Axially distributed sensing with a monoscopic imaging lens for single-shot distance measurements.

Using the image-based optical measurement method known as axially distributed sensing (ADS), the depth information of a scene is retrieved by evaluating images recorded with a camera positioned on multiple points along a common optical axis. We describe the design of a monoscopic lens that images the scene from two different on-axis points of perspective simultaneously onto a single camera. Designed for use in a territorial surveillance video system, this lens allows for capturing 3D scene information based on ADS with a single shot.

Estimation of the phase error in interferometric measurements by evaluation of the speckle field intensity.

Intensities recorded with CCD or CMOS sensors represent spatially averaged values of the intensity across the area of a pixel. In this work we investigate the influence of spatial averaging in interferograms on the evaluated phase from an object wave with well resolved, fully developed speckles. Based on an analytical description of the averaging process, a procedure is developed to create a quality map for the evaluated phase, in order to give an estimation of the expected error at each point.

Determination of large-scale out-of-plane displacements in digital Fourier holography.

A novel approach for the determination of large-scale out-of-plane displacements from digital Fourier holograms is presented. The proposed method is invariant to lateral object shifts. It is based on the determination of the scaling of the reconstructed image that occurs when the recording distance is changed.

Improvement of accuracy in digital holography by use of multiple holograms.

Speckle pattern decorrelation reduces the accuracy of interferometric shape and deformation measurements. We introduce a technique for the reduction of speckle noise in digital holography. The method is not based on classical filtering techniques such as median filters.

Correlation between intensity and phase in monochromatic light.

Analytical expressions to describe the phase gradient of monochromatic light by means of the three-dimensional intensity distribution are derived. With these formulas it is shown that the two-dimensional phase gradient in a plane can be completely determined from noninterferometric intensity measurements if the light propagates strictly in one direction. The analytical expressions are verified by means of numerical investigations on simulated speckle fields, and the results are discussed with respect to common deterministic phase retrieval approaches.

Miniaturized digital holography sensor for distal three-dimensional endoscopy.

A miniaturized sensor head for endoscopic measurements based on digital holography is described. The system was developed to measure the shape and the three-dimensional deformation of objects located at places to which there is no access by common measurement systems. A miniaturized optical sensor, including a complete digital holographic interferometer with a CCD camera, is placed at the end of a flexible endoscope.