4f Imaging System Research Articles

Improved interferometric detection of scattered light with a 4f imaging system

We analyze the performance of three imaging systems to detect near-forward scattered light interferometrically by using a Mach-Zehnder geometry. The alignment of each system is demonstrated by measurement of the heterodyne efficiency and correlation of the angular width and field 1/e radius measurements of the sample beam. Measurements of angular-scattering data demonstrate the range of angles over which each system is effective. Of the three systems analyzed, the 4f imaging system is determined to be most effective, because it accurately reproduces both the phase and the amplitude of the scattered field at the detector.

Imaging phase objects with square-root, Foucault, and Hoffman real filters: a comparison.

Methods of imaging phase objects are considered. First the square-root filter is inferred from a definition of fractional-order derivatives given in terms of the integration of a fractional order called the Riemann-Liouville integral. Then we present a comparison of the performance of three frequency-domain real filters: square root, Foucault, and Hoffman. The phase-object imaging method is useful as a phase-shift measurement technique under the condition that the output image intensity is a known function of object phase. For the square-root filter it is the first derivative of the object phase function. The Foucault filter, in spite of its position, gives output image intensities expressed by Hilbert transforms. The output image intensity obtained with the Hoffman filter is not expressed by an analytical formula. The performance of the filters in a 4f imaging system with coherent illumination is simulated by use of VirtualLab 1.0 software.

Optomechanical design and characterization of a printed-circuit-board-based free-space optical interconnect package

We present a proof of concept and a feasibility demonstration of a practical packaging approach in which free-space optical interconnects (FSOI's) can be integrated simply on electronic multichip modules (MCM's) for intra-MCM-board interconnects. Our system-level packaging architecture is based on a modified folded 4f imaging system that has been implemented with only off-the-shelf optics, conventional electronic packaging, and passive-assembly techniques to yield a potentially low-cost and manufacturable packaging solution. The prototypical system as built supports 48 independent FSOI channels with 8 separate laser and detector chips, for which each chip consists of a one-dimensional array of 12 devices. All the chips are assembled on a single substrate that consists of a printed circuit board or a ceramic MCM. Optical link channel efficiencies of greater than 90% and interchannel cross talk of less than -20 dB at low frequency have been measured. The system is compact at only 10 in.3 (25.4 cm3) and is scalable, as it can easily accommodate additional chips as well as two-dimensional optoelectronic device arrays for increased interconnection density.

A Novel Free-Space Comega Network and Its Optical Implementation

A novel free-space multistage interconnection network has been proposed. The network can be implemented using a 1×2 binary phase grating (BPG) which is placed in a 4f imaging system. All optical channels from BPG have been used to form a Comega network. The optomechanical package of the Comega network was made.

Binarization of a super‐resolving graytone pupil filter by digital halftoning

Abstract— Six digital‐halftoning procedures, including one algorithm proposed by us, are compared to determine which one is best suited to binarization of a parabolic super‐resolving pupil filter. The procedures we deal with include iterative, error‐diffusion, error‐convergence, and 1‐pixel algorithms. We carry out a numerically simulated experiment in which an object that consists of either one point source or two coherent point sources is imaged in a 4f imaging system with either a continuous super‐resolving parabolic filter or one of its six different binary versions. The performance of binary filters is examined in terms of two parameters: the resemblance of their amplitude impulse response (AIR) to the AIR of the original continuous filter, as well as the two‐point Sparrow resolution criterion. We found that the best performance in terms of both figures of merit is achieved with the filter generated by means of one‐weight error diffusion when the weight is randomly positioned and the algorithm is processed on a serpentine raster.

Integrated optical imaging system

A planar version of a 4f imaging system is described where the input object and the lenses are integrated on one side of a single quartz glass substrate. The lenses were implemented as diffractive lenses with four discrete phase levels.