, or, we could say, the optics of the next generation, with its new concepts, might be first revealed in this special issue. Numerous disciplines are required for the design and advancement of optical systems in the next generation. These disciplines include discrete mathematics, fractured pupil, MEMS, digital signal processing, discrete optical detection, computational, adaptives, and compressive imaging, 3D displays, new optimization and algorithmic methods, and advanced interferometry; they all contribute to defining Optics Next, the coming generation of optics. At Optics and Photonics Taiwan 2013, scientists and engineers from commercial, 10 October 2014 / Vol. 53, No. 29 / APPLIED OPTICS
ODT1
academic, and military disciplines came together to share advances in imaging and nonimage systems. This issue contains a subset of the high-quality work presented at this meeting as well as some contributions from the wider imaging, nonimage, and optical testing systems community. These papers cover a broad spectrum of theoretical and experimental investigations in optical systems design, testing, and applications. In this collection of papers, you will find research on a computational modulation transfer function for Nyquist sampled imaging sensors; micro-optics integrated with MEMs and free-form optical arrays applied to a nonimage solar energy system; fundamental aberration theory of optical design for zoom optics; adaptive optical solutions for human vision models with genetic algorithms; tolerance analysis via Taguchi models; the secondary optical design of LED and its application to automotive lighting, tunnel lighting and projectors; pupillometers applied to diabetics; an introduction to a newly developed laser acupuncture system; the optical design of smart phone cameras and panoramic videoscope cameras; and a liquid crystal element applied to an optical storage system; in addition, some innovative interferometry and LED measurement are introduced in this special issue. Ching-Cherng Sun et al. present a tunnel lighting design consisting of a cluster light-emitting diode and a free-form lens. Compared with traditional fluorescent lamps, the proposed luminaire, of which the optical utilization factor, optical efficiency, and uniformity are, respectively, 44%, 92.5%, and 0.72, exhibits favorable performance in energy saving, glare reduction, and traffic safety. Pin Han et al. demonstrate a design strategy for refractive lenses that offers high uniformity illumination and good directivity. The simulation results show that the uniformity of the illumination can reach over 80%, and the diverging angle can be less than 3° for an appropriate partition number. Jyh-Cheng Yu et al. investigate the optical design of planar curved LED end-lit light bars using v cuts as light-diverting structures. This study addresses the design of planar curved LED end-lit light bars and the optimization scheme for illuminance uniformity. V cuts are used as the optical coupling features, and the lead angles of the v cuts are varied to achieve optimum axial luminous intensity. Shang pin Ying et al. introduce a phosphorconverted light-emitting diode with a curved remote phosphor layer; by changing the geometry of the flat remote phosphor layer in a conventional remote phosphor structure, the package extraction efficiency and luminous efficacy of the curved remote phosphor structure were improved. Hsiao-Yi Lee et al. propose a free-form secondary lens to be optimized as an LED. The surface contour of the free-form lens can be determined according to the requirements of an LED. Optical experimental results show that an optical efficiency of 95.69% can be achieved by the lens, of which the illumination uniformity is 0.317. ODT2
APPLIED OPTICS / Vol. 53, No. 29 / 10 October 2014
Wen-Shing Sun et al. simulate and compare the illuminance, uniformity, and efficiency of metal-halide lamps, white LED light sources, and hybrid light box designs combining sunlight and white LED lighting used for indoor basketball court illumination. Mang Ou Yang et al. present a novel wearable pupillometer design, without external light artifacts, and an embedded algorithm with blinking elimination, which investigates autonomic neuropathy through recording pupil dynamics triggered by an external sensitive invisible light source. These parameters obtain over 85% sensitivity, 83% specificity, and 88% accuracy. The pupillometer is proven reliable, effective, portable, and inexpensive for diagnosing diabetes in an early stage. This paper was the subject of an OSA press release. Ou-Yang et al. use the highfrequency component of the spectral power of accommodative microfluctuations as a major objective indicator for analyzing the effects of visual fatigue based on various displays, such as colorformation and 3D displays. Chih-Yu Wang et al. develop a novel laser-acupuncture system that can be used to implement the manipulation methods of traditional acupuncture, such as lifting and thrusting. A 780 nm laser diode with a maximum power of 90 mW was used as the light source. The result is consistent with traditional acupuncture in that acupuncture incorporating lift and thrust is more effective than that without lift and thrust. Bo-Wen Wu presents research that applied the eye model and Taguchi experiment method, combined with design optimization for a hyperbolic-aspherical lens, to significantly reduce the lens thickness by more than 30%, outperforming the average thickness reduction in a general aspherical lens. Jose Sasian et al. present an accurate method to determine smartphone camera lens distortion to an estimated average error of 0.09%. Yongtian Wang et al. design and develop such a holographic HUD system with a large asymmetric field of view (FOV) while maintaining good image quality. Experimental results demonstrate that this prototype achieves a total FOV of 30°horizontal × 24°vertical, a resolution of 1280 × 1024, and a 5% distortion. Wen-Shing Sun et al. propose an optical design of a compact LED projector. By using a new TIR prism and projection lens, the whole optical engine is smaller in size and has a higher contrast ratio for image quality. In this design, the uniformity of the screen reaches more than 82%, and the efficiency increases by more than 44%. Hoang Yan Lin et al. present a novel structure of a rigid panoramic endoscope. The inspected target field is imaged on the sensor by an optical lens with a dynamic mechanical module. A microgear 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. Guo-Dung Su et al. used a deformable mirror (DM) as a reflecting element in an optical zoom system and
polydimethylsiloxane as a deformable membrane that can achieve a large stroke. The optical zoom module consists of a pair of micromachined deformable mirrors. The thickness of this module is 10 mm in optical design to achieve 2× optical zoom; the f -number is 6.4. Su et al. propose a wide-angle and thin camera module integrating the principles of an insect’s compound eye and the human eye, mimicking them with a curved hexagonal microlens array and a hemispherical lens, respectively. Victor V. Belyaev et al. suggest a liquid crystal (LC) director configuration for its application in optical compensators. Design and fabrication methods of hybrid aligned nematic (HAN) cells with an arbitrary LC pretilt angle are described. The LC pretilt angle is measured in the HAN cells with a given planar or vertical LC alignment on one of the substrates. Chaohsien Chen proposed algebraic algorithms provide a more efficient and complete method than do earlier algorithms adopting scanning procedures for complete solutions of zoom curves of three-component zoom lenses with the second component fixed. Chen proposed methods of solving aspheric singlets and cemented doublets with given primary aberrations. Rung-Sheng Chen develops a straightforward rigorous and flexible computational method to determine the coordinate points on an aspheric surface. An extension of the basic SPMbased method is used to generalize the development of the catadioptric collimator surfaces to illustrate this general algorithm for aspheric surface design for an extended LED light source. Jung-Hung Sun demonstrated a method of tolerance reallocation for an optical zoom lens design based on the indicated specifications and correspondent tolerances by the optical design software. In his paper, the investigation of applying the Taguchi method of focusing on MTF, DST, and RI was successfully adopted to reallocate tolerance; the process could be suitable for focusing on other image quality selection. Chih-Ta Yen et al. propose 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 pickup lens design, this new optical design delivers performance as good as the conventional one but has more room for tolerance control, which plays a role in antishaking devices, such as portable Blu-ray players. Allen Jong-Woei Whang et al. simulate a multicurvature lens to collimate rays propagated from different angles and describes a method based on a free-form microlens array, which increases transmission efficiency. Results show that with the free-form microlens array collimator, the light propagates at least 50.26% parallel, and the efficiency increases by 24.76%, enhancing the core values of the daylighting system in building illumination. Allen Jong-Woei Whang et al. investigate the design of a heliostat that reflects sunlight vertically onto a daylighting system. This study proposes a 3 × 3 mirror matrix heliostat, which is different from the traditional heliostat with one single mirror. With the
heliostat, the system efficiency increases as high as 3.32 times. Chao-Wen Liang et al. propose a newly developed high overlapping density stitching interferometer, which is also proved to effectively reduce measurement uncertainty and improve measurement quality. Liang et al. discuss the use of high overlapping density subaperture stitching interferometry to reduce the impact of reference optics errors on the stitched phase. The tested optics surface deformation phase is determined by averaging the multiple subaperture measurements taken at different rotational angles. The simulation shows that the high overlapping density subaperture stitching interferometry can effectively reduce the stitched phase errors that are due to either the static or dynamic reference optics errors. Sivan Isaacs et al. propose a simplified analytic expression for the propagation matrix, which is derived for the case of nematic liquid crystal in the homogeneous geometry for LC Fabry–Perot tunable filters. The effects of dephasing originating from wedge or noncollimated light beams are investigated. Finally, more detailed experimental results of our polarization-independent configuration are given, which uses polarization diversity with a Wollaston prism. King Ung Hii et al. demonstrate a quadruple-pass lateral shearing interferometer by introducing a single mirror into the conventional double-pass system for collimation-based applications. The proposed system can be utilized for refraction-based and reflectionbased applications that depend on a test arm with a convergent beam. Mohammad Solaiman et al. discuss various dispersion compensation methods including design and evaluation, seeking a cost-effective technique with remarkable dispersion compensation percentage and pulse shape. The joint technique achieved the optimum dispersion compensation percentage among all evaluated techniques to reach 96.36%, remarkable pulse shape, and relatively lower cost compared with DCF but still more expensive than chirped Tanh FBG. Wenjiang Guo et al. propose and develop a new reference-free beam-sampling (RFBS) methodology and system for this particular application. It is shown that a ten of nanometers measurement accuracy is achieved, even for surfaces with a peak valley value of more than 1 mm. The feasibility and effectiveness of the RFBS methodology are proven. Chun-Liu Zhao et al. propose a reflective long-period grating-based sensor with a Sagnac fiber loop mirror (SFLM) for simultaneous measurement of refractive index (RI) and temperature. The application for 40 km long-distance RI and temperature measurement shows that the sensor has potential application in long-distance sensing. Shang-Ping Ying et al. propose the output power measurement of bare-wafer/chip light-emitting diodes (LED) using a large-area silicon (Si) photodiode with a simple structure and high accuracy relative to the conventional partial flux measurement using an integrating sphere. As a result, the large-area Si photodiode 10 October 2014 / Vol. 53, No. 29 / APPLIED OPTICS
ODT3
method practically reduces the output power measurement deviations of the bare-wafer/chip LED, so that high-accuracy measurement can be achieved in the mass production of the bare-wafer/chip LED without the complicated integrating sphere structure. Chuen-Lin Tien et al. propose a hybrid and flexible interference microscope combined with different phase algorithms to measure the surface roughness
ODT4
APPLIED OPTICS / Vol. 53, No. 29 / 10 October 2014
of thin films. The experimental results show that the proposed approach is feasible in determining the 3D deformation and surface roughness of thin films. HoLin Tsay et al. propose a newly developed fast measurement of a modulation transfer function (MTF) optical system inclusive of on- and off-axis measurement and then suggest there is nothing different for off- and on-axis measurement during microscanning.
