Switchable electro-optic diffractive lens with high efficiency for ophthalmic applications.

Presbyopia is an age-related loss of accommodation of the human eye that manifests itself as inability to shift focus from distant to near objects. Assuming no refractive error, presbyopes have clear vision of distant objects; they require reading glasses for viewing near objects. Area-divided bifocal lenses are one example of a treatment for this problem. However, the field of view is limited in such eyeglasses, requiring the user to gaze down to accomplish near-vision tasks and in some cases causing dizziness and discomfort. Here, we report on previously undescribed switchable, flat, liquid-crystal diffractive lenses that can adaptively change their focusing power. The operation of these spectacle lenses is based on electrical control of the refractive index of a 5-mum-thick layer of nematic liquid crystal using a circular array of photolithographically defined transparent electrodes. It operates with high transmission, low voltage (<2 Vrms), fast response (<1 sec), diffraction efficiency > 90%, small aberrations, and a power-failure-safe configuration. These results represent significant advance in state-of-the-art liquid-crystal diffractive lenses for vision care and other applications. They have the potential of revolutionizing the field of presbyopia correction when combined with automatic adjustable focusing power.

Dynamic correction of a distorted image using a photorefractive polymeric composite.

We demonstrate, for the first time, the dynamic correction of aberrated images in real-time using a polymeric composite with fast response times. The current novel experimental design is capable of restoring a phase aberrated, image carrying laser beam, to nearly its original quality. The ability to reconstruct images in real-time is demonstrated through the changing of the aberrating medium at various speeds. In addition, this technique allows for the correction of images in motion, demonstrated through the oscillatory movement of the resolution target. We also have demonstrated that important parameters of the materials in the study such as response times, diffraction efficiencies and optical gains all retain high figures of merit values under the current experimental conditions.

Structure of the Teaching Analysis by Students (Tabs).

Recent trends in student-based evaluation of instruction indicate interest in diagnostic aspects of teacher behavior in the classroom. The Teaching Analysis By Students (TABS) was administered to 2096 students enrolled in 90 courses at the University of Hawaii. Thirty-nine (36 diagnostic, three criterion) ratings were factor analyzed, and seven factors were rotated with Varimax. The factors were labeled Accountability, Communication Facilitator, Dynamism/Flexibility, General Instructor Impact, Closure/Pacing, Openness, and Communication Skill. The factors divided into two broad categories: management of information and management of interpersonal relations. Stepwise multiple regression was employed to predict three criterion ratings: instructor impact (R # .72), course impact (R # .64), and cognitive and affective growth (R # .52). The findings supported the view that specific instructor behaviors are related to educational outcomes.

Structure of Student-Based Evaluation Ratings.

This study attempted to clarify the dimensionality of faculty-course evaluation. A special appraisal instrument consisting of 64 rating items was administered to 2301 men and women students at the University of Hawaii. Sixty-four variables were intercorrelated and factor analyzed, resulting in an eight factor solution. The factors were grouped around the concepts of learning context, instructor, course, and outcomes of instruction. The findings were discussed in light of a systems approach to evaluation in higher education.