An innovative optics lab design for residency training in ophthalmology.

Proper understanding of the optical function of the eye is the foundation of clinical understanding of ophthalmologists. Although teaching principals of optics has always been a part of ophthalmology residency curriculum, it seems that successful strategies other than lecture-based methods are needed to engage students and facilitate the understanding of optical principals. A collaborative team of physicists (optics Ph.

Photon approach to diffraction, interference, optical coherence, and image formation.

When a parallel beam of light illuminates an aperture, the uncertainty principles require associating probability amplitude to a photon at each point of the aperture. Superposition of the amplitudes at the observation point behind the aperture, determines the probability that the photon strikes the point. In this paper, we show that this "photon approach" explains several optical concepts.

Optical diffractometry by rough phase steps.

Optical diffractometry (OD) using a phase step is an alternative for interferometry, further, has least sensitivity to environmental vibrations. Therefore, OD has found numerous interesting metrological and technological applications. OD utilizes a phase step to detect the influence of objects under measurement by the changes in the Fresnel diffraction pattern.

3D imaging using scanning diffractometry.

Imaging of cells is a challenging problem as they do not appreciably change the intensity of the illuminating light. Interferometry-based methods to do this task suffer from high sensitivity to environmental vibrations. We introduce scanning diffractometry as a simple non-contact and vibration-immune methodology for quantitative phase imaging.

Measuring source width and transverse coherence length using Fresnel diffraction from a phase step.

Measurement of the source size and specifying its effect on the spatial coherence of propagating light are important for characterizing distant sources such as stars, and imaging with partially coherent light. The common method for measuring spatial coherence is Young's two-pinhole experiment. For characterizing spatial coherence along a line, one needs to change the location of the pinholes over a large number of pairs of points.

Determination of the spectral line profile using a phase gradient step and stationary Fourier transform spectroscopy.

This paper introduces a new, to the best of our knowledge, simple, fast, and affordable spectroscopy technique, in which Fresnel diffraction caused by a phase gradient step is used to determine the spectral profile of light sources by Fourier transformation of the interferogram data. To realize the phase gradient step, a Fresnel biprism or double mirror can be used. In principle, a single interferogram is sufficient to obtain the line profile.

Moiré deflectometry-based position detection for optical tweezers.

Optical tweezers have proven to be indispensable tools for pico-Newton range force spectroscopy. A quadrant photodiode (QPD) positioned at the back focal plane of an optical tweezers' condenser is commonly used for locating the trapped object. In this Letter, for the first time, to the best of our knowledge, we introduce a moiré pattern-based detection method for optical tweezers.

Application of white light Fresnel diffractometry to film thickness measurement.

In this work we present the theoretical background and experimental procedure to measure the thickness of thin films by analyzing Fresnel diffraction patterns obtained from polychromatic illumination of phase-step samples. As examples of this technique, we measured the thicknesses of thin aluminum layers on glass substrates using three different broad-spectrum light sources. The results are in excellent agreement with independent interferometric measurements within less than 5% relative uncertainties.

Nanometer displacement measurement using Fresnel diffraction.

We introduce a relatively simple and efficient optical technique to measure nanoscale displacement based on visibility variations of the Fresnel diffraction fringes from a two-dimensional phase step. In this paper we use our technique to measure electromechanical expansions by a thin piezoelectric ceramic and also thermal changes in the diameter of a tungsten wire. Early results provide convincing evidence that sensitivity up to a few nanometers can be achieved, and our technique has the potential to be used as a nanodisplacement probe.

Tunable spectral shifts and spectral switches by controllable phase modulation.

In this work, we offer a novel and flexible approach of spectral switches which can be handled more simply by controlling the phase of the diffracted light field of a completely spatially coherent incident beam with spectral profile from a one-dimensional phase step. This scheme has the benefit of easy implementation by simply varying the height of a one-dimensional phase step which causes spectral switches to occur when the step height reaches certain critical values without modulating any properties of the light source. To illustrate this effect, an explicit and analytical expression at an observation point corresponding to the step edge is obtained and some numerical examples are given and examined experimentally.

Application of Fresnel diffraction from a phase step to the measurement of film thickness.

When a thin film that is prepared in a step form on a substrate and coated uniformly with a reflective material is illuminated by a parallel coherent beam of monochromatic light, the Fresnel diffraction fringes are formed on a screen perpendicular to the reflected beam. The visibility of the fringes depends on film thickness, angle of incidence, and light wavelength. Measuring visibility versus incident angle provides the film thickness with an accuracy of a few nanometers.

Spectral anomalies near phase singularities in reflection at Brewster's angle and colored castastrophes.

The anomalous behavior of a polychromatic beam reflected from the interface of two homogeneous dielectric media at the neighborhood of Brewster's angle is investigated theoretically and examined experimentally. An explicit expression is derived for the spectrum at an arbitrary observation point for a given incident spectrum. By introducing a modifier function it is shown that the spectrum at each point sensitively depends on the observation angle just in the immediate neighborhood of Brewster's angle and wavelength.