Rose-Hulman Institute of Technology has 35 years of graduating optical scientists and engineers. The change from the Applied Optics degree program to the Optical Engineering degree program occurred in 2003, which paved the way for ABET accreditation. The past and present program reinforces the idea that we are educating our students in optics applications to deal with real-world problems and practice the profession of optical engineers. The RHIT program has been at the forefront of developing project-based learning since its inception in 1983. Since the name changed, the optical engineering program (OE) has completed three cycles of ABET accreditation. We are continuously improving our OE curriculum to meet the current and future needs of the industry and cutting-edge research. To lead the ABET review, Rose-Hulman initiated the dialogue with SPIE to be the lead society for optical engineering in 2004. This paper will discuss several steps taken to develop a world-class OE program with state-of-the-art laboratory facilities for undergraduate optical engineering education.
The Department of Physics and Optical Engineering at Rose-Hulman Institute of Technology has served as an educational outreach partner with the National Science Foundation sponsored engineering research center, Lighting Enabled Systems & Applications (formally Smart Lighting) for the past eight years. As part of the center, we developed educational materials on smart lighting, developed and taught lighting courses and workshops for both high school teachers and college students, and produced several short educational videos with students on lighting and general optical engineering topics. In this paper we will give examples of research and technical projects that were completed with students, discuss instructional materials that were developed, and describe the content of lighting and optics related educational videos.
Precise measurement of extremely small tilt angles is of immense importance in various scientific and technological applications. Interferometry has always been a tool of great importance in such applications. Most of the conventional interferometric techniques use a Michelson configuration and the problem with this interferometer is that it is extremely sensitive to environmental turbulances and vibrations. In our privious works, we had introduced a cyclic interferometer for the measurement of tilt angles which showed excellent stability against environmental turbulances and vibrations as well as twice the sensitivity. Also, with the introduction of multiple reflections, sensitivity as low as 5 micro radian had been achieved by us. To improve the sensitivity further, we had employed phase shifting techniques. The cyclic configuration being a same path interferometer, we used a polarizing phase shifting technique. For acieving this, we developed a new scheme of polarizing phase shifting techique which is rather simpler compared to those reported in the literature. With this we could precisely measure angles as low as 2 nano radians. However, in these measurements we found that the precise alignment of the quarter wave plate plays an important role in the visibility of the fringes which affects the accuracy of measurement. In this work, we numerically investigate the effect of the misalignment of the quarter wave plate on the visibility of the fringes and consequently on the accurcy of the measurement.
Accurate measurement of angles is extremely important in various metrological applications. Interferometry has always
been an excellent technique for accurate measurements. Several methods have been proposed for accurate tilt measurement
using interferometric techniques. Almost all of them use the Michelson configuration which is extremely sensitive to
environmental vibrations and turbulences. We know that a cyclic interferometer is extremely stable. Even though it is not
sensitive to displacement changes, it is twice sensitive to tilt compared to that of a Michelson interferometer. We have
enhanced the sensitivity to measure tilt using multiple reflections in a cyclic interferometer. Since the input beam is
collimated, we have studied the effect of aberration of the input beam on the accuracy of tilt measurement. Experimental
results on this study are presented in this paper.
Michelson interferometer is one of the most popular optical interferometric systems used in optical metrology. Typically, Michelson interferometers are used to measure object displacement with wavefront shapes to one half of the laser wavelength. As testing components and device sizes reduce to micro and nano size, a sensitivity of half the wavelength of light cannot be used to measure several hundred picometer displacement. Multiple-reflection interferometers have been proposed and are used to increase the sensitivity in a Michelson interferometer; however, when altering the number of reflections, the system alignment becomes cumbersome. We describe some of the problems associated with the current multiple-reflection interferometer and introduce a setup for matching path lengths to increase the resolution and allow for the reduction of the stringent requirement on the coherence length of the lasers used. Theoretically, we show that more than 1000 reflections can be achieved. Experimental results of up to 100 reflections are presented in this paper.
The Accreditation Board for Engineering and Technology (ABET) recently revised their published list of programspecific criteria. Beginning during the 2014-15 cycle, all engineering programs which include “optical” and “photonic” in their titles must meet new specific criteria to receive ABET accreditation. One portion of the wording under the curriculum section states “The curriculum must prepare students to have knowledge of and appropriate laboratory experience in: geometrical optics, physical optics, optical materials, and optical and/or photonic devices and systems.” Last year, the Rose-Hulman optical engineering curriculum committee revised our baccalaureate degree program. A portion of this effort sought to improve alignment to the ABET program-specific criteria. Here we review the outcomes of this effort, including our documented continuous improvement process, the realignment of our existing courses along the four tracks laid out by ABET, and the introduction of new undergraduate courses to improve student learning.
Lateral shear interferometry operating in the convergent beam mode has been used for testing optical components. This method is simple and phase information of the wavefront has conventionally been extracted using phase stepping techniques. We propose to use defocus, which introduces uniform tilt as a means of extracting phase information via two procedures, namely spatial phase stepping and spatial frequency carrier method. Experimental results are presented that show the wavefront phase extracted with defocus before and after the focal point of the lens.
Previously, we reported a simple method to obtain lateral shear in both the x - and y -directions using a multiplexing technique. The phase data was extracted using the inherent spatial carrier fringes formed due to the tilt in the two sheared beams. In this article, we report that an error in phase map is introduced when the band-pass-filtered Fourier transform (FT) spectrum is not centered prior to performing the inverse FT to obtain the phase. We also found that intentionally introducing aberrations when capturing dynamic fluctuations in the wave front, resulted in controlling the spread of the Fourier spectrum.
Testing with lateral and radial shears is becoming standard in optical shops. Of late, holographic optical elements have proven to be easy and simple to set up, and can be used in both a collimated and convergent beam. However, there is very little work on making quantitative measurements using a symmetric radial shear. We demonstrate a simple method of obtaining both asymmetric and symmetric radial shears, and use the inherent tilt in the wavefronts to perform spatial Fourier transformation to extract phase maps. This radial shear interferometer is also suitable for static and dynamic situations.
Over the past several years there has been a rapid advancement in solid state lighting applications brought on by the
development of high efficiency light emitting diodes. Development of lighting devices, systems and products that meet
the demands of the future lighting marketplace requires workers from many disciplines including engineers, scientists,
designers and architects. The National Science Foundation has recognized this fact and established the Smart Lighting
Engineering Research Center that promotes research leading to smart lighting systems, partners with industry to enhance
innovation and educates a diverse, world-class workforce. The lead institution is Rensselaer Polytechnic Institute with
core partners Boston University and The University of New Mexico. Outreach partners include Howard University,
Morgan State University, and Rose-Hulman Institute of Technology. Because of the multidisciplinary nature of
advanced smart lighting systems workers often have little or no formal education in basic optics, lighting and
illumination. This paper describes the initial stages of the development of self-contained and universally applicable
educational modules that target essential optics topics needed for lighting applications. The modules are intended to be
easily incorporated into new and existing courses by a variety of educators and/or to be used in a series of stand-alone,
asynchronous training exercises by new graduate students. The ultimate goal of this effort is to produce resources such
as video lectures, video presentations of students-teaching-students, classroom activities, assessment tools, student
research projects and laboratories integrated into learning modules. Sample modules and resources will be highlighted.
Other outreach activities such as plans for coursework, undergraduate research, design projects, and high school
enrichment programs will be discussed.
Testing with a single holographic lens or grating in a collimated beam is normally not possible because of the inherent tilt caused in the wavefront. The tilt between the two beams in shearing creates a large number of linear fringes which overshadow the information about the wavefront. However, here, we show that we can use this tilt to make quantitative measurements which was otherwise not possible. In the novel method, we obtain shear in a relatively simple way, and at the same time we extract phase information using spatial Fourier transform technique. This technique is suitable for making quantitative measurement of wavefront and disturbances in turbulent conditions. Here, we demonstrated the real-time phase measurement capacity of the interferometer, a result of one such application is shown.
A new mechanism is proposed for selective laser killing of abnormal cells by laser thermal explosion of single
nanoparticles - "nano-bombs" - delivered to the cells. Thermal explosion of the nanoparticles is realized when the heat
generates within the strongly-absorbing target more rapidly than the heat can diffuse away. On the basis of simple
energy balance, it is shown that the lower level of the threshold energy density of a single laser pulse required for
thermal explosion of solid gold nanospehere is about 40 mJ/cm2, which is well below the safety standard for medical
lasers (100 mJ/cm2) for healthy tissue and cells. The nanoparticle's explosion energy density can be reduced further (up
to 11 mJ/cm2) by using gold nanorods due to higher plasmon-resonance absorption efficiency of nanorods. Additionally,
the nanorods optical resonance lies in the near-IR region, where biological tissue transmissivity is the highest. Here, the
effective therapeutic effect for cancer cell killing can be achieved due to nonlinear phenomena, which accompany the
thermal explosion of the nanoparticles: generation of the strong shock wave with supersonic expansion of dense vapor in
the cell volume, producing sound waves and optical plasma.
The Physics and Optical Engineering department at Rose-Hulman Institute of Technology offers three degrees at the undergraduate level; physics, optical engineering, and engineering physics. The department recently transitioned a science-based applied optics degree into a B.S (Optical Engineering) degree. With this transition we began the process of seeking accreditation for the optical engineering program through the Accreditation Board of Engineering and Technology (ABET). This paper describes several assessment components of the accreditation process which includes a detailed curriculum mapping exercise to meet engineering standards. We discuss the overall outcome based optical engineering education.
Education in optics has evolved in the last decade into an application and enabling technology field and it is emerging as an engineering field in the last couple of years. Therefore, as a newly evolving program, the emphasis is placed on the overall learning outcomes of the students. In that regard we have developed concept inventory questions in optical engineering to monitor and assess improvements in student learning. The concept inventory questions are given to students twice during a course, one at first day of class and the same questionnaire is given to them during the last day of class. The pre-class test is used to assess prior knowledge of the students and the second test is used to measure the learning experience of the students. The results of the test are used to monitor and improve overall education experience of the students.
Rose-Hulman has a history of meeting the need for optical engineers via the Applied Optics Programs since 1983. We have changed our degree program to Optical Engineering and will seek ABET accreditation. The present paper will deal with the step taken to accomplish this and define the mission of the degree program.
The optics educational programs at Rose-Hulman Institute of Technology have progressed and evolved over the past twenty years. Beginning with a modest undergraduate area minor in applied optics we now offer bachelors and masters degree programs in optical engineering. Distinctive elements of the current optical engineering programs including courses and curricula will be discussed.
Multiple wavelength interferometry is used to increase the range of unambiguity beyond that of single wavelength interferometry. In wavelength scanning interferometry, the frequency of the intensity modulation induced by the wavelength change is determined independently for each image pixel. The tuning range determines the resolution of measurements, while the tuning step limits the range of the measurements. Laser diodes can be tuned, but an external cavity is needed for a larger mode hop free wavelength variation. Polished and optically rough surfaces can be analyzed in the same manner. Acquisition times of a few seconds and high resolutions were obtained. In a new development, the application of temporal evaluation of speckles for deformation and shape measurement will be discussed. It turns out that spectral and temporal phase analysis can be very useful for many applications in optical metrology.
Interferometry using a single wavelength delivers the surface topography and surface heights of optically polished surfaces. However, discrete steps and holes cannot be determined, the sensitivity is fixed, and the analysis of optically rough surfaces is not possible. Some of these limitations can be overcome by using two or more wavelengths. In wavelength scanning interferometry, the frequency of the modulation induced by the wavelength change is determined independently for each image pixel. The tuning range determines the resolution of measurements, while the tuning step limits the range of the measurements. Laser diodes can be tuned, but an external cavity is needed for a larger mode hop free wavelength variation. Polished and optically rough surfaces can be analyzed in the same manner. In a new development, the application of temporal evaluation of speckles for deformation and shape measurement will be discussed. It turns out that spectral and temporal phase analysis can be very useful for many applications in optical metrology. Experimental results will support the methods discussed.
Absolute interferometry can be a powerful tool for distance and shape measurement. Two and more wavelengths can be used to increase the range of unambiguity in interferometry. Furthermore it leads to the possibility to apply interferometric methods to measure optical rough surfaces. A continuously tunable laser in a two beam unequal path interferometer is used to overcome the ambiguity problem of classical interferometric methods. While the laser wavelength is tuned continuously, the variation of the interference intensity is recorded sequentially. At each image pixel the frequency of the signal modulation is analyzed, giving the absolute depth information for the corresponding object point. The wavelength tuning step governs the depth of measurement whereas the tuning range determines the depth resolution to be obtained. The method can be applied for optical as well as for technical surfaces. In the latter case, the intensity variation is observed independently in each speckle. However, the resolution of the measurement of optically rough surfaces is limited by the surface roughness. The continuous tuning of the wavelengths is performed with a diode laser with external cavity where a frequency variation of 30 nm can be obtained without mode hops within one second. Furthermore a novel method to measure the shape and steps heights by rotating the object and using temporal evaluation of the speckles' modulation is presented. Currently a temporal Fourier- transformation is used, similar to the evaluation method used in wavelength scanning interferometry.
In this paper we discuss the implementation of a project oriented laboratory course in optics education. Through our discussion we show the relevance and necessity for such a course. The course is tailored not only to make the students to learn concepts, but to build a product from scratch to completion. Emphasis is also made on the design, performance, marketing and aesthetics of the product.
In this paper we propose a new method of shearing in an electronic speckle pattern shearing interferometry using holographic gratings. The system we are proposing consists of two parts: 1) to image the object onto an intermediate ground glass, and 2) the image on the ground glass is in turn imaged onto the photosensor of a CCD camera. A holographic grating placed in front of the ground glass screen is used for shearing the two images and for introducing phase stepping.
In this paper further discussions on some new methods proposed in an earlier paper on phase stepping interferometry is detailed. These studies reveal that certain algorithms are more sensitive to miscalibration and nonlinearity and can be better candidates to detect the presence of phase shifter miscalibration or nonlinearity. A simplified approach to the understanding of the error and its reduction/elimination in phase shifting interferometry are also presented.
Techniques for measuring time-varying biospeckle of botanical specimens are investigated. Experimental evidence on the probability density function is presented. Several applicable techniques, such as power spectral density and correlation, are used for measuring and analyzing the temporal speckle intensity variations. These techniques are shown to exhibit information about the shelf life and aging of some botanical specimens used in our study. We also present a new phenomena related to the spatial properties of time-varying speckles. Theoretical and experimental results on the size of a speckle in a speckle pattern and its relation to the temporal intensity variation are also detailed.
Described in this paper is a compact phase measuring ESPI system that incorporates single mode fiber and diode laser. The single mode fiber along with diode laser provides ease of system arrangement but also causes wavelength fluctuation and instability. The wavelength instability was reduced to an acceptable level with an optical isolator. Experimental studies on wavelength stability of the diode laser, the back-reflection intensity from the fiber ends, and their influence on the system are presented.
The design and system performance of an infrared phase-stepping interferometer is reviewed. This instrument is capable of measuring rms surface roughness with a repeatability of 0.02 waves. The instrument uses a 4-bucket unwrapping algorithm. Calibration of the interferometer and removal of inherent system aberrations are discussed along with the system performance, including repeatability and accuracy. The interferometer is an all-reflective optics design to permit use at any wavelength, accommodating both far- (10.6 micron) and near- (5 micron) infrared sources. Testing applications include infrared windows and surface testing.
In this paper a comparison of different techniques to obtain vibration patterns by phase stepping on an electronic speckle pattern interferometer (ESPI) is made. The theoretical evaluation of the contrast of the fringes shows that the (pi) phase step method gives good contrast; however, the four step method gives the same contrast along with better pictorial representation. Speckle averaging on the other hand also increases the contrast of the fringes apart from smoothing of speckles. Experimental results corroborating the theoretical predictions are also presented.
A phase-measuring fiber optic electronic speckle pattern interferometer (ESPI) was recently constructed and demonstrated. In this arrangement, phase stepping is introduced by stretching the fiber wrapped around a piezoelectric transducer. Calibration of the phase step is critical in phase measurement techniques for obtaining good phase plots. Methods used for calibrating the stretcher are outlined and the drifts in the phase caused by fluctuations in temperature and mechanical stresses are discussed. Ways to minimize this drift are also presented.
In this paper we discuss a fiber optic electronic speckle pattern interferometer (ESPI) for obtaining 3D information about surface deformation. Phase stepping is introduced by stretching the fiber wrapped around a piezo-electric transducer. Two schemes to stretch the fiber are discussed. Also calibration of the phase step is critical in phase measurement techniques for obtaining good phase plots. In this paper we outline a method used for calibrating the stretcher. We also discuss the error in the phase caused by temperature changes.
In this paper we discuss a fiber optic phase measuring Electronic Speckle Pattern Interferometer. The phase stepping is obtained by stretching the reference arm fiber. We also outline briefly the theory of determining the phase by differentiating the interferogram. Preliminary results obtained with four bucket and differentiation algorithms are presented. 2.
Fiber optic Mach-Zehnder interferometric sensors for the measurement of various physical parameters such as pressure temperature and magnetic fields are well known and documented. This paper deals with the construction of a fiber optic sensor incorporating He-Ne and diode lasers. Preliminary experimental results for temperature sensing are reported.
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