Fengtao Wang

45 Degree Polymer Micromirror Integration for Board-Level Three-Dimensional Optical Interconnects

We introduce here a simple method of integrating 45 degrees total internal reflection micro-mirrors with polymer optical waveguides by an improved tilted beam photolithography on printed circuit boards to provide surface normal light coupling between waveguides and optoelectronic devices for optical interconnects. De-ionized water is used to couple ultraviolet beam through the waveguide core polymer layer at 45 degrees angle during the photo exposure process. This technique is compatible with PCB manufacturing facility and suitable to large panel board-level manufacturing. The mirror slope is controlled accurately (within +/- 1 degrees) with high repeatability. The insertion loss of an uncoated micro-mirror is measured to be 1.6 dB.

Single sensor that outputs narrowband multispectral images.

We report the work of developing a hand-held (or miniaturized), low-cost, stand-alone, real-time-operation, narrow bandwidth multispectral imaging device for the detection of early stage pressure ulcers.

Precision measurements for propagation properties of high-definition polymer waveguides by imaging of scattered light

We present a reliable, nondestructive, and real-time technique for characterization of propagation properties of planar optical waveguides based on accurately imaging the scattered light from the optical waveguide using a sensitive charge-coupled device (CCD) camera with built-in integration functionality. This technique can be used for real-time investigation of the propagation properties (loss, mode profile, bending properties, etc.) as well as the fabrication quality of planar optical waveguides. With this technique, we evaluate high-definition polymer optical waveguides on printed circuit board (PCB) substrates with a very low loss of 0.065 dB/cm at a wavelength of 850 nm, and measurement accuracy is less than 0.01 dB/cm. We expect this technique with the given CCD camera to be suitable for reliably measuring loss coefficients well below 0.1 dB/cm.

High-contrast subcutaneous vein detection and localization using multispectral imaging.

Abstract. Multispectral imaging has shown promise in subcutaneous vein detection and localization in human subjects. While many limitations of single-wavelength methods are addressed in multispectral vein detection methods, their performance is still limited by artifacts arising from background skin reflectance and optimality of postprocessing algorithms. We propose a background removal technique that enhances the contrast and performance of multispectral vein detection. We use images acquired at visible wavelengths as reference for removing skin reflectance background from subcutaneous structures in near-infrared images. Results are validated by experiments on human subjects.

Real-Time Multispectral Imager for Home-Based Health Care

Multispectral imaging (MSI) is becoming a powerful tool for tissue abnormality detection. Conventional MSI systems, however, are not readily suitable for challenges of routine clinical uses due to the fact that they are expensive, bulky, and time consuming to acquire the data. In this letter we report a novel approach to instrument MSI technology into a handheld, low-cost, standing-alone, real-time operational device that is suitable for home-based health care. It covers techniques used to produce multiple images at discrete signature wavelengths of tissues with a single shot.

Developing handheld real time multispectral imager to clinically detect erythema in darkly pigmented skin

Pressure ulcers have been identified as a public health concern by the US government through the Healthy People 2010 initiative and the National Quality Forum (NQF). Currently, no tools are available to assist clinicians in erythema, i.e. the early stage pressure ulcer detection. The results from our previous research (supported by NIH grant) indicate that erythema in different skin tones can be identified using a set of wavelengths 540, 577, 650 and 970nm. This paper will report our recent work which is developing a handheld, point-of-care, clinicallyviable and affordable, real time multispectral imager to detect erythema in persons with darkly pigmented skin. Instead of using traditional filters, e.g. filter wheels, generalized Lyot filter, electrical tunable filter or the methods of dispersing light, e.g. optic-acoustic crystal, a novel custom filter mosaic has been successfully designed and fabricated using lithography and vacuum multi layer film technologies. The filter has been integrated with CMOS and CCD sensors. The filter incorporates four or more different wavelengths within the visual to nearinfrared range each having a narrow bandwidth of 30nm or less. Single wavelength area is chosen as 20.8μx 20.8μ. The filter can be deposited on regular optical glass as substrate or directly on a CMOS and CCD imaging sensor. This design permits a multi-spectral image to be acquired in a single exposure, thereby providing overwhelming convenience in multi spectral imaging acquisition.

Instrument an Off-Shelf CCD Imaging Sensor Into a Handheld Multispectral Video Camera

In this letter, we report the feasibility study of converting an ordinary off-shelf charge-coupled device (CCD) imaging sensor into a multispectral imaging instrument, using the multispectral bruises detection as an example. The resulting handheld device is capable of producing in real-time multiple pixel-registered images centered at different wavelengths in a single exposure, thereby providing overwhelming operational convenience. The results are advantageous for the development of a handheld narrowband multispectral imaging video camera for image guided medical surgery.

Capped optical polymeric waveguide

We present here a new type of polymer waveguides (i.e., capped waveguide) fabricated using contact photolithography with considerable performance improvement over the conventional waveguides. We also show that by simultaneous patterning of the core and the top cladding in capped waveguides, we can considerably reduce the effect of fabrication defects and reduce the propagation loss by at least 20% compared to conventional waveguides.

45 Degree polymer micro-mirror integration for board-level three-dimensional optical interconnects

We introduced here a novel method to fabricate polymer optical waveguides with integrated 45° total internal reflection (TIR) micro-mirrors by contact photolithography on printed circuit boards (PCBs) to achieve fully embedded optical interconnects. The 45° TIR mirrors were shaped at the ends of the waveguides in one step to provide surface normal light coupling between waveguides and optoelectronic devices. A tank of de-ionized (D.I.) water is used to couple the ultraviolet (UV) exposure beam through the core polymer layer at 45° angle during the contact photolithography process, and then the 45 mirror facet will be formed after the post-process. Compared to the conventional glass prism-polymer coupling interface, this novel water-polymer interface provides a simple, convenient, and cost efficient solution. This technique is not only compatible with PCB manufacturing facility and technology, but also suitable to large panel board-level manufacturing for optical interconnects. The 45° angle can be controlled with an accuracy of ±1° and has a high reproducibility. The average insertion loss of the 45° TIR uncoated mirrors is around 1.6dB.

Detecting early stage pressure ulcer on dark skin using multispectral imager

We are developing a handheld multispectral imaging device to non-invasively inspect stage I pressure ulcers in dark pigmented skins without the need of touching the patients skin. This paper reports some preliminary test results of using a proof-of-concept prototype. It also talks about the innovations impact to traditional multispectral imaging technologies and the fields that will potentially benefit from it.