This article presents results from a survey of ethical beliefs about practice dilemmas unique to clinical work with children and adolescents. Survey data suggest that identical practices are not always ethically equivalent, particularly when the developmental status of the client is varied. The survey also reveals widespread ambiguity about what constitutes ethical practice, as manifested both in individual uncertainty and in the absence of group consensus. Ethically guided clinical practice is presented as a far more complex undertaking than adherence to a single set of professional standards.

In a phase stepped speckle interferometer, phase steps can be realized temporally or spatially. The spatial approach has the advantage of simultaneous acquisition of all phase stepped interferograms which eliminates phase errors due to phase changes that can occur between phase steps when phase is stepped in time. For spatially phase stepped systems based on multiple optical channels, it is important that interferograms are well aligned to the others. Alignment can be achieved and maintained by a system that does not rely strongly on high mechanical stability but is based on measuring the alignment errors and correcting them. The alignment system presented in this work uses speckle correlation to quantify alignment errors with sub-pixel accuracy, and comprises a piezo-electric controlled mirror to achieve precise alignment.The alignment method has been implemented for a two-channel shearing speckle interferometer. It allows for precise initial alignment both for translation and rotation of the two phase stepped speckle patterns on the CCD. Translation adjustments to maintain sub-pixel alignment during operation can be realized very quickly, preceding a test session. The importance of adequate alignment, and the effects of insufficient alignment, are illustrated by experimental results.

No abstract

It is generally acknowledged that it takes at least three phase-stepped speckle patterns to obtain quantitative phase information. However, if only a phase change has to be determined, a two-bucket approach can be followed, under certain conditions. The background of the two-bucket algorithm, and the requirements with respect to the use of it, are explained. Examples of modeled and measured phase stepped speckle intensity data, showing numerical instability when conditions are not met are presented. It is also shown that two phase-stepped speckle pattern pairs, taken before and after an event can be sufficient to determine phase changes invoked by the event.

A polarization-based shearing speckle interferometer requires the incoming scattered light to have proper polarization characteristics: the light should be equally distributed over two orthogonal polarization states in order to obtain two interfering beams with equal intensities and the highest possible modulation. Many surfaces scatter linearly polarized light randomly, providing equal intensities for the interfering beams on average. However, when a diffusely reflecting metallic surface is illuminated by a linearly polarized laser beam, the polarization direction of the illuminating beam is retained to a large extent in the scattered light. As a result light entering the interferometer will not be randomly polarized, which may lead to low modulation due to unbalanced object and reference beams. A solution that handles the problem effectively is proposed. It consists of a quarter-wave plate positioned in front of the interferometer, oriented at 45 • . It is shown that unfavourable predominant polarization states encountered when testing unprepared metallic surfaces can be converted into favourable ones, thereby obtaining well balanced object and reference beams, irrespective of the polarization direction of the incoming light.

No abstract

A polarization phase stepping method is presented based on the use of a polarization plane rotator that establishes a relative phase shift between two counter-rotating circularly polarized beams. The phase step can be made relatively accurate, since it just depends on the accuracy with which the rotator is manufactured, and not on its orientation. The phase stepping method has been implemented in a single-camera two-channel shearing speckle interferometer, with two optical channels, and a relative phase step of π/2 between them.

Phase stepping algorithms are mostly based on three or more interferograms that can either be acquired sequentially, involving some temporal phase stepping mechanism, or in parallel. When a phase step is applied between acquisitions, object phase changes may cause phase errors when calculating phase. A new system that allows the object to change in between arbitrary temporal phase steps is proposed. It comprises a relatively simple polarization based two-channel speckle interferometer that acquires two π/2 phase stepped interferograms simultaneously with a single camera. This quadrature pair is phase stepped with a temporal phase stepping system that is also polarization based. Simulations and experimental results are presented that illustrate the improvements achieved with quadrature phase stepping compared to results obtained with the two-channel speckle interferometer operated without additional temporal phase stepping.