Channel reduction and applications to image processing.

Oftentimes when one is dealing with digital color images it is desired that some sort of image processing be performed on the spatial information. Current methods require that one process each of the channels (also called planes or colors) of an image separately, which increases the number of computations significantly. A novel, to our knowledge, approach to reducing the number of channels in a color image is presented.

Passive ranging through wave-front coding: information and application.

Passive-ranging systems based on wave-front coding are introduced. These single-aperture hybrid optical-digital systems are analyzed by use of linear models and the Fisher information matrix. Two schemes for passive ranging by use of a single aperture and a single image are investigated: (i) estimating the range to an object and (ii) detecting objects over a set of ranges.

Control of chromatic focal shift through wave-front coding.

Control of chromatic aberration through purely optical means is well known. We present a novel, to our knowledge, optical-digital method of controlling chromatic aberration. The optical-digital system, which incorporates a cubic phase-modulation (CPM) plate in the optical system and postprocessing of the detected image, effectively reduces a system's sensitivity to misfocus in general or axial (longitudinal) chromatic aberration, in particular.

Realizations of focus invariance in optical-digital systems with wave-front coding.

We report experimental verification of an extended depth of focus (EDF) system with near-diffraction-limited performance capabilities. Dowski and Cathey [Appl. Opt.

Effect of detector noise in incoherent hybrid imaging systems.

Hybrid imaging systems involve the joint design of an optical image-gathering module and digital processing algorithms to obtain a required final image. They have the potential to achieve imaging performance hitherto unobtainable by conventional imaging techniques. A reduction in the signal-to-noise ratio of the final image is one of their main disadvantages when one is considering linear signal processing.

Phase plate to extend the depth of field of incoherent hybrid imaging systems.

A hybrid imaging system combines a modified optical imaging system and a digital postprocessing step. We describe a spatial-domain method for designing a pupil phase plate to extend the depth of field of an incoherent hybrid imaging system with a rectangular aperture. We use this method to obtain a pupil phase plate to extend the depth of field, which we refer to as a logarithmic phase plate.

Reducing complexity in computational imaging systems.

Traditional methods of optical design trade optical system complexity for image quality. High quality imagers often require high system complexity. A new imaging methodology called Wavefront Coding uses aspheric optics and signal processing in order to reduce system complexity and deliver high quality imagery.

New paradigm for imaging systems.

We describe a new paradigm for designing hybrid imaging systems. These imaging systems use optics with a special aspheric surface to code the image so that the point-spread function or the modulation transfer function has specified characteristics. Signal processing then decodes the detected image.

Extended depth of field with a nonlinear silver-halide emulsion detector.

Presented here are experimental results of an extended depth-of-field (EDF) system using film to record the image. The EDF system used is an application of wave-front coding. A phase mask is placed in the aperture stop of the lens to code the image data; then digital signal processing is used to decode the image.

Reduced depth of field in incoherent hybrid imaging systems.

A hybrid imaging system combines a modified optical imaging module and a digital postprocessing step. We define what to our knowledge is a new metric to quantify the blurring of a defocused image that is more suitable than the defocus parameter for describing defocused hybrid imaging systems. We use this metric to design a pupil phase grating to reduce the depth of field, thereby increasing the axial resolution, of an incoherent hybrid imaging system using quasi-monochromatic illumination.

Extended depth of field and aberration control for inexpensive digital microscope systems.

We present a new application and current results for extending depth of field using wave front coding. A cubic phase plate is used to code wave fronts in microscopy resulting in extended depths of field and inexpensive chromatic aberration control. A review of the theory behind cubic phase plate extended depth of field systems is given along with the challenges that are face when applying the theory to microscopy.

Defocus transfer function for circularly symmetric pupils.

We present a two-dimensional function that graphically illustrates the effects of defocus on the optical transfer function (OTF) associated with a circularly symmetric pupil function. We call it the defocus transfer function (DTF). The function is similar in application to the ambiguity function, which can be used to display the OTF associated with a defocused rectangularly separable pupil function.

Extended depth of field through wave-front coding.

We designed an optical-digital system that delivers near-diffraction-limited imaging performance with a large depth of field. This system is the standard incoherent optical system modified by a phase mask with digital processing of the resulting intermediate image. The phase mask alters or codes the received incoherent wave front in such a way that the point-spread function and the optical transfer function do not change appreciably as a function of misfocus.

Single-lens single-image incoherent passive-ranging systems.

We introduce a new system for single-lens single-image incoherent passive ranging. The only a priori object information this system requires is that the objects to be ranged must possess a low-pass spatial frequency spectrum. Physically, this system for passive ranging is a standard optical imaging system that is customized with a special-purpose optical mask or filter.

Practical speed limits of free-space global holographic interconnects: time skew, jitter and turn-on delay.

The speed limits imposed on free-space global interconnects are affected by factors that can be divided into three groups: geometric parameters of the optical system that determine the propagation time and time skew, emitter parameters (turn-on delay and timing jitter), and system requirements (fan-in in the detector and bit error rate). For 32 × 32 global interconnects, numerical estimations of light propagation time and timing skew are presented. Time delay and jitter in a diode laser are calculated.

Ferroelectric liquid-crystal-based binary optical memory employing feedback.

A two-dimensional bit-oriented refreshing optical memory that is loosely based on the design of an electronic flip-flop is presented. The test system consisted of two amorphous-silicon liquid-crystal optically addressed spatial light modulators placed into an inverting configuration to provide a stable refreshable memory element. A description of the optically addressed spatial light modulator device and its operation is presented.

Superresolving phase conjugate scanning microscope.

Analytical and experimental results of a new type of optical scanning microscope, which uses a phase conjugate mirror and pinholes to achieve superresolution, are presented. The phase conjugate scanning microscope has a higher Rayleigh resolution limit and better sectioning discrimination than conventional, single pass, and double pass scanning microscopes. It also can reduce the effect of static and dynamic aberrations on the imaging process, is very easy to align, and has the potential of introducing optical power gain into the system.

Optical database/knowledgebase machines.

In this paper we discuss various aspects of databases and knowledgebases and indicate how optics can play an important role in the solution of many of the previously unsolved problems in this field.

Polarization-based optical parallel logic gate utilizing ferroelectric liquid crystals.

We describe parallel optical XOR and XNOR logic gates implemented with ferroelectric liquid-crystal (FLC) electro-optic elements to yield naturally a logic in which the binary gate outputs are indicated by two orthogonal polarizations of transmitted light. These gates absorb no power from the incident light beam and hence can be cascaded without the need to regenerate NOT inputs. The FLC elements also confer the advantages of low-voltage, low-power, submicrosecond switching and intrinsic two-state memory.

Optical implementations of mathematical resolution.

Mathematical resolution is an algorithmic technique for reasoning from facts expressed in clause form to a conclusion. The technique is normally implemented on electronic computers with list-processing languages. This paper presents data representation and processing techniques for a parallel implementation using array-based optical logic.

Primary adrenocortical nodular dysplasia, a distinct subtype of Cushing's syndrome. Case report and review of the literature.

Non-iatrogenic Cushing's syndrome has been associated primarily with three entities: pituitary-dependent processes due to pituitary adenomas or microadenomas causing adrenal hyperplasia; pituitary-independent primary adrenal causes, predominantly unilateral adenomas, rarely multiple adenomas or adrenal carcinoma; ectopic sources of adrenocorticotropic hormone (ACTH) production. Although non-neoplastic bilateral adrenal disease generally has been ascribed to extra-adrenal stimulation, a rare cause of Cushing's syndrome that involves bilateral adrenal nodule formation independent of pituitary stimulation has been identified. Nodular adrenal diseases represent a confusion of terms in the literature, but one subgroup of Cushing's syndrome has most frequently--and, perhaps, most appropriately--been designated primary adrenocortical nodular dysplasia.

Chronic arthritis of rabbits induced by mycoplasmas. IV. Protective effect of immunization and prior infection.

Rabbits exposed to Mycoplasma arthritidis either by active immunization with killed mycoplasmas or by primary infection in the right knee were protected against intra-articular challenge with viable M. arthritidis in the left knee. This protection extended to the challenged knees of preinfected rabbits even while highly active inflammation persisted in the initially injected joints.

Rheumatoid vasculitis of the colon presenting as pancolitis.

This report describes a patient with pancolitis resulting from rheumatoid vasculitis. Corticosteroid treatment reduced colonic inflammation but colectomy was required to control hemorrhage. The case illustrates the need to recognize colitis as a manifestation of rheumatoid vasculitis so that new treatment modalities may be employed to achieve a more successful medical management.